^^^njBR?^^ 


This  book  is  due  on  the  date  indicated 
below  and  is  subject  to  an  overdue 
fine  as  posted  at  the  circulation  desk. 


EXCEPTION:  Date  due  will  __ 
earlier  if  this  item  is  RECALLED. 


1  be  I 
.ED.  I 


THE 

COMPARATIVE    ANATOMY 

OF  THE 

DOMESTICATED    ANIMALS 


THE 

COMPARATIVE    ANATOMY 

OF  THE 

DOMESTICATED    ANIMALS 


BY 

A.   CHAUVEAU,  M.D.,  LL.D. 

MEMBER   OF   THE   INSTITUTE   (ACADEMY   OF   SCIENCES);   INSPECTOR-GENERAL  OF  VETERINARY 
SCHOOLS   IN   FRANCE;   PROFESSOR   AT   THE   MUSEUM   OF   NATURAL   HISTORY,   PARIS 

JElctiiseli  antJ  IBnlargeti,  toftl)  ti)e  ©o^opcratfon  ot 
S.  ARLOING 

DIRECTOR  OF  THE   LYONS   VETERINARY   SCHOOL 
PROFESSOR  OF  EXPERIMENTAL  AND   COMPARATIVE  MEDICINE  AT   THE   LYONS   FACULTY   OF  MEDICINE 


SECOND    ENGLISH    EDITION 

TRANSLATED    AND    EDITED 

By  GEORGE  FLEMING,  C.B.,  LL.D.,  F.R.C.V.S. 

LATE  PRINCIPAL  VETERINARY  SURGEON   OF  THE  BRITISH  ARMY  ;   FOREIGN  CORRESPONDING  MEMBER 

or  THE  SOClETfe   ROYALE  DE   MfeDKCINE,  AND   OF  THE   SOClfiTfi   ROYALE   DE   mSdECINE  PUBLIQUE,  OF  BELGIUM 

FOREIGN  ASSOCIATE   OF  THE  SOClllTfi  CENTRALE   DE   MfeOECINE  VfiT^RINAIRE   OP  FRANCE 

HONORARY   LIFE   MEMBER  OF  THE  ROYAL  AGRICULTURAL  SOCIETY   OF  ENGLAND 

FOREIGN  MEMBER  OF  THE   SOClfiTfi  NATIONALE  D'AGRICULTURE  OF  FRANCE,   ETC 

EXAMINER  IN  ANATOMY   FOR  THE   ROYAL  COLLEGE   OF  VETERINARY  SURGEONS 


WITH  585  ILLUSTRATIONS 


NEW    YORK 

D.    APPLETON    AND    COMPANY 

1905 


IN  COMMEMORATION  OF  THE  CENTENARY 

OF   THE 

ROYAL    YETERINAEY    COLLEGE,    LONDON; 

THE    PARENT   OF   VETERINARY    SCHOOLS    IN    ENGLISH-SPEAKING   COUNTRIES. 

AND   IN   MEMORY   OF 
CHARLES  VIAL  DE   SAINT-BEL, 

EQUERRY   TO   LOUIS    XVI.    OF   FRANCE,    PRINCIPAIi   OF   THE    LYONS    ACADEMY, 

PROFESSOR   IN   THE    ROYAL   VETERINARY    SCHOOL  OF  THAT    CITY, 

AND 

DEMONSTRATOR  OF  COMPARATIVE  ANATOMY  AT  MONTPELLIER  ; 

WHO,    WHEN   A   REFUGEE    FROM    THE    GREAT    FRENCH    REVOLUTION,    WAS 

CHIEFLY   INSTRUMENTAL    IN    ESTABLISHING    THE    FIRST   ENGLISH    VETERINARY  SCHOOL, 

IN   WHICH    HE    WAS    THE    FIRST   TEACHER, 

1791. 


PEEFACE  TO   THE   SECOND   ENGLISH   EDITION. 

Since  the  translation  of  this  work  into  English,  seventeen  years  ago,  it 
has  been  several  times  reprinted,  the  last  occasion  being  in  1889.  Cir- 
cumstances had,  however,  for  some  time  indicated  that  there  was  need 
for  a  revision  of  the  work  in  order  to  bring  it  up  to  the  requirements 
of  the  present  day,  and  the  issue  of  a  fourth  French  edition  last  year  was 
considered  a  favourable  opportunity  for  undertaking  the  task. 

In  preparing  this  second  edition,  the  necessities  of  advancing  veteri- 
nary education  in  the  English-speaking  schools  was  kept  in  view,  and  this 
entailed  considerable  amendments,  alterations,  and  additions,  in  order 
to  adapt  it  more  perfectly  to  the  conditions  it  should  fulfil  as  a  text- 
book and  standard  work  of  reference  on  the  subject. 

The  high  esteem  in  which  the  first  edition  has  been  held  for  so  many 
years  in  this  country,  in  our  Colonies,  and  in  the  United  States  of  America, 
amply  testifies  to  the  value  of  the  work ;  and  in  this  new  edition  every- 
thing has  been  done  to  render  it  still  more  comprehensive,  complete,  and 
useful.  The  anatomy  of  the  Ass,  Mule,  and  Eabbit  has  been  added,  as 
well  as  that  of  the  Camel — that  animal  being  utilized  not  only  in  our 
army  in  different  parts  of  the  world,  but  also  in  some  of  our  Colonies. 
The  number  of  illustrations  has  been  increased  by  more  than  one  hundred 
and  thirty,  the  pages  have  been  enlarged,  and  the  letterpress  so  modified 
as  to  make  reading  and  reference  much  easier. 

A  copious  index — there  is  none  in  the  French  edition — has  also  been 
added,  with  the  view  of  enhancing  the  usefulness  of  the  book  as  a  work 
of  reference  for  students  and  practitioners. 

With  these  alterations,  additions,  and  modifications,  I  trust  the  work 
may  continue  to  be  accepted  as  in  every  way  worthy  of  the  position 
accorded  to  it  as  the  best  on  the  subject. 

The  editorial  remarks — for  which,  as  well  as  for  the  translation,  I 
assume  the  entire  responsibility — are  included  in  brackets,  as  in  the  first 
edition. 

GEORGE  FLEMING. 
London, 

April,  1891. 


TABLE   OF   CONTENTS. 


Dedication 

Preface  to  the  Second  Edition 

Table  of  Contents 

Table  of  Illustrations 


Vll 

ix 

xxvii 


GENERAL  CONSIDERATIONS. 


Definition  and  Division  of  Anatomy       ....... 

Enumeration  and  Classification  of  the  Species  of  Domesticated  Animals 
General  Ideas  of  the  Organization  of  Animals,  and  the  order  followed  in  studying  the 
various  apparatuses  ........ 


BOOK  I. 

IiOCOMOTORY  APPARATUS. 

[RST  SECTION.— THE  BONES 

7 

Chapter  I.— The  Bones  in  General     .... 

7 

Article  I. — The  Skeleton     ...... 

8 

Article  II.— General  Principles  applicable  to  the  Study  of  all 

the  Bones        11 

Name,  Situation,  Direction,  and  Configuration  of  Bones 

12 

Internal  Conformation  of  Bones.     Structure  of  Bones 

15 

Development  of  Bones           ...... 

19 

Chapter  II.— The  Bones  of  Mammalia  in  Particular 

24 

Article  I.— Vertebral  Column        .            .                         .            . 

24 

Characters  Common  to  all  the  Vertebrae  .... 

24 

Characters  Proper  to  the  Vertebrae  in  each  Region     . 

26 

1.  Cervical  Vertebrae  ...... 

27 

Differential  Characters  ...... 

30 

2.  Dorsal  Vertebrae      ...... 

32 

Differential  Ciiaracters  ...                          ,             . 

35 

3.  Lumbar  Vertebrae   ...... 

36 

Differential  Characters  ...... 

37 

4.  Sacrum        ....... 

39 

Differential  Characters                .... 

40 

5.  Coccygeal  Vertebrae             ..... 

41 

Differential  Characters  ..... 

41 

The  Spine  in  General      ...... 

42 

Varieties  in  the  Vertebral  Column     .... 

43 

Comparison  of  the  Vertebral  Column  of  Man  with  that  of  the  1 

Domesticated 

Animals               ...... 

45 

Article  II.— The  Head  .            .            .            c            .            . 

46 

The  Bones  of  the  Cranium    ..... 

46 

1.  Occipital      ....... 

46 

Differential  Characters  ..... 

48 

2.  Parietal       ....... 

49 

Differential  Characters  ..... 

49 

3.  Frontal 

49 

Differential  Characters  ..... 

52 

TABLE  OF  CONTENTS. 


4.  Ethmoid      . 
DiflTerentiiil  Characters 

5.  Sphenoid     . 

Diflferentiiil  Characters 

6.  Temporal     . 
DiflFerential  Characters 

The  Bones  of  the  B'ace    . 

1.  Supermaxillii     . 
Diflferential  Characters 

2.  Premaxilla 
DiflFerential  Characters 

3.  Palatine 
Differential  Characters 

4.  Pterygoid 
Differential  Characters 

5.  Malar    . 
Differential  Characters 

6.  Lachrymal 
Differential  Characters 

7.  Nasal    . 
Differential  Characters 

8.  Turbinated 
Differential  Characters 

9.  Vomer  . 
Differential  Charaeters 

10.  Inferior  Maxilla 
Differential  Characters 

11.  Hyoid 
Differential  Characters 

12.  Wormian  Bunes 
Of  the  Head  in  General  . 

1.  General  Configuration 

2.  Conformation  of  the  Cranium  in  Particular 

3.  Relations  between  the  Cranium  and  Face  . 

4.  Modifications  due  to  Age     . 
Comparison  of  the  Head  of  Man  with  that  of  Animals 

Article  III. — The  Tuobax 

The  Bones  of  the  Thorax  in  Particular 

Differential  Characters 
Ribs  ...... 

Differential  Characters  in  the  Ribs  of  other  Animals 
The  Thorax  in  General  .... 

Comparison  of  the  Thorax  of  Man  with  that  of  other  Animals 

1.  Sternum 

2.  Ribs 
Article  IV.— Anterior  Limbs 

Shoulder 

Scapula      . 

Differential  Characters 
Arm 

Humerus 

Differential  Ciiaracters 
Forearm 

1.  Radius 

2.  Ulna 
Differential  Characters 

Anterior  (or  Fore)  Foot,  or  Hand 

1.  Carpal  Bones     . 
Differential  Characters 

2.  Metacarpal  Bones 
Differential  Characters 


TABLE  OF  CONTENTS. 


that  of  the   Domesticated 


AND   THEIR   PARALLELISM 


8.  Bones  of  the  Phalanges  or  Digital  Region  .... 

Differential  Characters  ...... 

Comparison  of  tJje  Thoracic  Limb  of  Man  with  that  of  the  Domesticated  Animal 
Article  V. — The  Hand  in  General        ..... 

Article  VI. — Posterior  or  Pelvic  Limb 
Pelvis     .... 

A.  Coxa,  or  Os  Innomatura 

B.  The  Pelvis  in  General 
Differential  Characters 

Thigh     .... 

Femur        .... 

Differential  Characters 
Leg  ..... 

1.  Tibia 

2    Fibula,  or  Peroneus       .  . 

3.  Patella 

Differential  Characters 
Posterior  Foot      . 

1.  Bones  of  the  Tarsus 
Differential  Characters 

2.  Bones  of  the  Metatarsus 
Differential  Characters 

3.  Bones  of  the  Digital  Region 
Differential  Characters 

Comparison  of  the  Abdominal  Limb  of  Man  with 
Animals. 
Article  VII. — The  Foot  in  General 
Article  VIII. — The  Limbs  in  General, 
Chapter  III.— The  Bones  in  Birds 
Chapter  IV.— Theory  of  the  Vertebral  Constitution  of  the  Skeleton 
SECOND   SECTION —THE   ARTICULATIONS  .... 

Chapter  I.— The  Articulations  in  General  .... 

General  Characters  of  the  Diarthroses  ..... 

General  Characters  of  the  Synarthroses  ..... 

General  Characters  of  the  Amphiarthroses,  or  Symphyses      . 
Chapter  II. — The  Articulations  in  Mammalia  in  Particular     . 
Article  I. — Articulations  op  the  Spine     ..... 

Intervertebral  Articulations         ...... 

Differential  Characters       ....... 

Article  II.— Articulations  of  the  Head 

1.  Atlo-axoid  Articulation  .  .  .  .  .  . 

2.  Occipito-atloid  Articulation  ..... 

3.  Articulations  between  the  Bones  of  tlie  Head    .... 

4.  Temporo-maxillary  Articulation      ..... 

5.  Hyoideal  Articulations  ....... 

Article  III. — Articulations  of  the  Thorax     .... 

Extrinsic  Articulations  ....... 

Costo-vertebral,  or  Articulations  of  the  Ribs  with  the  Vertebral  Column 
Intrinsic  Articulations  ....... 

A.  Chondro-sternal  or  Costo-sternal  Articulations 

B.  Chondro-cdsta!  Articulations,  or  Articulations  between  the  Ribs  and  their 

Cartilages        ...  .... 

C.  Articulations  between  the  Costal  Cartilages 

D.  Sternal  Articulation  peculiar  to  the  Ox  and  Pig 

The  Articulations  of  the  Thorax  considered  in  a  General  Manner,  with  respect  to 
their  Movements       .... 
A.RTICLE  IV. — Articulations  of  the  Anterior  Limbs 

1.  Scapulo-humeral  Articulation 

2.  Humero-radial  Articulation 

3.  Radio- ulnar  Articulation 

4.  Articulations  of  the  Carpus        .  , 


xii 


TABLE  OF  CONTENTS. 


5.  Intermetacarpal  Articulations   .... 

6.  Metacarpo-plialangeal  Articulations 

7.  Articulation  of  the  First  Phalanx  with  the  Second,  or  First 

Articulation  .... 

8.  Articulation  of  the  Second  Phalanx  with  tlie  Third,  Second  Interphalangeal 

Articulation,  or  Articulation  of  the  Foot 
,  \bticle  V. — Articulations  of  the  Posterior  Limbs 

1.  Articulations  of  tlie  Pelvis 

2.  Coxo- femoral  Articulation  . 

3.  Femoro-tibial  Articulation 

4.  Tibio- fibular  Articulation    . 

5.  Articulations  of  the  Tarsus,  or  Hock      . 
Chapter  III.— The  Articulations  in  Birds    . 

THIRD   SECTION. -THE   MUSCLES 

Chapter  I.— General  Considerations  on  the  Striped  Muscles 

The  Striped  Muscles  in  General        ..... 

Structure  of  the  Striped  Muscles  .... 

Physico-chemical  Properties  of  Striped  Muscles 

Physiological  Properties  of  Striped  Muscles 

Appendages  of  the  Muscles   ...... 

Manner  of  Studying  the  Muscles 
Chapter  II.— The  Muscles  of  Mammalia  in  Particular 
Article  I. — The  Muscles  of  the  Trunk 

Subcutaneous  Region  ...... 

Flesliy  Pannicuius  (Panniculus  Carnosus) 

Cervical  Region         ....... 

A.  Superior  Cervical  or  Spinal  Region  of  the  Neck 

1.  Rhomboideus  ...... 

2.  Angularis  Muscle  of  the  Scapula  (Levator  Anguli  Scapulae) 

3.  Splenius         ....... 

4.  Complexus  (Complexus  Major)    .... 

5.  Trachelo-mastoideus  (Complexus  Minor) 

6.  Spinalis  or  Semispinalis  Colli      .... 

7.  Intertransversales  Colli  ..... 

8.  Great  Oblique  Muscle  of  the  Head  (Obliquus  Capitis  Auticus  or  Inferioris) 

9.  Small    Oblique    Muscle   of  the    Head   (Obliquus    Capitis    Posticus    or 

Superioris) 

10.  Great  Posterior  Straight  Muscle  of  the  Head  (Rectus  Capitis  Posticus 

Major)  ........ 

11.  Small  Posterior  Straight  Muscle  (Rectus  Capitis  Posticus  Minor) 
Differential  Ciiaracters    ....... 

B.  Inferior  Cervical  or  Trachelian  Region 

1.  Subcutaneous  Muscle  of  the  Neck  (Cervical  Panniculus)  . 

2.  Mastoido-humeralis  (Levator  Humeri) 

3.  Sterno-maxillaris  ...... 

4.  Sterno-thyro-hyoideus  ..... 

5.  Subscapulo-hyoideus         ...... 

6.  Great  Anterior  Straight  Muscle  of  the  Head  (Rectus  Capitis  Auticus 

Major)         ........ 

7.  Small   Anterior  Straight  Muscle  of  the  Head  (Rectus  Capitis  Auticus 
Minor)      ....... 

8    Small  Lateral  Straight  Muscle  (Rectus  Capitis  Lateralis) 
9.  Scalenus  ....... 

10.  Long  Muscle  of  the  Neck  (Longus  Colli) 

Differential  Characters   ...... 

Spinal  Region  of  the  Back  and  Loins 

1.  Trapezius    ....... 

2.  Great  Dorsal  (Latissimus  Dorsi) 

3.  Small  Anterior  Serrated  Muscle  (Seiratus  Anticue) 

4.  Small  Posterior  Serrated  Muscle  (Serratus  Posticus) 

5.  Ilio-spiualis  Muscle  (Longissimus  Dorsi) 


TABLE  OF  CONTENTS. 


6.  Common  Intercostal  Muscle  (Transversalis  Costarum)  . 

7.  Transverse  Spinous  Muscle  of  the  Back  and  Loins  (Semispinalis  of  the 

Back  and  Loins)  ...... 

Differential  Characters  ..... 

Comparison  of  the  Muscles  of  the  Back,  Neck,  and  Cervix  in  Man  with 
analogous  Muscles  in  tbe  Domesticated  Animals 

1.  Muscles  of  the  Back  and  Cervix  .... 

2.  Muscles  of  the  Neck  ..... 
Sublumbar  or  Inferior  Lumbar  Region  .... 

1.  Iliac  Fascia  or  Lumbo-iliac  Aponeurosis 

2.  Great  Psoas  Muscle  (Psoas  Magnus)     .... 
3    Iliac  Psoas  Muscle  (Iliacns)  .... 

4.  Small  Psoas  Muscle  (Psoas  Parvus)        .... 

5.  Square  Muscle  of  the  Loins  (Quadratus  Lumborum) 

6.  Intertransversales  of  the  Loins  (Intertraiisversales  Lumborum) 
Differential  Characters    ...... 

Comparison  of  the  Sublumbar  Muscles  of  Man  with  those  of  Animals 
Coccygeal  Region  ...... 

1.  Sacro-coccygeal  Muscles  .... 

2.  Ischio-coccygeus  (Compressor  Coccygeus)   . 
Region  of  the  Head  ...... 

A.  Facial  Region        ...... 

1.  Labialis  or  Orbicularis  of  the  Lips  (Orbicularis  Oris) 

2.  Zygomatico-labialis  (Zygomaticus) 

3.  Supermaxillo-labialis  (Levator    Labii    Superioris   Proprius,  or  Nasalis 

Longus)      ...... 

4.  Maxillo-labialis  (Depressor  Labii  Inferioris) 

5.  Mento-labialis,  or  Muscle  of  the  Chin  (Levator  Menti) 

6.  Intermediate  Posterior  Muscle      .... 

7.  Alveolo-labialis  (Buccinator) .... 

8.  Supernaso -labialis  (Levator  Labii  Superioris  alaequi  Nasi) 

9.  Great  Supermaxillo-nasalis  (Dilatator  Naris  Lateralis) 

10.  Small  Supermaxillo-nasalis  (Dilatator  Naris  Superioris)  . 

11.  TransversalLs  Nasi  (Dilatator  Naris  Transversalis)     . 

B.  Palpebral  Region  ...... 

1.  Orbicularis  of  the  Eyelids  (Orbicularis  Palpebrarum) 

2.  Frouto-Palpebral,  or  Corrugator  Supercilii 

3.  Lachrymalis  Muscle  ..... 

C.  Auricular  or  Conchal  Region  .... 

1.  Zygomaticus-auricularid  (AttoUens  Anticus)  . 

2.  Temporo-auricularis  Externus  (Attollens  Maximus) 

3.  Scuto-auricularis  Externus    .... 

4.  Cervico-auriculares  (Retrahentes  Aurem) 

5.  Parotido-auricularis  (Abducens,  or  Deprimens  Aurem) 

6.  Temporo  auricularis  Internus  (Attollens  Posticus) 

7.  Scuto-auricularis  Internus      .... 

8.  Mastoido-auricularis         ..... 

D.  Masseteric  or  Temporo-maxillary  Region 

1.  Masseter.  ...... 

2.  Temporalis    ...... 

3.  Internal  Pterygoid  (Pterygoideus  Internus) 

4.  External  Pterygoid  (Pterygoideus  Externus) 

5.  Digastricus  (Stylo-maxillaris)      .... 
Z.  Hyoideal  Region  ..... 

1.  Mylo-hyoideus     .  .  .  ... 

2.  Genio-hyoideus  ..... 

3.  Stylo-hyoideus     ...... 

>.  Kerato-hyoideus  (Hyoideus  Parvus)  .  ,  , 

J.  Occipito-styloideus  ..... 

6.  Hyoideus  Transversus  .... 
Differential  Characters    ...... 


PAGE 

265 


jdT 


TABLE  OF  CONTENTS. 


1.  Facial  Regrion  .  >  .  . 

2.  Palpebral  Region  .  «  .  .  . 

3.  Masseteric  or  Temporo-maxillary  Region    . 

4.  Hyoideal  Region  .  .  .  .  . 
Comparison  of  the  Muscles  of  the  Human  Head  with  those  of  the  Domesticated 

Animals      .  ...... 

1.  Epicranial  Muscles       ..... 

2.  Muscles  of  the  Face  ..... 

3.  Muscles  of  the  Lower  Jaw         .  „  .  . 

4.  Hyoideal  Muscles   .  .  ,  .  . 
Axillary  Region        ...                          ,             . 

1.  Superficial  Pectoral  (Pectoralis  Anticus  and  Transversua)  . 

2.  Deep  Pectoral  (Pectoralis  Magnus  and  Parvus)  , 
Differential  Characters    ...... 

Costal  Region  ....  . 

1.  Serratus  Magnus     ...... 

2.  External  Intercostala    .  .  . 

3.  Internal  Intercostuls  o  .  .  .  . 

4.  Leva  tores  Costarum      ..... 

5.  Triangularis  Stemi  ..... 
Differential  Characters           ..... 
Comparison  of  the  Thoracic  Muscles  of  Man  with  those  of  the  Domesticated 

Animals  ...... 

Inferior  Abdominal  Region  ..... 

1.  Abdominal  Tunic  (Tunica  Abdominalis,  Tunica  Elastica) 

2.  White  Line  (Linea  Alba)    ..... 

3.  Great    or   External     Oblique    of    the   Abdomen   (Obliquus     Abdominis 

Externus)       ....  ... 

4.  Small    or    Internal    Oblique    of    the    Abdomen    (Obliquus     Abdominis 

Internus)  ....... 

5.  Great  Straight  Muscle  of  the  Abdomen  (Rectus  Abdominis) 

6.  Transverse  Muscle  of  the  Abdomen  (Transversalis  Abdominis) 
Differential  Characters  ...... 

Comparison  of  the  Abdominal  Muscles  of  Man  with  those  of  Animals 
Diaphragmatic  Region  .  .  o  .  . 

Diaphragm      .  .  .  .  .  .  =  .  . 

Differential  Characters  ....... 

Comparison  of  the  Diaphragm  of  Man  witli  that  of  Animals 
Article  II. — Muscles  of  the  Anterior  Limbs  .  «  .  o 

Muscles  of  the  Shoulder  .  .  .... 

A.  External  Scapular  Region         ..... 

1.  External  Scapular  Aponeurosis    ...... 

2.  Long  Abductor  of  the  Arm,  or  Scapular  Portion  of  the  Deltoid  (Teres 

Externus)    .....  .  . 

3.  Short  Abductor  of  the  Arm  (Po.itea  Spinatus  Minor),  or  Teres  Minor 

4.  Supra-spinatus  (Antea  Spinatus)  .  .  .  . 

5.  lufra-spinatus  (Postea  Spinatus)         ..... 

B.  Internal  Scapular  Region  ....... 

1.  Subscapuliiris  ..... 

2.  Adductor  of  the  Arm  (Teres  Internus,  or  Teres  Major) 

3.  Coraco-humeralis,  Coraco-brachialis,  or  Omo-brachialis 

4.  Small  Scapulo-humeralis  (Scapulo-Humeralis  Gracilis,  Scapulo-Hume- 

ralis  Posticus)         ....... 

Differential  Characters    ........ 

Comparison  of  the  Muscles  of  the  Shoulder  of  Man  with  those  of  Animals    . 
Muscles  of  the  Arm  .  .  ,  .  .  . 

A.  Anterior  Brachial  Region  ...  .  . 

1.  Long  Flexor  of  the  Forearm  (Flexor  Braehii),  or  Brachial  Biceps 

2.  Short  Flexor  of  the  Forearm  (Humeralis  Obliquus,  Brachialis  Anticus, 

or  Humeralis  Externus)  ...... 

B.  Posterior  Brachial  Region         ,  o  ... 


PAGE 

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290 
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291 
291 


292 
292 

292 
293 
296 
296 
296 
297 
297 
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299 
299 


300 


305 
305 
307 
307 
308 
308 
310 
310 
310 
310 
310 
311 

311 
312 
312 
313 
314 
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315 
315 

316 
316 
316 
316 
317 
317 


319 


TABLE  OF  CONTENTS. 


1.  Large  Extensor  of  the  Forearm  (Caput  Magnum) 

2.  Short  Extensor  of  the  Forearm  (Caput  Medium) 

3.  Middle  Extensor  of  the  Forearm  (Caput  Parvum),  luternal  portion  of  the 

Triceps  ....... 

4.  Small  Extensor  of  the  Forearm,  or  Anconeus 
Dififerential  Characters    ....... 

Comparison  of  the  Muscles  of  the  Arm  of  Man  with  those  of  Animals 
Muscles  of  the  Forearm  ....... 

Antibrachial  Aponeurosis      ...... 

A.  Anterior  Antibrachial  Region         ..... 

1.  Anterior  Extensor  of  the  Metacarpus  (Extensor  Metacarpi  Magnus) 

2.  Oblique  Extensor  of  the  Metacarpus  (Extensor  Metacarpi  Obliquus) 

3.  Anterior  Extensor  of  the  Plialanges  (Extensor  Pedis) 

4.  Lateral  Extensor  of  the  Phalanges  (Extensor  Suffragiuis) 

B.  Posterior  Antibrachial  Region  ..... 

1.  External  Flexor  of  the  Metacarpus  (Flexor  Metacarpi  Externus,  or  Pos- 

terior Ulnaris)  .... 

2.  Oblique  Flexor  of  the  Metacarpus  (Flexor  Metacarpi  Medius,  or  Anterior 

Ulnaris)       ........ 

3.  Internal  Flexor  of  the  Metacarpus  (Flexor  Metacarpi  laternus,  or  Pal 

maris  Magnus)  ...... 

4.  Superficial  Flexor,  Sublimis  of  the  Phalanges  (Flexor  Pedis  Perforatus) 

5.  Deep  Flexor  of  the  Phalanges  (Flexor  Pedis  Perforans)  . 
Dififerential  Characters  .... 

Muscles  proper  to  the  Forearm  in  Carnivora    . 

1.  Proper  Extensor  of  the  Tliumb  and  Index 

2.  Long  Supinator  .... 

3.  Short  Supinator         .... 

4.  Round  Pronator  .... 

5.  Square  Pronator         ...... 

Comparison  of  the  Muscles  of  the  Forearm  of  Man  with  those  of  Animals 

1.  Anterior  Region  ...... 

2.  External  Region     .... 

3.  Posterior  Region  .... 
Muscles  of  the  Anterior  Foot  or  Hand     . 

A.  Muscles  of  the  Anterior  Foot  in  Carnivora 
1    Short  Abductor  of  tlie  Thumb 

2.  Opponens  of  the  Thumb 

3.  Short  Flexor  of  the  Thumb 

4.  Adductor  of  the  Index 

5.  Cutaneous  Palmar  (Palmaris  Brevis) 

6.  Adductor  of  the  Small  Digit 

7.  Short  Flexor  of  the  Small  Digit 

8.  Opponens  of  the  Small  Digit 

9.  Lumbrici  ..... 
10.  Metacarpal  Interosseous  Muscles 

B.  Muscles  of  the  Anterior  Foot  in  the  Pig     . 

C.  Muscles  of  the  Anterior  Foot  in  Solipeds 

D.  Muscles  of  the  Anterior  Foot  in  Ruminants 
Comparison  of  the  Hand  of  Man  with  that  of  Animals 

A.  Muscles  of  the  Thenar  Eminence  . 

B.  Muscles  of  the  Hypothenar  Eminence  . 

C.  Interosseous  Muscles  .... 
Article  III.— Muscles  of  the  Posterior  Limbs 

Muscles  of  the  Gluteal  Region,  or  Croup 

1.  Superficial  Gluteus  (Gluteus  Externus) 

2.  Middle  Gleuteus  (Gluteus  Medius,  Gluteus  Maximus) 

3.  Deep  Gluteus  (Gluteus  Internus) 
Dififerential  Characters  ..... 
Comparison  of  the  Gluteal  Muscles  of  Man  with  those  of  Animals 
Muscles  of  the  Thigh     .... 


PAGE 

319 
320 


rvi  TABLE   OF  CONTENTS. 


A.  Anterior  Crural,  or  Femoral  Region  .... 

1.  Muscle  of  the  Fascia  Lata  (Tensor  Fascia  Latae,  Tensor  Vaginae  Femoris) 

2.  Crural  Triceps  ....... 

3.  Crureus,  Rectus  Parvus,  Anterior  Gracilis 

B.  Posterior  Crural  Region  ...... 

1.  Biceps  Femoris,  Triceps  Abductor  Femoris 

2.  Semitendinosus  Muscle  (Biceps  Rotator  Tibialis)      . 

3.  Semimembranosus  (Adductor  Magnus)    .... 

C.  Internal  Crural  Region  ...... 

1.  Great  Adductor  of  the  Leg  (Sartorius)     .... 

2.  Short  Adductor  of  the  Leg  (Gracilis)  .... 

3.  Pectineus  .  ... 

4.  Small  Adductor  of  the  Thigh  (Adductor  Parvus,  Adductor  Brevis)  . 

5.  Great  Adductor  of  the  Thigh  (Adductor  Maguus,  Adductor  Longus) 

6.  Quadrate  Crural  (Quadratus  Femoris,  Iscliio-Femoralis) 

7.  External  Obturator  (Obturator  Externus) 

8.  Internal  Obturator  (Obturator  Internus)        .... 

9.  Gemelli  ....... 

Differential  Characters  ....... 

1.  Anterior  Crural  Region       ...... 

2.  Posterior  Crural  Region  ...... 

3.  Internal  Crural  Region       ...... 

Comparison  of  the  Muscles  of  Man's  Thigh  with  those  of  the  Thigh  of  Animals 

1.  Anterior  Muscles  ....... 

2.  Muscles  of  the  Posterior  Region      ..... 

3.  Muscles  of  the  Internal  Region  ..... 

Muscles  of  the  Leg  ....  .  . 

Tibial  Aponeurosis  ........ 

A.  Anterior  Tibial  Region      ...... 

1.  Anterior  Extensor  of  the  Phalanges  (Extensor  Pedis) 

2.  Lateral  Extensor  of  the  Phalanges  (Peroneus)    . 

3.  Flexor  of  the  Metatarsus  (Flexor  Metatarsi) 

B.  Posterior  Tibial  Region      ...... 

1.  Gastrocnemius,  or  Gemelli  of  the  Tibia  (Gastrocnemius  Externus)     . 

2.  Soleus  (Plitntaris)  ...... 

3.  Superficial  Flexor  of  the  Phalanges  (Flexor  Perforatus,  Gastrocnemius 

Internus)    .  .  ..... 

4.  Popliteus  ....... 

5.  Deep  Flexor  of  the  Phalanges  (Perforans,  Flexor  Pedis) 

6.  Oblique  Flexor  of  the  Phalanges  (Flexor  Accessorius)     . 
Differential  Characters  ...... 

1.  Anterior  Tibial  Region       ...... 

2.  Posterior  Tibial  Region  ...... 

Comparison  of  the  Muscles  of  the  Leg  of  Man  with  those  of  Animals     . 

1.  Anterior  Region  ....... 

2.  External  Region      ....... 

3.  Posterior  Region  ....... 

Muscles  of  the  Posterior  Foot 

Pedal  Muscle  (Extensor  Pedis  Brevis,  Extensor  Brevis  Digitorum)    . 

Differential  Characters    ....... 

Comparison  of  the  Muscles  of  the  Foot  of  Man  with  those  of  Animals 

\.  Dorsal  Region         ....... 

2.  Plantar  Region  ....... 

3.  Interosseous  Muscles  .... 
Chapter  IIL— The  Muscles  in  Birds  ..... 
Chapter  IV.— General  Table  of  the  Attachment  of  the  Muscles  in 

Solipeds  ....... 


^^ 


TABLE  OF  CONTENTS. 


XTii 


BOOK  11. 


THE  DIGESTIVE  APPARATUS. 

Chapter  I.— General  Considerations  on  the  Digestive  Apparatus 
Chapter  II.— The  Digestive  Apparatus  in  Mammalia 
Article  I.— Preparatory  Organs  of  the  Digestive  Apparatus     . 
The  Mouth  ....... 

1.  Lips       ........ 

2.  Cheeks        ....... 

3.  Palate  ....... 

4.  Tongue       ....... 

5.  Soft  Palate        ....... 

6.  Teeth  ....... 

7.  The  Mouth  in  General  ..... 
DifiFerential  Characters  in  the  Mouth  of  the  other  Animals 

Comparison  of  the  Mouth  of  Man  with  that  of  Animals 

Table  of  Dentition  ...... 

The  Salivary  Glands  ...... 

1.  Parotid  Gland  ...... 

2.  Maxillary  or  Submaxillary  Gland  .... 

3.  Sublingual  Gland    ...... 

4.  Molar  Glands    ....... 

5.  Labial,  Lingual,  and  Staphyline  Glands 
DiflFereutial  Characters  in  the  Salivary  Glands  of  the  other  Animals 

Comparison  of  the  Salivary  Glands  of  Man  with  those  of  Animals 
The  Pharynx  ....... 

DiflFereutial  Characters  in  the  Pharynx  of  the  other  Animals   . 
Comparison  of  the  Pharynx  of  Man  with  that  of  Animals 
The  (Esophagus  ...... 

DiflFereutial  Characters  in  the  (Esophagus  of  the  other  Animals     . 
Comparison  of  the  (Esophagus  of  Man  with  that  of  Animals 
Article  II. — The  Essential  Organs  of  Digestion 
The  Abdominal  Cavity  ..... 

DiflFereutial  Characters  in  the  Abdominal  Cavity  of  the  other  Animals 
Comparison  of  the  Abdominal  Cavity  of  Man  with  that  of  Animals 
The  Stomach  ....... 

1.  The  Stomach  of  Solipeds  .... 

DiflFereutial  Characters  in  the  Stomach  of  the  other  Animals 

1.  The  Stomach  of  the  Rabbit  .  .  .  . 

2.  The  Stomach  of  the  Pig  ....  . 

3.  The  Stomach  of  Carnivora  ..... 

4.  The  Stomach  of  Ruminants       ..... 
Comparison  of  the  Stomach  of  Man  with  that  of  Animals 
The  Intestines  ....... 

1.  The  Small  Intestine  ..... 

2.  The  Large  Intestine      ...... 

A.  Csecum    ....... 

B.  Colon  ....... 

0.  Rectum    ....... 

Diflferential  Characters  in  the  Intestines  of  the  other  Animals 

1.  The  Intestines  of  the  Rabbit  .... 

2.  The  Intestines  of  Ruminants  .... 

3.  The  Intestines  of  the  Pig  .... 

4.  The  Intestines  of  Carnivora    .  .... 
Comparison  of  the  Intestines  of  Man  with  those  of  Animals 
General  and  Comparative  Survey  of  the  Abdominal  or  Essential  Portion  of  the 

Digestive  Canal  ...... 

Organs  Annexed  to  the  Abdominal  Portion  of  the  Digestive  Canal 

1.  Liver  ....... 

2.  Pancreas      ....... 

8.  Spleen  ..... 


TABLE  OF  CONTENTS. 


Diflferential  Characters  in  the  Organ8  annexed  to  the  Abdonainal  Portion  of  the 

Digestive  Canal  in  the  other  Animals        .....       508 
Comparison  of  the  Organs  annexed  to  the  Abdominal  Portion  of  the  Digestive 

Canal  of  Man  with  those  of  Animals       .....  510 

Chapterlll.— The  Digestive  Apparatus  of  Birds      .  .  .  .511 


BOOK   III. 

RESPIRATORY  APPARATUS. 

Chapter  I.— Respiratory  Apparatus  in  Mammalia         ...  517 

The  Nasal  Cavities          ......             c             .  517 

1.  The  Nostrils                   .......  518 

2.  The  Nasal  Fossae                  ....                          .             .  519 

3.  The  Sinuses      .....                          ,             .  524 
DifTerential  Characters  in  the  Nasal  Cavities  of  the  other  Animals      .             .  526 

Comparison  of  the  Nasal  Cavities  of  Man  with  those  of  Animals                     .  527 

The  Air- tube  succeeding  the  Nasal  Cavities        .....  527 

1.  The  Larynx      ........  527 

2.  The  Trachea            .......  536 

3.  The  Bronchi      ........  539 

Differential  Characters  in  the  Air-tube  succeeding  the  Nasal  Cavities  in  the 

other  Animals      ........  541 

Comparison  of  the  Larynx   and  Trachea  of  Man  with   these  Organs  in  the 

Domesticated  Animals   .......  542 

The  Thorax        .........  542 

Differential  Characters  in  the  Thorax  of  the  other  Animals            .            .  545 

The  Lungs          .........  546 

Differential  Characters  in  the  Lungs  uf  the  other  Animals              .             .  552 

Comparison  of  the  Larynx,  Trachea,  and  Lungs  of  Man  with  those  of  Animals  .  553 

The  Glandiform  Bodies  connected  with  the  Respiratory  Apparatus                .  554 

1.  The  Thyroid  Body  or  Gland  .  .  .  .  .  .554 

2.  The  Thymus  Gland      .......  555 

Differential  Characters  in  the  Glandiform  Bodies  annexed  to  the  Respiratory 

Apparatus  in  the  other  Animals   ......  556 

Comparison  of  the  Glandiform  Bodies  annexed  to  the  Respiratory  Apparatus 

in  Man  with  those  of  Animals    ......  557 

Chapter  II.— The  Respiratory  Apparatus  of  Birds  .  .  .557 


BOOK   IV. 
URINARY  APPARATUS. 

1.  The  Kidneys 568 

2.  The  Ureters  ........  574 

3.  The  Bladder 575 

4.  The  Urethra  .  .  .  .  .  .  .  .  578 

5.  The  Supra-renal  Capsules  ......  578 

Differential  Characters  of  the  Urinary  Apparatus  in  the  other  Animals  .  579 

Comparison  of  the  Urinary  Apparatus  of  Man  with  that  of  Animals  .  581 

BOOK  V. 
CIRCULATORY  APPARATUS. 

rlRST   SECTION.— THE   HEART  .  ....  583 

1.  The  Heart  as  a  Whole      ......  583 

2.  External  Conformation  of  the  Heart  .....  584 

3.  Internal  Conformation  of  the  Heart  .....  587 


TABLE  OF  CONTENTS. 


4.  Structure  of  the  Heart  .... 

5.  The  Pericardium  ..•••• 

6.  The  Action  of  the  Heart 
Differential  Characters  in  the  Heart  of  the  other  Animals 

Comparison  of  the  Heart  of  Man  with  that  of  Animals    . 
SECOND   SECTION.— THE   ARTERIES 
Chapter  I.— General  Considerations    . 
Chapter  II.— Pulmonary  Artery    . 
Chapter  III.— Aorta        ..... 
Article  I.— Common  Aorta,  or  Aortic  Trunk 

Cardiac,  or  Coronary  Arteries, 
Article  II. — Posterior  Aorta  .... 

Parietal  Branches  of  the  Posterior  Aorta 

1.  Intercostal  Arteries  .... 

2.  Lumbar  Arteries  .... 

3.  Diphragmatic  Arteries  .... 
Middle  Sacral  Artery            .... 

Visceral  Branches  of  the  Posterior  Aorta    . 

1.  Broncho-CEsophageal  Trunk 

2.  Cceliac  Artery  ..... 

3.  Anterior  or  Great  Mesenteric  Artery 

4.  Posterior  or  Small  Mesenteric  Artery 

5.  Renal  or  Emulgent  Arteries 

6.  Spermatic  Arteries     .  .  .  '  • 

7.  Small  Testicular  Arteries  (Male),  Uterine  Arteries  (Female) 
Differential  CLaracters  in  the  Posterior  Aorta  and  its  Collateral  Branches  in 

the  other  Animals       .  .  .  .  • 

1.  Posterior  Aorta  in  Ruminants 

2.  Pesterior  Aorta  in  the  Pig     .... 

3.  Posterior  Aorta  in  Carnivora 
Comparison  of  the  Aorta  of  Man  with  that  of  Animals 

Article  III.— Internal  Iliac  Arteries,  or  Pelvic  Trunks 

1.  Umbilical  Artery  .  .  •  •  • 

2.  Internal  Pudic  Artery,  or  Artery  of  the  Bulb 

3.  Lateral  Sacral  or  Subsacral  Artery 

4.  Ilio-lumbar  Artery,  or  Iliaco-muscular 

5.  Gluteal  Artery  .  .  .  •  • 

6.  Obturator  Aitery     .  .  •  •  • 

7.  Uiaco-femoral  Artery    .  .  •  •  •  •. 
Differential  Characters  in  the  Internal  Iliac  Arteries  of  the  other  Animals 

1.  Internal  Iliac  Arteries  of  Ruminants 

2.  Internal  Iliac  Arteries  of  the  Pig 

3.  Internal  Iliac  Arteries  of  Carnivora     .... 
Comparison  of  the  Internal  Iliac  Arteries  of  Man  with  those  of  Animals 

iiETicLE  IV.— External  Iliac  Arteries,  or  Crural  Trunks 
Femoral  Artery  ...••• 

1.  Prepubic  Artery         .  •  •  *      .       "       ^  x," 

2.  Profunda  Femoris,  Great   Posterior  Muscular  Artery  of  the 

Deep  Muscular  Artery  .  .  •  •  • 

3.  Superficialis  Femoris,  Superficial  Muscular,  or  Great  Anterior 

Artery         ..-•••• 

4.  Innominate  or  Small  Muscular  Arteries  . 

5.  Saphena  Artery         ..•••• 
Popliteal  Artery  ..•••• 
Terminal  Branches  of  the  Popliteal  Artery 

1.  Posterior  Tibial  Artery    .  .  •  •  • 

2.  Anterior  Tibial  Artery  .  .  .  •  • 

3.  Pedal  Artery        .  •  •  •  ',/»., 
Differential  Characters  in  the  External  Iliac  Arteries  of  the  other  Animals 

1.  External  Iliac  Arteries  of  Ruminants 

2.  External  Iliac  Arteries  of  the  Pig  .... 


Thigh 


Muscular 


TABLE  OF  CONTENTS. 


3.  External  Iliac  Arteries  of  Carnivora. 
Comparison  of  the  External  Iliac  Arteries  of  Man  with  those  of  Animals 
Article  V. — Anterior  Aorta  ..... 

Article  VI.— Brachial  Trunks,  or  Axh.lary  Arteries 
Collateral  Branches  of  the  Axillary  Arteries 

1.  Dorsal,  Dorso-muscular.  or  Transverse  Cervical  Aiteiy     . 

2.  Superior  Cervical,  Cervico-muscuiar,  or  Deep  Cervical  Artery 

3.  Vertebral  Artery  ...... 

4.  Internal  Tiioiacic  Pectoral,  or  Internal  Mammary  Artery 

5.  External,  Infi-rior  Thoracic,  or  External  Mammary  Artery 

6.  Inferior  Cervical  Artery  .  ^      .  .  . 

7.  Supra-scapular  Artery      ...... 

8.  Infra-scapular  or  Subscapular  Artery 
Humeral  Artery,  or  Terminal  Artery  of  the  Brachial  Trunk    . 

1.  Anterior  Radial  (or  Spiral)  Artery      .... 

2.  Posterior  Radial  Artery    ...... 

(1)  First  Terminal  Branch  of  the  Posterior  Radial  (Radio-Palmar)  Artery, 
ur  Common  Trunk  of  the  Interosseous  Metacarpals 

(2)  Second  Terminal  Branch  of  the  Posterior  Radial  Artery,  or  Collateral 

Artery  of  the  Cannon  .... 

Dififerential  Characters  in  the  Axillary  Arteries  of  tht  other  Animals 

1.  Axillary  Arteries  of  Ruminants  .... 

2.  Axillary  Arteries  of  the  Pi^         .... 

3.  Axillary  Arteries  of  Carnivora  .... 
Comparison  of  the  Axillary  Arteries  of  Man  with  those  of  Animals 

Article  VII.— Common  Carotid  Arteries    .... 

Occipital  Artery  ...... 

Internal  Carotid  Artery      ...... 

External  Carotid  Artery  ...... 

Collateral  Branches  of  the  External  Carotid  Artery 

1.  Submaxillary,  Facial,  or  Glosso-facial  Artery 

2.  Maxillo-muscular  Artery        ..... 

3.  Posterior  Auricular  Artery  .  .  .  '. 
Terminal  Branches  of  the  External  Carotid  Artery 

1.  Superficial  Temporal  Artery,  or  Temporal  Trunk 

2.  Internal  Maxillary,  or  Gutturo-maxillary  Artery 
Differential  Chaiaftt-rs  in  the  Carotid  Arteries  of  the  other  Animals 

1.  Carotid  Arteries  of  Carnivora  .... 

2.  Carotid  Arteries  of  the  Pig  .... 

3.  Carotid  Arteries  of  Ruminants  .... 
Comparison  of  the  Carotid  Arteries  of  Man  with  those  of  Animals 

THIRD   SECTION. -THE   VKINS  ..... 

Chapter  I.— General  Considerations  . 
Chapter  II.— Veins  of  the  Lesser  Circulation,  or  Pulmonary  Veins 
Chapter  III.— Veins  of  the  General  Circulation 
Article  I.— Cardiac  or  Coronary  Veins 
Abticle  II. — Anterior  Vena  Cava 

Jugular  Veins        ..... 
Roots  of  the  Jugular    .... 

1.  Superficial  Temporal  Vein 

2.  Internal  Maxillary  Vein  . 

3.  The  Sinuses  of  the  Dura  Mater 
Axillary  Veins  .... 

1.  Brachial  or  Subscapular  Vein 

2.  Humeral  Vein      .... 

3.  Subcutaneous  Thoracic  or  Spur  Vein 

4.  Deep  Veins  of  the  Forearm 

5.  Superficial  Veins  of  the  Forearm 

6.  Metacarpal  Veins 

7.  Digital  Veins  .... 

8.  Veins  of  the  Ungual  Region,  or  Foot 


TABLE  OF  CONTENTS. 


a   External  Venous  Apparatus 
b.  Internal  or  lutra-osseous  Venous  Apparatus 
Article  III. — Posterior  Vena  Cava 
Plirenic  or  Diaphragmatic  Veins 
Vena  Portse 

1.  Roots  of  the  Vena  Portse 

2.  Collateral  AflBnents  of  the  Vena  Portse 
Renal  Veins     . 
Spermatic  Veins    . 
Lumbar  Veins 
Common  Iliac  Veins 

1.  Internal  Iliac  Vein 

2.  External  Iliac  Vein    . 

3.  Femoral  Vein 

4.  Popliteal  Vein 

5.  Deep  Veins  of  the  Leg 

6.  Superficial  Veins  of  the  Leg 

7.  Metatarsal  Veins 

8.  Veins  of  the  Digital  Region 
Diiferential  Characters  in  the  Veius  of  the  other  Animals 

Comparison  of  the  Veins  of  Man  with  those  of  Animals 
FOURTH   SECTION.— THE   LYMPHATICS 
Chapter  I. — General  Considerations 

Lymphatic  Vessels       ..... 
Lymphatic  Glands,  or  Ganglia 
Chapter  II.— The  Lymphatics  in  Particular 
Article  I. — The  Thoracic  Duct       .  •  • 

Article  II.— The  Lymphatics  which  constitute  the  Affluents  of  the  Thoracic 
Duct  . 


Lymphatics  of  the  Abdominal  Limb,  Pelvis, 
inguinal  Organs 


Abdominal  Parietes,  and  Pelvi 


1.  Sublumbar  Glands 

2.  Deep  Inguinal  Glands 

3.  Superficial  Inguinal  Glands 

4  Popliteal  Glands 

5.  Iliac  Glands 

6.  Precrural  Glands 
Lymphatics  of  the  Abdominal  Viscera 

1.  Glands  and  Lymphatic  Vessels  of  the  Rectum  and  Floating  Colon 

2.  Glands  and  Lymphatic  Vessels  of  the  Double  Colon 

3.  Glands  and  Lymphatic  Vessels  of  the  Csecum 

4.  Glitnds  and  Lymphatic  Vessels  of  the  Small  Intestine 

5  Glands  and  Lymphatic  Vessels  of  the  Stomach 
6.  Glands  and  Lymphatic  Vessels  of  the  Spleen  and  Liver  . 

Glands  and  Lymphatic  Vessels  of  the  Organs  contained  in  the  Thoracic  Cavity 
Glands  and  Lymphatic  Vessels  of  the  Thoracic  Parietes 
Lyijiphatic  Vessels  of  the  Head,  Neck,  and  Anterior  Limb 

1.  Prepectoral  Glands  ..... 

2.  Pharyngeal  Glands     ..... 

3.  Submaxillary,  or  Subglossal  Glands 

4.  Prescapular  Glands    ..... 

5.  Brachial  Glands  ...... 

Article  III. — Great  Lymphatic  Vein 

Diflerential  Characters  in  the  Lymphatics  of  the  other  Animals 
Chapter  III.— The  Circulatory  Apparatus  in  Birds    . 
Article  I.— The  Heart   ...... 

Article  II. — The  Arteries   ..... 

Article  III.— The  Veins  •  .  ,  ,  , 

Article  IV. — The  Lymphatics 


xm  TABLE  OF  CONTENTS. 

BOOK  VI. 
APPARATUS   OF  INNERVATION. 

FIRST   SECTION.— THE   NERVOUS   SYSTEM   IN   GENERAL 

General  Conformation  of  the  Nervous  System 
Structure  of  the  Nervous  System  .... 

Properties  and  Functions  of  the  Nervous  Systems      .... 
SECOND   SECTION.— THE   CENTRAL   AXIS   OF   THE   NERVOUS   SYSTEM 
Chapter  I.— Protective  and  Enveloping  Parts  of  the  Cerebro-spinal  Axis 
The  Bony  Case  containing  the  Central  Cerebro-spinal  Axis 

1.  The  Spinal  Canal 

2.  The  Cranial  Cavity   . 
The  Envelopes  of  the  Cerebro-spinal  Axis 

1.  The  Dura  Mater 

2.  The  Arachnoid    .... 

3.  The  Pia  Mater  ....... 

Differential  Characters  in  the  Protecting  and  Enveloping  Parts  of  the  Cerebro- 
spinal Axis  in  the  other  Animals  . 

Comparison  of  the  Protective  and  Enveloping  Parts  of  the  Cerebro-spinal  Axis 
of  Man  with  those  of  Animals     ...... 

Chapter  II.— The  Spinal  Cord  ...... 

External  Conformation  of  the  Spinal  Cord 
Internal  Conformation  and  Structure  of  the  Spinal  Cord 
Differential  Characters  in  the  Spinal  Cord  of  the  other  Animals    . 
Comparison  of  the  Spinal  Cord  of  Man  with  that  of  Animals 
Chapter  III.— The  Brain,  or  Eneephalon  .... 

Article  I.— The  Brain  as  a  Whole       ..... 

Article  II. — The  Isthmus      ...... 

External  Conformation  of  the  Isthmus  .... 

1.  The  Medulla  Oblongata  ..... 

2.  The  Pons  Varolii  ...... 

3.  The  Crura  Cerebri     ...... 

4.  The  Crura  Cerebelli  ...... 

5.  The  Valve  of  Vieusseus  ..... 

6.  The  Corpora  Quadrigemina,  or  Bigemina 

7.  The  Optic  Tiialami    ...... 

8.  The  Pineal  Gland  ...... 

9.  The  Pituitary  Gland  ..... 
Internal  Conformation  of  the  Isthmus  ..... 

1.  The  third  or  Middle  Ventricle,  or  Ventricle  of  the  Thalami  Optici 

2.  The  Aqueduct  of  Sylvius  ..... 

3.  The  Posterior,  or  Cerebellar  Ventricle 
Structure  of  the  Isthmus  ...... 

Differential  Characters  in  the  Isthmus  of  the  other  Animals 

Comparison  of  the  Isthmus  of  Man  with  that  of  Animals 
Article  III. — The  Cerebellum  ..... 

1.  External  Conformation  of  the  Cerebellum    .... 

2.  Internal  Conformation  of  the  Cerebellum 
Differential  Characters  of  the  Cerebellum  in  the  other  Animals 

Comparison  of  the  Cerebellum  of  Man  with  that  of  Animals 
Article  IV. — The  Cerebrum        ...... 

External  Conformation  of  the  Cerebrum    . 

1.  The  Longitudinal  Fissure 

2.  The  Cerebral  Hemispheres     . 
Internal  Conformation  of  the  Brain 

1.  The  Corpus  Callosum 

2.  The  Lateral  or  Cerebral  Ventricles 
8.  The  Septum  Lucidum 

4.  The  Trigonum,  or  Fornix 

5.  The  Hippocampi 


TABLE  OF  CONTENTS. 


xxiii 


6.  The  Corpora  Striata         .... 

7.  The  Choroid  Plexus  and  Velum  Interpositum 
Structure  of  the  Brain  .... 
DifFereutial  Characters  in  the  Brain  of  the  other  Animals 

Comparison  of  the  Cerebrum  of  Man  with  that  of  Animals 
THIKD  SECTION.— THE  NERVES*     . 
Chapter  I.— The  Cranial  or  Encephalic  Nerves 

1.  First  Pair,  or  Olfactory  Nerves 

2.  Second  Pair,  or  Optic  Nerve* 

3.  Third  Pair,  or  Common  Oculo-:JIotor  Nerves 

4.  Fourth  Pair,  or  Pathetici  Nerves  . 

5.  Fifth  Pair,  or  Trigeminal  Nerves 

6.  Sixth  Pair,  or  External  Motor  Ocular  Nerves 

7.  Seventh  Pair,  or  Facial  Nerves 

8.  Eighth  Pair,  Auditory,  or  Acoustic  Nerves 

9.  Ninth  Pair,  or  Glosso-Pharyngeal  Nerves 

10.  Tenth  Pair,  Vagus,  or  Pneumogastric  Nerves 

11.  Eleventh  Pair,  Spinal,  or  Accessory  Nerves  of  the  Pneumogastrics 

12.  Twelfth  Pair,  or  Great  Hypoglossal  Nerves 
Differential  Characters  in  the  Cranial  Nerves  of  the  other  Animals 

Comparison  of  the  Cranial  Nerves  of  Man  with  those  of  Animals 
Chapter  II.— Spinal  Nerves  ... 

Article  I.— Cervical  Nerves  (Eight  Pairs) 
Article  II.— Dorsal  Nerves  (Seventeen  Pairs) 
Article  III. — Lumbar  Nerves  (Six  Pairs) 

Article  IV.— Sacral  Nerves  (Five  Pairs)     .... 
Article  V. — Coccygeal  Nerves  (Six  to  Seven  Pairs) 
Article  VI. — Composite  Nerves  formed  by  the  Inferior  Branches  of 

Spinal  Branches  ...... 

Diaphragmatic  (or  Phrenic)  Nerve       .... 

Brachial  Plexus     ....... 

1.  Diaphragmatie  Branches  ..... 

2.  Levator  Anguli  Scapulae  and  Rhomboideal  Branch 

3.  Serratus  Magnus,  or  Superior  Thoracic  Branch    . 

4.  Pectoral  or  Inferior  Thoracic  Branches 

5.  Subcutaneous  Thoracic  Branch    .... 

6.  Latissimus  Dorsi  Branch        .... 

7.  Axillary  or  Circumflex  Nerve       .... 

8.  Nerve  of  the  Teres  Major       .... 

9.  Subscapular  Branches  .... 

10.  Supra-scapular  Nerve 

11.  Anterior  Brachial  or  Musculo-Cutaneous  Nerve   . 

12.  Radial  (or  Mu^culo-spiral)  Nerve 

13.  Ulnar  or  Culdto-cutaneous  Nerve 

14.  Median  or  Cubito-plantar  Nerve 
Differential  Characters  in  the  Brachial  Plexus  of  the  other  Animals 

Compa4son  of  the  Brachial  Plexus  of  Man  with  that  of  Animals 
Lumbo-Sacral  Plexus  ...... 

A.  Anterior  Portion        ..... 

1.  Iliaco-muscular  Nerves  .... 

2.  Crural  or  Anterior  Femoral  Nerve 

3.  Obturator  Nerve  ..... 

B.  Posterior  Portion        ..... 

4.  Small  Sciatic  or  Anterior  and  Posterior  Gluteal  Nerves 

5.  Great  Sciatic  or  Great  Femoro-popliteal  Nerve 
Collateral  Branches     ...... 

Terminal  Branches  ...... 

Differential  Characters  in  the  Lumbo-sacral  Plexus  of  the  other  Animals 

Comparison  of  the  Lumbo-sacral  Plexus  in  Man  with  that  of  Animals 
Chapter  III.— The  Great  Sympathetic  .... 

1.  Cranial  Portion  of  the  Sympathetic        .... 


887 


TABLE  OF  CONTENTS. 


2.  Cervical  Portion  of  the  Sympathetic  .... 

3.  Dorsal  Portion  of  the  Sympathetic         .... 

4.  Lumbar  Portion  of  the  Sympathetic  .... 

5.  Sacral  Portion  of  the  Sympathetic  ... 
Differential  Characters  in  the  Great  Sympathetic  of  the  other  Animals 

Ciimparison  of  the  Great  Sympathetic  of  Man  with  that  of  Animals  . 
Chapter  IV.— The  Nervous  System  of  Birds  .... 


PAGE 

887 
891 
892 
893 
894 
894 


BOOK   VII. 


APPARATUSES  OF   SENSE. 

Chapter  I.— Apparatus  of  Touch    .  .  .  .  - 

Article  I. — The  Skin       ...... 

Article  II. — The  Appendages  of  the  Skin  .  .  . 

Hairs  ........ 

Horny  Productions  ...... 

1.  The  Hoof  of  Solipeds       ..... 

a.  The  Parts  container!  in  the  Huof    .... 

b.  Description  of  the  Hoof  .... 

2.  The  Claws  of  Kuminants  and  Pachyderms 

3.  The  Claws  of  Carnivora   ..... 

4.  The  Frontal  Horns    ...... 

5.  The  Chestnuts     ...... 

(6.  The  Ergots).  ...... 

Chapter  II.— Apparatus  of  Taste  .... 

Differential  Characters  in  the  Apparatus  of  Taste  in  the  other  Animals 
Comparison  of  the  Apparatus  of  Taste  in  Man  with  that  of  Animals 
Chapter  III.— Apparatus  of  Smell ..... 
Chapter  IV.— Apparatus  of  Vision      .... 
Article  I.— Essential  Organ  of  Vision,  or  Ocdlar  Globe 

Membranes  of  the  Eye  ..... 

A.  Fibrous  Membranes  ...... 

1    The  Sclerotica  ...... 

2.  The  Cornea  ...... 

B.  Musculo-vascular  .  .  c  .  . 

1.  The  Choroid  Membrane      .  ,  ,  .  . 

2.  The  Iris  ...... 

C.  Nerve  Membrane      ...... 

3.  The  Betina       ...... 

The  Media  of  the  Eye        ...... 

1.  Crystalline  Lens  ...... 

2.  Vitreous  Humour       .  .  ... 

3.  Aqueous  Humour  ..... 
Article  II.— Accessory  Organs  of  the  Visual  Apparatus 

Orbital  Cavity  ...... 

Muscles  of  the  Globe  of  the  Eye     ..... 

Protective  Organs  of  the  Eye  ..... 

1.  Eyelids  ....... 

2.  Membrana  Nictitans         ..... 

Lachrymal  Apparatus        ...... 

Differential  Characters  in  the  Visual  Apparatus  of  the  other  Animals 

Comparison  of  the  Visual  Apparatus  of  Man  with  that  of  Animals     . 
Chapter  V.— Auditory  Apparatus       .... 
Article  I. — Internal  Ear,  or  Labyrinth    .... 
The  Osseous  Labyrinth  ..... 

1.  The  Vestibule  ...... 

2.  The  Semicircular  Canals  .... 


899 
904 
904 
907 
908 
908 
914 
921 
921 
922 
922 
922 
922 
924 
924 
924 
925 
926 
927 
927 
927 


929 


933 
936 
936 
937 
938 
938 
938 
939 
941 
941 
943 
944 
946 
947 
947 
947 
947 
948 


TABLE  OF  CONTENTS. 


3.  The  Cochlea 
The  Membranous  Labyrinth 

1.  The  Membranous  Vestibule 

2.  The  Membranous  Semicircular  Canals 

3.  The  Membranous  Cochlea 
Fluids  of  the  Labyrinth     .  .  .  .  , 
Distribution  and  Termination  of  the   Auditory  Nerve  in   the   Membranous 

Labyrinth  ••■•.. 

Article  II.— Middle  Ear,  ob  Case  of  the  Tympanum 

1.  Membrane  of  the  Tympanum        .... 

2.  The  Promontory,  Fenestra  Ovalis,  and  Fenestra,  Rotunda 

3.  The  Mastoid  Cells  .... 

4.  The  Bones  of  the  Middle  Ear 

5.  The  Mucous  Membrane  of  the  Tympanum 

6.  The  Eustachian  Tube 

7.  Tlie  Guttural  Pouches      . 
Article  III.— The  External  Ear     . 

The  External  Auditory  Canal. 
The  Concha,  or  Pavilion    . 

1.  Cartilages  of  the  Concha. 

2.  Muscles  of  the  External  Ear . 

3.  Adipose  Cushion  of  the  External  Ear 

4.  Integuments  of  the  External  Ear 
Differential  Characters  in  the  Auditory  Apparatus  of  the  other  Animals 

Comparison  of  the  Auditory  Apparatus  of  Man  with  that  of  Animals 


PAGE 

948 
949 
949 
950 
950 
951 

951 
951 
951 
952 
953 
953 
955 
955 
956 
957 
957 
957 
958 
958 
958 
958 
958 
958 


BOOK  VIII. 

GENERATIVE   APPARATUS. 

Chapter  I.— Genital  Organs  of  the  Male 

Tiie  Testicles,  or  Secretory  Organs  of  the  Semen    . 

1.  The  Tunica  Vaginalis     .  . 

2.  The  Testicles  .  .  .'.*.*." 
Excretory  Apparatus  of  the  Semen      . 

1.  The  Epididymis  and  Deferent  Canal.  ..'.*. 

2.  The  Vesiculse  Seminales  and  Ejaculatory  Ducts 

3.  The  Urethra  .  .  .  •.".*." 

4.  The  Glands  annexed  to  the  Urethra         .'.'.'.* 

5.  The  Corpus  Cavernosum         .  . 

6.  The  Penis 

Diiferential  Characters  in  the  Male  Genital  Organs  of  the  otlier  Animals  . 
Comparison  of  the  Genital  Organs  of  Man  with  those  of  Animals 
Chapter  II.— Genital  Organs  of  the  Female 
1    The  Ovaries  .... 

2.  The  Fallopian  or  Uterine  Tubes,  or  Oviducts 

3.  The  Uterus  ....  ... 

4.  The  Vagina       .  •  .  . 

5.  The  Vulva  .  .  .'.'.*.' 

6.  The  Mammae 

Differential  Characters  in  tlie  Female  Genital  Organs  of  the  othpr  Animals     . 
Comparison  of  the  Genital  Organs  of  Woman  with  those  of  Domesticated  Female 
Animals 
Chapter  III.— Generative  Apparatus  of  Birds         ...      * 

1.  Male  Generative  Organs  ...... 

2.  Female  Generative  Organs  ..... 


960 
960 
963 
967 
967 
968 
970 
973 
973 
975 
976 


984 


993 
995 
997 
999 

1002 
1003 
1003 
1004 


UTi 


TABLE  OF  CONTENTS. 


BOOK    IX. 


EMBRYOLOGY. 

Chapter  I.  -The  Ovum  and  its  Sarly  Embryonic  Developments 

Article  I.— The  Ovum  ...... 

Article  II. — First  Embryonic  Developments     .... 

Article  III. — General  Direction  of  Development.— Vertebral  Type 
Chapter  II.— The  Foetal  Envelopes  of  Solipeds 

1.  The  Chorion      ...... 

2.  The  Amniou  ..... 

3.  The  Allantois    ....... 

4.  The  Umbilical  Vesicle         .  .  ... 

5.  The  Placenta    ....... 

6.  The  ITmbilical  Cord  ...  .  . 
Differential  Cliaracters  in  the  Annexes  of  the  Foetus  of  the  other  Animals 

Comparison  of  the  Annexes  of  the  Human  Foetus  with  those  of  Animals 
Chapter  III.— Development  of  the  Foetus 
Article  I.— Formation  of  the  Embryo  ..... 

Development  of  the  Chorda  Dorsalis  and  Vertebral  Laminae 
Article  II. — Development  of  the  Various  Organs  in  the  Animal  Economy 

Development  of  the  Nervous  System. 

Development  of  the  Organs  of  Sense 

Development  of  the  Locomotory  Apparatus  . 

Development  of  the  Circulatory  Apparatus 

Development  of  the  Respiratory  Apparatus  . 

Development  of  the  Digestive  Apparatus 

Development  ot  the  Genito-urinary  Apparatus 


PAGR 

1005 
1005 
1005 
1011 
1016 
1018 
1019 
1019 
1023 
1023 
1025 
1027 


1032 
1032 
1033 
1033 
1035 
1038 
1040 
1045 
1046 
1049 


TABLE   OF  ILLUSTRATIONS. 


FIG. 
1. 

2. 
3. 
4. 
5. 


Skeleton  of  the  Dog  . 

Skeleton  of  the  Cat         .  . 

Skeleton  of  the  Pig  . 

Skeleton  of  the  Rabbit    . 

Skeleton  of  the  Horse 

Skeleton  of  the  Cow 

Skeleton  of  the  Slieep 

Skeleton  of  the  Camel    . 

Vertical  section  of  bone 

Minute  structure  of  bone 

Lacunae,  or  osteoplasts  of  osseous  substance 

Cartilage  at  the  seat  of  ossification 

Elements  of  a  vertebra 

A  cervical  vertebra 

Atlas  (inferior  surface) 

The  axis  or  dentata  (lateral  view) 

Axis  and  sixth  cervical  of  the  Horse  and  Ass 

Type  of  a  dorsal  vertebra  (the  fourth)     . 

Middle  dorsal  vertebra  of  the  Horse,  viewed  from  three  typical  lines 

Dorsal  vertebra  of  the  Horse  and  Ass  (the  eleventh) . 

Lumbar  vertebra  (front  view) 

Upper  surface  of  lumbar  vertebrae     . 

Lumbar  vertebra  of  the  Horse  and  Ass   .  , 

Lumbar  vertebrae  of  the  Cat  and  Rabbit        . 

Lateral  view  of  sacrum  .... 

Horse's  head  (front  view)     .... 

Head  of  the  Cat  (posterior  aspect) 

Head  of  the  Pig  (anterior  face)  .  .  , 

Head  of  tiie  dog  (anterior  face)   . 

Ox's  head  (anterior  face)       .... 

Head  of  a  hornless  Ox     .  .  .  , 

Ram's  head  (anterior  face)    .... 

Anterior  bones  of  the  head  of  a  foetus  at  birth 

Posterior  bones  of  the  head  of  a  foetus  at  birth 

Head  of  the  Rabbit  (posterior  face) 

Head  of  the  Rabbit  (antero-lateral  face) 

Ox's  head  (posterior  lace)  .  .  ,  , 

Posterior  aspect  of  Horse's  skull 

Head  of  the  Pig  (posterior  face). 

Dog's  head  (posterior  view)  .... 

Longitudinal  and  transverse  section  of  the  Horse's  head  , 

Antero-posterior  and  vertical  section  of  the  Horse's  head 

Median  and  vertical  section  of  the  Ox's  head 

Inferior  maxilla         .  .  .  ,  , 

Head  of  the  Camel  .  ,  , 

Head  of  the  Cat         . 

Hyoid  bone 

Wormian  bones  of  the  Ox 


Chauveau    . 

PAGK 
8 

Chauveau    . 

8 

Chauveau    . 

9 

Chauveau    . 

9 

Original 

10 

Original 

10 

Chauveau    . 

11 

Chauveau    . 

12 

Carpenter    . 

16 

Carpenter    . 

17 

Carpenter    . 

17 

Carpenter    . 

20 

After  Owen  . 

25 

Original 

27 

Original 

28 

(Jriginal 

28 

Chauveau     . 

29 

Original 

32 

Chauveau    . 

33 

Chauveau     . 

34 

Original 

36 

Chauveau     . 

37 

Chauveau    . 

38 

( 'hauveau    . 

39 

Original      . 

40 

Original      . 

46 

Chauveau    . 

49 

Chauveau    . 

50 

Chauveau    . 

51 

Chauveau    . 

52 

Chauveau    . 

53 

Chauveau    . 

53 

Chauveau    . 

54 

Chauveau    . 

57 

Chauveau    . 

59 

Chauveau    ■ 

62 

Chauveau    . 

65 

Original 

66 

Chauveau    . 

67 

Chauveau    . 

68 

Chauveau    . 

72 

Chauveau    . 

72 

Chauveau    . 

74 

Chauveau    . 

76 

Chauveau    . 

77 

Chauveau    . 

78 

Cliauveau    . 

78 

Cornevin      . 

80 

TABLE  OF  ILLUSTRATIONS. 


pro. 
49. 

50. 
51. 
52. 
53. 
54. 
55. 
56. 
57. 
58. 
59. 
60. 
61. 
62. 
63. 
G4. 
65. 
66 
67. 
68. 
69. 
70. 
71. 
72. 
73. 
74. 
75. 
76. 
77. 
78. 
79. 
80. 
81. 
82. 
83. 
84. 
85. 
86. 
87. 


100. 
101. 
102. 
103. 
104. 
105. 
106. 
107. 
108. 
109. 


mb) 


Horse's  head  (anterior  face) 

Horse's  head  (posterior  face) 

Horse's  head  (lateral  face 

Ass's  head  (lateral  face) 

Crania  of  different  breeds  of  Dogs 

Front  view  of  the  human  cranium 

External  or  basilar  surface  of  human  skull    . 

The  sternum 

Typical  ribs  of  the  Horse 

Thorax  of  Man  (anterior  face) 

Scapula  of  the  Horse  (external  face) 

Scapula  of  the  Horse  (internal  face) 

Scapula  of  the  Cat  and  Rabbit 

Antero-external  view  of  right  humerus 

Posterior  view  of  right  humerus         .  . 

Humerus  of  the  Cat  and  Rabbit 

External  face  of  the  radius  and  ulna 

Forearm  bones  of  the  Ass 

Right  fore  foot  of  a  Horse     . 

Carpus  of  the  Horse  (anterior  face) 

Carpus  of  the  Horse  (posterior  face) 

Posterior  view  of  right  metacarpus 

Forearm  and  foot  of  the  Ox  (front  view) 

Lateral  view  of  the  digital  region  (outside  of  right  li 

Posterior  view  of  anterior  digital  region 

Plantar  surface  of  third  phalanx 

Navicular  bone  .... 

Anterior  limb  of  the  Pig 

Forearm  and  foot  of  the  Dog  (anterior  face) 

Human  scapula  (external  aspect) 

Right  human  humerus  (anterior  surface) 

Human  arm-bones  (front  view)  . 

Palmar  surface  of  left  human  hand  .  . 

Hand  of  Man  and  the  domestic  Mammalia,  normal  and 

The  ossa  innominata  (seen  from  helow)  . 

Pelvis  (antero-lateral  view)  . 

Pelvis  (lateral  view)        .... 

Pelvis  of  the  Horse  .... 

Pelvis  of  the  Mare  .... 

Pelvic  bones  of  the  Cat  and  Rabbit  . 

Left  femur  (anterior  view) 

Left  femur  (posterior  view)   . 

Section  of  left  femur,  showing  its  structure 

Femur  of  the  cat  and  rabbit 

Posterior  view  of  right  tibia 

Leg-bone  of  the  Mule 

Patella  of  the  Horse  (superior  and  posterior  face) 

Patella  of  the  Horse  (anterior  face)  . 

Leg-bones  of  the  Cat  and  Rabbit 

Left  hind  foot  (external  aspect) 

Tarsus  of  the  Horse         .... 

Left  hock  (front  view) 

Left  hock  (internul  aspect) 

Posterior  aspect  of  left  metatarsus     . 

Human  pelvis  (female)    .... 

Right  human  femur  (anterior  aspect) 

Human  tibia  and  fibula  of  right  leg  (anterior  aspect) 

Dorsal  surface  of  left  human  foot 

Anterior  limb  of  the  Horse  (antero-external  view) 

Posterior  limb  of  the  Horse  (antero-external  view) 

Skeleton  of  a  Fowl  .... 


Original 

PAGE 

81 

.            Original 

81 

Chauveau    . 

84 

.              .            Chauveau    . 

85 

.     Chauveau    . 

89 

Wilson 

90 

.      Wilson 

91 

Chauveau    . 

93 

,              .     Chauveau    . 

94 

Wilmn 

97 

.     Chauveau    . 

99 

Chauveau    . 

99 

.      Chauveau    . 

100 

,             .            Original 

101 

.             .     Original 

102 

Chauveau    . 

103 

.     Original 

104 

,                          Chauveau 

106 

.     Original 

108 

Chauveau 

109 

,             .     Chauveau    . 

109 

Original 

111 

e     Chauveau 

113 

)              .            Original 

114 

.     Original 

114 

.             .            Original 

116 

G             .     Original 

117 

Chauveau 

118 

Chauveau 

118 

Wilson 

119 

.      Wilson 

120 

Wilson 

120 

Wilson 

121 

teratological      Chauveau 

122 

Chauveau 

127 

.     Original 

129 

Original 

129 

.     Chauveau 

132 

.             .            Chauveau 

133 

.     Chauveau 

136 

Original 

138 

Original 

138 

m             .            Original 

139 

Chauveau 

140 

Original 

141 

.     Chauveau 

142 

Chauveau 

143 

Chauveau 

143 

Chauveau 

144 

.     Original 

145 

Chauveau 

146 

.     Original 

147 

Original 

147 

.             .     Original 

149 

Wilson 

151 

.      Wilson 

152 

Wilson 

152 

.      Wilson 

152 

Chauveau 

155 

Chauveau 

156 

Chauveau 

159 

TABLE  OF  ILLUSTRATIONS. 


FIG. 

110.  Head  of  a  Fowl  (natural  size  :  posterior  view) 

111.  Sternum  and  bones  of  the  wing  . 

112.  Thoracic  or  pectoral  vertebra  of  a  Mammal    • 

113.  Caudal  vertebra  of  the  Turbot     . 

114.  Cephalic  vertebrae  of  the  Dog  ..... 

115.  Plans  of  the  different  classes  of  articulations       .  .        Beaunis 

116.  Section  of  branchial  cartilage  of  Tadpole       .... 

117.  Fibro-cartilage    ..... 

118.  White  or  non-elastic  fibrous  tissue     . 

119.  Yellow  or  elastic  fibrous  tissue    . 

120.  Cervical  ligament  and  deep  muscles  of  the  Horse's  neck 

121.  Intervertebral  articulations 

122.  Cervical  ligament  of  the  Ox  ... 

123.  Cervical  ligament  of  the  young  Camel     . 

124.  Atlo-axoid  and  occipito-atloid  articulations   . 

125.  Temporo-maxillary  articulation  . 

126.  Articulations  of  the  ribs  with  the  vertebrae  (upper  plane) 

127.  Articulations  of  the  ribs  with  the  vertebrae  (inferior  plane) 

128.  Scapulo-liumeral  and  humeroradial  articulations  (external  face) 

129.  Carpal  articulations  (front  view)  .... 

130.  Lateral  view  of  the  carpal  articulations  .  .  .  . 

131.  Details  of  the  metacarpo-phalangeal  articulation  of  the  Horse     . 

132.  Carpal,  metacarpal,  and  inter-phalangeal  articulations  of  the  Horse  . 

133.  Section  of  inferior  row  of  carpal  bones,  and  metacarpal  and  suspensory 

ligament    ........ 

134.  Posterior  view  of  metacarpo-phalangeal  and  interphalangeal  articu- 

lations ....... 

135.  Metatarso-phalangeal  and  interphalangeal  articulations  of  the  Horse 

136.  Articulation  of  the  foot  (inferior  face)  .... 

137.  Longitudinal  and  vertical  section  of  the  digital  region  of  the  Horse 

138.  Tendons  and  ligaments  of  the  posterior  face  of  the  digital  region  of 

the  Ox 

139.  Sacro-iliac  and  coxo-femoral  articulations      .... 

140.  Sacroiliac  and  coxo-femoral  articulations 

141.  Femoro-tibial  articulation      ...... 

142.  Ligaments  attaching  the  three  bones  of  the  leg  . 

143.  Tarsal  articulations  (front  view)         ..... 

144.  Articulations  of  the  tarsus  (lateral  view) 

145.  Ultimate  fibril  of  muscle        ...... 

146.  Striated  muscular-tissue  fibre      ..... 

147.  Primitive  fibre  of  red  muscle  ..... 

148.  Torn  muscular  fibre         ...... 

149.  Primitive  muscular  fibre       ...... 

150.  Relation  of  primitive  muscular  fibres  with  tendon 

151.  Transverse  section  of  frozen  muscle  .  .  .  *  . 

152.  Arrangement  of  the  fibres  of  a  muscle     .  .  .        Beaunis 

1 53.  Distribution  of  capillaries  in  muscle  ..... 

154.  Portion  of  elementary  muscular  fibre       .... 

155.  Striated  fibre  of  muscle  during  contraction     .... 

156.  Horse  fixed  in  first  position  ..... 

157.  Horse  fixed  in  second  position  ..... 

158.  Lateral  view  of  the  neck  (superficial  muscles)     . 

159.  Superficial  muscles  of  the  neck  and  spinal  region  of  the  back  and  loins 

160.  Lateral  view  of  the  neck  (middle  layer  of  muscles)   . 

161.  Cervical  ligament  and  deep  muscles  of  the  neck  . 

162.  Muscles  of  the  spinal  region  of  the  neck,  back,  and  loins 

163.  Deep  ditto  ....... 

164.  Muscles  of  the  back  and  cervix  of  Man  .... 

165.  Muscles  of  the  sublumbar,  patellar,  and  internal  crural  regions  . 

166.  Deep  muscles  of  the  sublumbar  region  .... 

167.  Sacro-iliac  and  coxo-femoral  muscles       .... 


Chauveau    . 

PAGh 

160 

Chauveau    . 

164 

Chauveau    . 

168 

Chauveau    . 

168 

Lavocat 

168 

and  Bouchard 

171 

Carpenter    . 

172 

Wilson 

173 

Carpenter    . 

174 

Carpenter    . 

174 

Chauveau    . 

181 

Chauveau    . 

182 

Chauveau    . 

184 

Chauveau    . 

185 

Chauveau    . 

187 

Chauveau    . 

188 

Chauveau    . 

191 

Chauveau    . 

191 

Chauveau    . 

196 

Chauveau    . 

201 

Chauveau    . 

202 

Chauveau    . 

204 

Chauveau    . 

205 

Chauveau    . 

207 

Original      . 

208 

Chauveau     . 

210 

Chauveau    . 

210 

Chauveau    . 

211 

Chauveau    . 

211 

Chauveau    . 

213 

Chauveau    . 

214 

Chauveau    . 

217 

Chauveau    . 

220 

Chauveau    . 

222 

Chauveau     . 

224 

Bowman 

232 

Bowman 

232 

Renaut 

233 

Renaut 

233 

Renaut 

234 

Renaut 

234 

Kiihne 

235 

and  Bouchard 

236 

Berres 

236 

Beale 

237 

Bowman 

237 

Chaiiveau     . 

240 

Chauveau     . 

241 

Original      . 

245 

Chauveau    . 

247 

Original      . 

248 

Chauveau    . 

251 

Chauveau    , 

261 

Chauveau    . 

264 

Wilson 

267 

Chauveau    . 

270 

Chauveau    . 

271 

Chauveau    . 

273 

TABLE  OF  ILLUSTRATIONS. 


168.  Superficial  muscles  of  the  face  and  head        .... 

169.  Muscles  of  external  ear  of  Mule  . 

170.  Muscles  of  the  ear     ....... 

171.  Hyoideal  and  pharyngeal  regions  .... 

172.  Superficial  muscles  of  the  Ox's  head  .... 

173.  Muscles  of  the  human  head         .  .  .  . 

174.  Muscles  of  the  axillary  and  cervical  regions  .... 

175.  Axillary  und  thoracic  muscles     ..... 

176.  Muscles  of  the  inferior  abdominal  region  (Ass) 

177.  Muscles  of  the  anterior  aspect  of  the  body  of  Man 

178.  Diaphragm  (posterior  face)    ...... 

179.  External  muscles  of  the  anterior  limb      .... 

180.  Muscles  of  anterior  aspect  of  Man's  upper  arm 

181.  Internal  aspect  of  left  anterior  limb         .... 

182.  Deep  muscles  on  external  aspect  of  right  anterior  limb  , 

183.  Tendons  and  burtse  of  anterior  limb  of  Horse 

184.  Flexor  tendons  of  phalanges  of  Horse  .... 

185.  Muscles  of  the  forearm  of  the  Ox  ...  . 

186.  Tendinous  and  ligamentous  apparatus  in  the  digital  region  of  the  Ox 

187.  Anterior  antibrachial  region  of  the  Pig 

188.  Muscles  of  the  forearm  and  paw  of  the  Dog 

189.  Superficial  muscles  of  human  forearm  .... 

190.  Deep  layer  of  superficial  muscles  of  human  forearm 

191.  Muscles  of  human  hand  =  .  .  .  . 

192.  Dissecting- table  ....... 

193.  Superficial  muscles  of  the  croup  and  thigh   .  . 

194.  Superficial  muscles  of  the  croup  and  thigh 

195.  Muscles  of  the  sublumbar,  patellar,  and  internal  crural  regions 

196.  Deep  muscles  of  the  coxo-femoral  region 

197.  Coccygeal  and  deep  muscles  surrounding  the  coxo-femoral  articu- 

lation        ...... 

198.  Superficial  muscles  of  the  croup  and  thigh  in  the  Cow 

199.  Muscles  of  the  anterior  femoral  region  in  Man 

200.  Muscles  of  the  posterior  femoral  and  gluteal  region  in  Man 

201.  External  deep  muscles  of  right  posterior  limb 

202.  Flexor  muscle  of  metatarsus 

203.  Muscles  on  inner  aspect  of  left  posterior  limb 

204.  Articular  capsules  and  bursse  in  posterior  limb    . 

205.  External  muscles  of  the  leg  of  the  Ox 

206.  Muscles  of  the  human  leg  (anterior  tibial  region) 

207.  Superficial  posterior  muscles  of  the  human  leg 

208.  First  layer  of  plantar  muscles  of  human  foot 

209.  Third  and  part  of  second  layer  of  plantar  muscles  of  human  foot 

210.  Squamous  epithelium  from  the  mouth     .... 

211.  Columnar  epithelium       .  .  ... 

2 1 2.  Columnar  ciliated  epithelium  .... 

213.  Conical  villi  on  mucous  membrane  of  small  intestine 

214.  Fusiform  cells  of  smooth  muscular  fibre  .  . 

215.  Hard  and  soft  palate  ..... 

216.  Composite  papilla  from  tongue  of  Dog     .  .  .  , 

217.  Simple  filiform  papillae  ..... 

218.  Foramen  of  Morgagni      ...... 

219.  Vertical  section  of  a  foramen  csecum 

220.  Muscles  of  the  tongue,  soft  palate,  and  pharynx  . 

221.  Lobe  of  racemose  gland  from  the  floor  of  the  mouth 
222    Follicular  gland  ....... 

223.  Section  of  an  amysdaloid  follicle       .... 

224.  Median  longitudinal  section  of  the  head  and  upper  part  of  neck 

225.  Magnified  section  of  a  canine  tooth ..... 

226.  Section  through  the  fang  of  a  molar  tooth      .  , 

227.  Transverse  section  of  enamel       .  .  .  .  c 


Original 
Cliauveau 

275 

280 

Original 
Original 
Chauveau 

282 
287 
290 

Wilson 

291 

Chauveau 

294 

Original 
Chauveau 

295 
304 

Wilson 

306 

Chauveau 

309 

Chauveau 

311 

Wilson 

317 

Original 
Original 
Chauveau 

318 
321 
329 

Chauveau 

331 

Chauveau 

333 

Chauveau 

334 

Chauveau    . 

335 

Chauveau 

337 

Wilson 

339 

Wilson 

339 

Wilson 

342 

Chauveau 

344 

Chauveau 

345 

Original 
Chauveau 

347 
354 

Chauveau 

356 

Chauveau 

358 

Chauveau 

359 

Wilson 

361 

Wilson 

361 

Original 
Chauveau 

363 
365 

Original 
Chauveau 

367 
370 

Chauveau 

372 

Wilson 

375 

Wilson 

375 

Wilson 

377 

Wilson 

377 

Wilson 

393 

Kolliker 

393 

Carpenter 
Wilson 

393 
394 

Bowman 

395 

Chauveau 

399 

Chauveau 

402 

Chauveau 

402 

Chauveau 

403 

Chauveau 

403 

Chauveau 

405 

KSlliker 

406 

KdlUker 

406 

Chauveau 

407 

Original 
Wilson 

4f)9 
412 

Carpenter 
Carpenter 

413 
414 

TABLE  OF  ILLUSTRATIONS. 


zxxi 


FIG.  ''■*<5E 

228.  Theoretical  section  of  dental  sac  of  permanent  incisor                          .  Chauveau  .  415 

229.  Section  of  dentine  and  pulp  of  an  incisor  tooth    .             .             .  Carpenter  ,  416 

230.  Dentition  of  inferior  jaw  of  Horse       .....  Chauveau  .  418 

231 .  Section  of  incisor  tooth  of  Horse                ....  Chauveau  .  418 

232.  Incisor  teeth  of  Horse  (details  of  structure)  ....  Chauveau  .  419 

233.  Profile  of  upper  teeth  of  the  Horse           ....  Chauveau  .  421 

234.  Transverse  section  of  Horse's  upper  molar      ....  Chauveau  .  422 

235.  The  teeth  of  the  Ox         .             .             .             .                          .  Chauveau  .  425 

236.  Ox's  incisor  tooth      .......  Chauveau  .  425 

237.  Incisor  teeth  of  a  Sheep  two  years  old     .             .             .             .  Chauveau  .  427 

238.  Teeth  of  the  Pig        ...                           ...  Chauveau  .  428 

239.  General  and  lateral  view  of  the  Dog's  teeth          .             .             .  Chauveau  .  429 

240.  Anterior  view  of  the  incisors  and  canine  teeth  of  Dog            .             .  Chauveau  .  429 

241.  Lateral  and  general  view  of  the  Cat's  teeth         .             .             .  Chauveau  .  429 

242.  Dentition  of  the  Rabbit         .....  Chauveau  .  430 

243.  Section  of  the  human  face            .....  Quain  .  432 

244.  Lobule  of  parotid  gland         ...                          .             .  Wagner  .  434 

245.  Capillary  network  of  follicles  of  pirotiil  gland     .              .             .  Berres  .  434 

246.  Termination  of  the  nerves  in  the  salivary  glands       .             .             .  Pfliiger  .  435 

247.  Inferior  aspect  of  head  and  neck              ....  Origincd  .  436 

248.  Maxillary  and  sublingual  glands        .....  Chauveau  .  437 

249.  Pharyngeal  and  laryngeal  region              ....  Original  .  441 

250.  Median  lengitudinal  section  of  head  and  upper  part  of  neck               .  Original  .  442 

251.  Pharynx  of  the  Horse  (posterior  view)     ....  Chauveau  .  443 

252.  Muscles  of  the  pharyngeal  and  hyoideal  regions        .             -             .  Original  .  445 

253.  Human  pharynx              ......  Wilson  .  447 

254.  Transverse  vertical  section  of  head  and  neck              .                          .  Original  .  448 

255.  Pectoral  cavity  and  mediastinum              ....  Chauveau  .  449 

256.  Theoretical  transverse  section  of  abdominal  cavity    .             .             .  Chauveau  .  452 

257.  Theoretical,  longitudinal,  and  median  section  of  abdominal  cavity  Chauveau  .  453 

258.  The  abdominal  cavity,  with  the  stomach  and  other  organs    .             .  Origiiuil  .  456 

259.  Stomach  of  the  Horse      ......  Chauveau  .  457 

260.  Interior  of  the  Horse's  stomach          .....  Chauveau  .  458 

261.  Muscular  fibres  of  stomach  (external  and  middle  layers)              .  Chauveau  .  460 

262.  Deep  and  middle  muscular  fibres  of  stomach              .             .             .  Chauveau  .  460 

263.  Peptic  gastric  gland        ......  KoUiker  .  461 

264   Portion  of  a  peptic  caecum    ......  Kolliher  .  461 

265.  Mucous  gastric  gland      ...                            .             .  KoUiker  .  462 

266.  Capillaries  of  mucous  membrane  of  stomach              .             .             .  Carpenter  .  462 

267.  Stomach  of  the  Dog         ...                           .             .  Chauveau  .  463 

268.  Stomach  of  the  Ox    .              .              .                                         .              .  Chauveau  .  464 

269.  Interior  of  the  stomacli  of  Ruminants      .                          .             ,  Chauveau  .  465 

270.  Section  of  the  wall  of  the  omasum  of  Sheep  o             .             ,             ,  Chauveau  .  467 

271.  Stomach  of  the  Sheep      ......  Chauveau  .  468 

272.  Section  of  the  omasum  of  the  Sheep               ....  Chauveau  .  469 

273.  Section  of  a  leaf  of  the  omasum  .....  Chauveau  ,  470 

274.  Longitudinal  section  of  a  large  papilla  from  the  omasum      .             .  Chauveau  .  470 

275.  Villi  of  human  and  Sheep's  intestine      ....  Teichmann  .  474 

276.  Portion  of  Brunner's  gland  -...,.  Thomson  .  474 

277.  Section  through  Peyer's  patch  of  Sheep .                          .             .  Teichmann  .  475 

278.  Section  through  solitary  follicle          .             .             .             .              .  Teichmann  .  476 

279.  Injected  villi  of  intestine              .....  KoUiker  .  476 

280.  Blood-vessels  in  Peyerian  glandulse  .....  KoUiker  .  477 

281.  Diagram  of  origin  of  lacteals  in  villi        ....  Funke  .  477 

282.  General  view  of  the  intestines  of  the  Horse  (right  side)         .             .  Chauveau  .  479 

283.  General  view  of  the  Horse's  intestines  (inferior  aspect)   »             .  Chauveau  .  480 

284.  The  colon  of  the  Horse          ......  Original  ..  481 

285.  Plan  of  the  colon              ......  Chauveau  .  482 

286.  Intestines  of  the  Rabbit  (sreneral  view)          •             c              .             .  Cliauveau  .  486 

287.  Stomach  and  intestines  of  the  Sheep        ....  Chauveau  .  487 

288.  General  view  of  the  intestines  of  the  Ox       .                          ,             .  Chauveau  .  488 


TABLE  OF  ILLUSTRATIONS. 


FIG. 

289. 
290. 
291. 
292. 
293. 
294. 
295. 
296. 
297. 
298. 
299. 
300. 
3(Jl. 
302. 
303. 
304. 
305. 
306. 
307. 
308. 
3ii9. 
310. 
311. 
312 
313. 
314. 
315. 
316. 
317. 
318. 
319. 
320. 
321. 
322. 
323. 
324. 
325. 
326. 
327. 


331. 
332. 


334. 
335. 


339. 
340. 
341. 
342. 
343. 
344. 
345. 
346. 
347. 
348. 
349. 


General  view  of  the  intestines  of  the  Pig             .             .             .  Chauveau    . 

Intestines  of  the  Dog             ......  Chauveau    . 

Digestive  apparatus  of  the  Cat  .....  Chauveau    . 

Human  intestines      .......  Wilson 

Abdominal  cavity,  with  the  liver  and  other  organs           .             .  Original 

Portion  of  a  hepatic  column,  with  secreting  cells       .             .             .  Leidy 
Biliary  capillaries  and  ducts       .....  Irminrjer  and  Frey 

Blood-vessels  in  lobules  of  liver         .....  Kiernan 

Section  of  lobules  of  liver,  witli  intra-lobular  veins           .             .  Kiernan 

Excretory  apparatus  of  the  Horse's  liver        ....  Chauveau    . 

Structure  of  the  spleen  (diagrammatic)   .             .             .        Beaunis  and  Bouchard 

Malpighian  corpuscles  attached  to  splenic  artery       .             .             .  KSlliker 

Splenic  corpuscle  from  the  spleen  of  Ox  .             .             .             .  Kdlliker 

Liver  of  the  Ox         ......             .  Cliauveau     . 

Liver  of  the  Dog,  with  its  excretory  apparatus    .             .             .  Chauveau    . 

Under  surface  of  the  human  liver      ....  Wilson 

General  view  of  the  digestive  apparatus  of  a  Fowl           .             .  Chauveau    . 

Cartilages  of  the  nostrils        ......  Chauveau    . 

Transverse  section  of  the  head  of  a  Horse            .             .             .  Chauveau    . 

Longitudinal  section  of  the  head  and  upper  part  of  neck      .             .  Original 
Cells  of  the  olfactory  mucous  membrane              .             .              Clarke  and  Schultze 

Fibres  of  olfactory  nerve       ......  Ecker 

Cartilages  of  the  larynx  disarticulated    ....  Chauveau    . 

Superior  face  of  larynx           ......  Chauveau    . 

Inferior  face  of  larynx     ......  Chauveau    . 

Muscles  of  tlie  Horse's  larynx            .....  Chauveau    . 

Postero-lateral  view  of  larynx      .....  Original 

Entrance  to  the  larynx  of  the  Horse               ....  Chauveau    . 

The  respiratory  organs  (inferior  aspect)  ....  Original 

Trachea,  bronchi,  and  lungs  of  the  Horse      ....  Chauveau    . 

Ciliated  epithelium  from  the  trachea       ....  Kdlliker 

Bronchial  tube,  with  its  bronchules   .....  Heale 

Mucous  membrane  of  a  broncliial  tube     ....  Heale 

Theoretical  section  of  thoracic  cavity,  behind  the  heart         .             .  Chauveau    . 

Theoretical  section  of  thoracic  cavity,  at  root  of  lungs    .             .  Chauveau    . 

Theoretical  section  of  thoracic  cavity,  in  front  of  right  ventricle         .  Chauveau    . 

Lungs  of  the  Horse         ......  Chauveau    . 

Lungs  of  the  Horse  .......  Chauveau    . 

Cast  of  bronchiole            ......  Chauveau    . 

Cast  of  bronchial  divisions     ......  Chauveau    . 

Plan  of  a  pulmonary  lobule          .             .                          ,             .  Waters 

Infundibula  of  lung  .......  Kdlliker 

Capillaries  around  the  infundibula  of  lung           .             .              .  Carpenter    . 

Lung  of  the  Sheep  (inferior  view)     .....  Chauveau    . 

Human  lungs  and  heart  ......  Wilson 

Gland-vesicles  of  thyroid       .....  Kdlliker 

Portion  of  thymus  of  Calf            .....  Kdlliker 

Course  and  termination  of  ducts  in  thymus  gland  of  Calf      .             .  Wilson 

General  view  of  the  air-sacs  in  the  Duck              .             .             ,  Chauveau    . 

General  view  of  the  genito-uriuary  apparatus  in  the  Horse  .             .  Chauveau    . 

Horizontal  longitudinal  section  of  the  Horse's  kidney      .  Chauveau     . 

Section  of  the  cortical  substance  of  the  kidney           .             .             .  Ecker 

Course  of  the  uriniferous  tubuli  .....  Hertz 

Diagram  of  the  circulation  in  the  kidney 
Transverse  horizontal  section  of  kidney   . 
The  kidneys  and  bladder  in  the  foetus  of  Solipeds 
Right  kidney  of  Ox  (upper  and  external  face)    . 
Left  kidney  of  Ox  (internal  and  inferior  face) 
The  calices  in  left  kidney  of  Ox 
Theoretical  plan  of  the  circulatory  system     . 
The  heart  and  principal  vessels  (left  face) 


Original 

Chauveau 

Chauveau 

Chauveau 

Chauveau 

Colin 


PAGE 

489 
490 
491 
492 
496 
498 
498 
499 
499 
500 
504 
505 
505 
508 
509 
510 
513 
519 
520 
521 
523 
524 
.'i28 
531 
531 
532 
533 
535 
537 
538 
539 
540 
541 
545 
545 
545 
546 
548 
549 
550 
551 
551 
551 
553 
.')53 
554 
556 
556 
564 
569 
371 
572 
573 
573 
574 
577 
580 
580 
680 
582 
585 


TABLE  OF  ILLUSTRATIONS. 


FIG. 

350. 
351. 
352. 
353. 
354. 
855. 
356. 
357. 
358. 
359. 
360. 
361. 
362. 
363. 
364. 
365. 
366. 
367. 


370. 
371. 
372. 
373. 
374. 
375. 
376. 
377. 
378. 
379. 
380. 
381. 


385. 


387. 


391. 
392. 


395. 
396. 
397. 


400. 
401. 
402. 
403. 
404. 
405. 
406. 
407. 
408. 


The  heart  and  principal  vessels  (right  face)        .  .  .  Chauveau 

Right  side  of  the  heart  laid  open       .....  Wilson 

Section  of  the  heart  at  the  level  of  the  valves       .  .  .  Sibson 

Left  cavities  of  the  heart  laid  open  .....  Wilson 

Auriculo-ventricular  fibro-cartilaginous  rings      .  .  .  Parchappe 

Anastomosing  muscular  fibres  of  heart  ....  KoUiker 

Muscular  whorl  at  point  of  heart  ....  Bourgery 

Posterior  unitive  fibres  of  auricles     .....  Bourgery 

Epithelium  of  the  endocardium  .....  KoUiker 

Human  lungs  and  heart  (front  view)  ....  WiUon 

Web  of  Frog's  foot,  showing  blood-vessels  and  their  anastomoses  Wagner 

Epithelial  cells  of  blood-vessels  .....  KoUiker 

Fenestrated  membrane  from  the  carotid  artery  of  the  Horse  .  KoUiker 

Coarse  elastic  tissue  from  pulmonary  artery  of  the  Horse  .  KoUiker 

Transition  of  a  minute  artery  of  the  brain  into  capillary  vessels         .  KoUiker 

Abdominal  or  posterior  aorta  and  cceliac  axis  in  the  Horse  .  Chauveau 

Distribution  of  the  small  mesenteric  artery   ....  Chauveau 

Arteries  of  the  stomach  of  Ruminants     ....  Chauveau 

Lateral  view  of  ttie  genito-urinary  organs  in  the  male  .  .  Chauveau 

Abdominal  aorta,  with  its  branches,  in  Man        .  .  .  Wilson 

The  external  and  internal  iliac  arteries  in  the  Mare  .  .  Chauveau 

Principal  arteries  of  posterior  foot  of  Horse  .  .  .  Cliauveau 

Anterior  aspect  of  human  leg  and  foot  ....  Wilson 

Posterior  aspect  of  human  leg      .  .  .  .  .  Wilson 

Arteries  of  sole  of  human  foot  .....  WiUmi 

Distributiou  of  the  anterior  aorta  ....  Chauveau 

Terminations  of  the  axillary  artery  in  the  Horse       ,  .  .  Chauveau 

Arteries  of  the  anterior  foot  (seen  from  behind)  .  .  Chauveau 

Arteries  of  the  anterior  foot  of  the  Horse       ....  Chauveau 

Arteries  of  the  human  forearm  and  hand  .  .  .  Wilson 

Arteries  of  the  brain  ......  Chauveau 

Arteries  of  the  head        ......  Chauveau 

Rete  mirabile  of  the  Sheep  (seen  in  profile)  ....  Chauveau 

Rete  mirabile  of  the  Ox  (posterior  face)  ....  Cliauveau 

Arteries  of  the  face  and  head  of  Man  ....  Heath 

Radicles  and  collateral  branches  of  the  jugular  vein  in  the  Horse  Chauveau 
Sinuses  of  the  dura  mater  and  radicles  of  the  jugular  vein  of  tiie 

Horse         ........  Chauveau 

Subsphenoidal  confluents  in  the  Horse  ....  Cliauveau 

Veins  of  the  foot        .......  Bouley 

General  view  of  the  veins  in  the  Horse   ....  Chauveau 

Vena  portae  and  its  roots       ......  Chauveau 

A  lymphatic  vessel  with  its  valves  ....  Chauveau 

Section  of  a  lymphatic  rete  mirabile  ....  Teichmann 

Section  of  lymphatic  gland  .....  KoUiker 

Section  of  simple  lymphatic  gland     .....  Teichmann 

Section  of  the  medullary  substance  of  lymphatic  glaud  of  Ox      .  KoUiker 

Ordinary  disposition  of  the  thoracic  duct       ....  Colin 

Double  variety  of  the  thoracic  duct  ....  Colin 

Triple  variety  of  the  thoracic  duct     .....  Colin 

Lymphatic  system  of  the  Horse  .....  Colin 

Great  lymphatic  vein  and  entrance  of  the  thoracic  duct         .  .  Colin 

Great  lymphatic  duct  (another  variety)  ....  Colin 

Thoracic  duct  in  the  Ox        .  .  .  .  .  .  Colin 

A  variety  of  the  thoracic  duct  in  the  Ox  .  .  .  Colin 

Another  variety  of  the  thoracic  duct  .  .  .  .  Colin 

A  fourth  variety  of  the  thoracic  duct       ....  Colin 

Thoracic  duct  of  small  Ruminants    .....  Colin 

Diagram  of  structure  of  nerve-fibre  ....  Carpenter 

Nerve-tube   .......  Ranvier 

Multipolar  or  stellate  nerve-cell  ....  Ecker 


PAGE 

586 
587 
589 
591 
592 
594 
594 
595 
597 
599 
603 
604 
604 
604 
605 
614 
619 
622 
627 
628 
630 
637 
642 
642 
643 
647 
651 
653 
655 


678 
680 
681 


695 
700 
704 
707 
714 
717 
718 
718 
719 
723 
723 
723 
725 
731 
731 
732 
733 
733 
733 
7:-<4 
740 
740 
741 


TABLE  OF  ILLVSTBATIONS. 


410.  Several  multipolar  nerve-cells 

411.  Pyriimidal  cell  of  the  grey  substance 

412.  Ganglion  from  heart  of  Frog 

413.  Bipolar  ganglionic  cells  and  nerve' 

414.  Stellate  nerve-cell     .  «  .  . 

415.  Structure  of  ganglionic  cells        .... 

416.  General  view  of  tlie  spinal  cord         ... 

417.  Spinal  cord  at  the  cervical  bulb  or  brachial  plexus 

418.  Section  of  the  spinal  cord  of  the  Horse  at  the  lumbar  region 

419.  Transverse  section  of  spinal  cord  in  the  lumbar  region     . 

420.  Transverse  section  of  spinal  cord  of  Man  in  the  middle  of  the  lumbar 

region         ...... 

421.  Ganglionic  cell  from  the  inferior  cornu  of  spinal  cord 

422.  Longitudinal  secti>m  through  cervical  bulb  of  spinal  cord  of  the  Cat 

423.  Brain  of  tlie  Horse  (upper  surface)   . 

424.  General  view  of  the  brain  (lower  surface) 

425.  Superior  view  of  the  encephalic  isthmus 

426.  Lateral  view  of  the  isthmus         .... 

427.  Transverse  section  of  the  brain  .  .  • 

428.  Dissection  of  the  medulla  oblongata        .  . 

429.  Median  and  vertical  section  of  the  brain 

430.  Layers  and  cells  of  grey  matter  of  cerebellum     .  . 

431.  Section  of  the  cortical  substance  of  the  cerebellum    . 

432.  Antero-posterior  and  vertical  section  of  the  brain  . 

433.  Brain  of  the  Horse  (lateral  face) 

434.  Corpus  callosum  .  .  .  .  , 

435.  Anterior  portion  of  the  lateral  ventricles 
436;  Transverse  section  of  human  brain 

437.  Course  of  association  nerve-fibres      .  .  . 

438.  Course  of  association  fibres  in  corpus  callosum     .  • 

439.  Course  of  radiating  fibres  in  the  corona  radlata 

440.  Layers  and  cells  of  a  frontal  convolution  ,  . 

441.  Corticle  substance;  of  the  cerebral  hemispheres 

442.  Brain  of  the  Ox  . 

443.  Brain  of  the  Slieep    ..... 

444.  Brain  of  the  Pig  ..... 

445.  Lateral  face  of  the  Dog's  brain 

446.  Brain  of  the  Dog  (upper  face)  ... 

447.  Brain  of  the  Cat       ...  . 

448.  Base  of  the  human  brain  .... 

449.  Muscular  fibres,  with  termination  of  motor  nerve      . 

450.  Nerves  of  the  eye  ..... 

451.  Section  of  the  pons  Varolii  .... 

452.  Lateral  view  of  the  medulla  oblongata    . 

453.  General  view  of  the  superior  and  inferior  maxillary  nerves 

454.  Section  of  medulla  oblongata  and  pons  Varolii  . 

455.  Section  of  middle  portion  of  medulla  oblongata 

456.  Origin  of  the  nerves  arising  from  the  medulla  oblongata 

457.  Origin  and  distribution  of  the  eighth  pair  of  nerves  in  Man 

458.  Distribution  of  the  nerves  in  the  larynx  of  the  Horse 

459.  Deep  nerves  of  the  head        .... 

460.  Nerves  of  the  guttural  region  in  the  Ox. 

461.  Innervation  of  submaxillary  and  sublingual  glands  . 

462.  Nerves  of  the  face  and  scalp  of  Man 

463.  Distribution  of  eighth  pair  of  nerves  on  left  side 

464.  Ganglion  of  a  spinal  nerve  from  the  lumbar  region 

465.  Nerves  of  the  brachial  plexus 

466.  External  nerves  of  anterior  limb  .  .  . 

467.  Nerves  of  the  digit  of  Horse 

468.  Nerves  of  tlie  digital  region  of  Ruminants 

469.  Nerves  of  the  palmar  face  of  Dog's  foot 


PAOB 

,             .     Chauveau    . 

741 

Chauveau    . 

741 

.     Ecker 

742 

Ecker 

742 

.     Beale 

742 

.   Beale  and  Arnold 

742 

.     Colin 

755 

Colin 

755 

.     Chauveau     . 

757 

Deiters 

758 

e  lumbar 

.     I.  L.  Clarke 

759 

Kraus^e 

760 

the  Cat    I.  L.  Clarke 

761 

.     CJiauveau    . 

764 

Chauveau    . 

766 

Chauveau    . 

770 

Chauveau    . 

773 

Cliauveau    . 

775 

Solly  and  Carpenter 

776 

.     Cliauveau    . 

780 

Duval 

781 

.     Kolliher      . 

782 

Chauveau    . 

783 

.     Cliauveau    . 

787 

Cliauveau    . 

789 

.     Chauveau    . 

789 

Edinger 

793 

.     Edinger 

794 

.            Edinger 

795 

.     Edinger 

795 

.            Cliauveau    . 

796 

.     Kolliher       . 

796 

,            Chauveau     . 

797 

,             .      Cliauveau    . 

798 

.            Chauveau    . 

799 

Chauveau    . 

800 

Chauveau     . 

801 

.     Chauveau    . 

801 

Emchfeld  and  LeveilU 

802 

,             .     Cohnheim    . 

806 

Chauveau    . 

812 

.     Duval 

814 

Erb 

815 

Chauveau    . 

818 

Duval 

825 

.     Duval 

833 

Toussaint     . 

836 

.      Wihon 

837 

Toussaint    , 

838 

Chauveau    . 

843 

Toussaint     . 

845 

Bernard 

848 

Eirschfeld  and  LeveilU 

850 

Hirschfeld  and  LeveilU 

851 

KolUker       . 

854 

.     Chauveau    . 

863 

Chauveau    . 

863 

.     Bouley 

866 

,            Cliauveau    . 

868 

.     Chauveau    . 

870 

TABLE  OF  ILLUSTRATIONS. 


FIG. 

470.  Nerves  of  the  palmar  face  of  Cat's  foot  .  ,  ,  .  Chauveau    . 

471.  Nerves  of  the  axilla  of  Man         ....       Hirschfeld  ami  LeveilU 

472.  Nerves  of  the  front  of  forearm  and  hand  of  Man         .  Hirschfeld  and  Leveill€ 

473.  Lumbo-sacral  plexus  and  internal  nerves  of  posterior  limb    .  .  Cliauveau    . 

474.  Posterior  portion  of  the  lumbo-sacral  plexus        .  .  .  Chauveau    . 

475.  External  nerves  of  posterior  limb      .....  Chauveau    . 

476.  Lumbar  plexus  of  Man  .....  Hirschfeld  and  Leveill^ 
'ill.  Nerves  at  the  posterior  aspect  of  human  leg  .  .  Hirschfeld  and  Leveill^ 
478  Nerves  at  the  front  aspect  of  human  leg               .             .        Hirschfeld  and  Leveill€ 

479.  Sympathetic  ganglion  from  a  Puppy  ....  Kolliker 

480.  Sympathetic  system  of  the  Horse  ....  Cliauveau    . 

481.  Brain  of  a  Bird  .......  Chauveau    . 

482.  Section  of  Horse's  skin    ......  Chauveau    . 

483.  Capillary  loops  in  cutaneous  papillae  ....  Berres 

484.  Tactile  papillae  from  the  skin       .....  Ecker 

485.  Interungulate  sinus  of  Sheep  .....  Owen 

486.  Branches  of  cutaneous  nerves  in  skin       ....  Ecker 

487.  Sudoriparous  gland    .......      Wagner 

488  Oblique  section  of  epidermis        .....  Carpenter    . 

489.  Hair-follicle  ......       Morel  and  Villemin 

490  Longitudinal  median  section  of  Horse's  foot         .  .  «  Original 

49L  Horizontal  section  of  Horse's  foot      .....  Original 

492.  Lower  surface  of  the  Horse's  foot  ....  Original 

493.  Lateral  view  of  the  Horse's  foot         .....  Original 

494.  Horizontal  section  of  hoof  .....  Chauveau    . 

495.  Horizontal  section  of  the  junction  of  the  wall  with  the  sole  of  hoof    .  Leisering     . 

496.  Horizontal  section  of  wall,  and  horny  and  vascular  lamiuse  .  Leisering     . 

497.  Hoof  removed  from  the  foot  ......  Leisering     . 

498.  Hoof  with  outer  portion  of  wall  removed  .  .  .  Leisering 

499.  Plantar  surface  of  hoof  ......  Leisering     . 

600.  Horn-cells  from  the  sole  of  hoof  .....  Leisering     . 

501.  Constituent  elements  of  the  wall        .....  Leisering     . 

502.  Theoretical  section  of  the  Horse's  eye     ....  Chauveau    . 

503.  Anterior  segment  of  a  transverse  section  of  the  globe  of  the  eye 

(human)    ........      Wilson 

504.  Cells  from  pigmentum  nigrum     .....  Carpenter    . 

505.  The  eye  (human)  with  the  sclerotic  coat  removed      .  .  .  Holden 

506.  Muscular  structure  of  the  iris      .....  Kolliker 

507.  Vertical  section  of  retina       ......  MUller 

508.  Diagram  of  the  structure  of  the  retina     ....  Krause 

509.  Capillaries  in  the  vascular  layer  of  the  retina  .  .  .  Berres 

510.  Muscles  of  the  eyeball  (viewed  from  above)  ,  .  .  Original 

511.  Labyrinth  in  Fishes,  Birds,  and  Mammals    ....  Gegenbaur  . 

512.  Section  of  lamina  spiralis  of  the  cochlea  .  ,  ,  Carpenter 

513.  Section  of  the  cochlea  parallel  to  its  axis       ....  Breschet 

514.  Cochlea  opened   .......  Chauveau    . 

515.  Eight  tympanic  cavity  of  Horse's  ear  ....  Chauveau 

516.  Bones  of  the  middle  ear  of  the  Horse       ....  Lavocat 

517.  Diagram  of  the  testicle  ••....  Holden 

518.  Human  testis,  injected  with  mercury       ....  Lauth 

519.  Vertical  section  of  the  Horse's  testis  ....  Chauveau 

520.  Internal  genito-urinary  organs  of  the  foetus  of  a  Mare      ,  .  Chauveau    . 

521.  Spermatozoa  of  various  animals  .....  Carpenter 

522.  Superior  view  of  the  genito-uriuary  organs  .  .  .  Chauveau 

523.  Transverse  section  of  penis    ......  Chauveau 

524.  Longitudinal  section  of  the  free  extremity  of  the  Horse's  penis  .  Chauveau 

525.  Internal  genital  organs  of  a  young  Bull         ....  Chauveau 

526.  Sections  of  the  urethra  of  the  Ox  at  different  points        .  .  Chauveau 

527.  Penis  and  muscles  of  the  sheath  of  the  Bull ....  Chauveau 

528.  Section  of  human  pelvis  ......  Gray 

629.  Section  of  the  ovary  .......  Schroen 


PAGE 

870 

871 
872 
876 
877 
879 


884 


895 
900 
900 
901 
901 
902 
902 
903 
905 
908 
909 
910 
912 
912 
914 
914 
915 
916 
916 
919 
919 
927 

931 
931 
932 
933 
935 
936 
936 
940 
948 
949 
949 
950 
953 
954 
963 
963 
964 
965 
967 
969 
974 
976 
977 
978 
979 
982 


TABLE  OF  ILLUSTRATIONS. 


FIG. 

530.  Ovaries,  oviducts,  and  uterus  of  a  foetus  (equine) 

531.  Ovarium  of  the  Rabbit         .... 

532.  Constituent  parts  of  Mammalian  ovum,  entire    . 

533.  Constituent  parts  of  Mammalian  ovum,  ruptured     . 

534.  Formation  of  the  corpus  luteum 

535.  Generative  organs  of  the  Mare,  isolated 

536.  Generative  organs  of  the  Mare,  in  situ  . 

537.  Termination  of  milk-duct  in  cluster  of  follicles 

538.  Ultimate  follicles  of  mammary  gland,  with  secreting  cells 

539.  Microscopic  appearance  of  milk 

540.  Human  uterus,  witii  its  appendages 

541.  Ovary  of  the  Bird   ..... 

542.  Graafian  vesicle  ..... 

543.  Optical  section  of  ovum  of  Eabbit   . 

544.  Ovum  of  Rabbit  ..... 

545.  Blastodermic  vesicle  of  Rabbit 

546.  Section  of  a  Fowl's  unhatched  egg 

547.  Area  pellucida  in  early  blastoderm 

548.  Transverse  section  of  blastoderm 

549.  Area  pellucida  of  blastoderm 

550.  Area  pellucida  in  blastoderm     .... 

551.  Transverse  section  of  blastoderm 

552.  Transverse  section  of  dorsal  region 

553.  Manner  in  which  embryo  and  envelopes  are  formed 

554.  Diagram  of  foetal  membranes    .... 

555.  Exterior  of  the  chorial  sac  (Mare)   . 

556.  Different  parts  of  foetal  Horse   .... 

557.  Foetus  of  the  Mare,  with  its  envelopes 

558.  Portion  of  ultimate  ramifications  of  umbilical  vessels    . 

559.  Vertical  section  of  injected  placenta 

560.  Portion  of  one  of  the  foetal  villi 

561.  Equine  foetus,  opened  on  left  side  to  show  umbilical  vessels 

562.  Blood-vessels  in  liver  of  an  equine  foetus  at  mid-term    . 

563.  Liver  of  a  Lamb  at  birth     .... 

564.  Foetus  of  the  Slieep        .... 

565.  Vertical  section  of  a  maternal  cotyledon 

566.  Embryo  of  the  Chick     .... 

567.  Section  of  embryo  Duck       .... 

568.  Embryo  of  the  Chick    .... 

569.  Transverse  section  of  embryo  of  Chick  on  third  day 

570.  Plan  of  development  of  eye        .... 

571.  Origin  of  encephalic  centres  in  human  embryo  of  fourth  week 

572.  Plan  of  chorda  dorsalis  at  period  of  formation  of  embryo 

573.  Plan  of  vertebra  at  an  early  period  of  development 

574.  Head  of  a  foetal  Lamb,  showing  Meckel's  cartilage 

575.  Plan  of  first  system  of  vessels  (embryo) 

576.  Embryonic  heart  at  an  early  period  (anterior  view) 

577.  Ditto,  seen  from  behind 

578.  Heart  of  an  equine  foetus 

579.  Plan  of  the  aorta  and  its  arches  at  an  early  period 

580.  Plan  of  the  circulation  in  the  human  embryo  (side  view) 

581.  Section  of  embryo  of  Rabbit 

582.  First  appearance  of  the  lungs    . 

583.  Embryo  of  Dog  at  twenty-five  days 

584.  Origin  of  liver  from  intestinal  wall  of  embryo  Chick 

585.  Urinary  and  genital  apparatus  in  embryo  Chick 


Chauveau    . 

PAGE 

986 

Pouchet 

987 

Coste 

988 

Coste 

988 

Pouchet 

989 

Chauveau    . 

991 

Chauveau    . 

994 

Sir  A.  Cooper 

998 

Lehert 

998 

Funke 

999 

Wilson 

1002 

Chauveau 

1004 

BalUani 

1006 

VanBeneden    1006 

Van  Beneden    1007 

Kdlliker 

1008 

Thomson 

1010 

Balfour 

1010 

Balfour 

1011 

Balfour 

1012 

Balfour 

1012 

Balfour 

1013 

Balfour 

1014 

Balfour 

1015 

Turner 

1017 

Chauveau 

1018 

Chauveau 

1020 

Chauveau 

1022 

Carpenter 

1023 

Turner 

1024 

Eclcer 

1025 

Cliauveau 

1026 

Colin 

1026 

Colin 

1027 

Cliauveau 

1028 

Turner 

1029 

Balfour 

1032 

Balfour 

10.33 

Balfour 

1034 

Kolliker 

1035 

Kdlliker 

1035 

Wagner 

1037 

Kdlliker 

1039 

Kolliker 

1039 

Huxley 

.     1039 

Kolliker 

1041 

Kolliker 

.     1042 

Kdlliker 

1042 

Chauveau 

.     1043 

Kolliker 

.     1043 

Coste 

.     1044 

Balfour 

.     1045 

Wagner 

.     1046 

Bischoff 

.     1046 

Muller 

.     1049 

Muller 

.     1050 

THE   COMPARATIVE   ANATOMY 

OF  THE 

DOMESTICATED  ANIMALS. 


GENERAL  CONSIDERATIONS. 

DEFINITION   AND   DIVISIONS   OP  ANATOMY. 

Anatomy  is  the  science  of  organization ;  it  studies  the  structure  of  animals 
when  these  are  dead.  It  comprises  two  grand  divisions — physiological  anatomy ^ 
which  describes  healthy  organs,  and  pathological  anatomy,  the  object  of  which  is 
the  description  of  diseased  organs. 

Physiological  anatomy,  which  alone  is  treated  of  in  this  book,  in  its  turn 
embraces — 

1.  General  anatomy,  which  is  occupied  with  similar  substances  or  tissues  of 
the  animal  body,  with  regard  to  their  texture,  and  their  physical,  chemical,  and 
physiological  properties,  irrespective  of  the  organs  in  which  these  tissues  are 
found.  The  particular  study  of  the  anatomical  elements  entering  into  the 
composition  of  the  tissues,  is  named  histology.  Histology  necessarily  requires 
the  aid  of  the  microscope. 

2.  Descriptive  anatomy,  which  studies  the  situation,  form,  and  relations  of 
organs,  as  well  as  the  relative  arrangement  of  the  various  tissues  composing 
them,  with  the  exception  of  the  structure  and  properties  of  these  tissues. 

If  this  study  be  devoted  to  a  single  species,  it  is  designated  special  anatomy. 
Example  :  human  anatomy,  or  anthropotomy ;  the  anatomy  of  the  Horse,  or 
hippotomy. 

"When  descriptive  anatomy  embraces  the  study  of  the  organization  of  the 
entire  animal  kingdom,  and  examines  the  differences  which  characterize  the  same 
organ  or  the  same  series  of  organs  in  each  class,  family,  genus,  or  species,  it  is 
named  comparative  anatomy.  Restricted  to  the  domesticated  animals,  this  study 
constitutes  veterinary  anatomy. 

Philosophical  or  transcendental  anatomy  differs  from  comparative  anatomy, 
in  that  it  indicates  the  analogies  of  organs  or  apparatus,  rather  than  their 
differences,  in  order  to  exhibit  as  clearly  as  possible  the  general  laws  of 
organization. 

Finally,  if  descriptive  anatomy  be  limited  to  denoting  the  relations  existing 
between  the  various  organs  of  a  region,  particularly  with  a  view  to  the  perform- 
ance of  operations  and  the  diagnosis  of  external  diseases,  it  takes  the  names  of 
topographical,  regional,  or  surgical  anatomy. 


GENERAL   CONSIDERATIONS. 


Enumeration  and  Classification  of  the  Species  of 
Domesticated  Animals. 

The  object  of  this  book  is  the  study  of  veterinary  anatomy.  The  animals  of 
which  it  treats  belong  to  the  Mammiferous  class  and  to  that  of  Birds. 

The  domesticated  Mammals  of  om-  clunates  have  their  representatives  in  a 
large  number  of  orders.     Thus,  we  find  among  them — 

1.  Of  the  Carnivora,  the  Dog  and  Cat; 

2.  A  Rodent,  the  Rahhit  ; 

3.  A  Pachyderm,  the  Pig ; 

4.  Of  Solipeds,  the  Horse  and  Ass ;  the  produce  of  the  Male  Ass  with  the 

mare,  i.e.  the  3fule,  and  that  of  the  Horse  with  the  Female  Ass,  known 
by  the  name  of  Hinny ; 

5.  Of  Ruminants,  the  Ox,  Sheep,  and  Goat. 
With  regard  to  Poultry,  they  range  themselves — 

1.  In  the  Gallinaceous  or  Columba  order,  the  genera  to  which  the  Common 
Fowl,  Guinea  Foivl,  Turkey,  and  Pigeon  belong  ; 

In  the  order  of  Palmipeds,  the  Goose  and  Duclc. 

Girard  has  proposed  a  special  classification  for  the  domesticated  Mammals, 
based  upon  the  number  of  digits  terminating  each  of  their  limbs,  and  has  defined 
four  categories  :  the  first  comprises  the  Horse,  Ass,  Mule,  and  Hinny,  which  take 
the  name  of  monodactyles,  because  their  digital  region  is  composed  of  a  single 
digit ;  in  the  second,  under  the  denomination  of  didactyles  or  bisulcate  animals, 
those  with  two  digits,  such  as  the  Ox,  Sheep,  and  Goat ;  in  the  third,  or  regular 
tetradactyles,  is  found  the  Pig,  each  of  whose  limbs  has  four  digits  ;  lastly,  the 
Dog  and  Cat,  which  most  frequently  have  four  digits  on  the  posterior  members 
and  five  on  the  anterior  ones,  and  form  the  class  of  irregular  tetradactyles. 

This  nomenclature  will  not  be  followed  here,  as  it  is  opposed  to  the  general 
laws  of  organization.  Philosophical  anatomy  has,  in  fact,  demonstrated  that  there 
are  really  no  true  monodactyles,  didactyles,  etc.  ;  all  are  materially  or  virtually 
pentadactyles.  It  is  therefore  considered  better  to  keep  to  the  classification 
established  by  zoologists,  because  it  prevents  confusion  in  scientific  language. 

The  regimen  and  habits  of  the  domesticated  animals  bring  about  diiferences 
in  their  organization ;  these  appear  very  great  at  first  sight,  though  in  reality  they 
are  not  so  marked  as  they  seem. 

In  order  to  study  the  descriptive  anatomy  of  all  these  annuals,  we  will  not 
pass  them  in  review,  one  after  another,  giving  for  each  the  description  of  every 
organ  ;  but  shall  take  a  type,  which  will  most  frequently  be  the  Horse,  implicitly 
compared  with  man,  and  briefly  compare  all  the  others  with  it.  In  this  com- 
parison, the  animals  will  be  generally  classed  according  to  their  domestic  value  ; 
though  exceptions  will  be  made  to  the  rule  which  has  been  instituted  by  our 
predecessors,  whenever  any  advantage  m  point  of  concision  or  perspicuity  is  likely 
to  be  obtained. 

General  Ideas  of  the  Organization  of  Animals. 

Order  followed  in  studying  the  Various  Apparatuses. 

The  bodies  of  animals  contain  fluid  and  solid  organic  matters,  as  well  as  gases 
and  some  mineral  substances. 

Organic  Fluids. — The  fluids  are  very  abundant  in  the  animal  economy ; 


GENERAL   CONSIDERATIONS.  3 

not  only  do  they  fill  certain  vessels  constructed  for  them,  but  they  also 
impregnate  all  the  solid  parts  of  the  body.  Their  importance  is  very  great,  for 
without  them  the  organic  solids  would  perish  ;  an  element  deprived  of  humidity 
is  ipso  facto  deprived  of  life. 

These  fluids  vary  in  their  nature  and  composition.  Apart  from  those  that 
the  solids  imbibe,  there  is  not  one  which  is  completely  amorphous.  In  the 
midst  of  a  liquid  holding  organized  matter  in  solution,  there  are  always  formed 
elements  which  will  be  referred  to  hereafter.     Examples  :  the  blood  and  lymph. 

Organic  Solids. — In  studying  the  organic  solids,  we  will  proceed  from  the 
simple  to  the  complex. 

Solid  organized  matter  is  amorphous — as  in  the  hyaline  substance  of  cartilage 
and  the  fundamental  substance  of  bone  tissue,  or  it  assumes  the  form  of  more 
or  less  voluminous  particles  in  every  instance  invisible  to  the  naked  eye,  and  to 
which  the  name  of  anatomical  elements  has  been  given.  They  may  be  reduced  to 
three  principal :  the  granule,  the  cell,  and  the  fibre. 

Granules. — These  are  the  smallest  known  elements.  They  may  be  held  in 
suspension  in  animal  fluids,  remain  free  among  the  other  elements,  or  be  enclosed 
in  the  interior  of  cells.  Their  nature  is  not  always  the  same  :  they  are  proteic, 
fatty,  or  pigmentary.     The  pigmentary  granules  are  of  a  brown  colour. 

Cells. — The  cell  is  pre-eminently  the  anatomical  element. 

Theoretically,  the  cell  is  a  microscopic  mass  of  a  nitrogenous  substance,  viscid 
{protoplasm  or  sarcode),  uniformly  transparent,  or  slightly  granular.  Frequently 
in  the  midst  of  this  protoplasm  there  is  perceived  a  nucleus  provided  with  a 
nucleolus,  and  at  its  periphery  an  enveloping  membrane. 

The  cell  lives  like  an  entire  organism  :  it  feeds,  grows,  multiplies,  absorbs, 
secretes,  moves,  etc.  It  behaves  like  a  complete  animal,  though  it  be  a  micro- 
scopic one. 

The  form  of  the  cell,  as  well  as  its  volume  and  nature,  vary.  It  has  therefore 
received  various  names. 

There  are  round,  polyhedral,  fusiform,  conical,  stellate,  and  other  shaped 
cells.  Some  have  a  diameter  of  1-1 2000th  part  of  an  inch,  while  others  are 
l-2000th  part.  Cells  multiply  in  various  ways  :  1st,  by  the  division  of  the 
nucleus  and  segmentation  of  the  protoplasm  in  the  interior  of  the  enveloping 
membrane  {endogenous  multiplication)  ;  2nd,  by  constriction,  then  division  of  the 
nucleus,  protoplasm,  and  enveloping  membrane  {flssiparous  multiplication)  ;  3rd, 
by  a  kind  of  bulging  or  swelling  of  the  enveloping  membrane,  and  constriction 
and  separation  of  the  enlargement  thus  formed  {gemmation). 

A  large  number  of  cells  only  temporarily  remain  in  this  condition.  In  con- 
sequence of  modifications  that  cannot  be  referred  to  here,  they  are  converted 
into  fibrillse  or  other  elements,  in  which  it  is  difiicult  to  recognize  the  primordial 
element. 

Others  maintain  the  cellular  form  :  then  they  develop,  live,  and  die  in  several 
ways.  Sometimes  they  are  worn  by  the  contact  of  foreign  bodies,  as  on  the  sur- 
face of  the  skin  ;  sometimes  they  become  liquefied,  as  in  some  glands  ;  and  at 
other  times  they  undergo  fatty  degeneration,  which  gradually  brings  about  their 
complete  destruction. 

The  permanent  cells  are — 

1.  Hcematies  or  red  corpuscles,  which  are  found  in  a  state  of  suspension  in  the 
blood  ;  they  are  round  and  discoid  in  Mammalia,  with  the  exception  of  the 
Camel  and  Llama,  in  which  they  are  elliptical,  as  well  as  in  Birds,  Reptiles,  and 


4  GENERAL   CONSIDERATIONS. 

the  majority  of  Fishes.     These  cells  have  an  envelope,  but  they  do  not  have 
a  nucleus  in  JVIammalia  ; 

2.  Leucocytes,  white  corpuscles,  or  lymph  cells,  which  float  in  the  blood,  lymph, 
chyle,  and  the  connective  tissue  interspaces.  These  cells  are  susceptible  of  amae- 
boid  movements,  and  their  fundamental  form  is  spherical ;  though  they  are  often 
Irregular  in  shape,  owing  to  the  contractile  prolongations  they  throw  out,  called 
pseupodes.     They  may  have  one  or  more  irregular  nuclei ; 

3.  Connective  cells,  which  are  flat,  nucleated,  and  irregular  ;  they  are  applied 
to  the  fasciculi  of  connective  fibres  ; 

4.  Adipose  cells,  lying  in  the  connective  tissue  and  filled  with  fat,  which  has 
pushed  the  protoplasm  and  nucleus  towards  the  envelope  ; 

5.  Medullary  cells,  with  a  budding  nucleus  or  multiple  nuclei  (myeloplaxes 
and  medullo-cells),  forming  the  principal  elements  of  the  marrow  of  bones  ; 

6.  Cartilage  cells,  which  have  no  envelope,  and  which,  single  or  associated 
with  a  variable  intermediate  substance,  form  cartilages  ; 

7.  Bone  cells,  lodged  in  a  space  remarkable  for  its  elliptical  shape  and  the 
numerous  prolongations  on  its  margin.  The  cells  are  nucleated,  have  no  envelope, 
and  secrete  the  fundamental  solid  substance  of  the  bony  tissue  ; 

8.  Contractile  cells,  which  constitute  the  basis  of  muscular  tissue.  They  are 
fusiform  and  nucleated  ; 

9.  Nerve  cells,  met  with  in  the  cerebro-spinal  centres  and  the  ganglia  of  the 
cerebro-spinal  and  sympathetic  systems.  They  are  provided  with  one,  two,  or 
more  prolongations  called  poles ;  hence  they  are  uni-,  bi-,  or  multipolar. 

10.  Epithelial  cells,  found  on  the  surface  of  tegumentary  membranes,  or  laid 
over  the  interior  of  more  or  less  diverticulated  cavities  (glandular  cavities  or  glands). 
The  epithelial  element  is  lamellar  or  polyhedric,  cylindrical,  calcif  orm,  vibratile,  etc. 

11.  Endothelial  cells,  always  lamellar,  and  hning  serous  cavities  and  vascular 
canals. 

Fibres. — A  fibre  is  an  elongated  element  of  variable  dimensions  and  com- 
position. Thus,  it  may  be  very  fine  {connective  fibre),  or  thick  and  limited  by 
two  borders  more  or  less  apart  (muscidar  fibre)  ;  it  is  homogeneous  throughout 
{elastic  fibre),  or  has  a  contents  and  a  distinct  envelope  {nerve  fibre).  The  vitality 
of  fibres  is  not  comparable  with  that  of  cells.  Once  formed,  they  are  only 
nourished,  for  it  is  not  yet  definitely  ascertained  whether  they  can  multiply. 

In  the  animal  economy  there  are  four  kinds  of  fibres — 

1.  Connective  fibre,  an  extremely  fine  element,  but  in  which,  nevertheless, 
two  borders  can  be  distinguished  if  it  be  examined  by  a  power  of  from  800  to 
1000  diameters.  The  fibres  form  fasciculi  in  the  connective  tissue,  or  are  distri- 
buted in  the  midst  of  a  fundamental  substance — as  in  the  fibro-cartilages.  The 
connective  fibre  constitutes  the  most  solid  organs  of  the  animal  economy — the 
ligaments,  tendons,  etc. 

2.  Elastic  fibre,  found  closely  packed  in  certain  organs,  such  as  the  cervical 
ligament  and  abdominal  tunic,  or  forming  a  network  in  the  midst  of  connective 
tissue  ;  it  is  even  found  in  the  framework  of  bones. 

3.  Muscular  fibre,  smooth  or  striped  (striated),  which  has  the  property  of 
contracting  under  the  influence  of  stimuli.  Smooth  (or  unstriped),  is  found 
in  a  large  number  of  viscera  ;  striped  is  more  especially  in  the  domain  of  the 
locomotory  apparatus. 

4.  Nerve  fibre,  very  remarkable  for  its  continuous  axis-cylinder.  It  is  found 
in  the  nerve  centres,  cerebro-spinal  nerves,  and  great  sympathetic  system. 


GENEBAL  CONSIDERATIONS.  5 

I 

Inorganic  Substances. — These  substances  (gases  and  mineral  matters)  are 
usually  found  in  solution  in  the  animal  fluids.  Their  presence  is  indispensable 
in  the  constitution  of  the  living  body. 

Sometimes  the  mineral  matters  are  solid,  amorphous,  or  crystallized.  In  this 
condition  they  are  rarely  met  with  in  healthy  organs  (iriternal  ear)  ;  but  they  are 
frequently  found  in  diseased  ones. 

Tissues. — The  anatomical  elements,  by  being  grouped  in  different  manners, 
form  tissues.  Some  tissues  are  constituted  by  one  kind  of  element ;  these  are 
simple  tissues — for  example,  epithelial  tissue.  But  the  larger  number  are  formed 
by  a  combination  of  several  different  elements  ;  these  are  composite  tissues — for 
example,  nerve  tissue. 

The  anatomical,  physico-chemical,  and  physiological  characters  of  the  tissues, 
are  repeated,  it  need  scarcely  be  remarked,  in  the  anatomical,  physico-chemical, 
and  physiological  properties  of  the  elements  which  enter  into  their  composition. 

Only  four  simple  types  of  fundamental  tissue  are  described,  and  which  are 
based  on  the  morphological,  chemical,  and  physiological  characters  of  the 
constituent  elements — 

1.  In  the  first  place,  there  are  to  be  noted  the  tissues  of  connective  substance 
or  framework,  comprising  the  varieties  of  connective  tissue,  fibrous  tissue,  elastic 
tissue,  cartilaginous  tissue,  and  bone  tissue. 

2.  Then  there  are  the  cellular  tissues,  formed  entirely  of  persistent  cells ; 
they  are  the  epithelial  tissue  proper,  and  the  glandular  tissue. 

The  cells  of  the  epithehal  tissue  are  differently  arranged.  If  they  are 
disposed  in  a  single  layer,  they  constitute  a  simple  epithelium  ;  but  if  superposed 
so  as  to  form  two  or  more  layers,  then  it  is  a  stratified  epithelium.  According  to 
the  form  of  the  superficial  layer  of  cells,  the  epithelium  is  polyhedric,  pavement., 
cylindrical,  spherical,  or  calciform.  In  certain  parts  the  superficial  cells  are 
furnished  with  vibratile  cilia,  and  the  epithehum  is  then  called  vibratile  (or  ciliated). 

3.  The  third  type  is  represented  by  the  muscular  tissue,  the  agent  of  move- 
ment, which  is  divided  into  striated  and  non-striated  muscle. 

4.  Lastly,  there  is  the  nerve  tissue,  which  is  present  under  two  aspects — 
white  substance  and  grey  substance.  The  first  is  formed  entirely  of  nerve  fibres 
and  a  supporting  tissue  or  neuroglia ;  the  second  by  fibres  and  nerve  cells  united 
by  neurogha.  The  grey  substance  belongs  to  the  most  important  portions  of  the 
nervous  system — the  brain,  spinal  cord,  and  gangha,  where  it  co-exists  with  the 
white  substance.  The  latter  entirely  constitutes  the  peripheral  ramifications  of 
the  nervous  system. 

Organs. — The  term  "  organ  "  is  given  to  any  portion  of  the  body  having  a 
determinate  form  and  a  function  to  fulfil.  A  bone,  a  muscle,  the  stomach,  the 
liver,  and  the  brain,  are  organs. 

General  Arrangement  of  the  Organs  and  Apparatus. — All  animal 
organs  are  enclosed  between  two  membranes  named  limitary  or  tegumentary 
membranes,  which  are  continuous  with  one  another  at  the  margin  of  the  natural 
openings.  These  are  the  skin  and  the  mucous  membranes,  in  the  composition  of 
which  are  included  a  layer  of  connective  tissue  and  an  epithelium 

Organs  protected  by  these  membranes  are  solid  or  hollow. 

Among  the  first,  a  certain  number  act  as  supports  :  such  are  the  organs  formed 
by  the  connective  tissue,  and  particularly  the  cartilages  and  bones. 

Others  are  destmed  to  produce  movements  :  these  are  the  muscles.  The 
action  of  the  muscles  is  communicated  directly  to  the  organs  that  are  to  be 


e  GENERAL   CONSIDERATIONS 

moved,  or  it  is  transmitted  through  the  medimn  of  oth%r  organs,  such  as  the 
tendons  and  the  aponeuroses. 

The  central  nervous  organs — the  nerves  properly  so  called — belong  to  this  group 
of  solid  organs.  The  activity  of  muscles  and  the  sensibility  of  limitary  membranes 
are  due  to  them. 

With  regard  to  the  hollow  organs,  they  are  everywhere  formed  by  an  envelope 
of  smooth  (or  unstriped)  muscular  tissue,  lined  by  an  internal  tegumentary  or 
mucous  membrane.  Examples  :  the  bladder  and  stomach.  There  must  also  be 
included  the  vessels  formed  by  elastic  and  contractile  membranes  arranged  as 
canals,  in  which  the  blood  and  lymph  circulate  ;  the  glands,  and,  lastly,  the  serous 
membranes  which  line  the  interior  of  the  splanchnic  cavities,  cover  the  surface  of 
the  organs  contained  in  them,  and  the  inner  face  of  the  articulations  and  synovial 
sheaths. 

It  is  remarkable  that,  in  the  trunk,  the  bones  form  two  superposed  cylinders, 
one  of  which  lodges  the  organs  of  circulation,  digestion,  and  respiration,  and  the 
other  the  central  nervous  system  (neural  and  luemal  ajUnder). 

Apparatus. — Organs  are  very  numerous  in  the  animal  economy,  and  in  order 
to  study  them  profitably  it  is  necessary  to  classify  them  in  a  methodical  manner, 
according  to  their  physiological  affinities.  Consequently,  there  have  been  col- 
lected into  a  single  category  all  those  organs  which  are  destined  to  achieve  the 
same  physiological  finality,  and  to  such  a  group  has  been  given  the  name  of 
apparatus. 

Bichat  has  grouped  the  apparatuses  according  to  the  ultimate  object  of  their 
functions,  and  has  thus  formed  two  great  categories  :  one,  comprising  the 
apparatuses  which  maintain  the  individual  {apparatuses  of  nutrition  and  relation)  ; 
the  other,  the  apparatus  destined  for  the  preservation  of  the  species  {apparatus  of 
generation). 

We  will  describe  these  apparatuses  in  the  following  order  : — 

1.  Locomotory  Apparatus ; 

2.  Digestive  Apparatus ; 

3.  Respiratory  Apparatus ; 

4.  Urinary  Depurative  Apparatus ; 

5.  Circulatory  Apparatus ; 

6.  Inner vatory  Apparatus ; 

7.  Sensory  Apparatus ; 

8.  Generative  Apparatus. 

This  description  will  be  terminated  by  a  brief  notice  of  the  evolution  of  ths 
/(Btus^  and  its  appendages. 


BOOK  I. 

LocoMOTORY  Apparatus. 

The  locomotory  apparatus  is  composed  of  all  those  organs  which  minister  to  the 
movements  an  animal  may  execute.  It  is  certainly  one  of  the  most  important  in 
the  economy,  from  the  nmnber  and  size  of  the  pieces  which  enter  into  its 
formation,  and  by  the  necessary  co-operation  it  affords  the  majority  of  the  other 
apparatuses  in  the  performance  of  the  physiological  acts  allotted  to  them. 

It  is  constituted  of  two  kinds  of  organs— the  bones  and  muscles.  The  hones, 
hard  and  resisting,  stony  in  appearance,  are  really  inert  levers,  joined  by  firm 
and  movable  articulatmis,  which  permit  their  playing  upon  each  other  with  the 
greatest  facility,  at  the  same  time  maintaining  them  in  their  relative  positions. 
The  muscles,  grouped  around  the  bones  and  attached  to  them,  are  soft  organs 
which  possess  the  property  of  contraction,  under  certain  determinate  conditions, 
and  of  involving  in  that  movement  the  bones  to  which  they  are  fixed  by  their 
extremities.  The  bones  are  altogether  passive  in  their  motion,  while  the  muscles 
are  really  the  active  organs  of  locomotion — the  power  intended  to  move  the  bony 
levers. 

We  will  study,  successively — 

1.  The  bones,  a  particular  branch  of  descriptive  anatomy  which  has  received 

the  name  of  Osteology  ; 

2.  The  articulations,  or  Arthrology ; 

3.  The  muscles,  or  Myology. 


FIRST  SECTION. 
The  Bones. 

CHAPTER    I. 
THE    BONES    IN    GENERAL. 


Bones,  properly  speaking,  are  only  to  be  found  in  vertebrate  animals,  and 
constitute  their  principal  zoological  character.  In  the  animal  body  they  form 
an  internal  framework  which  consolidates  the  entire  edifice,  and  gives  it  its 
general  form  and  dimensions.  It  is  advantageous,  before  commencing  a  particular 
description  of  each  bone,  to  survey  them  in  a  general  manner.  This  study 
comprises:    1.  The  description  of   the   skeleton;   2.  A   summary  indication   of 


8  TEE  BONES. 

ihQ  general  principles  which  should  be  known,  in  order  to  comprehend  the  details 
of  the  special  descriptions. 

Aeticle  I. — The  Skeleton. 
The  whole  of  the  bones,  considered  in  their  natural  relations  to  each  other, 
constitute  the  skeleton.     In  order  to  prepare  the  skeleton  of  any  animal,  it  is 


SKELETON    OF   THE   DOG. 


sufficient  to  free  it  from  the  soft  parts  surrounding  it.     The  skeleton  should  be 
designated  natural,  if  in  this  operation  the  ligaments  that  naturally  join  the 

Fig.  2. 


SKELETON    OF   THE   CAT. 


various  pieces  together  are  allowed  to  remain  ;  and  artificial  if,  after  these  liga- 
ments have  been  destroyed,  it  is  necessary  to  replace  them  by  materials  foreign 
to  the  organization,  such  as  iron  or  brass  wire. 


THE  SKELETON.  9 

The  skeleton  is  divided  into  trunk  and  limbs. 

1.  The  trunk  offers  for  consideration,  in  the  middle  line,  the  spine  or 
vertebral  column — a  flexible  stalk  measuring  the  entire  length  of  the  animal,  and 
composed  of  a  series  of  distinct  pieces  articulated  one  behind  the  other.  An- 
teriorly, this  stalk  supports  the  head — a  pyramidal  mass  which  results  from  the 
assemblage  of  a  large  number  of  bones.     On  each  side  of  the  middle  portion  of 

Fig.  3. 


SKELETON   OF  THE   PIG. 

I 

the  spine,  there  are  detached  bony  arches  which  have  received  the  name  of  ribs, 
and  which  rest,  directly  or  indirectly,  by  their  inferior  extremities,  on  a  single 
bone  called  the  sternum.  These  bony  arches  in  this  way  circumscribe  the  thorax — 
a  spacious  cavity  destined  for  the  reception  of  the  principal  organs  of  respiration 
and  circulation. 

2.  The  limbs,  four  in  number — two  anterior  and  two  posterior — are  the  ap- 

Fig.  4. 


SKELETON   OF   THE   RABBIT. 


pendages  which  support  the  trunk  of  the  domestic  Mammals.  They  are  usually 
distinguished  as  anterior  and  posterior  (or  fore  and  hind),  but  it  will  be  more 
convenient  to  name  them  according  to  their  relations,  as  thoracic  (or  pectoral)  and 
abdominal  limbs.  Each  represents  a  column  divided  into  several  rays  resting  upon 
one  another,  and  generally  forming  more  or  less  open  angles.     The  anterior  limbs 


10 


THE  BONES. 


are  each  divisible  into  four  principal  regions  :  the  shoulder,  applied  against  the 
front  part  of  the  thorax ;  the  arm,  which  succeeds  the  shoulder  ;  and  the  fore- 


SKELETON    OP   THE    HORSE. 


arm,  and  foot.  The  posterior  limbs  also  comprise  four  regions  :  the  haunch  or 
pelvis,  which  articulates  with  the  posterior  part  of  the  spine  ;  and  the  thigh,  leg^ 
and  posterior  foot. 

Fig.  6. 


SKELETON    OF  THE   COW. 


In  Birds,  the  posterior  limbs  alone  assume  the  function  of  columns  of  support. 
The  thoracic  limbs,  formed  for  flight,  constitute  the  wings. 


GENERAL  PRINCIPLES  APPLICABLE  TO  THE  STUDY  OF  ALL  THE  BONES.     11 


The  number  of  bones  entering  into  the  composition  of  the  skeleton  of  the 
principal  domesticated  animals,  arrived  at  the  adult  period  of  life,  varies  accord- 


Fig.  7. 


SKELETON    OF   THE  SHEEP. 


ing  to  the  species.    They  are  apportioned  to  the  regions  of  the  trunk  and  limbs 
just  mentioned,  in  the  manner  indicated  in  the  following  table  : — 


Designation. 

SOLIPEDS.' 

Ruminants. 

Pig. 

Dog.' 

Vertebral  Column' 

Head^ 

48 

28 

37 

1-  2 

1—  2 

2—  2 
16-32 

1—  2 
1-  2 

3—  6 
15-30 

45 

28 

27 

1—  2 

1-  2 

2-  4 
20-40 

1-  2 
1—  2 

3-  6 
19—38 

50 

29 

29 

1—  2 

1—  2 

2—  4 
36—72 

1—  2 
I—  2 

3—  6 
36-72 

46 

28 

27 

1—  2 

1—  2 

2—  4 
36—72 

1-  2 
1—  2 

3—  6 
32—64 

Thorax 
Shoulder 
Arm    . 
Forearm 
Fore  foot 
Pelvis 
Thigh 
Leg    . 
Hind  fool 

^    Double  regions    - 

Tc 

tals 

191 

196 

270 

255 

AeTICLE    II. — GElfEEAL    PkINCIPLES    APPLICABLE    TO    THE    StUDY   OF    ALL 

THE  Bones, 

The  description  of  a  bone  comprises  its  name,  situation,  shape,  internal  cori' 
formation,  structure,  and  mode  of  development. 

'  One  lumbar  vertebra  less  is  found  in  the  Ass,  and  sometimes  also  in  the  Mule. 

*  The  08  penis  has  not  been  included. 

'  The  sacrum  is  reckoned  as  a  single  bone,  and  the  number  of  coccygeal  vertebrae  at  aa 
average  of  16  for  the  Horse,  18  for  the  Ox,  22  for  the  Pig,  and  18  for  the  Dog. 

*  The  OS  hyoides  is  reckoned  as  a  single  bone. 


12 


THE  BONES. 

Name. 


The  nomenclature  of  osteology  does  not  rest  on  any  basis  capable  of  confer- 
ring upon  it  a  methodic  form.  Consequently,  we  find  bones  which  derive  their 
name  from  their  shape  (example  :  the  fibula)  ;  others  from  their  resemblance 


to  known  objects  (the  tibia  and  vomer).  Some  owe  it  to  their  position  (the 
frontal  bone),  or  their  uses  (the  axis  and  parietal  bones).  Several  attempts 
have  been  made  to  submit  the  nomenclature  of  the  bones  to  more  precise 


GENERAL  PRINCIPLES  APPLICABLE  TO  TEE  STUDY  OF  ALL  THE  BONES.    13 

and  uniform  rules,  but  the  new  designations  proposed  have  not  been  sanctioned 
by  custom. 

Situation. 
The  situation  of  a  bone  should  be  viewed  in  two  ways  :  1st,  Relative  to  the 
median  plane  of  the  body ;  2nd,  Relative  to  the  other  portions  of  the  skeleton. 

A.  Situation  relative  to  the  median  plane  of  the  body. — The  designation  of 
median  plane,  improperly  median  line,  is  given  to  an  imaginary  vertical  plane 
passing  through  the  middle  of  the  skeleton,  which  it  divides  from  before  to 
behind,  into  two  equal  portions.  The  bones  may  be  situat|^  on  the  median 
plane,  in  which  case  there  is  only  one  of  each  kind,  and  they  are  called  single ; 
they  are  also  named  symmetrical  bones,  because  the  median  plane  divides  them 
into  equal  lateral  halves  exactly  alike.^  The  bones  disposed  in  a  double  and 
regular  manner  on  the  sides  of  the  median  plane  bear,  for  this  reason,  the  name 
of  pair  bones ;  they  are  also  called  asymmetrical  bones,  because  their  form  does 
not  admit  of  their  being  divided,  in  any  sense,  into  two  similar  portions.  On  the 
contrary,  a  bone  of  this  kind  always  offers  the  most  perfect  symmetry  with  its 
fellow  on  the  opposite  side.^ 

B.  Relative  situation  to  the  other  parts  of  the  skeleton. — To  indicate  the 
situation  of  a  bone,  considered  from  this  point  of  view,  is  to  make  known  the 
place  it  occupies  in  the  region  to  which  it  belongs,  and  the  connections  it  may 
have  with  adjoining  regions.  Thus,  the  radius  is  situated  in  front  of  the  ulna, 
between  the  arm-bone  and  the  carpus. 

Direction. 

This  is  absolute  or  relative. 

A.  The  absolute  direction  is  related  to  the  axes  of  the  bones  themselves.  Thus 
it  is  that  a  bone  may  be  rectilinear,  curvilinear,  or  twisted. 

B.  The  relative  direction  is  determined  by  the  relation  to  the  fictitious  planes 
established  around  or  in  the  interior  of  the  skeleton,  or  with  regard  to  the 
neighbouring  bones.  For  example,  a  bone  is  vertical,  horizontal,  or  oblique.  In 
the  latter  case  it  may  be  downwards  and  backwards,  or  in  the  reverse  direction. 
Example  :  the  scapula  is  placed  obliquely  downwards  and  forwards. 

Shape  of  the  Bones. 

Form. — This  is  also  absolute  or  relative. 

A.  Absolute  Form. — The  absolute  form  of  a  bone  is  that  which  it  owes  to 
the  relations  existing  between  its  three  dimensions — length,  width,  and  thickness. 
a.  A  bone  in  which  one  of  its  dimensions  much  exceeds  those  of  the  other  two  is 
a  long  bojie  (example  :  the  femur),  provided  it  be  hollowed  out  internally  by  an 
elongated  space— the  medullary  canal.  Long  bones  belong  exclusively  to  the 
limbs.  In  the  animal  economy  there  are  found  bones  which  resemble  them  in 
their  dimensions,  but  they  have  no  medullary  canal  (example :  the  ribs). 
These  differ  essentially  from  the  true  long  bones,  and  are  also  distinguished  from 
them  by  the  appellation  of  elongated  bones,  b.  A  bone  that  offers  two  dimensions 
much  more  developed  than  the  third,  is  a  flat  or  tvide  bone  (example  :  the 
parietal  bone).     The  bones  of  this  category,  destitute  of  a  medullary  cavity,  are 

•  Instances  have  been  recorded  of  asymmetry  in  single  bones.  Lesbre  has  seen  the  sixth 
cervical  vertebra  of  the  Horse  tricuspid  on  one  side  and  bicuspid  on  the  other,  and  a  last  dorsal 
vertebra  with  one  of  its  transverse  processes  having  the  characters  of  the  lumbar  vertebraj. 

*  But  there  might  be  slight  differences  in  weight,  torsion,  etc.  In  Man  there  is  nearly 
always  a  difference  between  the  right  and  the  left  side. 

4 


14  TEE  BONES. 

met  with  in  the  head  and  the  upper  regions  of  the  Umbs.  c.  A  bone  which 
offers  nearly  the  same  development  in  all  its  dimensions,  is  called  a  short  bone 
(example  :  the  astragalus).  Destitute,  like  the  preceding,  of  a  medullary  canal, 
the  short  bones  are  found  in  the  spine  and  some  regions  of  the  limbs. 

B.  Relative  Form. — To  make  known  the  relative  form  of  a  bone,  is  to  indicate 
the  greater  or  less  exact  resemblance  it  may  bear  to  geometrical  figures,  or  to 
familiar  objects.     Thus,  the  scapula  is  a  bone  of  a  triangular  shape. 

Regions  of  the  Bones. — When  describing  the  eminences  and  external 
cavities  of  bone^  it  is  essential  not  to  allude  to  them  casually  by  passing 
indifferently  from  one  to  another.  To  avoid  the  diificulties  resulting  from  the 
application  of  such  an  irrational  system,  it  is  necessary  to  divide  the  bone  to  be 
studied  into  several  regions,  in  which  external  peculiarities  can  be  examined 
successively,  as  they  present  themselves.  The  general  course  to  be  followed  in 
order  to  learn  the  regions  of  a  long,  a  flat,  and  a  short  bone,  is  as  follows  : — 

a.  A  long  bone  is  always  divided  into  three  parts — a  body  and  two  extremities. 
The  bod//  or  middle  portion,  or  diaphysis,  is  the  narrowest  part  of  the  bone.  In 
shape  it  is  a  geometrical  solid,  inclining  somewhat  to  that  of  a  very  long  prism. 
On  the  body  of  a  bone,  therefore,  there  are  studied  as  many  faces  and  planes, 
angles  or  borders,  as  on  the  prism  it  represents. 

The  extremities,  or  epiphyses,  are  more  or  less  considerable  enlargements, 
formed  primarily  by  a  special  bony  nucleus,  and  offering  articular  surfaces,  as 
well  as  surfaces  for  muscular  or  ligamentous  insertion. 

b.  A  flat  bone  must  necessarily  have  two  faces,  and  borders  and  angles. 

c.  A  short  bone  has  more  or  less  faces,  and  plane  or  salient  angles  which  are 
often  ignored,  because  of  their  trifling  ijnportance. 

External  Peculiarities  of  Bones. — These  markedly  attract  the  attention, 
because  they  modify  the  general  shape  of  bones,  and  singularly  assist  in 
distinguishing  one  bone  from  another.  These  peculiarities,  which  are  real 
distinctive  features  that  permit  their  description  to  be  precisely  established,  are 
always  either  eminences  or  cavities,  according  to  their  different  uses. 

A.  Eminences. — The  eminences  that  stand  out  in  relief  from  the  surfaces 
of  bones,  are  divided  into  two  different  categories.  One  class  concurs  in  the 
formation  of  the  articulations  which  join  the  bones  to  each  other ;  they  are 
named  articular  eminences,  in  which,  again,  are  distinguished  diarthrodial  and 
synarthrodial  eminences,  according  as  they  belong  to  movable  or  immovable 
articulations.  The  others,  usually  destined  for  the  insertion  of  ligaments  and 
muscles,  are  called  non-art icidar  eminences  or  eminences  of  insertion. 

(The  term  imp-int  is  also  used  in  anatomy,  and  signifies  a  collection  of  small 
rugged  eminences  which  make  the  surface  of  the  bone  uneven  and  rough.  There 
are  muscular,  tendinous,  ligamentous,  and  aponeurotic  imprints,  according  as 
they  give  attachment  to  muscles,  tendons,  ligaments,  or  aponeuroses.) 

a.  The  synarthrodial  eminences  are  always  indentations  more  or  less  deep  and 
finely  cut,  which  stud  the  border  of  large  bones. 

b.  The  diarthrodial  eminences  are  volimiinous,  smooth,  and  in  a  fresh  state 
covered  with  cartilage.  They  are  named  heads  and  condyles  :  heads,  when  they 
describe  the  segment  of  a  sphere  (head  of  the  femur,  head  of  the  humerus) ; 
condyles,  when  they  represent  an  ovoid  segment  cut  parallel  to  its  larger  axis 
(condyles  of  the  femur). 

c.  The  non-articular  eminences  receive  various  names.  If  they  are  volumi- 
nous and  much  detached  from  the  bone,  they  are  called  processes  or  apophyses. 


GENERAL  PBINOIPLES  APPLICABLE  TO  THE  STUDY  OF  ALL  THE  BONES.     15 

Apophyses  receive  qualificatives  derived  from  the  analogies  perceived  between 
them  and  known  objects  (examples  :  the  styloid,  clinoid,  coronoid,  and  coracoid 
processes).  The  appellations  of  protuberances  and  hiherosities  are  given  to  non- 
articular  eminences  when  they  are  large  and  round,  and  slightly  detached. 
Lastly,  they  are  named  lines,  crests,  and  ridges,  when  they  are  narrow  and 
very  long. 

The  processes  are  sometimes  epiphysary  in  early  life,  and  formed  by  a  special 
nucleus. 

B.  Cavities. — The  cavities  of  bones  have  also  been  divided  into  articular, 
diarthrodial  or  synarthrodia! ,  and  non-articular  cavities. 

a.  The  diarthrodial  cavities  correspond  to  the  eminences  of  the  same  name  in 
the  bony  joints.  They  take  the  designation  of  glenoid  cavities  when  they  are 
oval  and  shallow,  and  cotyloid  cavities  when  they  are  deeply  excavated,  like  a 
basin  or  the  cup  of  an  acorn  (examples  :  the  glenoid  cavity  of  the  scapula,  and  the 
cotyloid  cavity  of  the  coxa).  The  synarthrodial  cavities  fit  into  the  dentations 
opposed  to  them. 

b.  The  non-articular  cavities  serve  either  for  hgamentous  or  muscular 
insertion,  or  for  the  passage  of  vessels,  nerves,  tendons,  etc. 

They  are  termed  channels  or  furrows,  when  they  are  wide,  deep,  and  smooth  ; 
grooves,  when  they  are  long,  narrow,  and  smooth  at  the  bottom  ;  and  fissures, 
when  they  are  narrow  and  rugged.  Digitcd  impi'essions  is  the  name  given  to 
those  excavations  in  bones  which  look  as  if  produced  by  the  pressure  of  the 
finger.  The  fossce,  sinuses,  cells,  and  notches  are  also  non-articular  cavities  of 
bones.  The  sinuses  and  cells  are  formed  by  open  spaces  in  the  interior  of 
bones  ;  notches,  by  cavities  excavated  on  their  margins. 

When  a  cavity  passes  quite  through  a  bone,  it  is  termed  a  foramen.  If  this 
foramen  has  a  certain  length,  it  is  designated  a  conduit  or  canal.  Fissures  are 
long,  narrow  openings  ;  hiatus  is  the  term  applied  to  a  wide  opening  with  an 
irregular  outline. 

In  order  to  aid  the  memory,  the  external  peculiarities  of  bones  are  grouped 
in  the  following  synoptical  table  : — 


i  Non-Articulars 


(  Synarthrodials  .  Dentations. 
JDiarthrodials  .  (  gf^^^^s. 

I  Styloids. 
Coracoids. 
Mastoids. 
1  1  uoerosiiies. 

Lines. 
^Crests. 


i 

Articulars.     .    .. 

aynarmroaiaiB  -J  Dentation 
^Diarthrodials     .{^^^^ 

Channels. 

^, 

Furrows. 

•< ' 

Grooves. 

o 

Digital  impressions. 

pa 

Fossae. 
Sinuses. 

Non-Articulars  .< 

Cells. 

Notches. 

Foraminse. 

Canals. 

Ducts. 

Slits. 

,  Hiatuses. 

Internal  Conformation  of  Bones. 

Sections  made  in  various  directions  through  the  substance  of  bones,  show 
that  their  internal  conformation  varies,  according  as  they  belong  to  the  category 
of  long,  flat,  or  short  bones  The  diaphysis  of  long  bones  is  hollowed  out  into  a 
large  fusiform  cavity — the  medullary  canal.  This'  canal  is  absent  in  the  flat  and 
short  bones,  and  is  replaced  by  irregular  cavities  which  communicate  with  each 
other,  called  medullary  spaces.    Its  walls  are  formed  by  a  very  dense  bony  tissue, 


16 


TEE  BONES. 


the  pores  of  which  are  scarcely  visible  to  the  naked  eye,  and  which  is  called  the 
compact  substance.  The  extremities  of  long  bones  are  surrounded  by  a  thin 
layer  of  compact  substance,  while  the  remainder  of  their  mass  is  constituted  by 
the  spongy  substance — bony  tissue  channeled  into  medullary  spaces.  { Reticulated 
bony  tissue  is  but  another  form  of  spongy  substance,  the  only  difference  between 
the  two  consisting  in  the  cells  or  meshes  of  the  first  being  formed  of  intercrossed 
osseous  fibres,  while  those  of  the  second  are  formed  of  lameUce.)  The  medullary 
canal,  and  areolae  of  the  spongy  tissue,  are  filled  by  the  marrow  (or  medulla). 

The  flat  bones  are  constituted  by  a  layer  of  spongy  tissue  placed  between  two 
plates  of  compact  substance.  (In  the  flat  bones  of  the  cranium,  the  two  layers 
of  compact  tissue  are  termed  the  vitreous  tables,  while  the  cells  of  the  spongy 
tissue  are  designated  diploe.)  In  certain  points  of  their  extent,  the  spongy 
substance  disappears,  and  then  the  bone  is  composed  of  a  single  lamina  of 
compact  tissue. 

The  short  bones  have  a  nucleus  of  spongy  substance,  enveloped  in  a  layer^ 
more  or  less  thick,  of  compact  tissue. 

The  compact  substance  of  the  bones,  being  very  resisting,  is  found  in  all 
those  situations  which  have  to  sustain  violent  efforts.  The  spongy  substance  is 
very  hght  when  compared  with  its  volume,  and  is  met  with  in  the  wider  portions  of 
the  bones,  to  which  it  affords  increased  size  without  adding  sensibly  to  their  weight. 

Structure  of  Bones. 

Bones  are  formed  of  a  proper  tissue,  covered  externally  by  a  particular 
membrane — the  periosteum,  and  occupied  internally  by  the  medulla,  vessels,  and 
nerves. 

A.  Proper  tissue. — The  elements  of  the  proper  tissue  of  bone  are  always  and 
everywhere  the  same  ;  the  texture  alone  is  modified  in 
the  compact  and  spongy  substance. 

Everywhere  the  bone  tissue  is  composed  of  a  funda- 
mental substance,  which  is  amorphous  or  slightlj 
granular,  white,  and  more  or  less  opaque,  according  to 
the  thickness  it  offers.  This  fundamental  substance  is 
penetrated  by  an  infinite  number  of  vascular  canaliculi 
[bone  cavities),  with  prolongations  {hone  canaliculi), 
which  contain  cells  {bone  cells).  The  cavities  and  their 
contents  are  named  osseous  corpuscles  or  osteoplasts.  In 
a  dried  plate  of  bone,  the  corpuscles  appear  dark  when 
viewed  by  reflected  light,  white  and  shining  by  direct 
light. 

In  the  spongy  tissue,  the  bone  corpuscles,  anasto- 
mosing by  the  ends  of  their  canahcuh,  are  distributed 
throughout  the  lamellte  of  fundamental  substance,  which 
is  intercrossed  in  such  a  way  as  to  circumscribe  the 
numerous  medullary  spaces. 

In  the  compact  tissue,  the  corpuscles  are  regularly  distributed  in  the 
substance  of  the  bony  lamellae,  which  are  arranged  in  concentric  layers. 

In  a  transverse  section  of  the  diaphysis  of  a  long  bone,  it  is  noticed  that  the 
fundamental  substance  is  excavated  by  an  infinite  number  of  vascular  canaliculi, 
named  Haversian  canals  (Figs.  9,  10).  These  canals  measure  from  l-2500th  to 
l-200th  of  an  inch  in  diameter,  and  are  parallel  to  each  other  and  to  the  larger 


Fig.  9. 


VERTICAL    SECTION    OF     BONE, 

showing     the    network     of 
Haversian  canals. 


GENERAL  PRINCIPLES  APPLICABLE  TO  THE  STUDY  OF  ALL  THE  BONES.    17 


axis  of  the  bone  ;  they  communicate  frequently  by  transverse  branches.     "While 
the  most  superficial  open  on  the  surface  of  the  bone,  beneath  the  periosteum, 
and  the  deepest  into  the  medullary  canal,  a  certain  number  terminate  in  the 
areolae  of  the  spongy  substance  at  the 
ends  of  the  bones.  '^"     * 

The  wails  of  these  canals  are  con- 
stituted by  several  concentric  lamellae 
of  fundamental  substance,  in  which  are 
lodged  the  essential  elements  of  the 
bony  tissue.  Each  canal,  with  its 
vessels,  its  system  of  concentric  lamellae, 
its  osteoplasts,  and  its  osseous  canaliculi, 
forms  a  whole  (the  Haversian  system) 
which  represents  the  complete  bone  in 
miniature.  All  the  Haversian  systems 
preserve  a  certain  independence  ;  the 
canalicuh  of  each,  after  reaching  the  minute  structure  of  bone,  as  shown  iu  a  thia 

.    ,  1         11         n      ,     1    ,  section  cut  transversely  to  the  direction  of  the 

periphery,  are  nearly  all  reflected  to-      Haversian  canals. 

wards  the  centre  (the  recurrent  canaliculi  l,  A  Haversian  canal  surrounded  by  its  concentric 


lamellse  ;  the  lacunae  are  seen  between  the 
lamella',  but  the  radiating  tubuli  are  omitted; 
2,  ibid.,  with  its  concentric  laminae,  lacunae,  and 
radiating  tuhuli;  3,  the  area  of  one  of  the 
canals  ;  4,  4,  intervening  lamelljE,  and  between 
them,  at  the  upper  part,  several  very  long 
lacunae  with  their  tubuli. 


Fig.  11. 


of  Ranvier)  and  rejoin  the  canaliculi  of 
the  same  system,  instead  of  anasto- 
mosing with  those  of  the  neighbouring 
system. 

Between  the  Haversian  systems, 
there  are  the  intermediate  systems  of 
lamellae  which  fill  the  spaces  left  through 
the  imperfect  contact  of  the  former. 
In  all  the  long  bones  there  is  a  system 
of  periphercd  lamellae,  enveloping,  ex- 
ternally, all  the  Haversian  systems ; 
while  a  system  of  perimediiUary  lamellce, 
more  or  less  perfect,  also  exists  at  the 
inner  surface  of  the  medullary  canal.       ^*«^^^^'  ^^  '^'''^*?rf ™  °!-  ''''f'''  substance, 

,,,  ,  ^    ,         1-11  magnified  500  diameters. 

Sharpey  observed  that  the  peripheral  ^^  ^^^^,^1  ^^^-^^ .  j^  j^s  ramifications, 

bony  lamellte  were  traversed  by  fibres 

{Sharpey's  ov  perforating  fibres),  and  J.  Renaut  has  remarked  in  the  same  lamellae 
the  presence  of  elastic  fibres. 

The  proper  tissue  of  bones  is  a  framework  of  organic  matter  which  has 
gelatine  for  its  base,  and  in  which  are  deposited  the  calcareous  phosphates 
and  carbonates  which  give  to  this  tissue  its  characteristic  hardness.  This 
is  easily  rendered  evident  by  immersing  any  bone  in  dilute  nitric  or  hydro- 
chloric acid  ;  acid  dissolve  the  calcareous  salts,  but  do  not  act  upon  the  organic 
framework.  So  it  is,  that  after  some  days'  maceration  the  bone  becomes 
flexible,  like  cartilage,  and  loses  part  of  its  weight,  although  it  preserves  its 
volume  and  shape.  The  counterpart  of  this  experiment  may  be  made  by 
submitting  it  to  the  action  of  fire.  It  is  then  rendered  quite  friable,  because  its 
organic  skeleton  has  been  destroyed,  without  the  earthy  salts  it  contained  being 
affected. 

B.  Periosteum. — This  is  a  very  vascular  and  nervous  fibrous  membrane  which 
covers  the  entire   bone,  with  the  exception  of  the  articular  surfaces  and  the 


18  THE  BONES. 

insertions  of  tendons  and  ligaments.  Its  thickness  and  adherence  are  not  the 
same  everywhere  ;  it  adheres  most  closely  near  the  ends  of  bones.  By  its  inner 
face  it  corresponds  to  the  surface  of  the  bone,  into  which  it  sends  prolongations 
{arciform  fibres)  which  ultimately  become  Sharpey's  fibres  ;  by  its  external  face, 
it  is  continuous  with  the  surrounding  connective  tissue  and  that  of  the  muscular 
aponeuroses. 

The  periosteum  may  be  resolved  into  two  layers,  though  these  are  not  always 
very  distinct.  The  superficial  layer  is  essentially  fibrous,  and  is  formed  by  a 
network  of  elastic  fibres  containing  bundles  of  longitudinal  fibres  and  cells. 
The  deep  layer  is  a  closer  elastic  network,  with  finer  connective  tissue  fibres,  and 
a  larger  quantity  of  cells  and  vessels.  This  is  called  the  osteogenous  layer , 
because  of  its  functions. 

C.  Medulla. — The  medulla,  or  marrow,  is  a  pulpy,  fatty  substance,  which  fills 
the  medullary  canal  and  the  areola  of  the  spongy  tissue  of  the  bones,  and 
partly  the  Haversian  canals.  Somewhat  consistent,  and  of  a  rosy  tint  in  the 
bones  of  young  animals,  the  marrow  becomes  diffluent  and  yellow  in  the  bones 
of  those  advanced  in  age,  except  in  the  vertebrae  of  the  Horse,  Ox,  Dog,  etc., 
and  in  the  limbs  of  the  Rabbit.  In  the  first  state,  it  is  also  mucous  or  fibrous  in 
the  cranial  and  facial  bones  undergoing  development,  and,  rosy  in  colour,  it 
only  contains  traces  of  fat ;  while  in  the  second,  it  has  96  per  cent,  of  this 
substance.  The  medulla  of  bones  is  composed  of  :  1st,  some  trabecul^e  of 
delicate  connective  tissue  and  a  network  of  stellate  cells,  to  support  the  vessels 
and  nerves ;  2nd,  fat  cells ;  3rd,  particular  cells,  named  by  M.  Robin  medullo- 
cells  and  myeloplaxes. 

The  medullo-cells,  abundant  in  the  red  or  foetal  marrow,  are  small  cells  with  a 
spherical  or  budding  nucleus  {Bizzozero's  cells),  analogous  to  the  lymph  cells ; 
some  are  impregnated  with  hgemoglobine.  With  regard  to  the  myeloplaxes,  these 
are  enormous  flat  cells,  irregular  in  outline,  and  containing  a  large  number  of 
nuclei.  Rare  in  the  yellow  marrow,  they  are  more  particularly  found  adhering 
to  the  walls  of  the  medullary  canal,  or  the  alveoli  of  the  spongy  tissue. 

D.  Blood-vessels. — The  arteries  of  bones  belong  to  three  orders — a  distinction 
based  on  their  volume  and  the  extent  of  their  distribution. 

The  arteries  of  the  first  order  penetrate  to  the  interior  of  the  medullary 
canal  of  long  bones,  by  a  particular  orifice — the  nutrient  foramen.  They  soon 
divide  into  two  branches,  which  break  up  into  a  network  that  lines  the  walls 
of  the  canal  and  enters  the  tissue  of  the  medulla.  This  network  communicates 
with  the  arteries  of  the  second  order,  which  go  to  the  spongy  tissue  of  the 
extremities  of  the  long  bones,  penetrating  them  by  the  numerous  nutritive 
foramina  that  surround  the  epiphyses.  Lastly,  the  arteries  of  the  third  order 
are  branches  of  the  periostic  network  that  enters  the  superficial  Haversian 
canals.  These  canals  may  be  considered,  strictly  speaking,  as  a  third  category 
of  nutrient  conduits.  In  the  flat  and  short  bones  there  are  no  arteries  of  the 
first  order. 

Veins  accompany  the  arteries,  and  are  always  more  voluminous  than  these ; 
they  frequently  make  their  exit  by  special  and  very  large  openings  at  those 
points  where  the  spongy  tissue  is  abundant.  The  veins  of  bones  sometimes 
exhibit  saccular  dilatations  on  their  course.  Certain  veins  in  the  cranial  bones 
have  their  walls  partly  or  entirely  channeled  in  the  bony  tissue  ;  they  are  lined 
by  a  simple  endothelium. 

E.  Lymphatic  vessels. — The  existence  of  these  cannot  be  affirmed. 


GENERAL  PRINCIPLES  APPLICABLE  TO  THE  STUDY  OF  ALL  THE  BONES.    19 

Nerves. — These  belong  to  the  eerebro-spinal  and  ganglionic  system  of  nerves  ; 
the  latter  are  always  vaso-motor  nerves. 

Almost  constantly,  a  somewhat  volmninous  nerve  enters  the  medullary  canal, 
by  passing  through  the  nutrient  foramen,  and  is  distributed  to  the  medulla. 
The  compact  tissue  receives  few  nerve  filaments  ;  while,  on  the  contrary,  the 
spongy  tissue  at  the  extremities  of  the  long  bones,  as  well  as  the  short  bones, 
contains  many.  Certain  short  bones,  such  as  the  vertebrse,  are 
remarkable  for  the  numerous  nerves  they  receive. 

DEVELOPMENT    OP    BONES. 

The  bones,  before  arriving  at  the  condition  in  which  we  see  them  in  the 
adult  animal,  pass  through  several  successive  phases,  the  study  of  which  consti- 
tutes Osteogemj. 

Nearly  all  the  bones  were  originally  cartilaginous,  those  of  the  roof  of  the 
cranium  and  the  face  being  only  represented  by  fibrous  tissue.  We  will  examine 
the  development  of  these  cartilaginous  and  fibrous  bones. 

A.  Development  of  the  Cartilaginous  Bones. — In  the  embryo  at  an  early  period, 
the  bones  are  composed  of  a  mucous  material  analogous  to  that  which  enters  into 
the  composition  of  all  the  other  organs  ;  this  matter  is  constituted  by  a  mass  of 
embryonic  cells.  Later,  they  become  harder,  white,  and  elastic — that  is,  cartila- 
ginous. Certain  portions  of  the  skeleton  persist  in  this  condition  during  the  life 
of  the  animal.  These  permanent  cartilages  are  found  where  the  bony  skeleton 
must  have  a  certain  amount  of  flexibility,  and  on  the  articular  surfaces. 

The  temporary  cartilages,  like  the  permanent,  have  a  fundamental  amorphous  : 
01  hyahne  substance,  in  which  are  embedded  round  cells  containing  one  or  several 
nuclei.     But  they  soon  undergo  modifications,  which  result  in  giving  to  the 
pieces  they  form  the  hardness  and  structure  of  perfect  osseous  tissue. 

These  modifications  gradually  cause  the  cartilage  to  disappear,  and  to  be 
replaced  by  bony  tissue,  without  the  skeleton  ceasing  for  an  instant  to  preserve 
its  form  and  functions.  The  process  commences  by  calcification  of  the  peri- 
chondrium and  of  the  middle  part  of  the  diaphysis,  which  ensures  the  stability 
of  the  organ.  Then  the  blood-vessels,  which  are  constantly  present  in  temporary 
cartilages,  pass  through  the  diaphysary  nucleus,  ramify,  and  are  directed  in  a 
parallel  manner  towards  the  extremities.  Simultaneously,  the  chondroplasts  are 
arranged  in  parallel  series  in  front  of  the  vessels  (rivulation  of  the  cartilage),  and 
finish  by  merging  into  large,  irregular,  elongated  cavities,  incompletely  separated 
by  bands  of  fundamental  substance  of  the  calcified  cartilage,  designated  the 
directing  lines  of  ossification. 

The  blood-vessels  enter  these  cavities,  carrying  to  their  surface  cells  which 
proliferate,  and  are  differentiated  into  osteoblasts  or  productive  cells  of  bone. 
The  osteoblasts  are  deposited,  layer  upon  layer,  against  the  walls  of  the  spaces 
limited  by  the  lines  of  ossification,  and  form,  by  a  kind  of  secretion,  concentric 
strata  of  the  osseous  fundamental  system  which  surrounds  them  ;  then  the 
osteoblasts  become  osteoplasts.  The  cavities  made  in  the  cartilage  finish  by 
becoming  filled  up,  except  at  the  centre,  where  a  central  cylindrical  space 
remains  (Haversian  canal),  and  a  blood-vessel. 

In  the  extremities  of  the  bones,  where  there  are  no  Haversian  canals,  the 
preparatory  modifications  are  the  same  as  in  the  diaphysis,  only  the  cartilaginous 
cells  collect  in  small  irregular  masses,  and  not  in  parallel  piles.     Each  of  these 


20 


THE  BONES. 


masses  forms  layers  of  bone  substance,  that  finish  by  constituting  the  lamellaB  of 
spongy  tissue  at  the  periphery  and  medullary  tissue  at  the  centre,  to  fill  the 
areola  of  the  latter. 

In  this  way  is  accomplished  the  transformation  of  cartilage  into  bone.     As 
will  have  been  observed,  it  is  not  a  mere  calcification  of  the  cartilaginous  tissue, 
«^A,      but  a  real  substitution  of  bone  tissue,  presentmg  the  following  phases  :  1.  Peri- 
tijfe*^- ,  (  chondrial  and  endochondral  calcification  in  places  (nuclei  or  centres  of  ossifica- 
tion).   2.  Invasion  of  the  centres  of  ossification  by  vessels,  rivulation  of  the 
cartilage.     3.  MedulHzation   of    the    cartilage,    and 
formation   of^  osteoblasts.     4.   Development   of   the 
'Jt^  <^^  .^^^      ■'•  '■ "        bone  tissue,  appearance  of  the  osteoplasts. 

J"^  ^§  e^^   /^:r^  B.  Development  of  the  Fibrous  Bones. — The  bones 

originally  fibrous  are  not  merely  charged  with  lime 
salts  in  order  to  acquire  a  bony  appearance.  They 
do  not  pass  through  a  transitory  cartilaginous  state, 
but  the  phenomena  of  ossification  take  place  in  the 
fibrous  tissue  in  the  following  manner  : — 

The  fasciculi  of  connective  tissue  become  calcified, 
separate  here  and  there  from  one  another  to  form 
spaces,  into  which  blood-vessels  enter  or  osteoblasts 
appear.  To  this  phase  of  medullization  succeeds  the 
phase  of  ossification,  which  is  accomplished  in  the 
same  manner  as  in  the  cartilaginous  bones.  Only 
the  directing  lines  are  represented  by  connective 
fasciculi,  which  later  become  Sharpey's  fibres. 

0.   Progress   of    Ossification. — Ossification    com- 
mences simultaneously  in  several  parts  of  the  skeleton, 
and  in  each  of  the  bones  in  particular— though  not 
throughout  their  entire  extent  at  the  same  time.     On 
CARTILAGE   AT   THE   SEAT  OF  thc  coutrary,  lu  certain  determinate  points  of  the  carti- 
ossiFicATioN,  showing  at  its  lagiuous  or  fibrous  mass,  osseous  tissue  is  developed 
ir^'lsCi:;...'":  c:lr™:  ^Wch,  gradually  extendmg,  ends  by  completely  in- 
each  of  which  is  enclosed  in  a  vadiug  it.    These  points  are  named  nuclei  (or  centres) 
sheath  of  calcified  intercellular  ^f  ossificatiou.     The  nuclei  are  primitive  or  comple- 
mentary.     The    latter,  termed   epiphyses,   are   in  a 
fashion  added  to  the  bone,  and  wholly  or  partly  form  certain' apophyses,    rtjlj* ,  '^' 
Although  these  centres  of  ossification  increase  from  day  to  day,  they  never- 
theless remain  for  a  long  time  independent  of  each  other,  and  are  united  only  by 
cartilage.     When  the  skeleton  is  completely  developed,  the  various  centres  of 
ossification  become  joined  to  each  other,  and  the  entire  bone  forms  one  piece  ; 
there  are  no  longer  any  apophyses. 

Up  to  the  present  time,  attempts  to  discover  the  laws  which  govern  the 
appearance  of  the  centres  of  ossification  have  been  futile  ;  the  size  of  the  bone 
counts  for  nothing  ;  and  the  influence  of  proximity  to  the  centres  of  circulation, 
which  has  been  sometimes  brought  forward  (for  the  sternum,  for  example, 
which  is  never  completely  ossified),  cannot  be  accepted.  The  law  which 
presides  over  the  union  of  the  centres  of  ossification  has  also  been  sought 
for.  A.  Berard  imagined  he  could  formulate  it  in  the  following  proposition  .- 
Of  the  two  extremities  of  along  bone,  it  is  always  that  towards  ivhich  the  nutrient 
foramen  is  directed  that  is  first  united  to  the  body  of  the  bone.     But  to  Berard's 


GENERAL  PRINCIPLES  APPLICABLE  TO  THE  STUDY  OF  ALL  THE  BONES.   21 

law  there  are  nmnerous  exceptions ;  and  in  order  to  demonstrate  that  it  is  not 
absolute,  it  is  sufficient  to  indicate  that  the  direction  of  the  nutrient  foramen 
varies  much,  not  only  in  similar  bones  of  different  species  of  animals,  but  also  in 
similar  bones  of  the  same  species^ ;  and  yet  the  progress  of  ossilication  is  alwajs 
the  same. 

The  period  when  fusion  of  the  epiphyses  terminates  in  the  domestic  animals 
is  still  little  known  ;  fusion  is  evidently  complete  when  growth  is  achieved,  but 
this  period  is  markedly  modified  by  hygiene  and  the  :'ood  animals  receive.  Renault 
and  some  breeders  have  observed,  that  in  the  proocious  breeds  of  cattle  the 
evolution  of  the  teeth  is  more  rapid  than  in  the  common  breeds.  More  recently, 
Sanson  has  affirmed  that  precocity,  characterized  by  this  prompt  dental  evolution, 
is  marked  by  a  more  rapid  fusion  of  the  epiphyses,  and  he  believes  there  is  a 
direct  relation  between  the  evolution  of  the  teeth  and  that  of  the  bones. 
According  to  this  principle,  in  the  Horse  the  fusion  of  the  epiphyses  should 
commence  and  terminate  between  three  and  five  years  of  age. 

Toussaint,  however,  did  not  share  this  opinion.  In  the  Ox,  Sheep,  and 
Horse,  he  remarked  that  the  first  centres  of  ossification  appeared  in  the  body 
of  the  flat  and  the  longbone^and  in  the  centrum  and  arches  of  the  vertebrae. 
When  the  first  half  of  ^esrajtionnad  not  been  passed,  no  other  points  of  ossifica- 
tion were  seen.  It  is  necessary  to  add,  however,  those  of  the  second  and  third 
phalanges  and  the  calcis,  which  comport  themselves  as  long  bones. 

In  the  last  half  of  gestation,  ossification  invades  the  complementary  nuclei,  as 
well  as  the  short  bones  ;  the  exceptions  are  the  pisiform  bone  and  the  inner  condyle 
of  the  humerus  in  the  Calf  and  Foal,  and  the  large  and  small  sesamoid  bones  in 
the  Calf  only.  Ossification  of  these  bones  of  the  skeleton  is  slow.  It  must  also 
be  mentioned  that  at  birth  the  complementary  nuclei  of  the  coxas^  are  not  yet 
visible,  and  they  are  net  seen  until  ten  months  or  a  year  afterwards.   ^^  ^  ""'  ^^^J 

With  regard  to  fusion  of  the  epiphyses,  it  occurs  at  the  following  periods  in 
the  principal  bones  of  the  Horse ;  at  the  twelfth  to  the  fifteenth  month  in  the 
second  phalanx  at  first,  then  in  the  first  phalanx  ;  at  the  fifteenth  to  the 
eighteenth  month  in  the  middle  metacarpal,  afterwards  in  the  metatarsal.  At 
this  age  fusion  also  occurs  at  the  upper  end  of  the  radius  and  inferior  ex- 
tremity of  the  humerus  :  from  twenty  months  to  two  years,  at  the  lower  end  of 
the  tibia  ;  from  three  to  three  and  a  half  years,  at  the  upper  extremity  of  the 
humerus,  at  the  two  ends  of  the  femur,  and  at  the  upper  end  of  the  tibia  ; 
lastly,  about  five  years,  in  the  bodies  of  the  vertebrae  and  in  the  coxae. 

In  the  Ox,  ossification  progresses  at  about  the  same  rate  as  in  the  Horse, 
except  that  there  is  a  little  greater  precocity  in  the  fusion  of  the  epiphyses  of  the 
humerus  and  radius,  which  are  fused  at  the  same  time  as  those  of  the  phalanges, 
and  matacarpal  and  metatarsal  bones.  In  this  animal,  the  two  lateral  halves  of 
the  latter  bones  are  united  before  union  of  the  inferior  epiphysis  to  the  body  of 
the  bone.  The  Sheep  offers  an  interesting  peculiarity,  in  that  the  humero- 
radial epiphyses  are  consolidated  before  those  of  the  phalanges,  and  towards  the 
tenth  month. 

If  the  results  of  these  observations,  made  on  our  principal  domestic  animals, 
are  compared  with  the  evolution  of  the  dental  system,  we  are  compelled  to  con- 
clude, with  Toussaint,  that  fusion  of  the  epiphyses  does  not  commence  at  the 
same  time  as  the  eruption  of  the  first  permanent  teeth.  If  a  relationship  exists 
between  the  evolution  of  the  teeth  and  that  of  the  bones,  it  has  yet  to  be 
demonstrated  in  an  exact  manner. 


22  THE  BONES. 

Toussaint  has  also  studied  the  course  of  ossification  in  the  Bog,  Pig,  and 
Rabbit.  In  the  Dog  at  birth,  none  of  the  complementary  nuclei  have  been 
invaded  by  ossification.  Consequently,  bone  tissue  is  only  found  in  the  dia- 
physis  of  the  long  and  flat  bones.  In  the  thrge  months  after  birth,  the  great 
majority  of  the  epiphyses  commence  to  ossify  ;  and  after  this  period  there  only 
remain  the  pyramidal  bone  and  the  complementary  nuclei  of  the  coxffi,  in  the 
cartilaginous  condition  ;  the  ossification  of  these  latter  commence  at  from  five  to 
six  months. 

The  skeleton  of  the  Rabbit  is,  at  birth,  in  a  condition  almost  identical  with 
that  of  the  Dog  ;  nearly  all  the  epiphysary  nuclei  of  the  humerus  and  that  of 
the  lower  end  of  the  femur,  however,  show  osseous  points. 

In  the  Fig,  at  birth  ossification  is  much  more  advanced  than  in  the  Dog ; 
but  it  is  less  so  than  in  the  larger  Herbivora. 

The  fusion  of  the  epiphyses  has  been  studied  in  the  Dog.  It  commences  at 
five  months,  in  the  phalanges  and  metacarpals,  and  continues  in  the  humerus 
and  radius,  the  corresponding  epiphyses  of  which  are  consolidated  at  nine 
months  ;  at  eighteen  months  there  can  be  distinguished  the  nuclei  at  the  upper 
border  of  the  scapula,  the  upper  end  of  the  humerus,  inferior  extremity  of  the 
radius  and  uhia,  the  epiphyses  of  the  femur,  and  the  bodies  of  the  vertebrae. 
The  latter  facts  support  the  preceding  ones,  and  likewise  demonstrate  that  the 
conclusions  of  Sanson  are  probably  too  absolute. 

Growth  of  the  Bones. 

Bones  increase  by  the  superposition  of  new  elements,  while  the  soft  parts  of 
the  organism  grow  by  the  interposition  of  new  elements  in  the  mass  of  pre- 
existing elements.  The  manner  in  which  this  apposition  of  new  elements  is 
accomplished  is  not  the  same  in  the  long,  the  flat,  or  the  short  bones. 

1.  Long  Bones.  As  a  general  rule,  the  long  bones  elongate  by  the  growth 
and  ossification  of  the  temporary  cartilage  situated  between  the  diaphysis  and 
the  osseous  nuclei  at  the  extremities.  Consequently,  elongation  ceases  when  the 
primitive  or  complementary  nuclei  are  fused  with  one  another.  The  increase  in 
length  in  the  bones  of  the  Ihnbs  does  not  take  place  everywhere  in  the  same 
proportion.  Duhamel,  Flourens,  and  particularly  Oilier  and  Humphry,  have 
remarked  that,  in  the  thoracic  limb,  the  extremity  furthest  removed  from  the 
humero-radial  articulation  grows  fastest ;  while  in  the  abdominal  limb,  the 
extremity  most  distant  from  the  femoro-tibial  articulation  grows  the  least. 

With  regard  to  the  increase  in  thickness  of  the  bone,  this  occurs  by  ossifica- 
tion of  the  deeper  layer  of  the  periosteum — the  osteogenous  lager.  The  experiments 
of  the  authors  just  mentioned  irrefutably  demonstrate  this,  and  those  of  Oilier 
have  even  proved  that  the  periosteum  may  produce  bone  at  a  point  where  it  has 
been  transplanted. 

The  periostic  bone  is  developed  according  to  the  process  of  ossification  in  the 
fibrous  tissue.  In  a  transverse  section  of  the  diaphysis  of  a  growing  long  bone, 
there  is  seen,  as  Laulaine  has  indicated,  concentric  circumferences  united  by 
radii  of  osseous  substance.  The  diaphysary  portion  of  the  periostic  bone  is 
fused  with  the  extremities,  through  the  medium  of  the  ossification  notch  of 
Ranvier — a  prolongation  of  the  periosteum  into  the  articular  enlargement  around 
the  cartilage  of  conjugation.  The  formation  of  bone  tissue  in  the  deeper  layer 
of  the  periosteum  is  very  active  during  the  youth  of  animals,  but  it  soon 
diminishes,  and  ceases  completely  in  advanced  age. 


GENERA  L  PRINCIPLES  A PPLICABLE  TO  THE  STUD  Y  OF  ALL  TEE  BONES.    23 

If  the  phenomena  of  growth  were  not  counterbalanced  by  those  of  absorption, 
long  bones  would  acquire  an  enormous  thickness  and  weight.  But  in  the  first 
period  of  life,  in  proportion  as  new  layers  are  applied  to  the  surface  of  bones,  the 
deeper  parts — those  occupying  the  axis  of  the  diaphysis — disappear  by  absorption. 
In  this  way  the  medullary  canal  is  formed,  and  a  just  proportion  established 
between  the  volume  and  weight  of  the  skeleton. 

When  the  bones  are  completely  formed,  during  the  entire  adult  period  the 
process  of  destruction  is  equal  to  that  of  growth,  so  that  their  weight  and  com- 
position does  not  vary.  At  a  later  period,  absorption  is  greater  than  the  forma- 
tive force,  which  in  old  age  is  altogether  in  abeyance  ;  so  that  the  organic 
matter  of  the  bones  is  rarefied,  and  these  lose  their  elasticity  and  gain  in 
fragility. 

It  has  been  remarked  that  the  development  of  the  bones  is  subordinate,  in 
a  certain  measure,  to  the  activity  and  resistance  of  the  organs  in  their  vicinity. 
Lesshoft  and  Popoff  beheve  that  the  development  of  a  bone  is  in  proportion  to 
the  activity  of  the  neighbouring  muscles,  that  the  pressure  of  external  organs- 
such  as  an  aponeurosis — may  produce  torsion  in  a  bone  and  retard  its  growth, 
so  that  its  greatest  thickness  will  correspond  to  the  point  where  the  surrounding 
Ijf^  resistances  are  at  a  minimum.  Oilier,  however,  has  noted  that  the  long  bones 
i^*^"^  become  more  elongated  when  they  do  not  sustain  pressure  on  their  extremities. 

2.  Flat  Bones. — These  bones  have  sometimes  only  one  primary  nucleus  of 
ossification,  placed  in  the  centre.  They  grow  by  the  increase  of  this  nucleus, 
which  gradually  invades  the  mass  of  the  bone  in  radiating  from  the  centre  towards 
the  periphery.  When  they  have  several  nuclei,  some  of  these  are  at  the  margin, 
and  in  such  a  case  the  bones  increase  by  ossification  of  the  marginal  efpiphyses 
and  growth  of  the  central  nucleus. 

Flat  bones  increase  in  thickness  by  the  formation  of  sub-periosteal  layers, 
and  by  the  development  of  the  spongy  tissue  between  the  two  compact  plates. 

3.  Short  Bones. — These  grow  in  thickness  by  the  progressive  ossification  of 
the  osteogenic  layer  of  the  periosteum ;  and  in  length  by  ossification  of  the 

•  epiphysary  cartilages,  when  they  possess  complementary  nuclei. 

Nutrition  of  Bones. 

The  experiments  which  consisted  in  feeding  young  animals  with  madder,  and 
afterwards  examining  their  osseous  system,  have  for  a  long  period  demonstrated 
the  nutrition  of  bones.  When  bones  cease  to  grow,  nutrition  becomes  less  active  ; 
but  it  is  evident  that  it  does  go  on,  in  order  to  maintain  the  organic  matter  of 
the  osseous  tissue  in  a  proper  condition. 

The  abundance  of  vessels  carrying  blood  to  all  parts  of  the  bone  tissue,  alone 
suffices  to  prove  the  existence  of  a  nutritive  movement  in  these  apparently  stony 
organs. 


THE  BONES. 


CHAPTER   11. 
THE   BONES   OF   MAMMALIA   IN   PARTICULAR. 

Article  I. — Vertebral  Column. 

The  vertebral  column,  or  spine,  is  a  solid  and  flexible  stalk  situated  in  the  middle 
and  upper  part  of  the  trunk,  of  which  it  forms  the  essential  portion.  It  protects 
the  spinal  cord  and  sustains  the  thorax,  as  well  as  the  principal  or2:ans  of  circu- 
lation, respiration,  and  digestion.  Articulated  anteriorly  with  the  head,  and 
terminating  in  a  point  at  its  posterior  extremity,  this  stalk  is  formed  by  a  some- 
what considerable  assemblage  of  short,  single,  tuberous  bones,  to  which  has  been 
given  the  name  of  vertehne.  These  bones,  though  all  constructed  on  a  uniform 
type,  yet  do  not  offer  the  same  configuration  throughout  the  whole  spine.  The 
differences  they  present  in  this  respect  have  permitted  their  being  divided  into 
five  principal  groups  ;  whence  the  division  of  the  vertebral  column  in  five  regions, 
which  are,  enumerating  them  from  before  to  behind  :  1.  Cervical  region.  2, 
Dorsal  region.  3.  Lumbar  region.  4.  Sacral  region.  5.  Coccygeal  region.  The 
first  comprises  seven  vertebrse,  which  serve  as  a  base  for  the  animal's  neck  ;  the 
second  has  eighteen,  against  which  the  ribs  are  placed  ;  the  third  has  only  six, 
which  correspond  to  the  loins  ;  in  the  fourth  there  are  five,  constantly  fused  into 
one  mass  in  the  adult,  to  constitute  a  single  bone — the  sacrum  ;  while  the  fifth 
possesses  a  variable  number  of  small  degenerate  vertebrte,  gradually  decreasing 
in  size  to  form  the  tail.  The  pieces  constituting  the  first  three  regions  are  called 
true  veiieircB  ;  those  of  the  last  two  are  designated /(v/se  vertehrce. 

The  subjoined  table  indicates  the  number  of  vertebrae  in  each  of  the  regions 
of  the  spine,  in  the  horse  and  other  domestic  Mammalia. 


Animals. 

Vertebra. 

Cervical. 

Dorsal. 

Lumbar. 

Sacral. 

COCCTGEAL. 

Horse 

Ox 

Sheep    

Goat 

Camel 

Pig 

Dog 

Cat 

Rabbit 

7 
7 
7 
7 
7 
7 
7 
7 
7 

18 
13 
13 
13 
12 
14 
13 
13 
12 

6  or  5 

6 
6—7 

6 

7 

6—7 

7 

7 

7 

5 
5 
4 
4 
4 
4 
3 
3 
4 

15-18 
16—20 
16—24 
11-12 
15—18 
21-23 
16—21 

21 
16-18 

The  characters  belonging  to  all  these  vertebrae  will  be  first  studied  ;  then  a 
particular  description  of  those  of  each  region  will  be  given  ;  and,  finally,  an 
examination  will  be  made  of  the  spine  as  a  whole. 

Characters  common  to  all  the  Vertebrae. 

Each  of  these  small  bones  is  pierced  from  before  to  behind  by  a  wide  opening — 

the  spinal  foramen.,  or  vertebral  canal ;  whence  results,  for  the  entire  spine,  a  long 

canal  traversing  its  whole  length,  and  which  lodges  a  very  important  portion  of 

the  nervous  centres— the  spinal  cord.     This  canal,  which  traverses  the  vertebrae 


VEBTEBB^.  25 

from  one  end  to  the  other,  transforms  it  into  a  ring  in  which  we  recognize,  for 
facility  of  description,  two  parts — the  one  inferior,  the  other  superior.  The  first, 
or  hotly,  is  very  thick,  and  forms  the  base  of  the  vertebras  ;  the  second,  which 
is  thin,  has  been  designated  spinous  or  spinal — from  one  of  the  pecuUarities  it 
presents,  or  annular — because  it  circumscribes  the  major  portion  of  the  spinal 
foramen.  This  division  is  not  altogether  an  arbitrary  one,  for  the  body  and  the 
annular  portion  constitute,  in  the  foetus,  two  distinct  pieces,  which  do  not  become 
united  for  a  long  time  after  birth. 

Body  {centrum). — The  shape  of  the  body  of  a  vertebra  is  that  of  a  prism 


Fig.  13. 

k 

B      A. 

A 

i 

w. 

•{{ 

ELEMENTS   OF   A   VERTEBRA.      (AFTER   OWEN.) 

A,  Ideal  typical  vertebra ;  B,  Actual  thoracic  vertebra  of  a  bird ;  c,  Centrum  (or 
body),  giving  off,  d,  d,  the  diapophyses,  and  p,p,  the  parapophyses  (transverse  and 
articular  processes) ;  the  neural  arch,  enclosing  the  spinal  cord,  is  formed  by 
n,  n,  the  neurapophyses  (lamince),  saxd  n,  s,  the  neural  spine  {spinous  process); 
the  hamal  arch,  enclosing  the  great  centres  of  the  circulation,  is  formed  by  h,  h, 
the  haemapophyses  (costal  cartilages) ;  and  h,  s,  the  haemal  spine  (sternum). 
From  both  the  neurapophyses  and  haemapophyses  may  be  given  off  the  zygapo- 
physes,  z,  z.  The  lateral  arches,  which  may  enclose  the  vei'tebral  arteries,  o,  o, 
are  completed  by  the  pleurapophyses  (ribs),  pi.  ;  these  in  B  are  bent  downwai-ds, 
so  as  to  form  part  of  the  hasmal  arch,  and  give  off  the  diverging  appendages,  a,  a. 

with  four  faces,  of  which  two  only — the  superior  and  inferior — are  free,  and  can 
be  studied  in  the  adult  ;  the  two  lateral  faces  are  united  and  confounded  with 
the  annular  portion.  This  prism  also  presents  two  extremities — an  anterior  and 
posterior. 

Faces. — The  superior  face,  limited  in  extent,  forms  part  of  the  spinal  foramen, 
constituting  its  floor.  It  exhibits  :  1.  On  the  middle  line,  two  roughened, 
prominent  surfaces,  representing  two  triangles,  whose  summits  are  opposed. 
2.  On  the  sides,  two  depressed  smooth  surfaces,  perforated  by  one  or  more 
openings  that  lead  to  the  interior  of  the  bone.  The  inferior  face  is  divided  into 
two  lateral  portions  by  a  median  crest  (the  htemal  spine). 

Extremities. — The  anterior  has  a  prominent  convex  head,  more  or  less 
detached.  The  posterior  offers  a  cavity  for  the  reception  of  the  head  of  the 
next  vertebra.  These  two  planes — the  one  convex,  the  other  concave — do  not 
come  into  immediate  contact ;  an  elastic,  flexible  fibro-cartila^e,  firmly  attached 
to  each,  is  interposed  between  them. 


26  THE  BONES. 

Annulae  Portion  {neurcd  arch  or  neuropophyses). — This  is  formed  by  an 
osseous  plate  that  curves  suddenly  downwards,  in  the  shape  of  an  arch,  the  two 
extremities  of  which  approach  each  other,  enclose  the  body,  and  become  united 
to  it.  It  offers  for  study  :  1.  An  internal  and  an  external  surface.  2.  An 
anterior  and  &,  posterior  border. 

Surfaces. — The  internal  surface,  concave  and  smooth,  forms,  with  the  superior 
face  of  the  body,  the  spinal  foramen.  The  external,  convex  and  irregular,  pre- 
sents :  1 .  A  single  prominence,  raised  in  the  middle  of  the  superior  portion,  and 
named  the  spinous  process  {neural  spine).  2.  The  transverse  processes  (diapo- 
physes)  are  a  double  pair  of  eminences,  one  on  each  side,  and  projected  trans- 
versely outwards. 

Borders. — The  anterior  border  has  two  articular  facets  looking  upwards  : 
these  are  the  anterior  articular  processes  {prezygopophyses),  right  and  left.  In 
each  is  a  notch  which,  when  placed  in  opposition  to  a  similar  excavation  in  the 
preceding  vertebra,  forms  the  inter vertehrcd  foramen.  The  posterior  border  pre- 
sents the  same  pecuUarities,  with  this  difference,  that  the  articular  faces  of  the 
posterior  articular  processes  {postzygopophyses)  are  inclined  downwards,  to  corre- 
spond with  the  anterior  facets  of  the  succeeding  vertebra.^ 

Structure  of  the  vertebrce.  —The  compact  substance,  which  is  abundant  in  the 
spinous  portion,  forms  in  the  body  an  extremely  thin  layer,  inclosing  a  volumi- 
nous nucleus  of  spongy  tissue.  The  latter  is  traversed  by  numerous  venous 
canals,  which  open  on  the  surface  of  the  bone. 

Development.  —  It  has  been  already  shown  that  the  body  and  spinous 
portion  of  a  vertebra  constitute,  in  yoimg  animals,  two  distinct  pieces.  Each 
was  primarily  formed  from  two  lateral  centres,  which  met  on  the  median  line. 
In  the  body,  the  fusion  of  these  centres  is  so  prompt,  that  it  is  generally  believed, 
perhaps  justly,  that  the  development  of  this  part  of  the  vertebra  proceeds  from 
a  single  centre  of  ossification.  The  union  of  the  two  centres  in  the  annular 
portion,  usually  designated  the  vertebral  lamince  {parapophyses),  is  slower.  It 
commences  in  the  most  anterior  vertebrae,  and  is  latest  in  the  sacral  and  coccy- 
geal regions.  To  the  three  principal  pieces  of  the  vertebra  in  process  of 
ossification,  are  added,  at  a  subsequent  period,  complementary  centres  of  ossifi- 
cation, variable  in  number  according  to  the  regions  and  species  of  animal ; 
there  is  always  one  for  each  of  the  anterior  and  posterior  surfaces  of  the 
vertebral  bodies  ;  while  others,  much  less  constant,  concur  to  form  the  spinous 
and  transverse  processes. 

Characters  proper  to  the  Vertebrae  of  each  Region. 

A  casual  inspection  of  a  vertebra  might  suffice,  strictly  speaking,  to  dis- 
tinguish the  region  of  the  spine  to  which  it  belonged.  For  instance,  a  cervical 
vertebra  is  recognized  by  its  volume,  the  absence  of  a  spinous  process,  and  the 
foramen  which  traverses  the  base  of  its  transverse  processes.  The  dorsal 
vertebra  is  conspicuous  by  its  tubercular  transverse  processes,  and  by  being 
furnished,  outwardly,  with  an  articular  surface,  as  well  as  by  the  depressions  on 
its  body  destined  to  receive  the  heads  of  the  ribs.  The  lumbar  vertebra  has  its 
long  flattened  transverse  processes  ;  while  the  coccygeal  vertebra  offers  rudi- 

('  Vertebrae  which  have  centra  concave  at  both  ends,  are  designated  amphicselous.  Those 
distinguished  by  a  concavity  in  front  and  a  convexity  behind,  are  known  as  procxlous ;  but  if 
the  cavity  is  behind  and  tlie  convexity  before,  they  are  then  named  opisthocxlous.  A  vertebra 
of  the  above  description  belongs  therefore,  to  the  opisthocaslous  class.) 


VEBTEBRM  27 

mentary  laminae  and  processes.  There  is  no  necessity  for  noticing  the  sacrum, 
the  five  pieces  of  which  form  one  bone— a  feature  that  markedly  distinguishes 
it  from  the  other  regions  of  the  vertebral  column.  But  these  few  distinctive 
characteristics  do  not  satisfy  the  requirements  of  descriptive  anatomy  ;  so  that 
it  is  necessary  to  undertake  a  more  extensive  study  of  each  of  these  regions. 

1.  Cekvical  Vertebe^. 
General  Characters. — These  vertebrae,  the  longest  and  thickest  in  the 
spine,  present  generally  a  cubical  form.  They  are  usually  distinguished  from  the 
vertebrae  of  the  other  regions  by  the  following  characters  :  The  inferior  spine  of 
the  body  is  strongly  marked,  especially  behind,  where  it  terminates  in  a  small 
tubercle.  The  head  is  well  detached  from  the  remainder  of  the  bone,  and 
describes  a  very  short  curve.  The  posterior  cavity, 
wide  and  deep,  represents  a  veritable  cotyloid  de- 
pression, which  is  too  large  to  fit  the  head  exactly; 
the  intermediate  fibro-cartilage  on  these  two  sur- 
faces is  also  of  a  great  thickness.  The  spinous 
process  forms  a  simple  roughened,  and  but  slightly 
prominent,  ridge.  The  transverse  processes,  very 
developed,  are  elongated  in  an  antero-posterior 
direction,  and  inclined  downwards.    In  this  region 

they  are  designated  the  trachelian  processes,  be-  ^  cervical  vertebra. 

cause  of  their  relations  with  the  trachea  ;  a  j^  Superior  spinous  process ;  2,  an- 
f oramen  that  traverses  them  from  before  to  terior  articuiaj  processes ;  3,  pos- 
behind  at  their  base  has  been,  for  the  same  f^tr  ^^n^et fac^'^o^Tod^  f 'e!?; 
reason,  named  the  trachelian  foramen  {^vertebral  transverse  processes,  with  their 
foramen).      The    articular  processes,   large    and        tubercles  or  rudimentary  ribs ;  8, 

'  .         ,  -TIT  1  J    •  J  inferior  crest,  or  spine :  9,  concave 

promment,  are  mchned  downwards  and  mwards.        posterior  face. 
The  notches  are  wide  and  deep. 

Specific  Characters. — The  seven  cervical  vertebrae  are  reckoned  from 
before  to  behind,  and  receive  numerical  names  indicating  their  place  in  the 
region. 

First. — The  first  vertebra  of  the  neck,  which  has  been  named  the  atlas,^ 
deserves  a  very  careful  description.  At  first  sight  there  is  recognized  the  great 
development  of  its  transversal  diameter,  the  considerable  dimensions  of  the 
spinal  foramen,  and  the  thinness  of  its  body.  The  intra-spinal  face  of  the  latter 
is  divided  into  two  portions  by  a  transverse  ridge  :  one  anterior,  furnished  with 
hgamentous  imprints,  exhibits,  laterally,  two  deep  excavations,  which  lodge  the 
venous  sinuses  ;  the  other,  posterior,  is  smooth  and  concave  from  side  to  side, 
and  forms  an  articular  surface  into  which  is  received  the  odontoid  process  of  the 
axis  ;  this  surface  takes  the  place  of  the  cotyloid  cavity.  The  inferior  spine  of 
the  body  appears  as  a  large  tubercle  (Fig,  15,  6),  The  head  is  absent,  and  is 
replaced  by  two  concave  facets.  The  anterior  articular  processes  have  their 
gliding  surfaces  looking  downwards  ;  they  are  joined  to  the  two  preceding  facets 
to  constitute  two  large  diarthrodial  cavities,  which  articulate  with  the  occipital 
condyles  (Fig,  15,  1),  There  is  no  spinous  process,  but  a  roughened  surface 
instead.  The  transverse  processes  are  large,  flattened  above  and  below,  inclining 
forwards  and  downwards,  and  are  provided  with  a  thick  rugged  lip.    Posteriorly, 

*  Rudimentary  ribs  are  sometimes  attached  by  ligaments  to  the  ends  of  the  transverse 
processes  (.Leshre). 


28 


THE  BONES. 


Fig.  15. 


atlas;  inferior  sitrface. 
1,  Articular  cavities  for  condyles  of 
the  occipital  bone ;  2,  articulai  facet ; 
3,  vertebral  or  antero-internal  fora- 
men ;  4,  posterior,  or  cervical  fora- 
men ;  5,  transverse  process  or  wing 


quite  at  their  base,  and  on  each  side  of  the  spinal  foramen,  they  show  two  large 
vertical  facets  which  represent  the  posterior  articular  processes  ;  these  facets  are 
uneven,  are  confounded  with  the  articular  cavity 
of  the  upper  face  of  the  body,  and  correspond  to 
the  two  analogous  facets  of  the  axis.  Each  trans- 
verse process  is  pierced  at  its  base  by  two  foramina, 
which  traverse  it  from  below  upwards.  The 
posterior  represents  the  vertebral  foramen  of  the 
other  vertebrae  ;  while  the  anterior  is  continued 
to  the  external  surface  of  the  process  by  a  wide, 
deep,  but  very  short  channel,  running  from  with- 
out to  within,  and  joins  a  third  foramen,  which 
enters  the  spinal  canal.  These  last  two  openings, 
with  the  demi-canal  which  unites  them,  replace 
the  anterior  notch  ;  the  posterior  is  altogether 
absent.  Lastly,  an  inflected  venous  canal,  the 
position  of  which  varies,  and  it  is  also  sometimes 
tubercle  representing  the  inferior  absent,  crosscs  the  lamiuffi  of  the  atlas,  and  opens, 
spinous  process;  7,  superior  arch,  qjj  Qjjg  ^[^q^  j^to  the  Spinal  caual,  and  on  the 

forming  the  roof  of  the  spinal  fora-        ,  ,  ^t    ^^      ^  mi-        ^i 

^gn    ^  other,  beneath  the  transverse  process,     ihe  atlas 

contains  much  compact  tissue,  and  is  generally 
developed  from  six  centres  of  ossification  :  two  for  the  body,  which  at  an  early 
period  becomes  a  solid  piece,  and  two  for  the  annular  part ;  the  other  two  are 
complementary  centres,  each  of  which  forms  one  of  the  two  posterior  undulated 
facets  and  lip  of  the  corresponding  transverse  process. 

Second. — This  is  named  the  axis,  or  dentata  (Fig.  16).     It  is  the  longest  of 

all  the  cervical  vertebrae  ;  those  which 
succeed  it  gradually  diminish  in  length 
and  in  thickness.  The  body  of  the  axis 
has  no  increase  anteriorly,  but  a  conical 
process  termed  the  odontoid,  which  is 
flattened  above  and  below,  concave  and 
rough  from  one  side  to  the  other  on  its 
superior  face  ;  convex  in  the  same  direc- 
tion and  perfectly  smooth  on  its  inferior 
face.  The  latter  represents  an  articular 
half-hinge,  around  which  glides  the  con- 
cave articular  surface  on  the  superior 
face  of  the  body  of  the  atlas.  The 
anterior  articular  processes  are  carried 
to  the  base  and  to  each  side  of  the 
odontoidian  pivot,  in  the  shape  of  two 
undulated  facets,  which  are  confounded  with  the  gliding  surface  of  the  latter, 
the  destination  of  which  has  been  already  noted.  The  spinous  process,  very 
large  and  elongated  antero-posteriorly,  is  divided  behind  into  two  roughened  lips. 
The  transverse  processes  are  slightly  developed,  and  terminate  posteriorly  in  a 
single  tubercle,  directed  backwards.  The  anterior  notches  are  very  deep,  and 
are  most  frequently  converted  into  foramina.  This  vertebra,  although  voluminous, 
is  light,  in  consequence  of  its  containing  much  spongy  substance.  In  the  young 
animal,  the  odontoid  process  and  the  articular  surfaces  on  each  side,  constitute 


Fig.  16. 


THE  AXIS,  OR  dentata;  LATERAL  VIEW. 

1,  Superior  spinous  process ;  2,  odontoid  pro- 
cess; 3,  intervertebral  foramen,  or  hole  of 
conjugation;  4,  body;  5,  inferior  spinous 
process  ;  6,  7,  inferior  and  superior  articu- 
lating processes. 


VERTEBRM  29 

two  centres,  distinct  from  each  other  and  from  the  body  of  the  vertebra.  After 
the  axis,  the  cervical  vertebrae  diminish  in  length  and  increase  in  thickness  ; 
while  the  obliquity  of  their  articular  processes  becomes  more  pronounced  the 
more  distant  they  are  from  that  vertebra. 

Third,  fourth,  and  fifth.— Each,  of  these  has,  at  its  transverse  processes,  two 
prolongations — one  anterior,  the  other  posterior.    The  inferior  face  of  their  bodies 


AXIS    AND   SIXTH    CKRVICAL    OF    THE    HORSE    AND    ASS. 

A.  Axis  of  the  Horse.      1,  spinous  process  ;    2,  transverse  process ;    3,  odontoid  process ; 
4,  lateral  articular  facet. 

B.  Axis  of  the  Ass.     Same  numbers  and  same  signification. 

a',   Sixth  cervical  vertebra  of  the  Horse.     1,  Articular  head  ;  2,  posterior  articular  process  ; 
3.  articular  cavitv  ;  4,  posterior  prolongation  of  the  transverse  process  :   5,  anterior  ditto. 
b',  Sixth  cervical  vertebra  of  the  Ass.     Same  numbers  and  same  signification. 

exhibits  a  median  spine  terminated  posteriorly  by  a  tubercle,  which  gradually 
increases  in  volimie  from  the  third  to  the  fifth  vertebra. 

The  third  presents,  between  its  anterior  and  posterior  articular  processes,  an 
almost  complete  gap  ;  if  its  anterior  extremity  be  placed  on  a  horizontal  plane, 
it  will  touch  that  plane  by  its  articular  and  transverse  processes  and  its  head. 


30  TEE  BONES. 

In  the  fourth,  the  articular  processes  are  united  by  a  thin,  sharp  osseous  plate, 
notched  only  in  front.  Laid  on  a  horizontal  plane,  the  head  remains  some 
distance  from  that  plane.  The  fifth  is  recognized  by  the  continuous,  thick,  and 
rugged  lamina  which  unites  the  articular  processes,  and  by  the  tubercle  of  the 
inferior  spine  on  the  body,  which  is  in  shape  like  the  heart  on  a  playing-card. 

Sixth.— T\n&  is  distinguished  by  the  slight  prominence  of  the  spinous  process, 
but  particularly  by  the  almost  total  disappearance  of  the  inferior  spine,  and  the 
presence  of  a  third  prolongation,  very  strong  and  inchning  downwards  at  its 
transverse  process — a  circumstance  to  which  this  vertebra  owes  its  designation  of 
tricuspid. 

Seventh. — This  has  received  the  name  of  prominens,  because  its  spinous  pro- 
cess, terminating  in  a  point,  is  more  distinct  than  in  the  preceding  vertebrae,  the 
axis  excepted.  It  exhibits,  besides  :  deep  imprints,  which  replace  the  inferior 
spine  ;  a  concave  demi-facet  on  each  side  of  the  posterior  cavity  of  the  articulation, 
of  the  head  of  the  first  rib  ;  a  particular  disposition  of  its  transverse  processes, 
which  are  unituberculous  ;  the  complete  absence  of  the  vertebral  foramen  ;  and, 
lastly,  the  depth  and  width  of  its  notches.  The  spinal  foramen,  which  has 
already  assumed  a  somewhat  considerable  diameter  in  the  sixth  cervical  vertebra, 
is  still  larger  in  the  seventh. 

Ass. — The  cervical  vertebra3  in  this  animal  much  resemble  those  in  the 
Horse.  Studying  them  more  closely,  however,  it  is  possible  to  discover  certain 
differences  which  distinguish  them  from  those  of  the  other  Equidfe.  Thus,  the 
rugosities  on  the  arch  of  the  atlas  are  much  less  marked  than  in  the  Horse,  and 
form  a  kind  of  thick  depressed  tubercle.  The  vertebral  foramen  is  very  large 
in  proportion  to  the  size  of  the  vertebra,  and  the  canal  uniting  the  two  portions 
of  the  anterior  foramen  of  the  transverse  process  is  deep  and  protected  by  a 
well-defined  rim.  The  axis  has  a  less  elevated  spinous  process  than  that  of  the 
Horse  ;  its  upper  border,  nearly  parallel  with  the  transverse  process,  is  more 
deeply  divided  into  two  lips,  and  the  summit  of  its  transverse  process  extends, 
backwards  to  the  articular  process,  while  in  the  Horse  it  does  not  go  beyond  the 
origin  of  the  latter.  In  the  third,  the  lamina  uniting  the  two  prolongations  or 
points  of  the  transverse  processes,  is  notched  behind  the  anterior  prolongation, 
instead  of  being  notchless  as  in  the  Horse.  In  the  fourth  Siud  fifth  this  notch  is 
still  more  marke4.  In  every  instance  the  anterior  prolongation  of  the  transverse 
process  is  always  more  detached  and  better  circumscribed  in  the  Ass  than  in  the 
Horse.  The  same  remark  applies  to  the  tricuspid ;  the  posterior  prolongation  is 
also  better  detached,  and  the  middle  prolongation  extends  nearly  to  the  articular 
cavity  of  the  vertebra — a  prolongation  which,  in  the  Horse,  does  not  exceed  one- 
half  the  length  of  the  posterior  one.  The  seventh  differs  little  from  that  of  the 
Horse  ;  nevertheless,  the  uni-tubercular  transverse  process  has,  in  front,  a  small 
sharp  projection  which  resembles  somewhat  the  anterior  prolongation  of  the 
bicuspid  processes. 

In  the  Mule  and  Hinny,  the  cervical  vertebrae  hold  the  middle  place  between 
those  of  the  Ass  and  the  Horse. 

Differential  Characters  of  the  Cervical  Vertebra  in  the  other  Domesticated 

Animals. 

A.  Ox,  Sheep,  and  Goat. — The  cervical  vertebrae  of  these  animals  differ  from  those  of 
Solipeds  by  their  shortness,  and  the  greater  development  of  their  insertion  eminences.  In  the 
Sheep  and  Goat  they  are  relatively  longer  than  in  the  Ox.     The  transverse  processes  of  the 


VERTEBRA.  31 

atlas  are  less  inclined  than  in  the  Horse,  and  have  no  vertebral  foramina ;  the  posterior  facets 
for  articulation  with  the  axis,  are  nearly  flat  and  join  each  other.  The  axis  has  a  semi-cylindri- 
cal, not  a  conical,  odontoid  process,  which  is  so  concave  on  its  upper  t^urface  that  it  looks  like 
a  groove.     Its  spinous  process  is  not  so  thick  as  in  the  Horse,  and  is  not  bitid  posteriorly. 

In  the  Jive  succeeding  vertebras,  a  rugged  continuous  lamina  unites  the  anterior  articular 
processes  to  the  posterior.  The  spinous  process  inclines  forward,  and  is  flattened  transversely 
at  its  summit,  which  is  sometimes  bifid  ;  it  progressively  increases  in  height  from  the  third  to 
the  fifth  vertebra. 

In  the  sixth,  the  transverse  processes  have  only  two  prolongations — a  superior  and  inferior; 
the  latter,  large  and  flattened  on  both  sides,  is  bent  abruptly  downwards.  The  spinous  process 
has  already  attained  the  height  of  1|  to  2  inches  in  this  vertebra,  and  is  flattened  laterally. 

The  seventh  well  deserves  the  name  of  prominens,  its  spinous  process  being  no  less  than 
from  4  to  4f  inches  (see  Figs.  6  and  7). 

B.  Camel.— In  the  Camel,  the  cervical  vertebrae  are  longer  and  thinner  than  in  the  other 
large  domestic  animals.  Altogether,  they  form  oue-third  of  the  total  length  of  the  spine. 
Their  vertebral  lamiiise  are  deeply  notched  before  and  behind,  which  allows  them  to  easily 
enter  tlie  spinal  canal.  Their  articular  processes  are  convex,  and  from  the  second  to  the  sixth 
inclusively,  the  vertebral  foramen  is  small  and  deeply  placed  in  the  laminae. 

The  atlas  is  distinguished  from  that  of  the  Horse  and  Ox  by  the  absence  of  the  tubercle  on 
the  inferior  face  of  the  body,  and  the  shortness  of  the  transverse  processes,  of  which  the  border 
is  thin  and  sharp.  The  vertebral  foramen  makes  a  somewhat  long  course  in  the  transverse 
process  of  this  vertebra,  and  opens  at  the  bottom  of  the  excavation  in  which  the  anterior  inter- 
vertebral foramina  meet — the  latter  being  double. 

The  axis  is  very  long  and  constricted  in  its  middle ;  the  inferior  crest  is  only  slightly 
salient ;  there  are  ilouble  invertebral  foramina,  the  largest  of  which  is  divided  by  a  bony 
septum ;  the  odontoid  process  is  as  in  the  Ox.  The  other  cervical  vertebrae  gradually  diminish 
in  size  and  increase  in  thickness  from  before  to  behind. 

In  the  third,  fourth,  and  fifth,  the  transverse  processes  are  bi-tuberculated. 

In  the  sixth,  the  transverse  process  is  a  wide  and  thick  plate,  inclining  downwards. 

The  seventh  is  recognized  by  its  long  spinous  process  and  the  smallness  of  its  transverse 
process,  which  has  a  larger  and  more  obvious  vertebral  foramen  than  the  other  vertebras 
(see  Fig.  8). 

C.  Pig. — Of  all  the  domesticated  animals,  this  has  the  shortest,  the  widest,  the  most 
tuberous,  and  consequently  tlie  strongett  cervical  vertebrae.  The  body  of  these  bones  has  no 
crest  on  the  inferior  face  ;  the  head,  but  little  detached,  is  scarcely  round,  and  looks  as  if  driven 
back  on  itself;  consequently,  tiie  posterior  cavity  is  not  deep.  The  vertebral  laminae  are  very 
narrow,  and  scarcely  extend  from  one  part  of  the  vertebra  to  the  other  in  the  superior  portion, 
so  that  the  spinal  canal  appears  at  this  point  to  be  incomplete. 

In  the  atlas,  the  transverse  processes  are  less  inclined  than  in  Ruminants ;  the  vertebral 
foramen  is  not  constant,  and  when  it  exists,  opens  on  one  side,  under  the  transverse  process, 
and  on  the  other,  on  its  posterior  margin,  after  pursuing  a  certain  tiack  in  the  substance  of 
the  bone. 

The  odontoid  process  of  the  axis  is  constricted  at  its  base.  This  verte*bra  is  distinguished 
by  its  high  and  thin  spinous  process  inclining  slightly  back,  by  its  transverse  processes  being 
but  slightly  prominent,  and  perforated  by  an  enormous  vertebral  foramen. 

In  the  four  succeeding  vertebrae,  the  spinous  process  terminates  in  a  blunt  point,  and  inclines 
forward ;  slightly  salient  in  the  first,  it  gradually  rises  in  the  others.  The  transverse  processes 
form  two  prolongations :  one,  the  superior,  is  tuberous,  and  is  joined  to  the  anterior  articular 
process  by  a  plate  of  bone,  which  is  pierced  by  a  foramen ;  the  other,  the  inferior,  flattened  on 
both  sides,  bent  downwards,  and  large,  as  it  belongs  to  a  posterior  vertebra,  transforms  the 
inferior  face  of  these  vertebral  bodies  into  a  large  groove.  The  seventh  has  a  spinous  process 
as  long  as  those  of  the  dorsal  region.  A  peiforated  bony  plate,  as  in  the  preceding  vertebrae, 
unites  the  anterior  articular  process  to  the  single  tubercle  composing  the  transverse  process; 
the  latter  is  continued  back  nearly  to  the  posterior  notch  by  a  second  plate,  also  perforated 
with  a  foramen  (see  Fig.  3). 

D.  Dog  and  Cat. — In  these  animals,  the  cervical  vertebrae  are  long  and  thick,  and  much 
resemble  those  of  Solipeils.  Nevertheless,  besides  their  smaller  volume,  they  are  distinguished  : 
1.  By  the  disposition  of  their  corresponding  articular  surfaces  ;  the  anteiior,  or  head,  is  nearly 
flat,  and  is  even  slightly  excavated  in  its  centre ;  the  posterior,  or  cavity,  is  l.ut  little  hollowed 
to  receive  the  head  of  the  next  vertebra;  2.  By  the  width  of  the  vertebral  laminae,  which 
overlap  one  another;  3.  By  the  height  of  their  spinous  processes,  which  increases  as  the 
vertebrae  extend  back  ;  4.  By  the  great  extent  of  the  anterior  and  posterior  articular  processes, 


32  THE  BONES. 

which  are  united  by  means  of  a  continuous  and  very  salient  bony  plate,  that  considerably 
augments  the  transversal  diameter  of  each  vertebra. 

In  the  atlas,  the  articular  surface  for  the  odontoid  pivot  is  confounded  in  front  with  the 
cavities  which  correspond  to  the  occipital  condyles.  The  two  facets  which  are  annexed 
posteriorly  to  this  articular  surface,  instead  of  being  plane  or  gently  undulated,  as  in  the 
other  domesticated  animals,  are  transformed  into  real  glenoid  cavities.  The  triinsverse  pro- 
cesses are  carried  directly  outwards  and  a  little  backvvanl ;  the  lip  wljicli  borders  eacli  is 
slightly  raised ;  of  the  two  foramina  wiiich  replace  the  anterior  notch,  one  only  exists,  and 
this  penetrates  to  the  interior  of  the  spinal  canal ;  the  other  is  merely  a  simple  notch. 

In  the  axis,  the  odontoid  process  is  cylindrical,  narrow  at  its  base,  and  bent  a  little  upwards ; 
the  lateral  facets  of  this  eminence  represents  true  condyles.  The  spinous  process  is  very  thin 
and  undivided,  and  is  curved  forward  above  the  laminae  of  the  atlas.  The  anterior  notches  are 
never  converted  into  foramina. 

The  third  cervical  vertebra  is  the  largest  :  and  the  succeeding  ones  gradually  diminish  in 
thickness  to  the  last,  contrary  to  what  occurs  in  the  other  species.  The  seventh  does  not  show 
the  spinous  process  so  developed  as  in  Ruminants  and  Pachyderms  (see  Figs.  3,  4,  7). 

E.  Rabbit. — The  cervical  vertebrae  in  this  animal  somewhat  resemble  those  in  the  Cat, 
though  they  differ  in  certain  general  and  particular  characters.  Thus,  in  the  Rabbit  they 
become  larger  as  they  proceed  backward  ;  the  atlas  has  its  transverse  processes  horizontal,  and 
they  are  narrow  at  their  oriain  ;  the  axis  has  a  bifid  tubercle  at  the  posterior  extremity  of  its 
spinous  process,  and  a  notch  below  it ;  the  succeeding  vertebrae  are  thin ;  the  fourth,  fifth,  and 
sixth  are  trifid  in  their  transverse  processes ;  and  the  seventh  has  a  short  spinous  process. 


2.  DoESAL  Vertebe^  (Fig.  18). 

Geneeal  Chaeacters. — In  the  dorsal  vertebrae  the  body  is  very  short,  and 
in  front  has  a  large  slightly  projecting  head ;  behind,  it  has  a  shallow  cavity. 
Laterally,  these  vertebrae  present,  at  the  base  of 
the  transverse  processes,  four  concave  articular 
Jacets,  the  two  anterior  of  which  are  situated  near 
the  head,  while  the  posterior  two  are  hollowed  out 
of  the  border  of  the  articular  cavity  of  the  body. 
Each  of  these  facets  is  joined  to  an  analogous 
facet  on  the  neighbouring  vertebra  to  form  a 
small  excavation,  into  which  is  received  the  head 
(or  capitulum)  of  the  corresponding  rib.  The 
spijious  process  is  very  high,  is  compressed  on 
both  sides,  inclines  backwards,  and  its  summit 
is  terminated  by  a  tubercle.  The  transverse 
processes  are  unitubercular,  and  directed  obliquely 
outwards  and  upwards  ;  on  their  external  aspect 
they  have  a  diarthrodial  plane  facet  which  corre- 
sponds to  the  tuberosity  (or  tuberculum)  of  the 
rib  (and  may  therefore  be  named  the  tubercular 
transverse  process).  The  articular  processes  are 
narrow,  and  constitute  simple  unrelieved  facets 
cut  on  the  base  of  the  spinous  process.  The 
posterior  notches  are  deep,  and  sometimes  con- 
verted into  foramina. 

Specific  Charactees. — None  of  the  eigh- 
teen dorsal  vertebrae  differ  much  from  the  type 
just  described  ;  and  it  is  difficult  to  establish 
special  characters  for  each.  It  is,  nevertheless 
possible  to  assign  to  a  dorsal  vertebra,  approximately,  the  rank  it  should  occupy, 
in  accepting  the  following  facts  as  a  guide  :   1.  The  vertical  diameter  of  the 


ttpe  op  a  dorsal  vertebra  (the 
fourth). 

1,  Body,  2,  2,  articular  facets  for  the 
head  of  the  rib;  3,  articular  facet  for 
tuberosity  of  the  rib;  4,  articular 
processes  ;  5,  spinal  foramen ;  6, 
tuberous  base  of  spinous  process; 

7,  posterior  articular  face  of  body ; 

8,  8,  transverse  processes ;  9, 
superior  spinous  process  ;  10,  an- 
terior articulation  of  body. 


TEE   VERTEBRA. 


vertebral  bodies  augments  progressively  from  before  to  behind.  Their  lateral 
diameter,  which  determines  that  of  the  spinal  canal,  becomes,  on  the  contrary, 
less  from  the  first  to  the  tenth  vertebra  ;  after  which  it  assumes  increasing 
proportions  to  the  last  one.  The  articular  surfaces,  which  serve  for  the  mutual 
contact  of  head  and  cavity,  become 
larger  and  shallower  in  proportion 
as  the  vertebrae  are  more  posterior. 
The  inferior  spine  on  the  body  is 
very  salient  and  tuberculated  in  the 
two  first  vertebrae,  very  acute  in  the 
third  and  fourth  ;  it  disappears  in 
the  sixth  and  ninth,  to  reappear  and 
become  more  marked  from  the  tenth 
to  the  last.  2.  The  intervertehral 
cavities,  intended  for  the  reception 
"of  the  heads  of  the  ribs,  diminish 
in  depth  and  extent  from  the  first  to 
the  last.  3.  The  longest  spi^ious  pro- 
cess belongs  to  the  third,  fourth, 
and  fifth  vertebra  ;  those  which 
follow  gradually  decrease  to  the 
eighteenth.  Their  width  diminishes 
from  the  second  to  the  eighth  :  it 
afterwards  increases  in  a  progressive 
manner  in  the  succeeding  vertebrfe  ; 
from  the  second  to  the  tenth  vertebra, 
the  summit  of  the  spinous  process  is 
large  and  tuberculated  ;  in  the  last 
seven  it  is  flattened  laterally.  Their 
obliquity  is  less  marked  as  they  pro- 
ceed backwards  ;  in  the  sixteenth  and 
seventeenth  vertebrae,  the  spinous 
process  is  nearly  vertical  ;  it  inclines 
slightly  forward  in  the  eighteenth. 
Those  of  the  tenth,  eleventh,  and 
twelfth  vertebrae  are  slightly  curved 
like  an  S.  4.  The  articular  processes, 
from  the  first  to  the  tenth  vertebra, 
gradually  contract  and  approach  the 
median  line ;  in  the  succeeding 
vertebrae  they,  on  the  contrary, 
increase,  and  become  concave  and 
wider  apart  from  those  of  the  oppo- 
site side.  5.  The  volume  of  the  transverse  processes  and  the  size  of  their  diarthrodial 
facets,  diminish  from  before  to  behind.  In  the  three  first  vertebrte  this  facet  is 
concave  ;  in  the  first  nine  the  articular  facet  looks  outwards  and  backwards, 
while  the  facet  on  the  body  looks  forwards  ;  in  the  last  the  two  facets  are 
directed  forwards.  These  two  facets  are  generally  confounded  in  the  seventeenth 
and  eighteenth  vertebrae.  The  first  dorsal  vertebra  much  resembles  the 
prominens ;    it  is  distinguished  from  it,  however,  by  the  presence  of  four 


MIDDLE    DORSAL    VERTEBRA    OF    THE    HORSE, 
VIEWED    FROM    THREE    TYPICAL    LINES. 

The  first  line,  A  B,  passes  from  before  to  behind  by 
the  most  salient  point  of  the  transverse  process, 
intersecting  the  middle  of  the  lateral  facet  in- 
tended for  the  tuberosity  of  the  rib,  and  of  the 
cavity  on  the  border  of  the  posterior  articular 
surface  of  the  body.  Below  is  the  intervertebral 
foramen,  the  spinous  process,  and  the  articular 
facets  on  the  base  of  the  latter.  The  line  c  D 
is  tangent  to  the  summit  of  the  transverse  pro- 
cess and  head  of  the  vertebra ;  it  intersects  the 
anterior  articular  processes.  The  line  M  N  is 
horizontal,  and  tangent  to  the  inferior  face  of 
the  body. 


9i 


TEE  BONES. 


diarthrodial  facets  on  its  extremities.  It  also  differs  from  the  other  vertebrae  by 
the  shortness  of  its  spinous  process,  which  terminates  in  a  point ;  by  the  size  and 
prominence  ,of  its  articular  processes  ;  and  by  the  depth  of  its  notches.  The 
last  vertebra  never  has  facets  on  the  contour  of  its  posterior  cavity. 

Ass. — Besides  the  smaller  volume  of  the  vertebrse,  the  following  differential 
characters  will  serve  to  distinguish  these  bones  in  this  animal :  1.  The  spinous 
processes,  as  far  as  the  tenth  vertebra,  are  a  little  more  inclined  backwards  than 


Fig.  20. 


A   DORSAL    VERTEBRA    OF   THE    HORSE    AND    ASS   (THE    ELEVENTH). 

A,  Vertebra  of  the  Horse  {anterior  face).     1,  Head  ;  2,  spinous  process ; 
3,  3,  transverse  processes. 

B,  Vertebra  of  the  Ass  (anterior  face).    Same  description  as  for  the  horse. 
a',    Vertebra  of  the  Horse  (lateral  face).     1,  Head  ;  2,  spinous  process  ; 

3,  transverse  process. 
b',    Vertebra  of  the  Ass  (lateral  face).     Same  description  as  for  the  horse. 


in  the  Horse,  while  the  inclination  forward  of  the  latter  is  equally  marked  ;  the 
anterior  part  of  the  summit  of  the  spinous  process  is  in  contact  with  a  horizontal 
plane,  when  the  three  last  vertebrae  of  the  Ass  are  laid  on  their  anterior  portion. 
2.  From  the  first  to  the  tenth,  the  summit  of  the  transverse  processes  lies  behind 
the  margin  of  the  anterior  articular  facets  in  the  Ass,  while  it  is  beyond  them 
from  the  fourth  in  the  Horse.  From  the  eleventh  to  the  thirteenth,  the  projection 
of  the  transverse  processes  is  equal  to  that  of  the  anterior  articular  facets  in  the 


THE   VERTEBRA.  35 

two  species  ;  then  the  processes  become  predominant  in  the  Ass  (Fig.  20, 
A',  B',  3,  3),  and  they  preserve  this  character  to  the  eighteenth.  3.  All  the 
transverse  processes  are"  less  oblique  than  those  in  the  Horse  ;  also  the  line  which 
intersects,  in  the  middle,  the  summit  of  these  processes  and  their  lateral  articular 
facet,  passes  always  in  front  of  the  posterior  facet  on  the  body  ;  in  the  Horse, 
this  line  traverses  the  latter  facet,  except  in  the  first  and  fifth  vertebra  (Fig.  20, 
A.  B).  4.  There  are  not  seen  on  the  nine  last  dorsal  vertebrse  of  the  Ass,  the 
anterior  articular  facets  ascending  to  the  base  of  the  spinous  process,  as  usually 
occurs  in  the  Horse.  5.  Lastly,  the  notches  of  the  intervertebral  foramina  are 
nearly  always  closed  by  a  bony  bridge  in  the  Ass,  and  only  rarely  so  in  the  Horse. 
The  dorsal  vertebrae  in  the  Mule  and  Hinny  off"er  the  same  mixture  of 
particular  characters  which  are  found  in  their  parents  ;  though  it  is  not  doubtful 
that  the  vertebr^  of  the  Mule  (Hinny)  produced  by  the  union  of  the  female  Ass 
-with  the  Stallion  Horse,  more  resemble  the  former  than  the  latter,  especially 
in  the  transverse  processes. 

Differential  Characters  in  the  Dorsal  Vertebrae  of  other  Animals. 

A.  Ox.— In  the  Ox,  these  thirteen  bones  are  longer  and  thicker  than  in  the  Horse.  Their 
flpinous  processes  are  larger  and  incline  more  backward ;  their  transverse  processes  are  very- 
voluminous,  and  are  provided  with  a  convex  facet  from  above  to  below  ;  while  their  posterior 
notclies  are  nearly  always  converted  into  foramina. 

Considered  individually,  they  are  more  slender  in  the  middle  than  at  the  extremities.  Their 
spinous  processes  diminish  in  width,  especially  at  their  summits,  from  the  first  to  the  eleventh 
vertebra,  and  widen  again  in  the  two  last ;  they  progressively  increase  in  slope  to  the  tenth, 
after  which  they  become  more  and  more  upright;  tlie  first  four  are  the  longest,  and  are  nearly 
the  same  in  height ;  the  others  gradually  decrease. 

In  the  first  four  or  five  vertebrae,  the  articular  facet  of  the  transverse  processes,  while 
retaining  its  vertical  convexity,  is  concave  in  an  antero-posterior  direction.  This  facet  is 
always  absent  in  the  last  vertebra,  and  sometimes  even  in  the  preceding  one.  The  two  bones 
terminating  the  dorsal  region  show,  in  addition,  the  articular  processes  disposed  like  those  of 
"the  lumbar  vertebrae. 

B.  Sheep  and  Goat.— The  thirteen  dorsal  vertebrae  of  the  Sheep  and  Goat  are  relatively 
less  strong  than  those  of  the  Ox;  their  spinous  processes  are  not  so  wide,  and  their  posterior 
notches  are  never  converted  into  foramina. 

C.  Camel.— The  dorsal  vertebrae  of  the  Camel,  twelve  in  number,  are  remarkable  for  the 
length  of  their  bodies,  and  the  height  and  width  of  their  spinous  processes.  The  transverse 
processes  are  a  little  less  detached  than  in  the  Ox,  but  they  are  very  tuberous.  The  posterior 
notclies  are  narrow,  deep,  and  close  to  the  base  of  the  spinous  processes;  they  do  not  form 
foramina.  The  convexity  or  concavity  of  the  articular  surfaces  of  the  body  diminishes  from  the 
first  to  the  last  bone;  while  the  spinous  processes  increase  in  length  and  width  from  the  first 
to  the  sixth,  and  diminish  in  the  last  six.  These  processes  are  much  inclined  from  the  third 
to  the  ninth ;  then  they  gradually  become  erect  in  the  last  three. 

D.  Pig.— The  Pig  has  fourteen  dorsal  vertebrae,  which,  in  their  general  disposition,  are 
not  unlike  those  of  the  Ox.  As  with  that  animal,  the  intervertebral  foramina  are  double,  each 
-vertebral  lamina  being  perforated  laterally  by  an  opening  situated  in  front  of  the  posterior 
notch.  In  addition,  the  vertebrae  of  the  Pig  present  this  peculiarity,  that  their  transverse 
processes  are  generally  traversed  at  the  base  by  a  single  or  multiple  foramen,  which  communicates 
with  the  preceding. 

With  regard  to  the  special  characters  proper  to  some  of  the  vertebrae,  these  are,  as  with  the 
other  animals,  very  few,  and  may  be  described  as  follows:  I.  The  transverse  processes  of  the 
four  vertebrae  preceding  the  last  project  but  slightly.  2.  In  the  fourteenth  this  process 
resembles  those  of  the  lumbar  vertebrae.  3.  The  articular  facet  of  the  transverse  process  in  the 
four  last  vertebrae  is  confounded  with  the  anterior  lateral  facet  corresponding  to  the  head 
of  the  rib.  4.  The  articular  processes  of  the  last  five  vertebrae  are  arranged  like  those  of  the 
lumbar  vertebrae ;  and  the  prominence  formed  by  the  tubercle  on  the  outside  of  the  anterior 
articular  process  replaces,  to  a  certain  degree,  the  transverse  process  of  these  vertebrae. 

E.  Dog  and  Cat.— These  animals  have  thirteen  dorsal  vertebrae  formed  on  the  same  model 


36  TEE  BONES. 

as  those  of  the  Horse ;  but  their  spinous  processes  are  in  general  narrower  and  thicker.  The 
tenth  always  has  its  spiuouss  process  vertical,  triangular,  and  terminated  in  a  sharp  point.  The 
last  three  liave  no  posterior  facets  tor  tJie  articulation  of  tlie  heads  of  the  ribs,  and  exhibit,  in 
the  conformation  of  their  articular  processes,  the  same  disposition  as  the  lumbar  vertebrae.  In 
the  Cat,  the  transverse  processes  of  the  three  last  dorsal  vertebrae  are  thin,  sharp,  and  turned 
backwards ;  they  never  possess  facets  for  the  tuberosity  of  the  ribs. 

F.  Rabbit. — The  twelve  dorsal  vertebrae  of  this  animal  are  similar  to  those  of  the  Cat. 
But  the  spinous  process  of  the  first  nine  is  thinner  and  more  oblique,  while  that  of  the  three 
last  is  higher  and  thinner  than  in  the  Cat.  Besides,  the  transverse  process  is  continued,  in 
the  Rabbit,  by  a  triangular  portion  which  increases  the  width  of  the  vertebral  lamina.  The 
inferior  face  of  the  body  is  more  hollowed  in  its  middle  portion,  and  the  inferior  crest  is  more 
salient  than  in  the  Cat. 

3.  Lumbar  Vertebra  (Figs.  21,  22). 

General  Characters. — A  little  longer  and  wider  than  the  dorsal  vertebrae, 
which  they  resemble  in  the  arrangement  of  their  bodies,  these  vertebrae  are 
characterized  :  1.  By  their  short,  thin,  and  wide  spinous  processes,  which  are  slightly 
inclined  forwards,  and  are  provided  at  their  summits  with  a  scabrous  tubercle. 

2.  By  their  largely  developed  trans- 
^'S-  21-  verse  processes,  flattened  above  and 

below,  and  directed  horizontally 
outwards.^  3.  By  the  salient  an- 
terior articular  pit'ocesses,  hollowed 
out  on  each  side,  and  provided  ex- 
ternally with  a  tubercle  for  inser- 
tion. 4.  By  their  equally  prominent 
posterior  articular  processes,  rounded 
in  the  form  of  a  half -hinge. 

Specific    Characters.  —  The 
LUMBAR  VERTEBRA  (FRONT  VIEW).  charactcristics  which  may  serve  to 

1.  Body ;  2,  its  articular  face ;  3,  superior  spinous  distinguish  these  Vertebrae  from 
process ;  4,  spinal  foramen  ;  5,  anterior  articular  Qjjg  another,  are  derived  from  the 
processes ;  6,  6,  tran>verse,  or  costiform  processes ;      ,      t  ,      ,  .  -,    , 

7,  posterior  articular  process.  oody,  and  the  spmous  and  trans- 

verse processes.  1.  From  the  first 
to  the  last  there  is  a  progressive  diminution  in  the  vertical  diameter  of  the  bodies, 
and  an  increase  in  their  transverse  diameter.  The  inferior  spine  on  the  body 
becomes  shorter  and  wider  from  the  first  to  the  last  vertebra  ;  in  the  six  vertebrae 
it  resembles  an  elongated  triangle,  the  summit  of  which  is  directed  forwards. 

2.  The  spinous  processes  decrease  in  width  from  before  to  behind,  and  their 
anterior  border  becomes  more  and  more  concave  ;  their  summits  are  thickened 
and  tuberculated  in  the  three  first,  and  thin  and  sloping  forward  in  the  three  last. 

3.  The  transverse  processes  are  longer  in  the  middle  vertebrae  than  in  those  placed 
before  and  behind.  The  processes  in  the  first  and  second  vertebrae  incline  slightly 
backward  ;  in  the  third  they  are  more  upright ;  and  in  the  succeeding  ones  they 
are  directed  a  little  forward.  In  the  last  two  they  are  remarkable  for  their  thick- 
ness ;  in  the  fifth  an  oval-shaped  articular  facet  is  observed  on  their  posterior 
])order  ;  in  the  sixth,  two  are  present — one  in  front,  corresponding  to  the  pre- 
ceding, and  one  behind,  slightly  concave,  meeting  a  similar  facet  on  the  sacrmn. 
The  fourth  and  fifth  vertebrae  very  often  correspond,  at  their  transverse  processes, 
by  means  of  analogous  facets. 

'  Rudimentary  ribs  are  sometimes  found  attached  by  ligaments  to  the  extremities  of  the 
transverse  processes  (Lesbre). 


THE  VERTEBR^\ 


37 


Fig.  22. 


According  to  Sanson,  five  is  the  natural  number  of  lumbar  vertebrae  in  the 
specific  type  of  African  Horses  (see  remarks  on  the  Spine  in  General).  The 
transverse  processes  in  these  animals  also  offer  some  peculiarities.  Thus  the 
increase  in  their  length  ceases  at  the  second,  and  from  this  an  almost  insensible 
diminution  occurs  to  the  fifth.  The  transverse  processes  of  the  first  lumbar  ver- 
tebra are  alone  less  inclined  backward  ;  they  are  perpendicular  to  the  direction 
of  the  body  in  the  second  and  third,  and  inclined  forward  in  the  fourth  and  fifth. 

The  thoroughbred  English  Horse  has  sometimes  five,  sometimes  six  lumbar 
vertebrae,    but    in    every    instance    the 
lumbar    region    is    comparatively  short 
(Cornevin). 

Ass. — The  lumbar  vertebrae  in  the 
Ass,  five  in  number,  are  easily  distin- 
guished from  those  of  the  Horse  by  the 
characters  special  to  their  spinous  and 
transverse  processes,  and  articular 
tubercles. 

1.  The  spinous  processes  are  propor- 
tionately longer  that  those  of  the  Horse, 
and  they  are  also  more  inclined  forward. 
If  their  bodies  rest  on  a  horizontal  plane, 
and  if  a  line  be  drawn  tangent  to  the 
posterior  border  of  the  spinous  process, 
an  acute  angle  is  always  obtained  at  the 
point  of  junction  of  the  line  and  plane  ; 
but  if  this  be  done  with  the  vertebras  of 
the  Horse,  there  is  at  least  a  right  angle. 

2.  The  transverse  processes  increase 
in  length  from  the  first  to  the  second  ; 
they  are  nearly  equal  in  the  second  and 
third,  and  decrease  suddenly  in  the  ffth. 
They  are  usually  inclined  downwards  ;  their  posterior  border  and  superior  face, 
near  the  body,  are  marked  by  a  vasculo-nervous  furrow,  which  is  scarcely  visible 
in  the  Horse.  Finally,  it  is  not  rare  to  find  no  inter-transverse  articulation 
between  the  two  last. 

3.  The  most  important  differential  character  is  observed  in  the  articular 
tubercules.  The  diarthrodial  facets  are  surmounted  by  a  flat  tongue  of  bone, 
which  is  projected  outwards  in  the  direction  of  the  summit  (see  Fig.  23,  A,  B,  4, 
4).  This  piece  gradually  becomes  lower  from  theirs;*  to  the  fifth  vertebra  ;  in  the 
first,  it  projects  beyond  the  articulation  by  more  than  one-fourth  of  an  inch,  and, 
up  to  a  certain  point,  resembles  the  condition  observed  in  the  Rabbit  or  Dog. 

In  the  Mule  there  are  sometimes  six,  sometimes  only  five,  lumbar  vertebras. 
These  have  the  spinous  and  transverse  processes  somewhat  as  in  the  Horse  ;  their 
articular  tubercles  resemble  those  of  the  Ass. 

In  the  Hinny,  of  which  opportunity  has  rarely  been  had  for  study,  Goubaux 
and  ourselves  have  found  five  lumbar  vertebrae,  which,  in  their  shape,  much 
resembled  those  of  the  Ass. 


UPPER  SURFACE  OF  LUMBAR  VERTEBRAE. 

,  SuQimit  of  spinous  process ;  2,  2,  anterior 
articular  jirocesses  ;  3,  3,  posterior  articu- 
lar processes ;  4,  4,  transverse  processes. 


Differential  Characters  in  the  Lumbar  VERTEBRiE  of  other  Animals. 
A.  Ox,  Sheep,  and  Goat. — The  six  lumbar  vertebrae  of  the  Ox  are  longer  and  thicker 
than  those  of  the  Horse.     The  transverse  processes  are  also  generally  more  developed,  are 


38  THE  BONES. 

coDcave  on  the  anterior  border,  convex  on  the  posterior,  and  incline  slightly  downward,  with 
the  exception  of  the  two  first,  which  remain  nearly  horizontal.  They  increase  in  length  from 
the/r«<  to  the  fourth  vertebra ;  in  the  latter  and  the  fifth,  they  are  nearly  of  the  same  dimensions ; 
in  the  last  they  suddenly  become  shorter.  Their  width  gradually  decreases  from  before  to  beliind. 
In  the  fifth  and  sixth  vertebrae,  these  processes  have  no  articular  facets  between  them  and  the 
sacrum,  these  being  only  met  with  in  Solipedd.  The  articular  processes  are  prominent,  and 
further  removed  from  the  median  line  as  they  belong  to  posterior  vertebrae. 
« 

Fig.  23. 


A  LUMBAR  VERTEBRA  OF  THE  HORSE  AND  ASS. 

A,  Lumbar   vertebra  of  the  Horse  {anterior  face).      1,  Head ;    2,  2,  transverse  processes ; 
3.  spinous  process  ;  4,  4,  articular  tubercles. 

B,  Lumbar  vertebra  of  the  Ass  {anterior  face).     Same  description  as  for  the  horse. 


In  the  Goat  the  transverse  processes  are  more  inclined  downwards. 

In  the  Sheep,  on  the  contrary,  the  processes  of  the  six  or  seven  vertebrae  ascend  towards 
their  extremities. 

B.  Camel. — Apart  from  number,  which  is  seven,  the  lumbar  vertebrae  of  this  animal  offer 
nearly  the  same  features  as  those  of  the  Ox. 

C.  Pig.— The  lumbar  vertebrae  of  the  Pig  greatly  resemble  those  of  ruminant  animals.  It 
commonly  happ(  ns  that  seven  are  met  with ;  but  in  this  case  the  supplementary  vertebra  is 
generally  a  sacral  one.  It  is  not  denied,  however,  that  seven  lumbar  vertebrae  may  exist  in  the 
Pig,  along  with  the  normal  number  of  sacral  vertebrae. 

D.  Dog  and  Cat.— In  the  Dog  and  Cat,  the  lumbar  vertebrae,  seven  in  number,  are 
remarkable  for  their  strength,  due  to  their  length,  thickness,  and  the  development  of  the 
eminences  for  insertion.     The  spinous  process  is  low,  and  becomes  acute  in  the  last  vertebra. 


TEE  VERTEBRA.  39 

The  transverse  processes  incline  very  much  forward  and  downward  ;  they  become  longer  from 
the  first  to  the  second-last  bone ;  in  the  latter  they  become  contracted,  and  in  the  seventh 
vertebra  they  are  still  more  diminislied,  and  terminate  in  au  obtuse  point.  The  tubercle  of  the 
anterior  articular  process  is  extremely  prominent,  and  the  posterior  notches  are  surmounted  bv 
a  small,  very  acute  prolongation,  directed  backwards,  which  becomes  more  developed  towards 
the  anterior  vertebrae.  This  small  prolongation  exactly  represents  the  transverse  process  of  the 
dorsal  vertebrae. 

E.  Rabbit.— They  are  stronger  than  those  of  the  Cat,  and  the  first  three  have  on  the  lower 
surface  of  their  bodies  a  very  salient  crest,  which  simulates  a  real  inferior  spine ;  the  others 
have  a  median  crest  which  gradually  decreases  towards  the  last  bone.   The  tubercle  surmount- 


Fig.  24. 


LUMBAR  VERTEBRA  OF  THE  CAT  AND  RABBIT. 

A,  Second,  third,  and  fourth  lumbar  vertebrcB  of  the  Cat  (inferior  face}.  1,  1,  1, 
TraDsverse  processes  ;  2,  2,  2,  crest  on  the  inferior  face  of  the  body;  3,  articular 
tubercles  of  the  first  vertebra. 

B,  Second,  third,  and  fourth  lumbar  vertebra  of  the  Babbit  (inferior  face}.  1,  2, 
Same  signification  as  in  preceding. 

C,  Third  lumbar  vertebra  of  the  Cat  (lateral  face}. 
prolongation;  2,  ditto  posterior  prolongation;  3, 
4,  4,  posterior  ditto;   5,  spinous  process. 

D,  Third  hcmbar  vertebra  of  the  Babbit  (lateral  face}. 
prolongation  ;    2,  ditto  posterior  prolongation ; 


1,  Transverse  process,  anterior 
I,  anterior  articular  tubercles; 

1,  Transverse  process,  anterior 
,  anterior  articular   tubercle : 


4,  4,  posterior  articular  tubercles  :  5,  spinous  process. 

ing  the  posterior  notches  is  more  developed  than  in  the  Cat.  The  spinous  process  is  prolonged 
backward  by  a  translucent  bony  plate,  wliich  disappears  in  the  last  two.  The  anterior  articular 
tubercles  are  more  developed,  more  erect,  and  nearer  the  median  line,  than  in  the  Caruivora. 
Lastly,  the  transverse  processes  are  relatively  longer,  and  those  of  the  first  are  remarkable  for 
the  notched  enlargement  they  offer  at  their  free  extremities. 


4.  Sacrum  (Fig.  25). 

The  sacrum  results,  as  already  stated,  from  the  consolidation  of  five  vertebrse. 
This  single  bone  articulates,  in  front,  with  the  last  lumbar  vertebra  ;  behind, 
with  the  first  coccygeal  bone,  and  on  the  sides  with  the  ossa  innominata.  It  is 
triangular,  flattened  above  and  below,  and  from  before  to  behind  describes  a 
slight  curve  upwards.  It  offers  for  study  a  superior  and  an  inferior  face,  two 
borders,  a  base,  a  summit,  and  a  central  canal — the  extension  of  the  spinal  canal. 

Faces. — The  superior  face  presents,  on  its  middle,  the  spinous  processes  of  the 


THE  BONES. 


sacral  vertebrae,  which  together  constitute  what  is  called  the  sacral  or  supersacral 
spine.  These  processes  are  united  at  their  base  only,  and  remain  isolated  for  the 
remainder  of  their  extent ;  they  all  incline  backwards  and  terminate,  with  the 
exception  of  the  first,  by  a  tuberous  summit,  which  is  often  bifid  ;  their  length 
diminishes  from  the  second  to  the  fifth  bone.  On  each  side  of  the  sacral  spine 
exists  a  groove,  at  the  bottom  of  which  are  four  openings — the  super-sacral Jara- 
raina.  These  orifices  open  into  the  spinal  canal,  and  communicate  with  four 
analogous,  but  wider  apertures,  pierced  at  the  inferior  face  of  the  bone,  and  for 

this  reason  named   the   sub-sacral 
Fig-  25.  foramina.       The    inferior    face    is 

smooth,  and  shows  traces  of  the 
N^L        ,m^''''.      J^S&^fi^^^^  '''•■'  primitive  separation  of  the  vertebral 

^^■-^'"^^^P^^^^^^^i^mS^  V  bodies ;     the   sub-sacral    foramina, 

~       '  '  ^  which    represent,   with   the   corre- 

sponding super-sacral  openings,  the 
intervertebral  foramina  of  the  other 
regions  of  the  spine,  are  observed 
on  this  surface. 

Borders. — The  hvo  borders,  thick 
and  concave,  form,  posteriorly,  a 
rugged  lip ;  in  front,  they  present 
an  irregular  surface  inclining  ob- 
liquely from  above  to  below,  from 
within  outwards,  and  from  before 
to  behind.  This  surface,  which  is 
intended  for  the  articulation  of  the 
sacrum  with  the  ossa  innominata,  is  divided  into  two  parts  :  one,  the  inferior — 
named  in  Man  the  auricular  facet — is  slightly  undulated  and  diarthrodial ;  the 
other,  the  superior,  serves  for  ligamentous  insertions. 

Base. — This  offers  :  1.  On  the  median  line,  the  anterior  orifice  of  the  sacral 
canal,  and  the  anterior  articular  surface  of  the  body  of  the  first  sacral  vertebra, 
which  is  oval  and  slightly  convex.  2.  On  the  borders,  the  articular  processes  and 
anterior  notches  of  this  vertebra,  as  well  as  the  elliptical  and  somewhat  convex 
facets  which  bring  it  into  contact  with  the  transverse  processes  of  the  last  lumbar 
vertebra. 

Siimmit. — The  summit,  thrown  back,  presents  :  1.  The  posterior  orifice  of  the 
sacral  canal.  2.  The  posterior  articular  surface  of  the  body  of  the  last  sacral 
vertebra.  3.  The  vestiges  of  the  articular  processes  and  posterior  notches  of  that 
vertebra. 

Sacral  canal. — This  is  the  portion  of  the  spinal  canal  which  is  channeled  out 
of  the  sacrum  ;  it  is  triangular,  and  diminishes  in  width  from  before  to  behind. 

The  sacrum  of  the  Ass  much  resembles  that  of  the  Horse  ;  nevertheless,  it  is 
possible  to  distinguish  it  by  the  shape  of  the  articular  tubercles  of  the  first  sacral 
vertebrae,  which  resemble  those  of  the  articular  tubercles  of  the  lumbar  region, 
and  the  traces  those  tubercles  have  left  between  the  sacral  vertebra3,  especially 
between  the  first. 


LATERAL  VIEW  OF  SACRUM. 

1,  Articular  surface  of  body ;  2,  3,  articular  surfaces 
corresponding  to  those  on  the  transverse  processes 
of  the  last  lumbar  vertebra;  4,  spinal  foramen;  5, 
auricular  facet;  6,  anterior  articular  processes; 
7,  inferior  or  sub-sacral  foramina ;  8,  superior 
spinous  processes ;  9,  summit  or  coccygeal  ex- 
tremity. 


Differential  Characters  in  the  Sacral  Vertebra  op  other  Animals. 

A.  Ox. — The  sacrum  of  the  Ox  is  more  voluminous  and  curved  than  that  of  the  Horse 
The  spinous  processes  are  entirely  consolidated,  and  are  surmounted  by  a  thick  rugged  lip ; 


THE   VERTEBRAE.  41 

they  are  bordered  at  their  base  and  on  each  side  by  a  ridge  that  represents  the  rudiments  of  the 
articular  processes.  The  lateral  borders  are  sharp  and  bent  downwards.  The  surfaces  that 
serve  to  unite  the  sacrum  to  the  ossa  innominata  have  a  somewhat  vertical  direction.  There 
are  no  lateral  facets  on  the  base  of  the  bone,  for  the  union  of  the  sacrum  with  the  transverse 
processes  of  the  last  lumbar  vertebra. 

B.  Sheep  and  Goat. — In  the  Sheep  and  Goat,  the  sacrum  is  shorter ;  sometimes  the  con- 
solidation of  the  spinous  processes  is  late,  or  never  occurs. 

C.  Camel. — Sacrum  short  ancl  composed  of  four  vertebrae;  broad  and  curved  on  its  inferior 
face.  The  spinous  processes,  rather  low,  are  strong  and  free  throughout  their  extent.  The 
auricular  facets  are  cut  very  obliquely. 

D.  Pig. — This  is  formed  by  four  vertebrae,  which  are  a  long  time  in  becoming  fused 
together ;  and  it  is  often  difficult  to  discover  where  the  sacrum  ends  and  the  coccyx  begins.' 
The  spinous  processes  are  entirely  absent.  The  vertebral  laminae  are  not  consolidated ;  so  that 
the  spinal  canal  is  half  cut  through  in  its  upper  portion,  as  in  the  cervical  region  ;  this  canal  is 
also  much  compressed  above  and  below. 

E.  Dog  and  Cat. — The  three  vertebrae  which  form  the  sacrum  of  Carnivora  are  early  con- 
solidated. The  sacral  spine  constitutes  a  thin  sharp  ridge,  while  the  lateral  surfaces  for 
articulation  with  the  ossa  innominata  are  turned  quite  outwards,  and  are  nearly  vertical. 

F.  Rabbit. — Relatively  longer  than  tliat  of  Carnivora,  the  sacrum  of  this  animal  is  remark- 
able for  the  presence  of  four  vertebrae,  the  spinous  processes  of  which  are  isolated  from  each 
other. 

5.  Coccygeal  Vertebe^. 

The  coccygeal  region,  or  coccyx,  comprises  from  fifteen  to  eighteen  degenerate 
vertebrae,  which  gradually  diminish  in  thickness  from  the  first  to  the  last.  In  the 
first  three  or  four,  nearly  all  the  characteristics  of  true  vertebrae  are  found  ;  they 
show  a  vertebral  foramen,  a  body,  a  spinous  process,  and  transverse  processes, 
directed  backwards  ;  the  articular  processes  only  are  altogether  absent.  In  the 
succeeding  vertebrae,  these  characters  become  effaced  ;  the  vertebral  laminte  do  not 
join  completely,  and  the  vertebral  canal  is  only  a  simple  groove,  which,  gradually 
decreasing  in  depth,  at  last  entirely  disappears.  The  insertion  eminences  also 
become  less  salient,  and  the  coccygeal  vertebrae  are  soon  reduced  to  small  bony 
cylinders,  narrow  in  the  middle  and  wider  at  both  extremities,  with  a  convex 
articular  surface  at  each  end  (except  the  last,  which  has  only  one  articular  surface). 
These  small  cylinders — the  last  traces  of  the  vertebral  bodies — are  each  developed 
from  three  centres  of  ossification  ;  they  are  very  spongy  and  light.  The  first 
coccygeal  vertebra  is  frequently  consolidated  with  the  sacrum  in  aged  animals. 

Differential  Characters  of  the  Coccygeal  Bones  in  other  Animals. 

A.  Ox,  Sheep,  and  Goat. — In  proportion,  the  coccygeal  vertebrae  of  ruminants  are  stronger 
and  more  tuberous  than  those  of  the  Horse.  The  anterior  articular  processes  exist  in  a  rudi- 
mentary condition. 

B.  Camel. — Fifteen  to  eighteen  in  number,  they  are  not  so  strong  and  are  less  tuberous 
than  in  the  Ox.     The  first  six  are  channeled  by  a  triangular  canal. 

C.  Pig. — These  vertebrae  in  tlie  Pig  are  more  particularly  distinguished  by  the  presence  of 
articular  processes,  by  means  of  which  the  foremost  bones  correspond  with  each  other. 

D.  Dog  and  Cat. — In  these  animals,  the  vertebrae  of  the  coccyx  are  very  strong  and 
tuberous.  The  first  five  or  six  are  as  perfect  as  the  true  vertebrae,  and  comport  themselves  in 
every  respect  like  them.  The  last  are  small  V-shaped  bones,  which  M.  Goubaux  has  described 
by  the  name  of  hypMoid  bones. 

E.  Rabbit. — The  coccyx  of  the  Rabbit  is  analogous  to  that  of  the  Cat. 


'  This  can  always  be  made  out,  however,  by  consulting  the  disposition  of  the  articular  pro- 
cesses. Thus,  in  the  sacral  vertebrae  these  eminences — if  we  except  the  anterior  ones  of  the 
first  and  the  posterior  of  the  last — never  exist  except  in  a  rudimentary  state ;  while  in  the  other 
five  coccygeal  vertebrae  they  reappear  with  all  their  characters. 


12  THE  BONES. 

The  Spine  in  General. 

The  vertebral  column  has  now  to  be  considered  in  its  entirety,  and  examined 
successively  in  its  superior  face,  its  inferior  face,  its  lateral  faces,  and  its  spinal 
canal.     Afterwards  its  direction  and  mobility  will  be  noticed. 

Superior  surface. — This  presents,  on  its  median  line,  the  series  of  spinous  pro- 
cesses. But  little  salient  in  the  cervical  region,  these  eminences  are  much 
developed  in  the  dorsal  and  lumbar,  where  they  constitute  a  long  crest — the 
dorso-Iumbar  spine,  as  well  as  in  the  sacrum,  where  they  form  the  sacral  spine. 
They  soon  disappear  in  the  coccygeal  vertebrae.  Outwards,  and  on  each  side  of 
these  processes,  is  seen  a  succession  of  tubercles  for  insertion,  represented  iu  the 
cervical  and  lumbar  vertebrae  by  articular  processes,  and  in  the  dorsal  vertebrae 
by  the  superior  or  rugose  portion  of  the  transverse  processes.  These  tubercles 
are  disposed  in  line,  and  separated  from  the  spinous  processes  by  a  channel 
designated  the  vertebral  groove,  which  is  more  or  less  deep  and  wide.  It  is  on 
these,  and  on  the  spinous  processes,  that  the  extensor  muscular  fascicuU  of  the 
spine  receive  the  greater  portion  of  their  fixed  or  movable  insertions. 

Inferior  surface. — Wide  at  the  neck,  this  surface  becomes  narrow  in  the  dorsal 
region,  to  be  again  widened  at  the  lumbo-sacral  region,  and  once  more  contracted 
at  the  coccyx.  Crests  more  or  less  developed,  which  divide  the  vertebral  bodies 
into  two  lateral  portions,  right  and  left,  are  remarked. 

Lateral  surfaces. — These  offer  for  study  the  thirty-six  intervertebral  foramina, 
through  which  the  spinal  nerves  pass.  They  exhibit  besides,  in  the  neck,  the 
transverse  processes  ;  in  the  back,  the  external  facets  of  these  processes,  and  the 
intervertebral  facets,  all  destined  to  sustain  the  heads  of  the  ribs  ;  on  the  loins, 
the  transverse  or  costiform  processes.  It  may  be  remarked  that  the  ribs  and  the 
transverse  processes  of  the  neck  and  loins  furnish  points  of  insertion  to  the 
powerful  muscles  which  produce  the  lateral  movements  of  the  spine.  In  the  sacrum, 
the  lateral  faces  are  formed  for  the  articulation  of  the  spine  with  the  ossa 
innominata. 

Spinal  canal. — This  canal  communicates,  in  front,  with  the  cranial  cavity. 
Very  wide  in  the  atlas,  for  the  reception  of  the  odontoid  process  and  to  permit 
the  rotatory  movements  of  the  head  without  injury  to  the  spinal  cord,  this  canal 
suddenly  diminishes  in  the  axis.  It  again  dilates  at  the  termination  of  the 
cervical  region  and  the  commencement  of  the  dorsal ;  there  the  spinal  cord 
presents  a  greater  volume,  and  the  movements  of  the  spine  are  very  extensive. 
Towards  the  middle  of  the  back,  the  spinal  canal  offers  its  smallest  diameter  ;  it 
widens  from  this  part  to  the  lumbo-sacral  articulation  ;  after  which  it  contracts 
rapidly,  and  disappears  altogether  near  the  fourth  or  fifth  coccygeal  vertebra. 
The  lumbo-sacral  dilatation  coincides  with  the  enlargement  of  the  cord  in  this 
region,  and  with  the  enormous  quantity  of  nerves  lying  beside  it. 

Direction  of  the  Spine.— The  spine  does  not  extend  in  a  straight  line  from  the 
head  to  the  posterior  extremity  of  the  body.  If  it  is  followed  from  the  caudal 
extremity — which  is  free  and  looks  downwards — to  the  anterior  extremity,  it  will 
be  observed  that  it  passes  upwards  and  forwards,  forming  a  convex  inflexion 
corresponding  to  the  roof  of  the  pelvis.  In  the  lumbar  and  posterior  half  of  the 
dorsal  region,  it  is  nearly  horizontal  and  rectilinear  ;  thence  it  descends  to  the 
cervical  region,  where  it  again  rises  and  forms  two  curves — one,  posterior,  bend- 
ing upwards,  the  other  anterior,  passing  downwards.  This  direction  "of  the  spine 
gives  it  the  form  of  a  console. 


THE   VERTEBRA.  43 

MoMity  of  the  Spine. — In  the  cervical  region,  the  almost  total  absence  of 
spinous  processes,  the  great  development  of  the  articular  processes,  and  the  very 
short  curve  described  by  the  surfaces  of  contact  of  the  vertebral  bodies,  allow 
the  spine  very  extensive  and  varied  movements.  In  the  dorsal  region,  however, 
these  movements  are  very  limited,  the  spinous  processes  and  the  costal  arches 
preventing  the  play  of  the  vertebrae  on  each  other.  In  the  lumbar  region,  the 
spine  can  be  flexed  and  extended  more  than  in  the  dorsal ;  but  its  lateral  move- 
ments are  quite  as  restricted,  owing  to  the  presence  of  the  transverse  processes  and 
the  reciprocal  union  or  dovetailing  of  the  articular  processes.  Lateral  motion  is 
even  rendered  impossible  in  the  posterior  half  of  this  region,  from  the  manner 
in  which  the  transverse  processes  are  adapted  to  each  other.  It  may  be  remarked, 
however,  that  this  disposition  singularly  favours  the  integral  transmission  of  the 
propulsive  efforts  communicated  to  the  trunk  by  the  posterior  extremities. 

The  sacral  vertebrae,  having  to  afford  the  ossa  innominata  a  solid  fixed  point, 
could  not  preserve  their  independence  and  mobility  if  they  were  like  the  other 
vertebrae  ;  they  are  consequently  consolidated  into  a  single  piece,  which  fulfils  all 
that  is  required  of  it  in  this  respect.  In  the  coccyx  the  spine  again  recovers  its 
mobility,  and  to  an  extent  more  marked  than  elsewhere  ;  the  bones,  articulating 
with  each  other  by  means  of  convex  surfaces,  and  having  no  long  processes  at 
their  extremities,  are  placed  in  the  best  possible  conditions  for  effecting  varied 
and  extensive  movements. 

Varieties  in  the  Vertebral  Column. 

To  anatomists,  the  bones  of  the  spine  have  frequently  offered  curious  varieties 
in  their  shape  and  number. 

1.  Shape. — Goubaux  has  observed  varieties  of  this  kind  in  the  last  two  cervical 
vertebrae  of  the  Horse.  In  one  instance,  the  sixth  had  the  transverse  process 
biscuspid  on  the  left  and  tricuspid  on  the  right.  This  anatomist  has  collected 
several  similar  examples.  Husson  has  found  the  sixth  cervical  vertebra  with  a 
prolongation  deficient  in  the  transverse  processes  ;  and  the  seventh,  on  the  con- 
trary, with  an  additional  prolongation. 

The  dorsal  vertebra  have  also  exhibited  varieties  in  shape.  Daubenton  has 
referred  to  the  skeleton  of  an  Ass,  in  which  the  last  vertebra  had  on  one  side 
only  a  transverse  process  like  that  of  the  lumbar  vertebrae.  We  have  seen  this 
variation  in  the  Horse. 

In  the  lumbar  region,  Goubaux  has  noticed — as  we  have  done — the  fourth  and 
fifth  vertebrae  sometimes  articulating  by  their  transverse  processes  ;  the  articula- 
tions may  even  be  fused.  Sometimes  the  transverse  processes  of  the  first  lumbar 
vertebra  articulate  at  their  base  with  the  body  of  the  bone,  and  become  floating 
ribs. 

Thomas  has  remarked  an  interesting  variation  in  the  sacrum.  He  found  in 
the  Sheep  a  long,  costiform,  transverse  process  on  one  of  the  sides  of  the  first 
sacral  vertebra.  The  last  vertebra  in  this  region  sometimes  shows,  in  the  Dog — • 
either  to  the  right  or  left,  or  on  both  sides  at  the  same  time— one  or  more  articular 
facets  on  the  transverse  processes,  uniting  with  similar  facets  on  the  first  coccygeal 
bone  (Goubaux). 

2.  Number. — For  a  long  time,  instances  have  been  accumulating  of  variations 
in  the  number  of  bones  in  the  spine  ;  but  they  do  not  form  a  very  imposing 
array,  probably  because  it  is  difficult  to  observe  them  without  making  a  special 
and  attentive  study  of  the  subject. 


41  THE  BONES. 

These  variations  have  been  noted  in  all  the  regions  of  the  vertebral  column, 
though  they  are  rare  in  the  cervical  region.  Sometimes  they  consist  in  a  dimi- 
nution, sometimes  in  an  increase,  in  the  number  of  the  vertebrse. 

a.  So  far  as  it  is  known,  a  decrease  in  the  nimiber  of  the  cervical  vertebrae 
in  the  domestic  animals  has  not  been  observed.  Goubaux  has  sometimes  met 
with  eight  cervical  vertebrae,  though,  as  the  eighth  offered  relations  with  the  first 
rib,  he  was  disposed  to  place  it  in  the  dorsal  region.  In  this  case  the  anomaly  was 
in  the  number  of  bones  in  the  spine. 

b.  The  dorsal  region  is  more  frequently  abnormal.  Bourgelat  and  Rigot 
have  dissected  Horses  which  had  only  seventeen  dorsal  vertebra.  Groubaux  and 
ourselves  have  seen  similar  instances,  though  the  length  of  the  animals  afforded 
no  suspicion  of  modification  in  their  spines.  It  is  certainly  more  common  to  see 
the  nimiber  of  dorsal  vertebrae  increased  to  nineteen,  as  is  proved  by  the  observa- 
tions of  Bourgelat,  Higot,  Husson,  Goubaux,  and  our  own. 

This  increase  is  observed  also  in  the  asinine  species.  We  have  the  skeleton 
of  an  Ass  in  which  there  are  twenty  ribs  on  each  side,  and  therefore  twenty 
dorsal  vertebrae.     In  the  Ox,  fourteen  dorsal  vertebrae  have  been  found. 

c.  The  lumbar  region  is  still  more  frequently  modified.  The  Horse  at 
times  has  only  five  lumbar  vertebrae  (Daubenton,  Chauveau,  Goubaux,  Sanson, 
and  several  German  anatomists)  ;  the  Ass  only  four  (Goubaux).  In  the  other 
animals — the  Dog,  for  example — an  increase  in  nunlber  has  been  remarked  ; 
Girard  has  seen  eight  lumbar  vertebrae,  instead  of  seven.  Goubaux  and  ourselves 
have  on  several  occasions  seen  seven  lumbar  vertebrse  in  the  Sheep. 

d.  The  sacrum  has  often  one  or  two  pieces  more  in  old  subjects,  due  to 
the  fusion  of  the  first  or  second  of  the  coccygeal  vertebrae  with  its  posterior 
extremity.  At  other  times,  the  supernumerary  piece  is  situated  at  the  base. 
Earely  is  the  number  of  sacral  vertebrae  diminished  ;  Goubaux  has  only  met  with 
one  instance  in  which  there  were  four  sacral  vertebrae  in  the  Horse. 

e.  The  number  of  coccygeal  bones  is  extremely  variable  ;  and  in  order  to 
be  convinced  of  this,  one  has  only  to  look  at  the  tables  drawn  up  by  anatomists. 
Nevertheless,  it  is  certain  that  the  normal  number  is  never  less  than  seven  or 
eight,  as  Bourgelat  stated  in  the  first  edition  of  his  Anatomie. 

To  resume,  it  is  seen  that  all  the  regions  of  the  spine  may  offer  variations  in 
the  number  of  vertebrte,  and  that  these  variations — rare  between  the  neck  and 
the  back — are,  on  the  contrary,  frequent  at  the  two  extremities  of  the  lumbar 
region.  When  the  bones  are  deficient,  the  diminution  is  only  apparent — that  is, 
the  vertebra  which  is  absent  in  one  region  is  carried  to  the  adjoining  region.  It 
frequently  happens,  for  instance,  when  a  lumbar  vertebra  is  missing,  that  the 
sixth  is  united  to  the  sacrum  ;  or  when  there  are  nineteen  dorsal  vertebrae,  there 
is  one  less  in  the  lumbar  region.  It  is  not  always  sufficient  to  examine  the 
regions  contiguous  to  the  one  which  is  modified,  to  gain  an  exact  notion  as  to  the 
modification.  In  fact,  a  change  in  the  number  of  vertebrae  in  a  region  may  be 
compensated  for  by  an  alteration  in  a  distant  region.  In  the  museum  of  the 
Lyons  school,  there  is  the  skeleton  of  an  Ox  in  which  there  are  fourteen  dorsal 
vertebrae,  with  the  normal  number  of  cervical,  but  only  four  sacral.  We  also 
possess  the  skeleton  of  a  Horse  which  has  seven  lumbar  vertebra,  with  the  normal 
number  in  the  other  regions,  though  the  seventh  bone  is  certainly  the  first  sacral, 
as  it  has  all  its  characteristics  ;  and  with  regard  to  the  fifth  sacral  bone,  this 
evidently  comes  from  the  coccygeal  region.  In  the  first  skeleton,  the  increase 
in  the  dorsal  region  has  therefore  been  com^imsated  for  by  a  decrease  in  the  sacral 


THE   VERTEBRA.  45 

region  ;  and  in  the  second,  the  augmentation  in  the  lumbar  region  has  been  com- 
pensated for  by  a  diminution  in  the  coccygeal  region. 

These  transpositions  occur  more  especially  on  the  confines  of  the  dorso-lumbar 
and  lumbo-sacral  regions. 

But  the  increase  or  decrease  in  the  normal  number  of  vertebrae  is  sometimes 
absolute.  Goubaux  and  Husson  have  found,  in  the  Horse,  nineteen  dorsal 
vertebrae  with  the  normal  number  of  the  other  vertebrae.  The  Ass  with  twenty 
ribs  already  mentioned,  had  the  usual  number  of  vertebras  in  the  other  regions. 
The  first-named  anatomist  has  counted,  under  the  same  conditions,  seven  lumbar 
vertebrae  in  the  Sheep.  Hering,  Rueff,  Leyh,  Sanson,  etc.,  have  found  five  lumbar 
vertebrae  in  the  Horse,  without  any  modifications  in  any  other  parts  of  the 
vertebral  column.  Sanson  has  even  remarked,  that  in  several  oriental  Horses 
there  are  generally  only  five  lumbar  vertebrae.  The  presence  of  this  anomaly  is 
always  allied  to  a  particular  shape  of  the  cranium  and  face.  In  the  estimation 
of  Sanson,  these  characters  are  so  important  that  they  serve  to  distinguish  specific 
types.  The  specific  type  with  five  lumbar  vertebrae  is  pecuHar  to  north-east 
Africa,  probably  Nubia, 

It  is  not  intended  in  this  place  to  discuss  the  opinions  of  Sanson  and  the 
value  of  his  specific  types,  but  merely  to  remark  that  the  number  of  vertebrae  is  very 
liable  to  variation  in  each  region  of  the  spine,  and  that  these  variations  are  even  so 
frequent  in  animals  of  the  same  origin,  that  it  would  be  perhaps  premature  to 
attribute  to  the  number  of  vertebra  in  a  given  region  the  value  of  an  absolutely 
specific  character. 

It  has  been  attempted  to  explain  these  variations  by  an  ancestral  influence, 
or  by  the  influence  of  surroundings  and  exercise.  But  why  might  they  not  be 
the  consequence  of  irregularities  in  the  fusion  of  the  nuclei  which  constitute  the 
vertebral  column  of  the  foetus  ?  Fol  has  observed  that  at  the  fifth  week  the 
human  embryo  has  thirty  such  pieces,  and  that  at  the  sixth  week  the  thirty- 
eighth,  thirty-seventh,  and  thirty-sixth  vertebrae  have  become  one,  while  the 
thirty-fifth  has  no  longer  perfect  limits — so  that  an  embryo  measuring  nineteen 
millimetres  has  only  thirty-four  vertebrae.  The  spine  of  the  embryo  is  com- 
posed, therefore,  of  a  larger  number  of  pieces  than  that  of  the  adult.  The 
reduction  in  number  is  due  to  fusions ;  consequently,  it  is  reasonable  to  admit 
the  possibility  of  variations  in  the  extent  of  these  fusions  and  the  places  where 
they  may  occur.  (For  further  details,  see  the  Memoirs  of  Goubaux  and  Sanson, 
in  Robin's  Journal  de  VAnatomie  de  la  Physiologie,  1867  and  1868.) 

Comparison  of  the  Vertebral  Column  of  Man  with  that  of  the  Domesticated 

Animals. 
The  vertebral  column  of  Man  is  composed  of  twenty-nine  bones :  twenty -four  vertebrae, 
the  sacrum,  and  four  pieces  constituting  the  coccyx.     The   twenty-four  vertebrae  are  thus 
distributed : 

Cervical  vertebrae 7 

Dorsal  „  12 

Lumbar        „  5 

In  all  these  vertebrae,  the  bodies  are  slightly  excavated  at  the  two  extremities,  while  in  the 
domesticated  animals,  the  superior  or  anterior  is  convex,  and  the  inferior  or  posterior  concave. 

1.  Cervical  vertebrae. — These  are  wide  and  short.  The  spinous  processes  are  moderately 
developed  and  bifid  at  their  summits ;  the  transverse  processes  are  also  divided  into  two 
branches — a  posterior  and  an  anterior. 

2.  Dorsal  vertebrx.—ln  these  vertebrae,  the  bodies  increase  in  thickness  from  the  first  to 
the  last.     In  the  first  as  well  as  in  the  last  dorsal  vertebrae,  the  spinous  process  is  almost 


46 


THE  BONES. 


immediately  directed  backwards  ;  in  the  middle  portion  of  this  region  these  processes  are  very 

obliquely  directed  downwards  and  backwards. 

3.  Lumbar  vertebras. — The  lumbar  vertebrae  are  the  strongest  bones  in  the  spine,  and  their 
bodies  are  nearly  as  thick  as  those  of  the  larger  domesti- 
cated animals.  This  enormous  development  of  the  lumbar 
vertebrae  in  Man  is  related  to  his  position  as  a  biped.  In 
the  fifth,  the  lower  face  of  the  body  is  cut  very  obliquely 
backwards  and  upwards,  and  the  transverse  processes  are 
more  voluminous  than  those  of  the  other  lumbar  vertebrae. 

4.  Sacrum. — The  sacrum  is  formed  by  the  union  oi 
five  pieces.  It  is  very  concave  from  above  to  below  and 
before  to  behind.  In  becoming  united  to  the  lumbar 
region,  it  forms  a  salient  angle  in  front,  to  which  has 
been  given  the  name  of  promontory  or  sacro-vertebral  angle. 
The  sacral  spine  is  continuous  or  interrupted,  according 
to  the  subject ;  it  is  always  bifid  inferiorly. 

5.  Coccygeal  vertebras. — These  are  little  bones  or  flat- 
tened tubercles,  four  in  number,  rarely  five,  and  usually 
consolidated.  Tbe  coccyx  is  conical  in  shape.  Its  base 
shows  two  processes  directed  upwards,  which  are  called 
the  cornua  of  the  coccyx.  Its  summit  is  often  deviated 
to  the  right  or  left. 


Article  IL— The  Head  (Fig.  26). 

The  head  is  a  large,  bony,  quadrangular 
pyramid,  elongated  from  above  to  below,  sus- 
pended by  its  base  to  the  anterior  extremity  of 
the  spine.  Its  direction  varies  with  the  atti- 
tudes of  the  animal,  but  we  will  suppose  it, 
for  convenience  of  description,  to  be  nearly  verti- 
cal. It  is  formed  of  a  great  number  of  particular 
bones,  which  are  only  distinct  from  one  another 
in  very  young  animals  ;  for  well  before  the  adult 
period  is  reached,  the  majority  of  the  bones  are 
united  and  cannot  be  separated. 

The  head  is  divided  into  two  parts  :  the 
cranium  and  the  face. 


horse's  head  (front  view) 

I,  Occipital  tuberosity;  2,  origin 
of  the  mastoid  crest ;  3,  parietal 
bone  ;  4,  saggital  suture  ;  5,  junc- 
tion of  the  parietal  and  temporal 
bones ;  6,  zygomatic  arch ;  7, 
frontal  bone  ;  8,  frontal  suture  ; 
9, temporal  fossa;  10,  supra-orbital 
foramen  ;  11,  12,  lachrymal  bone ; 
13,  malar  bone ;  14,  nasal  border  of 
frontal  bone  ;  15,  nasal  bone  ;  16, 
suture  of  nasal  bones;  17,  super- 
maxillary  bone  ;  18,  infra-orbital 
foramen  ;  19,  anterior,  or  pre- 
maxillary  bone;  20,  foramen  in- 
cisivum  ;  21,  incisor  teeth  (young 
mouth). 


Bones  of  the  Craniam. 

The  cranium,  or  upper  part  of  the  head,  is 
composed  of  seven  flat  bones,  five  of  which  are 
single  :  the  occipital,  parietal,  frontal,  sphenoid, 
and  ethmoid;  one  only,  the  temporal,  is  double. 
These  bones  circumscribe  a  central  cavity,  the 
cranial,  which  communicates  behind  with  the 
spinal  canal,  and  lodges  the  principal  portion  of 
the  nervous  centres — the  brain. 


1.  Occipital  Bone  (Fig.  26,  1). 

The  occipital  bone  occupies  the  superior  extremity  of  the  head,  which  it 
supports  from  the  anterior  extremity  of  the  spine.  This  bone  is  very  irregular 
m  its  form,  aud  is  bent  at  a  right  angle  in  front  and  behind.     It  has  an  external 


TEE  HEAD.  47 

and  an  internal  face,  and  a  circumference  which  brings  it  into  contact  with  the 
adjoining  cranial  bones  ;  the  latter  is  subdivided  into  two  anterior  lateral  borders, 
two  posterior  lateral  borders,  an  anterior  and  posterior  salient  angle,  and  two 
lateral  re-entering  angles. 

Faces. — The  external  face  is  divided  into  three  portions  by  the  double  flexure 
of  the  bone  :  one  looks  forward,  another  upward,  and  the  third  backward.  It 
exhibits  : — 1.  On  the  median  line,  and  from  before  to  behind  :  a,  an  antero- 
posterior ridge  which  constitutes  the  origin  of  the  parietal  ridges,  to  be  mentioned 
hereafter  ;  b,  a  transverse,  voluminous,  and  very  prominent  eminence,  marked 
posteriorly  by  deep  imprints,  with  a  medium  projection  named  the  cervical 
tuberosity  ;  this  is  the  external  occipital  tuberosity  which,  in  the  Horse,  corre- 
sponds at  the  same  time  to  the  superior  curved  lines  of  the  occipital  bone  of  Man. 
This  protuberance  forms  the  culminating  point  of  the  head,  and  divides  the 
anterior  and  superior  parts  of  the  external  face  of  the  bone  ;  c,  the  occipital 
foramen  {foramen  magnum),  a  large  orifice  that  passes  through  the  bone  at  the 
posterior  flexure,  and  establishes  a  communication  between  the  cranial  cavity  and 
spinal  canal ;  d,  the  external  surface  of  the  basilar  process — a  narrow  and  thick 
prolongation  formed  by  the  bone  as  it  passes  to  meet  the  sphenoid  :  this  surface 
is  convex  laterally.  2.  On  the  sides  :  a,  A  sharp  crest  which  prolongs,  laterally, 
the  superior  curved  lines,  and  descends  on  the  middle  of  the  lateral  anterior 
border,  to  be  continued  with  the  superior  root  of  the  zygomatic  process  and  the 
mastoid  crest  of  the  temporal  bone  ;  b,  Linear  imprints,  parallel  to  the  latter, 
and  prolonged  on  the  base  of  the  styloid  process  :  they  are  destined  for  the 
insertion  of  the  small  oblique  muscle  of  the  head,  and  represent  the  inferior 
curved  lines  of  the  occipital  bone  of  Man  ;  c,  Within  these  imprints  is  a  slightly 
roughened  cavity  for  the  insertion  of  the  posterior  recti  muscles ;  d,  The  two 
condyles — articular  eminences  with  a  double  convexity,  one  superior,  the  other 
inferior :  these  eminences  are  situated  on  each  side  of  the  occipital  foramen 
{foramen  magnum),  and  correspond  to  the  anterior  cavities  of  the  atlas  ;  e,  More 
outwards  are  the  two  styloid  {paroccipital)  processes,  or  jugular  eminences — long 
projections  flattened  on  each  side,  terminated  in  blunt  points,  directed  backwards, 
and  separated  from  the  condyles  by  a  deep  space,  the  stylo-condyloid  notch ;  f. 
Under  the  condyles  is  the  condyloid  fossa — a  smooth  depression,  pierced  at  the 
bottom  by  the  condyloid  foramen,  which  penetrates  the  cranium. 

The  internal  face  of  the  occipital  bone  is  concave,  and  shows  :  behind,  the 
foramen  magnum  ;  above,  an  uneven  surface,  which  forms  the  roof  of  the 
cerebral  cavity  ;  below,  the  superior  face  of  the  basilar  process,  slightly  hollowed 
into  a  groove  ;  on  the  sides,  the  internal  orifice  of  the  condyloid  foramen. 

Circumference. — The  anterior  lateral  borders  are  thick,  and  are  united  by 
suture  with  the  parietal  bone,  and  with  the  tuberous  portion  of  the  temporal 
bone  by  the  harmonia  suture.  The  posterior  lateral  borders  are  sharp,  and 
constitute  the  sides  of  the  basilar  process  ;  each  concurs  in  the  formation  of  the 
occipito-spheno-temporal  hiatus,  also  termed  the  foramen  lacerum  basis  cranii — a  vast 
irregular  opening,  extending  from  above  downwards,  penetrating  the  cranium,  and 
divided  by  a  ligament,  in  the  fresh  state,  into  two  portions,  one  inferior,  the 
anterior  foramen  lacerum,  the  other  superior,  the  posterior  foramen  lacerum.  The 
anterior  angle,  which  is  dentated,  is  dovetailed  into  the  parietal  bone.  Theposterior 
angle  is  very  thick,  and  forms  the  summit  of  the  basilar  process  ;  it  is  united  by 
suture  with  the  body  of  the  sphenoid.  The  lateral  re-entering  angles,  or  jugular 
notches,  correspond  to  the  point  where  the  bone  is  bent  posteriorly  ;  they  separate 


48  THE  BONES. 

the  anterior  lateral  from  the  corresponding  posterior  lateral  border,  and  are  occupied 
by  the  petrous  portion  of  the  temporal  bone. 

Structure. — The  occipital  bone  contains  much  spongy  substance. 

Development.— li  is  developed  from  four  centres  of  ossification  ;  one,  the 
anterior,  is  single,  and  forms  the  occipital  tuberosity  ;  another,  the  posterior, 
also  single,  forms  the  basilar  process  ;  the  other  two  are  pairs,  and  comprise  each 
a  condyle,  with  a  styloid  process  and  the  corresponding  condyloid  foramen. 

The  occipital  bone  in  the  Ass  is  distinguished  by  the  prominence  of  the 
external  occipital  tuberosity  (see  the  Head  in  General),  by  the  depth  of  the 
groove  (mastoid)  which  com^ses  over  the  outer  face  of  the  styloid  process,  and 
by  the  articular  surface  prolonged  to  the  origin  of  the  basilar  process,  which 
constricts  it  in  a  circular  manner. 

Differential  Characters  in  the  Occipital  Bone  op  other  Animals. 

A.  Ox. — The  occipital  bone  of  this  animal  does  not  show  any  anterior  elbow,  neither  does 
it  form  a  portion  of  the  iinierior  part  of  the  head.  The  external  occipital  tuberosity  is  obtuse, 
and  givts  rise  on  each  side  to  the  superior  curved  lines. 

The  styloid  processes  are  short  and  much  bent  inwards.  Tlie  basilar  process,  wide,  short, 
and  thick,  has  a  groove  in  the  middle  of  its  external  face ;  this  groove  is  sometimes  absent  in 
the  Sheep  and  Goat. 

The  condyloid  foramina  are  double,  sometimes  triple ;  the  superior  foramen  does  not  pass 
directly  into  the  cranium,  but  goes  to  a  vast  conduit  that  opens  behind  on  the  lateral  margin 
of  the  occipital  foramen,  and  wliich  terminates  in  front  by  two  orifices,  one  entering  the  parieto- 
temporal canal,  the  other  opening  on  the  external  surface  of  the  bone.  The  foramen  lacerum 
is  divided  into  an  anterior  aud  posterior  foramen,  by  the  mastoid  portion  of  the  temporal 
bone. 

B.  Sheep  and  Goat. — The  inner  tuberosity  is  only  marked  by  a  slight  prominence  of  the 
internal  plate  of  the  bone.  In  the  occipital  bone  of  these  animals  are  found  the  peculiarities 
noted  in  that  of  the  Ox  ;  the  groove  on  the  basilar  process  is  sometimes  absent,  and  in  the 
Sheep  the  superior  curved  lines  are  very  salient  and  occupy  the  summit  of  the  head.  This 
feature  is  still  more  marked  in  the  Goat,  and  also  more  in  the  Cervine  species,  in  wliich  this 
bone  somewhat  resembles  that  of  the  Horse. 

C.  Camel. — The  bone  shows  a  double  angle  as  in  Solipeds.  In  its  anterior  and  superior 
portions  it  resembles  that  of  the  Horse,  and  in  its  posterior  portion  that  of  the  Ox.  The  crest, 
which  constitutes  the  origin  of  the  parietal  crests,  as  well  as  the  superior  curved  lines,  are 
thin,  sharp,  and  very  high.  The  styloid  processes  are  short,  wide,  thick,  and  articulated  by 
harmonic  suture  with  the  tuberosity  of  the  temporal  bone.  The  superior  curved  lines  are 
scarcely  marked  in  young  animals. 

D.  Pig. — The  occipital  bone  in  this  animal  is  not  bent  anteriorly;  but  the  transverse 
protuberance  representing  the  curved  lines  forms,  nevertheless,  as  in  the  Horse,  the  summit  of 
the  Head.  This  eminence,  which  is  excavated  on  both  sides  on  the  posterior  face,  unites  in 
front  with  the  parietal  bone,  which  abuts  on  the  occipital  at  an  acute  angle.  There  is  no 
externa]  occipital  protuberance,  properly  speaking,  and  the  styloid  processes  are  very  long  and 
directed  downwards. 

E.  Camivora.— The  external  occipital  tuberosity  is  very  strong  and  high.  The  external 
occipital  crest  is  absent  or  little  marked ;  the  styloid  processes  are  short.  The  foramen  lacerum 
is  divided  into  two  portions  by  the  mastoid  process,  and  the  basilar  process  is  wide,  long,  and 
thick,  and  hollowed  on  the  side  by  a  channel  that  joins  a  similar  one  in  the  temporal  bone  to 
form  a  large  venous  canal.  Tliis  last  communicates,  behind,  with  the  posterior  foramen 
lacerum,  and  opens,  in  front,  in  the  cranium,  where  it  is  continuous  with  the  cavernous  groove 
of  the  sphenoid.  The  anterior  angle  forms  a  very  marked  prominence,  which  is  deeply  fixed 
into  the  parietal  bone,  and  partly  constitutes  the  internal  occipitnl  process  of  that  bone.  The 
latter  does  not  show  the  lateral  excavations  at  its  base;  they  are  found  lower,  towards  the 
summit  of  the  petrous  bone,  on  the  sides  of  the  occipital.  The  parieto-temporal  canals  are, 
nevertheless,  continued  to  the  base  of  the  process,  which  they  traverse  to  open  into  its  interior. 
In  the  most  intelligent  breeds,  the  occipital  foramen  is  deeply  notched  above  (Faure). 


THE  HEAD. 


2.  The  Parietal  Bone  (Fig.  26). 

The  parietal  is  a  wide  and  thin  bone,  very  much  arched  to  form  the  roof  of 
the  cranial  cavity.  It  is  bounded  above  by  the  occipital  bone,  below  by  the 
frontal,  and  laterally  by  the  two  temporal  bones.  It  offers  for  study  an  external 
and  internal  face,  and  a  circumference  divided  into  four  regions  or  borders. 

Faces. — The  external  face  is  convex.  It  exhibits  two  curved  ridges  with 
concavity  directed  outwards  ;  these  two  crests,  which  are  termed  the  parietal 
ridges,  approach  each  other  and  unite  superiorly,  to  be  continued  with  the  antero- 
posterior ridge  of  the  occipital  bone  ;  below  they  diverge  and  proceed,  one  on 
each  side,  to  join  ike  supra-orbital  process.  They  divide  the  surface  of  the  bone 
into  three  portions  :  two  lateral,  which  are  rough  and  traversed  by  vascular 
channels,  forming  part  of  the  temporal  f ossa3 ;  the 
third,  or  middle,  is  plane,  smooth,  and  of  a  triangu- 
lar form,  and  covered  by  the  skin.  The  interjial 
face  is  concave,  covered  by  digital  impressions, 
and  grooved  by  small  vascular  canals  ;  it  offers, 
on  the  middle  line,  and  altogether  above,  the 
parietcd  protuberance.  This  trifacial  and  very 
salient  projection  presents  at  its  base,  on  each  side, 
an  excavation  elongated  transversely,  into  which 
opens  the  parieto-temporal  canal,  and  which 
lodges  a  venous  sinus.  It  is  continued,  in  front, 
by  a  median  crest,  which  is  often  replaced  by  a 
slight  groove — ^the  saggital  furrow,  bordered  by 
linear  imprints.  Two  other  ridges,  resulting  from 
the  abutment  of  the  lateral  border  of  the  bone 
against  the  anterior  face  of  the  petrous  bone,  rise 
from  the  sides  of  this  eminence  and  descend  to 
the  sphenoid  bone  ;  they  separate  the  cerebral 
from  the  cerebellar  cavity. 

Borders. — The  superior  border  is  notched, 
thick,  and  slightly  dentated  ;  it  articulates  with 
the  occipital  bone.  The  inferior  border,  slightly 
concave,  and  deeply  dentated,  offers  an  external 
bevel  in  its  middle  portion,  and  an  internal  bevel 
on  its  sides  ;  it  corresponds  with  the  frontal  bone. 
The  lettered  borders  are  very  thin,  and  are  cut,  at 
the  expense  of  the  external  plate,  into  a  wide,  sloping  edge,  which  shows  a  groove 
destined  to  form  the  parieto-temporal  canal.  A  very  prominent  angle  separates 
each  into  two  portions — an  inferior,  that  articulates  by  suture  with  the  squamous 
portion  of  the  temporal  bone  ;  and  a  superior,  curved  inwards  towards  the  centre 
of  the  cranial  cavity.  The  latter  portion  of  the  lateral  border  is  in  contact  with 
the  anterior  face  of  the  petrous  portion  of  the  temporal  bone,  with  which  it 
concurs  to  form  the  lateral  crest  that  descends  to  the  parietal  protuberance. 

Structure. — This  bone  contains  much  compact  tissue,  the  spongy  substance 
existing  only  in  its  middle. 

Development. — It  is  developed  from  two  large  lateral  centres  of  ossification,  to 
which  is  added  a  single  centre  to  form  the  parietal  protuberance.  In  early  life 
the  parietal  ridges  are  absent. 


head  of  the  cat  (posterior 
aspect). 
1,  Occipital  bone;  2,  zygomatic 
process  of  the  temporal  bone; 
3,  tympanic  bulb  ;  4,  condyle  of 
the  temporal  bone ;  5,  malar 
bone  ;  6,  orbital  process  of  the 
malar  ;  7,  ditto  of  frontal  bone  ; 
8,  8,  palatine  bones  ;  9,  9,  maxil- 
lary bone;  10,  premaxillary  bone; 
11,  pterygoid  bone;  12,  sphenoid 
bone ;   13,  vomer. 


50 


THE  BONES. 


Differential  Characters  of  the  Parietal  Bone  in  other  Animals. 

A.  Ox. — The  parietal  bone  in  the  Ox  does  not  occupy  the  anterior  aspect  of  the  head,  but 
concurs  with  the  occipital  to  form  the  base  of  the  neck.  It  represents  a  very  narrow  osseous 
plate,  elongated  transversely,  and  curved  at  its  two  extremities,  which  descends  into  the 
temporal  fossae  to  rest  upon  the  sphenoid  bone.  There  are  no  parietal  ridges.  The  internal 
protuberance  is  only  marked  by  a  slight  elevation  of  the  internal  plate ;  for  the  most  part  it 
belongs  to  the  occipital  bone.  The  parietal  bone  of  the  Ox  is  developed  from  three  centres 
of  ossification,  and  the  middle  nucleus  is  even  primarily  divided  into  lateral  halves ;  but  these 
centres  «re  consolidated  with  each  other  at  an  early  period,  as  well  as  with  the  anterior 
portion  of  the  occipital.  It  does  not  aid  in  the  formation  of  the 
parieto-teniporal  canal,  and  is  excavated  internally  by  cavities 
which  communicate  with  the  frontal  sinuses. 

B.  Sheep,  Goat.— The  parietal  bone  of  the  Sheep  and  Goat 
is  relatively  much  larger  than  that  of  the  Ox.  It  participates  in 
the  formation  of  the  parieto-temporal  canal,  and  has  no  sinuses. 

C.  Camel.— This  bone  occupies  the  anterior  face  of  the 
cranium ;  but  it  is  long,  narrow,  and  deeply  lodged  between  the 
squamous  portion  of  the  temporal  bone  and  the  frontal  bone,  to 
rest  on  the  sphenoid.  The  parietal  crests,  thin  and  elevated,  lie 
against  each  other  for  nearly  their  entire  lengtli,  and  are  not  pro- 
longed to  the  frontal  bone  (Fig.  45).  These  crests  do  not  exist  at 
an  early  age. 

D.  Pig. — The  parietal  bone  is  very  thick ;  it  has  two  very 
marked  crests,  which  do  not  meet  at  their  upper  part  (Fig.  28). 

E.  Dog,  Cat. — In  the  Dog,  the  parietal  bone  is  distinguished 
by  the  great  development  of  the  temporal  crests  (Fig.  2li). 

In  the  Cat  there  are  scarcely  any  parietal  crests,  and  the  in- 
ternal protuberance  is  replaced  by  two  great  transverse  bony  plates, 
which  separate  the  cavity  of  the  cerebrum  from  that  of  the 
cerebellum. 

F.  Rabbit.— Almost  quadrilateral,  the  parietal  bone  of  the 
Rabbit  has  its  temporal  crests  carried  to  near  its  lateral  borders. 

3.  Frontal  Bone  (Fig.  26). 

The  frontal  is  a  flat  quadrilateral  bone,  the  sides  of 
which  are  bent  in  the  middle  at  an  acute  angle,  and  are 
carried  back,  and  a  little  inwards,  to  meet  the  wings  of 
the  sphenoid  bone.  It  assists  in  forming  the  cranial  roof 
and  part  of  the  face.  It  is  bordered  :  above,  by  the 
parietal  bone  ;  below,  by  the  nasal  and  lachrymal  bones  ; 
and  on  each  side,  by  the  temporal  bones.  It  offers  for 
study  an  external  and  an  internal  face,  and  four  borders. 

Faces. — The  external  face  is  divided,  by  the  double 
flexure  of  the  bone,  into  three  regions  :  a  middle  and 
two  lateral.  The  first,  nearly  plane,  is  lozenge-shaped, 
is  covered  by  the  skin,  and  constitutes  the  base  of  the 
forehead.  It  gives  rise  on  each  side,  at  the  point  where 
it  is  inflected,  to  a  long  process,  flattened  above  and 
below,  which  curves  backward,  forming  the  orbital  arch. 
The  superior  or  external  face  of  this  process  is  convex  and  slightly  roughened  ; 
the  internal  face  is  smooth  and  concave,  and  forms  part  of  the  orbital  fossa.  Its 
posterior  border,  thick  and  concave,  is  continued,  inwardly,  with  the  correspond- 
ing parietal  ridge,  and  outwardly  with  the  superior  border  of  the  zygomatic 
process.  It  limits,  in  front,  the  temporal  fossa.  The  anterior  border,  also 
concave,  but  thin,  concurs  in  the  formation  of  the  orbital  margin  ;  the  summit, 


head  of  the  pig 
(anterior  face). 
1,  Summit  of  occipital 
tuberosity.  2,  parietal 
bone.  3,  frontal  bone  : 
A,  Supra-orbital  fora- 
men ;  a',  channel  de- 
scending from  it.  4, 
zgomatic  process.  5, 
malar  bone.  6,  lachry- 
mal bone :  b,  Lachrymal 
canals.  7,  supermax- 
illary  bone  :  C,  Inferior 
orifice  of  the  super- 
maxillo-dental  canal. 
8,  nasal  bone.  9,  pre- 
maxillary  bone. 


THE  HEAD. 


thickened  and  denticulated,  rests  upon,  and  is  united  to,  the  zygomatic  process 
of  the  temporal  bone  ;  the  base  is  wide,  and  is  traversed  by  an  opening  termed 
the  supra-orUtal,  or  superciUarij  foramen.  The  two  lateral  regions  of  the  external 
face  of  the  frontal  bone  are  slightly  excavated,  and  assist,  for  the  greater  portion 
of  their  extent,  to  form  the  orbits.  They  often  show,  near  the  base  of  the 
orbital  arch,  a  small  depression  corresponding  to  the  flexure  described  by  the 
great  oblique  muscle  of  the  eye  in  passing  through  its  pulley. 

The  interned  face  of  the  frontal  bone  is  concave,  and  divided  into  two  unequal 
parts  by  a  transverse  ridge,  corresponding  to  the 
anterior  border  of  the  cribriform  plate  of  the  ethmoid 
bone.  The  superior,  the  most  extensive,  is  covered 
with  digital  impressions,  and  belongs  to  the  cranial 
cavity.  It  exhibits  :  1.  On  the  median  line,  a  slight 
furrow,  or  a  crest  which  is  continuous,  above,  with  the 
median  ridge  of  the  parietal  bone,  and  below,  with 
the  crista-gaJU  process.  2.  On  the  sides,  and  in  the 
re-entering  angle  formed  by  the  flexure  of  the  bone, 
there  is  a  narrow  slit,  or  mortise,  which  receives  the 
wing  of  the  sphenoid  bone.  The  inferior  part  is  united, 
on  the  median  line,  to  the  perpendicular  plate  of  the 
ethmoid.  It  assists  in  forming  the  bottom  of  the 
nasal  cavities,  and  presents  laterally  two  large  openings 
which  lead  to  the  frontal  sinuses — vast  anfractuous 
spaces  excavated  between  the  two  plates  of  the  bone. 

Borders. — The  superior  border  is  denticulated  and 
cut  obliquely  in  its  middle  portion,  at  the  expense  of 
the  internal  plate,  and  on  the  lateral  parts  at  the 
expense  of  the  external  table  ;  it  is  in  contact  with 
the  parietal  and  squamous  portion  of  the  temporal 
bone.  The  inferior,  prolonged  to  a  point  in  the  middle, 
is  in  apposition  with  the  nasal  bones  through  the 
medium  of  a  wide  external  bevel ;  laterally,  it  is  very 
thin,  faintly  serrated,  and  articulates  with  the  lachrymal 
bone.  The  lateral  borders,  thin  and  irregular,  present 
two  notches  :  one,  the  superior  {incisura  spJmioidaUs), 
is  wide  and  deep,  and  occupied  by  the  wing  of  the  sphe- 
noid bone  ;  the  other,  inferior,  is  very  narrow,  and, 
uniting  with  a  similar  notch  in  the  sphenoid  bone,  forms 
the  orbital  foramen,  which  opens  into  the  cranium, 
very  near,  but  external  to,  the  ethmoid  fossa.  Each  of  these  borders,  also,  is 
adapted,  for  a  limited  extent,  to  the  corresponding  palatine  bone. 

Structure. — The  two  compact  plates  of  the  frontal  bone  are  separated  by 
spongy  texture  towards  the  middle  and  in  the  upper  part ;  they  separate  below 
to  form  the  frontal  sinuses.  Laterally,  they  are  very  thin  and  consolidated  with 
each  other. 

Development. — The  frontal  bone  is  developed  from  two  lateral  centres  of 
ossification,  which  only  coalesce  at  a  late  period.  In  youth  the  cranial  portion 
of  the  bone  forms,  in  front  of  the  head,  a  large  rounded  protuberance  standing 
beyond  the  facial  portion.  This  prominence  disappears  when  the  frontal  sinuses 
begin  to  be  developed.     These  cavities  do  not  exist  at  an  early  period  of  foetal 


head  of  dog  (anterior 
face). 

1,  Occipital  tuberosity;  2, 
median  spur  of  the  occi- 
pital bone ;  3,  parietal 
bone  ;  4,  origin  of  the  pa- 
rietal crests;  5,  zygomatic 
process  ot  the  temporal 
bone  ;  6,  frontal  bone  ;  6', 
orbital  process ;  7,  malar 
bone  ;  8,  lachrymal  bone  ; 
9,  nasal  bone  ;  10,  super- 
maxilla  ;  11,  inferior  ori- 
fice of  the  supermaxillo- 
dental  canal;  12,  pre- 
maxillary  bone. 


52  THE  BONES. 

life  ;  but  commence  to  form  about  the  fourth  month  of  conception,  by  a  process 
of  resorption,  which  removes  the  spongy  substance  interposed  between  the  two 
compact  tables  of  bone,  and  may  even  cause  the  destruction  of  the  internal  table. 
The  sinuses  enlarge  with  age,  and  remain  during  life  separated  from  one  another 
by  a  vertical  septum. 

Differential  Characters  in  the  Frontal  Bone  of  other  Animals. 

A.  Ox,  Sheep,  Goat. — In  Eumiaants,  the  frontal  bone  does  not  come  in  contact  with 
the  temporal  or  palatine  bones  (Figs.  30,  31,  32). 

In  the  Ox,  this  bone  is  extremely  developed,  occupying  alone  nearly  one-half  of  the  anterior 
surface  of  the  head.     It  is  particularly  distinguished  by:  1.  Its  great  thickness.     2,  The 

Fig.  30. 


ox's  head  (anterior  face). 

1,  Mastoid  process  ;  2,  superciliary,  or  supra-orbital  foramen  ;  3,  malar  bone ;  4,  lachrymal 

bone  ;  5,  maxillary  spine  ;  6,  inferior  orifice  of  the  supermaxillo-dental  canal. 


osseous  conical  cores  which  support  the  horns.  These  eminences,  more  or  less  long  and  curved, 
very  rugged,  perforated  by  foramina,  and  grooved  by  small  vascular  channels,  are  detached 
outwards  from  each  side  of  the  bone,  near  the  summit  of  the  head.  The  proce.-^ses  which  form 
the  orbital  arches  rest  by  their  summits  on  the  zygomatic  bone.  The  supra-orbital  foramen  is 
transforraeil  into  a  veritable  and  frequently  multiple  canal ;  its  anterior  orifice  opens  into  a 
vasculo-nervous  groove,  which  ascends  towards  the  base  of  the  horns,  and  descends  to  near  the 
lower  border  of  the  bone.  Between  this  groove  and  the  base  of  the  orbital  arch  is  the  frontal 
boss.  Thp  orbital  foramen  entirely  belongs  to  this  bone.  The  inferior  border  is  deeply  notched 
in  its  middle  to  receive  the  nasal  bones;  the  frontal  sinuses  are  prolonged  into  the  horn-cores, 
the  parietal  bone,  and  even  into  the  occipital  bone.  , 

The  frontal  bones  of  the  Angus  breed  of  cattle  (^polled  cattle)  have  no  horn-cores.  The 
ablation  in  the  calf  of  the  periosteum,  followed  by  cauterization,  at  the  point  where  appear 
the  osseous  prolongations  which  serve  as  bases  for  the  horns,  prevents  the  development  of 
these  appendages.  Cornevin  mentions  that  a  farmer  of  Haute  Marne  has  in  this  way  muti- 
lated the  cattle  bred  on  his  farm  for  twenty-three  years,  and  yet  the  mutilation  has  not  become 
hereditary.    Fig.  31,  representing  the  head  of  an  Ox  so  mutilated,  shows  that  the  removal  of  the 


THE  BEAD. 


53 


periosteum  in  such  animals  has  the  effect  of  producing  a  considerable  elongation  and  narrowing 
of  the  upper  part  of  the  frontal  bone. 

In  the  Sheep  and  Goat,  tlie  frontal  bone  is  relatively  less  extensive  and  strong  than  in  the 
Ox;  it  does  not  ascend  to  the  summit  of  the  head,  and  the  frontal  sinuses  are  not  prolonged 
beyond  its  superior  border  (Fig.  32). 

B.  Camel. — The  frontal  bone  of  this  animal  much  resembles  that  of  Solipeds.  The 
middle  portion  of  its  external  face  is  triangular  in  shape,  the  base  being  wide,  and  the  apex 
fixed  in  the  deep  notch  formed  on  the  inferior  border  of  the  parietal  bone;  it  is  slightly 
hollowed  in  the  middle  line,  and  convex  on  the  lateral  parts.     The  orbital  arch  rests  on  the 


Fig.  32. 


HEAD   OF   A    HORNLESS   OX. 


ram's  head  (anterior  face). 
1,  Occipital  bone  ;  2,  parietal  bone  ;  3,  core  of  right 
frontal  bone  ;  4,  the  left  core  covered  by  its  horn ; 
5,  supra-orbital  foramen  ;  5',  channel  descending 
from  it ;  6,  lachrymal  bone  ;  7,  malar  bone ;  8,  nasal 
bone  ;  9,  supermaxillary  bone  ;  10,  premaxillary 
bone;  10',  its  internal  process;  11,  incisive  open- 
ing. 

zygomatic  bone,  as  in  the  Ox  (Fig.  37).  The  supra-orbital  foramina  are  transformed  into 
inflected  canals,  which  open  on  the  anterior  face  of  the  bone,  near  its  middle. 

On  the  circumference  of  the  bone  are  several  notches,  some  of  which  concur  with  the 
other  bones,  to  form  foramina  (orbital,  nasal) ;  two  are  seen  to  the  right  and  left  of  the  line  of 
union  of  the  bone  with  the  supra-nasal,  and  two  others  are  in  the  orbital  cavity.  These  open- 
ings are  partially  closed  by  the  Wormian  bones ;  they  open  into  the  upper  compartments  of  the 
turbinated  bones. 

In  the  young  Camel,  the  middle  portion  is  deeply  excavated ;  this  excavation  diminishes 
as  the  animal  advances  in  age,  and  as  the  frontal  sinuses  enlarge. 

C.  Pig.— The  frontal  bone  of  the  Pig  is  very  thick  and  short,  and  does  not  join  the 
temporal  or  zygomatic  bones  ;  the  orbital  arch  is  completed  by  a  ligament.  The  supra-orbital 
foramen,  disposed  as  in  the  Ox,  abuts  in  a  channel  that  descends  on  the  nasal  bones.     The 


*  In  the  Museum  of  the  Lyons  Veterinary  School. 


54 


THE  BONES. 


orbital  foramen  is  formed  by  the  frontal  bone  only.  There  is  no  mortise  for  the  union  of  the 
frontal  with  the  sphenoid  bone ;  and  the  frontal  sinuses  are  prolonged  into  the  parietal.  The 
frontal  bone  articulates  with  the  superior  maxillarie.s  (Fig.  28). 

D.  Carnivora. — In  the  Carnivora,  the  external  face  of  the  frontal  bone  presents  in  its 
middle  a  more  or  less  deep  depression.     The  ori)ital  arch  is  incomplete,  and  there  is  no  supra- 
orbital foramen  or  mortise  on  the  inner  face. 


superior  maxilLiry  bones 


anterior  bones  of  the  head  op  a  fcetus 
(horse)  at  birth,  disarticulated,  and 
viewed  from  behind. 


It  unites  with  tht 
(Fi-.  29). 

E.  Rabbit. — In  this  animal  the  frontal 
bone  is  long  and  narrow,  and  the  orbital 
process  is  thin,  elevated,  and  directed  upwards 
and  backwards,  but  it  does  not  reach  the 
zygomatic  bone,  and  is  deeply  notched  at  its 


4.  Ethmoid  Bone  (Fig.  33). 

The  ethmoid  bone,  deeply  situated 
m  the  limit  between  the  cranium  and 
the  face,  is  enclosed  between  the  frontal, 
the  sphenoid,  the  vomer,  the  palatine, 
and  the  supermaxillary  bones.  It  is 
composed  of  three  portions — a  jjer- 
pendicular  plate,  and  two  lateral  masses. 

The  Perpendicular  Lamina  of 
THE  Ethmoid  Bone. — Situated  in  the 
mesian  plane,  and  flattened  on  both 
sides,  this  bone  presents  tu'o  faces,  a 
left  and  right,  and  four  borders. 

Faces. — The  faces,  covered  by  the 


.,  Occipital  bone  :  1,  condyle ;  2,  condyloid 
foramen ;  3,  styloid  process ;  4,  summit  of 
basilar  process.  B,  Parietal  bone  :  8,  j)arie- 
tal  protuberance;  9,  channel  which  concurs 
to  form  the  parieto-temporal  canal.  C,  Fron- 
tal bone:  10,  transverse  crests  separating 
the  cranial  from  the  facial  portion  of  the 
bone;  11,  frontal  sinuses;  12,  notch  on  the 
lateral  border  occupied  by  the  wing  of  the 
sphenoid  bone  ;  13,  notch  for  the  formation 
of  the  orbital  foramen  ;  14,  summit  of  the 
orbital    process  ;    15,   supra-orbital  foramen. 

D,  Perpendicular  lamina  of  the  ethmoid  bone. 

E,  E,  Lateral  masses  of  the  ethmoid  bone  : 
16,  the  great  ethmoid  cell.  F,  Squamous 
portion  of  the  temporal  bone :  17,  Supra- 
condyloid  process  ;  18,  channel  for  the  forma- 
tion of  the  parieto-temporal  canal.  G,  Pet- 
rous portion  of  the  temporal  bone  :  5, 
mastoid  process  ;  6,  internal  auditory  hiatus  ; 
7,  opening  for  the  Eustachian  tube  into  the 
tympanum,  h,  Lachrymal  bone.  I,  Nasal 
bone.     J,  Superior  turbinated  bone. 


pituitary  membrane,  present,  posteriorly,  small  sinuous  crests  ;  elsewhere  they  are 
smooth.  A  very  narrow  interval,  constituting  the  bottom  of  the  nasal  cavities, 
separates  them  from  the  lateral  masses. 

Borders. — The  superior  border  looks  towards  the  centre  of  the  cranial  cavity, 
and  constitutes  what  is  called  the  ethmoidal  ridge,  or  crista-galli  ^wocess.     It  is 


THE  HEAD.  55 

free,  concave,  and  sharp,  prolonged  in  front  and  above  by  the  median  crest  of 
the  frontal  bone,  and  confounded  behind  with  the  middle  portion  of  the  inferior 
sphenoid.  The  inferior  border  is  continuous  with  the  cartilaginous  plate  which 
separates  the  nasal  cavities.  When  this  plate  becomes  ossified,  which  is  not 
unfrequent,  it  is  impossible  to  discover  the  point  where  it  begins  or  the  ethmoid 
bone  terminates.  The  middle  Septum  of  the  nose  has  been  considered,  and 
justly,  as  a  prolongation  of  the  perpendicular  plate  (or  lamina)  of  this  bone. 
The  anterior  border  is  consolidated  with  the  vertical  septum  which  separates  the 
frontal  sinuses.  The  posterior  border  is  joined  above  to  the  median  plate  which 
divides  the  sphenoidal  sinuses  into  two  compartments.  Below,  it  is  fixed  in  the 
groove  of  the  vomer,  and  soon  becomes  confounded  with  that  bone,  which  is 
itself  consolidated  with  the  inferior  sphenoid. 

Lateral  Masses  of  the  Ethmoid  Bone. — These  are  two  large  pyriform 
tuberosities  placed  on  each  side  of  the  perpendicular  lamina,  and  offering  for 
study  a  middle  portion,  a  base,  and  a  summit.  Each  of  these  is  formed  by  an 
assemblage  of  numerous,  extremely  thin,  osseous  plates,  curved  into  small  and 
very  fragile  convolutions.  These,  elongated  from  above  to  below,  become 
longer  as  they  are  more  anterior  ;  they  are  attached  by  their  superior  extremities 
to  the  transverse  plate  which  separates  the  cranium  from  the  nasal  cavities,  and 
by  one  of  their  borders  to  a  thin  leaf  of  bone  which  envelops  the  lateral  masses 
outwardly.     They  have  received  the  name  of  the  ethmoidal  volutes  (or  cells). 

Middle  portion. — This  should  be  studied  externally  and  internally 

The  external  surface  of  each  ethmoidal  mass  is  divided  into  two  sections  : 
an  internal,  making  part  of  the  nasal  cavities  ;  the  other,  external,  concurs  in 
forming  the  walls  of  the  frontal  and  maxillary  sinuses.  The  first,  the  least 
extensive,  is  almost  plane  ;  parallel  to  the  perpendicular  lamina,  it  is  isolated 
from  it  by  the  narrow  space  which  forms  the  bottom  of  the  nasal  cavities  ;  it 
presents  several  openings  which  separate  the  most  superficial  cells,  and  join  the 
internal  canals  to  be  hereafter  noticed.  The  second,  very  extensive  and  convex, 
looks  outwards  in  front  and  behind,  and  is  covered  by  an  osseous  plate  traced 
with  shallow  furrows,  which  correspond  internally  with  the  small  crests  to  which 
the  cells  are  attached.  This  lamella  is  prolonged,  inferiorly,  a  little  beneath  the 
inferior  extremity  of  these  latter,  and  turns  outwards  to  articulate  with  the 
palate  and  superior  maxillary  bones  ;  superiorly,  it  coalesces  with  the  sphenoid 
and  the  orbital  portion  of  the  frontal  bone. 

Internally,  the  lateral  masses  are  hollowed  from  above  to  below  by  extremely 
diverging  canals,  which  open  inferiorly  into  the  nasal  cavities,  and  separate  the 
cells  from  one  another.  The  latter  are  so  incurvated  that  the  internal  cells 
communicate  with  each  other.  There  are  some,  however,  which  are  completely 
closed  ;  the  anterior,  or  great  cell,  is  frequently  so.^ 

Base. — The  base  of  each  lateral  mass  looks  upwards,  and  is  formed  by  the 
transverse  septum  between  the  cranium  and  the  nasal  cavities.  This  septum  is 
perforated  by  openings  which  give  passage  to  the  ethmoidal  nerves  ;  it  is  named 
the  cribriform  plate  of  the  ethmoid  bone.  It  is  concave  on  the  superior  surface, 
which  constitutes  the  ethmoidal  fossa,  and  convex  on  the  opposite  face,  where 
attachment  is  given  to  the  superior  extremities  of  the  cells.  It  is  consolidated 
internally  with  the  perpendicular  plate  ;  the  other  points  of  its  circumference 
are  attached  to  the  sphenoid  bone,  and  to  the  transverse  ridge  on  the  internal 
face  of  the  frontal  bone. 

'  It  is  not  rare  to  find  it  opening  into  the  superior  maxillary  sinus. 


96  THE   BONES. 

Summit. — The  summit  of  each  lateral  mass  is  formed  by  the  inferioi 
extremity  of  the  ethmoidal  cells,  which  is  directed  downwards,  towards  the  nasal 
cavities.  One,  more  volmninous  than  the  others,  is  carried  much  lower,  and 
terminates  by  a  rounded  protuberance.  It  corresponds  to  the  middle  cornu 
{concha  media)  of  Man. 

Structure  of  the  ethmoid  hone. — Very  little*  spongy  tissue  enters  into  the 
composition  of  this  bone,  and  this  is  only  found  near  the  anterior  border  of 
the  perpendicular  plate. 

Development. — The  ethmoid  bone  is  late  in  attaining  its  development,  and 
the  adjoining  bones  are  nearly  completely  ossified  when  it  is  yet  entirely 
cartilaginous.  The  bony  transformation  commences  in  it  at  the  inferior  ex- 
tremity of  the  cells,  and  advances  progressively  from  below  upwards.  The  per- 
pendicular plate  is  only  ossified  in  part  when  the  cells  have  passed  through  the 
first  half  of  the  process  ;  at  the  same  time  it  coalesces  with  the  inferior 
sphenoid.  The  cribriform  plate  is  the  last  to  become  ossified,  this  transforma- 
tion having  scarcely  been  achieved  when  the  animal  is  six  or  eight  months  old. 

Differential  Characters  in  the  Ethmoid  Bone  of  other  Animals. 

A.  Ox,  Sheep,  Goat. — In  Ruminants,  the  great  ethmoidal  cell  is  enormously  developed, 
and  looks  like  a  third  turbinated  bone  prolonged  beyond  tlie  usual  two ;  it  has  been  named 
the  olfactory  antrum.  The  bone  is  closely  imprisoned  between  the  adjacent  bones,  in  con- 
sequence of  the  slight  development  of  the  sinuses  around  it.  This  character  otherwise  belongs 
to  all  the  domesticated  animals,  except  Solipeds  (Fig.  36). 

B.  Camel.— The  crista-galli  process  is  very  thick,  and  the  ethmoidal  fossae  are  narrow 
and  deep. 

C.  Pig.— The  superior  turbinated  bone  is  very  long,  and  the  papyraceous  plate  appears  in 
the  orbital  cavity. 

D.  Dog,  Cat. — The  ethmoidal  fossa  is  very  deep,  and  the  cells  very  developed  and 
diverticulated.  The  perpendicular  lamina  is  at  a  late  period  consolidated  with  the  sphenoid 
bone. 

5.  Sphenoid  Bone  (Fig.  34). 

The  sphenoid  bone  is  situated  behind  the  cranium,  between  the  occipital, 
ethmoidal,  palatine,  vomer,  pterygoid,  frontal,  and  temporal  bones.  It  is  formed 
by  the  union  of  two  pieces,  which  have  been  sometimes  described  as  distinct 
bones — the  anterior  or  inferior  sphenoid,  and  the  posterior  or  superior  sphenoid. 
It  is  now  supposed,  in  the  description,  that  this  union  has  been  completed. 

It  is  a  bone  flattened  before  and  behind,  curved  from  one  side  to  the 
other,  thick  in  its  middle  part,  named  the  bodi/,  and  thin  on  the  sides,  which,  in 
their  inferior  half,  are  prolonged  in  the  form  of  aJce,  or  U'ings.  It  has  two 
surfaces  a,nd  four  borders. 

Surfaces. — The  exfermd  surface  is  convex,  and  presents  :  1.  On  the  median 
line,  the  external  surface  of  the  body,  rounded  from  one  side  to  the  other,  is 
continued  with  that  of  the  basilar  process,  and  has  marked  muscular  imprints 
superiorly.  2.  On  the  sides  and  from  within  outwards  :  (a)  the  Vidian  (or 
pterygoid)  fissure,  directed  from  above  downwards,  and  continued  by  the  Vidian 
canal,  a  very  smaU  foramen  which  opens  into  the  orbital  hiatus  ;  (b)  the  sub- 
sphenoidal,  or  pterygoid  process,  a  long  eminence,  flattened  on  both  sides,  inclining 
downwards,  articulating  with  the  palatine  and  pterygoid  bones,  and  traversed  at 
its  base  by  the  Vidian  canal ;  (f)  a  little  behind  and  above  this  eminence,  the 
superior  orifice  of  the  sub-sphenoidal  (or  pterygoid)  foramen — a  large  canal  which 
bifurcates  inferiorly  ;  (d)  more  in  front,  the  orbital  hiatus,  a  kind  of  vestibule  into 


THE  HEAD. 


F 


Fig.  34. 


which  open,  in  common,  the  principal  branch  of  the  subsphenoidal  canal,  the  three 
supra-sphenoidal  canals,  the  Vidian  and  optic  canals,  and  the  orbital  opening  : 
this  hiatus  is  surmounted  by  a  thin  and  sharp  bony  plate,  above  which  opens 
the  smallest  branch  of  the  subsphenoidal  foramen  ;  (e)  altogether  without  the 
hiatus  is  remarked  a  smooth  surface  belonging  to  the  wing  of  the  sphenoid,  and 
which  concurs  to  form  the  orbital  cavity. 

The  internal  face  is  concave  from  side  to  side.  It  shows  :  1.  On  the  median 
line,  and  from  before  to  behind,  a  small 
projection  united  to  the  crista-galli ;  the 
optic  fossa,  elongated  transversely  in  the 
form  of  a  shuttle,  and  presenting  at  the 
bottom,  and  on  each  side,  the  superior 
orifice  of  the  optic  foramen,  a  cylindrical 
canal  directed  obliquely  downwards,  for- 
wards, and  outwards,  to  reach  the  orbital 
hiatus ;  the  supra-sphenoidal  or  pituitary 
fossa,  also  named  the  sella  Turcica,  a  slight 
depression,  limited  behind  by  a  scarcely 
noticeable  transverse  projection  separating 
it  from  the  superior  channel  of  the  basilar 
process.  2.  On  the  sides,  and  in  front,  the 
internal  surface  of  the  wings,  depressed  by 
very  superficial  digital  impressions  ;  more 
behind  and  outwards,  a  fossa,  elongated 
from  before  to  behind,  which  lodges  the 
mastoid  lobule  of  the  brain  ;  between  this 
fossa  and  the  sella  Turcica,  two  vertical 
fissures — an  internal,  named  the  cavernous 
sinus,  and  an  external,  wider  and  deeper, 
for  the  passage  of  a  large  nervous  branch. 
These  two  fissures  open  below,  near  the 
junction  of  the  three  supra-sphenoidal  canals. 
Two  of  these,  which  are  very  wide,  are  placed 
one  before  the  other,  and  separated  only  by 
a  slight  partition.  The  superior  of  these  con- 
stitutes the  great  sphenoidal  fissure  {foramen 
lacerum  orhitale)  ;  the  other,  the  lower,  is  the 
foramen  rotundum,  and  opens  into  the  orbital 
hiatus.  The  third,  very  small  {foramen  pathe- 
ticiim),  is  situated  outside  the  great  anterior 
canal,  opens  above  the  optic  foramen,  within 
the  bony  mass  surmounting  the  hiatus,  and 
sometimes  on  the  free  margin  of  this  lamina. 

Borders. — The  superior  is  a  little  con- 
cave, and  shows,  in  its  middle,  the  superior 

extremity  of  the  body,  mammillated  and  articulated  with  the  summit  of 
the  basilar  process  ;  on  each  side,  two  notches  which  circumscribe  below  the 
occipito-spheno-temporal  hiatus  {foramen  lacerum  basis  cranii).  The  internal 
notch  is  the  narrowest,  and  from  its  affording  a  passage  for  the  internal  carotid 
artery,  is  called  the  carotid  notch ;  it  is  continued  on  the  external  face  of  the 


POSTERIOR  BONES  OF  THE  HEAD  OF  A 
FOETUS  (horse)  AT  BIRTH,  DISARTICU- 
LATED   AND    viewed    in    FRONT. 

A,  Sphenoid  bone  :  1,  ma.xillary  notch  ;  2, 
carotid  notch  ;  3,  groove  for  the  passage 
of  the  maxillary  nerve  ;  4,  cavernous 
sinus ;  5,  optic  fossa ;  6,  great  wing  ; 
6',  unossified  portion  of  the  great  wing; 
7,  notch  for  the  formation  of  the  orbital 
foramen.  B,  Vomer.  C,  Palatine  bone. 
D,  Malar  bone.  E,  Supermaxilla  :  8, 
inferior  orifice  of  the  raaxillo-dental 
canal.     F,  Premaxillary  bone. 


5^  THE  BONES. 

bone  by  a  smooth  excavation  to  which  Rigot  has  given  the  name  of  carotid  fossa. 
The  external  is  also  prolonged  on  the  exterior  surface  of  the  sphenoid,  by  a  short 
and  wide  fissure  ;  it  lodges  the  inferior  maxillary  nerve.  Outside  this  is  another 
very  narrow  notch,  intended  for  the  passage  of  the  middle  meningeal  artery. 
The  fibro-cartilaginous  substance  that  partly  fills  the  occipito-spheno-temporal 
hiatus,  transforms  these  notches  into  foramina,  the  first  of  which  is  named  the 
carotid  canal ;  the  second,  the  foramen  ovale ;  and  the  third,  the  foramen  spinosum. 
The  inferior'  border,  also  concave,  is  likewise  divided  into  three  portions,  a  middle 
and  two  lateral.  The  first  is  thick,  and  formed  by  the  inferior  extremity  of  the 
body  ;  it  is  excavated  by  two  large  cavities  belonging  to  the  sphenoidal  sinus. 
These  cavities  are  separated  from  one  another  by  a  vertical  osseous  plate,  often 
perforated,  which,  at  an  early  period,  is  fused  with  the  perpendicular  lamina  of 
the  ethmoid  bone.  The  very  thin  lateral  portions  form  part  of  the  circum- 
ference of  the  wings  ;  they  are  notched  near  their  union  with  the  middle  piece 
to  assist  in  the  formation  of  the  orbital  foramen.  The  ttvo  lateral  borders  are 
thin  and  convex  in  their  anterior  half,  as  is  also  the  contour  of  the  wings,  which 
are  mortised  in  the  frontal  bone.  For  the  remainder  of  their  extent  they  are 
thick,  denticulated,  and  bevelled  at  the  expense  of  the  external  plate,  to  articulate 
with  the  squamous  portion  of  the  temporal  bone. 

Structure. — This  bone  is  compact  on  its  sides,  and  spongy  in  its  middle  part ; 
inferiorly,  it  is  excavated  by  the  sphenoidal  sinuses. 

Development. — It  is  developed  from  two  principal  nuclei  of  ossification  ;  a 
superior  forms  the  subsphenoidal  process  and  the  canal  of  the  same  name,  the 
Vidian  fissure,  pituitary  fossa,  fissures  of  the  internal  face,  and  the  most  posterior 
of  the  great  supra-sphenoidal  canals  ;  the  other,  the  inferior,  forms  that  portion 
of  the  body  hollowed  by  the  sinuses,  the  lateral  alas,^  and  the  optic  fossa  and 
canals.  In  meeting  each  other,  these  centres  form  the  Vidian  canal  and  the  two 
anterior  supra-sphenoidal  canals.  They  are  not  consolidated  with  each  other 
until  a  very  late  period  ;  for  which  reason  they  are  sometimes  described  as  two 
distinct  bones.  M.  Tabourin  has  even  proposed  to  attach  the  description  of  the 
inferior  sphenoid  to  that  of  the  ethmoid,  because  it  is  united  with  this  bone  a 
long  time  before  it  is  joined  to  the  superior  portion.^ 

Differential  Characters  in  the  Sphenoid  Bone  op  other  Animals. 

A.  Ox. — In  the  Ox,  the  subsphenoidal  or  pterygoid  processes  are  large  and  thin  The 
subsphenoidal  canal  is  absent.  The  sella  Turcica  is  deep,  and  the  bony  projection  separating 
it  from  the  basilar  process  is  very  high.  The  three  supra-sphenoidal  canals  are  converted  into 
a  single,  but  wide  one.  There  are  no  notches  in  tlie  superior  border,  for  the  passage  of  the 
internal  carotid  and  spheno-spinous  arteries.  The  oval  foramen  is  entirely  confined  to  this 
bone. 

B.  Sheep. — In  the  Sheep,  the  osseous  prominence  that  limits  the  pituitary  fossa  posteriorly 
forms  a  lamina  curving  forwards,  and  prolonged  at  its  extremities  into  two  points,  which 
constitute'  the  posterior  clinoid  processes. 

C.  Camel.— The  sphenoid  is  longer  and  tliicker  than  in  the  Ox.  The  subsphenoidal 
or  pterygoid  processes  are  narrow  and  very  thick.  The  oval  foramen  is  relatively  small.  The 
optic  canals  are  covered  at  their  internal  ojiening  by  a  bony  plate.  The  optic  fossa  is  nearly 
on  a  level  with  the  pituitary  fossa. 

D.  Pig. — The  sphenoid  of  the  Pig  is  very  short,  but  the  subsphenoidal  processes  are 
extraordinarily  developed,  and  flattened  before  and  behind.  There  is  no  subsphenoidal  canal, 
and  the  sella  Turcica  is  deep,  and  limited  behind  by  a  very  salient  crest.     A  single  canal 


These  wings  are  not  analogous  to  those  portions  of  the  sphenoid  bone  in  Man  bearing  the 
(  name.     They  are  the  processes  of  Ingrassias  enormously  developed. 
Tabourin,  Journal  de  Med.  Ve'tifrinaire,  p.  229.    Published  at  Lyons,  1845. 


THE  READ. 


replaces  the  tbiameu  rotimdum  and  the  great  sphenoidul  fissure,  as  in  the  Ox.     The  wings, 
shghtly  salient,  are  articulated  by  suture  witli  the  frontal  bone. 

E.  Dog,  Cat. — The  superior  sphenoid  of  the  Dog  is  very  short,  and  bears,  laterally,  two 
wide  wings  which  ascend  to  the  temporal  fossa ;  they  correspond  to  those  of  the  sphenoid  bone 
in  Man.  The  inferior  sphenoid  is,  on  the  contrary,  very  narrow,  and  its  lateral  prolongations, 
or  processes  of  Ingrassias,  are  reduced  to  very  small  proportions.  The  subsphenoidal  or 
pterygoid  process  is  very  short,  and  the  canal  is  single,  and  communicates  witli  the  foramen 
rotundum.  The  pituitary  fossa  is  shallow,  limited  behind  and  before  by  the  posterior  clinoid 
and  anterior  clinoid  processes,  so  named  because  of  their  being 

compared  to  the  four  posts  of  an  ancient  bed.  The  supra- 
sphenoidal  canals  are  only  two  in  number:  one  represents 
the  great  sphenoidal  fissure,  the  other  the  round  foramen. 
The  carotid  notch,  joining  a  similar  one  in  the  temporal 
bone,  forms  an  opening  which  may  be  designated  the  carotid 
foramen,  because  it  gives  passage  to  an  extremely  remark- 
able loop  the  internal  carotid  artery  describes  after  passing 
through  the  carotid  canal.  The  oval  foramen  is  the  same  as 
in  the  Ox. 

In  the  Cat  there  is  the  same  disposition,  with  the  excep- 
tion of  no  sphenoidal  canal  or  carotid  notch  being  present. 

F.  Rabbit.— The  body  of  the  sphenoid  is  short,  tri- 
angular, thick  at  its  upper  border,  pierced  in  the  middle  by 
an  orifice  which  opens  into  the  pituitary  fossa.  Tlie  wings 
are  very  developed ;  the  subsphenoidal  processes,  bifid,  are 
closely  embraced  by  the  pterygoids  and  palatine  bones ;  and 
the  optic  fossa  is  replaced  by  a  large  foramen,  which  com- 
municates at  the  same  time  with  the  two  orbital  fossae. 


6.  Tempokal  Bone  (Figs.  26,  33). 


HEAD  OF  THE  RABBIT  (POS- 
TERIOR face). 
Occipital  tuberosity;  2,  sty- 
loid process  of  the  occipital 
bone  ;  3,  condyle  of  ditto  ;  4, 
tympanic  bulb ;  5,  basilar  pro- 
cess of  the  occipital  bone ;  6, 
body  i)f  the  sphenoid  ;  7,  ptery- 
goid bone;  8,  zygomatic  bone  ; 
9,  9,  condyles  of  the  temporal 
bone;  10,  palatine  bone;  11,  11, 
superior  maxillary  bone;  12, 12, 
premaxilla;  13,  orbital  pro- 
cess of  the  fi-ontal  bone  ;  14,  14, 
superior  double  incisors. 


The  temporal  ■  bones  enclose  the  cranial  cavity 
laterally,  and  articulate  with  the  occipital,  parietal, 
frontal,  sphenoidal,  and  malar  bones  ;  also  with 
the  inferior  maxilla  and  the  hyoid  bone.  Each 
is  divided  into  two  pieces,  which  are  never  consoli- 
dated in  the  horse  ;  one  forms  the  squamous  portion 
of  the  temporal  bone  ;  the  other,  the  petrous  portion. 
They  will  be  described  separately. 

Squamous  -portion. — This  is  flattened  on  both 
sides,  oval,  and  slightly  incurvated  like  a  shell,  a 
shape  to  which  it  owes  its  name.  It  offers  for 
study  an  external  and  an  internal  face.,  and  a  circum- 
ference. 

Faces. — The  external  face  is  convex,  and  marked 
by  some  muscular  imprints,  vascular  fissures,  and 
openings  which  penetrate  the  parieto-temporal  canal. 
It  forms  part  of  the  temporal  fossa,  and  gives  origin  near  its  middle  to  the  zygomatic 
process — a  long  eminence  which  at  first  runs  outwards,  and  soon  curves  forwards 
and  downwards  to  terminate  in  a  thin  summit.  The  base  of  this  eminence  forms, 
in  front,  a  concave  surface  belonging  to  the  temporal  fossa  ;  behind,  it  offers  the 
articular  surface  which  corresponds  with  the  maxillary  bone.  The  latter  is  com- 
posed of  :  1.  A  condyle  transversely  elongated,  convex  above  and  below,  and  slightly 
concave  from  side  to  side.  2.  A  glenoid  cavity,  limited  below  by  the  condyle,  above 
by  a  mammilif orm  eminence,  the  supra-condyloid  (or  anterior  mastoid)  process^ 

'  In  Man  this  is  represented  by  the  inferior  or  vertical  ramus  of  the  upper  root  of  the 
zygomatic  process. 


60  THE  BONES. 

against  %yhich  rests  the  maxillary  condyle  when  this  bone  is  drawn  backwards  ;  it 
is  immediately  above  this  eminence  that  the  inferior  orifice  of  the  parieto-temporal 
canal  (mastoid  foramen)  opens.  The  external  face  of  the  zygomatic  process  is 
smooth  and  convex  ;  the  internal,  concave,  is  also  smooth,  and  bordered  outwards 
by  the  temporal  fossa.  Its  anterior  border  is  sharp  and  convex  ;  the  posterior,  very 
short,  is  thick  and  roughened.  Its  summit  is  ilattened  from  before  to  behind,  and 
marked  by  notches  on  its  two  faces  ;  it  somewhat  resembles  a  wedge,  fixed  as  it  is 
between  the  orbital  process  of  the  frontal  bone  and  the  zygoma  ;  it  comes  in  contact 
with  the  maxillary  bone,  and  by  a  small  portion  of  its  anterior  face,  which  is 
deprived  of  notches,  it  concurs  in  circumscribing  the  orbital  cavity.  In  the 
domesticated  animals,  as  in  Man,  the  zygomatic  process  appears  to  arise  from  the 
surface  of  the  bone  by  two  roots — one,  the  inferior  or  transverse,  is  represented  by 
the  condyle  ;  the  other,  the  siqjerior,  forms  a  sharp  crest  which  is  continuous  with 
the  anterior  border  of  the  process,  and  above,  joins  the  lateral  crest  of  the  occipital 
protuberance. 

The  internal  or  cerebral  face  of  the  squamous  portion  is  divided  into  two  parts 
by  an  almost  vertical  channel,  which  terminates  above  the  supra-condyloid 
process,  and  which,  meeting  a  similar  furrow  on  the  parietal  bone,  forms  the 
parieto-temporcd  canal.  The  superior  portion  is  of  small  extent,  and  of  a 
triangular  form  ;  it  articulates  by  a  simple  harmonia  suture  with  the  external 
face  of  the  petrous  portion.  The  inferior  part,  the  widest,  present  in  its  middle 
some  cerebral  impressions.  For  the  remainder  of  its  extent  or  circumference,  it 
is  cut  into  a  wide,  dentated,  and  lamellar  bevel,  which  brings  it  in  contact  with 
the  surrounding  bones. 

Circumference. — This  may  be  divided  into  tivo  borders  .-  one,  anterior,  is 
convex  and  united  with  the  parietal  and  frontal  bones  ;  the  other,  posterior,  articu- 
lates with  the  sphenoid  in  its  inferior  moiety,  and  is  provided,  above  the  level  of 
the  supra-condyloid  process,  with  a  deep  notch  which  receives  the  external 
auditory  canal.  Superiorly,  the  two  borders  unite  at  the  summit  in  a  thin  point, 
which  rests  on  the  occipital  bone. 

Structure. — The  squamous  portion  of  the  temporal  bone  is  formed  of  two 
very  thin  compact  plates,  which  have  but  little  spongy  tissue  between  them  ;  the 
latter,  however,  is  very  abundant  in  the  body  of  the  zygomatic  process. 

Development. — It  is  developed  from  a  single  nucleus  of  ossification. 

Petrous  Portion. — This  is  one  of  the  most  interesting  parts  of  the 
skeleton  for  study,  in  consequence  of  its  containing  two  systems  of  cavities  which 
enclose  the  essential  organs  of  hearing.  One  of  these  systems  is  named  the  cavity 
of  the  tympanun  or  middle  ear  ;  the  other  forms  the  interned  ear.  These  cavities 
will  be  studied  when  we  come  to  speak  of  the  auditory  apparatus.  In  the  mean 
time,  only  the  external  surface,  and  the  structure  and  development  of  this  portion 
of  the  temporal  bone,  will  be  noticed. 

It  is  wedged  between  the  antero-lateral  border  of  the  occipital  bone,  the 
lateral  border  of  the  parietal,  and  the  superior  part  of  the  internal  face  of  the 
temporal  shell.  It  represents  a  quadrangular  pyramid,  the  base  of  which  is  turned 
downwards  and  a  little  backwards.  It  will  be  studied  successively  in  four  faces, 
a  summit,  and  base. 

Faces. — The  anterior  face  is  united  by  harmonia  suture  to  the  parietal  bone. 
The  posterior  face  articulates  in  the  same  manner  with  the  occipital  bone.  The 
external  face  lies  against  the  squamous  portion  of  the  bone.  The  internal  face, 
slightly  concave  and  marked  by  very  superficial  digital  impressions,  forms  a  part 


THE  HEAD.  61 

of  the  lateral  wall  of  the  cerebellar  cavity.  It  presents  the  canal  or  internal  audi- 
tory hiatus  {rneatus  auditorius  internus),  a  small  fossa,  the  bottom  of  which  is 
pierced  by  several  foramina  for  the  transmission  of  nerves  ;  the  largest  of  these 
is  the  internal  orifice  of  the  aqimdudus  Fallopii — a  flexuous  canal  which  passes 
through  the  bone  and  opens  at  the  external  surface  of  its  base  ;  the  other 
foramina  penetrate  the  cavities  of  the  internal  ear. 

These  faces  are  separated  from  each  other  by  so  many  borders  or  plane  angles, 
two  of  which  more  particularly  merit  attention  ;  one  of  these  isolates  the  external 
from  the  posterior  face,  and  the  other  separates  the  anterior  from  the  internal 
face.  The  first  is  thick  and  rugged,  and  constitutes  the  mastoid  crest ;  it  is  con- 
tinuous above  with  the  lateral  ridge  of  the  occipital  bone,  after  being  united  to 
the  superior  root  of  the  zygomatic  process,  and  terminates,  near  the  base  of  the 
bone,  by  a  tuberosity  for  muscular  insertion,  to  which  has  been  given  the  name 
of  (poster  io7-)  mastoid  process.  This  border  is  traversed  by  a  slit,  the  mastoid  fissure^ 
which  passes  under  the  squamous  portion  and  enters  the  parieto-temporal  canal. 
The  second  is  thin,  and,  with  the  superior  part  of  the  lateral  border  of  the  parietal 
bone,  forms  the  crest  which  establishes  the  line  of  demarcation  between  the 
cerebral  and  cerebellar  cavities  of  the  cranium  ;  it  gives  attachment  to  the 
tentorium  cerebelli. 

Summit. — This  is  slightly  denticulated,  and  articulates  with  the  occipital  bone. 

Base. — This  is  very  irregular,  and  offers  :  outwardly,  the  external  auditory 
canal  which  penetrates  the  middle  ear,  and  the  external  orifice  of  which  has  been 
named  in  veterinary  anatomy  the  external  auditory  hiatus ;  inwardly,  a  sharp 
crest  which  circumscribes  the  external  contour  of  the  foramen  lacerum  basis  cranii ; 
above,  and  under  the  mastoid  process,  the  stylo-mastoid  or  pre-mastoid  forammi,  the 
external  orifice  of  the  aqueduct  of  Fallopius  ;  below,  the  subuliform  (or  styloid) 
process  for  the  attachment  of  the  tensor  palati  muscle  and  the  Eustachian  tube  : 
this  is  a  long,  thin,  and  pointed  process  presenting,  at  its  base  and  within,  a  canal 
(styloid  foramen)  which  enters  the  cavity  of  the  tympanum,  and  which  is  incom- 
pletely partitioned  by  a  small  bony  plate  into  two  parallel  portions  ;  in  the  centre, 
the  hyoid prolongation  or  vaginal  process  ^ — a  little  cylindrical  eminence  surrounded 
by  a  bony  sheath,  and  the  mastoid  protuberance  or  auditory  bulla — a  slightly  sahent, 
smooth,  and  round  eminence  hollowed  internally  by  numerous  cells,  which  form 
part  of  the  middle  ear. 

The  several  small  and  very  remarkable  canals  which  pass  through  the  petrous 
portion  of  the  temporal  bone,  will  be  noticed  when  the  nervous  and  arterial 
branches  they  lodge  are  described. 

Development. — The  petrous  portion  of  the  temporal  bone  is  developed  from 
two  principal  centres  of  ossification  which  are  consolidated  at  birth,  and  which 
are  often  described  as  two  distinct  portions — the  one  as  the  petrous  or  stony 
portion,  the  other  as  the  mastoid  portion. 

The  faces,  borders,  summit,  and  inner  side  of  the  base  of  the  bone  are  formed 
by  the  petrous  part,  which  contains  the  cavities  of  the  internal  ear  and  furnishes 
the  inner  wall  of  the  middle  ear. 

The  mastoid  portion  constitutes  almost  entirely  the   base  of  the  temporal 
pyramid  ;    to  it  belong  the  external  auditory  canal,  the   mastoid   process,  the 
sheath  of  the  hyoid  prolongation,  and  the  styloid  process  ;  it  forms  the  external 
wall  and  circumference  of  the  case  of  the  tympanum. 
'  This  is  the  analogue  of  the  mastoid  canal  in  Man. 

*  This  process  is  prolonged  by  a  cartilage  that  unites  it  to  the  styloid  hone. 
7 


62  TEE  BONES. 

For  the  petrous  portion  of  the  temporal  bone  there  are  also  two  small  com- 
plementary nuclei  :  one  for  the  vaginal  process — the  base  of  which  is  united  to 
the  petrous  portion,  and  another  forming  the  ring  of  the  tympanum. 

Structure. — The  petrous  portion  is  the  hardest  mass  of  bone  in  the  skeleton, 
and  scarcely  contains  any  spongy  tissue,  except  at  the  centre  of  the  mastoid 
process  ;  in  the  mastoid  portion  it  may  be  said  not  to  exist. 


Differential  Characters  in  the  Temporal  Bone  of  other  Animals. 

In  the  other  domestic  animals,  the  petrous  portion  of  the  temporal  bone  becomes 
consolidated  with  the  squamous  portion,  and  the  summit  of  the  zygomatic  process  only 
articulates  with  the  malar  bone. 

A.  Ox,  Sheep,  Goat.— The  condyle  of  the  zygomatic  process  is  very  wide  and  convex  in 
every  sense.  The  parieto-temporal  canal  is  very  large,  and  entirely  excavated  in  the  temporal 
bone;  its  superior  or  internal  extremity  opens  above  the  petrous  portion  in  an  excavation  which 
represents  the  lateral  cavity  of  the  parietal  protuberance  in  the  Horse ;  at  its  inferior  extremity 
it  always  shows  several  orifices. 

Tiie  mastoid  process  is  very  salient,  and  belon<^s  to  the  squamous  portion.  The  mastoid 
cre.st  is  confounded  with  the  upper  root  of  the  zygomatic  process  ;  iiiferiorly,  it  surpasses  the 
mastoid  process,  and  is  prolonged  to  the  mastoid  protuberance.     Tlie  latter  is  very  voluminous. 

The  subuliform  process  is  larger  and  stronger  than 
in  the  Horse  ;  there  is  no  mastoid  fissure. 

In  the  Sheep  and  Goat,  the  mastoid  process  is 
scarcely  distinct  from  the  crest ;  and  the  mastoid 
portion  of  the  bone  is  only  at  a  late  period  consoli- 
dated with  the  petrous  portion. 

B.  Camel. — The  squamous  portion  of  the 
temporal  is  wider  than  that  of  the  Horse ;  it  is 
excavated  in  tlie  upper  part  of  its  external  surface. 
The  zygomatic  process  has  a  large  and  thin  base; 
its  articular  surface  is  nearly  level  from  before  to 
behind,  and  is  concave  from  one  side  to  the  other ; 
the  supra-condyloid  process  is  very  developed  (Fig. 
45).  The  petrous  portion  is  thin,  and  closely  con- 
fined between  the  occipital  and  squamous  bones. 
The  mastoid  crest  and  process  are  not  markedly 
developed.  The  hyoid  prolongation  is  placed  at  the 
bottom  of  a  great  bony  sheath. 

C.  Pig.— The  articular  surface  of  this  bone 
resembles  that  of  Rodents;  it  is  not  limited  pos- 
teriorly by  a  subcondyloid  eminence,  and,  in  addition, 
offers  a  wider  transverse  surface.  The  zygomatic 
process  articulates  with  the  jugal  bone  by  the  wliole 
extent  of  its  posterior  border.  A  crest  leading  from 
the  external  auditory  hiatus  to  the  mastoid  pro- 
The  mastoid  crest  is,  as  in  the  Ox,  confounded  with 


head  of  the  rabbit  (antero-lateral 
face). 

1,  Occipital  bone ;  2,  parietal ;  3,  tym- 
panic bulb ;  4,  auditory  canal ;  8,  8, 
nasal  bones;  9,  supermaxilla;  10,  pre- 
maxilla;  11,  inferior  maxilla. 


tuberance  replaces   the  mastoid  process, 
the  superior  root  of  the  zygomatic  process. 

D.  Carnivora. — In  tlie  Carnivora,  the  articular  surface  of  the  zygomatic  process  merely 
forms  a  glenoid  cavity,  into  which  the  condyle  of  the  msixillary  bone  exactly  fits.  Tlie 
temporal  bone  in  these  animals  is  alsodistinguisliedby  the  width  of  the  externul  auditorv  canal, 
the  absence  of  a  liyoid  prolongation,  the  small  development  of  the  mastoid  and  styloid  pro- 
cesses, the  enormous  volume  of  the  mastoid  protuberance,  and  the  presence  of  two  particnlar 
canals  which  cannot  be  traced  in  the  other  animals.  One  of  them— the  carotid  mmni-tra verses 
the  mastoid  portion,  and  joins,  superiorly,  the  venous  canal  which  passes  between  the  basilar 
process  and  the  temporal  bone ;  by  its  inferior  extremity  it  joins  the  carotid  foramen,  which 
itself  pern  tiates  the  cranium,  a  little  beyond  the  venous  canal  just  mentioned.  The  other 
conduit  is  pierced  in  the  petrous  portion  immediately  above  the  carotid  canal ;  it  affords  a 
passage  to  tlie  fifth  pair  of  cranial  nerves. 

E.  Rabbit. --Tlie  squamous  portion  is  circular,  and  has  a  shoit  process  flattened  from 
before  to  behind  at  its  base,  and  from  side  to  side  at  its  extremity.     The  articular  surface  is 


TBI,  HEAD.  63 

concave  transversely,  and  elongated  from  before  tobeliind.  The  petrous  portion  has  a  consider- 
able tympanic  bulb  applied  closely  to  the  auditory  canal,  which  is  large  and  obliquo  behind. 
The  mastoid  process  is  a  simple  crest  situated  above  the  auditory  canal ;  the  hyoid  prolongation 
is  absent. 

Bones  of  the  Pace. 

The  face  is  much  more  extensive  than  the  cranimn  in  the  majority  of  the 
domesticated  animals,  and  is  composed  of  two  jmvs — a  bony  apparatus  that  serves 
as  a  support  to  the  passive  organs  of  mastication — the  teeth.  The  superior  or 
anterior  jaiv,  traversed  in  its  entire  length  by  the  nasal  cavities,  is  formed  by 
nineteen  flat  bones,  only  one  of  which,  the  vomer,  is  a  single  bone.  The  pairs 
are  :  the  superior  and  intermaxilJaries  (or  premaxillaries),  the  palate,  piterijgoid, 
malar,  lachrymal,  nasal,  and  superior  and  inferior  turbinated  hones.  Of  these 
only  four — the  maxillaries — are  intended  for  the  implantation  of  the  teeth  ;  the 
others  form  the  union  between  the  cranium  and  the  superior  maxilla,  or  concur 
in  the  formation  of  the  nasal  cavities.  The  loiver  jaw  has  for  its  base  a  single 
bone — the  inferior  maxilla,  or  maxillary  hone.  « 

1.  SuPEEioR  Maxillary  Bone  (Fig.  26). 

This  bone,  also  named  the  supermaxillary  hone,  the  most  extensive  in  the 
upper  jaw,  is  situated  on  the  side  of  the  face,  and  is  bordered  above  by  the 
frontal,  palate,  zygomatic,  and  lachrymal  bones  ;  below,  by  the  premaxillary 
bones  ;  in  front,  'by  the  nasal  bone  ;  behind  and  within,  by  that  of  the  opposite 
side.  It  is  elongated  vertically,  is  irregularly  triangular,  and  exhibits  two  faces, 
two  borders,  and  two  extremities. 

Faces. — The  external  face,  which  is  more  convex  in  the  young  than  the  old 
animal,  presents  :  1.  On  the  level  of  the  fourth  and  fifth  molar  teeth,  a  vertically 
elongated  ridge  which  is  continued  above  with  the  inferior  border  of  the 
zygomatic  bone  ;  this  is  the  maxillary  spine.  2.  The  inferior  orifice  of  the 
maxillo-dental  canal,  or  infra-orbited  foramen. 

The  internal  face  concurs  in  forming  the  external  parietes  of  the  nasal  cavities. 
We  observe,  above  and  in  front,  a  deep,  wide,  and  diverticulated  excavation, 
forming  part  of  the  maxillary  sinus  ;  above  and  behind,  a  surface  roughened  by 
fine  lamellffi  and  denticulations  to  correspond  with  the  palate  bone,  and  traversed 
from  above  to  below  by  a  fissure  which  forms,  in  uniting  with  a  similar  fissure  in 
the  latter  bone,  the  pcdatine  canal.  For  the  remainder  of  its  extent  it  is  unequally 
smooth,  covered  by  the  membrane  of  the  nose,  and  divided  into  two  surfaces  by 
a  slightly  vertical  and  sinuous  crest  that  affords  attachment  to  the  maxillary 
turbinated  bone  :  the  anterior  surface,  which  responds  to  the  middle  meatus  of 
the  nasal  fossa,  shows  the  lower  orifice  of  the  osseous  lachrymal  canal  continued 
by  a  fissure  to  the  lower  extremity  of  the  bone  ;  the  posterior  surface  belongs  to 
the  inferior  meatus.  From  this  face  is  detached,  near  its  inferior  border,  a  wide 
and  long  vertical  plate,  which  forms,  in  Man  and  short-faced  animals,  a  simple 
process — t\iQ  palatine  process.  This  plate,  uniting  in  the  middle  line  with  that  on 
the  opposite  side,  concurs  in  forming  the  greater  portion  of  the  palatine  arch.  It 
shows  :  an  anterior  slightly  concave  face,  forming  the  floor  of  the  nasal  fossae ;  a 
posterior  face,  buccal,  furrowed  by  small  fissures,  perforated  by  fine  openings,  and 
traversed  along  its  length  by  a  somewhat  wide  groove — the  pcdatine  fisstfre,  which 
commences  above  at  the  lower  orifice,  of  the  palatine  canal ;  a  denticulated  border 


61  THE   BONES. 

which  articulates  with  a  similar  border  on  the  palatine  process  of  the  opposite 
side. 

Borders. — The  anterior,  thin  and  convex,  is  divided  into  two  parts  :  an 
inferior,  which  is  mortised  to  receive  the  external  border  of  the  nasal  bone  and 
the  external  process  of  the  premaxilla  ;  and  a  superior,  cut  in  a  wide  bevel,  at 
the  expense  of  the  external  plate,  to  respond  to  the  lachrymal  and  zygomatic 
bones.  The  external  border  is  very  thick,  and  hollowed  into  six  large  quadrilateral 
cavities,  named  alveoli,  in  which  are  implanted  the  molar  teeth.  Above  the  last 
alveolus  it  forms  a  rugged  eminence  designated  the  alveolar  tuberosity ;  below  the 
first  alveolus  it  becomes  thin  and  sharp,  and  constitutes  part  of  the  interdental 
space  {diastema)  which  separates  the  molar  from  the  incisor  teeth. 

Extremities. — The  superior  is  the  thickest,  and  represents  a  smooth  rounded 
protuberance,  into  the  interior  of  which  the  maxillary  sinus  is  prolonged.  Above 
and  within  this  eminence  is  a  wide  and  deep  excavation,  in  the  formation  of 
which  the  palate  bones  participate.  This  is  the  maxillary  hiatus,  situated  directly 
opposite  the  orbital  hiatus.  At  the  bottom  of  this  cavity  is  seen  the  nasal 
foramen,  as  well  as  the  upper  orifice  of  the  infra-orbital  and  the  palatine 
canals.  The  nasal  foramen  belongs  to  the  palate  bone,  and  enters  the  nasal  cavity. 
The  infra-orhital  cayial  traverses  the  maxillary  sinus  in  passing  above  the 
roots  of  the  molar  teeth,  and  terminates  by  two  branches — one,  short  and 
wide,  which  opens  on  the  external  surface  of  the  bone,  on  a  level  with  the 
third  molar  ;  the  other,  very  narrow,  continues  the  course  of  the  canal  in  the 
substance  of  the  bone,  and  is  prolonged  by  several  small,  very  fine  branches 
into  the  premaxillary  bone.  The  palatine  canal,  channeled  between  the  super- 
maxillary  and  the  palate  bone,  extends  from  the  maxillary  hiatus  to  the  palatine 
fissure. 

The  inferior  extremity  presents  a  cavity  which  forms  the  alveolus  of  the  tusk, 
by  uniting  with  a  similar  space  in  the  premaxillary  bone. 

Structure  and  develojyment. — This  bone  is  developed  from  a  single  nucleus,  and 
is  the  more  spongy- — particularly  towards  the  alveolar  border  and  the  superior 
extremity — as  the  animal  is  young. 

Differential  Characters  in  the  Superior  Maxillary  Bone  of  the  other  Animals. 

A.  Ox,  Sheep,  Goat. — In  the  Ox,  Sheep,  and  Goat,  the  maxillary  spine  does  not  directly 
join  the  zygomatic  crest ;  a  curved  line,  with  concavity  posterior,  effects  the  union  between 
these  two  parts.  The  inferior  oriiice  of  the  infra-orbital  foramen  is  pierced  above  the  first 
molar  tooth.  There  is  no  fissure  for  the  formation  of  the  palatine  canal.  Tlie  cavity  of  the 
sinus  is  more  spacious  than  in  the  Horse,  and  is  prolonged  (in  the  Ox  only)  between  the  two 
laminae  of  the  palatine  roof.     There  is  no  alveolus  for  the  tusk. 

B.  Camel. — Not  so  long  or  wide  as  in  the  Horse  and  Ox,  the  supermaxilla  of  the 
Camel  is  deeply  excavated  iibove  the  forehead  and  the  orbit.  The  maxillary  spine  is  replaced 
by  a  round  and  i?mooth  prominence,  which  disappears  at  the  inferior  opening  of  the  superior 
dental  canal,  pierced  above  the  interval  separating  the  second  from  the  third  molar.  The 
posterior  face  of  the  palatine  process  is  narrow,  has  no  palatine  fissure,  but  shows  the  orifice 
of  the  palatine  canal. 

C.  Pig. — In  the  Pig,  the  external  surface  of  this  bone  is  hollowed  in  its  middle,  and 
presents  in  front  a  voluminous  relief  formed  by  the  alveolus  of  the  canine  tooth.  The  cavity 
is  entirely  formed  in  the  supermaxilla.  There  is  no  alveolar  tuberosity,  and  the  interdental 
spaoe  is  very  short,  while  the  cavity  for  the  sinus  is  little  developed.  The  lower  orifice  of  the 
palatine  canal  is  even  pierced  in  the  substance  of  the  supermaxilla. 

D. — Dog,  Cat. — In  Carnivora,  this  bone  is  very  short;  its  anterior  border  offers  a  long 
process  analogous  to  the  nasal  spiiie  of  Man.  It  alone  furnishes  the  alveolus  of  the  tusk. 
The  palatine  canal,  pierced  entirely  in  the  bone  of  that  name,  nevertheless  opens,  by  its 


TBE  HEAD. 


65 


inferior  extremity,  at  tlie  junction  of  the  supermaxilla  with  the  palatine  bone.     The  maxillary 
sinus  is  not  very  spacious,  and  there  is  no  maxillary  spine  (Fig.  29). 

E.  Rabbit. — The  superior  maxilla  in  this  animal  is  less  extensive,  proportionately,  than 
that  of  the  other  animals.  The  external  table  is  thin,  and  even  cribriform.  The  malar  tubercle 
is  narrow  and  directed  outwards.  The  palatine  process  is  very  narrow,  and  therefore  only 
very  slightly  concurs  in  the  formation  of  the  arch  of  the  palate ;  it  does  not  extend  to  the 
summit  of  the  internal  process  of  the  incisive  bone  (Fig.  36). 

Fig.  37. 


ox's   HEAD   (POSTERIOR   FACE), 

A,  Parietal  bone:  1.  occiintal  foramen;  2,  occipital  condyle;  3,  styloid  process  of  that  bone; 
4,  condyloid  foramina;  5,  mastoid  process;  6,  mastoid  protuberance;  7,  subuliform  (temporal) 
process;  8,  hyoideal  sheath  ;  9,  stylo-mastoid  foramen  ;  10,  external  auditory  hiatus  ;  11,  inferior 
orifice  of  the"  parieto-temporal  canal;  12,  temporal  condyle;  13,  posterior  foramen  lacerum ; 
14,  oval  foramen  ;  17,  subsphenoidal  process  ;  18,  orbital  hiatus  ;  19,  optic  foramen.  B,  Frontal 
bone  :  20,  supra-orbital  foramen  ;  21,  orbital  foramen ;  22,  lachrymal  protuberance.  C,  Malar  bone  : 
23,  pterygoid  bone,  d.  Palatine  bone  :  24,  nasal  foramen  ;  25,  inferior  orifice  of  the  palatine 
canal.  E,  Supermaxillary  bone  :  26,  maxillary  spine.  G,  Premaxillary  bone :  27,  its  internal 
process  ;  28,  external  process ;  29,  incisive  openings. 

2.  Premaxillaey,  Inteemaxillary,  or  Incisive  Bone  (Figs.  26,  38). 

This  bone  occupies  the  inferior  extremity  of  the  head,  and  is  composed  of  a 
thick  prismatic  jwrtion,  lengthened  superiorly  by  two  long  processes. 

Thick  portion  or  base. — This  presents  a  solid  mass  with  three  faces  :  an 
external  or  labial,  smooth  and  convex  :  an  internal,  denticulated  for  union  with  the 
opposite  bone,  and  traversed  from  before  to  behind  by  an  inflexed  fissure,  which 
forms,  with  an  analogous  one  in  the  other  premaxilla,  the  incisive  canal  or  fora- 
men incisivum  ;  the  third  or  posterior,  also  called  the  buccal,  is  slightly  concave,  and 


66 


THE  BONES. 


shows  the  continuation  of  the 
foramen.     These  three  faces 

Fig.  38. 


POSTERIOR   ASPECT   OF    HORSE'S 
SKULL. 

,  Occipital  tuberosity ;  2,  fora- 
men magnum ;  3,  3,  occipital 
condyles  ;  4,  4,  styloid  pro- 
cesses ;  5,  5,  petrous  bone ;  6, 
basilar  process ;  7,  pterygoid 
fissure  of  the  sphenoid  bone  ;  8, 
foramen  lacerum  ;  9,  9,  supra- 
condyloid,  or  anterior  mastoid 
process  ;  10,  10,  articular  emi- 
nence, or  temporal  condyle ;  11, 
body  of  sphenoid  bone ;  12,  ptery- 
goid process  ;  13,  ethmoid  bone  ; 
14,  temporal  bone  and  sphenoidal 
sutuie;  15,  lachrymal  bone;  16, 
vomer;  17,  malar  bone;  18, 
maxillary  tuberosity  ;  19,  pos- 
terior nares,  or  guttural  opening 
of  the  nose ;  20,  palatine  bone ; 
21,  palatine  styloid  process  ;  22, 
palato-maxillary  foramen;  23, 
palatine  process  of  superior 
maxillary  bone,  with  suture  ;  24, 
ditto  of  premaxillary  bone;  25, 
premaxillary  bone ;  26,  upper 
incisor  teeth  ;  27,  point  of  junc- 
tion of  the  premaxillary  with 
the  supermaxillary  bone  ;  28,  up- 
per molar  teeth  (young  mouth). 


palatine  groove,  which  terminates  in  the  incisive 
are  separated  by  as  many  borders  :  two  internah 
hmitiug  the  corresponding  face  before  and  be- 
hind ;  and  an  external,  separating  the  labial  from 
the  buccal  face.  The  latter  only  merits  notice. 
It  is  very  thick,  and  is  divided  into  two  parts  : 
an  inferior,  which  describes  a  curved  line,  con- 
cavity upwards,  and  is  excavated  by  three  alveoli 
for  the  reception  of  the  incisor  teeth  ;  another,  the 
superior,  is  straight,  vertical,  and  somewhat  sharp, 
and  forms  part  of  the  dental  interspace.  It  is 
limited  above,  near  the  base  of  the  external  process, 
by  a  cavity  for  the  formation  of  the  alveolus  of 
the  canine  tooth. 

Processes. — These  are  distinguished  as  external 
and  intei'iial.  The  first,  the  longest  and  strongest, 
is  flattened  on  both  sides  ;  its  external  face  is 
smooth,  and  continued  with  that  of  the  thick  por- 
tion of  the  bone  ;  its  internal  face  is  covered  by 
the  mucous  membrane  of  the  nose  ;  the  anterior 
border  is  smooth  and  rounded ;  the  posterior, 
denticulated  to  respond  to  the  supermaxillary  bone, 
is  in  contact  with  the  external  border  of  the  base  ; 
its  summit  is  thin,  and  is  insinuated  between  the 
latter  and  the  nasal  bone.  The  internal  {ox palatine) 
process,  the  smallest,  is  flattened  from  before  to 
behind,  and  forms  a  very  thin  tongue  of  bone,  sepa- 
rated from  the  other  portions  by  a  narrow  and  very 
deep  notch,  named  the  incisive  opening  or  cleft.  Its 
inferior  face  constitutes  a  small  portion  of  the  floor 
of  the  nasal  fossae  ;  the  posterior,  continuous  with 
the  same  face  of  the  principal  mass  of  the  bone, 
forms  part  of  the  palatine  roof  ;  its  external  border 
circumscribes,  inwardly,  the  incisive  opening  ;  the 
internal  is  united  by  dentated  suture  with  the 
opposite  bone. 

Structure  and  development. — It  is  a  spongy 
bone,  developed  from  a  single  nucleus. 

Differential  Characters  in  the  Premaxillary  Bone 
OF  OTHER  Animals. 

A.  Ox,  Sheep,  Goat  (Fig.  37).— Tlie  iuferior  or  prin- 
cipal portion  of  this  bone  is  flattened  befure  and  behind, 
and  deprived  of  alveoli  in  its  external  border;  neither  is  there 
any  incdsive  foramen.  It  is  rarely  consolidated  with  the 
adjacent  bones,  and  is  never,  in  the  smaller  Ruminants 
(Sheep  and  Goat),  articulated  with  the  nasal  bone  by  the 
summit  of  the  external  process. 

B.  Camel. — By  its  form,  tlie  premaxillary  bone  much 
resembles  that  of  the  smaller  Ruminants.  Its  base  is 
not  so  wide,  but  it  is  thicker  than  in  the  Ox.  This  base  is 
rugged  in  its  lower  surface,  and  excavated  by  an  alveolar 


THE  HEAD. 


67 


cavity.     The  incisive  opening  is  very  small,  and  the  external   process   does  not   reacli   the 
nasal  bone. 

C.  Pig. — In  the  Pig,  the  external  process  of  tlie  premaxillary  bone  is  very  long  and  wide 
at  its  base,  and  consolidated  with  the  nasal  bone  fur  about  the  upper  two-thirds  of  its  length. 
There  is  no  incisive  foramen  or  cavity  for  the  tusk.     The  incisive  openings  are  oval. 

D.  Dog,  Cat. — Of  small  size,  the  premaxilla  of  Carnivora  has  no  incisive  foramen  or 
alveolar  cavity  for  the  canine  tooth.     The  incisive  open- 
ings are  the  same  as  in  the  Pig.  Fig.  39. 

E.  Rabbit.— Proportionately  voluminous,  the  pre-  r  ^ 
maxilla  of  the  Rabbit  is  remarkable  for  the  great  de-                        '^                   ^ 
velopnient  of  its  ascending  processes,  which  reach  the              _     ^  {^mWI^^S^^  f 
frontal  bone,  and  the  width  of  the  incisive  slits,  which 
are  conlounded  above  the  internal  processes.     It  carries 
two  incisors,  placed  one  before  the  other. 


3.  Palatine  Bones  (Fig.  38). 

The  folate  or  palatine  hones  are  situated  be- 
tween the  supermaxillaries,  at  the  margin  of  the 
guttural  opening  of  the  nasal  cavities,  and  are 
articulated  with  the  sphenoid,  ethmoid,  vomer, 
frontal,  and  pterygoid  bones.  Elongated  from 
above  to  below,  flattened  laterally,  and  curved 
towards  each  other  at  their  inferior  extremity, 
which  is  flattened  from  before  to  behind,  these 
bones,  though  irregular  in  shape,  offer  for  study 
two  faces,  tivo  herders,  and  two  extremities. 

Faces. — The  external  face  of  the  palate  bone 
is  divided  into  three  fractions — a  superior,  or 
orbital,  an  inferior,  or  palatine,  and  a  middle,  or 
articular.  The  first  is  smooth  and  slightly  ex- 
cavated, and  participates  in  the  formation  of  the 
maxillary  hiatus  ;  it  shows  a  small  groove,  the 
staphyloid,  which  reaches  the  palatine  fraction 
in  passing  between  the  posterior  border  of  the 
bone  and  the  alveolar  tuberosity.  The  second  is 
not  extensive,  and  looks  backwards  in  conse- 
quence of  the  antero-posterior  flattening  which 
the  bone  presents  at  its  inferior  extremity  ;  it 
forms  part  of  the  roof  of  the  palate.  The  third 
presents  a  lamellar  and  denticulated  surface 
which  corresponds  to  a  similar  face  on  the 
superm axillary  bone,  and  is  channeled  from 
above  to  below  by  the  internal  groove  of  the 
palatine  canal. 

The  interned  face,  smooth  and  concave,  forms 
part  of  the  external  wall  and  the  floor  of  the 
nasal  fossa. 

Borders. — The  anterior  is  indented,  near  its  superior  third,  by  a  deep  notch, 
which  is  often  converted  into  a  foramen,  the  nasal.  Below  this  notch  the  bone 
is  thin  and  denticulated  for  union  with  the  supermaxillary  bone  ;  above,  its  two 
plates  separate  widely  from  one  another,  giving  rise  to  a  very  spacious  cavity 


HEAD  OF  THE  PIG  (POSTERIOR  FACE). 

1,  Occipital  tuberosity ;  2,  occipi- 
tal foramen;  3,  occipital  con- 
dyle; 4,  condyloiil  foramen;  5, 
basilar  process  ;  6,  6,  mastoid  crest; 
7,  styloid  process  of  the  occipital 
bone  ;  8,  articular  surface  of  the 
temporal  bone ;  9,  mastoid  protu- 
berance ;  10.  foramen  lacerum ;  1 1, 
subsphenoidal  process  —  external 
wing  of  pterygoid  process ;  12, 
palatine  crest ;  13,  pterygoid  bone 
(internal  wing  of  the  ])terygoid 
process)  ;  14,  inferior  orifice  of  the 
palatine  canal ;  15,  15,  incisive 
openings. 


TEE  BONES. 


which  forms  part  of  the  sphenoid  sinus.  The  posterior  border  presents,  above, 
a  rugged  crest  called  the  palatine,  flattened  from  side  to  side,  bent  outwards,  and 
bordered  at  its  base  and  inwards  by  a  very  narrow  synarthrodia!  surface,  which 
responds  to  the  pterygoid  bone.  It  is  smooth  and  concave  in  its  inferior  half, 
and  forms,  with  that  of  the  opposite  side,  a  parabohc  arch  (palatine  arch)  which 
circumscribes,  below  and  at  the  side,  the  double  guttural  orifice  of  the  nasal 
cavities. 

Extremities. — The  superior,  flattened  on  both  sides,  is  bevelled  on  the  external 
side  to  articulate  with  the  subsphenoidal  process.  The 
inferior,  flattened  from  before  to  behind,  is  curved 
inwards  and  united  by  simple  suture  with  that  of  the 
opposite  bone. 

Structure  and  deveJopment. — This  is  a  very  com- 
pact bone,  developed  from  a  single  centre  of  ossifi- 
cation. 

Differential  Characteks  in  the  Palatine  Bone  in 
OTHER  Animals. 

The  principal  distinctive  feature  of  this  bone  in  the  different 
domestic  animals  is  due  to  the  part  it  takes  in  forming  the 
arch  of  the  palate.  In  this  respect  there  are  very  great  differ- 
ences in  various  species,  but  in  none  of  them  is  tliis  part  so 
reduced  as  in  Solipeds,  in  which  the  bone  is  scarcely  equal  to 
one-fifth  of  tlie  palatine  surface. 

A.  Ox,  Sheep,  G-oat. — Tlie  palatine  bone  in  these  animals 
is  very  developed,  and  noticeable  for  the  considerable  extent  of 
the  palatine  portion  of  its  external  surface.  The  palatine  canal 
is  entirely  channeled  out  in  its  substauce.  The  palatine  crest, 
very  thin  and  elevated,  is  formed  altogether  by  the  posterior 
border  of  the  palate  bone,  the  pterygoid,  and  the  subsphenoidal 
process.  There  is  no  excavation  for  the  sphenoidal  sinuses ; 
but,  instead,  all  that  part  of  the  bone  which  enters  into  the  roof 
of  the  palate  is  hollowed,  but  in  the  Ox  only,  by  irregular 
cavities  which  communicate  with  the  maxillary  sinus  of  the 
same  side.     The  nasal  foramen  is  very  wide. 

B.  Camel. — The  staphyline  fissure  is  wide  and  deep ;  the 
palatine  crest  is  very  developed,  and  has  two  rugged  depressions 
at  its  base.  The  palatine  canal  is  not  included  in  the  palate 
bone ;   it  opens  at  the  second  molar. 

C.  Pig. — The  palatine  portion  is  leas  developed  than  in 
Ruminants,  for  it  forms  less  tlian  one-fourth  of  the  palatine 
arch  ;  on  the  other  hand,  the  orbital  portion  is  very  limited. 
The  palatine  crest  is  rt-placed  by  a  tuberosity,  against  which 
rests,  outwardly,  the  subsphenoidal  process,  and  inwardly  the 
pterygoid  bone.  The  union  of  these  three  parts  constitutes,  on 
tlie  posterior  surface  of  the  head,  a  thick  and  very  remarkable 
trifid  projection  or  mamelon. 

D.  Dog,  Cat.— It  is  in  the  Carnivora  that  the  palatine  bones 
are  of  greatest  extent  in  their  proper  palatine  portion,  as  they 
constitute  nearly  one-half  of  the  palatine  arch.  They  have  no 
share  in  t)ie  formation  of  the  sphenoidal  sinuses,  but  furnish  a 
small  excavation  to  the  maxillary  sinuses. 

E.  Rabbit. — The  palatine  bones  resemble  those  of  the  Horse, 
with  regard  to  the  part  they  play  in  forming  the  palatine  arch. 
The  palatine  canal  opens  also  between  the  palatine  and  superior 
maxillary  bones,  but  the   palatine   crests   are   proportionately 

more  developed  than  in  Solipeds  (Fig.  35). 


dog's  head  (posterior  face). 

1,  Occipital  tuberosity ;  2, 
occipital  foramen ;  3,  occi- 
pital condyle ;  4,  condyloid 
foramen  ;  5,  styloid  process 
of  the  occipital ;  6,  mastoid 
protuberance ;  7,  concave 
temporo-maxillary  articular 
surface  ;  8,  supra-condy- 
loid  eminence ;  9,  inferior 
orifice  of  the  parieto-tem- 
poral  canal ;  10,  posterior 
foramen  lacerum ;  11, 
ditto,  anterior.  On  the  op- 
posite side  at  a  is  shown 
the  orifice  communicating 
with  the  Eustachian  tube 
and  the  tympanum  ;  at  h 
the  passage  for  the  carotid 
loop.  12,  Body  of  the 
sphenoid ;  13,  oval  fora- 
men ;  14,  inferior  orifice  of 
the  subsphenoidal  canal  ; 
15,  pterygoid  bone;  16, 
nasal  surface  of  the  palate 
bone;  17,  palatine  surface 
of  the  same;  18,  vomer; 
19,    supermaxillary    bone ; 


20. 


incisive  opening. 


THE  HEAD.  69 

4.  Pteeygoid  Bone  (Figs.  34,  38).* 

A  small  and  very  short  bone,  elongated  from  above  to  below,  flattened  on 
both  sides,  and  situated  on  the  inner  aspect  of  the  subsphenoidal  process,  but 
external  to  the  vomer. 

Its  external  face  is  in  contact  with  the  palate  and  sphenoid  bones  ;  the 
internal  is  smooth,  and  covered  by  the  pharyngeal  mucous  membrane.  Its 
superior  extremity  is  tapering,  and  concurs  in  forming  the  Vidian  canal ;  the 
inferior  is  thickened  into  a  small  pointed  process  (the  hamular  process),  the 
apex  of  which,  directed  backwards,  offers  outwardly  a  groove  which  serves  as  a 
pulley  to  the  tendon  of  the  tensor  palati  muscle. 

This  bone  is  composed  entirely  of  compact  tissue,  and  is  developed  from  a 
single  centre  of  ossification. 

Differential  Characters  in  the  Pterygoid  Bone  of  other  Animals. 

A.  Ox,  Sheep,  Goat. — The  pterygoid  of  the  Ox,  Sheep,  and  Goat  is  very  wide,  and  closes 
an  aperture  left  between  the  s|ihenoid  and  palatine  bones. 

B.  Camel. — In  the  Camel  the  pterygoid  is  short,  broad,  and  applied  to  the  internal  face 
of  the  subsphenoidal  process  and  palatine  crest.  It  does  not  concur  in  the  formation  of  the 
Vidian  canal.     Its  inferior  extremity  has  a  narrow  and  deep  fissure. 

C.  Pig. — (See  the  description  of  the  palatine  bone.) 

D.  Camivora. — This  bone  is  very  strong  in  Carnivora,  and  quadrilateral  in  shape. 

5.  Malar  or  Zygomatic  Bone  (Figs.  26,  34). 

This  bone,  also  -designated  the  juf/al  bone,  is  elongated  from  above 
to  below,  flattened  on  both  sides,  and  irregularly  triangular  in  shape  ;  it  is 
situated  on  the  side  of  the  face,  and  articulates  with  the  supermaxillary, 
lachrymal,  and  temporal  bones.  It  is  described  as  having  tivo  faces,  two  borders^ 
a  base,  and  a  summit. 

Faces. — The  external  face  comprises  two  portions  separated  from  each  other 
by  a  semicircular  ridge  that  extends  from  the  summit  to  the  middle  of  the 
anterior  border  of  the  bone,  and  concurs  to  form  the  outer  margin  of  the  orbit. 
The  anterior  portion,  smooth  and  concave,  belongs  to  the  orbital  cavity.  The 
posterior,  more  extensive,  is  also  smooth  and  slightly  convex.  The  internal  face 
is  excavated  in  its  central  part,  which  corresponds  to  the  maxillary  sinus.  On 
its  margin  it  shows  denticulations  and  lamellae  for  articulation  with  the  super- 
maxillary bone. 

Borders. — The  cmterior,  thin  and  denticulated,  is  joined  to  the  lachrymal 
bone.  The  posterior,  or  masseteric  border,  is  thicker,  and  constitutes  a  roughened 
crest,  the  zygomatic  ridge,  which  is  continued  above  with  the  posterior  border  of 
the  process  of  the  same  name,  and  below  with  the  maxillary  spine. 

Base  and  summit. — The  base,  very  thin,  is  united  to  the  supermaxillary  bone. 
The  summit,  flattened  from  before  to  behind  and  bevelled  on  its  anterior  face, 
joins  the  zygomatic  process,  and  forms  with  it  the  j'l/gal  bridge,  or  zygomatic  arch. 

SU-ucture  and  development. — This  bone  is  rather  spongy  in  its  upper  part,  and 
is  developed  from  a  single  nucleus  of  ossification. 

Differential  Characters  in  the  Malar  Bone  op  other  Animals. 
A.  Ox,  Sheep,  Goat. — The  malar  bone  of  Kuminants  is  very  developed.     The  zygomatic 
crest  is  no  longer  formed  by  the  posterior  border  of  the  bone,  but  is  carried  to  the  posterior 
part  of  the  external  face,  and  runs  parallel  with  the  eyebrow.     The  summit  is  bifurcated,  the 

'  This  bone  is  the  representative  of  the  internal  wing  of  the  pterygoid  process  in  Man. 


70  THE  BONES. 

anterior  branch  forming  a  buttress  against  tlie  summit  of  tbe  orbital  process  of  the  frontal 
bone,  while  the  posterior  articulates  with  the  temporal.  In  these  animals,  the  bone  offers 
several  centres  of  ossification. 

B.  Camel. — This  bone  is  very  little  developed,  aud  is  compressed  from  before  to  behind^ 
Its  anterior  face  is  very  concave,  and  circumscribes  the  orbit  posteriorly.  Its  posterior  face 
considerably  overhangs  the  maxillary  bone,  and  forms  a  very  salient  zygomatic  crest.  The 
summit  is  bifurcated,  as  in  the  Ox. 

C.  Pig. — The  summit  of  this  bone  in  the  Pig  is  flattened  on  each  side,  and  divided  inta 
two  brandies,  between  which  is  wedged  the  summit  of  the  zygomatic  process ;  the  anterior 
branch  is  very  sliort,  and  does  not  join  the  frontal  bone. 

D.  Camivora.— The  malar  of  the  Dog  and  Cat  only  articulates  with  the  supermaxillary 
bone,  and  by  its  base  alone.  The  crest  describes  a  curve,  the  concavity  backwards,  and  the 
summit  comports  itself  as  in  the  Pig. 

F.  Rabbit. — The  bone  is  flattened  on  both  sides  ;  the  summit,  united  with  the  zygomatic 
process  of  the  temporal  bune,  is  single ;  while  the  base  is  confounded  entirely  with  the  malar 
tuberosity  (Fig.  36). 

6.  Lachrymal  Bone  (Figs.  26,  51). 

A  small,  thin,  and  very  light  bone,  bent  on  itself  at  a  right  angle,  it  is 
situated  beneath  the  orbit,  which  it  aids  in  forming,  and  is  wedged  between  the 
frontal,  nasal,  snpermaxillary,  and  malar  bones.  It  is  studied  on  its  external 
and  internal  faces  and  circumference. 

Faces. — The  external  is  divided  into  two  regions,  superior  and  inferior,  by 
a  curved  crest  which  forms  part  of  the  orbital  margin,  and  is  provided  with 
notches,  which  are  variable  in  their  form  and  number.  The  superior  region, 
named  the  orbital,  because  of  its  situation  in  the  orbit,  is  slightly  concave  and 
smooth.  It  presents,  near  the  orbital  margin,  the  orifice  of  the  laclirynud  diict, 
which  traverses  the  maxillary  sinus  and  opens  on  the  internal  face  of  the  super- 
maxillary  bone,  where  it  is  continued  by  a  fissure  ;  behind  this  is  the  lachrymal 
fossa.  The  inferior  ov  facial  region  is  slightly  bulging,  and  provided  sometimes 
with  a  tubercle  for  insertion, — the  lackrymal  tubercle.  The  internal  face  is 
employed,  for  the  whole  of  its  extent,  in  the  formation  of  the  walls  of  the 
maxillary  and  frontal  sinuses  ;  it  exhibits  a  cylindrical  prominence  produced  by 
the  bony  tube  of  the  lachrymal  duct. 

Circumference. — This  is  very  irregular,  and  denticulated  for  articulation  with 
the  neighbouring  bones. 

Structure  and  development. — This  bone  is  entirely  compact,  and  is  developed 
from  a  single  nucleus  of  ossification. 

In  the  Ass,  the  lachrymal  tubercle  is  placed  towards  the  anterior  border  of 
the  bone  ;  usually,  it  partly  belongs  to  the  nasal  bone,  and  is  consequently  found 
on  the  suture  uniting  the  lachrymal  bone  to  the  proper  bones  of  the  nose. 

Differential  Chakactebs  in  the  Lachrymal  Bone  of  other  Animals. 

A.  Ox,  Sheep,  Goat.— The  lachrymal  bone,  much  more  extensive  than  that  of  tlie 
Horse,  forms  in  tlie  bottom  of  the  orbit  an  enormous  protuberance,  hollowed  internally  by  the 
maxillary  sinus,  and  the  walls  of  whicii  are  so  thin  and  fragile  that  the  slightest  jar  is  sufficient 
to  cause  their  fracture  (in  the  skeleton).  It  would  be  convenient  to  designate  it  the  lachrymal 
protuberance.^  In  the  smaller  Kuminants,  the  inferior  region  of  the  internal  face  shows  a 
depression — the  lachrymal  fossa. 

B.  Camel.— This  bone  is  much  smaller  than  in  the  Horse ;  its  facial  portion  especially  Is 
almost  rndimi  ntary.  There  is  no  lachrymal  protuberance  nor  tubercle,  the  latter  being  carried 
to  the  superior  maxilla. 

C.  Pig.— In  the  Pig  there  are  observed  a  lachrymal  fossa  and  two  lachrymal  canals,  which 

'  Girard,  who  named  this  eminence  the  orbital  protuberance,  wrongly  described  it  as; 
belonging  to  the  supermaxillary  bone. 


THE  HEAD.  71 

are  pierced  outside  the  orbital  cavity,  and  soon  coalesce  in  the  substance  of  the  bone  to 
constitute  a  single  canal.     The  fossa  is  very  deep. 

D.  Camivora. — This  bone  in  Carnivora  is  extremely  small.  Its  external  face  entirely 
belongs  to  the  orbit,  and  does  not  descend  beneath  the  margin  of  tliat  cavity;  it  has  no 
lachrymal  fossa.  The  reduced  dimensions  it  presents  in  these  animals  well  justifies  the  name, 
OS  unguis,  given  to  it  in  anthropotomy. 

7.  Nasal  Bones  (Fig.  26). 

Situated  on  the  anterior  aspect  of  the  head,  these  bones  articulate  with  each 
other  in  the  median  hne,  and  are  fixed  between  the  frontal,  lachrymal,  and  super- 
maxillary  bones  ;  they  are  triangular  in  shape,  elongated  from  above  to  below, 
flattened  from  before  to  behind,  and  offer  for  study  two  faces,  two  borders,  a  base, 
and  a  summit. 

Faces. — The  external  or  anterior  face,  wider  above  than  below,  is  convex  from 
side  to  side,  and  almost  smooth.  The  posterior,  internal,  or  nasal  face  exhibits  a 
vertical  crest  passing  along  the  external  border  of  the  bone,  which  gives  attach- 
ment to  the  turbinated  portion  of  the  ethmoid  ;  at  its  superior  extremity  this 
crest  bifurcates,  and  between  its  two  branches  shows  a  concave  surface  which 
forms  part  of  the  frontal  sinus.  For  the  remainder  of  its  extent  the  internal 
face  is  smooth,  and'  covered  by  the  mucous  membrane  of  the  nasal  fossa ;  it 
is  also  excavated  into  a  channel  to  form  the  superior  meatus  of  this  cavity. 

Borders. — The  extermd  border  is  very  thin  in  its  upper  two-thirds,  and  articu- 
lates with  the  lachrymal  bone,  the  anterior  border  of  the  supermaxillary,  and  the 
extremity  of  the  external  process  of  the  premaxilla.  In  its  lower  third  it  becomes 
isolated  from  the  latter  bone,  in  forming  with  the  anterior  border  of  its  large  pro- 
cess a  very  acute  re-entering  angle,  the  opening  of  which  looks  downwards.  The 
interned  border  is  denticulated  for  contact  with  the  opposite  bone. 

Base  and  Summit. — The  base  occupies  the  superior  extremity  of  the  bone  ; 
it  describes  a  curved  line  with  the  convexity  above,  and,  in  uniting  on  the  median 
line  with  that  of  the  opposite  bone,  forms  a  notch  similar  to  that  of  the  heart 
figured  on  playing-cards  ;  it  is  bevelled,  at  the  expense  of  the  internal  plate,  to 
articulate  with  the  frontal  bone.  The  summit  of  the  two  nasal  bones,  which  is 
pointed,  constitutes  the  nasal  prolongation — the  name  given  to  a  single  triangular 
process  which  comprises  all  that  portion  of  the  nasal  bones  separated  from  the 
premaxillaries  by  the  re-entering  angle  before  mentioned. 

Structure  and  development. — Almost  entirely  compact  in  structure,  it  is 
developed  from  a  single  centre. 

Differential  Characters  in  the  Nasal  Bones  of  other  Animals. 

A.  Ox,  Sheep,  Goat. — The  nasal  bones  of  the  Ox  are  never  consolidated  with  each  other, 
nor  yet  with  the  neighbouring  bones.  The  external  border  only  comes  in  contact  to  a  small 
extent  with  the  supermaxillary  bone ;  the  superior  extremity  is  fixed  in  the  notch  of  the  inferior 
border  of  the  frontal  bone.  At  their  inferior  extremity,  they  each  present  a  notch  which  divides 
them  into  two  points. 

In  the  Sheep  and  Goat  the  nasal  spine  is  unifid,  as  in  the  Horse  (see  Figs.  30,  32). 

B.  Camel. — In  the  Camel,  the  proper  bones  of  the  nose  are  short  and  narrow;  their 
external  border  is  in  contact  only  with  the  superior  maxilla;  the  upper  extremity  is  rounded. 
At  the  inferior  extremity,  they  show  a  well-marked  notch,  which  divides  them  into  two  points, 
but  the  inner  point  is  very  small. 

C.  Pig. — Tliese  bnnes  are  long  and  narrow,  and  traversed  on  their  external  face  by  the 
fissure  that  descends  from  the  supra-orbital  foramen.     The  nasal  prolongation  is  short. 

D  Carnivora.— The  two  bones  of  the  nose  are  little  developed,  and  are  wider  below  than 
above ;  they  have  no  nasal  prolongation,  but  offer,  instead,  a  semicircular  notch. 


THE  BONES. 


E  Rabbit.— Proportionately  long  and  wide,  the  nasal  bone  of  the  Rabbit  articulates,  by 
the  whole  of  its  external  border,  with  the  ascending  process  of  the  preuiaxillary  bone.  The 
anterior  extremity  of  the  nasal  bone  is  very  slightly  salient. 


Fig.  41. 


Fig.  42. 


LONGITUDINAL  AND  TRANSVERSE  SECTION  OP 
THE  horse's  head,  SHOWING  THE  FLOOR  OF 
THE  CRANIAL  AND  NASAL  CAVITIES,  WITH 
THE    MAXILLARY    SINUSES. 

1,  Condvloid  foramen.  2,  Section  of  the  parieto 
tem[ioval  canal.  3,  Foramen  lacerum  basis 
cranii.  4,  Carotid  notch.  4',  Maxillary 
notch:  o,supermaxillary  fissure  ;  6,  cavern- 
ous fissure.  5,  Origin  of  the  supra-sphe- 
noidal  canals  :  c,  sella  Turcica.  6,  Optic 
fossa.     7,  Portion  of  the  crista-galli  process. 

8,  Cribriform  plate  of   the  ethmoid    bone. 

9,  Perpendicular    plate   of  the   s^ame  bone. 

10,  10,  Its  lateral  masses.  11,  Interior  of 
the  great  ethmoidal  cell.  12,  12,  Bottom  of 
the  maxillary  sinuses  communicating  with 
the  sphenoidal  sinuses.  13,  Superior 
maxillary  sinus.  14, Inferior  maxillary  sinus. 
14',  Superior  compartment  of  the  maxillary 
turbinated  bone,  forming  part  of  the  latter 
sinus.  15,  Section  of  ttie  supermaxillo- 
dental  cannl.  16,  Channel  of  the  vomer. 
17,  Internal  proc.'ss,  or  point  of  the  pre- 
maxillary  bone. 


ANTERO-POSTERIOR  AND  VERTICAL 
SECTION  OF  THE  HORSE'S  HEAD. 

1,  Condyloid  foramen  ;  2,  parietal 
protuberance  ;  3,  internal  audi- 
tory hiatus  ;  4,  cerebral  cavity  ; 
5,  cerebellar  cavity;  6,  supe- 
rior border  of  the  perpendicular 
plate  of  theethmoidbone(crista- 
galli  process) ;  7,  ethmoidal 
volutes — nasal  face;  8,  vestiges 
of  the  right  frontal  sinus;  9, 
ditto  of  the  sphenoidal  sinus  ; 
10,  pterygoid  process;  11,  eth- 
moidal turbinated  bone;  12, 
maxillary  turbinated  bone  ;  13, 
crest  of  the  supermaxillary 
bone  to  which  the  latter  is 
fixed  ;  14,  vomer.  A,  Orifice  of 
communication  between  the 
nasal  cavity  and  the  sinus. 


THE  BEAD.  73 


TUEBINATED   BONES   (Fig.  42). 


The  turlinated  (or  turUnal)  hones,  two  on  each  side,  represent  two  irregular 
bony  columns,  wider  above  than  below,  compressed  laterally,  hollowed  internally, 
and  lying  vertically  side  by  side  on  the  external  wall  of  the  nasal  fossa,  which 
they  divide  into  three  meatuses  or  passages. 

They  are  distinguished  into  anterior  and  posterior  turbinated  hones. 

The  anterior  or  superior,  also  named  the  ethmoidal,  is  formed  by  a  very  thin 
plate  of  compact  tissue— fragile  and  like  papyrus,  fixed  by  its  anterior  border  to 
the  internal  crest  of  the  nasal  bone,  and  rolled  on  itself,  from  before  to  behind, 
in  the  same  manner  as  the  cells  of  the  ethmoid  bone.  Above,  it  is  confounded 
with  the  last-named  bone,  of  which  it  is  only,  properly  speaking,  the  most  anterior 
volute.  At  its  inferior  extremity,  it  is  prolonged  by  a  fibro-cartilaginous  frame- 
work to  the  external  orifice  of  the  nose. 

Its  internal  cavity  is  partitioned  by  a  transverse  plate  into  two  portions  :  the 
superior  compartment  forms  part  of  the  frontal  sinus  ;  the  inferior  is  subdivided 
by  other  small  lamellEe  into  a  variable  number  of  cells  which  communicate  with 
the  nasal  cavity.  This  bone,  developed  from  a  single  nucleus,  is  ossified  at  the 
same  time,  and  in  the  same  manner,  as  the  ethmoidal  cells.  Before  birth,  it  is 
already  intimately  consolidated  with  the  nasal  bone. 

The  posterior,  inferior,  or  maxiUary  turbinated  hone  resembles  the  first,  except 
in  some  particulars.  Thus,  its  bony  or  proper  portion  is  not  so  long  or  volu- 
minous, while  its  cartilaginous  part  is,  on  the  contrary,  more  developed.  It  is 
attached,  by  its  posterior  border,  to  the  vertical  and  sinuous  crest  of  the  super- 
maxillary  bone,  and  is  rolled  from  behind  to  before,  or  in  an  inverse  direction  to 
the  other.  It  has  no  connection  with  the  ethmoid,  and  its  superior  cavity  forms 
part  of  the  inferior  maxillary  sinus.  It  is  late  in  becoming  ossified,  and  is 
scarcely  united  in  a  definite  manner  to  the  maxillary  bone  until  the  horse  is 
about  a  year  old. 

The  meatuses  are  distinguished  into  anterior  or  superior,  middle,  and  posterior 
or  inferior.  The  first  passes  along  the  front  of  the  ethmoidal  turbinated  bone  ; 
the  second  separates  the  two  turbinated  bones,  and  presents,  near  its  superior 
extremity,  the  opening  communicating  between  the  sinuses  and  the  nasal  cavities.^ 
The  third  is  situated  behind  the  maxillary  turbinated  bone,  and  is  confounded 
with  the  floor  of  the  nasal  fossa. 

The  turbinated  bones  are  essentially  disposed  to  furnish  the  membrane  of  the 
nose  with  a  vast  surface  of  development.  This  membrane,  indeed,  covers  their 
entire  superficies,  and  even  penetrates  the  anfractuous  cells  of  their  lower 
compartment. 

Differential  Characters  in  the  Turbinated  Bones  of  other  Animals. 

A.  Ox,  Sheep,  Goat. — In  the  Ox  (Fig.  43),  the  ethmoitlal  turbinated  bone  is  very  small, 
and  is  united  to  the  nasal  bone  bv  the  two  borders  of  its  osseous  plate ;  its  internal  cavity  entirely 
belongs  to  the  frontal  sinus.  The  maxillary  turbinated  bone  is  very  developed,  and  is  joined 
to  the  bone  which  sustains  it  at  a  later  period  than  in  the  Horse.  The  bony  lamina  of  which 
it  is  composed,  is  curved  on  itself  in  two  different  directions — from  before  to  behind  by  its 
posterior  border,  and  behind  to  before  by  its  anterior  border.  It  is  fixed  to  the  supermaxillary 
bone  by  its  middle  part,  through  the  medium  of  a  particular  bony  lamina,  and  it  very  incom- 

'  The  two  turbinated  bones,  in  being  applied  against  the  excavation  on  the  inner  face  of  the 
supermaxillary,  almost  entirely  close  it,  only  leaving  between  them  a  vertical  slit  which  con- 
stitutes the  opening  mentioned  above. 


74 


THE  BONES. 


pletely  closes  the  excavatioh  which  coucurs  to  form  the  maxillary  sinus.    In  the  skeleton  there 
is  also  found  behind,  and  at  the  base  of  this  turbinated  bone,  a  vast  opening  which  is  totally 

closed  in  the  fresh  condition  by  the  pituitary  membrane. 
The  maxillary  sinus  is  not  prolonged  in  its  interior. 
In  the  smaller  Euminants,  tlie  cavity  of  the  sinus  is 
closed  by  the  maxillary  turbinated  bone  in  a  more 
complete  manner  than  in  the  Ox. 

B.  Camel. — The  ethmoidal  turbinated  bone  is 
very  small.    Otherwise  it  is  as  in  the  other  Ruminants. 

C.  Pig. — The  same  arrangement  as  in  tlie  Sheep 
and  Goat,  except  that  the  bones  are  mucli  longer  and 
less  fragile. 

D.  Carnivora.— These  bones  in  tlie  Dog  and  Cat 
are  particularly  distinguished  for  their  numerous  cou- 
volutions.  Neither  participate  in  the  formation  of 
the  frontal  or  maxillary  sinuses;  the  latter  is  not  in 
any  way  closed  by  the  maxillary  turbinated  bone,  but 
opens  into  the  nasal  cavity  by  a  large  gaping  aperture. 

E.  Rabbit. — The  bones  are  arranged  as  in  the 
Dog,  but  the  folds  are  less  numerous. 


9.  VoMEE  (Figs.  34,  38). 

This,  a  single  bone,  elongated  from  above 
to  below,  flattened  on  both  sides,  and  extending 
on  the  median  line  from  the  body  of  the 
sphenoid  to  the  premaxillary  bone,  offers  for 
study  two  lateral  faces,  two  borders,  and  two 
extremities. 

The  faces  are  smooth,  plane,  and  covered 
by  the  nasal  membrane.  The  anterior  border 
is  channeled  for  the  whole  of  its  length  by  a 
deep  groove,  which  receives  the  posterior  border 
of  the  cartilaginous  septum  of  the  nose.  The 
posterior  border  is  sharp  and  smooth  in  its 
upper  half,  which  separates  the  two  guttural 
openings  of  the  nasal  cavities  :  it  is  thick  and 
slightly  denticulated  for  the  remainder  of  its 
extent,  and  rests  on  the  median  suture  resulting 
from  the  union  of  the  two  supermaxillary 
bones.  The  superior  extremity  is  provided,  in 
its  middle,  with  a  notch  which  divides  it  into 
two  lateral  prolongations  shaped  like  a  cat's 
ears  {wings  of  the  vomer) ;  it  articulates  with 
the  inferior  sphenoid,  ethmoid,  palatine,  and 
pterygoid  bones.  The  inferior  extremity  rests 
on  the  prolongations  of  the  premaxillae. 

This  bone  is  entirely  compact,  and  is 
developed  from  one  centre  of  ossification. 


MEDIAN    AND   VERTICAL    SECTION   OF 
THE   ox's    HEAD. 

X,  Condyloid  foramen;  1',  posterior  ori- 
fice of  the  occipital  lateral  canal 
joining  the  parieto-temporal  canal 
in  front ;  2,  internal  auditory  hiatus  ; 
3,  anterior  foramen  lacerum ;  4,  pos- 
terior ditto  ;  5,  iutra-cranial  orifice 
of  the  parieto-temporal  canal  ;  6,  6, 
median  bony  plate  separating  the 
frontal  sinuses  ;  7,  lamina  which  iso- 
lates the  sphenoidal  sinus;  8,  lamina 
partitioning  the  palatine  portion  of 
the  maxilliary  sinuses  ;  9,  oval  fora- 
men;  10,  optic  fossa;  11,  vomer; 
12,  pterygoid  bone  ;  1.3,  large  open- 
ing leading  into  the  maxillary  sinus, 
and  which,  in  the  fresh  state,  is  closed 
by  the  pituitary  membrane  ;  14,  max- 
illary turbinated  bone;  15,  ethmoidal 
turbinated  bone;  16,  great  ethmoidal 
cell. 


Differential  Characteks  in  the  Vomer  of 

OTHER  Animals. 
A.  Ox,  Sheep,  Goat. — This  is  a  very  wide  and 
thin  bone,  resting  only  on  the  lower  half  of  the  median 
suture  of  the  premaxillaries  (Fig.  43). 
B.  Camel.— Wider  in  its  upper  part  than  in  the  Ox,  the  vomer  reaches,  outwardly,  the 


THE  HEAD.  75 

orbital  cavity.     By  its  inferior  border,  it  rests  on  the  entire  length  of  the  median  suture  of  the 
palatine  and  superraaxillary  bones. 

C.  Pig. — The  vomer  in  this  animal  adheres  to  the  bones  of  the  palatine  arch  for  a  great 
extent.     The  free  portion  of  the  inferior  border  is  short  and  but  little  prominent. 

D.  Camivora.— In  the  Dog  and  Cat,  the  vomer  is  short,  but  its  wings  are  very  large. 

10.  Inferior  Maxillary  Bone  (Fig.  44). 

The  inferior  maxillary  hone  is  not  consolidated  with  any  of  the  preceding  bones, 
and  is  only  united  to  two  of  them — the  temporals — by  diarthrodial  articulation. 
It  is  a  considerable  bone,  situated  behind  the  upper  jaw,  and  composed  of  two 
symmetrical  branches,  which  are  flattened  on  both  sides,  wider  above  than  below, 
curved  forwards  in  their  upper  third,  joined  at  their  lower  extremities,  and 
separated  superiorly  so  as  to  leave  a  wide  gap  between  them,  like  the  letter  V  in 
shape,  called  the  intra-maxillary  space.  Each  offers  for  study  tivo  faces,  two 
borders,  and  two  extremities. 

Faces. — The  external  face  of  the  maxillary  branches  is  smooth  and  rounded  in 
its  inferior  two-thirds,  and  transformed  superiorly  into  a  rugged  surface,  in  which 
is  implanted  the  fibres  of  the  masseter  muscle.  The  internal  face  presents,  in  the 
corresponding  point,  an  excavated  surface  on  which  is  remarked  the  superior 
orifice  of  the  maxillo-dental  caned,  a  long  channel  which  descends  between  the 
two  plates  of  the  branch,  passing  under  the  roots  of  the  molar  teeth,  and  insensibly 
disappearing  in  the  body  of  the  bone  after  being  widely  opened  externally  by  the 
mental  {ov  anterior  maxillary)  foramen.  In  its  inferior  two-thirds,  the  internal 
face  is  smooth,  nearly  plane,  and  shows  nothing  very  remarkable.  Near  the 
alveolar  border  there  is  a  slightly  projecting  line — the  myloid  ridge ;  and  quite 
below,  or  rather  at  the  very  summit  of  the  re-entering  angle  formed  by  the 
separation  of  the  branches,  there  is  a  slight  rugged  excavation  confounded  with 
that  of  the  opposite  branch,  and  named  the  ye)iicd  surface. 

Borders. — The  anterior,  also  named  the  alveolar  border,  exhibits  for  study  a 
straight  or  inferior,  and  a  curved  or  superior  portion.  The  first  is  hollowed  by 
six  alveoU  to  receive  the  inferior  molar  teeth. 

The  second,  thinner,  concave,  and  rugged,  serves  for  muscular  insertion. 
The  posterior  border  is  also  divided  into  straight  and  curved  portions.  The  latter 
is  convex,  thick,  rugged,  and  margined  on  each  side  by  an  uneven  lip  ;  the  first 
is  regularly  rectilinear,  so  that  all  its  points  rest  at  the  same  time  on  a  horizontal 
plane  ;  it  is  thick  and  rounded  in  the  young  animal,  but  becomes  sharp  with 
age  ;  an  oblique  and  transverse  fissure — the  maxillary — separates  it  from  the 
curved  part.     The  union  of  these  two  portions  forms  the  angle  of  the  jaw. 

Extremities. — The  superior  e.vtremity  has  two  eminences  :  a  condyle,  and  a 
long  non-articular  process  named  the  coronoid  process.  The  condyle  is  elongated 
transversely,  and  convex  in  its  two  diameters  ;  it  responds,  through  the  medium 
of  a  fibro-cartilaginous  disc,  to  the  articular  surface  of  the  zygomatic  process. 
■  The  coronoid  process  is  situated  in  front  of  the  condyle,  from  which  it  is  sepa- 
rated by  a  division  called  the  sigmoid  or  corono-condyloid  notch ;  it  is  flattened  on 
both  sides,  and  curved  backwards  and  slightly  inwards. 

From  the  union  of  the  branches  of  the  maxillary  bone  at  their  inferior 
extremity,  results  a  single  piece,  flattened  before  and  behind,  and  widened  like  a 
spatula,  which  has  been  designated  the  body  of  the  bone.  This  merits  a  special 
description. 

Its  form  allows  us  to  divide  it  into  an  anterior  or  buccal  face,  a  posterior  or 


76 


THE  BONES. 


labial  face,  and  a  circumference.  The  anterior  face  is  smooth  and  concave,  is  lined 
by  the  buccal  mucous  membrane,  and  supports  the  free  extremity  of  the  tongue. 
The  posterior  face  is  convex,  more  extensive  than  the  preceding,  and  continuous 
with  the  external  face  of  the  branches.  It  presents  :  1.  On  the  median  line,  a 
slight  crest  or  small  groove— traces  of  its  being  originally  separated  into  two 
pieces.  2.  On  the  sides  and  above,  the  mental  foramen — the  inferior  orifice  of  the 
maxillo-dental  canal.  On  a  level  with  this  foramen,  the  bone  very  markedly 
contracts  to  form  the  neck.  The  circumference  describes  a  parabolic  curve,  the 
concavity  being  uppermost,  and  joins,  by  its  extremities,  the  anterior  border 
of  each  branch.  It  is  excavated  in  its  middle  part  by  the  six  alveoli  for  the 
lodgment  of  the  inferior  incisors,  and  behind  these— in  male  animals  only— there 
is  an  additional  alveolus  for  the  tusk.     The  portion  included  on  each  side 


Fig.  44. 


INFERIOR   MAXILLA. 

1,  Mental  foramen;  1',  superior  orifice  of  the  maxillo-dental  canal ;  2,  surface  of  implantation  for 
the  masseter  muscle  ;  3,  myloid  ridge  ;  4,  coronoid  process  ;  5,  condyle. 

between  the  last  incisor  and  first  molar,  forms  a  more  or  less  sharp  ridge,  which 
constitutes  the  inferior  interdental  space  or  bar  {diastema). 

Structure  and  development. — Formed,  like  all  the  flat  bones,  by  two  compact 
plates  separated  by  spongy  tissue,  the  inferior  maxilla  is  developed  from  two 
centres  of  ossification,  which  correspond  to  each  branch,  and  which  coalesce  some 
time  after  birth. 

But  in  the  human  foetus,  there  can  oe  seen  five  pieces  developed  around  the 
dental  canal — the  coronary,  articular,  angular,  opercular,  and  premaxillary — 
which  proves  that  the  maxilla  of  Mammalia  is  formed  on  the  same  type  as  that 
of  oviparous  Vertebrata  (Lavocat). 


DiFFEKENTIAL    CHARACTERS   IN    THE    INFERIOR    MaXILLA    OP   OTHER    ANIMALS. 

A.  Ox,  Sheep,  Goat.— In  these  animals,  the  part  of  the  posterior  border  of  the  inferior 
maxilla  below  the  molars  is  convex,  and  cannot  rest  on  a  horizontal  plane  by  all  its  points  at 
the  same  time.  The  condyle  is  convex  in  its  small  diameter,  and  slightly  concave  laterally  The 
coronoid  process  is  bent  backwards  and  outwards.  The  body  does  not  show  any  alveolus  for 
the  tusk,  because  this  tooth  is  not  present  in  these  animals ;  but  it  is  hollowed  by  eight  alveoli 
for  the  incisor  teeth.  The  two  branches  of  the  bone  are  never  consolidated,  but  remain 
movable  on  each  other  during  life. 


THE  HEAD. 


77 


B.  Camel. — The  branches  are  short  and  thick,  the  body  very  long,  and  the  interdental 
space  considerable.  The  straight  border  of  tlie  branches  has  a  posterior  rectilinear  border,  aa 
in  the  Horse ;  the  anterior  margin  of  the  curved  portion  is  tliin  and  sharp.  Oa  its  internal 
face  is  seen  a  plate  in  front  of  the  superior  opening  of  the  inferior  dental  foramen,  and  a  mylo- 
hyoid fissure. 

The  condyle  is  convex  in  front,  flat  and  oblique  behind.  The  coronoid  process  is  very 
strong.     Below  the  condyle  is  a  process  separated  from  the  latter  by  a  deep  notch. 

The  circumference  of  the  body  is  excavated  by  eight  alveoli — six  for  the  incisors,  and  two 
for  the  canines. 

C.  Pig. — A  straight  line  leading  from  the  greater  axis  of  the  alveoli  of  the  molar  would 

Fig.  45. 


HEAD   OF    THE    CAMEL. 

1,  Occipital  bone ;  2',  parietal  crest ;  3,  .squamous  temporal ;  4,  frontal  bone ;  4',  supra-orbital 
foramen;  5,  malar  bone;  6,  nasal  bones;  7,  supermaxillary  bone;  7',  infra-orbital  foramen; 
8,  premaxillary  bone;  9,  inferior  maxilla;  10,  11,  openings  of  the  inferior  dental  foramen. 


not  traverse  the  posterior  border  of  the  maxillary  branches ,  the  bottom  of  these  alveoli  corre- 
sponds to  the  relief  on  the  iimer  face.  The  condyle  is  compressed  on  both  sides,  and  elongated 
from  before  to  behind;  while  the  coronoid  process  is  short  and  wide.  TIjere  is  no  neck;  the 
interdental  spaces  are  very  short ;  and  the  maxillo-dental  canal  opens  inferiorly  by  multiple 
orifices. 

D.  Carnivora.— In  Carnivore,  this  is  hollowed  at  the  point  corresponding  to  the  insertion 
of  the  masseter  muscle  into  a  somewhat  deep  fossa.  The  posterior  border  is  disposed  as  in 
Ruminants,  and  below  the  condyle  lias  a  very  marked  tuberosity.  The  condyle  represents  an 
ovoid  segment,  and  fits  exactly  into  the  temporal  cavity.  The  coronoid  process  is  very  strong, 
elevated,  and  wide.  The  mental  foramina  are  double  or  treble.  There  are  no  interdental 
spaces,  nor  excavated  surface  on  the  inner  face  of  tlie  branches ;  and  the  latter  are  never 
consolidated. 

E.  Rabbit. — In  the  maxilla  of  the  Rabbit,  the  coronoid  process  is  very  short,  and  the 
condyle  narrow  and  elongated  from  before  to  behind.     The  posterior  border  is  deeply  notched 

8 


78 


THE  BONES. 


HEAD   OF    THE    CAT. 

Parieto-occipital  suture;  2,  parietal  bone; 
3,  frontal  bone ;  4,  orbital  piocess  of  the 
frontal  bone;  5,  malar  bone;  6,  supermaxil- 
lary  bone  ;  7,  7,  premaxilla  ;  8,  nasal  bone ; 
9,  tympanic  bulb  ;  10,  inferior  maxilla. 


in  its  curved  portion ;  the  interdental  space  is  very  long ;  and  the  body  has  only  two  alveoli 
for  the  incisors. 

11.— The  Hyoid  Bone  (Fig.  47). 

The  hi/oid  bone  constitutes  a  small  and  special  bony  apparatus  which  serves 

to  support  the  tongue,  as  well  as  the 
Fig-  -iS.  larynx  and  pharynx  ;  its  description  is 

placed  immediately  after  that  of  the 
bones  of  the  head  because  of  its  con- 
nection with  that  region,  it  being  situ- 
ated between  the  two  branches  of  the 
supermaxillarybone,  and  suspended  from 
the  base  of  the  cranium  in  an  oblique 
direction  from  above  to  below,  and  from 
before  to  behind. 

This  apparatus  is  composed  of  seven 
distinct  pieces,  arranged  in  three  series  : 
a  middle,  constituted  by  a  single  bone, 
and  named  the  body ;  two  lateral,  form- 
ing two  quasi-parallel  branches,  to  the 
extremities  of  which  the  body  is  articu- 
lated. 

Body  or  basihijal. — The  body  of  the 
hyoid  resembles  a  fork  with  two  prongs.  It  presents  :  1.  A  middle  part  flattened 
above  and  below,  and  consequently  provided  with  a  superior  and  an  inferior  face. 

2.  A  single  and  long  pro- 
p's- '*^'  longation  flattened  on 
both  sides,  which  is  de- 
tached from  the  middle 
part,  and  directed  forward 
and  downward  to  plunge 
into  the  muscular  tissue 
of  the  tongue  :  this  is  the 
anterior  appendix  of  the 
hijoideaJ  body,  or  Ungual 
prolongation.  3.  Two  late- 
ral cornua,  thyroid  cornua, 
great  cornua,  or  urohyals, 
projecting  backwards  and 
upwards,  articulating  by 
their  extremities  with  the 
thyroid  cartilage  of  the 
larynx,  and  offering,  at 
their  point  of  union  with 
the  middle  part,  two  con- 
vex diarthrodial  facets 
looking  upwards,  and 
corresponding  with  the  styloid  cormia.  The  body  of  the  hyoid  bone  is  developed 
by  three  centres  of  ossification — a  middle,  and  two  lateral  for  the  cornua. 

Branches. — The  three  pieces  composing  these  are  articulated  end  to  end,  by 


HYOID   BONE   OF   THE    HORSE. 

Body  or  ba^ihyal ;  2,  lingual  prolongation ;  3.  3,  thyi'oid 
cornua,  great  cornua,  or  urohyals ;  4,  4,  styloid  cornua. 
small  cornua.  or  apohyals ;  5,  5,  styloid  nuclei  or  ceratohyals ; 
6,  6,  styloids,  great  hyoideal  branches,  or  stylohyais  ;  7,  7, 
arthrohyals.  or  cartilaginous  nuclei  attaching  the  hyoid  to 
the  temporal  bone. 


THE  HEAD.  79 

means  of  a  cartilaginous  substance  that  joins  them  together  ;  they  are  of  very 
unequal  dimensions.  The  first,  which  is  in  relation  with  the  body,  is  of  medium 
size,  and  is  named  the  styloid  cormi,  small  conm,  or  small  branch.  The  second, 
termed  the  styloid  nucleus,  is  the  smallest.  The  third,  the  largest,  constitutes 
the  styloid  process  or  bo7ie,  or  great  branch. 

1.  The  styloid  cornua  {cfpohyaV)  is  a  small  cylindrical  piece  bearing  a  concave 
diarthrodial  surface  on  its  inferior  extremity  to  unite  it  to  the  body  ;  it  is  very 
spongy,  and  is  developed  from  two  ossifying  centres,  one  of  which,  the  epiphysary, 
is  for  the  inferior  extremity. 

2.  The  styloid  nucleus  {ceratohyal),  which  is  often  absent,  is  embedded  in  the 
uniting  cartilaginous  substance. 

3.  The  styloid  bone,  or  great  hyoideal  branch  {stylohyal),  is  long,  thin,  flattened 
on  both  sides,  and  directed  obliquely  from  above  to  below,  and  before  to  behind  ; 
it  presents  two  faces,  two  borders,  and  two  extremities.  The  faces — an  external 
and  internal — are  marked  by  some  few  imprints.  The  anterior  border  is  sharp 
and  slightly  concave  in  its  upper  third.  The  posterior  border  is  thicker,  and  is 
divided  into  two  portions — a  superior  or  horizontal,  which  is  very  short,  and  an 
inferior  or  vertical,  much  more  extensive.  The  angle  they  form  at  their  point 
of  junction  presents  a  salient,  and  more  or  less  roughened,  tuberosity.  The 
superior  extremity  is  united  to  the  hyoideal  prolongation  of  the  temporal  bone 
by  means  of  a  cylindrical  fibro-cartilage.  By  its  inferior  extremity,  the  styloid 
bone  is  united  either  to  the  styloid  nucleus  or  the  styloid  cornu,  forming  a  sharp 
elbow  directed  forwards.  The  styloid  bone,  developed  from  a  single  centre  of 
ossification,  is  almost  entirely  formed  of  compact  tissue. 

Differential  Characters  of  the  Htoid  Bone  in  other  Animals. 

A.  Ox,  Sheep,  Goat. — The  hyoid  bone  of  Ruminants  is  always  composed  of  seven  piecea. 
the  styloid  nucleus,  the  presence  of  which  is  not  constant  in  Solipeds,  is  never  absent  in  these,' 
and  has  the  proportions  of  the  second  small  branch.  The  anterior  appendix  is  very  short,  and 
only  represents  a  large  mamelon. 

B.  Camel. — The  liyoid  is  in  this  animal  as  in  the  Ox. 

C.  Pig.— The  body  is  voluminous  and  deprived  of  an  appendix;  the  small  branches  are 
short  and  consolidated  with  the  body ;  while  the  large  branches,  curved  like  an  S,  are  very 
thin,  and  are  not  united  to  the  small  branches  and  the  temporal  bone  by  libro-cartilage,  but  by 
veritable  yellow  elastic  ligaments. 

D.  Carnivora.  —  The  three  pieces  composing  the  body  of  the  hyoid  in  early  life  are  never 
consolidated  in  the  adult  animal,  but  always  remain  isolated,  as  in  Man.  The  middle  piece 
has  no  anterior  appendix;  the  fibro-cartilages  uniting  the  styloid  portions  to  each  other  and  to 
the  temporal  bone  are  very  long  and  flexible. 

12.  WoEMiAN  Bones  (Fig.  48). 

This  name  has  been  given  to  small  irregular  bones  which  Worms  observed 
between  some  of  the  sutures  of  the  cranial  bones.  They  are  developed  after 
birth,  in  the  cranial,  cranio-facial,  and  facial  sutures.  Their  number  and  position 
varies  with  the  species  of  animals,  and  even  the  breeds  of  the  same  species. 

Vaguely  described  by  Rigot,  they  have  been  recently  studied  by  Cornevin, 
who  observes  that  the  cranial  Wormian  bones  are  rare.  In  more  than  sixty 
crania,  they  were  found  only  once  or  twice  in  the  Ox  and  Horse  at  the  junction 
of  the  petrous  with  the  occipital  bone.  The  Wormian  bones  of  the  cranio-facial 
and  the  facial  suture  are  more  frequent ;  nevertheless,  they  have  been  met  with 
almost  exclusively  in  the  heads  of  common-bred  animals,  particularly  in  the 
bovine  species.     Cornevin  has  described  a  fontanelle  lachrymo-nasal  bone  (Fig. 


80  THE  BONES. 

48,  2),  and  Wormian  fronto-nasal  (Fig.  48,  1),  as  well  as  an  interaasal,  orbital, 
zygomato-maxillary,  maxillo-nasal-incisive  bone.  (Sometimes  two  Wormian 
bones  are  found  in  the  same  head.) 

OP  THE   HEAD   IN   GENERAL. 


1.  Geneeal  Configueation. 

From  the  union  of  all  the  bones  which  constitute  the  cranium  and  faoe, 
there  results  a  quadrangular  pyramid,  with  summit  inverted,  which  it  is  necessary 

to  study  as  a  whole.    We  will  pass  in 
^'S-  *^"  review,  successively,  its  four  faces,  its 

base,  and  its  summit. 

A.  Anterior  Face.— This  is 
subdivided  into  four  regions  (Fig. 
49)  : 

1.  Parietal  region. — This  has  for 
base  the  anterior  portion  of  the 
occipital  bone  and  the  parietal  bones. 
Limited,  above,  by  the  external  occi- 
pital tuberosity,  it  presents  on  the 
middle  line  a  spur  which  soon  bifur- 
cates to  form  the  parietal  or  temporal 
crests ;  the  latter  join  the  posterior 
border  of  the  zygomatic  process.        i 

2.  Frontal  region. — Larger  than^ 
the  preceding,  it  is  usually  plane  and 
lozenge-shaped.  Boimded  iuferiorly 
by  the  fronto-nasal  suture,  this  region 
projects,  laterally,  the  orbital  pro- 
cesses, the  base  of  which  is  pierced 
by  the  supra-orbital  foramen,  and  the 
anterior  border — somewhat  sharp— 
is  frequently  made  irregular  by  small 

notches,  one  of  which  is  often  converted  into  a  foramen. 

3.  Nasal  region. — This  region  has  for  its  base  the  proper  bones  of  the  nose. 
It  is  narrow,  convex  on  each  side,  and  plane,  concave,  or  convex  in  its  length, 
according  to  the  animals.  It  advances  above  the  entrance  to  the  nasal  cavities, 
where  it  forms  the  nasal  prolofigation,  the  summit  of  which,  in  the  Horse,  ceases 
at  nearly  two  fingers'  breadth  from  the  intermaxillary  symphysis. 

4.  Incisive  region. — Principally  formed  by  the  incisive  bones,  this  region 
presents  :  the  inferior  opening  of  the  nasal  cavities,  divided  in  the  fresh  state  by 
the  median  cartilaginous  septum  of  the  nose ;  the  incisive  slits  on  the  floor  of 
the  nasal  fossfe  ;  the  intermaxillary  symphysis,  channeled  above  by  a  more  or 
less  deep  groove  in  nearly  all  Horses,  but  raised,  on  the  contrary,  into  a  conical 
tubercle  in  the  Ass  and  Hinny,  and  perforated  in  the  middle  by  the  incisive  canal. 
Right  and  left  of  the  intermaxillary  symphysis  this  region  is  convex,  and  elevated 
by  the  prominence  which  the  roots  of  the  incisor  teeth  form. 

B.  Posterior  Pace. — In  this  are  recognized  four  distinct  regions  (Fig.  50)  : 
1.  Sub-occipital  region. — This  presents  :   in  the  middle,  the  basilar  process^ 


WORMIAN    BONES   OF   THE   OX.     (AFTER   CORNEVIN.) 

1,  Fronto-nasal  Wormian  bones;  2,  2,  lachrymo- 
nasal  fontanellar  bones. 


THE  HEAD. 


81 


a  strong  piece  more  or  less  deeply  channeled,  according  to  the  animals,  and 
provided  at  its  inferior  extremity  with  rugosities  for  the  attachment  of  the  anterior 
straight  muscles  of  the  head  ;  on  the  sides,  the  lacerated  foramina — large  irregular 


Fig.  49. 


horse's  head  (anterior  face). 
1,  Occipital  tuberosity ;  2,  origin 
of  the  mastoid  crest ;  3,  parietal 
bone;  4,  saggital  suture  ;  5,  junc- 
tion of  the  parietal  and  temporal 
bones ;  6,  zygomatic  arch ;  7, 
frontal  bone ;  8,  frontal  suture ; 
9,  temporal  fossa ;  10,  supra-orbital 
foramen  ;  11, 12,  lachrymal  bone  ; 
13,  malar  bone  ;  14,  nasal  border  of 
frontal  bone  ;  15,  nasal  bone  ;  16, 
suture  of  nasal  bones;  17,  super- 
maxillary  bone ;  18,  infra-orbital 
foramen;  19,  anterior,  or  pre- 
maxillary  bone ;  20,  foramen  in- 
cisivum  ;  21,  incisor  teeth  (young 
mouth). 


horse's  head  (posterior  face). 
,  Occipital  tuberosity ;  2,  foramen  magnum  ;  3, 
3,  occipital  condyles;  4,  4,  styloid  processes; 
5,  5,  petrous  bone ;  6,  basilar  process ;  7,  ptery- 
goid fissure  of  the  sphenoid  bone ;  8,  foramen 
lacerum  ;  9,  9,  supra-condyloid,  or  anterior  mas- 
toid process;  10,  lo,  articular  eminence,  or 
temporal  condyle;  11,  body  of  sphenoid  bone; 
12,  pterygoid  process;  13,  ethmoid  bone;  14, 
temporal  bone  and  sphenoidal  suture;  15, 
lachrymal  bone;  16,  vomer;  17,  malar  Ijone ; 
18,  maxillary  tuberosity;  19,  posterior,  or 
guttural  opening  of  the  nose  ;  20,  palate  bone  ; 
21,  palatine  styloid  process;  22,  palato-maxil- 
lary  foramen ;  23,  palatine  process  of  superior 
maxillary  bone,  with  suture  ;  24,  ditto  of  pre- 
maxillary  bone;  25,  premaxillary  bone;  26, 
upper  incisor  teeth  ;  27,  point  of  junction  of 
the  premaxillary  with  the  superior  maxillary 
bone  ;  28,  upper  molar  teeth  (young  mouth). 


openings  divided,  in  the  fresh  state,  into  two  portions  {anterior  and  posterior 
lacerated  foramina).  To  the  outside  of  these  openings  is  the  base  of  the  tuberous 
portion  of  the  temporal  bones,  especially  the  tympanic  bulb  ov petrous  bone ;  above 


82  THE  BONES. 

are  the  condyloid  fossae,  with  their  condyloid  foramen.,  and  the  styloid  processes  of 
the  occipital  hone  or  Jugular  eminences. 

2.  Suhsphenoidal  region. — This  region  is  notably  constricted  in  its  middle 
part,  where  it  has  for  base  the  body  of  the  posterior  sphenoid  bone  ;  it  is  enlarged 
above  by  the  temporal  articular  surfaces.  It  is  limited  by  the  inferior  border 
of  the  foramen  lacerum,  on  which  are  three  notches  transformed  into  foramina 
by  the  tissue  that  partitions  the  foramen  lacerum  basis  cranii  in  the  fresh 
state.  These  openings  are,  passing  from  within  to  without,  the  carotid  or  cavernous 
foramen,  the  foramen  ovcde  or  foramen  rotundum ;  they  are  all  preceded  by  a 
groove  on  the  surface  of  the  bone.  On  each  side  of  the  body  of  the  sphenoid  is 
the  narrow  Vidian  fissure,  prolonged  by  the  Vidian  canal,  and  margined  outwardly 
by  the  origin  of  the  suhsphenoidcd  process.  Laterally,  is  the  suhsphenoidal  canal 
for  the  passage  of  the  internal  maxillary  artery,  which  is  continued  forward 
by  two  branches,  one  of  which  opens  into  the  orbital  hiatus,  the  other  into  the 
temporal  fossa. 

3.  Spheno-pcdatine  region. — This  extends  from  the  superior  sphenoid  to  the 
palatine  arch.  In  the  median  plane  it  shows  a  vast  elliptical  opening — the 
gutturcd  opening  of  the  nascd  cavities,  divided  at  the  bottom  into  two  portions  by 
the  vomer,  and  bordered  laterally  by  two  elevated  crests  (pterygo-pcdatines) 
resulting  from  the  junction  of  the  pterygoids  with  the  palatine  crests  ;  and 
limited  in  front  by  the  posterior  border  of  the  palatine  bones,  which  is  raised  in 
its  middle  by  a  blunt  point  directed  backwards — the  nasal  spine.  Beyond  the 
pterygo-palatine  orests  is  a  slightly  depressed  surface,  on  which  run  the  branches 
of  the  internal  maxillary  artery  and  the  superior  maxillary  nerve.  This  surface 
extends,  above,  to  the  orhital  or  sphenoidctl  hiatus,  below  to  the  maxillary  hiatus. 
In  the  maxillary  hiatus  are  :  the  upper  opening  of  the  superior  dental  canal,  the 
palatine  caned,  and  the  nasal  foramen.  In  passing  from  the  maxillary  hiatus  on 
the  margin  of  the  guttural  opening  of  the  nasal  cavities,  we  meet  with  the 
staphyline  fissure,  which  is  limited  above  by  the  alveolar  tuberosity. 

4.  Pcdatine  region. — .This  is  a  wide  elongated  surface,  limited  laterally  by  the 
molar  teeth  and  interdental  spaces,  and  in  front  by  the  incisors.  It  shows  :  in 
the  middle,  the  pcdcdine  and  superior  maxillary  suture,  which  terminates  at  the 
incisive  canal ;  on  the  sides  and  above,  the  inferior  opening  of  the  pcdatine  grooves^ 
prolonged  by  the  pcdatine  fissures  ;  in  front,  the  incisive  slits. 

C.  Lateral  Face. — This  is  a  pair  face,  and  comprises  three  regions  (Fig.  51) : 

1.  Maxillary  region. — This  is  very  extensive.  Its  shape  is  triangular,  base 
superior — the  supermaxilla  being  joined  to  the  premaxilla.  Proceeding  backward, 
there  are  observed  :  a  fossa,  in  which  opens  the  infra^rhital  foramen  ;  the  lower 
orifice  of  the  superior  dental  canal,  pierced  above  the  third  molar  tooth  ;  the 
malar  or  zygomatic  spine — a  long  vertical  crest  for  the  insertion  of  the  masseter 
muscle,  commencing  above  the  fourth  molar  teeth,  and  continuing  upwards  with 
the  malar  bone  and  zygomatic  process.  Lastly,  the  maxillary  region  is  limited, 
above,  by  the  orbit  and  the  maxillary  tuherosity. 

2.  Orhital  region. — This  includes  the  orbit  or  orbital  cavity,  for  the  reception 
of  the  essential  and  some  of  the  accessory  organs  of  vision.  In  Man  and  the 
Quadrumana  this  cavity  has  complete  bony  walls,  but  in  the  domestic  animals  it 
always  largely  communicates  with  the  temporal  fossa,  and  it  is  not  always 
even  circumscribed  at  its  opening  by  a  soHd  ring.  A  fibrous  lining  {ocular  sheath) 
converts  it  into  a  distinct  cavity. 

In  the  Horse,  the  outline  of  the  orbit  is  constituted  :  below,  by  the  lachrymal 


THE  HEAD.  83 

bone  ;  above  and  in  front,  by  the  frontal  bone  and  its  process  ;  externally,  by 
the  malar  bone.  If  its  two  largest  diameters  are  measured,  it  is  remarked  that 
this  opening  is  scarcely  ever  regularly  circular,  its  width  varying  from  above  to 
below  or  from  without  to  within.  With  nine  Horses'  heads  of  various  ages  and 
breeds,  equal  diameters  were  found  in  only  one,  the  other  eight  being  unequal ; 
of  these,  the  vertical  diameter  of  the  orbit  predominated  in  five,  and  was  least  in 
three. 

In  the  Ass,  as  a  general  rule  the  vertical  diameter  is  smallest,  the  relation 
between  the  two  diameters  varying  from  ro9  to  1"15.  Otherwise,  the  entrance 
to  the  orbit  is  irregularly  square,  and  the  orbital  process  which  covers  it  is  much 
wider  and  more  salient  than  in  the  Horse — as  Lecoq  asserted,  and  as  the 
observations  of  Goubaux  and  Sanson  have  confirmed.  We  have  also  noticed 
these  differences,  and  they  are  not  the  only  ones  which  permit  the  skeleton  of 
the  Ass  to  be  recognized  ;  for  there  have  been  already  cited  those  of  the  spine 
and  bones  of  the  head — such  as  the  articular  depression  surrounding  the  basilar 
process,  the  vascular  furrow  on  the  styloid  process,  the  position  of  the  lachrymal 
tubercle,  and  the  conical  eminence  surmounting  the  premaxillary  symphysis, 
above  the  incisive  foramen  ;  others  will  be  noted  hereafter  (Figs.  51,  52). 

With  regard  to  the  cavity  of  the  orbit,  it  is  separated  from  the  maxillary 
hiatus  and  the  temporal  fossa  by  two  linear  imprints,  diverging  forwards,  to 
which  the  ocular  sheath  is  attached.  It  presents,  on  its  floor,  the  upper  orifice 
of  the  lachrymal  canal,  the  lachrymal  fossa,  where  the  small  oblique  muscle  of  the 
eye  has  its  fixed  insertion  ;  and  within  this,  but  higher,  the  little  depression  for 
the  bend  of  the  great  oblique  muscle  of  the  eye. 

3.  Temporal  region. — This  region  is  more  extensive  than  the  preceding,  and 
is  composed  of  three  principal  parts — the  temporal  fossa,  zygomatic  arch,  and 
petrous  portion  of  the  temporal  bone. 

The  temporal  fossa  surmoimts  the  orbit,  from  which  it  is  incompletely 
separated  in  Solipeds  and  Ruminants  by  the  orbital  arch  ;  in  the  other  domestic 
animals,  this  arch  is  incomplete  in  such  a  way,  that  in  the  skull  the  temporal 
fossa  is  confounded  for  the  greater  part  with  the  orbit.  Situated  obliquely  down- 
wards and  outwards  on  the  sides  of  the  cranium,  the  temporal  fossa  is  oval  in 
shape,  and  bounded  inwardly  by  the  occipital  or  temporal  crest,  outwardly  by 
the  anterior  border  and  longitudinal  root  of  the  zygomatic  process.  It  lodges 
the  temporalis  muscle  ;  consequently,  its  width  in  our  animals  is  proportionate  to 
the  power  of  that  muscle.  It  is  studded  with  muscular  imprints,  and  has  several 
vascular  foramina  which  enter  the  parieto-temporal  canal. 

The  zygomcitic  arch  is  formed  as  if  by  a  loop  thrown  from  the  cranium  on  to 
the  face,  outside  the  temporal  fossa  and  the  orbit.  It  is  constituted  by  the 
zygomatic  process  of  the  temporal  bone  and  the  malar  bone,  which  latter 
prolongs  it  to  the  maxillary  region. 

The  tuberosity  of  the  temporal  bone  shows,  outwardly,  the  external  auditory 
canal,  usually  larger  in  the  Ass  than  the  Horse.  Between  this  orifice  and  the 
supra-condyloid  eminence  is  the  opening  of  the  parieto-temporal  canal ;  and 
behind  the  latter  are  several  irregular  ridges,  one  of  them  being  the  hyoid 
process.  The  external  face  of  the  tympanic  case  is  also  studded  with  some 
styloid  prolotiyations,  one  of  which,  more  developed  than  the  others,  serves  for 
the  insertion  of  the  peristaphyline  muscles.  Above  the  hyoid  process  is  the 
mastoid  process,  and  between  these  two  parts  is  the  external  orifice  of  the  aqueduct 
of  Fallopius.     From  the  mastoid  process  extends  the  mastoid  crest,  the  summit  of 


84 


THE  BONES. 


which  meets  the  external  occipital  protuberance  ;  it  is  crossed  by  the  mastoid 
groove,  which  gives  the  mastoid  artery  passage  to  the  parieto-temporal  canal. 
All  of  the  petrous  portion  is  surrounded  by  deep  clefts,  resulting  from  the 
simple  union  of  this  bone  with  its  neighbouring  pieces. 

D.  Base. — The  base  or  superior  extremity  of  the  head,  formed  by  the 
occipital  bone,  represents  a  trapezoid  surface,  incurvated  from  before  to  behind. 
It  is  separated  from  the  anterior  face  by  the  external  occipital  tiiherosity,  the 
projection  of  which  is  always  greater  in  the  Ass  and  Mule  than  in  the  Horse, 
with  the  exception  of  the  English  Horse,  in  which  it  has  been  found  very 
developed  (Figs.  51,  52).     It  is  separated  from  the  lateral  faces  by  two  crests — 


Fig.  51. 


_         19  IS         12  17  22 

horse's  head  (lateral  face). 

1,  Occipital  condyle;  2,  styloid  process  of  the  occipital  bone;  3,  external  occipital  tuberosity, 
4,  parietal  crest ;  5,  external  auditory  hiatus ;  6,  zygomatic  process  of  the  temporal  bone ;  7, 
frontal  bone;  8,  orbit;  9,  lachrymal  bone  and  its  tubercle;  10,  zygomatic  or  malar  bone  ;  11, 
nasal  bone;  12,  supermaxillary  bone;  13,  zygomatic  spine;  14,  infia-orbital  foramen;  15,  pre- 
maxillary  or  intermaxillary  bone;  16,  incisor  teeth;  17,  molar  teeth;  18,  inferior  maxilla;  19, 
maxillary  fissure;  20,  maxillary  condyle;  21,  coronoid  process  of  the  maxilla;  22,  mental 
foramen;  23,  supra-orbital  foramen  ;  24,  basilar  process  of  the  occipital  bone. 


the  superior  curved  lines — which  are  prolonged  backwards  on  the  styloid  processes 
of  the  occipital  bone. 

In  the  middle  plane  is  the  occipital  crest,  behind  the  tuberosity  ;  it  terminates, 
in  becoming  gradually  effaced,  at  the  orripital  foramen,  which  is  bordered 
on  each  side  by  the  condyles  of  the  occiput.  The  condyles  are  separated 
from  the  styloid  processes  by  two  deep  notches — the  stylo-condyloid  notches. 
Between  the  middle  line  and  the  superior  curved  lines,  are  muscular  imprints 
irregularly  arranged  in  a  half -circle — these  are  the  inferior  curved  lines. 

The  base  of  the  skull  joins  the  anterior  and  posterior  faces  in  forming  angles  ; 
these  possess  some  interest,  as  they  may  afford  an  important  differential 
character  between  the  Ass  and  Horse. 


THE   HEAD.  85 

If  one  of  the  branches  of  a  goniometer  be  placed  tangentiallj  to  the  surface 
of  the  basilar  process,  and  the  other  to  the  summit  of  the  external  occipital 
tuberosity,  the  basilo-occipital  angle  will  be  obtained.  In  the  measurements 
we  have  taken  of  eight  heads  of  Horses  of  diverse  ages  and  breeds,  this  angle 
has  varied  from  70°  to  91°.  We  except  the  head  of  a  young  English  Stallion, 
the  basilo-occipital  angle  of  which  was  from  92°  to  100°.  Measurement  of  the 
heads  of  Asses  showed  the  angle  to  be  103°.  The  average  basilo-occipital  angle 
was  85*36°  for  the  Horse,  and  95°  for  the  Ass. 

If,  instead  of  taking  the  basilo-occipital  angle,  the  goniometer  be  applied  to 
the  origin  of  the  temporal  crests  and  the  superior  outline  of  the  occipital 


Fig.  52. 


ass's  head  (lateral  face). 

,  Occipital  condyle ;  2,  styloid  process  of  the  occipital  bone,  with  a  very  marked  furrow  on  its 
external  face;  3,  external  occipital  tuberosity,  more  developed  than  in  the  horse;  4,  parietal 
crest ;  5,  external  auditory  hiatus ;  6,  zygomatic  process  of  the  temporal  bone ;  7,  frontal  bone ; 
8,  orbit,  with  its  external  outline  more  angular  than  in  the  horse;  9,  lachrymal  bone,  with  its 
tubercle  partly  implanted  on  the  nasal  bone;  10,  zygomatic  or  malar  bone;  11,  nasal  bone; 
12,  supermaxilla ;  13,  zygomatic  spine;  14,  infra-orbital  foramen;  15,  premaxillary  bone,  with 
its  inner  border  raised  by  a  salient  tubercle  above  the  incisive  canal  ;  16,  incisor  teeth ;  17, 
molar  teeth;  18,  inferior  maxilla;  19,  maxillary  fissure;  20,  maxillary  condyle;  21,  coronoid 
process  ;  22,  mental  foramen  ;  23,  supra-orbital  foramen,  carried  more  to  the  middle  of  the  orbital 
process  than  in  the  horse  ;  24,  basilar  process  of  the  occipital  bone. 


In  the  Horse,  this  angle  is 
and  S7° — the  average  being 


foramen,  the  parieio-occipifal  angle  is  obtained 
between  81°  and  104°  ;  in  the  Ass  between  7' 
91-12°  for  the  Horse,  and  84°  for  the  Ass. 

It  was  foreseen  that  the  value  of  these  angles  would  be  in  inverse  relation. 
In  all  cases  when,  on  a  head,  the  basilo-occipital  angle  was  found  very  open  and 
the  parieto-occipital  more  closed,  combined  with  a  great  development  of  the 
external  occipital  tuberosity  and  the  differential  characters  already  described, 
it  was  certain  to  be  the  head  of  an  Ass.     In  the  English  Horse,  the  external 


Sa  TEE  BONES. 

occipital  tuberosity  of  which  is  very  developed,  the  two  angles  in  question  are 
nearly  equal.  In  the  JIule  and  Hinny,  the  value  of  the  angles  is  intermediate 
between  the  Horse  and  Ass.  In  the  Mule,  the  mean  value  has  been  86-12°  for 
the  basilo-occipital  angle,  and  88°  for  the  parieto-occipital  angle.  In  the  Hinny, 
it  was  87°  for  the  first,  and  81°  for  the  second. 

E.  Summit. — This  results  from  the  union  of  the  four  faces  ;  but,  instead  of 
being  acute,  it  is  flattened  from  behind  to  before,  curved  from  side  to  side,  and 
furnished  with  the  incisor  teeth. ^ 

2.    CONFOEMATION   OF   THE    CrANIUM    IN   PARTICULAR. 

Retzius  was  the  first  to  start  the  idea  of  considering  the  cranium  of  Man 
independently  of  the  fafce.  He  distinguished  the  races  of  mankind  as  hrachtj- 
cephalic  (short-headed),  and  dolichocephalic  (long-headed) — that  is,  crania  long 
from  before  to  behind,  and  crania  relatively  short.  Broca  more  recently  compared 
the  transverse  diameter  of  the  cranium  with  the  antero-posterior  diameter  taken 
as  a  unit,  and  has  expressed  this  relation  in  hundredths  by  the  term  cephalic 
index.  For  some  years,  Sanson  has  endeavoured  to  introduce  into  the  classifica- 
tion of  animals  the  calculations  of  Retzius  and  Broca.  Taking  the  dimensions 
of  the  cranium  as  a  basis,  he  has  divided  Horses  into  two  groups — the  brachy- 
cephalic  and  the  dolichocephalic  kinds. 

If  the  cerebral  cranial  cavity — the  only  important  one  for  this  purpose — be 
enclosed  in  a  parallelogram,  two  sides  of  which  shall  be  at  a  tangent  to  the  most 
salient  points  of  the  parietal  bones,  and  the  other  two  pass  in  front  of  the 
external  auditory  canals  and  across  the  supra-orbital  foramina,  the  dimensions  of 
the  base  and  height  of  this  parallelogram,  measured  in  a  straight  line.,  will 
correspond  to  the  longitudmal  and  transverse  diameters  of  the  cranium.  In 
proceeding  thus,  Sanson  has  found  that  in  certain  crania  the  transverse  diameter 
is  greater  than  the  longitudinal  {brachycephalic  crania),  while  in  certain  others 
the  transverse  is  shorter  than  the  longitudinal  diameter  {dolichocq)halic  crcmia).^ 

Toussaint  took  direct  measurements  of  the  interior  of  the  cranium,  and,  no 
matter  what  the  breeds  of  horses  were  which  he  examined,  he  always  observed 
that  the  longitudinal  diameter  exceeded  the  transverse.  We  have  made  cranio- 
metrical  investigations  on  a  number  of  Horses,  and  are  able  to  confirm  Toussaint's 
statements.  In  eight  skulls  from  different  sources,  the  longitudinal  diameter 
varied  between  118  and  1S6  millimetres,  the  transverse  between  88  and  104 
millimetres.  Consequently,  in  none  of  these  animals  was  the  transverse  diameter 
equal  to  the  longitudinal.  In  the  number  examined  were  the  skulls  of  a  Syrian 
and  an  English  stallion — types  which  Sanson  would  have  selected  as  the  most 
brachycephalic  ;  the  relations  between  the  length  and  width  were  1'17  for  the 
first,  and  VSl  for  the  second.     The  average  for  the  eight  heads  was  1*24. 

We  are  of  opinion  that  there  are  no  brachycephalic  Horses,  in  the  rigorous 
sense  of  the  word,  such  as  Sanson  admits  ;  so  that,  if  it  is  attempted  to  establish 
brachycephalic  and  dolichocephalic  types,  it  will  be  necessary  to  previously  fix 
what  shall  be  the  limit  between  these  two  types,  and  this  has  not  yet  been  done. 

The  crania  of  Asses  from  the  south  of  France  are  longer  than  that  of  the 

'  For  the  regions  of  the  head,  see  Lavocat's  Nouvelle  Osteologie  compar€e  de  la  tete  des 
Animaux  Domestiques. 

^  Sanson,  "  Me'moire  sur  la  Nouvelle  determination  d'un  type  specific  de  race  Chevaline," 
Journal  de  VAnatomie  et  de  la  Physiologie,  de  Ch.  Robin,  1867;  also  the  later  works  of  M, 
Sanson. 


THE  READ.  87 

Horse  ;  for  in  eight  the  average  relation  between  the  length  and  width  was  1-25, 
instead  of  1'24 — a  difference  not  very  great,  certainly.  The  difference  becomes 
more  marked,  however,  between  the  Ass  and  Horse,  if  the  length  of  the  cerebral 
be  compared  with  that  of  the  cerebellar  cavity.  This  comparison  has  yielded  an 
average  of  1-962  in  the  Horse,  and  1-927  in  the  Ass — which  proves  that  the 
cerebellar  cranium  is  longer  in  the  Ass  than  the  Horse. 

The  cranium  is,  as  it  were,  strangled  behind  the  orbital  processes  of  the 
frontal  bones.  In  glancing  at  the  cranium  of  the  Horse  and  Ass,  it  would  at  first 
appear  that  that  of  the  Ass  is  relatively  narrower  than  the  cranium  of  the  Horse. 
We  have  measured  six  heads  of  each  species  for  the  width  of  the  cranium  at  its 
greatest  diameter,  behind  the  orbital  processes,  and,  in  comparing  these  two 
diameters,  have  obtained  the  following  results  :  in  the  H^orse,  the  relation  varied 
between  1-18  and  1-27  ;  in  the  Ass,  between  1-20  and  1-47.  The  average  has 
been,  for  the  Horse,  1-226,  and  1-335  for  the  Ass.  From  these  figures,  it  might 
be  concluded  that  the  cranium  of  the  Ass  is  relatively  more  constricted  at  its 
inferior  extremity  than  that  of  the  Horse.  In  the  hybrids  of  the  Horse  and 
Ass,  the  cranial  cavity  is  more  elongated,  and  in  this  respect  the  Hinny  more 
resembles  the  Ass  than  the  Horse.  With  regard  to  narrowness  of  the  crauium 
behind  the  orbital  processes,  the  Mide  holds  the  middle  place  between  its  parents, 
while  the  Hinny  comes  nearest  to  the  Ass — the  reverse  of  what  is  noticed 
in  the  development  of  the  cerebellar  cranium. 

In  Ruminants,  the  shape  of  the  cranium  is  more  or  less  masked  by  the 
frontal  or  parietal  sinuses  ;  consequently,  it  is  difficult  to  study  satisfactorily  this 
part  of  the  head,  particularly  in  the  bovine  species. 

The  cranium  of  the  domestic  Dog  offers  great  varieties  ;  for  the  creation  of 
numerous  breeds  has  brought  about  important  differences  in  the  form  and 
dimensions  of  this  part,  which  it  is  impossible  to  deal  with  here. 

3.  Relations  between  the  Cranium  and  Face. 
Instead  of  studying  the  cranium  alone,  we  may  compare  it  with  the  face  in 
regard  to  width,  length,  and  the  area  that  each  of  these  two  regions  occupies  in 
a  vertical  and  median  section.     We  may  also,  in  measuring  the  facial  angle,  form 
an  idea  of  the  manner  in  which  these  two  regions  unite  to  form  the  head. 

1.  The  forehead,  properly  speaking,  measured  from  the  union  of  the  parietal 
crests  to  the  fronto-nasal  suture,  is  always,  in  the  Horse,  longer  than  the  cerebral 
cranium,  the  second  to  the  first  being  as  1  :  1"425.  The  forehead  of  the  Ass  is 
proportionately  less  developed,  for  we  have  found  that  the  cranium  is  to  the 
forehead  as  1  :  1-265. 

2.  This  shortness  of  the  Ass's  forehead,  which  renders  the  head  heavy,  is 
corrected  by  its  narrowness  ;  the  head  enlarges  at  the  orbital  processes.  In  com- 
paring the  distance  between  the  supra-orbital  foramina  and  the  transverse 
diameter  of  the  cerebral  cavity,  it  has  been  noted  that  the  width  of  the  cranium 
is  to  the  space  between  these  foramina  as  1  :  1-454  in  the  Horse,  and  1  :  1-265  in 
the  Ass.  The  forehead  of  the  Ass  is,  therefore,  in  proportion  to  the  cranium, 
shorter  and  narrower  than  in  the  horse.  From  this  point  of  view,  the  heads  of 
the  3I'uIe  and  Hinny  are  intermediate  to  those  of  their  parents  ;  but  the  first  of 
these  hybrids  is  nearer  the  Horse,  and  the  second  approaches  the  Ass. 

3.  Cuvier  imagined  that  one  of  the  means  of  judging  of  the  intelligence  ot 
animals,  would  be  to  compare  the  area  of  the  cranium  with  that  of  the  face, 
measured  on  a  median  section  of  the  head,  deprived  of  the  lower  jaw.     This 


TEE  BOXEd. 


great  naturalist  remarked  that  the  area  of  the  cranium  diminishes  as  the  animals 
are  further  removed  from  the  hmuau  type,  while  the  area  of  the  face  increases 
in  the  same  sense.  Colin  has  studied  the  heads  of  the  domesticated  animals 
from  this  point  of  view.  Putting  to  one  side  the  surface  occupied  by  the 
sinuses,  he  found  that  the  area  of  the  cranium  to  the  face  was  as — 


1  :  2-69  in  the  Horse. 
1  :  2  09  in  the  Ass. 
1  :  3-43  in  the  Ox. 
1   :  2-20  in  the  Ram. 
1  :  1-95  in  the  Goat. 


1  :  3  24  in  the  Pig. 
1  :  117  in  the  Dog. 
1  :  0-68  in  the  Cat. 
1  :  1-47  in  the  Rabbit. 
1  :  054  in  the  Lamb. 


From  this  table  it  will  be  seen  that,  if  the  domesticated  animals  are  classified 
according  to  the  area  of  the  cranium,  they  will  stand  in  the  following  order  : 
Cat,  Dog,  Rabbit,  Goat,  Ass,  Ram,  Horse,  Pig,  and  Ox. 

4.  Camper  measured  the  facial  aiigU  by  drawing  two  lines,  starting  from  the 
entrance  to  the  nasal  cavities,  and  passing  towards  the  middle  of  the  external 
auditory  canal  and  towards  the  most  prominent  part  of  the  forehead.  The  facial 
angle  gives  an  idea  as  to  the  relative  volume  of  the  face  and  cranium,  and  the 
dimensions  of  the  latter  ;  but  with  animals  it  furnishes  very  imperfect  information, 
because  of  the  form  of  the  face  and  the  development  of  the  sinuses  around  the 
cranial  cavity. 

Colin  has  measured  the  facial  angle  of  the  domestic  animals,  by  drawing  two 
lines  from  the  upper  incisors  towards  the  external  auditory  canal  and  the  fore- 
head, in  the  point  corresponding  to  the  lower  end  of  the  brain  ;  and  he  obtained 
the  following  average  values  :  from  12°  to  15°  for  the  Horse  ;  16°  for  the  Ass  ; 
20°  for  the  Bull  ;  from  20°  to  25°  for  the  Ram  ;  from  3-4°  to  41°  for  Dogs  ;  and 
41°  for  the  Cat. 

On  the  other  hand,  we  have  measured  this  angle  in  Equines,  and  find  that  it 
varies  :  in  the  Horse,  between  11°  and  13°  ;  in  the  Ass,  between  12°  and  16°  ; 
and  in  the  Mule,  between  13°  and  15°.  In  the  Hinny,  it  measures  14°.  It  is 
somewhat  remarkable  that,  in  the  Equidae,  the  Ass  should  have  a  greater  facial 
angle  than  the  Horse. 

4.  Modifications  due  to  Age. 

Age  brings  modifications  bearing  upon  the  form  of  some  regions  of  the  head, 
the  development  of  external  peculiarities  of  the  bones,  the  shape  of  the  cranium, 
and  its  relations  with  the  surface. 

1.  It  has  been  remarked  that  the  development  of  the  occipital  tuberosity, 
the  temporal  crests,  and  the  lachrymal  tubercle,  increases  with  age  in  the  Equine 
species  ;  the  infra-orbital  foramen,  which  is  frequently  only  a  notch  in  youth, 
becomes  a  true  foramen  when  the  animal  is  advanced  in  age.  In  the  Foal,  the 
forehead  is  convex  ;  that  bone  and  the  nasal  bones  become  flat  as  the  creature 
grows,  and  sometimes  even  the  line  of  the  nasal  bones  is  concave  in  old  age.  The 
maxillary  region,  which  is  at  first  convex,  becomes  gradually  hollow  as  the  molar 
teeth  are  pushed  out  of  the  alveoli ;  while  the  straight  part  of  the  posterior 
border  of  the  inferior  maxilla  becomes  thin  and  sharp  in  very  old  Horses.  The 
entrance  to  the  orbit  is  also  notably  modified,  though  its  shape  is  not  identical 
in  all  the  animals.  In  every  instance,  it  has  been  remarked  that  the  direction  of 
the  larger  axis  of  the  orbital  cavity,  comprised  at  first  in  the  plane  which  passes 
by  the  auditory  canal  and  the  implantation  of  the  upper  incisors,  is  depressed  in 


THE  HEAD. 


front,  and  at  an  advanced  age  is  found  in  a  plane  passing  by  the  inferior 
extremity  of  the  zygomatic  crest  and  the  summit  of  the  external  occipital 
tuberosity. 

2.  If  the  cranium  be  examined  by  itself,  it  will  be  noted  that,  in  proportion, 
it  is  less  narrowed  behind  the  orbital  processes  in  the  young  animal  than  in  the 
adult.  With  regard  to  the  cerebellar  cranium,  it  is  elongated  when  the  animal 
is  aged — a  consequence  of  the  natural  development  of  the  external  occipital 
tuberosity. 

3.  The  relation  of  the  areas  of  the  cranium  and  face  change  with  age.  If 
the  measurements  obtained  by  Colin  on  the  Lamb  and  Ram  are  compared,  it 
will  be  perceived  that  the  face  grows  as  the  creature  ages.  This  change  is  very 
evident  if  the  development  of  the  young  Hare  is  watched.  At  birth  the  face  is 
very  short — like  that  of  a  common  dog,  it  is  said  ;  but  when  development  is 
completed,  we  know  how  much  the  face  has  become  lengthened. 

4.  Finally,  in  consulting  the  table  of  angles  drawn  up  by  Colin,  we  might 
believe  that  the  facial  angle  widens  as  the  animal  advances  in  age.  Thus,  in  the 
young  Hinny,  Colin  estunated  the  facial  angle  at  15°  ;  this  angle  was  16°  on  an 


Fig.  53. 


A,  B,  C,  D.     1,  Fronto-parietal  crests;  2,  external  occipital  tuberosity;  3,  3,  superior  root  of 
the  zygomatic  process  of  the  temporal  bone. 

old  Hinny,  and  17°  on  another  very  old  one.  In  every  instance,  however,  according 
to  the  same  table,  this  angle  will  be  equal  in  a  four-years-old  Horse  and  in  an 
adult  Horse  ;  and  even  in  the  Calf  it  diminishes  one  degree  when  it  becomes  an 
adult  animal. 

The  measurements  we  have  taken  in  domestic  Solipeds,  have  demonstrated 
that  the  facial  angle  diminishes  in  a  constant  manner  as  the  animal  grows  old. 
Thus,  this  angle  is  16°  in  an  Ass  three  years  old  ;  it  is  15°  in  the  adult,  and  12° 
in  the  very  old  Ass.  We  have  found  it  13°  in  a  Foal  of  two  years,  and  11°  in 
an  old  Horse  ;  15°  in  a  Mule  of  eighteen  months,  and  12*30°  in  a  very  aged 
Mule. 

This  question  has,  therefore,  to  be  again  examined  ;  and,  however  it  may  be 
decided,  it  will  be  seen,  by  what  has  been  stated,  that  age  induces  very  interesting 
changes  in  the  form  and  proportions  of  various  parts  of  the  head. 

If  the  crania  of  different  breeds  of  Dogs  are  compared,  there  will  be  found 
very  marked  diversities  in  the  prominence  of  the  parietal  convexity,  and  the 
development  and  distance  apart  of  the  fronto-parietal  crests.  A  mere  glance 
at  the  ligures  above  (Fig.  53),  will  afford  evidence  of  this. 


90  THE  BONES. 

On  the  cranium  of  the  Mastiff  (a),  the  parietal  bulgings  are  httle  marked ; 
the  parietal  crests  are  very  elevated,  and  join  each  other  early,  so  that  the 
temporal  muscles  are  in  contact  throughout  the  greater  part  of  their  inner 
margin.  In  the  little  Lap-dog  (d),  the  parietal  crests  are  widely  separated  from 
one  another,  and  the  cranium  is  so  very  convex  as  to  resemble  that  of  a  Monkey. 
Between  these  extremes  are  many  intermediates  (b,  c)  ;  and  it  would  appear 
that  the  development  of  inteUigence  in  the  Dog  results  in  rendering  the  parietal 
bones  more  convex,  and  the  temporal  fosssB  narrower. 


Comparison  of  the  Head  of  Man  with  that  of  the  Domesticated  Animals. 

1.  Occipital  hone. — The  occipital  of  Man  is  large,  flat,  incurvated  like  a  shell,  and  the  ex- 
ternal tuberosity  is  slightly  developed,  and  united  by  a  ridge  to  the  occipital  foramen,  which 
is  relatively  very  wide.  Two  series  of  ridges  arise  from 
the  external  tuberosity  and  pass  towards  the  circum- 
ference of  tlie  bone ;  these  are  the  superior  and  inferior 
curved  or  semicircular  lines.  There  is  an  anterior  and 
a  posterior  condyloid  fossa  pierced  by  a  foramen  at  the 
bottom;  and  the  jugular  eminences,  wide  and  slightly 
prominent,  replace  the  styloid  processes  of  the  domesti- 
cated animals. 

The  internal  face  of  the  occipital  of  Man  corresponds 
with  the  cer(  brum  and  cerebellum  ;  and  for  this  purpose 
it  shows  four  fossae,  distinguished  into  superior  or  cerebral, 
and  inferior  or  cerebellar.  These  fossse  are  separated  by 
a  crucial  projection  whose  most  developed  portion  forms 
the  internal  occipital  protuberance. 

The  union  of  the  occipital  with  the  parietal  bones,  con- 
stitutes the  liimlidoidal  suture.  At  the  point  where  this 
bone  meets  the  parietal  and  the  squamous  portion  of  the 
temporal,  is  found,  in  the  infant,  the  lateral  posterior 
fontanel. 

2.  Parietal  hones. — The  parietals  are  always  isolated 
in  early  life,  and  sometimes  consolidated  with  each  other 
at  the  adult  age.  They  are  very  large,  quadrilateral, 
and  occupy  the  summit  and  sides  of  the  cranium. 

The  parietal  crests  are  absent,  but  are  replaced,  in 
certain  individuals,  by  two  faintly  marked  curved  lines 
situated  a  little  above  the  inferior  border  of  the  bone. 
The  middle  portion  of  the  external  face  is  very  convex. 

On  the  internal  face  there  is  no  parietal  protuberance, 
but  in  its  stead  the  internal  occipital  tuberosity.  It 
also  exhibits  ramous  channels,  which  in  disposition  are 
analogous  to  the  ribs  of  a  tig-leaf ;  as  well  as  the  parietal 
fossa,  which  corresponds  to  the  parietal  eminence. 

3.  Frontal  hone. — The  frontal  bone  of  Man  forms  the 
upper  part  of  the  face  and  the  anterior  portion  of  the 
cranium.  Convex  from  behind  forward,  then  vertical  in 
its  upper  three-fourths,  the  bone  suddenly  bends  at  tlie 
orbits,  so  as  to  become  horizontal  in  its  lower  fourth. 

The  external  face  offers,  above  the  forehead,  two  Literal 
frontal  eminences,  and  above  the  nose,  a  middle  frontal 
boss.  To  the  right  and  left  of  the  latter  are  two  salient 
arches— the  supra-orbital  ridges.  The  internal  face  entirely  belongs  to  the  cranial  cavity.  It 
offers,  on  the  median  line,  the  saggital  groove  terminated  by  a  frontal  crest;  and  on  each 
side  of  this  line  the  frontal  fosste,  corresponding  to  the  eminences  of  that  name,  and  orbital 
bo.sses  to  match  the  orbital  roofs.  There  is  no  mortise  for  the  articulation  of  the  sphenoid  bone. 
On  the  middle  poition  of  the  superior  frontal  border,  in  young  persons,  is  the  anterior 
angle  of  the  anterior  fontanel.  The  anterior  border  exhibits  three  supra-orbital  foramina 
and  the  orbital  arches. 


front  view  of  the  human 
cranium. 

,  Frontal  bone  ;  2,  nasal  tuberosity  ; 
3,  supra-orbital  ridfijp ;  4.  optic 
foramen  ;  5,  sphenoidal  fissure ; 
6,  spheno-maxillary  fissure ;  7. 
lachrymal  fossa ;  8,  opening  of 
the  nose  divided  by  the  vomer;  9, 
infra-orbital  foramen;  10,  malar 
bone  ;  11,  symphysis  of  the  lower 
jaw;  12,  mental  foramen;  13, 
ramus  of  the  lower  jaw  ;  14,  parie- 
tal bone  ;  15,  coronal  suture  ;  16, 
temporal  bone  ;  17,  squamous 
suture  ;  18,  upper  part  of  the  great 
ala  of  the  sphenoid  bone;  19,  com- 
mencement of  the  temporal  ridge  ; 
20,  zygoma  of  the  temporal  bone 
concurring  to  form  tlie  temporal 
arch  ;  21,  mastoid  process. 


THE  HEAD. 


91 


Fig.  55. 


4.  Ethmoid  hone.— In  Man,  the  external  fa^e  of  the  lateral   masses— formed  by  a  very 
thin  lamina,  termed  the  os  planum  or  lamina  pap2/r«e«— belongs  to  the  internal  wall  of  the  orbit. 

5.  Sphenoid  bone.— TLiis  is  distinguished,  in  Man,  into  a  body  and  four  wings- two  large 
and  twfi  small. 

Tlie  inferior  surface  of  the  body  oflfers  nothing  remarkable,  except  the  presence  of  a  conical 
prolongation  named  the  beak  (rostrum)  of  the  .sphenoid.  The  external  face  of  the  greater 
wings  forms  part  of  the  temporal  fowsa,  as  also  the  external  wall  of  the  orbit.  At  the  union 
of  the  wing.s  with  the  body,  are  detached  two  bifid 
pterygoid  proce.-^ses ;  their  internal  branch  represents 
the  pterygoid  bones  of  animals.  There  is  no  sub- 
sphenoidal  canal. 

Tlie  two  lesser  wings  are  very  thin  and  triangular, 
and  visible  only  on  the  superior  surface  of  the  bone  ; 
they  constitute  the  processes  of  Ingrassias. 

On  the  internal  face  of  the  bone  are  found :  (1) 
a  deep  pituitary  fossa,  limited  by  four  cUnoid  pro- 
cesses; (2)  an  optic  fossa,  shallow,  showing  very 
short  optic  canals  transformed  into  foramina  ;  (3)  the 
sphenoidal  fissure,  which  replaces  the  great  super- 
spheiioidal  canal  in  the  Horse;  (4)  the  great  foramen 
rotundum;  (5)  the  internal  face  of  the  wings,  much 
excavated ;  (6)  the  foramen  ovale,  which  transmits 
the  inferior  maxillary  nerve ;  (7)  the  small  foramen 
rotundum  that  lodges  the  spheno-spinous  artery. 

6.  Temporal  hone. — In  the  squamous  portion  of 
the  temporal  bone  of  Man,  the  zygomatic  process  only 
rests  on  the  malar  bone,  as  in  Ruminants.  The  glenoid 
cavity  is  concave  in  every  sense,  ami  divided  into  two 
parts  by  an  opening  named  t\\e  fi'<sura  Glaneri ;  the 
anterior  portion  only  is  articular  — the  posterior,  lying 
against  the  external  auditory  canal,  does  not  belong 
to  the  articulation  ;  it  corresponds  to  the  supra-con- 
dyloid  eminence  of  the  Horse.  The  tuberous  portion 
is  consolidated  with  the  squamous.  It  is  divided  into 
a  mastoid  and  a  pyramidal  portion ;  the  latter  com- 
prises, in  its  turn,  the  petrous  an^l  tympanic  portions. 
The  mastoid  portions  correspond  to  the  mastoid  pro- 
cess, mastoid  protuberance,  and  superior  border  of  the 
petrous  bone  in  the  Horse.  It  presents  a  rugged 
mast(;id  process.  Above  this  is  the  mastoid  canal ; 
and  aliove  and  behind  it,  tlie  digastric  groove — tlie 
pyramid  forming  a  considerable  projection  in  the 
interior  of  the  cranium.  The  styloid  process  or  bone 
is  altogether  separate  from  the  other  pieces  of  the 
hyoid,  and  in  the  adult  is  consolidated  with  the  tem- 
poral bone. 

7.  Supermaxilla. — In  Man  the  premaxilla  is  no 
longer  found  independent,  the  centre  which  forms  it 
coalescing  with  the  supermaxillary  bone. 

The  supermaxilla  of  man  concurs,  for  the  greater 
part  of  its  extent,  to  form  the  floor  of  the  orbit ;   it 

is  also  divided  into  three  faces :  an  external  or  facial,  a  superior  or  orbital,  and  an  internal 
or  naso-palatine.  The  external  face  presents,  from  before  to  behind:  (1)  a  small  fossa,  into 
which  is  inserted  the  niyrtiform  muscle;  (2)  the  infra-orbital,  or  canine  fossa,  showing  the 
inferior  orifice  of  the  infra-orbital  canal;  (3)  a  crest  corresponding  to  the  maxillary  spine  of 
Solipeds  :  (4)  the  alveolar  tuberosity.  This  face  carries,  in  front,  a  prolongation  that  forms  the 
ascending  process,  also  named,  because  of  its  relation,  the  tronto-nasal  process.  The  superior 
or  orbital  face  oflfers  a  fissure  which  precedes  the  infra-orbital  canal,  and,  outwards,  the  malar 
process.  The  internal  face  is  divided  by  the  palatine  process.  It  shows,  in  front,  the  half  of 
the  anterior  nasal  spine  and  a  groove  which  participates  in  the  formation  of  the  incisive  canal. 

8.  Palatine  fcojie.- The  palatine  bone  of  Man  isformedof  two  osseous  laminae— one  horizontal, 
the  other  vertical— which  are  joined  at  a  right  angle.     The  first  part  presents :  one-half  of  the 


EXTERNAL   OR   BASILAR   SURFACE    OF 
THE    BASE    OF   THE    HUMAN    SKULL. 

,  ],  The  bony  palate;  2,  incisive,  or 
anterior  palatine  foi-amea;  3,  pala- 
tine process  of  p  date  bone,  with  the 
posterior  palatine  foramen ;  4,  palate 
spine  with  transverse  ridge  ;  5,  vomer ; 
6,  internal  pterygoid  palate  ;  7,  sca- 
phoid fossa;  8,  external  pterygoid 
plate,  with  fossa  ;  9,  zygomatic  fossa  ; 

10,  basilar  process  of  occipital  bone  ; 

11,  foramen  magnum;  14,  glenoid 
fossa;  15,  meatus  auditorius  exter- 
nus ;  16,  foramen  lacerum  anterius  ; 
17,  carotid  foramen  of  left  siile;  18, 
foramen  lacerum  posterius,  or  jugular 
foramen;  19,  styloid  process;  20, 
stylo-mastoid  foramen,  with  jugular 
tubercle  and  digastric  fossa  ;  21,  mas- 
toid process  ;  22,  occipital  bone  ;  23, 
posterior  condyloid  fossa. 


92  THE  BONES. 

posterior  nasal  spine,  whicli  is  altogether  rudimentary,  or  even  null  in  animals  ;  the  orifice  of 
the  posterior  palatine  canal,  which  belongs  entirely  to  the  palate  boue;  the  pterygo-palatine 
foramen ;  lastly,  the  pterygoid  process,  which  represents  tiie  pterygoid  bone  of  animals.  The 
vertical  portion  foims  the  external  wall  of  the  nasal  cavities  by  its  internal  face,  and  by  its 
external  face  concurs  in  the  formation  of  the  zygomatic  or  temporal  fossa. 

9.  Malar  bone. — This  oflfers  three  faces.  The  external,  or  cutaneous,  serves  as  a  base  for  the 
most  salient  part  of  the  cheek.  The  superior,  or  orbital,  forms  part  of  the  external  wall  and 
floor  of  the  orbit ;  it  belongs  to  a  long  apophysis — the  orbital  process — which  rests  on  the 
sphenoid  and  frontal  bones.  The  posterior  face  is  smooth  and  concave  behind,  where  it  aids  to 
form  the  temporal  fossa;  in  front  it  is  uneven,  and  articulates  with  the  supermaxilla.  The 
posterior,  or  masseteric  border,  unites  with  the  zygomatic  process  of  the  temporal  bone. 

10.  Lachrymal  bone.  — This  bone  is  also  called  the  os  unguis  in  Man,  because  of  its  likeness 
to  the  nail  in  shape  and  tenuity.  It  is  entirely  lodged  in  the  orbit,  and  its  external  face  is 
divided  into  two  portions  by  a  vertical  crest ;  the  portion  situated  in  front  of  this  crest  forms 
part  of  the  lachrymal  groove.  By  its  internal  face,  the  lachrymal  bone  limits,  outwardly, 
the  bottom  of  the  nasal  cavities,  and  covers  the  anterior  cells  of  the  ethmoid  ;  by  its  posterior 
border,  within  the  orbit,  it  articulates  with  the  os  planum  of  the  ethmoid. 

11.  Nasal  bone. — The  proper  bones  of  the  nose  of  Man  exhibit  a  great  analogy  to  those  of 
the  Dog.  Tliey  do  not  possess  a  nasal  prolongation,  and  they  articulate  with  the  lateral 
cartilage  of  the  nose. 

12.  Vomer. — The  same  general  form  and  relations  as  in  Solipeds. 

13.  Inferior  maxillary  bone. — This  bone  in  Man  is  in  shape  somewhat  like  a  horse-shoe.  It 
is  nearly  of  the  same  witlth  throughout  its  whole  extent.  The  symphysis  is  vertical — a 
character  peculiar  to  Man.  Below  this  symphysis  is  a  triangular  projection — the  mental 
eminence.  The  genial  surface  of  the  Horse  is  replaced  by  four  little  tubercles,  termed  the 
genial  processes.  The  alveoli  of  the  molar  teeth  form  a  great  projection  on  the  inner  face  of 
the  bi)ne.  The  mylo-hyoid  ridge  is  very  developed.  The  superior  orifice  of  the  dental  canal 
is  covered  by  a  little  sharp  lamina.  From  this  oritice  begins  the  mylo-hyoidean  groove.  The 
coronoid  process  is  short ;  the  condyle  is  bent  towards  the  median  line,  and  the  sigmoid  notch 
is  wide  and  shallow.     The  superior  border  contains  fourteen  or  sixteen  alveoli. 

Aeticle  III. — The  Thorax. 

The  thorax  represents  a  coinoid  cage,  elongated  from  before  to  behind, 
suspended  under  the  vertebrae  of  the  dorsal  region,  and  contains  the  principal 
organs  of  respiration  and  circulation.  It  is  composed  of  bony  arches  named 
ribs,  thirty-six  in  number — eighteen  on  each  side — and  a  single  piece — the 
sternum,  which  serves  for  the  direct  or  indirect  support  of  the  inferior  extremi- 
ties of  the  ribs. 

The  Bones  of  the  Thorax  in  particular. 
1.  Sternum  of  the  Horse  (H^jial  Spine)  (Fig.  56). 

This  is  an  osteo-cartilaginous  body,  elongated  from  before  backwards, 
flattened  on  each  side  in  two-thirds  of  its  anterior  extent,  and  above  and  below 
in  its  posterior  third  ;  it  is  slightly  curved  on  itself,  and  situated  beneath  the 
thorax  in  an  oblique  direction  downwards  and  backwards.  It  offers  for  study,  a 
superior  face,  two  lateral  faces,  three  borders,  and  two  extremities. 

Faces. — The  superior  face,  shghtly  concave  longitudinally,  represents  an 
isoscelated  lengthened  triangle,  the  summit  of  which  is  directed  forwards  ;  it 
constitutes  the  floor  of  the  thoracic  cavity.  The  inferior  face  is  shaped  like  the 
keel  of  a  ship,  having  in  its  middle  a  longitudinal  ridge,  which  decreases  in 
height  from  before  to  behind.  It  has  two  inclined  planes  placed  towards  each 
other,  each  of  which  has  two  parts — a  superior  and  an  inferior.  The  first  shows 
eight  diarthrodial  cavities,  which  receive  the  inferior  extremity  of  the  cartilages  of 
the  true  ribs.    These  cavities  are  elongated  vertically,  and  draw  closer  to  each  other 


THE  THORAX.  93 

as  they  extend  backwards.  The  inferior  part,  which  is  more  extensive  before 
than  behind,  offers  to  the  powerful  pectoral  muscles  a  large  surface  for  insertion.^ 

Borders. — The  two  inferior  borders  separate  the  superior  from  the  inferior 
faces  ;  they  are  situated  above  the  diai-throdial  cavities,  are  united  anteriorly,  and 
each  gives  attachment  to  a  fibrous  band. 

Extremities. — The  anterior,  flattened  on  each  side  and  curved  upwards,  exceeds 
to  some  extent  the  first  articular  cavity  of  the  lateral  faces,  and  in  this  way  con- 
stitutes the  cervical  prolongation  {prcesternum)  of  the  sternum.  The  posterior 
extremity  is  flattened  superiorly  and  inferiorly,  and  forms  a  large  cartilaginous 
plate,  very  thin,  concave  above,  convex  below,  which  has  received  the  name  of 
the  abdominal  prolongation  (ensiform  cartilage),  or  xiphoid  appendage. 

Structure  and  development, — The  sternum  is  one  of  the  parts  of  the  skeleton 

Fig.  56. 


THE    STERNUM. 

1,  The  cervical  prolongation  (prcesternum,  or  cariniform  cartilage) ;  2,  the  xiphoid  appendage  (or 
ensiform  cartilage);  3,  3,  cavities  for  the  articulation  of  the  sternal  cartilages  ;  4,  inferior  burder. 

which  do  not  undergo  complete  osseous  transformation.  It  is  developed,  in 
Solipeds,  from  six  single  nuclei  of  spongy  substance,  ranged  one  behind  the 
other,  like  beads  on  a  string.  These  nuclei  never  coalesce  to  form  a  solid  piece, 
but  remain  separated  during  the  life  of  the  animal,  by  the  primary  cartilaginous 
mass.  The  latter  constitutes  the  entire  anterior  prolongation  of  the  bone  and  its 
carina,  as  well  as  the  xiphoid  appendage.  When  these  parts  of  the  sternum 
become  ossified — which  is  rare — they  are  only  partially  so. 

Differential  Characters  in  the  Sternum  op  other  Animals. 

In  all  the  domesticated  animals  except  Solipeds,  tlie  sternum  is  flattened  above  and  below 
instead  of  ou  both  sides. 

A.  Ruminants. — In  Ruminants,  each  piece  is  developed  from  two  lateral  centres  of  ossifi- 
cation. The  bones  wliich  compose  it  are  seven  in  number;  they  are  much  more  compact  than 
those  in  the  sternum  of  the  horse,  and  at  an  early  period  are  united  to  each  other,  with  the 
exception  of  tl:e  first,  which  is  joined  to  the  secmid  by  a  diarthrodial  articulation  tliat  permits 
it  to  execute  lateral  movements.  There  is  no  cervical  prolongation,  and  the  xiphoid  cartilage 
is  feebly  developed  and  well  detached  from  the  bodv  of  tiie  bone.  In  the  sternum  of  the  Goat 
and  Sheep,  the  two  first  pieces  have  no  diarthrodial  joint,  but  are  simply  united  by  a  layer  of 
cartilage,  which,  in  old  animals,  becomes  completely  ossified.  The  sternum  of  the  Camel  has 
a  very  oblique  direction  downwards  and  backwards,  and  is  formed  by  seven  pieces  ;  the  first  is 
somewhat  rudimentary,  while  the  two  are  very  strong,  and  serve  as  a  base  for  the  sternal 
callosity  or  pad. 

B.  Pig. — Tlie  sternum  of  this  animal  presents  in  its  general  conformation  the  essential 
features  of  that  of  large  Ruminants.  It  is  provided  with  a  well-defined  cervical  prolongation, 
and  is  composed  of  six  pieces,  which,  at  least  in  the  four  or  five  last,  are  each  divided  into  two 
lateral  nuclei. 

C.  Carnivora. — ^The  sternum  of  the  Dog  and  Cat  is  formed  of  eight  pieces,  elongated  from 
before  to  beliiud,  hollowed  in  their  middle  part,  and  thick  at  their  ends— formed,  indeed,  like 
the  last  coccygeal  vertebrae  of  the  Horse.     They  are  never  ossified  to  each  other. 

9 


94 


THE  BONES. 


2.  The  Ribs  (Pleuropophyses)  (Fig.  57). 

As  has  been  already  remarked,  on  each  side  of  the  thorax  there  are  eighteen 
ribs.  These  are  nearly  parallel  to  each  other,  and  separated  by  the  intervals 
termed  the  intercostal  spaces.  Attached  by  their  superior  extremity  to  the 
vertebrse  of  the  dorsal  region,  these  bones  terminate  at  their  inferior  extremity 
by  an  elastic  and  flexible  prolongation,  named  the  costal  cartilage,  by  means  of 
which  they  are  brought  into  direct  or  indirect  relations  with  the  sternum.     The 

characters   common   to   all  the 
^'S-  ^^-  ribs  will  be  first  noticed,  then 

the  special  features  which  serve 
to  distinguish  them  from  each 
other,  and,  lastly,  the  differences 
they  exhibit  in  other  than  Soh- 
ped  animals. 

A.  Characters  common  to 
ALL  THE  Ribs. — These  will  be 
studied  from  a  typical  point  of 
view,  first  in  the  rib  itseK,  and 
then  in  its  cartilage. 

1.  Description  of  a  typical 
rib. — A  rib  is  an  elongated 
asymmetrical  bone,  oblique  from 
above  to  below,  and  from  before 
to  behind,  flattened  on  both 
sides,  curved  hke  a  bow,  and 
twisted  on  itself  in  such  a  fashion 
that  its  two  extremities  cannot 
rest  on  the  same  horizontal 
plane.  It  is  divided  into  a 
middle  portion  or  bod//,  and  tivo 
extremities. 

3Iiddle  portion. — This  offers 
two  faces  and  two  borders.  The 
external  face  is  convex,  and 
hollowed  by  a  wide  groove  in 
its  anterior  half ;  it  shows 
superiorly,  towards  the  point 
corresponding  to  the  angle  of 
the  rib  in  Man,  some  tubercles 
and  muscular  imprints.  The 
internal  face  is  concave  and 
smooth,  and  covered  by  the 
pleura,  which  separates  it  from 
the  lungs.  The  anterior  border 
is  concave,  thin,  and  sharp ;  the  posterior — convex,  thick,  and  covered  with  rugged 
eminences — is  channeled  iuAvardly  by  a  vasculo-nervous  groove,  which  disappears 
near  the  middle  of  the  rib. 

Extremities. — The  superior  has  two  eminences— a  head  {capitidum)  and  a 
tuberosity  (tuberculum) — which  serve  for  the  support  of  the  rib  against  the  spine. 


TYPICAL   RIBS   OF   THE   HORSE. 

,  Inner  face  of  the  fifth  sternal  rib.  B,  External  face 
of  the  first  asternal  rib.  1,  Head  of  the  rib;  2,  its 
fissure ;  3,  neck  ;  4,  tuberosity  ;  5,  articular  facet ; 
6,  scabrous  fossa  for  the  insertion  of  the  interosseous 
costo-transverse  ligament ;  7,  groove  on  the  external 
face  ;  8,  vasculo-nervous  groove  on  the  posterior  border  ; 
9,  prolonging  cartilage ;  10,  A,  articular  tuberosity 
for  union  with  the  sternum. 


THE  THORAX.  9S 

The  first  is  formed  by  two  articular  demi-facets,  placed  one  before  the  other,  and 
separated  by  a  groove  for  ligamentous  insertion  ;  it  is  isolated  from  the  tuberosity 
by  a  narrow  part,  named  the  neck,  which  exhibits  a  rugged  fossa  for  the  implantation 
of  a  ligament.  The  second — situated  behind  the  head,  and  smaller  than  it — is 
provided  with  imprints  on  its  margin,  and  presents  an  almost  flat  diarthrodial  facet 
at  the  summit.  Each  rib  articulates  by  its  head  and  tuberosity  with  two  dorsal 
vertebrse  ;  the  head  is  received  into  the  intervertebral  articular  cavity  ;  the  tube- 
rosity corresponds,  by  its  facet,  to  the  transverse  process  of  the  posterior  vertebra. 

The  inferior  extremity  is  tuberous  and  excavated  by  a  shallow  cavity, 
irregular  at  the  bottom,  for  the  reception  of  the  upper  end  of  the  costal  cartilage. 

Structure  and  development. — The  ribs  are  very  spongy  bones,  especially  in  their 
inferior  moiety,  and  are  developed  at  a  very  early  period  from  three  centres  of 
ossification — a  principal  for  the  middle  portion  and  inferior  extremity,  and  two 
complementary  for  the  head  and  tuberosity. 

2.  Description  of  a  typiccd  costal  cartilage. — The  costal  cartilage  QicBmapopliysis) 
very  evidently  represents  the  inferior  rib  in  Birds  ;  it  is  a  cylindrical  piece, 
slightly  compressed  at  the  sides,  and  round  and  smooth  on  its  faces  and  borders. 
By  its  superior  extremity,  it  is  united  to  the  rib  it  serves  to  lengthen,  and  forms 
with  it  an  angle  more  or  less  obtuse,  opening  in  front.  At  its  inferior  extremity, 
it  is  terminated  by  an  articular  enlargement,  or  by  a  blunt  point.  In  youth,  the 
costal  prolongations  are  entirely  composed  of  cartilaginous  matter,  but  they  are 
soon  invaded  by  ossification  ;  so  that  in  the  adult  animal  they  are  already  trans- 
formed into  a  spongy,  substance,  with  large  areolae  which  remain  during  life 
surrounded  by  a  thin  layer  of  cartilage. 

B.  Specific  Characters  of  the  Ribs. — The  ribs,  hke  the  vertebra  of 
each  region  of  the  spine,  have  received  numerical  designations  of  first,  second, 
third,  etc.,  computing  them  from  before  to  behind  (Fig.  5).  Owing  to  the 
presence  of  an  altogether  essential  characteristic,  they  are  naturally  divided  into 
two  great  categories — the  sternal  or  true  ribs,  and  the  asternal  or  false  ribs.  The 
sternal  ribs,  numbering  eight — the  first  eight — have  their  cartilages  terminated 
inferiorly  by  an  articular  enlargement,  which  corresponds  to  one  of  the  lateral 
cavities  of  the  sternimi,  and  brings  the  true  ribs  into  direct  contact  with  this 
portion  of  the  skeleton.  The  asternal  ribs,  ten  in  number,  rest  on  each  other — 
the  last  on  the  seventeenth,  that  on  the  sixteenth,  and  so  on — by  the  inferior 
extremity  of  their  cartilage,  which  ends  in  a  blunt  point.  The  cartilage  of  the 
first  false  rib  is  united  somewhat  closely  to  the  last  sternal  rib,  and  it  is  through 
the  medium  of  this  that  all  the  asternal  ribs  lie  indirectly  on  the  sternum. 

If,  however,  the  ribs  are  considered  altogether,  with  regard  to  the  differential 
characters  presented  by  them  in  their  length,  width,  and  degree  of  incurvation, 
it  will  be  noted  :  1.  That  their  length  increases  from  the  first  to  the  ninth,  and 
from  this  diminishes  progressively  to  the  last,  2.  That  the  same  progressive 
increase  and  decrease  exists  in  the  cartilages.  .3.  That  they  become  gradually 
wider  from  the  first  to  the  sixth  inclusive,  and  then  contract  by  degrees  until  the 
eighteenth  is  reached  :  4.  That  the  curve  described  by  each  is  shorter  and  more 
marked  as  the  rib  is  situated  more  behind.  It  may  be  added,  that  the  channel 
on  the  external  face  is  less  conspicuous  in  proportion  as  the  rib  is  narrow. 

The  first  rib,  considered  individually,  is  always  distinguished  by  the  absence 
of  the  groove  on  its  outer  surface,  by  the  vasculo-nervous  groove  on  its  posterior 
border,  and  the  groove  or  notch  intermediate  to  the  two  facets  of  its  articular 
head.     It  is  also  recognized  by  the  deep  muscular  imprints  on  its  external  face, 


96  THE  BONES. 

the  shortness  and  thickness  of  its  cartilage,  and  particularly  by  the  articular  facet 
which  this  cartilas^e  exhibits  inwardly,  to  correspond  to  that  of  the  opposite  rib. 
The  last  rib  has  no  channel  on  its  external  surface,  and  the  facet  of  its  tuberosity 
is  confounded  with  the  posterior  facet  of  the  head.  This  last  character  is  also 
nearly  always  remarked  in  the  seventeenth  rib,  and  sometimes  even  in  the 
sixteenth. 

In  the  Ass,  the  ribs  in  general,  but  particularly  those  most  posterior,  are  less 
curved  than  in  the  Horse.  They  differ  more  particularly  in  the  curve  of  the  neck 
being  much  shorter — a  difference  which  is  most  obvious  when  the  goniometer  is 
applied  to  the  angle  of  the  rib,  and  the  most  salient  part  of  the  head  and  tube- 
rosity. By  this  means  we  have  obtained  an  angle  the  value  of  which  was  greater 
in  the  Ass  than  in  the  Horse  :  from  7><°  to  130°  for  the  external  ribs,  and  from 
100°  to  132°  for  the  asternal  ribs,  of  the  first  ;  from  60°  to  125°  for  the  sternal, 
and  from  140°  to  150°  for  the  asternals,  of  the  second.  The  upper  extremity  of 
the  sternal  ribs  in  the  Ass  is  less  twisted  outwards  than  the  same  part  in  the 
Horse  ;  and  in  the  latter,  the  plane  which  passes  by  the  head  of  the  rib  is  more 
distant  than  the  plane  which,  in  the  Ass,  passes  across  the  tubercle. 

The  ribs  of  the  Mule  are  intermediate  between  those  of  the  Ass  and  Horse, 
with  regard  to  the  value  of  the  angle  just  indicated  ;  they  approach  those  of  the 
Ass  by  the  twist  in  their  superior  extremity. 

Differential  Characters  in  the  Ribs  of  other  Animals. 
The  number  of  rib:^  varies  like  that  of  tlie  dorsal  vertebrae.     The  following  table'* indicate 
the  number  uf  these  bones  in  the  different  domesticated  animals  :  — 

Pig 14 

Ox l.S 

Sheep 13 

Goat 13 

Dog 13 

Camel     ...          12 

Rabbit 12 

A.  Ruminants. — These  animals,  with  the  exception  of  the  Camel,  have  eight  sternal  and 
five  asternal  ribs. 

In  the  Ox,  they  are  longer,  wider,  and  less  arched  than  in  Solipeds.  The  articular 
eminences  of  the  superior  t-xtremity  are  voluminous  and  well  <letafhed;  the  neck  especially  is 
very  long.  The  sternal  ribs  are  joined  to  their  cartilage  of  prolnngment  by  a  real  diarthrodiai 
articulation.  In  the  last  rib,  and  sometimes  in  tlie  one  before  it,  the  tuberosity  is  scarcely 
perceptible,  and  has  no  articuhir  facet.  In  the  Sheep  and  Goat,  the  sternal  ribs  are  consolidated 
with  the  cartilages  (Figs.  6.  7). 

The  Camel  has  eight  sternal  and  four  asternal  ribs.  The  rib.s  increase  in  length  to  the 
tenth,  and  in  width  to  the  si.xth  only.  They  are  less  curved  and  are  shorter,  proportionately, 
tiian  those  of  the  Ox,  the  shortness  being  very  marked  in  the  first  three.  The  tubercle  is  less 
de'achefl  than  in  the  Ox,  but  the  neck  is  longer  and  stronger  (Fig.  8). 

B.  Pig. — In  this  animal  there  are  fourteen  pairs  of  ribs,  seven  of  which  are  sternal  and 
seven  asternal.  The  first  are  provided  with  cartilages  of  prolongment  flattened  on  both  sides, 
extremely  wide  and  sharp,  and  convex  on  their  superior  border.  In  the  four  last  asternal  ribs, 
the  fitcet  of  their  tuberosity  is  confoundi'd  with  the  posterior  facet  of  the  head  (Fig.  3). 

C.  Carnivora. — They  possess  thirteen  ribs  on  each  side — nine  sternal  an.l  four  asternal. 
These  are  very  much  arched,  narrow,  and  thick,  and  their  cartilages  rarely  ossify.  In  the  Dog, 
the  articular  facet  of  tiie  tuberosity  remains  isolated  from  the  posterior  facet  of  the  head  in  all 
the  ribs.     It  is  absent  in  the  three  last  ribs  of  the  Cat  (Fig.  2). 

The  Thorax  in  General. 

The  description  of  the  interior  of  the  thoracic  cavity  will  be  referred  to  when 
treating  of  the  respiratory  apparatus.     It  is  only  necessary  here  to  examine  the 


THE  THORAX. 


97 


Fig.  58. 


external  surface  of  this  bony  ca^e.  For  this  purpose  it  is  divided  into  six 
regions — a  superior  plane,  an  inferior  plane,  tivo  lateral  pla7ies,  a  base,  and  a 
summit. 

Planes. — The  superior  plane  is  separated  into  two  portions  bj  the  spinous 
processes  of  the  dorsal  vertebra  ;  each  forms,  with  these  spinous  processes,  the 
costo-vertebral  furrow,  intended  to  lodge  the  majority  of  the  muscles  belonging 
to  the  spinal  region  of  the  back  and  loins.  The  inferior  plane,  less  extensive 
than  the  preceding,  offers  :  1.  On  the  median  line,  the  cariuiform  and  xiphoid 
cartilages  of  the  sternum  ;  2.  On  the  sides,  the  chondro-sternal  articulations, 
and  the  cartilages  of  prolongment  of  the  true  ribs.  The  lateral  planes  are  con- 
vex and  wider  at  their  middle  part  than  in  front  or  behind,  and  exhibit  the 
intercostal  spaces.  They  serve  to  give  support,  anteriorly,  to  the  superior 
segments  of  the  two  anterior  limbs. 

Base. — This  is  circumscribed  by  the  posterior  border  of  the  last  rib,  and  by 
the  cartilages  of  all  the  asternal  ribs  ;  it  is  cut  ouliquely  downwards  and  for- 
wards, and  gives  attachment,  by  its  internal 
circumference,  to  the  diaphragm — a  muscle 
which  separates  the  thoracic  from  the  ab- 
dominal cavity. 

Summit. — It  occupies  the  anterior  por- 
tion of  the  thorax,  and  presents  an  oval 
opening,  elongated  vertically,  situated  be- 
tween the  two  first  ribs.  This  opening 
constitutes  the  entrance  to  the  chest,  and 
gives  admission  to  the  trachea,  the  oeso- 
phagus, and  important  vessels  and  nerves. 

Comparison  of  the  Thorax  of  Man  with 

THAT   OF   THE    DOMESTICATKD   AnIMALS. 

1.  Sternum. 
The  sternum  of  Man  is  flattened  before  and 
behind,  and  diminishes  in  widtii  from  above  to  be- 
low. The  xiplioid  ap[)endage  is  narrow,  and  single 
or  bifid.  Besides  the  articular  surfaces  for  the  ribs, 
there  are  found  on  the  upper  end  two  lateral 
notches  for  articulation  with  the  clavicles. 


2.  Ribs. 
Of  the  twelve  ribs  in  Man,  seven  are  eternals 
and  five  asternals.  They  are  short,  narrow,  and 
much  incurvated,  especially  the  first  ones.  In  each 
rib  the  curvature  is  more  marked  in  the  posterior 
fourth  or  fifth,  than  in  the  anterior  three-fourths 
or  four-fifths ;  this  sudden  change  of  curvature  is 
indicated  in  the  external  face  by  a  kind  of  inflection 
and  thickening,  called  tlie  angle  of  the  ribs.  The 
prolonging  cartilages  of  the  eleventh  and  twelfth 
ribs  are  short,  and  are  lost  in  the  substance  of  the 
are  termed  ihe  floating  {or  false)  ribs  (Fig.  58> 


thorax  op  man  (anterior  face). 
1,  Superior  piece  of  the  sternum  ;  2, 
middle  piece,  or  body ;  3,  inferior  piece, 
or  ensiform  cartilage;  4,  first  dorsal 
vertebra ;  5,  hist  dor.^al  vertebra  ;  6, 
first  rib ;  7,  its  head  ;  8,  its  neck,  rest- 
ing against  the  transverse  process  of  the 
first  dorsal  vertebra ;  9,  its  tubercle ; 
10,  seventh,  or  last  true  rib  ;  11,  costal 
cartilages  of  the  true  ribs  ;  12,  the  last 
two  false  or  floating  ribs  ;  13,  the  groove 
along  the  lower  border  of  the  rib. 

abdominal  parietes  ;  for  this  reason  they 


Article  IV. — Anterior  Limbs. 

The  anterior  ( pectoral  or  thoracic)  limb  is  divided  into  four  secondary  regions — 
the  shoulder,  arm,  forearm,  and  fore  foot  or  hand. 


98  THE  BONES. 

SHOULDER. 

In  Solipeds,  this  region  has  for  its  base  a  single  bone — the  scapula  or  omoplat. 
^^  Scapula  (Figs.  59,  60). 

This  islW»^  triangular,  and  asymmetrical  bone,  prolonged  at  its  superior 
border  by  a  flexible  cartilage,  articulated  interiorly  with  the  humerus  only,  and 
applied  against  the  lateral  plane  of  the  thorax  in  an  oblique  direction  downwards 
and  forwards.     It  has  two  faces,  three  borders,  and  three  angles. 

Faces. — The  external  face  (or  dorsum)  is  divided  by  the  scapidar  or  acroynian 
spine,  into  two  cavities  of  unequal  width — the  supra-  and  infra-spinous  (or  antea 
and  2)ostea  spinatus)  fosscB.  The  spine  is  a  very  salient  crest  which  runs  the  whole 
length  of  the  external  scapular  surface  ;  very  elevated  in  its  middle  part,  which 
shows  an  irregular  enlargement — the  tuberosity  of  the  spine — it  insensibly  decreases 
towards  its  two  extremities.  The  supraspinous  fossa — the  narrowest — is  situated 
above,  or  rather  in  front  of  the  spine  ;  it  is  regularly  concave  from  side  to  side, 
and  perfectly  smooth.  The  infra-spinous  fossa  is  twice  the  width  of  the  preceding, 
and  occupies  all  the  surface  behind  the  spine.  It  exhibits  :  1.  Below,  and  near 
the  posterior  border,  several  rows  of  roughened  lines  for  muscular  insertion. 
2.  Near  the  neck,  the  nutritient  foramen  of  the  bone,  and  some  vascular  grooves. 

The  interned  face  is  excavated  in  its  centre  to  form  a  hollow,  called  the  subsca- 
pular fossa,  which  is  prolonged  superiorly  by  three  diverging  points.  The  median 
point  extends  to  the  superior  border  of  the  bone,  and  separates  two  roughened 
triangular  surfaces. 

Borders. — The  superior  is  indented  by  an  irregular  groove,  to  receive  the 
inferior  margin  of  the  cartilage  of  prolongation.  The  latter  is  convex  on  its 
superior  border,  extends  beyond  the  posterior  angle  of  the  bone,  and  gradually 
diminishes  in  thickness  as  it  leaves  its  point  of  attachment.  In  old  horses  it  is 
nearly  always  found  partially  ossified.  The  anterior  border,  thin  and  sharp,  is 
convex  in  its  superior  two-thirds,  and  slightly  concave  for  the  remainder  of  its 
extent.     The  posterior  is  thicker  and  a  little  concave. 

Angles. — The  anterior,  or  cerviccd  angle,  is  the  thinnest  of  the  three.  The 
posterior  or  dorsal  angle  is  thick  and  tuberous.  The  inferior,  or  humeral  angle,  is 
the  most  voluminous,  and  is  separated  from  the  remainder  of  the  bone  by  a 
slight  constriction,  which  constitutes  the  neck  of  the  scapula.  It  exhibits  :  1.  The 
glenoid  cavity — an  oval  diarthrodial  surface,  excavated  to  a  slight  extent  to  receive 
the  head  of  the  humerus,  nbtched  on  the  inner  side,  and  bearing  on  the  external 
margin  of  the  ridge  which  surrounds  it  a  small  tubercle  of  insertion.  2.  The 
coracoid  process,  situated  in  front,  and  at  a  certain  distance  from  the  glenoid 
cavity.  This  is  a  large  eminence  in  which  may  be  distinguished  two  parts  :  the 
base,  a  thick  rugged  process  ;  and  the  summit,  a  kind  of  beak  curved  inwards. 

Structure  and  development. — Like  all  the  flat  bones,  the  scapula  is  formed  of 
two  compact  layers  separated  by  spongy  tissue.  The  latter  is  very  scanty 
towards  the  middle  of  the  supra-  and  infra-spinous  fossfe,  where  it  is  often  alto- 
gether wanting  ;  it  is  most  abundant  in  the  angles.  In  Solipeds  and  Ruminants, 
the  scapula  is  developed  from  two  principal  centres  of  ossification,  one  of  which 
forms  the  coracoid  process. 

In  the  Carnivora,  the  cartilage  of  prolongation  is  replaced  by  an  epiphysary 
lip.  It  may  be  added  that  in  Mammaha,  Meckel,  Cuvier,  and  Strauss-Durckheim 
have  noted  a  supplementary  nucleus  in  the  glenoid  cavity  ;  and  that  Lavocat 
and  Goubaux  have  observed  it  in  Horses  especially.     Lavocat  has  described  it  as 


THE  ANTERIOR  LIMBS.  99 

a  pyramidal  nucleus,  base  inferior,  and  flattened  before  and  behind.  In  the 
Horse,  it  appears  at  the  centre  of  the  cavity  towards  the  seventh  or  eighth  month  ; 
it  increases  and  pushes  forward  the  coracoid  process  beyond  the  articular  sur- 
face. In  about  nine  or  ten  months  it  is  fused  with  the  principal  part  of  the  bone, 
and  in  about  a  year  with  the  coracoid  nucleus.     In  the  Ass  and  Mule,  the  glenoid 


Fig.  59. 


Fig.  60. 


SCAPULA  OF  THE  HORSE  (EXTERNAL  FACE).  1,  Subscapular  fossa ;  2,  anterior  triangular 

1,  Tuberosity  of  the  spine  ;  2,  supra-spinous  f  ^face  ;   3    posterior  triangular  surface  ; 

fossa ;  3,  infra-spinous  fossa ;  4,  nutrient  *'  *'  vascular  furrow  ;  5,  glenoid  cavity ; 

foramen;  5,  5,  5,  linear  imprints  for  the  ^   base  of  the  coracoid  process  (insertion 

insertion    of    the    coraco-humeralis ;     6,  of  the  coraco-humeralis). 

tubercle  for  the  same ;  7,    border  of  the 

glenoid  cavity ;    8,   coracoid    process ;    9, 

cervical    angle;     10,    dorsal    angle;    11, 

cartilage  of  prolongation. 

nucleus  appears  about  the  fourth  month,  and  its  evolution  is  completed  at  the 
seventh  or  eighth  month. 

In  the  Ass,  the  scapula  is  usually  more  curved  than  in  the  Horse,  while  the 
greater  development  of  its  superior  border,  and  the  more  considerable  constric- 
tion of  its  neck,  give  it  a  peculiar  appearance.     It  represents  a  wider  and  shorter 


]00 


TEE  BOXES. 


triangle  than  in  the  Horse,  and  the  spine  gradually  decreases  from  the  tuberosity 
until  it  is  nearly  lost  on  the  surface  of  the  bone,  towards  the  nutrient  foramen. 
In  the  Horse,  this  subsidence  of  the  spine  occurs  at  the  neck,  where  it  takes, 
place  quite  suddenly  ;  so  that  it  forms  a  more  or  less  marked  prominence. 

The  scapula  of  the  Hinny  has  the  general  form  of  that  of  the  Ass  ;  in  the 
Mule,  on  the  contrary,  it  is  elongated  Kke  that  of  the  Horse. 

Differential  Characters  in  the  Scapula  of  other  Animals. 

The  shoulder  is  composed  of  one  or  two  bones,  according  as  the  limb  is  intended  exclu- 
sivelj'  to  support  the  body,  or  is  required  for  other  purposes. 

A.  Ox,  Sheep,  Goat.— In  these  animals  the  shoulder  comprises  only  one  bone— the 
scapula— which  is  more  regularly  triangular  than  in  the  Horse.  The  spine  does  not  diminish 
in  passing  to  the  neck,  but,  on  the  contrary,  terminates  at  a  certain  distance  above  the  glenoid 

Fig.  61. 


R  A 

scapula  of  the  cat  and  rabbit. 

A,  Scapula  of  the  Cat.     B,  Scapula  of  the  Rabbit.     1,  Inferior  extremity  of  the  acromian  spine  v 

2,  supra-spinous  fossa;  3,  infra-spinous  process;  4,  superior  border. 

cavity  by  an  abrupt  ridge  prolonged  to  a  point,  which  represents  a  rudimentary  acromion  pro- 
cess. It  divides  the  external  surfnce  of  the  bone  into  two  fossse,  which  in  extent  are  as  1 :3. 
The  neck  is  more  constricted,  and  the  humeral  angle  better  detached,  than  in  Solipeds. 

B.  Camel. — The  scapula  of  this  animal  resembles  that  of  the  Ox  in  its  general  form,  but 
the  spine  divides  the  face  into  two  equal  fossae.  The  acromion  process  descends  to  the  glenoid 
cavity. 

C.  Pig. — The  .spine,  depressed  at  its  two  extremities,  rises  considerably  at  its  middle  por- 
tion, and  bends  over  towards  the  infra-spinous  process. 

D.  Camivora.— Their  shoulder  has  two  bones  — the  scapula  and  clavicle.  In  the  Dog , 
the  latter  is  little  more  than  a  shell  embedded  in  the  muscles  in  front  of  the  scapulo-humerul 
angle ;  in  the  Cat,  it  constitutes  a  small  styloid  bone  which  is  united  to  the  acromion  process 
and  the  sternum  through  the  medium  of  two  ligaments.  The  scapula  has  no  cartilay;e  of  pro- 
longation ;  its  anterior  border  is  very  convex,  as  if  it  had  been  curved  over  on  itself.  The  fos.'ife 
of  the  external  face  are  equal,  and  the  spine  terminates  in  an  acromion  process  that  reaches  the 
glenoid  cavity. 

E  Rabbit. — Two  bones  form  the  shoulder  of  this  animal.  The  clavicle,  although  longer 
than  that  of  the  Cat.  nevertheless  does  not  rest  directly  on  the  sternum  and  scapula.  The 
latter  is  in  shape  regularly  triangular;  the  neck  is  slender;  the  fos^sse  on  the  external  face 
are  very  unequal  ;  the  spine  is  prolonged  by  a  thin  acromion  pedicle  to  the  vicinity  of  the 
glenoid  cavity ;  and  the  superior  border  of  the  bone  is  [irovided  with  a  cartilage  of  prolongation. 


TEE  ANTERIOR   LIMBS. 


101 


Arm. 


Fig.  62. 


This  region  has  only  one  bone,  the  humerus. 

Humerus  (Figs.  62,  63). 

The  humerus  is  a  long  single  bone,  situated  between  the  scapula  and  the  bone 
of  the  forearm,  in  an  oblique  direction  downwards  and  backwards.  Like  all  the 
long  bones,  it  offers  for  study  a  bodt/  and  two  extremities. 

Body. — The  body  of  the  humerus  looks  as  if  it  had  been  twisted  on  itself  from 
within  to  without  in  its  superior  extremity,  and  from 
without  to  within  at  the  opposite  end.  It  is  irregularly 
prismatic,  and  is  divided  into  four  faces.  The  anterior 
face  (Fig.  62),  wider  above  than  below,  has  in  its  middle 
and  inferior  portions  some  muscular  imprints.  The  pos- 
terior, smooth  and  rounded  from  one  side  to  the  other, 
"becomes  insensibly  confounded  with  the  neighbouring 
faces.  The  external  is  excavated  by  a  wide  furrow,  which 
entirely  occupies  it,  and  turns  round  the  bone  obliquely 
from  above  to  below  and  behind  to  before  ;  it  is  to  the 
presence  of  this  channel  that  the  humerus  owes  its  ap- 
parent twist,  and  it  is  in  consequence  designated  the /?/rrow 
of  torsion  (or  inusculo-spiral  groove)  of  the  body  of  the 
humerus. 

This  furrow  is  separated  from  the  anterior  face  by 
a  salient  border — the  deltoid  ridge,  which  ends  inferiorly 
above  the  coronoid  fossa,  and  superiorly,  towards  the 
upper  third  of  the  bone,  by  the  imprint,  or  deltoid  (or 
external)  tuberosity.  This  is  a  roughened,  very  prominent 
eminence,  flattened  before  and  behind,  and  inclining  to- 
wards the  furrow  of  torsion  ;  by  its  superior  extremity, 
it  gives  origin  to  a  curved  line  which  is  carried  backwards 
to  join  the  base  of  the  articular  head.  Near  the  inferior 
extremity,  backwards  and  outwards,  is  seen  the  posterior 
deltoid  ridge,  which  separates  the  latter  from  the  posterior 
face  of  the  bone.  The  internal  face  of  the  body  of  the 
humerus,  rounded  from  side  to  side,  is  not  separated  from 
the  anterior  and  posterior  faces  by  any  marked  line  of 
demarcation.  It  offers,  near  its  middle,  a  depressed 
scabrous  process  (the  internal  tuberosity)  for  the  insertion  of 
the  teres  major  and  latissimus  dorsi  muscles.  Towards  its 
inferior  third  it  shows  the  nutrient  foramen  of  the  bone. 

Extremities. — These  are  distinguished  into  superior  and 
inferior.     Both  are  slightly  curved — the  first  backwards, 
the  second  forwards— a  disposition  which  tends  to  give  to  the  humerus  the  form 
of  an  S. 

The  superior  extremity  is  the  most  voluminous,  and  has  three  thick  eminences — 
a  posterior,  external,  and  internal.  The  first  constitutes  the  head  of  the  humerus. 
It  is  a  very  slightly  detached  articular  eminence,  rounded  like  the  segment  of  a 
sphere,  and  corresponding  with  the  glenoid  cavity  of  the  scapula,  which  is  too 
«mall  to  receive  it  entirely.     The  external  eminence — named  the  trochiter,  large 


ANTERO-EXTERNAL  VIEW 
OF    RIGHT    HUMERUS. 

1,  Trochlear  or  bicipital 
ridges ;  2,  external  or 
deltoid  tuberosity  ;  3, 
head  or  articular  sur- 
face ;  4,  external  tuber- 
cle ;  5,  shaft  or  body 
with  its  twisted  fur- 
row; 6,  7,  articular  or 
trochlear  condyles;  8, 
uluar  fossa  with  a  sul- 
cus; 9,  fossa  for  the 
insertion  of  the  exter- 
nal lateral  ligament. 


102 


THE  BONES. 


Fig.  63. 


(or  external)  trochanter,  and  great  fuberositi/—corm[>Y[ses  three  portions,  named 
the  summit,  convexitij,  and  crest  of  the  great  tuberosity.  The  internal  eminence — 
the  trochin,  little  (or  interned)  trochanter,  or  small  tuherosity — also  presents  three 
distinct  portions,  which,  by  their  position,  correspond  exactly  with  the  three  regions 
of  the  external  trochanter  ;  these  are  so  many  muscular  facets. 

The  external  and  internal  trochanters  are  separated  from  each  other  in  front 
by  a  channel  called  the  bicipital  groove,  because  the  superior 
tendon  of  the  biceps  muscle  glides  over  it.  It  consists  of 
two  vertical  grooves,  with  a  median  ridge  between  them. 

The  inferior  extremity  of  the  humerus  has  an  articular 
surface  corresponding  with  the  radius  and  ulna.  This  sur- 
face— elongated  transversely,  convex  from  before  backwards, 
and  of  greater  extent  within  than  without — exhibits  two- 
trochlea  separated  by  an  antero-posterior  relief. 

The  median  or  interned  trochlea,  the  deepest,  is  limited 
internally  by  a  kind  of  voluminous  condyle,  which  corre- 
sponds to  the  inner  lip  of  the  humeral  trochlea  of  Man. 
The  external  trochlea  is  bordered  outwardly  by  a  slightly 
salient  lip,  which  corresponds  to  the  condyle  of  the  humerus 
of  Man.  Above  and  behind  this  articular  surface  is  a  wide 
deep  fossa — the  olecranian  (or  condyloid),  so  named  because 
it  lodges  the  rostrom  of  the  olecranon  in  the  extension  move- 
ments of  the  forearm.  It  is  bordered  by  two  eminences, 
the  external  of  which  is  less  elevated  than  the  internal.  The 
first  represents  the  epitrochlea,  and  the  second  the  epicondyle, 
of  the  humerus  of  Man.  In  front,  and  above  the  inner 
trochlea,  there  is  another,  but  less  spacious  fossa,  which 
receives  the  coronoid  process  during  extreme  flexion  of  the 
forearm,  and  which,  for  this  reason,  it  would  be  convenient 
to  designate  as  the  coronoid  fossa.  Always  in  front,  but 
above  the  external  trochlea,  are  imprints  for  the  attach- 
ment of  the  capsular  ligament  of  the  elbow- joint  and  the- 
extensor  metacarpi  magnus.  Lastly,  at  the  extremities 
of  the  transverse  axis  of  the  inferior  articular  surface  is 
remarked,  outwardly, an  excavation  for  ligamentous  insertion; 
inwardly,  a  small  tuberosity  for  the  same  purpose. 
Structure  and  development. — The  humerus,  like  all  the  long  bones,  is  only 
spongy  at  its  extremities.  It  is  developed  from  six  points  of  ossification,  one  of 
which  alone  forms  the  body,  one  the  head  and  the  internal  trochanter,  another  the- 
external  trochanter,  a  fourth  the  inferior  articular  surface,  a  fifth  the  epicondyle, 
and  the  last  for  the  epitrochlea.  The  latter  is  sometimes  absent.  In  the  young 
animal  the  humerus  is  less  twisted,  and  the  eminences  for  muscular  insertion  less 
developed,  than  in  the  adult. 

In  the  Ass,  the  humerus  is  more  twisted  and  curved  in  S  form  than  in  that 
of  the  Horse,  and  these  modifications  replace  the  eminences  on  this  bone  in  the 
latter.  Consequently,  the  equilibrium  of  the  humerus  is  altered  when  it  lies  on  a 
horizontal  plane  by  any  one  of  its  faces  and  its  lower  extremity.  Thus,  while  the 
humerus  of  the  Ass  may  rest  in  equilibrium  on  a  plane — its  trochlea  and  two  other 
points  of  its  anterior  face  touching  it — the  Horse's  humerus  can  only  do  so  when 
the  condyle,  trochlea,  and  one  or  two  points  of  its  superior  extremity  touch  it.. 


POSTERIOR  VIEW  OF  THE 
RIGHT    HUMERUS. 

2,  External  trochanter; 
3,  articular  head  of 
the  bone;  4,  external 
tubercle  and  ridge  ; 
5,  body  or  shaft  of 
the  bone  ;  10,  condy- 
loid fossa. 


THE  ANTERIOR  LIMBS. 


103 


Fig.  64. 


Laid  on  its  posterior  face,  the  humerus  of  the  Ass  is  in  unstable  equiUbrium,  if  it 
has  to  touch  the  plane  by  the  epicondyle  and  epitrochlea  ;  this  is  not  so  with  the 
humerus  of  the  Horse.  If  it  is  placed  on  its  external  side,  the  deltoid  imprint 
remains  above  the  horizontal  plane  with  the  Ass,  and  touches  it  with  the  Horse. 
Lastly,  the  epitrochlea  descends  nearly  to  the  articular  surface  in  the  Ass,  so  that 
the  bone  is  almost  in  equilibrium  when  it  is  placed  on  its  inferior  extremity. 

The  humerus  of  the  Mule  and  Hinny  resembles  that  of  their  parents,  but 
that  of  the  Hinny  is  more  like  the  Ass's,  and  that  of  the  Mule  the  Horse's. 

Differential  Characters  in  the  Humerus  of  other  Animals. 

Proportiot)ately,  the  Immeius  is  longer,  ami  more  inflected  like  an  S,  as  the  number  of 
apparent  digits  is  increased.  Therefore  it  is  that,  in  the  C.irnivora,  the  characters  of  length 
and  inflection  are  most  marked. 

A.  Ox,  Sheep,  Goat.— In  these  animals,  the  furrow  of  torsion  is  less  marked,  and  the 
deltoid  imprint  less  salient  than  in  the  Horse,  while 

the  extremities  are  larger  and  more  curved.  The 
bicipital  groove  is  divided  into  two  depressions  by 
a  median  ridge ;  the  external  trochanter  is  enormous, 
and  its  very  elevated  summit  is  bent  over  the 
bicipital  groove.  Tlie  head  is  better  detitched  and 
the  trochlea  deeper  than  in  the  Horse.  The  medul- 
lary eanal  of  the  humerus  of  the  Ox  is  sometimes 
crossed  by  an  osseous  band. 

B.  Camel. — Humerus  cylindrical  and  nearly 
straight.  Torsion  furrow  shallow  ;  nutrient  foramen 
on  its  anterior  face.  Bicipital  groove  double,  the 
inner  cavity  being  larger  than  the  external.  The 
inferior  articular  surface  is  relatively  very  narrow, 
and  the  external  trochlea  deep. 

C.  Pig. — The  humerus  of  this  animal  is  com- 
pressed on  both  sides;  the  head  is  much  bent  back- 
wards, which  increases  its  S  inflection.  A  single 
bicipital  groove  placed  within  the  superior  extremity ; 
the  external  trochanter  voluminous,  and  the  summit 
turned  over  the  bicipital  groove.  Deltoid  imprint 
and  internal  tuberosity  of  the  body  replaced  by 
simple  muscular  imprints. 

D.  Dog  and  Cat. — The  humerus  is  very  elon- 
gated and  more  S-curved  than  in  all  the  other 
animals,  and  the  internal  tuberosity  is  leplaced  by 
some  imprints  ;  while  the  bicipital  groove  is  single, 
and  the  nutrient  foramen,  on  the  posterior  face,  is  as 
in  the  Ox,  Sheep,  and  Pig.  The  coronoid  fossa  com- 
municates with  that  of  the  olecranon  by  a  foramen. 

E.  Rabbit. — The  humerus  of  this  animal  greatly 
resembles  that  of  the  Dog,  except  that  it  is  much 
more  flattened  on  each  side,  and  the  deltoid  imprint 
is  on  the  anterior  face  and  nutrient  foramen  on  the 
inner  lace  of  the  bone. 

Forearm. 

This  region  has  for  its  base  two  bones — ^the  radius  and  mtitus  (or  vino), 
united  into  a  single  piece  {os  aniihrachii)  at  an  early  period  in  most  of  the 
domesticated  animals. 


HUMERUS   OF   THE   CAT   AND   RABBIT. 

,  Humerus  of  the  Rabbit.  B,  Humerus  of 
the  Cat.  1,  Condyle;  2,  trochlea;  3, 
diaphysis  ;  4,  external  trochanter ;  5, 
internal  trochanter ;  6,  bicipital  groove. 


1.  Radius  (Figs.  65,  66). 

This  is  a  long  bone,  placed  in  a  vertical  direction  between  the  humerus  and 
the  first  row  of  carpal  bones,  and  divided  into  a  body  and  two  extremities. 


104 


THE  BONES. 


Body. — Slightly  arched  and  flattened  before  and  behind,  it  presents  for  study 
two  faces  and  two  borders.  The  anterior  face  is  convex  and  perfectly  smooth.  The 
posterior,  a  little  concave  from  one  extremity  to  the  other,  offers  :  1.  Near  the 
external  border,  a  triangular  surface,  covered  with  asperities,  elongated  vertically, 
very  narrow,  commencing  near  the  upper  fourth  of  the  bone,  and  terminating  in 
a  fine  point  towards  the  lower  fourth  ;  this  surface  is  brought  into  contact  with 
the  anterior  face  of  the  ulna  by  an  interosseous  liga- 
^^S-  65.  ment,  which  is  completely  ossilied  before  the  animal 

-^'''  reaches  adult  age.     2.  Above,  there  is  a  wide,  trans- 

verse, but  shallow  groove,  which  aids  in  forming  the 
radio-ulnar  arch,  and  shows,  near  the  point  where  it 
touches  the  preceding  surface,  the  nutrient  foramen  of 
the  bone.  3.  Near  the  internal  border,  and  towards  the 
inferior  third,  there  is  a  vertically  elongated  and  slightly 
salient  eminence  for  insertion.  The  two  borders — external 
and  internal — are  thick  and  rounded  ;  they  establish  an 
insensible  transition  between  the  faces. 

Extremities. — The  superior  is  larger  than  the  inferior. 
It  has  :  1.  An  articular  surface  elongated  from  one  side 
to  the  other,  concave  from  before  to  behind,  wider 
within  than  without,  and  moulded  to  the  articular  sur- 
face of  the  inferior  extremity  of  the  humerus  ;  there 
is  also  seen,  outwardly,  a  double  depression  (glenoid 
cavities),  which  receives  the  two  lips  of  the  external 
trochlea ;  in  the  middle,  an  antero-posterior  ridge, 
which  is  received  into  the  internal  trochlea  ;  within, 
an  oval  cavity  corresponding  to  the  internal  border 
of  the  former.  2.  The  external  tuberosity,  placed  at 
the  extremity  of  the  great  diameter  of  the  articular 
surface  ;  it  is  prominent  and  well  detached.  3.  The 
interned  or  bicipital  tuberosity — a  large,  very  rugged,  and 
depressed  process,  situated  within  and  in  front  of  the 
glenoid  cavity.  4.  A  little  lower,  and  on  the  same  side, 
there  is  a  strong  muscular  and  ligamentous  imprint, 
separated  from  the  preceding  tuberosity  by  a  transverse 
1,  Ulna;  2,  point  of  the  groove  intended  for  the  passage  of  a  tendon.  .5.  The 
coronoid  process,^  a  small  conical  eminence,  at  the 
summit  of  which  terminates,  anteriorly,  the  median 
ridge  of  the  articular  surface.  (3.  Two  diathrodial 
facets  elongated  transversely,  cut  on  the  posterior  outline 
of  the  large  articular  surface,  with  which  they  are  con- 
founded by  their  superior  border  ;  they  correspond  with 
similar  facets  on  the  ulna.  7.  Below  these,  a  roughened 
surface  which  extends  to  the  radio-ulnar  arch,  and  is  in  contact  with  an  analogous 
surface  of  the  same  bone  through  the  medium  of  an  interosseous  ligament.  In 
the  Horse,  this  hgament  rarely  becomes  ossified. 

The  inferior  extremity,  flattened  before  and  behind,  presents  :  1.  Inferiorly,  an 
articular  surface  elongated  transversely  and  somewhat  irregular,  responding  to 
the  four  bones  in  the  upper  row  of  the  carpus.     2.  On  the  sides,  two  tuberosities 
*  In  Man  this  belongs  to  the  ulna. 


EXTERNAL  FACE  OF  THE 
RADIUS  AND  ULNA. 

Ulna;  2,  point  of  the 
ulna;  3,  beak  of  ulna  or 
olecranon  ;  4,  radio-ulnar 
arch ;  5,  supero-external 
tuberosity;  6,  radio-ulnar 
articular  surfaces  for  the 
humerus;  7,  bicipital  tu- 
b  rosity  ;  8,  shaft  or  body 
of  the  radius  ;  9,  grooves 
for  tendons. 


THE  ANTERIOR   LIMBS.  105 

for  ligamentous  insertion — the  internal  salient  and  well  circumscribed,  the  other 
external,  and  excavated  by  a  vertical  fissure — in  which  passes  a  tendon.  3.  In 
front,  three  grooves  for  the  gliding  of  tendons  ;  the  external  is  the  largest, 
and  vertical  like  the  median  ;  the  internal,  the  narrowest,  is  oblique  downwards 
and  inwards.  4.  Posteriorly,  a  strong  transverse  ridge  which  surmounts  the 
articular  surface,  and  serves  for  the  insertion  of  ligaments. 

Structure  and  development.— The  radius  is  a  very  compact  bone,  and  is 
developed  from  three  centres  of  ossification — one  for  the  body,  and  two  for  the 
extremities. 

2.  Ulna  (Figs.  65,  66). 

This  is  an  elongated,  asymmetrical  bone,  in  the  form  of  an  inverted  triangular 
pyramid,  applied  against  the  posterior  face  of  the  radius,  to  which  it  is  united 
in  adult  Solipeds.     It  offers  for  description  a  middle  portion  and  two  extremities. 

Middle  portion. — This  has  three  faces  wider  above  than  below,  and  three 
borders  which  become  joined  at  the  inferior  extremity  of  the  bone.  The  external 
face  is  smooth  and  nearly  plane.  The  internal  is  also  smooth  and  shghtly 
hollowed.  The  anterior  is  formed  to  correspond  with  the  radius,  and  presents 
pecuharities  analogous  to  those  of  the  posterior  face  of  that  bone.  Thus,  there 
is  found,  in  proceeding  from  above  to  below  :  1.  Two  small  diarthrodial  facets.^ 
2.  A  roughened  surface.  3.  A  transverse  groove  for  the  formation  of  the  radio- 
ulnar arch.  4.  A  triangular  surface,  studded  with  rugosities,  which  occupie^the 
remainder  of  the  bone  to  its  lower  extremity.  The  lateral  borders — externatand 
internal — are  sharp,  and,  like  the  anterior  face,  are  in  contact  with  the  radius. 
The  posterior  border  is  concave,  rounded,  and  thicker  than  the  other  two. 

Extremities. — The  superior  extremity  comprises  all  that  portion  which  exceeds 
the  articular  surface  of  the  radius.  It  constitutes  an  enormous  process — the 
olecranon — flattened  on  both  sides,  and  presenting  :  1.  An  external  face,  slightly 
convex.  2.  An  internal  excavated  face.  3.  An  anterior  border,  thin  and  sharp 
superiorly,  notched  below  to  form  the  sigmoid  cavity^ — an  articular  surface 
concave  from  above  downwards,  rounded  from  one  side  to  the  other,  which 
corresponds  with  the  humeral  cavity,  and  is  surmounted  by  a  salient  prolongation 
named  the  bectk  of  the  olecranon.  4.  A  concave  and  smooth  posterior  border.  5. 
The  summit — a  kind  of  thick  roughened  tuberosity  which  terminates  the  uhia 
above,  and  into  which  are  inserted  the  extensor  muscles  of  the  forearm. 

At  its  inferior  extremity,  the  ulna  ends,  towards  the  lower  fourth  of  the 
principal  portion  of  the  forearm,  in  an  acute  point,  and  sometimes  by  a  small 
knob  (capitulum  ulnce).  It  is  not  rare  to  see  it  prolonged,  especially  in  the  Ass 
and  Mule,  to  the  inferior  external  tuberosity  of  the  radius.  This  tuberosity  then 
appears  to  belong  to  it,  at  least  in  part  ;  and  all  that  portion  which  is  situated 
behind  its  vertical  groove  might  be  justly  considered  as  a  dependency  of  the 
uhia. 

Structure  and  development. — The  ulna  contains  much  compact  tissue,  even  in 
the  region  of  the  olecranon  ;  it  is  also  very  solid.  It  is  an  imperfect  bone, 
developed  from  two  centres  of  ossification  only,  one  of  these  being  for  the  apex 
of  the  olecranon. 

In  the  Ass  (Fig.  66),  the  radius  is  more  curved  than  in  the  Horse,  and  when 
its  anterior  face  is  placed  on  a  horizontal  plane,  the  bone  only  rests  on  its  upper 

'  Tlv  smaller  siqmmrl  cavity  of  Man. 
*  'The  qreater  f^iijinoid  en  vity  of  Man. 


106 


THE  BONES. 


end  and  the  middle  of  the  body.     It  is  also  distinguished  from  that  of  the  Horse 
by  the  depth  of  a  narrow  groove,  which  passes  through  the  rough  lip  above  and 
behind  the  inferior  surface,  superior  to  the  small  fossa 
F'g-  66.  that  receives  the  third  bone  of  the  upper  row  of  the 

carpus  during  flexion  and  extension  movements.  The 
ulna  of  this  animal  is  more  developed  than  that  of  the 
Horse,  and  its  olecranon  is  proportionately  shorter, 
broader,  and  more  hollowed  on  its  internal  face.  The 
inferior  extremity  (Fig.  66,  9)  is  nearly  always  formed 
by  a  particular  nucleus,  which  is  also  sometimes  the  case 
in  the  Horse. 

In  the  Hinny,  the  bone  of  the  forearm  resembles 
that  of  the  Ass,  with  the  exception  of  the  smallness  of 
the  lower  end  of  the  ulna. 

Differential  Characters  in  the  Forearm  Bones  of 
OTHER  Animals. 

The  principal  ditferential  characters  that  they  present  are  con- 
nected with  the  relative  dimensions  of  the  two  bones  and  their  mode 
of  union.  Regarding  these,  and  as  generally  applicable,  tlie  follow- 
ing principles  may  be  laid  down  : — 

1 .  The  development  of  the  ulna  is  in  direct  relation  to  the  division 
of  the  foot. — Mouodactylous  animals — such  as  the  Horse,  Ass,  and 
Mule — have,  in  fact,  only  a  rudimentary  ulna.  In  the  pentadacty- 
lous  animals,  on  the  contrary — as  Man,  the  Cat,  Elephant,  etc., — 
this  is  a  veritable  long  bone  which  equals,  or  even  exceeds,  the 
radius  in  volume. 

2.  The  closeness  of  union  between  the  radius  and  ulna  is  in 
increased  proportion  as  the  animal  exchmvely  employs  its  inferior 
extremity  for  standing  and  walking. — Thus,  in  Solipeds  and  Rumi- 
nants, and  Pachyderms  in  general,  the  two  bones  are  consolidated, 
or  at  least  united  by  an  interosseous  ligament,  and  in  so  firm  a 
manner  that  they  can  only  execute  very  obscure  movements  on 
each  other.  The  anterior  limb  of  these  animals  is,  indeed,  only 
used  to  support  the  body  on  the  ground.  In  those,  on  the  contrary, 
which  may  employ  it  to  dig  up  the  soil,  climb  on  trees,  etc.,  or  as 
an  organ  of  preliension,  the  radius  and  ulna  are  merely  joined  at 
their  extremities  by  an  articulation,  which  permits  them  to  move 
upon  one  another  with  the  greatest  facility.  Rodents,  the 
majority  of  the  Caniivora,  and  the  Quadrumana,  are  so  provided  ; 
but  it  is  in  Man  that  the  relative  independence  of  the  two  bones 
is  carried  to  the  highest  degree.  No  animal  can  so  easily  execute 
the  movements  of  pronation  and  supination  of  tiie  hand,  which  are 
determined  by  the  play  of  tlie  two  bones  of  the  forearm  on  each  other. 

To  the  indication  of  these  fundamental  characters,  may  be  added 
some  details  on  a  few  particular  and  important  points. 

A.  Ox,  Sheep,  Goat. — The  forearm  of  the  Ox  is  short; 
that  of  the  Sheep  and  Goat  is  longer  ;  but  in  the  three  species,  the 
ulna— thicker  than  in  the  Horse— is  a  long  bone  developed  from 
three  primary  nuclei.  It  extends  the  whole  length  of  tlie  radius, 
and  concurs  in  forming  the  articular  surface  corresponding  with 
the  carpal  liones. 

The  inferior  articular  surface  is  cut  obliquely  downwards  and 
inwards.  There  are  two  radio-ulnar  arches — a  superior  and  in- 
ferior— united  externally  by  a  deep  fissure.  The  union  of  tlie  two 
bones  is  more  intimate  than  in  the  Horse;  for  ossification  always 
ends  by  invading  that  portion  uf  the  interosseous  ligament  placed 
above  the  superior  vascular  arcli  (Fig.  71). 


forearm   bones  OF   THE 


1,  Diaphysis  of  the  radius; 

2,  bicipital    tuberosity ; 

3,  external  and  superior 
tuberosity  of  the  radius  ; 

4,  groove  for  the  passage 
ot  the  anterior  extensor 
of  the  phalanges  ;  5, 
surface  for  insertion  of 
branch  of  the  perforans 
tendon  ;  6,  body  of  the 
ulna  interrupted  at  its 
lower  third,  but  more 
complete  than  usual  ;  7, 
summit  of  the  olecranon  ; 
8,  beak  of  ditto ;  9,  in- 
ferior extremity  of  ditto ; 
10,  radio-ulnar  arch  ;  11, 
crest  above  the  inferior 
articular  surface  of  the 
radius,  behind. 


THE  ANTERIOR  LIMBS.  107 

B.  Camel. — The  radius  of  this  animal  has  a  narrow,  superior,  articulating  surface  of  two 
glenoid  cavities,  separated  by  a  median  salient  crest  terminating  in  front  by  a  very  marked 
coronoid  process ;  the  bicipital  tuberosity  is  large,  and  on  the  anterior  face.  The  ulna  is  very 
-concave  in  its  middle  part,  and  tlie  olecranon  is  broad  and  low. 

C.  Pig. — The  radius  is  short,  its  inferior  surface  cut  rather  obliquely  as  in  Ruminants,  and 
partly  formed  by  the  inferior  extremity  of  the  ulna,  which  is  a  voluminous  bone  provided  with 
a  medullary  canal,  and  solidly  united  to  the  radius  by  an  interosseous  ligament,  the  complete 
ossification  of  wliich  is  rare.  It  is  flattened  before  and  behind,  and  is  spread  over  the  posterior 
face  of  the  radius,  so  as  nearly  to  completely  cover  it.   The  olecranon  is  very  prominent  (Fig.  7G). 

D.  Dog,  Cat. — The  two  bones  of  the  forearm  are  nearly  equal  in  volume,  and  are  in 
contact  only  by  their  extremities,  where  they  show  for  this  purpose :  1.  Above,  on  the  ulna, 
a  concave  articular  surface — the  small  sigmoid  cavity ;  and  on  the  radius,  a  rounded  hinge-like 
facet.  2.  Below,  two  facets  analogous  to  the  preceding,  but  much  smaller;  that  on  the  radius 
is  concave,  and  that  on  the  ulna  convex.  Tliese  two  bones  slightly  cross  each  other,  so  that  the 
upper  end  of  the  ulna  touches  the  radius  behind  and  inwards,  wliile  the  inferior  terminates 
altogether  outwards.  In  the  Pig  and  Ruminants,  the  lower  end  is  in  contact  with  the  upper 
row  of  carpal  bones  (Fig.  77). 

E.  Kabblt. — The  ulna  is  still  more  developed  than  in  the  Cat,  and  more  curved  length- 
ways. 

The  posterior  border  of  the  olecranon  is  almost  vertical,  instead  of  being  oblique  from 
before  to  behind,  and  the  sigmoid  notch  is  deeper  and  shorter  curved  than  in  the 
Carnivora. 


ANTERIOR  (OR  FORE)  FOOT,  OR  HAND. 

The  anterior  foot,  or  hand,  is  the  region  which  presents  the  greatest  0flfe- 
rences  when  it  is  examined  in  the  various  individuals  of  the  animal  series. 
Nevertheless,  notwithstanding  these  varieties,  its  constitution  is  fundamentally 
the  same,  and  may  be  divided  into  three  sections — ^the  carpus,  metacarpus,  and 
phalangeal  region. 

In  vertebrate  animals,  the  hand  is  composed  of  a  certain  number  of  parallel 
or  quasi-parallel  segments,  which  constitute  the  digits.  Each  complete  digit  is 
subdivided  into  three  sections,  placed  one  above  the  other  ;  these  are,  reckoned 
from  above  to  below — carpus,  metacarpus,  and  phalanges. 

The  number  of  apparent  digits  varies  from  one  to  five  ;  and,  however  it  may 
otherwise  appear,  philosophical  anatomy  has  shown  that  the  hand  of  all  the 
domesticated  animals  may  be  considered  as  belonging  to  the  pentadactylous 
type.  When  it  does  not  appear  to  be  so,  this  is  due  to  more  or  less  numerous 
or  extensive  atrophies  or  abortions  always  occurring  according  to  fixed  laws.  (See 
remarks  hereafter  on  the  Hand  in  General.) 

1.  Caepal  Bones  (Figs.  67,  68,  69). 

The  carpus  (or  'knee')  forms  the  base  of  the  hand.  Situated  between  the 
inferior  extremity  of  the  radius  and  the  superior  extremity  of  the  metacarpal  bones, 
it  is  composed  of  several  small  bones  joined  to  each  other,  in  the  fresh  state,  by 
extremely  solid  articular  bands.  Collectively,  they  form  an  almost  quadrilateral 
mass,  in  which  may  be  distinguished  two  faces  and  four  borders. 

The  anterior  face  is  slightly  convex  from  side  to  side,  and  irregular  ;  it  is 
in  contact  with  the  tendons  of  the  extensor  muscles  of  the  metacarpus  and 
phalanges. 

1h.Q  posterior  face  is  very  unequal,  and  converted — especially  outwardly — into 
a  groove,  in  which  the  tendons  of  the  flexor  muscles  of  the  phalanges  glide. 


108 


THE  BONES. 


Fig.  67. 


The  superior  border  articulates  with  the  radius  ;  the  inferior  border  with  the 
metacarpal  bones. 

The  lateral  borders  are  nearly  flat  ;  above  and  behind  the  external  border  is 
remarked  a  considerable  eminence,  formed  by  the 
bone  which  will  be  hereafter  studied  as  the  super- 
carpal  bene  (pisiform  or  trapezium). 

In  the  carpus  of  the  Horse  are  seven  or  eight 
bones,  which  are  disposed  in  two  superposed  rows. 
The  superior  row  comprises  four  bones  placed  side 
by  side,  and  designated  by  the  numerical  names  of 
Jirst,  second,  third,  and  fourth,  viewing  them  from 
without  to  within.  The  inferior  row  has  only 
three,  which  are  named  in  the  same  manner. 

In  applying  to  them  the  names  proposed  by 
Liser,  we  have,  in  the  upper  row — 

1.  The  pisiform,  or  supercarpal  bone. 

2.  The  cuneiform  bone. 

3.  The  lunar  bone. 

4.  The  scaphoid  bone. 
In  the  inferior  row — 

1.  The  unciform  bone. 

2.  The  magnum  bone. 

3.  The  trapezoid  bone. 

4.  The  trapeziimi  (not  constant). 
The  description  of  these  bones  is  most  simple, 

and  may  be  made  in  a  general  manner  for  all.  Thus, 
with  the  exception  of  the  supercarpal  bone,  they 
are  solid,  nearly  cubical  in  form,  and  exhibit  on 
their  periphery  :  1.  Articular  surfaces.  2.  /Surfaces 
for  insertion. 

The  articular  surfaces  are  small,  flat,  or  slightly 
undulating  facets,  distributed  on  the  superior,  in- 
ferior, and  lateral  faces  ;  none  are  found  in  front 
or  behind.  The  superior  and  inferior  faces  are 
entirely  occupied  by  a  single  facet,  which  responds 
either  to  the  radius,  the  metacarpals,  or  to  the  bones 
of  the  other  row.  The  lateral  facets  are  always 
RIGHT  ANTERIOR  FOOT  OR  HAND    multiplc,  aud  iu  coutact  with  the  bones  of  the  same 


OF   A 


tier ;  they  do  not  exist,  of  course,  on  the  outside 
of  the  bones  at  the  ends  of  each  row. 

The  surfaces  for  insertion  are  absent  on  the 
superior  and  inferior  faces  ;  they  separate,  in  the 
form  of  roughened  depressions,  the  lateral  articular 
facets.  Before  and  behind,  they  are  covered  by 
more  or  less  marked  rugosities. 

Bones  of  the  Upper  or  Antibrachial  Row 
(Figs.  68,  69). — The  first,  or  os  pisiforme,  is  outside 
the  row  ;  it  is  situated  above  and  behind  the  carpus,  whence  its  name  of  super- 
carpal bone,  by  which  it  is  usually  known  in  veterinary  anatomy.  This  bone, 
which  merits  a  special   description,  represents  a  disc  flattened   on  both  sides. 


HORSE. 

1,  Radius;  2,  grooves  for  the  ex- 
tensor of  the  phalanges;  3, 
scaphoid;  4,  lunar;  5,  cunei- 
form ;  6,  pisiform ;  7,  mag- 
num;  8,  unciform ;  9,  great 
metacarpal;  10,  small  meta- 
carpal ;  11,  sesamoid  bone  ;  12, 
suffraginis  ;  13,  coronary;  14, 
navicular;  15,  pedal ;  16,  basi- 
lar process. 


THE  ANTERIOR  LIMBS. 


109 


oflFering  for  study  two  faces  and  a  circumference.  The  external  face  is  convex, 
roughened,  and  channeled  anteriorly  by  a  groove  that  traverses  it  from  above  to 
below,   in   which  glides   the   inferior  tendon    of   the   external    flexor    of   the 


CARPUS   OF   THE   HORSE   (ANTERIOR   FACE). 

1,  Pisiform  or  supercarpal  bone  (first  of  the 
upper  row);  2.  cuneiform  (second  ditto)  ; 
3,  lunar  (third  ditto);  4,  scaphoid  (fourth 
ditto)  ;  5,  unciform  (first  of  lower  row)  ; 
6,  OS  magnum  (second  ditto)  ;  7,  trape- 
zoid (third  ditto) ;  9,  inferior  articular 
face  of  the  radius;  10,  groove  for  the 
oblique  extensor  tendon  of  the  meta- 
carpus; 11,  groove  for  the  anterior  ex- 
tensor of  the  metacarpus;  12,  groove  for 
the  anterior  extensor  of  the  phalanges ; 
13,  superior  extremity  of  the  large  meta- 
carpal bone ;  14,  tubercle  for  the  inser- 
tion of  the  anterior  extensor  of  the  meta- 
carpus ;  15,  superior  extremity  of  the 
external  small  metacarpal  bone. 


CARPUS  OF   THE    HORSE   (POSTERIOR   FACE> 

1,  2,  3,  4,  5,  6,  7,  Same  bones  as  in  preced- 
ing figure  ;  8,  trapezium  (fourth  bone  of 
the  lower  row);  9,  9,  inferior  articular 
surface  of  the  radius  ;  10,  transverse  crest 
for  insertion  of  common  posterior  liga- 
ment of  the  carpus;  11,  superior  extremity 
of  large  metacarpal  bone;  12,  rugosities 
in  which  are  fixed  the  deep  layer  of  the 
suspense)  y  ligament  of  the  fetlock  or 
superior  sesamoid  ligament;  13,  external 
small  metacarpal ;  14,  internal  ditto. 


metacarpus.     Its  internal  face — smooth  and  concave — concurs  in  forming  the 
external  wall  of  the  carpal  sheath.     The  circumference  presents,  in  front,  two 
10 


110  THE  BONES. 

articular  facets  :  the  superior,  concave,  corresponds  to  the  radius  ;  the  inferior, 
convex,  is  in  contact  with  the  second  bone  of  the  upper  row. 

The  other  three  bones  of  this  row  increase  in  volume  from  without  to  within. 

The  second  bone,  os  pyramidalis,  or  cuneiform,  articulates  with  the  radius, 
the  first  bone  of  the  lower  row,  the  third  of  the  upper,  and  the  supercarpal 
bone  ;  it  has,  in  all,  five  articular  facets. 

The  third,  or  os  lunctre,  has  six  facets,  and  is  united  below  to  the  first  and 
second  bones  of  the  second  row. 

The  fourth,  or  os  scajjhoides — the  most  voluminous  of  the  row— has  only  four 
facets,  and  articulates  by  its  inferior  face  with  the  os  magnum  and  trctpezoides. 

Collectively,  the  second,  third,  and  fourth  bones  of  the  upper  row  form  two 
articular  surfaces. 

The  superior,  or  radial  articular  surface,  is  very  irregular  ;  but  in  examining 
it  from  without  to  within,  there  may  be  observed  :  1.  A  glenoid  cavity  on  the 
cuneiform  bone.  2.  In  front,  a  transversely  elongated  condyle  on  the  lunar  and 
scaphoid  bones.    3.  A  groove  placed  behind  the  preceding  condyle. 

The  inferior  articulating  surface,  which  corresponds  to  the  second  row,  is 
constituted  by  several  undulated  facets ;  it  is  convex  outwardly  and  in  front, 
concave  posteriorly  and  inwardly. 

Bones  of  the  Infekior  or  Metacarpal  Row  (Figs.  68,  69). — The  thick- 
ness of  these  bones  decreases  from  without  to  within. 

The  first,  unciform,  or  hookbone  {os  hainatum),  has  four  diarthrodial  facets, 
and  responds,  above,  to  the  two  first  bones  of  the  superior  row  ;  below,  to  the 
first  and  second  metacarpals. 

The  second,  os  magnum,  or  os  capitatum — ^the  largest — has  seven  articular 
facets,  three  of  which  are  on  the  interno-lateral  face.  It  articulates,  above,  with 
the  lunar  and  scaphoides  ;  below,  with  the  principal  metacarpal  and  the  internal 
rudimentary  metacarpal. 

The  third,  or  trapezoides — the  smallest — is  provided  with  five  facets,  and  is 
in  contact  with  the  scaphoides  above,  and  the  middle  and  internal  metacarpals 
below. 

Collectively,  these  bones  of  the  lower  row  form  two  large  diarthrodial 
surfaces.  The  upper  surface  responds  to  the  bones  of  the  upper  row,  and  is 
constituted  in  front,  and  from  without  to  within,  by  a  small  condyle  and  two 
glenoid  cavities  ;  behind,  by  two  isolated  condyles,  formed  by  the  os  magnum 
and  the  trapezoides.  The  inferior  articular  surface  is  only  formed  by  more  or 
less  long  and  plane  facets,  which  incline  towards  each  other.  It  articulates  with 
the  three  portions  of  the  metacarpus. 

Structure  and  deveJopm£nt. — Each  carpal  bone  is  formed  by  a  nucleus  of 
close  spongy  substance,  enveloped  in  a  very  thick  layer  of  compact  tissue.  Each 
is  developed  from  a  single  centre  of  ossification. 

The  carpal  bones  of  the  Ass  much  resemble  those  of  the  Horse,  but  the 
upper  face  of  the  Junar  is  more  concave ;  the  facet  of  the  cuneiform,  for  the 
pisiform,  is  less  concave,  but  larger  and  triangular,  and  is  always  separated  from 
the  superior  articular  surface  by  a  rough,  wide,  and  deep  groove.  The  pisifot  m 
is  more  circular  than  that  of  the  Horse,  and  is  modified  in  shape  to  correspond 
with  the  cuneiform  ;  while  the  inferior  surface  of  the  os  magnum  is  almost  plane 
in  the  Ass,  but  in  the  Horse  it  is  cut  into  a  condyle  in  front  and  a  glenoid  cavity 
behind.  Lesbre  states  that  the  trapezium  is  more  frequent  in  the  carpus  of  the 
Ass  than  the  Horse. 


THE  ANTERIOR  LIMBS. 


Ill 


The  carpal  bones  of  the  Hinny  are  hke  those  of  the  Ass,  but  those  of  the 
Mule  resemble  the  Horse. 


Fi^.  70. 


Differential  Characters  in  the  Carpal  Bones  of  other  Animals. 

A.  Ox,  Sheep,  Goat. — In  these  animals  the  carpus  is  composed  of  only  six  bones — four 
in  the  upper  and  two  in  the  lower  row,  where  the  os  magnum  and  trapezoid  are  fused  together. 
The  pisiform  bone  is  in  shape  as  its  name  implies,  has  no  groove,  and  has  no  relation  with  the 
radius.  The  cuneiform  bone  articulates  with  the  radius  and  ulna.  The  bones  of  the  lower 
row  only  articulate  with  the  large  metacarpal  bone  (Fig.  71). 

B.  Camel. — Among  tlie  seven  carpal  bones  of  the  Camel  are  seen  : 
a  pisiform  bone,  having  on  its  external  face  a  large  smooth  groove ;  a 
lunar,  flattened  on  each  side,  and  deeply  notched  laterally  ;  an  unciform 
having  a  pyramidal  prolongation  behind ;  an  os  magnum,  smaller  than 
the  latter ;  and  a  trapezoid,  little  developed,  and  entirely  removed  to 
the  posterior  part  of  the  carpus. 

C.  Pig. — The  carpus  of  the  Pig,  like  that  of  Man,  contains  eight 
bones — four  in  each  of  the  rows.  The  second  bone  of  the  upper  row 
articulates  with  the  ulna,  and  to  a  very  small  extent  with  the  radius. 
In  the  bones  of  the  lower  row,  it  is  observed  that  the  first  articulates 
witli  the  two  external  metacarpals,  the  second  with  the  great  internal 
metacarpal,  the  third  with  the  preceding  and  the  small  internal  meta- 
carpal. The  fourth,  or  trapezium,  terminates  inferiorly  by  a  blunt 
point,  and  has  no  relations  with  the  metacarpal  bones,  because  the  thumb 
is  entirely  undeveloped  in  this  animal  (Fig.  76). 

D.  Dog,  Cat. — In  the  Cat  and  Dog  there  are  also  eight  bones. 
Lesbre  says,  however,  that  the  scaphoid  and  lunar  are  sometimes  one 
bone,  and  that  often  a  lenticular  bone  is  found  in  the  upper  row.  The 
cuneiform  bone  is  very  developed,  and  occupies  all  the  external  border  of 
the  carpus,  articulating  with  the  ulna,  first  bone  of  the  second  row,  and 
the  first  metacarpal.  'J'he  pisiform  bone  is  elongated,  prismatic,  thick 
at  both  ends,  and  has  in  front  two  contiguous  articular  facets— one  for 
articulation  with  tlie  ulna,  the  other  for  union  with  the  cuneiform  bone. 
The  bones  of  the  lower  row  diminish  in  size  from  the  first  to  the  fourth, 
and  articulate — the  first,  with  the  first  and  second  metacarpals;  the 
second,  with  the  metacarpal  of  the  third  digit;  the  third,  with  the 
fourth  digit ;  and  the  fourth  with  the  metacarpus  of  the  thumb. 

E.  Rabbit. — This  animal  possesses  nine  carpal  bones;  for  it  is 
stated  that  between  the  two  rows  there  is  a  piece  which  Blainville  has 
named  the  intermediate  bone  It  really  belongs  to  the  upper  row,  and 
represents  the  scaphoid.  There  are,  therefore,  five  bones  in  the  first 
carpal  row  of  the  Rabbit,  and  in  this  respect  the  hand  of  this  species 
more  nearly  approaches  the  typical  hand  than  that  of  the  other  domestic 
animals  (see  the  Hand  in  General). 


2.  Metacarpal  Bones  (Figs.  67,  70). 


In  Solipeds,  the  metacarpus  is  composed  of  three  bones, 
named  the  "  metacarpals,"  standing  parallel  to  each  other. 
These  are  the  principal  metacarpal  and  the  two  rudimentary 
metacarpals — an  external  and  internal. 

Principal  Metacarpal  Bone  {psmetacarpi magnum').— 
This  is  a  long  cylindrical  bone,  situated  vertically  between  the 
carpus  and  the  digital  region. 

Bodij. — The  body  is  a  little  depressed  before  and  behind,  which  permits  it  to 
be  described  as  having  two  faces  and  two  borders.  The  anterior  face  is  perfectly 
smooth  and  rounded  from  side  to  side.  The  posterior  face  is  flat,  and  exhibits  : 
1.  Towards  the  upper  third,  the  nutrient  foramen  of  the  bone.     2.  On  the  sides, 


posterior  view  of 
right  metacarpus. 
1,  Head  of  large  meta- 
carpal bone  for  ar- 
ticulation with  the 
trapezoi'i,  magnum, 
and  unciform  ;  2, 
inner  splint,  rudi- 
mentary, or  small 
metacarpal  bone,for 
articulation  with 
the  trapezoid ;  4, 
scabrous  surface  for 
the  attachment  of 
the  suspensory  liga- 
ment ;  5,  nutrinnt 
foramen ;  6,  median 
ridge  separating  tne 
two  inferior  con- 
dyles. 


112  THE  BONES. 

two  narrow,  rousrhened  surfaces,  parallel  and  elongated  vertically,  commencing 
near  the  superior  extremity,  to  disappear  a  little  below  the  middle  of  the  bone  ; 
these  surfaces  are  held  in  apposition  to  the  rudimentary  metacarpals,  by  an 
interosseous  ligament  which  is  often  ossified  in  old  Horses.  The  borders — external 
and  internal — are  very  thick,  round,  and  smooth,  like  the  anterior  face. 

Extremities. — The  superior  is  flattened  before  and  behind,  and  presents.  1. 
Above,  an  undulating  articular  surface,  formed  by  the  union  of  several  flat  facets 
more  or  less  inclined  towards  each  other  ;  they  articulate  with  all  the  lower  row 
of  carpal  bones.  2.  Anteriorly  and  inwardly,  a  tuberosity  for  muscular  insertion. 
3.  Posteriorly — and  directly  above  the  roughened  surfaces  of  the  posterior  face — 
four  small  diarthrodial  facets  in  pairs,  and  running  into  the  larger  articular 
surface  by  their  superior  border ;  they  are  adapted  to  similar  facets  on  the 
rudimentary  metacarpals.  The  inferior  extremity,  elongated  transversely,  articulates 
with  the  first  phalanx  and  the  sesamoid  bones  by  an  articular  sm-face — convex 
from  before  to  behind — which  is  composed  of  tivo  lateral  condyles  separated  by  a 
median  spine.  The  two  condyles  would  be  exactly  alike,  if  the  antero-posterior 
diameter  of  the  external  condyle  were  not  less  extensive  than  that  of  the  opposite 
condyle.  Both  are  hollowed  on  the  sides  by  an  excavation  for  the  attachment 
of  ligamentous  fasciculi. 

Structure  and  development. — The  principal  metacarpal  is  one  of  the  most 
compact  bones  in  the  body.  It  is  developed  from  two  centres  of  ossification, 
one  of  which  is  for  the  inferior  extremity. 

RuDiMENTAEY  METACARPALS  (ossa  metacctrpi pavva). — The  two  rudimentary 
(sm.aU)  metacarpal  (or  splint)  bones  are  elongated,  and  placed  against  the 
posterior  face  of  the  principal  bone,  one  without,  the  other  within.  Each  is  in 
the  form  of  an  inverted  pyramid,  and  exhibits  a  middle  part  and  two  extremities. 

Middle  portion. — Prismatic  and  triangular,  this  ofl^ers  :  1.  Three  faces — an 
external,  smooth  and  rounded  from  one  border  to  the  other  ;  an  internal,  plane, 
and  equally  smooth  ;  an  anterior,  covered  with  asperities  to  give  attachment  to 
the  interosseous  ligament  uniting  the  lateral  metacarpal  bone  to  the  median. 
2.  Three  salient  borders  which  markedly  separate  the  faces  from  each  other. 

Extremities. — The  superior,  the  largest,  is  named  the  head,  and  shows  :  above, 
a  diarthrodial  facet  which  articulates  with  one  or  two  bones  of  the  inferior  row 
of  the  carpus  ;  in  front,  other  two  small  facets  continuous  with  the  preceding, 
and  in  contact  with  similar  facets  on  the  large  metacarpal  bone  ;  on  the  other 
points  of  its  periphery  are  rugosities  for  the  attachment  of  ligamentous  and 
tendinous  fibres.  The  inferior  extremity  only  reaches  to  about  the  lower  fourth 
of  the  large  metacarpal  bone,  and  terminates  in  a  small  button-shaped  enlarge- 
ment, which  is  never  fused  with  the  latter. 

The  two  small  metacarpals,  although  very  much  alike,  may  yet  be  easily 
distinguished  from  each  other.  For  instance,  the  internal  bone  is  always  the 
thickest,  and  often  the  longest ;  besides,  the  superior  articular  surface  of  its 
head  results  from  the  union  of  the  two  facets  articulating  with  the  two  last 
carpal  bones  of  the  lower  tier. 

Structure  and  development. — Of  a  somewhat  compact  texture,  like  all  the  long 
bones,  these  have  no  medullary  canal,  and  are  developed  from  only  one  ossifying 
centre.    Not  unfrequently,  however,  the  tubercle  is  formed  from  a  special  centre. 

The  metacarpus  of  the  Ass  is  recognized  by  :  1.  The  great  inequality  of  the 
small  metacarpals.  2.  The  thickness  of  the  large  metacarpal  (the  width  is  to  the 
thickness  as  1-35  :  1  in  the  A&s,  and  as  1*53  :  1  in  the  Horse).    3.  The  depth  of 


THE  ANTERIOR   LIMBS. 


113 


the  depressions  above  the  inferior  articular  surface,  poste- 
riorly. 4.  The  level  form  of  the  facet  articulating  with  the 
OS  magnum  of  the  second  row.  5.  The  presence  of  a  small, 
flat,  vertical  facet  on  the  posterior  contour  of  the  upper 
articular  surface  of  the  large  metacarpal. 

In  the  Mule  and  Hinny,  the  small  metacarpals  are  nearly- 
alike,  as  in  the  Horse  ;  the  large  metacarpal  is  flattened,  as 
in  that  animal,  with  marked  depressions  posteriorly. 


Differential  Characters  in  the  Metacarpus  of  other  Animals. 

The  number  of  metacarpal  bones  naturally  varies  with  tliat  of  the 

digits : — 

In  the  Carnivora  there  are 5 

In  the  Pig  there  are 4 

In  Ruminants  there  are 2  or  3 

With  regard  to  their  shape  and  form,  they  offer  interesting  differences, 

which  will  now  be  studied. 

A.  Ox,  Sheep,  Goat. — In  these  animals  the  metacarpal  bones  are 
two  in  number — a  principal,  which  itself  results  from  the  consolidation 
of  the  second  and  third  metacarpals ;  another,  altogether  rudimentary, 
situated  outwardly;  and  a  third— not  constant — embedded  in  a  fibrous 
cord  passing  along  the  inner  border  of  tlie  principal  metacarpal. 

The  principal  metacarpal  is  channeled  on  its  anterior  face,  and  for 
its  whole  length,  by  a  deep  vascular  fissure — a  trace  of  the  primitive 
separation  of  the  bone  into  two  pieces.  Tliis  fissure  presents,  inferiorly, 
the  anterior  orifice  of  a  canal  that  completely  traverses  the  bone.  The 
posterior  face  is  nlso  marked  by  a  very  slight  longitudinnl  groove.  The 
superior  extremity  exhibits,  externally  and  posteriorly,  a  single  diar- 
throdial  facet  for  articulation  with  the  rudimentary  metacarpal.  The 
inferior  extremity  is  divided  by  a  deep  notch  into  two  articular  surfaces, 
which  together  resemble  the  single  surface  in  the  Horse ;  each  articulates 
with  one  of  the  digits  ;  the  external  is  always  smaller  than  the  internal. 
In  the  foetus,  the  two  long  bones  that  form  the  great  metacarpal  are 
simply  laid  together,  and  their  medullary  canals  are  separated  from 
each  other  by  the  double  partition  which  results  from  this  apposition ; 
after  their  coalescence,  however,  the  partitions  are  completely  destroyed 
by  absorption,  and  in  a  short  time  there  is  only  a  single  medullary  canal 
for  the  entire  bone. 

Tiie  rudimentary  metacarpal  is  only  a  small  osseous  stylet,  articu- 
lating, by  a  diarthrodial  facet,  beiiind  and  to  the  outside  of  the  superior 
extremity  of  the  principal  metacarpal;  it  is  sometimes  absent  in  the 
Sheep  and  Goat. 

B.  Camel.— The  metacarpus  of  the  Camel  is  very  long,  quadran- 
gular in  its  upper  two-thirds,  and  flattened  behind  and  before  in  its 
inferior  third.  Its  posterior  face  is  converted  into  a  kind  of  concave 
furrow,  by  the  considerably  raised  borders  of  the  bone.  The  superior 
articular  surface  is  divided  into  two  parts  by  a  large  roughened  depres- 
sion ;  the  inner  part  is  on  a  higher  level  than  the  outer.  The  inferior 
extn  mity  is  also  divided  into  two  articular  surfaces  by  a  very  deep 
notch ;  each  surface  is  condyloid  in  its  anterior  moiety,  and  is  like 
that  of  the  Horse  in  its  posterior  moiety. 

C.  Dog,  Cat,  Rabbit.— The  five  metacarpals  of  the  Dog  and  Cat 
articulate  with  each  other,  at  their  superior  extremities,  by  lateral 
facets;  they  offer,  at  their  inferior  extremity,  a  condyle  prolonged  back- 
wards  by  an  articular  surface   resembling  that   of  the  Horse.      The 


forearm  and  foot 

OF  THE  ox  (front 

view). 

1,  Olecranon  ;  2,  body 

of    the    ulna ;     3, 

body  of  the  radius; 

first  and  second  bones 

rudimentary  metacarpals;  10,  principal  inetacarpals ;  11,  external  digit; 


4,  5, 6,  first,  second,  and  third  bones  of  the  upper  row  of  the  carpus;  7, 

of  the  lower  row ;  "         "  '       ' 

12,  internal  digit. 


114 


THE  BONES. 


middle  two  are  always  longer  than  the  two  lateral.     The  smallest  belongs  to  the  fifth  digit,  or 
thumb,  and  is  terminated  inferiorly  by  a  trochlea. 

D.  Pig. — The  four  metacarpals  of  the  Pig  articulate  with  each  other,  as  in  the  Carnivora. 
The  second  and  third  are  larger  than  the  first  and  fourth.  The  fifth  metacarpal  is  not 
developed  (Fig.  76). 

3.  Bones  of  the  Phalangeal  or  Digital  Region  (Figs.  72,  73). 
Solipeds  have  apparently  only  one  digit,  supported  by  the  principal  metacarpal 
bone,  and  composed  of  three  pieces  placed  end  to  end,  one  upon  another.     The 
first  comprises  three  bones — a  principal,  the  first  phalanx — and  two  complemen- 


Fig.  72. 


Fig.  73. 


LATERAL   VIEW    OF   THE   DIGITAL 
REGION   (OUTSIDE   OF    RIGHT   LIMB). 

1,  Large  metacarpal  bone  ;  2,  3,  outer  and 
inner  sesamoids ;  4,  first,  jiroximal,  os  suf- 
fraginis,  or  metacarpal  phalanx ;  5,  its 
posterior  surface  ;  6,  tuberosity  for  liga- 
mentous insertion ;  7,  inner  condyle  of 
ditto  ;  8,  eminences  on  second  phalanx  for 
attachment  of  lateral  ligament;  9,  smooth 
surface  for  passage  of  deep  flexor  tendon 
on  second  phalanx ;  10,  median  or  second 
phalanx,  os  coronae,  or  small  pastern  bone ; 
11,  navicular  bone;  12,  third  phalanx, 
pedal,  or  coffin  bone  ;  13,  its  basilar  process. 


POSTERIOR   VIEW   OF   THE   DIGITAL    REGION. 

1,  Large  metacarpal  bone  ;  2,  3,  outer  and 
inner  splint  bones  ;  4,  5,  sesamoid  bones  ; 
6,  suffraginis  ;  7,  8,  tuberosities  for  inser- 
tion of  crucial  ligaments ;  9,  triangular 
space  for  insertion  of  short  sesamoid  liga- 
ment ;  10,  anterior  face  of  suffraginis ; 
11,  12,  tuberosities  for  ligamentous  inser- 
tion ;  13,  articular  depression  separating 
condyles ;  14,  15,  second  phalanx ;  16, 
scabrous  surface  for  ligamentous  attach- 
ment; 17,  smooth  surface  for  gliding  of 
deep  flexor  tendon  ;  1 8,  navicular  bone  ; 
19,  pedal  bone ;  20,  basilar  process  ;  21, 
plantar  foramen. 


tary  ones,  the  sesamoids.  The  second  is  formed  by  the  second  phalanx,  and  the 
last,  which  terminates  the  limb,  is  constituted  by  the  third  phalanx,  and  an 
accessory  bone  which  has  received  the  name  of  the  small  sesamoid  {navicular 


First  (proximal)  or  Metacarpal  Phalanx  (Large  Pastern  Bone,  or 
Os  Suffraginis).— The  first  phalanx  (Figs.  72,  73),  the  smallest  of  all  the 
long  bones,  is  situated  in  an  oblique  direction  from  above  downwards,  and 
behind  to  before,  between  the  principal  metacarpal  and  the  second  phalanx. 


THE  ANTERIOR  LIMBS.  115 

Body. — Flattened  before  and  behind,  this  bone  exhibits  :  an  anterior  face^ 
round  from  one  side  to  the  other,  and  slightly  roughened  above  and  below  ; 
a  posterior  face,  flat,  covered  with  ligamentous  imprints  in  the  form  of  a  triangle 
with  the  base  reversed  ;  two  lateral  borders,  thick,  rounded,  and  provided  with 
some  imprints. 

Extremities. — The  superior,  the  largest,  presents  :  Above,  an  articular  surface 
adapted  to  the  inferior  metacarpal  surface,  and  consequently  composed  of  two 
glenoid  cavities  separated  by  a  groove  running  from  front  to  back  ;  laterally, 
and  a  little  posteriorly,  a  well-defined  tubercle  of  iiisertion.  The  inferior  extremity 
has  a  transversely  elongated  articular  surface,  to  articulate  with  the  second 
phalanx  ;  this  surface  is  formed  by  tivo  condyles  separated  by  a  middle  groove, 
and  surmounted  laterally  by  a  small  tuberosity  for  ligamentous  insertions.  The 
external  condyle  is  smaller  than  the  internal,  and  when  the  bone  is  placed  upon 
a  horizontal  plane,  the  anterior  face  turned  upwards,  it  only  touches  by  three 
points— the  two  tubercles  of  the  upper  extremity  and  the  internal  condyle  ;  by 
pressing  on  the  external  condyle,  it  is  easy  to  make  the  bone  oscillate. 

The  first  phalanx  is  a  very  compact  bone,  and  is  developed  from  two  points 
of  ossification,  one  of  which  is  for  the  superior  extremity  alone.  Professors 
Yachetta  and  Fogliata,  of  Pisa,  assert  that  this  bone,  as  well  as  the  second  phalanx, 
has  three  centres  of  ossification  during  uterine  life. 

Sesamoids  (Figs.  72,  7^). — These  are  two  small,  short  bones  placed  side 
by  side  behind  the  superior  extremity  of  the  first  phalanx,  the  articular  sur- 
face of  which  it  completes,  as  it  has  not  extent  enough  to  be  exactly  adapted  to 
the  metacarpal  surface.  Each  of  these  bones  represents  a  small,  irregularly  shaped 
polyhedron,  or,  rather,  a  short  trifacial  pyramid.  It  offers  :  an  anterior  face, 
which  is  articular,  and  corresponding  to  the  inferior  extremity  of  the  principal 
metacarpal  bone,  moulded,  as  it  were,  on  one  of  the  condyles  and  one  of  the 
sides  of  the  median  ridge  ;  a  posterior  face,  covered  with  cartilage  in  the  fresh 
state,  and  forming,  with  that  of  the  opposite  bone,  a  gliding  concave  surface  for 
the  flexor  tendons  of  the  phalanges  ;  a  latercd  face,  studded  with  ligamentous 
imprints  ;  a  summit,  directed  upwards  ;  and  a  base,  turned  downwards,  and 
serving  for  the  attachment  of  several  ligaments. 

Second  (or  Median)  Phalanx  (Os  Coron.^,  Small  Pastern  Bone  (Figs. 
72,  73). — This  is  a  short  bone,  situated  in  the  same  oblique  direction  as  the 
first  phalanx,  and  between  it  and  the  third.  Its  general  form  is  that  of  a 
cube  flattened  before  and  behind,  and  offering  the  following  features  :  an  anterior 
face,  covered  with  some  slight  imprints  ;  a  posterior  face,  provided,  above,  with  a 
transversely  elongated  gliding  surface  ;  a  superior  face,  channeled  by  two  glenoid 
cavities,  to  match  the  inferior  articulating  surface  of  the  first  phalanx  ;  an  inferior 
face,  formed  on  the  same  plan  as  the  last — being  occupied  by  two  unequal  condyles, 
which  articulate  with  the  third  phalanx  and  the  navicular  bone  ;  two  lateral  faces 
exhibiting  a  very  marked  imprint.  In  the  interior  of  this  bone  is  found  a  nucleus 
of  very  condensed  spongy  substance,  enveloped  in  a  layer  of  compact  tissue. 

It  is  usually  developed  from  a  single  centre  of  ossification,  though  in  many 
subjects  there  is  a  complementary  nucleus  for  the  superior  articular  and  the 
posterior  ghding  surface. 

Third  (Distal  or  Ungual)  Phalanx,  Os  Pedis  (Pedal  or  Coffin  Bone) 
(Figs.  72,  73,  74). — This  is  a  short  bone  which  terminates  the  digit,  and  sustains 
the  hoof  that  incloses  it  and  the  navicular  bone.  When  completed  by  a  special 
tibro-cartilaginous   apparidus,  it  represents  the  segment  of  a  very  short  cone. 


116  THE  BONES. 

obliquely  truncated  behind,  from  the  summit  to  the  base.     It  offers  for  study : 
three  faces,  three  borders,  and  two  lateral  angles. 

Faces. — The  anterior,  convex  from  side  to  side,  and  cribbled  by  porosities  and 
vascular  openings,  shows  on  each  side:  1.  The  preplantar  fissure — a  horizontal 
groove  more  or  less  ramified,  which  commences  behind,  between  the  retrossal  and 
basilar  processes,  terminating  in  front  in  one  of  the  foramina  that  penetrate 
the  bone.  2.  The  patilohe  eminence — a  roughened  projecting  surface,  situated 
between  the  preceding  fissure  and  the  inferior  border  of  the  bone.  The  superior 
face  is  occupied  by  an  articular  surface  formed  by  two  glenoid  cavities  and  a  slight 
median  ridge  ;  it  comes  in  apposition  with  the  inferior  face  of  the  second  phalanx. 
The  inferior  (or  solar)  face,  hollowed  out  like  an  arch,  is  divided  into  two  regions 
by  the  semilunar  crest,  a  salient  line  which  describes 
^'--  '^^-  a  curve  forwards.     The  anterior  region  is  perforated 

with  very  fine  porosities,  and  corresponds  to  that  part 
of  the  hoof  named  the  sole.  The  posterior  region 
shows,  immediately  behind  the  semilunar  crest,  a 
median  imprint,  and  two  lateral  channels  designated 
the  plantar  fissures.  These  originate  at  the  root  of 
tlie  basilar  process,  are  directed  obliquely  downwards 
and  inwards,  and  open  into  the  plantar  foramina, 
the  external  orifices  of  two  large  canals  which  enter 
PLANTAR  SURFACE  OF  THIRD     ^j^g  jjQ^g  ^ud  uultc  lu  Its  luterlor  to  form  the  semilunar 

PHALANX. 

«  o      sinus. 

1,  Lower   face,  or  sole  \  2,  i,  r,      i  n^^  •  ^  ■^  -ii, 

wings,    or    retrossal    pro-  Borders.— ThQ   Superior   describes   a   curve,   with 

cesses;  4.  internal  border;     the  convexity  forward,  and  presents  :  1.  In  its  middle, 
5,  plantar  foramina.  ^.j^^  pyramidal  eminence  of  the  OS  pedis — a  single  tri- 

angular process,  flat  before  and  behind,  roughened  on  its  anterior  aspect,  and 
concurring,  by  its  posterior  surface,  to  form  the  articular  surface  which  responds 
to  that  of  the  second  phalanx.  2.  Laterally,  two  facets  of  insertion  which 
encroach  on  the  anterior  surface,  and  even  advance,  posteriorly,  nearly  to  the 
preplantar  fissure.  The  inferior  border  is  thin,  dentated,  convex,  and  semicir- 
cular ;  it  is  perforated  by  from  five  to  ten  large  foramina,  which  pass  into  the 
bone.  The  posterior  border  is  slightly  concave  ;  on  it  is  observed  a  very  narrow, 
transversely  elongated,  diarthrodial  facet,  which  becomes  confounded  with  the 
superior  large  articular  surface,  and  is  adapted  to  a  similar  facet  on  the  navicular 
bone. 

Lateral  angles. — These  are  two  projections  directed  backwards,  on  the  summit 
of  which  the  three  borders  of  the  bone  unite,  and  which  gives  attachment  to  the 
lateral  fibro-cartilages.  A  deep  notch — the  origin  of  the  preplantar  fissures — 
separates. each  into  two  particular  eminences:  one,  the  superior,  named  by 
Bouley  the  basilar  process ;  the  other,  the  inferior,  prolonged  behind,  and  desig- 
nated by  Bracy  Clark  the  retrossal  process  (from  retro,  behind,  and  ossa,  bone). 

Sfructvre. — The  os  pedis  exhibits  in  its  interior  the  semilunar  sinus — a  cylin- 
drical, transversely  elongated,  and  semicircular  cavity  resulting  from  the  arching 
anastomoses  of  the  two  plantar  canals.  From  this  cavity  pass  off  numerous 
channels,  which  anastomose  frequently  with  each  other,  and  open  externally  by 
the  foramina  on  the  anterior  face  of  the  bone,  or  by  those  on  its  inferior  border. 
The  OS  pedis  has  for  its  base  a  nucleus  of  spongy  substance,  surrounded  by  a 
layer  of  compact  tissue.  The  latter  is  thicker  towards  the  pyramidal  eminence 
than  elsewhere,  and  sends  into  the  interior  numerous  prolongations  which  form 


THE  ANTERIOR   LIMBS. 


11? 


the  walls  of  the  semilunar  sinus,  as  well  as  the  bony  channels  which  spring 
from  it. 

Development. — The  third  phalanx,  formed  from  a  single  nucleus  of  ossifica- 
tion, undergoes  numerous  changes  in  its  configuration  during  life.  Thus,  in  the 
young  animal  the  lateral  angles  are  thick,  obtuse,^  and  but  little  prolonged 
posteriorly  ;  but  as  it  grows  older,  they  increase  in  length  and  become  salient. 
The  development  they  then  assume,  is  due  to  the  progressive  ossification  of  the 
lateral  cartilages  implanted  on  their  surface.  It  often  happens,  in  very  old  horses 
that  this  ossifying  process  is  carried  to  an  extreme  degree,  and  nearly  the  whole 
substance  of  these  complementary  organs  is  invaded.  From  the  commencement, 
its  inevitable  result  is  to  convert  the  notch  which  separates  the  basilar  from  the 
retrossal  process  into  a  foramen. 

The  comple  me  atari/  Jihro-cartilaiiinous  apparatus  of  the  as  pedis. — To  under- 
stand properly  the  disposition  of  this  portion  of  the  .foot,  it  is  necessary  that  a 
previous  knowledge  of  the  ligaments 
and  tendons  attached  to  the  os  pedis 
should  have  been  acquired  ;  therefore 
a  detailed  description  will  be  given 
when  the  Horse's  foot  is  studied  as  a 
whole,  in  the  article  on  the  Sense  of 
Touch.  It  will  be  sufficient  here  to  state 
that  this  apparatus  consists  of  two 
lateral  pieces — the  fibro-cartilages  of  the 
OS  pedis,  united  behind  and  below  by 
iheplantar  cushion — a  fibrous  and  elastic 
mass  on  which  rests  the  navicular  bone, 
through  the  medium  of  the  perforans 
tendon. 

The  Small  Sesamoid  or  Navicular 
Bone  (Figs.  72,  75). — This  short  bone 
is  annexed  to  the  third  phalanx,  behind 
which  it  is  situated  ;  it  is  elongated 
transversely,  flattened  above  and  below, 
and  narrow  at  its  extremities.  It  offers  : 
1.  A  superior  face,  on  which  are  pro- 
longed the  glenoid  cavities  and  the 
median  ridge  of  the  articular  surface 
of  the  OS  pedis  ;  it  articulates  with  the 

second  phalanx.  2.  An  inferior  face,  dixided  by  a  slight  ridge  into  two  undulated 
facets,  and  covered  with  cartilage  to  form  a  gliding  surface.  An  anterior  border, 
channeled  lengthways  by  a  groove  of  insertion,  above  which  is  remarked  a  diar- 
throdial  facet  that  brings  the  small  sesamoid  into  contact  with  the  posterior  border 
of  the  third  phalanx.  4.  A  posterior  border  and  two  extremities,  for  ligamentous 
insertion.  This  bone,  as  well  as  the  sesamoids,  originates  from  a  single  centre  of 
ossification.  It  is  formed  of  a  layer  of  compact  tissue  enveloping  a  nucleus  of 
very  condensed  spongy  substance.  (For  differences  in  the  Ass,  see  Posterior 
Limb.) 


NAVICULAR    BONE    OF    THE    HORSE. 

Anterior  Border  and  Inferior  Face.  1,  articu- 
lar facet  for  the  facet  on  the  po.stenor  border 
of  the  OS  pedis;  2,  roughened  groove  on  the 
anterior  border ;  3,  inferior  face,  smooth  and 
undulated.  B,  Posterior  Border  and  Superior 
Face.  1,  Articular  face  for  the  lower  end  of 
the  second  phalanx;  2,  posterior  border,  with 
many  foramina. 


118  THE  BONES. 

• 

Differential  Characters  in  the  Digital  Region  of  other  Animals. 
In  the  other  domesticated  animals,  the  number  of  complete  digits  is  as  follows : — 

Carnivora 5 

Pig 4 

Ruminants •    ....     2 

A.  Ox,  Sheep,  Goat. — These  animals  certainly  possess  four  digits,  but  only  two  are  perw 
feet— the  mMius  and  annularis — and  these  articulate  with  the  inferior  extremity  of  the  principal 
metacarpal  (Fig.  71).  The  two  others — the  index  and  auricularis — are  in  a  rudimentary  con- 
dition, and  are  represented  by  two  small  bones  situated  above  and  behind  the  metacarpo- 
phalangeal articulation. 

In  the  Ox,  Sheep,  and  Goat,  each  of  the  perfect  digits  comprises  (like  the  single  digit  of  the 
Horse)  three  phalanges  and  three  sesamoids. 

The  first  phalanx  fairly  represents  the  moiety  of  this  phalanx  in  the  Horse.     It  has  no 

Fig.  77. 
Fig.  76.  y^ 

^- 

if'  ''  *~ 


ANTERIOR   LIMB   OF   THE   PIGi. 


FOREARM  AND  FOOT  OF  THE  DOG  (AN- 
TERIOR face). 

1,  First  digit ;  2,  second  digit ;  3,  third 
digit ;  4,  fourth  digit  ;  5,  thumb ;  6, 
7,  8,  9,  first,  second,  third,  and  fourth 
bones  of  the  lower  row  of  carpnl  bones  ; 
10,  11,  first  and  second  bones  of  the 
upper  row;  12,  supercarpal  bone; 
13,  body  of  the  ulna  ;  14,  apex  of  the 
olecranon;  15,  beak  of  the  olecranon; 
16,  body  of  the  radius. 


posterior  imprints,  but  shows  them  on  its  inner  surface  for  the  attachment  of  several  ligaments. 
This  internal  face  is  plane,  and  the  external  convex ;  these  characters  are  repeated  in  the  other 
two  phalanges.  It  is  also  remarked  in  all  the  phalangeal  bones,  that  the  external  articular 
facet  of  the  extremities  is  always  larger  than  the  iuterual.     Of  the  two  sesamoids,  the  external 


THE  ANTERIOR   LIMBS. 


119 


Fig.  78. 


is  wider  and  less  elongated  than  tlie  internal.  They  articulate  with  each  other  and  with 
the  first  phalanx,  by  small  diarthrodial  facets. 

The  second  phalanx  is  hollowed  internally  by  a  small  medullary  cavity. 

The  ungual  phalanx,  as  a  whole,  resembles  one  of  the  lateral  moieties  of  the  os  pedis  of 
Solipeds.  Tills  phalanx  has  no  complementary  fibro-cartilage,  basilar  process,  or  retrossal 
eminence,  nor  yet  a  cavity  for  insertion  on  the  sides  of  the  pyramidal  eminence.  The  semilunar 
crest  is  replaced  by  an  obtuse,  thick,  and  rugged  ridge,  which  occupies  quite  the  posterior  limit 
of  tlie  inferior  face  of  the  bone.  Three  large  canals  penetrate  the  third  phalanx— two  to  the 
base  of  the  [lyramidal  eminence,  and  one  towards  the  origin  of  the  preplantar  fissure.  They 
form,  in  the  interior  of  the  bone,  a  vast  sinus,  giving  rise  to  several  vascular  canals  which  open 
on  the  surface.  There  is  only  one  foramen  at  the  base  of  the  pyramidal  eminence  in  the  smaller 
Ruminants. 

B.  Camel. — In  this  animal,  there  are  in  each  digit  only  three  phalanges  and  two  large 
sesamoids.  The  direction  and  form  of  these  phalanges 
differ  notably  from  what  is  seen  iu  Ruminants.  The 
first  phalanx  is  long,  very  oblique,  constricted  in  the 
middle,  and  very  thick  at  both  ends.  On  the  superior 
articulating  surface  is  a  single  glenoid  cavity,  dirided 
posteriorly  by  a  median  groove.  The  inferior  surface  is 
prolonged  on  the  posterior  face  of  the  bone,  which  is 
converted  into  a  kind  of  pulley.  The  second  phalanx  is 
nearly  horizontal,  and  much  flattened  above  and  below. 
The  ungual  phalanx  is  somewhat  like  an  irregular 
trifacial  pyramid  with  a  blunt  summit ;  near  its  base, 
on  its  upper  face,  it  has  a  roughened  tubercle. 

C.  Pig. — The  Pig  has  four  complete  digits  articu- 
lating from  the  metacarpals ;  the  thumb  is  absent.  The 
index  and  auricularis— or  fourth  and  fifth  digits — are 
short,  and  do  not  usually  rest  on  the  ground  (Fig. 
76). 

D.  Dog,  Cat,  Rabbit.— The  five  digits  of  the 
log  and  Cat  are  exactly  analogous  to  those  of  Man. 
Thus,  the  external  corresponds  to  the  auricularis,  the 
second  to  the  annularis,  the  third  to  the  medius,  the 
fourth  to  the  index,  and  the  internal  to  the  thumb. 
The  latter,  very  small,  has  only  two  phalanges,  and  does 
not  come  into  contact  with  the  ground.  Each  of  the 
first  four  is  composed :  1.  Of  a  first  phalanx,  to  which  are 
annexed  two  sesamoids.  2.  A  second  phalanx,  which 
represents  a  veritable  long  bone.  3.  A  conical  phalan- 
gette, pointed,  curved  downwards,  and  hollowed  at  its 
base  by  a  circular  groove,  in  which  is  lodged  the  matrix 
of  the  claw.  The  small  sesamoid  (or  navicular  bone) 
la  absent,  but  is  replaced  by  a  prominence  of  the  ungual 
phalanx.  The  auricularis  and  index  are  alike,  and  not 
80  long  as  the  annularis  and  medius,  which  are  the  same 
in  length. 


HUMAN  SCAPULA  (EXTERNAL  ASPECT). 

1,  Supra-spinous  fossa;  2,  infra-spinous 
fossa  ;  3,  superior  border  ;  4,  supra- 
sca|)ular  notch;  5,  anterior  or  axil- 
lary boi-der  ;  6,  head  of  the  scapu- 
lar and  glenoid  cavity ;  7,  inferior 
angle ;  8,  neck  of  the  scapula ;  9, 
posterior  border;  10,  spine;  11, 
triangular  smooth  surface,  over 
which  the  tendon  of  the  trapezius 
glides,  with  the  tuberculum  spinse 
scapulae  between  it  and  10 ;  12, 
acromion  process  ;  13,  nutrient  fora- 
men ;   14,  coracoid  process. 


Comparison  of  the  Thoracic  Limb  of  Man  with  that  of  the  Domesticated  Animals. 

A.  Shoulder. — The  shoulder  of  man  has  for  its  base  two  well-developed  bones — the  scapula 
and  clavicle.  The  scapula  (Fig.  78)  is  more  distinctly  triangular  than  that  of  all  the  domesti- 
cated animals ;  its  vertebral  border  is  also  more  extensive.  The  scapular  spine,  very  elevated 
is  continued  by  an  acromion  whose  extremity  reaches  to  above  the  scai)ulo-humeral  articulation. 
The  latter  is  separated  from  the  remainder  of  the  spine  by  a  constriction  called  the  pedicle  of 
the  acromion.  The  coracoid  process  is  voluminous,  and  resembles  a  semi-flexed  finger.  The 
clavicle  extends  from  the  acromion  to  the  sternum ;  it  is  flattened  above  and  below,  and  flexed 
like  an  italic  S.  This  inflection  of  the  clavicle  is  more  pronounced  in  the  male  than  the 
female. 

B.  Arm. — The  humerus  (Fig.  79)  of  Man  is  much  longer  than  that  of  animals.  Its  dia- 
physis  is  prismatic,  and  divisible  into  three  faces  ;  the  deltoid  imprint  has  the  form  of  a  V  with 
its  point  directed  downwards.     The  voluminous  articular  head  is  turned  inwards ;  the  bicipital 


120 


THE  BONES. 


groove  is  single,  and  looks  outwards.     The  inferior  articular  surface  resembles  that  of  animals, 
except  that  the  condyle  is  more  distinct. 

C.  Forearm  (Fig.  80). — The  two  bones  of  the  forearm,  as  we  have  already  seen,  only  articu- 
late by  their  extremities;  they  are  separated  from  one  another  in  their  middle  part.  The 
superior  extremity  of  the  radius  corresponds  with  the  condyle  of  the  humerus  ;  that  of  the  ulna 
articulates  with  the  humeral  trochlea.  The  coroiioid  process  belongs  to  the  ulna.  At  the 
lower  extremity  of  the  forearm,  it  is  reiniirked :  1.  That  the  radius  corresponds  with  tlie  greater 
portion  of  the  cnrpus,  while  the  ulna  only  articulates  with  the  pyramidalis.  2.  Tliat  the  radio- 
carpal articulation  is  protected  outwardly  and  inwanlly  by  two  small  osseous  prolongations — 
the  styloid  processes  of  thu  ulna  and  radius. 

D.  Hand. — 1.  Carpus  (Fig.  81). — The  carpus  of  Man  is  composed  of  eight  bones — four  in 
each  row.     The  three  tirst  of  the  upper  row  articulate  with  the  radius  ;  the  fourth  responds  to 


F.2. 


Fig.  8U. 


RIGHT   HUMAN   HUMERUS   (ANTERIOR 
SURFACE). 

1,  Shaft ;  2,  head  ;  3,  neck ;  4,  greater  tu- 
berosity ;  5,  lesser  tuberosity  ;  6,  bici- 
pital groove  ;  7,  interior  bicipital  groove  ; 
8,  posterior  bicipital  ridge  ;  9,  rough  sur- 
face for  insertion  of  deltoid;  10,  nutrient 
foramen;  11,  eminentia  capitata ;  12, 
trochlea;  13,  external  condyle;  14,  in- 
ternal condyle ;  15,  external  condyloid 
ridge;  16,  internal  condyloid  ridge;  17, 
fossa  for  the  coronoid  process  of  ulna. 


HUMAN    ARM-BONES    (FRONT   VIEW). 

1,  Shaft  of  ulna  ;  2,  greater  sigmoid  notch  j 
3,  lesser  sigmoid  notch ;  4,  olecranon 
process  ;  5,  coronoid  process  ;  6,  nutrient 
foramen ;  7,  ridges  for  insertion  of  in- 
terosseous membrane  ;  8,  capitalum  ulnae  ; 
9,  styloid  process;  10,  shaft  of  radius; 
11,  its  head  ;  12,  its  neck  ;  13,  its  tube- 
rosity ;  14,  oblique  line  ;  15,  lower  end 
of  bone  ;   16,  styloid  process. 


the  ulna.  In  the  bones  of  the  lower  row,  the  trapezium  responds  to  the  metacarpal  of  the  thumb 
and  that  of  the  index;  the  trapezoides  to  the  latter  only,  the  os  magnum  am  unciform  to  the 
metacarpals  of  the  medius,  annularis,  and  little  finger.  The  pisiform  bone  and  the  cuneiform 
process  of  the  unciform  convert  the  posterior  face  of  the  carpus  into  a  channel. 

2.  Metacarpus  (Fig.  81).— The  five  metacarpals  of  Man  are  parallel  to  each  other;  they 
articulate  by  their  superior  extremities  witli  the  bones  of  the  carpus,  and  by  their  inferior  ex- 
tremities witii  the  phalange-s.  They  are  all  concave  in  their  middle  portion,  and  tiiickened  at 
their  ends.  Tlie  metacarpal  of  the  thumb  is  the  shortest  and  strongest.  The  others  diminish 
in  volume  from  the  fourth  to  the  first. 


THE  ANTERIOR   LIMBS. 


121 


Fig.  81. 


3.  Digital  Region  (Fig.  81). — Here  we  fiurl  five  digits,  each  compcsed  of  three  bony  colum- 
nettes,  with  tlie  exception  of  the  thumb,  in  which  only  the  second  and  third  phalanges  are 
present.  They  decrease  in  length  from  the  third  to  the  first,  and  the  third  to  the  fifth.  The 
first  and  second  phalanges  are  small  semi-cylindrical  bones,  slightly  thickened  at  their  ex- 
tremities. The  ungual  phalanges  are  constricted  in  their  middle,  and  widened  like  a  horse- 
slioe  at  their  inferior  extremity  ;  the  palmar  face  is  roughened,  the  dorsal  face  smooth. 

Article  V. — The  Hand  in  General. 

1.  The  limits  of  this  region,  as  already  mentioned,  extend  from  the  lower 
end  of  the  forearm  to  the  third  phalanx,  inclusive.  If  it  is  examined  super- 
ficially, the  diiferences  it  presents  in  the  number  and  arrangement  of  the  parts 
composing  it  are  very  striking.  The  digits  that 
terminate  the  hand  are  pieces  which,  from  the  earliest 
times,  have  most  occupied  the  attention  of  observers. 
Thus,  when  we  do  not  go  beyond  simple  appearances, 
it  might  be  believed  that,  with  regard  to  the  number 
of  digits,  there  were  great  diiferences  in  animals. 
From  this  point  of  view,  the  domestic  animals  form 
a  nearly  decreasing  series,  commencing  with  the  Gar- 
ni vora  and  terminating  with  Solipeds.  And  in  relying 
upon  these  appearances,  some  anatomists  have  dis- 
tinguished these  animals  as  monodacti/les,  didad ij.es, 
and.  regular  and  irregular  tetradadijUs  ;  but  in  the 
generalizations  in  this  work,  we  have  ignored  these 
designations,  as  they  are  in  complete  disaccord  with  the 
teachings  of  philosophical  anatomy.  In  fact,  although 
the  Horse  appears  to  have  only  one  digit,  the  Ox  two, 
the  Pig  four,  the  Dog  and  Cat  five,  yet  the  hand  in  all 
these  creatures  may  be  referred  to  the  pentadactylous 
type.  To  demonstrate  this  unity  in  composition,  the 
laws  promulgated  by  Grethe  with  regard  to  the  vege- 
table kingdom,  and  developed  and  applied  to  animals 
by  Geoff"roy  Saint-Hilaire,  are  accepted  ;  and  we  have 
indicated  in  these  few  words  the  laws  of  analogy  and 
harmony,  the  principle  of  relations,  the  elective  affini- 
ties, the  organic  adjustments. 

These  laws  and  these  principles  have  been  more 
particularly  applied  to  the  study  of  the  'hand  of 
animals  by  Joly  and  Lavocat,  Paul  Gervais,  Richard 
Owen,  Delplanque,  and  Arloing.  Comparisons,  and 
the  attentive  study  of  normal  conditions  and  anomalies,  have  served  as  a  basis 
for  the  conclusions  arrived  at  by  these  authorities.  The  anomalies  that  certain 
zoologists  were  tempted  to  regard  as  proper  facts  likely  to  mislead  philosophical 
anatomists,  have,  on  the  contrary,  been  of  assistance  to  the  latter ;  because, 
according  to  the  expression  of  Geoffroy  Saint-Hilaire,  "  an  anomaly  restores  that 
which  \ye  term,  in  zoology,  -normal  conditions." 

2.  The  Archetypal  Hand.  The  chief  type  is  composed  of  five  digits, 
and  a  complete  digit  in  three  sections — the  carpus,  -which  has  two  bones  ;  the 
metacarpus,  which  has  only  one  :  and  the  phalangeal  section,  which  has  three. 
This  constitution  of  the  hand  has  been  conceived  by  Joly  and  Lavocat,  and 
reasoning  would  sanction  its  acceptance,  if  it  were  not  presented  in  some  animals 


PALMAR    SURFACE    OF    LEFT 
HUMAN    HAND. 

1,  Scaphoid  bone;  2,  semilu- 
nare;  3,  cuneiform  ;  4,  pisi- 
form ;  5,  trapezium  ;  6, 
groove  in  trapezium  for  ten- 
don of  flexor  car))i  radialis; 
7,  trapezoides  ;  iS,  magnum  ; 
9,  unciform  ;  10,  10,  the 
five   metacarpal  bones;    11, 

11,  first   row   of  phalanges; 

12,  12,  second  row;  13,  13, 
third  row;  14,  first  phalanx 
of  the  thumb;  15,  second 
and  last  phalanx. 


122 


THE  BONES. 


DESCRIPTION  ON   OPPOSITB  PAGE. 


THE  ANTERIOR  LIMBS.  123 

—such  as  the  3Ioh,  Marmot,  and  Guinea-pig— each,  of  which  have  five  digits 
arising  from  the  two  carpal  bones.  In  order  to  study  the  hand,  these  authorities 
place  it  in  its  natural  position — pronation  ;  and  the  different  pieces  are  reckoned 
from  without  to  within  by  the  numbers  1,  2,  3,  4,  5. 

3.  Modifications  in  the  Archetype.  But  the  archetypal  hand  is  not 
constantly  realized,  even  when  five  digits— such  as  they  are  usually  understood 
to  be — are  present.  The  hmnan  hand,  for  instance,  is  formed  by  five  digits  and 
five  metacarpal  bones,  with  only  eight  bones  in  the  carpus.  When  we  go  from 
Man,  the  number  of  bones  in  the  three  sections  is  more  or  less  diminished  ;  and 
in  the  carpus  of  the  domestic  animals,  as  in  that  of  Man,  if  the  archetypal 
number  does  not  exist  in  all  the  sections,  it  is  because  certain  pieces  have  been 
fused  with  adjoining  ones,  or  they  are  not  developed.  In  several  instances, 
certain  bones  become  so  atrophied  that  at  the  first  glance  they  are  not  recog- 
nizable. Joly  and  Lavocat  at  first  imagined  that  these  atrophies  took  place 
according  to  some  fixed  law  ;  they  believed  that  the  atrophy  operated  on  the 
middle  part  of  the  bones,  extending  downwards,  and  that  the  last  piece  to  dis- 
appear, in  an  atrophied  digit,  was  that  of  the  carpus. 

But  since  the  publication  of  their  first  memoires,  Lavocat  has  had  occasion 
to  state  that  this  law  is  not  absolute.  After  these  preliminary  remarks,  we 
will  study  the  modifications  in  the  archetypal  hand  in  Man  and  the  domestic 
animals,  and  demonstrate  that  in  these  it  may  easily  be  referred  to  the  pentadacty- 
lous  type. 

1.  Man. — The  human  hand  having  five  digits  and  five  metacarpal  bones,  it 
is  rational  to  admit  the  virtual  existence  of  five  pieces  to  each  of  the  carpal  rows. 
Materially,  there  are  only  four  bones  in  each  of  these  two  rows  ;  but  the  com- 
parative study  of  the  relations  of  each  of  these  bones  in  the  human  carpus,  and 
in  that  of  animals  which  are  in  possession  of  the  archetypal  hand,  leads  to  the 
belief  that  the  scaphoid  is  the  result  of  fusion  of  the  fourth  and  fifth  bones  of 
the  upper  row,  and  the  unciform  the  fusion  of  the  first  and  second  bones  of  the 

HAND   OF   MAN    AND   THE   DOMESTIC   MAMMALIA,   NORMAL   AND   TERATOLOGICAL   (Fig.  82). 

A,  Human  hand  (dorsal  face). 

B,  Dog's  hand  (same  position). 

C,  Pig's  hand  (normal  condition).     1,  Trapezium. 

c',  Pig's  hand  :  the  thumb  (1)  is  completely  developed  from  the  trapezium  (2). 

D,  Sheep's  hand  (normal  condition).  1,  Principal  metacarpal  ;  2,  rudimentary  metacarpal,  external ; 
3,  ditto,  mternal  (not  constant). 

E,  Hand  of  the  aquatic  Chevrotain.  1,  Double  principal  metacarpal;  2,  3,  lateral  metacarpals 
followed  by  phalanges. 

F,  Lamb's  hand,  a.  Carpus  and  superior  extremity  of  metacarpus  (seen  in  profile),  on  which  the 
metacarpus  of  the  thumb  (1)  was  shown.  6,  Ditto  (face)  :  1,  internal  rudimentary  metacarpal 
completely  developed  ;  2,  horny  plate  representing  the  thumb  on  the  surface  of  the  skin  ;  3,  horny 
plate  representing  the  first  digit  on  the  surface  of  the  skin. 

G,  Lamb's  hand  on  which  are  four  complete  digits.  1,  Principal  metacarpal ;  2,  3,  lateral  meta- 
carpals completely  developed. 

H,  Horse's  hand  (normal  condition).     1,  Principal  metacarpal ;  2,  3,  rudimentary  metacarpals. 

I,  Horse's  hand,  adult  (teratological  specimen,  showing  the  division  of  the  phalangeal  section, 
1,  1,  of  the  single  digit  of  Solipeds). 

K,  Foal's  hand  (teratological  specimen  described  by  Delplanque).  1,  Principal  metacarpal  bifid  in 
its  lower  third ;  2,  e.\ternal  rudimentary  metacarpal ;  3,  4,  phalangeal  sections  resulting  from 
the  division  of  the  great  digit. 

L,  Horse's  hand,  adult  (teratological  piece),  a.  Carpus  (inner  aspect)  :  1,  trapezium  ;  2,  trapezoid ; 
3,  principal  metacarpal  ;  4,  internal  rudimentary  metacarpal  transformed  into  a  complete  meta- 
carpal ;  5,  styliform  piece  representing  the  metacarpal  of  the  thumb.  6,  Inferior  extremity  of 
the  digital  region  (inner  aspect):  1,  principal  metacarpal,  followed  by  normal  phalanges;  2,  in- 
ternal rudimentary  metacarpal  transformed  into  a  complete  metacarpal,  followed  by  normal 
phalanges. 


124  THE  BONES. 

inferior  row  (Fio;.  82,  a).     It  is  easy,  therefore,  to  refer  Man  to  the  most  perfect 
pentadactylous  type. 

2.  Carnii'ora. — The  hand  of  the  Dog  and  Cat  has  five  distinct  digits,  the 
internal  of  which — the  thumb — smaller  than  the  others,  does  not  reach  the 
ground  (Fig.  82,  b).  By  the  metacarpus  and  the  phalangeal  section,  these 
animals  belong,  then,  to  the  pentadactylous  type.  They  appear  to  be  removed 
from  it  by  the  constitution  of  the  carpus,  for  it  has  only  seven  (Dog)  or  eight 
bones  (Cat)  ;  there  has  been  fusion  of  the  lunar  and  scaphoid,  but  the  fifth  bone 
of  the  upper  row  is  free.  The  number  of  bones  being  thus  raised  to  eight,  we 
know  how  they  may  be  referred  to  the  archetype — by  proceeding  in  the  same 
manner  as  for  the  human  carpus. 

3.  Rodents. — The  Rabbit  has  five  digits,  like  the  Cat,  and  nine  carpal  bones. 
Five  of  the  latter  are  in  the  upper  row,  in  consequence  of  the  duplication  of  the 
fourth  bone,  which  comports  itself  as  in  Carnivora.  The  scaphoid  is  between 
the  two  rows,  as  in  the  tarsus. 

The  Rabbit,  therefore,  only  differs  from  the  archetype  by  the  fusion  of  the 
first  to  the  second  inferior  carpal  bone,  which  sometimes  is  incomplete. 

We  have  thus  demonstrated  the  pentadactylous  composition  of  the  hand  in 
the  domestic  Carnivora  and  Rodents — an  easy  task,  as  these  animals  have  five 
apparent  digits.     We  will  now  pass  to  the  Pig. 

4.  Pig. — This  animal  has  eight  carpal  bones  and  four  complete  digits,  with 
metacarpals  and  phalanges — two  large  and  two  small  (Fig.  82,  c).  There  is  no 
difficulty  in  referring  the  carpus  of  the  Pig  to  that  of  Man  or  the  Carnivora,  and 
from  these  to  the  archetype.  It  suffices  to  find  in  this  creature  a  trace  of  the  fifth 
digit,  in  order  to  place  it  in  the  pentadactylous  type.  Normally,  the  fifth  bone  of 
the  lower  row — the  trapezium — has  no  relation  with  the  bones  of  the  metacarpus  ; 
which  proves  that  the  remainder  of  the  thumb  is  absent.  But  this  thumb  has 
been  found  entirely  developed,  and  having  the  appearance  of  the  other  digits. 
In  Fig.  M  (c'),  this  has  been  shown  in  the  teratological  cases  observed  by 
Joly  and  Lavocat,  and  Goubaux  and  ourselves.  Consequently,  although  the  Pig 
has  been  classed  among  bisculcate  animals  by  certain  zoologists,  yet  it  has  in  the 
anterior  limb  five  digits,  more  or  less  completely  developed. 

5.  Ruminants. — Intended  as  an  organ  of  support,  the  hand  of  Ruminants 
offers  several  fusions  or  abortions,  which  increase  its  solidity  at  the  expense  of 
its  suppleness  and  flexibility.  Thus,  in  the  first  place,  it  appears  more  difficult 
than  in  other  animals  to  find,  materially  or  virtually,  the  elements  of  the  five 
digits. 

Only  six  bones  are  found  in  the  carpus  of  the  0-r,  Sheep,  and  Goat ;  but  the 
study  of  relations  demonstrates  that  there  are  :  abortion  of  the  fifth  bone  of  the 
upper  row  ;  fusion  between .  the  first  and  second,  and  between  the  third  and 
fourth,  and  abortion  of  the  fifth  bone,  of  the  lower  row.  So  that,  in  reality,  there 
are  met  with,  in  the  carpus  of  the  domestic  Ruminants,  the  elements  of  ten 
bones,  with  the  exception  of  two  not  developed  (Fig.  82,  d). 

The  metacarpus  comprises  a  principal  metacarpal — the  inferior  articular  face 
of  which  is  double — and  a  stylif  orm  bone  placed  alongside  its  external  and  internal 
borders.  For  a  long  time,  GeofFroy  Saiut-Hilaire  had  demonstrated  that  the 
principal  metacarpal  is  formed  by  two  metacarpals  brought  together  during  foetal 
life,  and  separated  by  a  more  or  less  incomplete  medullary  septum  during  extra- 
uterine existence.  Besides,  the  isolation  of  the  two  metacarpals — temporary  in  the 
Ox — is  permanent  in  some  other  Ruminants,  such  as  the  Chevrotain  of  Guinea  and 


THE  ANTERIOR   LIMBS.  125 

the  Aquatic  Chevrotain  (Fig.  82,  e).  With  regard  to  the  external  stylet,  it  is 
an  atrophied  metacarpal ;  for  in  some  teratological  instances  it  becomes  elongated, 
and  supports  a  more  or  less  perfect  digit.  In  addition,  in  the  Chevrotain  it  is 
replaced  by  the  metacarpal  and  a  complete  digit  (Fig.  82,  e).  It  is  the  same 
with  the  internal  stylet,  which  is  usually  smaller,  and  embedded  in  a  fibrous  cord 
running  along  the  large  metacarpal ;  it  may,  like  the  external  stylet,  be  converted 
into  a  perfect  metacarpal  (Fig.  82,  P  and  g). 

It  remains  to  demonstrate  the  virtual  existence  of  a  fifth  metacarpal.  Nor- 
mally, no  traces  of  it  are  found  in  the  domestic  Ruminants,  but  it  appears  in 
some  anomalies.  The  museum  of  the  Toulouse  Veterinary  School  possesses  the 
hand  of  a  Lamb,  in  which  it  can  be  seen,  inside  the  internal  stylet,  which  has 
been  transformed  into  a  long  metacarpal — a  small  styliform  bone  which  is 
assuredly  nothing  else  than  the  metacarpus  of  the  thumb  (Fig,  82,  f,  i,).  Here 
is  the  metacarpus  brought  to  the  pentadactylous  type  ;  now  for  the  phalangeal 
region. 

The  digital  region  of  Ruminants  presents  two  perfect  digits  (the  second  and 
third.  Fig.  82,  d),  and  two  rudimentary  digits  reduced  to  one  or  two  small 
phalanges  covered  by  a  horny  plate  (ergot),  situated  behind  the  metacarpo- 
phalangeal articulation.  The  two  rudimentary  digits  may,  in  certain  cases,  be 
reproduced— to  the  right  and  left  of  the  normal  ones — complete  and  suspended  from 
real  metacarpals.  This  was  seen  in  a  specimen  from  a  young  sheep  (Fig.  82,  g)  ; 
and  this  condition  is  normal  in  the  Chevrotain  (Fig.  82,  e),  only  the  lateral 
digits  are  less  voluminous  than  those  appertaining  to  the  principal  metacarpal. 
The  presence  of  the  fifth  digit  is  normally  indicated,  according  to  Joly  and 
Lavocat,  by  a  tuft  or  spike  of  hair  inside  the  carpus,  rather  above  than  below  it. 
Sometimes  it  is  better  marked  ;  for  in  the  specimen  sho^Ti  in  Fig.  82,  f'  a, 
where  the  metacarpal  of  the  thumb  had  appeared,  this  digit  was  represented  on 
the  surface  of  the  skin  by  a  plate  of  horn  in  the  form  of  an  ergot  (f,  a  and  b, 
2).  Otherwise,  in  order  to  dispel  all  doubts,  it  may  be  mentioned  that  Geoff roy 
Saint-Hilaire  studied  a  new-born  Lamb  which  had  five  digits  in  the  anterior 
limb. 

6.  SoUpeds. — In  Solipeds,  there  is  apparently  only  one  digit  enclosed  in  one 
hoof.  Nevertheless,  by  the  aid  of  analogous  facts  to  those  which  have  already 
assisted  us  in  proving  pentadactylism  in  Ruminants,  we  shall  be  able  to  demon- 
strate that  the  hand  of  the  Horse,  Ass,  etc.,  is  no  exception  to  the  general  law. 
Many  anatomists  only  describe  seven  bones  in  the  carpus  of  the  Horse — four  in 
the  upper  row,  three  in  the  lower.  But  it  is  not  rare  to  see  a  pisiform  bone  on 
the  inner  side  of  the  trapezoid,  which  raises  the  number  of  carpal  bones  to  eight. 
And  Bourgelat,  Girard,  Rigot,  and  Goubaux  have  observed  in  the  carpus  of  the 
Horse,  in  addition  to  the  bones  mentioned,  a  similar  piece  alongside  the  external 
bone  of  the  second  row.  Lavocat  considered  this  second  piece  as  the  first  of  the 
inferior  carpal  bones — the  base  of  the  external  digit,  and  that  the  bone  found 
beside  the  trapezoid  was  the  trapezium  or  base  of  the  internal  digit  or  thumb, 
the  trapezoid  being  the  base  of  the  fourth  finger.  The  trapezium  and  trapezoid 
are  shown,  with  the  significance  attributed  to  them  by  Lavocat,  on  the  carpus 
represented  in  Fig.  82  (l  a,  1,  2). 

The  carpus  of  Solipeds  does  not  differ,  then,  from  the  archetype,  except  in  the 
frequent  abortion  of  the  fifth  superior  carpal  bone,  and  the  first  and  fifth  of  the 
lower  tier. 

The  metacarpus  of  Solipeds  comprises  a  large  bone  articulating  with  the 
11 


126  THE  BONES. 

digital  section,  and  two  rudimentary  pieces  on  each  side  of  it,  and  which  are 
really  atrophied  metacarpals  ;  for  in  some  teratological  specimens  they  are  as  long 
as  the  principal  bone,  and  terminate  in  a  diarthrodial  surface  which  articulates 
with  a  perfect  digit  (Fig.  82,  l  b).  At  first  sight,  there  are,  then,  three  meta- 
carpals in  Solipeds. 

With  several  authorities,  and  particularly  Joly  and  Lavocat,  we  have 
admitted  the  duplicity  of  the  large  median  metacarpal  bone,  basing  our  admis- 
sion on  several  considerations  with  regard  to  form  and  relations,  and  especially 
on  certain  anomalies  similar  to  those  represented  in  Fig.  82,  i,  in  which 
is  seen  the  single  digit  of  Solipeds  divided  like  that  of  the  Ox — the  division 
extending  to  the  lower  end  of  that  bone.  But  an  attentive  study  of  the 
metacarpal  region  in  the  Mammalia,  and  notably  in  Pachyderms,  and  of  the 
arrangement  it  offers  in  the  various  fossil  Equidfe,  has  caused  us  to  abandon 
this  opinion.  "We  consider  the  principal  metacarpal  of  Sohpeds  to  be  the  analogue 
of  the  metacarpus  of  the  medius  of  pentadactylous  Mammals.  With  regard  to 
the  anomaly  shown  at  i  and  k.  Fig.  82,  it  should  be  interpreted  as  an  example 
of  division  of  an  organ  normally  single. 

The  Horse,  then,  has  always  three  metacarpals — one  for  the  medius,  the 
index,  and  the  annularis  ;  and  it  remains  to  prove  the  existence  of  two  other 
metacarpals.  Usually,  the  metacarpal  of  the  thumb  is  completely  aborted  ;  but 
yet  the  existence  of  these  bones  is  indicated  by  the  frequent  presence  of  the 
trapezium  at  the  inner  side  of  the  carpus.  Lastly,  as  a  continuation  from  the 
trapezium  there  may  be  found  a  conical  prolongation  (Fig.  82,  L  a,  5),  parallel 
with  the  metacarpal  bone  of  the  index — a  prolongation  which,  because  of  its 
connections,  should  be  regarded  as  the  metacarpal  of  the  thumb. 

With  respect  to  the  metacarpal  of  the  auricularis,  or  little  digit,  we  do  not 
know  of  one  teratological  example  in  which  it  can  be  distinctly  seen.  But  its 
existence  is  virtually  indicated  by  the  presence  of  the  small  external  carpal  bone 
we  have  sometimes  observed,  and  which  was  noted  by  Bourgelat,  Eigot,  and 
Goubaux. 

The  phalangeal  section  only  possesses  the  elements  of  a  single  digit.  But 
besides  the  hoof,  Soliped  animals  have  a  horny  plate  divided  by  a  slight  median 
groove,  and  resting  on  an  elastic  cushion  behind  the  metacarpo-phalangeal  articula- 
tion. This  plate  occupies  the  same  position  as  the  ergots  in  the  Ox  ;  it  has  vessels 
and  nerves  from  the  same  source  as  those  of  the  principal  digit  ;  it  lies  upon  an 
elastic  bed  similar  to  that  belonging  to  that  organ  ;  and  Joly  and  Lavocat  regard 
it  as  the  representative  of  the  phalanges,  which  should  be  continued  with  the 
rudimentary  metacarpals.  Otherwise,  when  one  of  these  metacarpals  is  developed 
into  a  perfect  digit,  the  horny  plate  or  ergot  diminishes  in  volume,  because 
a  portion  of  its  substance  is  carried  to  the  extremity  of  the  supplementary  digit. 
It  -is,  therefore,  easy  to  find  three  digits  in  these  animals,  but  the  thumb  is  more 
difficult  to  render  evident.  However,  the  presence  of  a  trapezius,  and,  much 
more  rarely,  of  an  atrophied  metacarpal  succeeding  it,  would  warrant  the  admis- 
sion that  this  digit  exists,  if  it  were  not  represented  on  the  surface  of  the  skin  by 
the  chestnut — the  horny  plate  situated  on  the  internal  aspect  of  the  forearm. 
The  position  of  this  small  mass  of  horn  above  the  carpus  has  been  invoked 
against  this  signification  ;  but  it  is  easy  to  overcome  this  objection  in  showing,  by 
the  ascending  vessels  and  nerves  of  the  chestnut,  that  this  is  a  displaced  organ  ; 
the  vessels  and  nerves  arise  from  the  same  trunks  that  supply  the  other  digits. 

The  fifth  digit  is  not  absolutely  represented  except  by  its  carpal  base,  which  is 


TEE  POSTERIOR  LIMBS.  127 

often  absent  ;  however,  its  presence  in  a  certain  number  of  instances  allows  it  to 
be  affirmed  that  Solipeds  materially  and  virtually  belong  to  the  pentadactylous 
type.     This  conclusion  applies  a  fortiori  to  all  the  domestic  animals. 

According  to  statistics  drawn  up  by  Cornevin,  the  return  to  the  pentadacty- 
lous type  is  much  more  frequently  manifested,  in  Solipeds,  in  the  anterior  than 
the  posterior  limbs. 

Article  YI. — Posterior  or  Pelvic  Limbs. 

Each  of  these  is  divided,  as  already  noted,  into  four  secondary  regions  :  the 
pelvis,  thigh,  leg,  and  foot. 

Pelvis  (Figs.  83,  84,  85). 
The  pelvis  is  a  kind  of  bony  cavity  formed  by  the  union  of  the  sacrum  with 
two  lateral  pieces — the  ossa  innominata,  or  coxae — which  are  consolidated  with  each 

Fig.  83. 


THE   OSSA    INNOMINATA   (SEEN   FROM   BELOW). 

1,  Iliac  surface  ;  2,  auncular  facet ;  3,  angle  or  crest  of  the  ilium  ;  4,  angle  of  the  haunch  ;  5, 
?eSs.  r;^'  V^"'\T  '^'^'V*"'  '\  °°^  ""^  '^'  '"P'-'°'^  f""-  tl^e  insertion  of  the  rec'tu 
rator)  foramen  ;  11,  sciatic  spine ;   12,  12,  ischiatic  arch,  r  )       ,  ^, 

Other  in  the  inferior  median  line.     The  description  of  the  sacrum  having  been 
ah:eady  given,  it  now  remains  to  speak  of  the  os  inn^ominatum  of  each  side. 

A.  Coxa,  or  Os  Innominatum. 

The  OS  innominatum—2X^o  designated  os  coxa,  os  iliacum,  os  innominatum-is 

a  very  irregularly  shaped  flat  bone,  double  (with  its  fellow  on  the  opposite  side), 

and  directed  obhquely  downwards  and  backwards.     It  is  contracted  in  its  middle 

part,  which  presents  externally  a  deep  cavity-the  cotgloid ;  anteriorly,  where 


128  THE   BONES. 

it  rests  on  the  sacrum,  it  becomes  widened,  as  it  also  does  in  its  posterior 
portion,  which  is  inflected  inwards  to  be  united,  on  the  median  Hne,  with  the 
OS  innominatum  of  the  opposite  side. 

It  is  divided,  in  the  foetus,  into  three  distinct  pieces,  joined  by  cartilage  in 
the  centre  of  the  cotyloid  cavity,  which  they  concur  in  forming.  Although  they 
soon  become  consolidated  into  a  single  piece,  it  is  customary  to  describe  them  as 
so  many  separate  bones  by  the  names  of  ilium,  pubis,  and  ischium. 

Ilium  (Figs.  83, 84). — The  ilium — a  flat  and  triangular  bone,  curved  on  itself, 
directed  obliquely  downwards,  backwards,  and  outwards — forms  the  anterior 
portion  of  the  coxa  which  corresponds  with  the  sacrum.  It  is  the  most  consider- 
able of  the  three  divisions,  and  has  two  faces,  three  borders,  and  three  angles  or 
processes. 

Faces. — The  external  or  superior  face  (Fig.  83),  studded  Avith  some  muscular 
imprints,  is  excavated  on  both  sides,  and  is  named  the  external  iliac  fossa.  The 
internal  or  inferior  face  offers  for  study  :  1.  An  external  portion,  smooth,  and 
crossed  by  some  vascular  grooves  ;  this  is  the  iliac  surface,  which  is  replaced  in 
Man  by  an  excavation  called  the  internal  iliac  fossa.  2.  An  internal  portion, 
roughened  and  uneven,  presents,  posteriorly,  the  auricular  facet — an  irregular 
diarthrodial  surface,  elongated  from  side  to  side,  a  little  oblique  in  front  and 
inwards,  and  responding  to  an  analogous  surface  on  the  sacrum. 

Borders. — The  anterior  border,  or  crest  of  the  ilium,  is  slightly  concave,  and 
bears  a  roughened  lip  for  muscular  insertion.  The  external  border  is  thick, 
concave,  and  furrowed  by  vascular  fissures  ;  it  presents,  inferiorly,  the  nutrient 
foramen.  The  internal  border  is  thin  and  concave,  particularly  in  its  posterior 
part,  which  constitutes  the  great  sciatic  notch. 

Angles. — The  externcd  angle,  or  anterior  and  superior  spinous  2)rocess,  is  thick, 
wide,  and  flat,  and  bears  four  tuberosities  :  two  superior  and  two  inferior.  The 
internal  angle,  or  posterior  and  siqjerior  sp)inous  j^rocess,  represents  a  rugged  tube- 
rosity curved  backwards  and  upwards.  The  posterior — or  cotyloid  angle — is  pris- 
matic and  very  volimiinous.  It  exhibits  :  1.  Behind,  a  wide  concave  articular  facet, 
which  forms  part  of  the  cotyloid  cavity.  2.  Above  this  cavity,  the  supra-cotyloid 
crest,  represented  in  Man  by  the  ischiatic  spine.  This  is  an  eminence  elongated 
from  before  to  behind,  sharp  on  its  summit,  smooth  inwardly,  roughened  out- 
wardly, and  continuous  by  its  anterior  extremity  with  the  internal  border  of  the 
bone.  3.  Outwardly,  two  deep  imprints  for  the  insertion  of  the  rectus  femoris 
muscle.  4.  In'front  and  inwards,  the  ilio-2^ectineal  spine,  a  small  elongated  pro- 
minence forming  the  most  salient  point  of  a  kind  of  ridge  {linea  ilio-pectinea)  that 
insensibly  subsides  above  on  the  inner  face  of  the  ilium,  and  is  continued  below 
by  the  anterior  border  of  the  pubis. 

Of  the  three  angles  of  the  ilium,  the  first  is  also  termed  the  angle  of  the 
haunch,  and  the  second  the  angle  of  the  croup. 

Pubis  (Fig.  83). — Situated  between  the  ilium  and  ischium,  elongated  from 
side  to  side,  flattened  above  and  below,  and  irregularly  triangular,  the  pubis — the 
smallest  of  the  three  divisions — is  divided,  for  convenience  of  description,  into 
two  faces,  three  borders,  and  three  angles. 

Faces. — The  superior,  smooth  and  concave,  concurs  in  forming  the  floor  of 
the  pelvis.  It  shows  one  or  two  nutrient  foramina.  The  inferior  is  roughened, 
and  marked  throughout  its  length  by  a  wide  channel  which  reaches  the  bottom 
of  the  cotyloid  cavity.  This  fissure  lodges  the  pubio-femoral  ligament  and 
a  very  large  vein. 


THE  POSTERIOR   LIMBS. 


129 


Borders. — The  anterior  is  constituted  by  a  thin  rugged  lip,  which  is  curved 
upwards.  The  posterior,  thick  and  concave,  circumscribes  anteriorly  a  wide 
opening,  the  oval,  suhpiiUc,  or  obturator  foramen  ;  it  is  channeled  near  the  coty- 

Fig.  84. 


PELVIS   (ANTERO-LATERAL   VIEW). 

1,  Anterior  iliac  spine  ;  2,  posterior  iliac  spine  ;  3,  shaft  of  the  ilium,  with  the  ilio-pectineal  crest ; 
4,  cotyloid  cavity ;  5,  symphysis  pubis ;  6,  inferior  ischiatic  spine  and  tuberosity. 


loid  angle  by  a  fissure  which  runs  obliquely  inwards  and  downwards.  The 
internal  is  united  with  that  of  the  opposite  bone,  to  form  the  pubic  portion  of 
the  pelvic  symphysis. 

Ayigles.  —  The    ex-  Fig-  85. 

ternal,  also  named  the 
cotyloid  angle,  is  the 
thickest  of  the  three. 
To  it  chiefly  belongs 
the  rugged  depressed 
surface  that  constitutes 
the  bottom  of  the  coty- 
loid cavity.  The  in- 
ternal unites  with  the 
analogous  angle  of  the 
opposite  bone.  The 
•posterior  is  consolidated 
at  an  early  period  with 
the  antero  -  internal 
angle  of  the  ischium,  to 
enclose,  inwardly,  the 
oval  foramen. 

Ischium  (Figs.  84, 
85). — This  is  the  mean, 
in  volume,  of  the  three 
pieces  of  the  coxa.     Situated  behind  the  pubis  and  ilium,  it  is  flattened  above 


PELVIS   (LATERAL   VIEW). 

1,  External  angle  of  the  ilium,  or  anterior  iliac  spine  ;  2,  internal 
angle,  or  posterior  iliac  spine ;  3,  shaft  of  the  ilium  and  ilio- 
pectineal  line ;  4,  cotyloid  cavity,  or  acetabulum  ;  6,  inferior 
ischiatic  spine,  with  tuberosity  behind. 


130  THE  BONES. 

and  below,  and  of  a  quadrilateral  form.  It  offers  for  study  :  two  faces,  four 
borders,  and  four  angles. 

Faces. — The  superior  is  smooth  and  nearly  plane,  and  forms  part  of  the  floor 
of  the  pelvic  cavity.  It  has  a  small  nutrient  foramen  directed  outwards.  The 
inferior  presents  some  rugosities,  clustered  particularly  about  the  symphysis. 

Borders. — The  anterior,  thick  and  concave,  circumscribes  the  oval  foramen 
posteriorly.  The  posterior,  straight  and  directed  obliquely  forwards  and  inwards, 
forms,  with  the  analogous  border  of  the  opposite  bone,  a  large  notch  named  tjie 
ischial  arch.  It  exhibits,  throughout  its  extent,  a  rugged  depressed  lip  (the 
spine),  arising  from  the  side  of  the  inferior  face.  The  external,  thick  and 
concave,  constitutes  the  lesser  ischiatic  notch.  The  internal  is  joined  to  the 
ischium  of  the  other  side,  to  constitute  a  portion  of  the  pelvic  symphysis. 

Angles. — The  antero-externcd,  or  cotyloidean,  is  the  most  voluminous  of  the 
four,  and  affords  for  study  :  1.  An  excavated  diarthrodial  facet,  making  part  of 
the  cotyloid  cavity.  2.  The  posterior  extremity  of  the  supra-cotyloidean  crest, 
limited  by  a  small  transverse  fissure  which  separates  from  the  external  border  of 
the  bone.  The  antero-internal  angle  is  consolidated  with  the  posterior  angle  of 
the  pubis.  The  poster o-external  angle  forms  the  ischial  tuberosity.  This  is  a 
large  prismatic  process  which  looks  upwards,  and  is  prolonged  by  a  salient 
ridge,  elongated  from  before  to  behind,  with  its  sharp  border  turned  outwards 
and  downwards.  The  postero-internal  angle  forms,  with  that  of  the  other 
ischium,  the  summit  of  the  triangular  space  which  constitutes  the  ischial  arch, 
or  pubic  arch  of  some  species. 

The  Coxa  in  General. — This  bone,  the  three  constituent  parts  of  which  we 
have  just  been  studying,  presents  for  consideration,  as  a  whole,  a  middle  portion 
and  two  extremities.  The  middle,  very  much  contracted,  offers,  outwards  and 
downwards,  the  cotyloid  cavity  (or  acetabulum),  which  has  not  yet  been  described, 
because  its  study  does  not  properly  pertain  to  either  of  the  three  regions  of  the 
coxa.  This  cavity  is  intended  to  receive  the  articulating  head  of  the  femur,  and 
represents  the  segment  of  a  hollow  sphere  ;  it  is  circumscribed  by  a  very  salient 
rim,  which  is  thin  at  its  free  margin,  and  widely  notched  on  the  inner  side.  The 
deeper  portion  is  occupied  by  the  roughened  and  depressed  surface  already 
designated  as  the  bottom  of  the  cotyloid  cavity  {fundus  acetabuli),  which 
communicates,  by  the  internal  notch  of  the  rim,  with  the  inferior  groove  of  the 
pubis.  The  anterior  extremity,  flattened  on  both  sides,  and  formed  by  the 
ilium,  rests,  as  has  been  shown,  on  the  sacrum.  The  posterior  extremity, 
flattened  in  an  inverse  sense  to  the  preceding,  is  constituted  by  the  pubis  and 
the  ischium,  and  is  traversed,  from  above  to  below,  by  the  sub-pubic  (or  obturator) 
foramen — the  large  oval  aperture  which  separates  these  two  bones  from  one 
another,  and  perforates  the  floor  of  the  pelvis  ;  this  opening  is  closed  in  the 
fresh  staie  by  muscles. 

The  two  coxae,  by  uniting  in  their  posterior  part,  form  the  articulation  to 
which  has  been  given  the  name  of  ischio-pubic  or  pelric  symphysis ;  thus  united, 
the  two  bones  represent  something  like  a  V  with  the  opening  in  front — a 
circumstance  which  makes  the  lateral  diameter  of  the  pelvis  greater  in  front 
than  behind. 

Structure  and  Development  of  the  Coxa. — To  the  three  centres  of 
ossification  which  constitute  the  coxa,  are  added  two  complementary  centres  : 
one  for  the  anterior  spinous  process  and  spine  of  the  ihum,  another  for  the 
ischial  tuberosity. 


THE  POSTEBIOB  LIMBS.  131 

It  must  be  added  that  there  is,  within  and  in  front  of  the  cotyloid  cavity,  a 
cotyloid  nucleus  analogous  to  the  glenoid  nucleus  of  the  scapula.  This  nucleus, 
comprised  between  the  three  bones  of  the  coxa,  has  been  named  by  Serres  the 
Y-shaped  bone. 

In  youth,  the  different  parts  of  the  coxa  are  very  thick,  and  the  spongy 
tissue  is  abundant,  while  the  compact  is  rare.  The  pubis  is  always  convex  on 
its  two  faces,  and  the  middle  part  of  the  coxa — that  adjoining  the  cotyloid 
cavity — is  of  considerable  thickness,  a  feature  which  much  diminishes  the  extent 
of  the  pelvic  cavity.  As  the  animal  advances  in  age,  however,  the  layers  of 
compact  tissue  increase  in  thickness,  approaching  each  other  as  the  spongy 
substance  is  lessened.  The  pubis  becomes  thinnest,  and  at  an  advanced  period 
of  life  is  sometimes  even  translucid. 

The  compact  tissue  is  always  abundant  in  the  neighbourhood  of  the  cotyloid 
cavity,  as  this  is  the  centre  on  which  converge  all  the  impulsive  efforts  com- 
municated to  the  trunk  by  the  posterior  limbs.  It  is  also  in  this  cavity  that 
ossification  commences. 

B.  The  Pelvis  in  Genekal. 

1.  External  and  Internal  Conformation  of  the  Pelvis. — The  pelvis 
is  a  kind  of  rear  cavity  in  the  form  of  a  cone,  which  prolongs  the  abdominal 
cavity  between  the  sacrum  and  coccygeal  vertebrae. 

It  occupies  the  posterior  part  of  the  trunk,  and,  with  regard  to  its  conforma- 
tion, presents  for  study  an  external  and  internal  surface. 

External  surface. — This  may  be  resolved  into  four  planes  or  faces. 

The  superior  plane  is  slightly  oblique  from  above  to  below,  and  before  to 
behind  ;  its  degree  of  obliquity,  varies.  It  is  contracted  from  before  to  behind, 
and  shows  :  1.  On  the  median  line,  the  spinous  processes  of  the  sacral  and  the 
first  coccygeal  vertebrae.  2.  On  each  side  the  sacral  grooves,  at  the  bottom  of 
which  open  the  supra-sacral  canals. 

The  inferior  pla?ie  is  nearly  horizontal.  Formed  by  the  pubes  and  ischial 
I)ones,  it  presents  from  before  to  behind  :  1.  In  the  middle,  the  ischio-pubic 
symphysis.  2.  On  each  side  the  subpubic  groove,  the  oval  foramina,  and  the 
inferior  face  of  the  ischial  bones.  3.  Quite  externally,  the  cotyloid  cavities,  by 
which  the  pelvis  rests  upon  the  posterior  limbs.  , 

The  lateral  faces  are  oblique  downwards  and  outwards,  and  are  wider  in  front 
than  behind.  They  exhibit :  1.  The  spine  of  the  ilium  and  the  two  anterior 
■spinous  processes.  2.  The  external  iliac  fossa.  3.  The  ischial  arch.  4.  The 
supra-cotyloid  crest  or  ischiatic  spine,  which  presents,  outwardly,  the  surface  of 
insertion  for  the  internal  or  deep  gluteus  muscles.  5.  The  lesser  ischiatic  notch. 
6.  The  ischial  tuberosity. 

Internal  surface. — The  internal  surface  of  the  Horse's  pelvis  cannot  be 
divided  into  two  portions  as  in  Man,  because  the  inner  surface  of  the  iliac  bones 
is  not  hollowed  out  to  form  an  anterior  cavity. 

The  pelvis  of  Solipeds  is,  therefore,  a  simple  conoid  cavity,  in  which  are 
distinguished  four  planes  or  faces,  and  two  apertures  called  the  inlet  and 
outlet. 

The  anterior  openinq,  or  inlet,  is  nearly  circular,  especially  in  the  Mare,  and  a 
little  oblique  downwards  and  backwards.  It  is  limited  above  by  the  inferior  face 
^f  the  first  vertebra  of  the  sacrum  ;  inferiorly,  by  the  anterior  border  of  the 


182 


TEE  BONES. 


pubis  ;  and  on  the  sides  by  a  part  of  the  inner  face  of  the  iliac  bones,  and  also 
the  internal  aspect  of  the  pectineal  crests. 

The  inlet  presents  four  diameters,  a  knowledge  of  which  is  important  in 
obstetrics — a  vertical,  horizontal,  and  two  oblique.  The  first,  the  sacro-pubir, 
extends  from  the  inferior  face  of  the  sacriun  to  the  anterior  border  of  the  pubic 
symphysis  ;  its  mean  length  is  8:^  inches.  The  second,  the  bis-iliac,  is  measured 
from  one  pectineal  crest  or  eminence  to  another  ;  the  mean  of  this  is  H^jj  inches. 
The  two  last  diameters,  the  ileo-sacral,  are  estimated  from  the  inferior  face  of 
the  sacro-iliac  articulation  of  one  side  to  the  ilio-pectineal  eminence  of  the 
other ;   this  is,  on  an  average,  SyV  inches.     These  measurements  irrefutably 

Fig.  86. 


PELVIS   OF   THE    HORSE. 


demonstrate  that  the  inlet  is  not  elliptical  in  the  vertical  direction ;  but  it  may 
happen  that  the  transverse  diameter  is  the  greatest. 

The  posterior  aperture  or  outlet,  situated  at  the  posterior  end  of  the  pelvic 
cavity,  gives  exit  to  the  rectum  and  genital  organs.  It  is  limited  by  the  inferior 
face  of  the  summit  of  the  sacrum,  the  superior  face  of  the  ischial  bones,  the 
supra-cotyloid  crest  or  ischiatic  spine,  and  the  internal  face  of  the  sacro-sciatic 
ligaments.  At  the  outlet  only  two  diameters  are  recognized — a  vertical  and  a 
horizontal.  The  vertical,  extending  from  the  inferior  face  of  the  sacrum  to  the 
superior  face  of  the  ischial  symphysis,  measures  on  an  average  6yV  inches. 
The  horizontal  diameter,  comprised  between  the  two  supra-cotyloid  crests,  is 
7-j^  inches. 

The  superior  face  of  the  pelvic  cavity  is  a  little  concave  from  before  to 


THE  POSTERIOR  LIMBS.  133 

behind  ;  it  has  for  base  the  sacrum,  which  presents  on  each  side  of  the  median 
line  the  subsacral  foramina.  This  part  is  also  called  the  sacral  plane,  or  roof  of 
the  pelvis. 

The  inferior  region,  or  ischio-pubic  plane,  is  formed  by  the  pubes  and  the 
ischial  bones.  It  is  concave  from  side  to  side  ;  its  anterior  border  is  nearly 
straight,  and  its  posterior  border  is  scooped  out  by  a  wide  notch  to  form  the  arch 
of  the  ischium. 

It  has  been  remarked  by  Goubaux,  that  the  portion  of  this  plane  correspond- 
ing to  the  pubis  presents  numerous  varieties.  The  superior  face  of  the  pubis 
may  be  convex  in  its  anterior  moiety,  and  concave  in  its  posterior  ;  or  it  may  be 

Fifr.  87. 


PKLVIS   OF    Tllli   MARE. 

ooncave  before  and  convex  behind,  the  concavity  being  separated  from  the 
convexity  by  a  transverse  ridge.  This  ridge  is  sometimes  represented  by  a  series 
of  small  conical  eminences  ;  at  other  times  this  upper  face  is  disposed  as  a 
smooth  inclined  plate,  directed  backwards  and  upwards,  and  a  kind  of  rim 
surmounts  the  anterior  contour  of  the  oval  foramen.^ 

With  regard  to  the  lateral  faces,  they  are  formed  by  a  small  portion  of  the 
inner  face  of  the  iliac  bones,  and  in  great  part  by  the  sacro-sciatic  ligaments. 

The  foetus  must  pass  through  the  pelvic  canal  during  parturition  ;  it  is, 
therefore,  important  to  know  at  any  time  if  the  female  pelvis  is  of  sufficient 
dimensions  to  allow  the  foetus  to  leave  it.      Pelvimetry  is  the  name  given  to 

'  It  is  necessary  to  be  aware  of  the  frequency  of  these  asperities  on  the  floor  of  the  pelvic 
cavity,  in  order  not  to  arrive  at  false  inductions  when  exploring  the  bladder  per  re,etum. 


134  THE  BONES. 

that  section  of  obstetrics  dealing  with  the  diameters  of  the  pelvis.  These  may 
be  determined  in  several  ways,  which,  in  veterinary  surgery,  daily  receive  the 
sanction  of  experience. 

Some  years  ago  we  indicated  one,^  which  consists  in  measuring  the  horizontal 
distances  between  the  two  haimches  and  the  two  ischiatic  tuberosities,  and  the 
vertical  distance  extending  from  the  coxo-femoral  articulation  to  the  most 
salient  part  of  the  croup  ;  then  to  take  a  fourth  of  the  total  of  the  two  first 
measurements,  in  order  to  obtain  the  transverse  diameter  of  the  inlet,  and 
three-fourths  of  the  third,  to  have  the  vertical  diameter  of  this  opening. 

Saint-Cyr  and  Violet  have  investigated  the  relation  existing  between  the 
height  of  the  Mare  and  the  vertical  diameter  of  the  pelvis,  then  that  of  the 
width  of  the  croup  to  the  bis-iliac  diameter  ;  and  they  have  found  that  the  first 
was  equal  to  0"1515  centimetres  ;  the  second  to  0'4654,  in  a  well-bred  Mare,  to 
0*3945  in  common-bred  Mares.  Consequently,  according  to  the  pelvimetric 
procedure  of  these  authorities,  it  is  sufficient  to  multiply  the  height  of  the  Mare 
by  0-1515  to  have  the  vertical  diameter  of  the  inlet,  and  the  width  of  the  croup 
by  0*4654  or  0"3945,  according  to  circumstances,  to  find  the  transverse  diameter. 
But  this  question  rather  appertains  to  obstetrics.^ 

2.  Differences  in  the  Pelvis  of  the  Sexes. — The  pelvis  of  the  Mare 
exceeds  that  of  the  Horse  in  all  its  dimensions,  but  the  difference  is  most, 
marked  in  the  transverse  diameters  (Figs.  86,  87). 

The  inlet  forms  a  vast  circumference,  when  compared  with  that  of  the  male  ; 
the  pectineal  crests  are  wide  apart,  and  the  distance  separating  the  anterior 
border  of  the  pubis  from  the  lower  face  of  the  sacrum  is  considerable. 

If  the  pelvis  be  viewed  in  its  superior  plane,  it  is  found  that  in  the  Mare  the 
ischiatic  notches  are  very  deep  ;  that  the  internal  border  of  the  ilium  forms  a 
regularly  curved  and  very  concave  line  ;  and  that  the  supra-cotyloid  crests,  or 
ischiatic  spines,  are  widely  separated  from  each  other.  It  is  also  noticed  that 
the  floor  of  the  pelvis  is  wide,  and  that  the  bones  composing  it  tend  towards  the 
same  horizontal  Hne. 

In  the  male,  the  ischiatic  border  is  only  represented  by  a  very  curved  line  ; 
this  line  is  composed  of  two  almost  straight  portions,  which  join  at  an  obtuse 
angle  at  the  origin  of  the  neck  of  the  ilium  ;  the  supra-cotyloid  crests  are 
relatively  near  each  other,  and  bent  towards  the  longitudinal  axis  ;  while  the 
two  moieties  of  the  pelvic  floor  are  directed  very  obliquely  downwards  and 
inwards. 

In  the  Mare,  the  ischial  arch  is  larger  than  in  the  male,  and  forms  a  regular 
curve  uniting  the  two  tuberosities  of  the  same  name.  In  the  Horse,  the  two 
ischial  tuberosities  are  but  little  apart,  and  the  ischial  arch  forms  a  somewhat 
acute  angle,  with  its  borders  nearly  straight. 

Lastly,  when  the  pelvis  is  examined  in  its  inferior  plane,  in  addition  to  the 
features  already  indicated  in  the  ischial  arch,  it  is  found  that  in  the  Mare  the 
obturator  foramina  are  large  and  nearly  circular,  while  in  the  Horse  they  are 
elliptical ;  the  cotyloid  cavities  are  also  further  removed  from  the  ischio-pubic 
symphysis  in  the  female  than  in  the  male. 

The  sacrum  of  the  Mare  has  appeared  to  us,  in  some  individuals  to  be  a  little 
more  arched  from  before  to  behind  than  that  of  the  Horse  ;  but  this  character 
is  not  constant. 

'  Arloing;,  Journal  Vet^rinaire  de  Lyon.     1868. 

=  Saint  Cyr  and  Violet,  Trait€ cV Ohstetrique  VitMnaire,     Paris:  1888. 


Tn:E  POSTERIOR   LIMBS. 


135 


The  following  figures,  relating  to  the  capacity  of  the  pelvis  of  the  Mare  and 
Horse,  confirm  what  has  just  been  enunciated  : — 


Mare. 
Horizontal  Diameters. 

Horse. 
Horizontal  Diameters. 

Between  the  Pectineal 
Crests. 

Between  the  Supra-cotyloid 
Crest,. 

Between  the  Pectineal 
Cre^t8. 

Between  the  Supra-cotyloid 
Crests. 

Inches. 
9| 

Inches. 
7^ 

Inches. 
8t', 

Inches. 

Mare. 
Vertical  Diameters. 

Horse. 
Vertical  Diameters. 

Between  the  Sacrum  and 
Pubis. 

Between  the  Sacrum  and 
Ischium. 

Between  the  Sacrum  and 
Pubis. 

Between  the  Sacrum  and 
Ischium. 

Inches. 
8^ 

Inches. 

Inches. 
8 

Inches. 
6^ 

To  recapitulate,  there  is  observed  in  the  pelvis  of  the  Mare  : — 

1.  A  great  increase  in  the  transverse  diameters. 

2.  A  deep  and  regularly  concave  ischiatic  notch. 

3.  A  wide  and  concave  ischial  arch. 

4.  Circular  obturator  foramina. 

5.  The  cotyloid  cavities  distant  from  the  pubic  symphysis. 

In  the  Ass,  the  inlet  of  the  pelvis  is  a  longer  oval  than  in  the  Horse.  The 
coxse  are  distinguished  by  :  1.  The  less  curvature  of  the  anterior  border  of  the 
ilium.  2.  A  slightly  excavated  external  iliac  fossa.  3.  The  triangular  shape  of 
the  obturator  foramina.  4.  A  short  and  deep  notch  separating  the  external 
border  of  the  ilium  from  the  angle  of  the  haunch.  5.  The  direction  of  the 
tuberosities  of  this  angle ;  they  approach  more  nearly  the  parallelism  with  the 
median  plane  of  the  trunk  than  in  the  Horse.  6.  The  disposition  of  the  rugo- 
sities in  tubercles  for  the  insertion  of  the  suspensory  ligaments  of  the  corpus 
cavernosum  on  the  inferior  face  of  the  ischium.  In  the  Ass,  also,  a  line  which 
would  unite  the  inferior  contour  of  the  auricular  facet  to  the  most  salient 
point  of  the  angle  of  the  haunch,  would  be  parallel  to  the  anterior  border  of  the 
ihum,  while  it  would  be  oblique  on  this  border  in  the  Horse. 

The  inlet  of  the  pelvis  in  the  Hinny  resembles  that  of  the  Ass  ;  in  that  of 
the  Mule,  it  holds  a  middle  place  between  the  Ass  and  Horse.  The  pelvis  of 
the  Hinny  resembles  that  of  the  Ass,  also,  by  the  form  of  the  obturator  foramina, 
the  direction  of  the  anterior  border  of  the  ilium,  and  the  position  of  the  auricu- 
lar facet ;  while  that  of  the  Mule,  on  the  contrary,  resembles  the  pelvis  of  the 
Horse  in  these  features.  The  reverse  is  noted  with  regard  to  the  disposition  of 
the  angle  of  the  haunch. 


Differential  Characters  in  the  Pelvis  op  other  Animals. 

It  is  remarked  :  1.  That  in  all  the  domesticated  animals,  with  the  exception  of  Solipeds 
and  the  Camel,  the  direction  of  the  coxse  is  nearly  horizontal.  2.  That  in  all,  the  ilium  is 
more  oblique  than  in  Solipeds.  3.  That  in  all,  the  transverse  diameters  of  the  pelvis  are 
relatively  less  extensive. 

A.  Ruminants. — In  the  Ox,  the  space  between  the  two  coxae  is  scarcely  so  great  in  front 


THE  BONES. 


as  behind ;  the  ilium  is  not  voluminous,  and  has  only  three  processes  on  the  anterior  and 
superior  iliac  spines.  There  is  no  furrow  on  the  lower  face  of  the  pubes,  and  its  upper  face, 
like  that  of  the  ischium,  is  very  concave.  Thrt-e  eminences  are  seen  on  the  posteio-external 
angle  of  the  ischium.  In  early  life,  the  ischio-pubic  symphysis  shows  an  epiphysary  nucleus 
in  the  middle  of  its  inferior  face.  (The  epiphysis  on  the  inner  border  of  the  ischium  has  been 
considered  by  some  anatomists  as  an  independent  bone,  and  described  by  them  as  the 
inter-ischial  bone). 

Tiie  ischio-pubic  symphysis  has,  in  the  middle  of  its  inferior  face,  a  thick  protuberance, 
flattened  on  each  side  and  very  pointed;  in  early  life  this  is  an  epiphysis,  and  the  epipliysary 
nucleus,  bifurcated  posteriorly,  is  continued  along  the  posterior  border  of  tlie  ischial  bones  as 
far  as  the  ischial  tuberosity,  in  the  form  of  two  marginal  bands. 

The  rim  of  the  cotyloid 
cavity  has  also  three  notches, 
and  the  supra-coryloid  crest, 
or  ischiatic  spine,  is  very  ele- 
vated and  shiirp,  and  but  little 
rou;<hened  outwardly. 

lu  the  Sheep  and  Goat,  the 
coxae  are  yet  more  horizontal 
and  proportionately  longer 
than  in  the  Ox,  but  the  upper 
face  of  ttie  ischium  and  pubis 
i.s  less  concave  ;  the  external  ' 
iliac  fossa  is  separated  into  two 
portions  by  a  small  longi- 
tudinal crest. 

The  pelvis  of  the  Camel  ia 
remarkable  for  its  great  ob- 
liquity, its  shortness,  and  its 
narrowness.  The  anterior 
border  of  the  ilium  is  convex ; 
the  pubis  and  ischium  are 
very  thick;  the  rim  of  the 
cotyhiid  cavity  is  elevated  and 
regular;  the  ischio-pubic  sym- 
physis forms  a  rugged  crest 
outside  the  pelvis;  and  the 
ischial  tuberosity  is  disposed 
in  the  same  manner  as  in  the 
Horse. 

B.  Pig.— Tlie  pelvis  of 
the  Pig  closely  resembles  that 
of  the  smaller  Ruminants  ; 
though  the  crest  of  the  ilium 
is  convex,  and  there  is  no  pro- 
tuberance outside  the  ischio- 
pubic  symphysis, 
height,  and  the  ischio-pubic 


PELVIC   BONES   OF   THE   CAT   AND   RABBIT. 

1,  Pelvis  of  the  Cat.  B,  Pelvis  of  the  Rabbit.  1,  Sacrum  ;  2, 
external  iliac  fossa;  3,  great  ischiatic  notch;  4,  external  border 
of  the  ilium  ;  5,  supra-cotyloid  crest ;  6,  cotyloid  cavity  ;  7, 
crest  above  the  shaft  or  neck  of  the  ilium ;  8,  small  sciatic 
notch;  9,  anterior  extremity  of  the  symphysis  pubis;  10, 
ischium;  11,  ischial  tuberosity;  12,  pubis;  13,  obturator 
foramen. 


The  pelvic  cavity  is   vast,  in  proportion  to  the   animal' 
symphysis  is  late  in  becoming  ossified. 

C.  Dog. — In  the  Dog,  the  transverse  diameter  of  the  pelvis  is  greater  behind  than  in  front ; 
it  is  smallest  between  the  cotyloid  cavities.  The  ilium  is  nearly  vertical,  and  its  external 
face  is  much  depressed.  The  notch  forming  the  ischial  arch  occupies  no  more  than  the 
internal  moiety  of  the  posterior  border  of  the  ischium ;  between  this  arch  and  the  ischial 
tuberosity,  is  a  rugged  lip  directed  downwards.  There  is  no  furrow  on  the  lower  face  of  the 
pubis.     Ossification  of  the  symphysis  is  even  later  than  in  the  Pig. 

D.  Cat. — In  the  Cat,  tlie  ilium  is  proportionately  narrow,  and  the  supra-cotyloid  crest 
liigher,  than  in  the  Dog.  The  posterior  border  of  the  ischium  is  regularly  convex  from 
without  to  within,  and  the  pubic  symphysis  has,  inferiorly,  a  somewhat  salient  crest  (Fig.  88). 

E.  Rabbit. — Pelvis  horizontal ;  ischium  nearly  as  long  as  the  ilium  ;  external  iliac  fossa 
divided  by  a  blunt  longitudinal  crest ;  supra-cotyloid  crest  little  elevated,  straight,  and  ending 
abruptly  behind  by  a  kind  of  notch  ;  rim  of  the  cotyloid  cavity  complete,  or  having  a  slight 
posterior  notch;  ischial  tuberosities  parallel  and  not  divergent,  as  in  the  Dog:  and  posterior 
border  of  the  ischium  concave,  and  very  obliquely  directed  forw-ards  and  inwards  (Fig.  88). 


THE  POSTERIOR  LIMBS.  1S7 


Thigh. 
This  has  for  its  base  one  bone — the  femur. 

Femur  (Figs.  89,  90). 

The  femur  (os  femoris)  is  a  long,  pair  bone  situated  in  an  oblique  direction 
downwards  and  forwards,  between  the  coxa  and  the  principal  bone  of  the  leg  ; 
it  is  divided  into  a  bodt/  (or  shaft)  and  two  extremities. 

Body. — It  is  irregularly  cylindrical,  and  presents  for  study  four  faces.  The 
external,  internal,  and  anterior,  confounded  with  one  another,  are  regularly 
rounded  and  almost  smooth,  showing  only  some  slight  imprints  and  vascular 
grooves.  The  posterior,  nearly .  plane,  and  wider  above  than  below,  offers  :  1. 
Outwardly  and  towards  the  superior  third,  an  uneven  circular  surface.  2.  On 
the  same  level,  and  inwardly,  a  shght  crest,  oblique  downwards  and  outwards. 
3.  In  the  middle,  a  very  extensive  roughened  surface,  having  the  form  of  an 
obliquely  angular  parallelogram,  for  the  attachment  of  the  great  adductor  muscle 
of  the  thigh.  4.  Below  this  surface,  a  large  vascular  groove  running  obliquely 
outwards  and  downwards. 

On  the  limit  of  the  posterior  and  external  faces  are  found,  towards  the  upper 
third,  a  large  rugged,  flattened  eminence,  curved  in  front,  and  termed  the 
subtrochanterian  crest  (or  external  smcdl  trochanter  ^),  because  of  its  position  under 
the  trochanter ;  below,  a  deep  fossa,  named  the  subcondijloid,  garnished  at  its 
bottom  with  asperities,  and  bordered  in  front  by  an  uneven  lip.  On  the  limit 
of  the  posterior  and  internal  face,  there  are  observed  from  above  to  below  : 
1.  The  small  trochanter — a  large  scabrous  tuberosity,  elongated  in  conformity 
with  the  bone,  and  situated  near  its  upper  fourth.  2.  A  marked  longitudinal 
imprint  for  the  attachment  of  the  pectineus  ;  behind,  it  is  confounded  with  the 
surface  for  the  insertion  of  the  great  adductor  muscle  of  the  thigh,  and  presents, 
in  front,  the  nutrient  foramen  of  the  bone.  3.  The  origin  of  the  great  posterior 
fissure.  4.  Quite  below,  a  collection  of  large  tubercles  which  form  the  supra- 
condyloid  crest. 

Extremities. — The  superior  extremit)/  is  sensibly  flattened  before  and  behind, 
and  shows  :  1.  Inwardly,  an  articular  head  which  is  received  into  the  cavity  of 
the  acetabuluna.  This  head  is  separated  from  the  other  portion  of  the  body  by 
a  neck,  which  is,  however,  not  well  marked  in  the  Horse,  and  forms  two-thirds 
of  a  sphere,  excavated  in  its  internal  part  by  a  very  deep  cavity  for  ligamentous 
insertion.  2.  Outwardly,  a  very  large  eminence — the  trochanter  major,  or  great 
{external)  trochanter,  in  which  is  recognized,  as  in  the  trochlea  of  the  humerus  : 
a  summit,  much  more  elevated  than  the  articular  head,  and  shghtly  bent  inwards  ; 
a  convexity,  encrusted  with  cartilage,  and  anterior  to  the  summit,  from  which 
it  is  separated  by  a  narrow  and  deep  notch  ;  a  crest  situated  under  the  convexity, 
and  formed  by  a  tuberculated  surface,  on  which  one  of  the  tendons  of  the  middle 
gluteus  muscle  becomes  inserted,  after  gliding  over  the  convexity.  3.  Posteriorly, 
the  trochanteric  or  digitcd  fossa — a  deep  cavity  studded  with  imprints,  and  circum- 
scribed, outwardly,  by  a  salient  lip  {trochanteric  ridge),  which  descends  vertically 

'  This  is  tlie  third  trochanter  of  Cuvier,  and  takes  the  place  of  the  external  and  superior 
branch  of  the  linea  axpera  of  Man.  (It  is  the  external  small  trochanter  of  Percivall,  and  the 
middle  trochanter  of  Leyh  ) 


138 


THE  BONES. 


from  the  summit  of  the  trochanter  to  the  posterior  face  of  the  bone,  where  it 
gradually  subsides. 

The  [inferior  extremity  is  flattened  before  and  behind  ;  consequently,  its  laro-er 
axis  crosses  at  a  right  angle  that  of  the  upper  extremity.  It  is  distinguished  by 
the  presence  of  tzvo  condyles  and  a  trochlea.  The  two  condyles,  placed  behind, 
one  beside  the  other,  articulate  with  the  superior  extremity  of  the  tibia.  They 
are  separated  by  a  deep  depression  designated  the  intercondyloid  fossa,  which 
lodges  the  spine  of  the  tibia  and  the  interosseous  ligaments  of  the  femoro-tibial 


Fig.  89. 


Fig.  90. 


LEFT   FEMUR    (ANTERIOR   VIEW). 

1,  Head ;  2,  2,  trochanter  major,  with  its 
crest ;  3,  trochanter  minor,  subtrochan- 
terian  crest,  or  third  trochanter;  4,  in- 
ternal trochanter  ;  5,  notch  for  insertion 
of  ligamentum  teres  ;  7,  8,  tuberosities 
for  tendinous  and  ligamentous  insertion  ; 
9,  trochlea. 


LEFT   FEMUR   (POST^IOR    VIEW). 

Head  ;  2,  trochanter  major  ;  3,  trochanter 
minor ;  4,  internal  trochanter ;  5,  fossa 
for  insertion  of  ligamentum  teres ;  6, 
trochanteric  fossa;  7,  8,  tuberosities;  9, 
fossa  for  the  insertion  of  the  external 
meniscus;  10,  supra-condyloid  fossa ;  11, 
condyles. 


articulation.  The  external  condyle  bears,  outwardly,  two  fossag — one  superior,  for 
ligamentous  insertion ;  the  other,  inferior,  for  muscular  attachment.  The 
internal  condyle  presents,  posteriorly  and  inwardly,  near  the  posterior  extremity 
of  the  intercondyloid  notch,  a  roughened  depression  for  the  insertion  of  the 
fibro-cartilaginous  meniscus  interposed  between  the  external  condyle  and  the 
corresponding  articular  plane  of  the  tibia.  It  is  surmounted  outwardly — on 
the  side  opposite  to  the  intercondyloid  notch — by  a  large  tubercle  for  insertion. 
The  trochlea,  a  wide  pulley  on  which  the  patella  glides,  is  situated  in  front  of 


THE  POSTERIOR   LIMBS. 


139 


Fig.  91. 


the  condyles.  It  is  slightly  oblique  downwards  and  inwards,  and  appears  to 
continue  in  front  the  intercondyloid  notch.  Of  the  two  lips  which  border  its 
cavity  laterally,  the  internal  is  the  thickest  and  the  most  prominent.  Between 
the  external  and  the  corresponding  condyle,  is  seen  a  digital  fossa  for  muscular 
insertion. 

Structure  and  development. — The  femur,  very  spongy  at  its  extremities,  is 
developed  from  four  principal  centres  of  ossification  :  one  for  the  body,  another 
for  the  articular  head,  the  third  for  the  trochanter,  and  the  last  for  the  inferior 
extremity  alone. 

The  femur  of  the  Ass  offers  several  differential  characters,  the  principal  of 
which  have  reference  to  the  length  of  the  neck,  the  development  of  the  third 
trochanter  (trochanter  minor),  and  the  curvatures  of  the 
diaphysis.  The  greater  length  of  the  neck  causes  the 
internal  trochanter  to  be  some  distance  from  the  hori- 
zontal plane  on  which  the  inner  face  of  the  bone  lies  ; 
in  the  Horse  this  trochanter  is  always  in  contact  with 
the  plane.  The  small  trochanter  is  less  developed  than 
in  the  Horse,  as  may  be  seen  on  laying  the  bone  on  its 
external  border ;  for  the  femur  of  the  Ass  rests  by  the 
trochanter  major  and  external  condyle,  while  in  the  Horse, 
it  lies  on  the  latter  and  the  subtrochanteric  crest.  With 
regard  to  the  curvatures,  there  is  remarked  a  slight 
diminution  in  that  which  carries  the  head  of  the  bone 
backwards,  and  a  slight  increase  in  the  twist  of  the 
diaphysis  around  its  longitudinal  axis,  which  alters  the 
equilibrium  of  the  bon*  so  that  it  is  impossible  to  have 
it  in  stable  equilibrium  when  it  rests  on  the  trochanter 
major,  head,  and  inner  lip  of  the  trochlea  ;  this  is  easily 
accomplished  with  the  femur  of  the  Horse. 

By  the  dimensions  of  the  neck  and  internal  trochanter, 
the  femur  of  the  Hinny  and  Mule  holds  a  middle  place 
between  their  progenitors  ;  while  in  the  development  of 
the  trochanter  major,  and  the  degree  of  torsion  around 
its  longitudinal  axis,  the  femur  of  the  Hinny  much  resembles  that  of  the  Ass, 
and  the  Mule  that  of  the  Horse,  though  the  conditions  of  equilibrium  always 
remain  the  same  as  in  the  latter. 


SECTION   OF   LEFT   FEMUR, 
SHOWING   ITS  STRUCTURE. 


Differential  Characters  in  the  Thigh-bone  of  the  other  Animals. 

In  all  the  domesticated  animals  except  Solipeds,  the  femur  tends  to  become  curved  longi- 
tudinally, prismatic,  and  triangular;  the  posterior  face  contracts, and  the  surfaces  for  insertion 
that  it  presents  gradually  approach  each  other,  until  they  become  confounded,  and  form  a 
linea  aspera  in  certain  species.  The  head  is  more  distinct ;  the  internal  trochanter  is  a  rough 
tubercle,  and  is  joined  to  the  large  trochanter  by  an  oblique  ridge  ;  the  large  trochanter  sub- 
sides, and  forms  a  single  mass,  the  summit  and  convexity  of  which  are  confounded ;  the  third 
trochanter,  the  fossa,  and  the  supra-condyloid  crest  are  more  or  less  effaced.  In  addition  to 
these  modifications,  there  are  others  special  to  each  species. 

A.  Rvuninants.— In  the  Ox,  there  is  no  subtrochanteric  crest ;  the  supra-condyloid  fossa 
is  shallow,  and  the  crest  little  noticeable.  The  head  is  well  detached,  and  has  its  centre 
excavated  by  a  shallow  fossa  of  insertion.  The  trochlea  is  narrow,  and  its  inner  border  ascends 
much  higher  on  the  anterior  face  of  the  bone  than  the  external. 

In  the  Sheep  and  Goat,  the  general  form  of  the  femur  resembles  that  of  the  Ox.  It  is 
observed,  however,  that  the  body  is  slightly  curved  backwards ;  that  the  supra-condyloid  fossa 


140 


THE  BONES. 


is  nearly  obliterated ;  that  the  trochantir  has  subsiiled  nearly  to  a  level  with  the  articulaJ 
head;  and  that  the  trochha  is  circumscribed  by  two  equal-sized  lips. 

The  femur  of  the  Camel  more  nearly  resembles  that  of  Man.  It  is  long,  slender,  and  curved 
backwards.  The  body  is  prismatic  in  its  middle  portion,  and  the  two  branches  of  the  linea 
aspera  meet  in  the  middle  and  diverge  towards  the  ends.  Tlie  articular  head  is  very  much 
separated  from  the  trochanter  major,  which  is  below  the  level  of  tlie  most  prominent  part  of  the 
head.  Tiie  internal  condyle  is  smaller  than  the  external,  and  the  trochlea  is  narrow,  while  its 
lips  are  equal. 

B.  Pig. — In  the  femur  of  the  Pig,  there  is  also  noticed  a  supra-condyloid  fossa,  but  it  is 

wide  and  sliallow  ;  the  rugosities  of  the  posterior  face  are  replaced  by  some  salient  lines  ;  the 

trochanter  major  is  on  a  level  with  the  heail;  the  latter  is  supported  by  a  somewhat  constricted 

neck,andissituated  within,  and  in  front  of,  the  trochanter  major.    This  hitter  disposition  changes 

the  direction  of  the  great  axis  of  the  superior  extremity, 

which  fibliquely  crosses  that  of  the  inferior  extremity. 

C.  Camivora. — In  the  Dog  and  Cat,  the  femur  is 
long  and  curved  like  a  bow.  Tlie  rugged  surfaces  of  the 
posterior  face  are  confounded,  and  form  two  crests  repre- 
senting the  linea  aspera  of  the  human  femur.  These 
crests  do  not  lie  against  each  other  in  the  middle  portion 
of  the  bone — they  are  merely  parallel ;  tlien  they  diverge 
above  and  below,  to  terminate  beneath  the  great  and 
small  trochanters,  and  above  the  two  condyles.  The 
trochanter  major  is  not  so  high  as  the  particular  head. 
The  femur  of  Carnivora  is  also  distinguished:  1.  By 
the  complete  absence  of  the  third  trochanter  and  the 
supra-condyloid  fossa — this  last  being  replaced  by  a 
small  tubercle,  which  terminates  below  the  external 
brinch  of  the  linea  aspera.  2.  By  the  marked  constriction 
and  length  of  the  neck  supporting  the  articular  head. 
3.  By  the  depth  of  the  digital  fossa. 

In  the  Cat  and  Rabbit  are  found  small  bony  nodules, 
embedded  like  sesamoids  m  the  substance  of  the  lateral 
ligaments  of  the  femoro-tibial  articulation.  After  mace- 
ration, liiey  often  adhere  to  the  condyles  of  the  femur. 

D.  Rodents.— The  femur  of  the  Rabbit  resembles 
that  of  the  Dog.  It  is  flat  before  and  behind,  and  more 
bent  inwards  at  its  upper  end.  The  internal  trochanter 
appears  as  a  crest,  and  not  a  tubercle ;  and  the  sub- 
trochanteric crest  is  very  developed,  and  placed  im- 
mediately below  the  trochanter  major. 

Leg. 

This  has  for  its  base  three  bones  :  the  tibia, 
peroneus  {pv  fibula),  and  the  rotiila  {or  patella). 


A.  -       B 

rEMtJR    OF    THE    OAT    AND    RABBIT. 

L,  Femur  of  the  Rabbit.  B,  Femur 
of  the  Cat.  1,  Diaphysis  ;  2,  head  ; 
3,  internal  trochanter;  4,  trochanter 
major  ;  5,  subtrochanteric  crest ; 
6,  trochlea;  7,  internal  condyle; 
8,  sesamoid  imbedded  in  the  internal 
ligament  of  the  femoro-tibial  articu- 
lation. 


1.  Tibia  (Fig.  93). 

The  tibia  is  a  long  prismatic  bone,  thicker  at  the  superior  than  the  opposite 
extremity,  and  situated  between  the  femur  and  the  astragalus,  in  an  oblique 
direction  downwards  and  backwards,  constituting  the  principal  portion  of  the 
leg.     It  has  a  body  or  shaft,  and  two  extremities. 

Bod//.— Thk  offers  for  study  three  faces  and  three  borders.  The  faces  are 
wider  above  than  below.  The  external  is  almost  smooth,  and  is  concave  in  its 
superior  part  and  convex  below,  where  it  deviates  to  become  the  anterior.  The 
internal,  slightly  convex  on  both  sides,  presents,  superiorly,  deep  imprmts  for  the 
attachment  of  the  adductor  muscles  of  the  thigh  and  the  semitendinosus.  The 
posterior,  nearly  plane,  is  divided  into  two  triangular  surfaces  :  one,  superior, 


THE  POSTERIOR  LIMBS. 


141 


Fig.  93. 


slightly  roughened,  serves  for  the  attachment  of  the  popliteus  muscle  ;  the  other 

inferior,  much  more  extensive,  is  furrowed  into  numerous  longitudinal  crests, 

which  give  attachment  to  the  perforans  muscle.     On  the  Hmit  of  these  two 

surfaces  is  remarked  the  nutrient  foramen  of  the  bone. 

The  borders  are  distinguished  as  anterior,  external,  and 

internal.     The  first  is  rounded,  and  not  very  sahent  in  its 

inferior  two-thirds  ;    it  forms,   in  its   superior   third,  a 

curved  crest,  with  the  concavity  external,  which  joins  the 

anterior  and  superior  tuberosity  of  the  bone  ;    this  has 

received  the  name  of  the  tibial  crest.     The  external  border 

is  very  thick  and  concave  above,  where  it  constitutes,  in 

common  with  the  fibula,  the  tibial  arch.     The  internal  is 

also  very  thick,  straight,  and  provided  superiorly  with  some 

salient  tubercles  to  which  the  popliteus  is  attached. 

Extremities. — The  superior  extremity,  the  most  volumi- 
nous, is  formed  by  three  tuberosities — an  anterior  and  two 
lateral,  which  are  external  and  internal.  The  first,  the 
smallest,  is  a  rugged  process  continuous  with  the  tibial 
crest,  and  separated  from  the  external  tuberosity  by  a 
wide  and  deep  groove,  into  which  passes  a  tendinous  cord  ; 
it  is  excavated,  in  front,  by  a  vertically  elongated  fossa, 
which  lodges  the  middle  ligament  of  the  patella.  The 
externcd  tuberosity,  medium  in  size  and  the  most  detached, 
has  outwardly  an  articular  facet  for  the  head  of  the  fibula. 
The  internal  tuberosity,  the  largest  and  least  detached, 
presents  :  on  the  sides,  ligamentous  imprints  ;  behind,  a 
small  tubercle  which  gives  attachment  to  the  posterior 
crucial  ligament  of  the  femoro-tibial  articulation.  The 
superior  face  of  the  two  lateral  tuberosities  is  occupied  by 
two  large,  irregular,  and  undulated  articular  surf  aces,  which 
respond  to  the  condyles  of  the  femur,  through  the  medium 
of  the  two  meniscus-shaped  fibro-cartilages  interposed 
between  the  two  bones.  Of  these  two  surfaces,  the  ex- 
ternal is  always  the  widest,  because  it  serves,  by  its  posterior 
part,  for  the  gliding  movements  of  the  popliteal  tendon. 
They  are  separated  from  each  other  by  the  tibial  spine — a 
conical  articular  eminence,  divided  into  two  lateral  parts 
by  a  groove  for  insertion  excavated  at  its  base  ;  and  in  front 
by  two  lateral  facets  for  the  insertion,  anteriorly,  of  the 
two  inter-articular  cartilages  ;  it  is  bordered  behind  by 
another  fossa,  which  receives  the  posterior  insertion  of  the 
internal  meniscus. 

The  inferior  extremity,  flattened  behind  and  before,  ex- 
hibits an  articular  surface  moulded  on  the  pulley  of  the 
astragalus,  and  two  lateral  tuberosities.  The  articular 
surface  is  formed  by  two  deep  cavities,  oblique  forwards  and  outwards,  and 
separated  by  a  median  tenon  which  terminates  posteriorly  by  a  very  prominent 
projection,  on  which  the  bone  rests  when  it  is  made  to  stand  vertically  on  a  hori- 
zontal plane.     The  external  tuberosity  ^  projects  but  little,  and  is  traversed  in  ItB 

*  The  external  malleolus  of  Man. 
12 


POSTERIOR   VIEW   OP 
RIGHT    TIBIA. 

Tibial  spine  ;  2,  fossa 
for  the  insei'tion  of  the 
internal  meniscus ;  3, 
external  tuberosity 
with  articulation  for 
the  fibula  ;  4,  fossa  for 
the  insertion  of  exter- 
nal meniscus ;  5,  fibula, 
forming  with  the  tibia 
the  tibial  arch;  6, shaft, 
or  body  of  the  tibia; 
7,  8,  external  and  in- 
ternal malleoli,  inferior 
tuberosities,  or  lateral 
processes  of  the  tibia; 
9,  articular  trochleas 
with  a  median  ridge, 
for  articulation  with 
the  astragalus. 


142 


THE  BONES. 


LEG-BONES   OF   THE   MULE,    WITH   THE 
FIBULA   COMPLETELY    DETACHED. 

I,  Nutrient  foramen  ;  2,  insertion  sur- 
face for  the  perforans ;  3,  insertion 
surface  for  the  popliteus ;  4,  tibial 
ridge ;  5,  fossa  for  the  insertion  of 
the  anterior  crucial  ligament;  6,  in- 
ternal articular  surface;  7,  external 
articular  surface  ;  8,  tubercle  for  the 
insertion  of  the  posterior  crucial  liga- 
ment ;  9,  fossa  for  the  insertion  of 
the  internal  meniscus ;  10,  tibial 
crest ;  11,  internal  and  inferior  tu- 
berosity; 12,  external  and  inferior 
fissure  of  the  tuberosity;  13,  pos- 
terior prominence  formed  behind  by 
the  median  spur  of  the  inferior  articu- 
lar surface  ;'  14,  superior  extremity 
of  the  fibula  articulating  with  the 
tibia;  15,  the  body  ofthe  fibula — com- 
pletely developed  in  this  specimen. 


middle  by  a  vertical  fissure.  The  infernal 
tubcrosif//,^  better  defined,  is  margined  pos- 
teriorly by  an  oblique  channel. 

Structure  and  development. — The  tibia  is 
very  compact  in  its  inferior  portion,  and  is 
developed  from  five  chief  centres  of  ossifica- 
tion. The  body  is  formed  by  one  and  the 
superior  extremity  by  two,  the  anterior  tuber- 
osity having  one  of  these  ;  the  last  develops 
the  whole  of  the  inferior  extremity  of  the  bone, 
except  the  external  tuberosity,  which  is  de- 
veloped from  a  separate  nucleus,  that  at  an 
early  period  becomes  fused  with  the  principal 
one  of  the  epiphysis. 

The  tibia  of  the  Ass  is  remarkable  for 
the  more  or  less  perfect  equality  of  the  promin- 
ences around  the  inferior  articular  surface,  so 
that  this  bone  can  sometimes  lie  in  stable 
equilibrium  on  its  inferior  extremity.  It  is 
also  distinguished  from  that  of  the  Horse  by  : 

1.  The  more  or  less  marked  obliquity  of  the 
grooves  which  articulate  with  the  astragalus. 

2.  The  disposition  of  the  oblique  prominence 
coursing  the  surface,  for  the  insertion  of  the 
popliteus  muscle.  3.  The  great  development 
of  the  imprint  for  the  semitendinosus  muscle, 
and  the  crest  above  the  groove  for  the  oblique 
flexor  tendon  of  the  phalanges. 

The  tibia  of  the  Mule  and  Hinny  more 
particularly  resembles  that  of  the  Horse. 

2.  Fibula,  ok  Peroneus  (Fig.  94). 

A  small,  undeveloped  bone,  elongated  and 
styloid  in  shape,  situated  outside  the  tibia, 
and  extending  from  the  superior  extremity  of 
that  bone  to  the  middle  or  lower  third  of  its 
body. 

The  middle  portion  of  the  fibula  is  thin 
and  cylindrical,  and  forms  above,  in  common 
with  the  external  border  of  the  larger  bone, 
the  tibial  arch.  Its  superior  extremity,  wide 
and  flattened  on  both  sides,  has  received  the 
name  of  head.  It  offers,  on  its  internal  face, 
a  diarthrodial  facet  to  articulate  with  the 
external  and  superior  tuberosity  of  the  tibia  ; 
on  its  external  face  it  shows  ligamentous  im- 
prints.    The  infei'ior  extremity  of  the  fibula 

*  The  internal  malleolus. 


THE  POSTEBIOB  LIMBS. 


143 


terminates  in  a  blunt  point,  and  gives  attachment  to  the  ligamentous  fibres  that 
unite  it  to  the  tibia. 

The  fibula  is  sometimes  continued  to  the  external  inferior  tuberosity  of  the 
latter  bone,  with  which  it  is  confounded  ;  and  as  this  tuberosity  always  forms  a 
special  nucleus,  particularly  in  the  young  Foal,  it  seems  natural,  having  regard 
to  the  disposition  observed  in  Pachyderms  and  the  Carnivora,  to  consider  it  as  the 
inferior  extremity  of  the  fibula  fused  to  the  tibia.  In  these  animals,  indeed,  the 
tuberosity  or  external  maleolus  is  formed  by  the  inferior  extremity  of  the  fibula. 

Structure  and  development. — This  bone  is  very  compact,  and  apparently 
developed  by  a  single  nucleus  of  ossification  ;  though,  in  reality,  there  are  two, 
one  of  which  is  for  the  head  of  the  bone. 

3.  Patella  (Figs.  95,  96). 

A  small,  short,  and  very  compact  bone,  situated  in  front  of  the  femoral 
trochlea,  and  annexed  to  the  tibia,  to  which  it  is  attached  by  three  extremely  solid 
ligamentous  bands. 

The  small  polyhedron  which  it  represents  only  offers  for  study  three  faces  : 


PATELLA   OF   THE   HORSE   (SUPERIOR   AND 
POSTERIOR   FACES). 

1,  Superior  face  ;  2,  posterior  articular  face ; 
3,  external  border. 


PATELLA  OF  THE  HORSE  (ANTERIOR  FACE). 

1,   Anterior   face ;    2,  external   border ;    3, 
internal  border. 


the  superior,  roughened,  and  serving  for  the  insertion  of  the  triceps  cruralis  and 
rectus  muscles  ;  the  anterior,  convex  and  irregular  ;  and  the  third,  the  posterior, 
moulded  on  the  femoral  trochlea,  to  which  it  is  but  imperfectly  adapted.  In  the 
fresh  state,  however,  the  articular  surface  formed  by  the  latter  face  is  completed 
by  a  fibro-cartilaginous  apparatus,  which  will  be  noticed  when  describing  the 
femoro-tibial  articulation.  This  articular  surface  is  composed  :  1.  Of  a  median 
ridge,  which  occupies  the  bottom  of  the  trochlear  cavity.  2.  Of  two  depressed, 
gliding,  lateral  facets  on  the  sides  of  this  cavity  ;  the  internal  facet  is  always 
larger  than  the  external — a  disposition  which  permits  the  patella  of  one  hmb  to 
be  distinguished  from  that  of  the  other. 

The  Patella  of  the  Ass  is  usually  narrower  than  that  of  the  Horse,  but  this 
feature  would  scarcely  permit  of  its  being  distinguished  from  that  of  the  other 
domestic  Equidae. 


144 


THE  BONES. 


Fig.  97. 


Differential  Characters  in  the  Leg-bones  op  the  other  Animals. 

In  the  leg-bones  there  is  observed,  in  the  various  domesticated  animals,  differences  analo- 
gous to  those  mentioned  as  existing  in  the  forearm  of  the  pectoral  limb.  More  particularly 
is  til  is  the  case  with  regard  to  the  development  of  the  fibula.  The  relations  existing  between 
the  development  of  that  bone  and  the  number  of  digits,  is  less  marked  than  that  which  exists 
between  the  development  of  the  ulna  and  the  division  of  the  digital  region.  Thus,  in  Rumi- 
nanta  the  fibula  is  only  represented  by  its  inferior  nucleus  of  ossification,  although  there  are 
two  apparent  and  free  digits.     In  these  animals  the  patella  is  also  very  narrow  ;  and  in  all  the 

domesticated  species  except  Solipeds,  tlie  articular 
grooves  in  the  lower  end  of  the  tibia  are  directed  im- 
mediately from  before  to  behind. 

A.  Ox,  Sheep,  Goat.— In  the  Ox,  the  tibia  is 
short ;  it  is  longer  in  the  Goat  and  the  Sheep.  The 
tibia  of  these  animals  is  remarkable  for :  1.  The  absence 
of  the  lateral  facet  on  the  supero-external  tuberosity. 
2.  The  absence  of  a  vertical  fossa  on  the  anterior  tuber- 
osity. 3.  The  absence  of  roughened  lines  on  the  pos- 
terior face.  4.  The  obliquity  downwards  and  inwards 
of  the  inferior  articular  surface.  The  most  salient  point 
of  this  surface  is  the  anterior  extremity  of  the  middle 
tenon. 

The  body  of  the  fibula  and  its  upper  extremity 
are  replaced  by  a  fibrous  cord,  which  is  sometimes 
ossified  wholly  or  in  part,  and  may  then  resemble  the 
fibula  of  Solipeds.  The  inferior  extremity  forms  a 
small  isolated  bone  (the  tamal  coronoid  bone  of  some 
authorities),  articulating  in  one  direction  with  the  tibia, 
and  in  another  with  the  calcis  and  astragalus. 

B.  Camel The  tibia  of  the  Camd  is  very  long. 

slightly  bent  outwards  at  its  upper  end,  and  inwards 
at  the  lower  end.  The  tibial  crest  is  high  and  sharp. 
The  posterior  face  shows  only  one  roughened  line 
limiting  the  popliteal  surface. 

C.  Pig.— In  the  Pig,  the  fibula  is  flattened  on  both 
sides,  extends  the  whole  length  of  the  leg,  and  is  united 
to  the  tibia  by  its  two  extremities  :  above,  by  a  diar- 
throdial  facet ;  below,  by  an  interosseous  ligament. 
It  is  developed  from  three  ossifying  centres;  the  in- 
ferior articulates  with  the  calcis  and  astragalus. 

D.  Dog,  Cat. — In  Carnivora,  the  tibia  is  long  and 
slender,  and  presents  a  salient  anterior  crest.  The 
fibula  is  also  as  long  as  the  tibia,  and  is  united  to 
that  bone  at  three  points :  at  the  two  extremities  by 
articular  surfaces,  in  the  inferior  third  and  middle  by 
an  interosseous  ligament. 

E.  Rabbit.  The  leg-bones  of  this  animal  much 
resemble  those  of  Carnivora,  diflering  only  in :  1.  More 
pronounced  flattening  of  the  tibia  on  each  side  at  its 

upper  end,  and  before  and  behind  inferioily.     2.  The  slightly  salient  malleoli.     3.  The  fibula, 
which  is  fused  with  the  tibia  in  its  lower  third. 


LEG-BONES  OF    THE   RABBIT    AND   CAT. 

A,  Boues  of  the  Rabbit.  B,  Bones  of 
the  Cat.  1,  Diaphysis  of  the  tibia ; 
2,  crest  of  the  tibia;  3,  internal 
malleolus  or  tuberosity  of  the  in- 
ferior extremity  of  the  tibia ;  4, 
anteiior  extremity  of  the  median 
tenon  on  the  inferior  articular  sur- 
face of  the  tibia ;  5,  fibula  ;  6,  ex- 
ternal malleolus  or  tubei'osity. 


Posterior  Foot. 

This  region,  which  bears  the  o;reatest  resemblance  to  the  same  region  in  the 
anterior  limb,  comprises  three  subdivisions— the  tarsus,  the  metatarsus,  and  the 
digital  region. 

1.  Bones  of  the  Tarsus  (Figs.  98,  99). 
These  are  short,  very  compact  bones,  six  or  seven  in  number,  and  situated 


THE  POSTERIOR   LIMBS. 


145 


between  the  inferior  extremity  of  the  tibia  and  the  superior  extremity  of  the 
metatarsal  bones  ;  they  are  arranged,  like  the  bones  of  the  carpus,  in  two  tiers — 
a  superior  and  an  inferior. 

The  superior  row  only  comprises  two  bones, 
the  largest ;  these  are  the  astragalus  and  the 
calcaneum  (or  calcis).  The  inferior  row  is  formed, 
outwardly,  of  the  cuboides  alone  ;  inwardly  and 
anteriorly,  it  is  subdivided  into  two  secondary 
rows,  the  superior  of  which  is  constituted  by  the 
scaphoides,  and  the  inferior  by  the  large  and  small 
cuneiform  bones.  The  last  is  sometimes  divided 
into  two,  in  which  case  there  are  three  cunei- 
forms ;   then  the  total  number  of  the  bones  is 


Astragalus. — An  irregular  cubical  bone,  situ- 
ated in  front  of  the  calcis,  between  the  tibia 
and  the  scaphoid,  and  divided  into  Jive  faces  : 
1.  A  superior  and  anterior,  formed  as  an  articular 
pulley  to  correspond  with  the  inferior  extremity  of 
the  tibia.  This  pulley — oblique  from  above  down- 
wards, forwards,  and  outwards — may  be  considered 
as  the  type  of  the  most  perfect  trochlea  in  the 
body  ;  it  forms  with  the  median  plane  of  the  body 
an  angle  of  from  12°  to  15°.  Its  borders  are 
slightly  spiral,  the  inner  being  more  prolonged 
backwards  than  the  external ;  its  groove  receives 
the  median  tenon  of  the  tibia,  and  its  two  ridges 
or  lips  fit  into  the  lateral  furrows  of  that  bone  ; 
the  two  lips  are  deeply  implanted  in  the  lateral 
grooves,  and  their  two  fossae  are  hollowed  out  of 
their  lower  extremity,  to  admit  the  end  of  the 
principal  bone  during  flexion  movements,  2.  An 
inferior  face,  occupied  by  a  slightly  convex  articu- 
lar surface  articulating  with  the  scaphoid  ;  this 
surface  is  notched  outwardly  by  an  excavation  for 
ligamentous  insertion  ;  behind  the  internal  ex- 
tremity of  this  furrow,  the  articular  face  is  cut 
in  such  a  manner  as  to  present  two  facets  inclined 
towards  each  other,  and  separated  by  a  sharp 
ridge.  3.  A  posterior  face,  irregular,  cut  into  three 
or  four  diarthrodial  facets  adapted  for  similar 
facets  on  the  calcis,  and  which  are  separated  by 
a  wide,  rugged  excavation  ;  the  middle  facet  is 
elliptical,  almost  vertical,  slightly  convex,  and  is 
the  largest.  4.  An  external  face,  covered  with 
imprints  for  the  tibo-tarsal  ligaments.  5.  An 
internal  face,  provided  below  with  a  small  tubercle 
for  insertion,  and,  posteriorly,  with  a  badly  defined 
sinuous  furrow  for  the  tendon  of  the  oblique  flexor 
muscle  of  the  phalanges  (Fig.  99). 


left  hind  foot  (external 
aspect). 

1,  Tibia  ;  2,  summit  of  calcis  or  cal- 
caneum ;  3,  astragalus  ;  4,  cuboid; 
5,  scaphoid ;  6,  cuneiform  mag- 
num ;  7,  large  metatarsal  bone  ; 
8,  small  metatarsal  bone  ;  9,  suf- 
fraginis,  proximal,  or  first  pha- 
lanx ;  10,  sesamoid  bones;  11, 
coronary,  second,  or  middle  pha- 
lanx ;  12,  pedal  bone,  or  third  or 
distal  phalanx;  14,  navicular 
bone  ;  15,  basilar  process  of  pedal 
bone. 


146 


THE  BONES. 


Calcaneum,  or  Calcis  (Figs.  98,  99,  100,  101).-A  bone  vertically  elongated, 
flattened  on  both  sides,  and  presenting  tivo  faces,  hvo  borders,  and  two  extremities. 

The  external  face  is  smooth  and  nearly  plane.  The  internal  face  is  excavated 
into  a  ghdmg  groove  to  form  the  tarsal  groove,  in  which  passes  the  tendon  of 
the  perforans.     The  anterior  border  is  slightly  concave.     The  posterior  border  is 

Fig.  99. 


TARSUS  OF   THE 
INTERNAL  ASPECT. 

1,  Calcis;  2,  astragalus  (first  and  second  bones  of  the 
upper  row);  3,  cuboid;  4,  scaphoid;  5,  cuneiform 
magnum;  6,  vascular  canal  between  the  cuboid, 
scaphoid,  and  cuneiform  magnum ;  7,  smooth  sur- 
face for  the  tendon  of  the  gastrocnemius;  8,  surface 
for  insertion  of  latter ;  9,  smooth  surface  for  the 
tendon  of  the  perforans  ;  10,  anterior  extremity  of 
the  tibia;  11,  superior  extremity  of  the  large  meta- 
tarsal bone.  A,  Bones  of  the  upper  row.  b.  Bones 
of  the  lower  row.     T,  Tibia,     m,  Metatarsus.  ' 


ANTERO-EXTERNAL  ASPECT. 

1,  Calcis;  2,  astragalus;  3,  cunei- 
form  magnum ;  4,  scaphoid ;  5, 
cuboid;  6,  cuneiform  parvum ;  7, 
superior  extremity  of  large  meta- 
tarsal bone  ;  8,  superior  extremity 
of  inner  small  metatarsal  bone. 
A,  Bones  of  the  upper  row.  b, 
Bones  of  the  lower  row.  t,  Tibia. 
M,  Metatarsus, 


thicker,  straight,  and  rugged.  The  superior  extremity,  slightly  enlarged,  con- 
Btitutes  the  summit  of  the  calcaneum,  and  is  divided  into  three  parts  :  a  middle 
which  gives  attachment  to  the  tendon  of  the  gastrocnemius  ;  the  other  the 
anterior,  is  a  smooth  surface  on  which  this  tendon  rests  when  the  foot  is  much 
flexed  ;  the  third,  altogether  posterior,  also  constitutes  a  gliding  surface  for  the 


TEE  POSTERIOR   LIMBS. 


147 


tendon  of  the  perforatus.  The  inferior  extremity,  wide  and  voluminous,  shows  in 
front  three  or  four  articular  facets  which  articulate  with  the  astragalus,  and  are 
(Separated,  like  those  of  the  last  bone,  by  an  irregular  and  slightly  excavated  sur- 
face for  insertion.  Below,  it  shows  for  articulation  with  the  cuboid  a  fifth  facet, 
continuous  with  one  of  the  preceding. 

Developynent. — The  calcaneum  is  developed  from  two  nuclei  of  ossification, 
one  of  which  is  for  the  summit. 

Cuboid  hone  (Figs.  98,  99). — This  little  bone,  situated  at  the  external  side  of  the 
scaphoid  and  the  large  cuneiform  bone,  between  the  calcis  and  two  of  the  metatar- 
sals, does  not  resemble  a  cube,  but  a  parellelopiped  elongated  from  before  to  behind. 
It  offers  six  faces  :  a  superior,  an  articular  face,  in  contact  with  the  calcaneum  ; 
an  inferior,  also  articular,  articulating  with  the  principal  and  external  rudimen- 
tary metatarsal  hones  ;  an  internal,  furnished  with  three  facets  for  contact  with 
the  scaphoid  and  great  cuneiform,  and  crossed  from  before  to  behind  by  a  fissure, 


Fig.  100. 


Fig.  101. 


LEFT    HOCK  (FRONT    VIEW). 

1,  Apex  of  calcaneum  ;  2,  astragalus,  inner 
ridge ;  3,  cuneiform  magnum ;  cunei- 
form medium ;  5,  cuboid. 


LEFT   HOCK   (INTERNAL   ASPECT). 

1,  Apex  of  calcaneum ;  2,  inner  articular 
ride  of  astragalus ;  3,  navicular,  scaphoid, 
or  cuneiform  medium  ;  4,  cuneiform  mag- 
num ;  5,  cuboid  ;  6,  cuneiform  parvum. 


which  forms  with  these  two  bones  a  vascular  canal  ;  an  external,  an  anterior,  and 
B>  posterior,  covered  with  imprints. 

Scaphoid  hone  (the  large  cuneiform  of  Percivall)  (Figs.  98,  99). — Flattened  above 
and  below,  it  is  described  as  having  two  faces  and  a  circumference.  The  faces,  both 
articular,  are  furrowed  by  a  channel  of  insertion,  and  are  distinguished  as  superior 
and  inferior.  The  first  is  concave,  and  articulates  with  the  astragalus  ;  the  second 
is  convex,  and  in  contact  with  the  two  cuneiform  bones.  The  circumference  offers, 
outwardly,  two  small  facets,  which  are  adapted  to  similar  facets  on  the  cuboid 
bone.     For  the  remainder  of  its  extent,  it  is  covered  with  imprints  (Fig.  99). 

Oreat  Cuneiform  hone  (the  middle  cuneiform  of  Percivall)  (Figs.  99, 100, 101). — 
Flattened  above  and  below,  and  triangular  in  shape,  this  bone  is  much  smaller  than 
the  scaphoid,  though  resembling  it  in  a  striking  manner.  Its  superior  face  is  in 
contact  with  the  latter  bone,  and  its  inferior  face  articulates  with  the  middle  and 
internal  lateral  metatarsal  bones.  Its  external  harder  is  provided  with  one  or  two 
facets  to  correspond  with  the  cuboid  bone  ;  and  its  internal  herder  also  shows  one. 


148  THE  BONES. 

which  is  in  contact  with  another  on  the  small  cuneiform.  Its  anterior  border  is 
roughened  throughout  its  extent  (Figs.  99,  100). 

Small  Cuneiform  hone  (Figs.  99,  101). — Situated  at  the  inner  side  of  the  tarsus, 
this  bone — the  smallest  of  any  yet  examined — is  elongated  from  before  to 
behind,  flattened  on  both  sides,  and  wedged  in  between  the  os  scaphoides,  the  large 
cuneiform  bone,  and  the  large  and  internal  small  rudimentary  metatarsal  bones, 
with  which  it  corresponds  by  four  articular  facets  :  a  superior,  two  inferior,  and 
one  internal.  When  this  bone  is  in  two  portions,  there  are  then  three  cuneiforms, 
which  may  be  distinguished,  as  in  Man,  by  naming  them //•«/,  second,  and  third 
(Fig.  99). 

It  is  not  very  rare  to  find  the  scaphoid  {cuneiform  mafjnum)  fused  with  the 
great  cuneiform  {cuneiform  medium),  and  sometimes  even  the  cuboid  is  joined  to 
the  cunean  bones. 

Development. — All  the  bones  of  the  tarsus,  with  the  exception  of  the  calcis, 
are  developed  from  a  single  nucleus  of  ossification. 

The  astragalus  in  the  Ass  is  distinguished  from  that  of  the  Horse  by  the 
external  Hp  of  the  trochlea,  which  is  abruptly  deviated  outwards  at  its  inferior 
extremity ;  and  by  the  disposition  of  the  inferior  articular  surface,  which  is 
regularly  convex  from  side  to  side,  behind  the  groove  for  insertion  ;  in  the 
Horse  this  part  of  the  articular  surface  is  formed  by  the  union  of  two  facets 
inclined  towards  each  other.  In  the  same  animal,  the  scaphoid  {cuneiform 
maffnum)  is  recognized  by  the  shape  of  the  superior  diarthrodial  surface,  which 
is  a  hollowed  reproduction  of  the  inferior  face  of  the  astragalus  ;  and  the  g7-eat 
cuneiform  {cuneiform  medium)  by  the  larger  concavity  of  its  scaphoid  face. 

Differential  Characters  in  the  Tarsal  Bones  of  the  other  Animals. 

In  the  domestic  animals,  the  tarsus  differs  in  the  number  and  shape  of  the  bones  enteriug 
into  its  formation. 

A.  Ox,  Sheep,  Goat. — The  tarsus  of  these  animals  is  slender,  and  has  only  five  bones, 
the  cuboid  and  scaphoid  being  fused  into  one.  The  astragalus  i.s  tlongated  from  above  to 
below,  and  is  united  to  the  scaphoid  by  an  antero-posterior  groove,  and  to  the  calcis  by  a 
vertical  groove ;  so  that  it  has  tiiree  trochleas.  The  principal  trochlea  has  its  external  border 
thicker  than  the  internal,  and  decreases  from  below  to  above.  The  posterior  trochlea  is  not 
80  deep  as  the  others.  The  calcis  is  lon^'  and  thin;  the  posterior  gliding  surface  on  the 
summit  is  excavated  into  a  channel.    The  small  cuneiform  is  pisiform,  and  but  slightly  developed. 

B.  Camel. — In  the  Camel,  there  are  six  tarsal  bones,  two  of  which  :ire  cuneiform.  The 
astragalus  articulates,  by  means  of  a  double  groove,  with  the  scaphoid  and  cuboid.  The 
calcis  is  relatively  short,  and  about  equally  excavated  on  its  two  faces.  The  cuboid  ia 
voluminous. 

C.  Pig. — The  tarsus  of  this  animal  much  resembles  that  of  Ruminants  in  its  general 
disposition,  and  in  the  astragalus  ami  calcis;  but  it  lias  seven  bones,  because  the  cuboid  and 
scaphoid  are  separate,  and  there  are  constantly  three  cunfi/nrm  bones. 

D.  Dog,  Cat. — There  are  seven  bones  in  the  tarsus  of  these  animals.  The  astragalus 
articulates  witli  the  scaphoid— almost  as  in  Man— by  means  of  a  tiue  In  ad,  separated  from  the 
rest  of  the  bone  by  a  constriction  named  the  neck  of  the  astragalus.  The  cuboid  and  the  three 
cuneiform  bones  articulate  with  the  five  metatarsal  bones. 

2.  Bones  of  the  Metatarsus  (Figs.  98,  102). 

These  bones  are  three  in  number — a  median  and  two  lateral — and  offer  the 
greatest  analogy  to  the  metacarpal  bones.  This  enables  us  to  dispense  with  a 
general  description  of  them,  and  to  confine  ourselves  only  to  indicating  the 
differential  characters  which  distinguish  them  from  the  corresponding  bones  in 
the  anterior  limb. 


THE  POSTERIOR  LIMBS. 


149 


The  principal,  large,  or  median  metatarsal  bone,  is  longer  than  the  same 
metacarpal,  and  its  body,  instead  of  being  slightly  compressed  before  and  behind, 
is  nearly  a  regular  cylinder.  It  presents,  outwardly,  a  fissure  which  is  directed 
at  first  obliquely  backwards  and  downwards  (Fig.  99),  and  afterwards  descends 
vertically  along  the  lateral  external  metatarsal  bone.  The  articular  surface  of 
the  superior  extremity  is  excavated  in  its  centre  by  a  large  fossa  for  insertion 
(Fig.  99).  This  surface  presents,  behind  and  outwards,  a 
thick  tubercle  which  appears  to  spring  from  the  body  of  the  Fig.  102. 

bone,  and  which  has  a  facet  against  which  the  external  rudi- 
mentary metatarsal  rests.  The  inferior  extremity  is  at  the 
same  time  wider  and  thicker  than  that  of  the  metacarpus. 
Above  and  in  front  of  the  articular  surface,  it  is  hollowed 
by  a  small  transverse  fossa,  which  is  deeper  than  in  the  corre- 
sponding bone  in  the  anterior  limb. 

Of  the  tivo  rudimentary  {digital,  splint),  or  lateral  meta- 
tarsal bones,  the  external  is  always  longest,  if  not  thickest. 
The  internal  bears  on  the  superior  face  of  its  head  three 
articular  facets,  two  of  which  articulate  with  the  small 
cuneiform,  and  the  third  with  the  large  bone  of  that  name. 

The  length  of  these  rudimentary  metatarsals  is  nearly 
equal  to  three-fourths  that  of  the  principal  metatarsal. 

The  metatarsus  of  the  Ass  is  remarkable  for  the  length 
of  its  rudimentary  metatarsals,  which  are  nearly  five-sixths 
that  of  the  principal  bone.  The  latter  is  also  notable, 
because  of  its  length  and  fineness  ;  and  if  it  is  compared 
with  that  of  the  Horse,  it  is  distinguished  by  :  1.  The  tri- 
angular shape  of  its  upper  extremity,  due  to  the  great 
development  of  the  tubercle  on  which  the  external  rudi- 
mentary metatarsal  lies.  2.  The  flat  diarthrodial  facet  which 
articulates  with  the  antero-external  part  of  the  large  cunei- 
form,    3.  The  marked  inequality  of  its  condyles. 


Differential  Characters  in  the  Metatarsal  Bones  of  the 
OTHER  Animals. 


posterior  aspect  op 
left  metatarsus. 

1,  Head  of  principal 
metatarsal   bone  ;   2, 

3,  external  and  in- 
ternal splint  bones, 
or  metatarsals  of  the 
rudimentary    digits  ; 

4,  rough  surface  for 
insertion  of  suspen- 
sory ligament  ;  5, 
nutrient  foramen  ; 
6,  middle  ridge  or 
tenon  of  inferior  arti- 
cular surface. 


The  metatarsus  is  also  a  region  in  which  the  number  of  bones  varies 
in  the  domesticated  animals.  Tlius,  in  Ruminants  there  are  two,  and 
five  in  the  Pig,  Camivora,  and  Rodents. 

The  metatarsals  of  the  latter  are  exactly  like  the  same  bones  in 
the  anterior  limb.     Those  of  Ruminants  are  slightly  different. 

A.  Ox,  Sheep,  Goat.— In  the  Ox,  Sheep,  and  Goat  are  found  a 
principal  and  a  rudimentary  metatarsal  bone.  The  latter  is  a  small 
lenticular  bone,  articulating,  posteriorly,  with  the  head  of  the  large 
metatarsal  bone.  The  latter  differs  from  the  principal  metacarpal 
bone,  in  being  longer,  quadrilateral  in  form,  and  having  a  vascular 
canal  traversing  the  posterior  face  of  its  upper  extremity. 

B.  Camel. — The  metatarsus  differs  from  the  metacarpus  by  its  greater  width  and  less 
thickness;  the  articular  surface  is  divided  by  a  depression  into  two  parts,  situated  on  the  same 
horizontal  plane. 

C.  Pig.— The  Pig  has  four  perfect  metatarsals,  and  an  internal  rudimentary  one.  The 
latter  is  a  small  bone  flattened  on  both  sides,  articulating  by  means  of  a  diarthrodial  facet,  and 
sometimes  fused  posteriorly  with  the  upper  end  of  the  fourth  metatarsal. 

D.  Dog,  Cat.— Ill  the  Dog  and  Cat  are  one  rudimentarv  and  four  perfect  metatarsals. 
The  former  is  articulated  with  the  internal  cuneiform,  and  represents  the  vestige  of  the  thumb. 


150  THE  BONES. 

3.  Bones  of  the  Digital  REOrioN  (Fig.  98). 

Id  Man,  the  digits  of  the  foot — known  as  toes — are  very  different  to  those  of 
the  hand  ;  but  it  is  otherwise  with  the  domestic  animals.  The  phalangeal  region 
of  the  posterior,  closely  resembles  that  of  the  anterior  Hmb.  The  analogy  in  the 
conformation  of  these  bones  is  even  pushed  so  far,  that  it  becomes  very  difficult 
to  distinguish  them  from  one  another. 

There  are  some  differential  characters,  however.  For  instance,  it  is  remarked  : 
1.  That  the  first  phalanx  is  not  so  long  as  in  the  anterior  limb,  and  less  wide 
and  thick  at  its  inferior  extremity  ;  but  it  is,  on  the  contrary,  wider  and  thicker  at 
its  superior  extremity.  2.  That  the  lateral  diameter  of  the  second  phalanx  is 
shorter.  8.  That  the  third  phalanx,  less  expanded  towards  its  inferior  border, 
has  more  the  shape  of  a  V,  and  that  its  inferior  face  is  more  concave.  4.  That 
the  sesamoids  are  less  voluminous.  5.  That  the  navicular  bone  is  shorter  and 
narrower. 

In  the  Ass,  the  same  differential  features  are  observed  between  the  posterior 
and  anterior  phalanges  as  in  the  Horse,  and  there  are  no  very  marked  differences 
between  the  former  in  these  two  animals.  The  following  may,  however,  serve  to 
distinguish  them. 

The  ^rs^  phalanx  of  the  Ass  is  proportionately  longer  than  that  of  the  Horse, 
and  the  rugosities  are  larger ;  the  principal  nutrient  foramen  is  usually  on  the 
anterior  face,  and  the  external  glenoid  cavity  is  much  smaller  than  the  internal. 

The  second  phalanx  is  also  proportionately  longer  than  that  of  the  Horse. 
Its  inferior  median  furrow  is  deep,  especially  behind  ;  it  has  generally  numerous 
nutrient  foramina  below  the  posterior  gliding  surface  ;  the  median  tenon  of  its 
upper  face  terminates  before  and  behind  by  a  salient  tubercle,  which  prevents  the 
bone  from  resting  in  equilibrium  when  it  is  placed  vertically  on  that  face. 

The  third  phalanx  of  the  Ass  is  higher  than  that  of  the  Horse,  owing  to  the 
development  of  the  pyramidal  process  ;  it  is  constricted  above  the  preplantar 
fissure  ;  the  surface  of  the  sole  is  proportionately  more  extensive,  and  the 
concavity  of  the  semilunar  crest  is  less  marked  ;  the  extremities  of  that  crest  are 
saUent,  and  the  plantar  fissures  very  deep. 

The  navicular  bone  shows  very  marked  differences.  In  the  Ass  its  thickness 
is  very  considerable,  due  to  the  median  ridges  on  both  faces.  Its  posterior 
border  is  very  oblique  downwards  and  backwards,  and  it  is  towards  this  border 
that  it  inclines  when  Ave  attempt  to  make  it  lie  horizontally  on  its  upper  face  ; 
while  its  two  extremities  are  more  curved  than  in  the  Horse. 

In  the  Mule  and  Hinny,  the  two  first  phalanges  much  resemble  those  of 
the  Ass,  while  the  third  shows  the  characters  of  that  of  their  progenitors. 
Nevertheless,  that  of  the  Hinny  is  rather  more  like  the  third  phalanx  of  the 
Horse  than  that  of  the  Ass,  while  the  contrary  is  observed  in  that  of  the  Mule. 

Differential  Characters  in  the  Posterior  Phalangeal  Region  of  other  Animals. 

In  all  the  domesticated  animals,  the  posterior  digits  comport  themselves  exactly  like  the 
anterior.  The  Carnivora  alone  offer  a  notable  difference ;  in  them,  in  reality,  the  inner  toe, 
the  equivalent  of  the  thumb,  does  not  exist — or  rather,  it  is  only  represented  by  tiie  rudimentary 
metatarsal  bone  alluded  to  above.  Nevertheless,  it  frequently  occurs  that  a  completely  de- 
veloped thumb  is  found  in  this  animal ;  and  in  this  case  the  rudimentary  metatarsal  is  ordinarily 
followed  by  a  ligamentous  cord,  to  which  is  suspended  a  bony  stylet  that  represents  either  the 
inferior  extremity  of  the  metatarsal  bone,  or  the  first  phalanx ;  it  is  to  this  stylet  that  are  found 
articulated  in  succession  the  second  and  third  phalanges. 

It  is  not  rare  to  meet  with  a  sixth  floating  toe  in  dogs  of  very  large  size. 


THE  POSTEBIOR  LIMBS. 


151 


Comparison  of  the  Abdominal  Limb  of  Man  with  that  of  Animals. 

A.  Pelvis  (Fig.  103). — The  longitudinal  axis  of  the  pelvis  of  Man  forms,  with  the  horizon, 
an  angle  of  about  40°. 

The   bones  which  compose  it  are  proportionately  larger  and  stronger  than  in  all  the 
domesticated  animals. 

The  two  faces  of  the  ilium,  and  especially  the  inner  face,  are  much  hollowed ;  the  iliac 
crest  has  the  form  of  an  italic  S. 

The  pubis  alone  participates  in  the  formation  of  the  pelvic  sympliysis,  and  the  concavity 
which,  in  the  domesticated  animals, 

is  called  the  ischial  arch,  is  desig-  Fig.  103. 

nated  in  Man  the  pubic  arch. 

In  consequence  of  the  excavation 
on  the  inner  face  of  the  ilium,  the 
pelvic  cavity  may  be  divided  into 
the  great  and  lesser  pelvis.  In  the 
latter  are  lodged  the  genital  and 
urinary  organs,  as  well  as  the  ex- 
tremity of  the  digestive  tube. 

B.  Thigh  (Fig.  104).— The  femur 
of  Man  is  nearly  vertical,  and  situ- 
ated in  a  direction  sligiitly  oblique 
downwards  and  inwards  ;  it  presents 
a  curvature  forwards.  The  body  of 
the  bone  is  prismatic  and  triangular 
in  its  middle  part;  the  posterior 
border  of  this  prism  forms  a  some- 
what salient  cresf,  which  takes  the 
place  of  all  the  insertion  eminences 
on  the  posterior  aspect  of  the  femur 
in  animals,  and  is  designated  the 
linea  aspera.  This  line  bifurcates 
above  and  below ;  below,  the  branches 
margin  a  triangular  or  popliteal  space. 

The  head  is  supported  by  a  long 
neck,  inserted  obliquely  into  the 
superior  extremity.  The  two  con- 
dyles are  joined  together  in  front  by 
the  trochlea,  which  is  wide  and* 
shallow. 

a  Leg  (Fig.  105)  —Three  bones  : 


human  pelvis  (female). 

1,  Last  lumbar  vertebra  ;  2,  2,  intervertebral  substance ; 
3,  promontory  of  the  sacrum  ;  4,  anterior  surface  of  the 
sacrum  ;  5,  coccyx ;  6,  iliac  fossae  ;  7,  antero-superior 
spinous  process ;  8,  antero-inferior  spinous  process ; 
9,  acetabulum,  a.  Its  notch  ;  6,  body  of  ischium;  c,  its 
tuberosity  ;  d,  its  spine  ;  e,  pubis ;  /,  symphysis  pubis  ; 
g,  arch  of  the  pubes ;  h,  angle  of  os  pubis;  i,  spine  of 
pubes,  with  crest  between  it  and  h;  k,  k,  pectineal  line ; 
I,  I,  ilio-pectineal  line,  with  its  prolongation,  m,  m ; 
n,  ilio-pectineal  eminence  ;  o,  smooth  surface  for  femoral 
vessels  ;  p,  p,  great  sacro-ischiatic  notch. 


the  tibia,  fibula,  and  patella. 

The  tibia  is  very  long  ;  its  crest  (or  spinous  process)  is  much  more  developed  than  in  any 
of  the  domesticated  animals,  and  describes  a  kind  of  curve  like  an  italic  S.  On  the  inner 
aspect  of  the  inferior  extremity  is  seen  a  voluminous  process  which  occupies,  inwardly,  a 
portion  of  the  tibio-tarsal  articulation  :  this  is  the  internal  malleolus.  The  articular  surface  ia 
not  exactly  formed  to  correspond  with  the  whole  articular  surface  of  the  astragalus. 

The  fibula  is  as  long  as  the  tibia.  It  is  prismatic,  and  slightly  twisted  on  itself.  It  articu- 
lates above  and  below  with  the  tibia.  The  lower  extremity  responds  to  the  astragalus,  and 
forms  a  prominence  named  the  external  malleolus. 

There  is  nothing  particular  to  note  in  the  patella. 

D.  Foot  (Fig.  106). — The  foot  of  Man  is  pLaced  in  a  horizontal  direction.  Its  upper 
aspect  is  convex;  its  inferior  face  is  excavated,  and  it  rests  on  the  ground  by  its  two 
extremities. 

1.  Tarsus. — In  the  tarsus  there  are  seven  bones,  three  of  which  are  cuneiform.  The  astra- 
galus articulates  with  the  tibia  and  fibula ;  it  responds  to  the  scaphoid  by  a  well-detached 
convex  articular  surface,  named  the  head. 

In  the  bones  of  the  lower  row,  it  is  remarked  that  the  cuboid  responds  to  the  fifth  and 
fourth  metatarsals;  the  first  cuneiform  to  the  third;  the  second  cuneiform  to  the  second 
metatarsal :  and  the  third  to  the  first. 

2.  Metatarsus. — The  metatarsus  is  composed  of  five  bony  columns,  nearly  parallel  to  each 


152 


TEE  BONES. 


other.     They  are  enumerated  from  without  to  within,  and  increase  in  length  from  the  first  to 
the  fourth  ;  the  fifth  is  the  shortest  and  most  voluminous. 

3.  Digital  region-— This  comprises  five  digits  or  toes.  The  phalanges  of  these  toes  are 
analogous  to  those  of  the  fiiigersi,  from  which  they  are  distinguished  by  their  small  size.  They 
increase  in  volume  from  tlie  first  to  the  fifth  digit. 


Article  VIL — The  Foot  in  General. 

It  would  be  useless  to  reproduce  here  the  general  considerations  discussed 
when  treating  of  the  hand  (p.  121),  and  it  may  therefore  be  sufficient  to  state 

Fig.  104.  Fig.  105.  Fig.  106. 


RIGHT    HUMAN    FEMUR 
(ANTERIOR   ASPECT). 

1,  Shaft ;  2,  head  ;  3,  neck  ; 
4,  great  trochanter ;  5, 
anterior  intertrochanteric 
line;  6,  lesser  trochanter; 
7,  external  condyle ;  8, 
internal  condyle  ;  9,  tu- 
berosity for  attachment 
of  external  lateral  liga- 
ment; 10,  fossa  for  ten- 
don of  origin  of  popliteus 
muscle  ;  11,  tuberosity 
for  attachment  of  inter- 
nal lateral  ligament. 


HUMAN  TIBIA  AND  FIBULA 
OF  RIGHT  LEG  (ANTERIOR 
ASPECT). 

1,  Shaft  of  tibia;  2,  inner 
tuberosity;  3,  outer  tu- 
berosity ;  4,  spinous  pro- 
cess ;  5,  tubercle ;  6,  in- 
ternal surface  of  shaft ; 
7,  lower  extremity  of 
tibia;  8,  internal  malleo- 
lus;   9,  shaft    of   fibula; 

10,  its  upper  extremity; 

11,  its  lower  extremity; 
between  1  and  6  is  the 
sharp  crest  of  the  tibia. 


DORSAL  SURFACE   OF   LEFT 
HUMAN   FOOT. 

1,  Astragalus  ;  2,  its  anterior 
extremity       articulating 
with  the  cuboid  bone,  4 
3,  3,  calcis  ;  4,  scaphoid 

5,  internal  cuneiform  bone 

6,  middle  cuneiform  bone 

7,  external  cuneiform 
bone  ;  8,  cuboid  bone ;  9, 
metatarsal  bones  of  first 
and  second  toes;  10,  first 
phalanx  of  great  toe  ;  11, 
second  ditto  ;  12,  13,  14, 
phalanges  of  second  toe. 


that  the  works  of  the  anatomists  already  mentioned — and  especially  those  of  Joly 
and  Lavocat — have  demonstrated  that  the  foot  of  animals  is  constructed  on  the 
same  type  as  the  hand.     In  it,  as  in  the  hand,  three  sections  are  remarked  :  the 


THE  FOOT   IN  GENERAL.  153 

tarsus,  metatarsus,  and  phalanges  ,-  and,  in  the  archetype,  each  section  comprises 
five  parallel  rows,  each  of  which  has  two  tarsal  bones,  one  metatarsal,  and  three 
phalangeal.  In  the  present  fauna  there  is  not,  perhaps,  a  Mammal  which  has 
a  perfectly  typical  pentadactylous  abominal  limb  ;  for  this  ideal  disposition  is 
modified  in  the  sense  already  indicated  for  the  hand.  In  the  following-  brief 
paragraphs,  an  attempt  will  be  made  to  show  the  manner  in  which  Man  and  the 
domestic  animals  may  be  allotted  to  the  archetype. 

1.  31  an. — In  Man  the  archetype  is  realized  in  the  metatarsal  and  phalangeal 
sections,  and  it  will  now  suttice  to  examine  the  tarsal  section.  This  contains 
seven  separate  bones — three  in  the  upper  and  four  in  the  lower  row.  It  must 
not  be  forgotten  that  the  scaphoid,  although  situated  between  the  two  rows, 
nevertheless  belongs  to  the  upper,  as  happens  in  the  carpus  of  certain  species. 
Apparently,  it  is  deficient  in  two  bones  in  the  upper  row  and  one  in  the  inferior. 
This  deficiency  arises  from  fusion  of  the  apex  of  the  calcaneum  {first  superior 
metatarsal  hone)  with  the  remainder  of  the  bone  {second  hone),  of  the  scaphoid 
with  the  fifth  hone  in  the  upper  row,  and  of  the  first  inferior  tarsal  bone  with  the 
cuboid  in  the  second  row. 

2.  Carnivora. — The  foot  of  Carnivora  only  differs  from  that  of  Man  in  the 
arrangement  of  the  thumb  ;  as  this  digit  has  usually  no  phalanges,  and  its  meta- 
tarsal piece  is  only  a  small,  very  short  styliform  bone.  Notwithstanding  this 
difference,  the  pentadactylous  archetype  is  as  easily  recognized  in  the  foot  of 
these  animals  as  in  that  of  Man. 

3.  Rodents. — The  foot  of  the  Rahhit  and  Hare  is  yet  less  complete  than  that 
of  Carnivora,  as  the  metatarsal  of  the  thumb  is  absent  ;  but,  by  the  constitution 
of  the  tarsus,  Rodents  resemble  Carnivora  and  Man,  and  consequently  they  can 
be  also  classed  in  the  pentadactylous  type. 

4.  Pig. — In  this  animal,  the  tarsus  presents  the  same  number  of  pieces  and 
the  same  fusions,  as  in  Rodents,  Carnivora,  and  Man.  The  metatarsus  and 
phalangeal  section  have  four  complete  toes — first,  second,  third,  and  fourth  ; 
and  with  regard  to  the  fifth  digit,  it  is  represented  by  a  short,  flat,  and  irregu- 
larly triangular  metatarsal,  articulating  posteriorly  with  the  third  metatarsal,  and 
attached  to  the  third  cuneiform  by  some  ligamentous  fibres. 

5.  Ruminants. — The  foot  of  the  Ox,  Sheep,  and  Goat  present  numerous 
fusions,  and  even  some  abortions.  The  tarsus  has  only  five  distinct  bones  ;  for, 
besides  the  fusions  which  exist  as  in  the  preceding  animals,  the  scaphoid  is  united 
to  the  cuboid,  and  the  third  cuneiform  is  completely  aborted. 

The  metatarsus  of  these  animals  includes  a  principal  metatarsal,  provided, 
inferiorly,  with  a  double  diarthrodial  surface,  and  an  internal  rudimentary 
metatarsal.  Must  we  consider  the  principal  metatarsal  as  the  result  of  the  fusion 
of  the  third  and  fourth,  and  admit,  in  Ruminants,  the  abortion  of  the  first  two 
digits  ?  Several  anatomists  have  professed  this  opinion.  Lavocat  did  so  at  first, 
and  then  abandoned  it.  He  considered  the  principal  metatarsal  as  due  to  fusion 
of  the  metatarsals  of  the  first  four  digits,  and  he  expressed  himself  on  this  point 
as  follows  :  "  The  first  and  the  fourth  metatarsals  are  visible,  and  fused  above 
and  behind  the  united  large  metatarsals.  Each  of  them  has  the  shape  of  a  thick 
pyramid,  with  its  base  uppermost,  large,  and  about  five  centimetres  long  in  the 
Ox.  Above,  they  join  to  form  an  arch,  which  is  the  contour  of  a  wide  and  short 
vascular  canal  running  between  them  and  the  two  large  metatarsals,  and  which 
does  not  exist  in  the  Goat  and  SheejJ.  Their  widened  superior  extremity  is  in 
contact  with  the  bones  of  the  tarsus,  to  wit :  the  first  metatarsal  with  a  facet  of 


154  TEE  BONES. 

the  p-ototarsiis,  or  first  portion  of  the  cuboid  ;  the  fourth  metatarsal  with  all  the 
inferior  facet  of  the  tetrofarsus,  or  second  cuneiform.  And  each  of  them  has, 
for  this  eminently  normal  connection,  an  articular  facet  well  separated  from  the 
diarthrodial  surface  of  the  large  metatarsals  by  a  large  fossa  destitute  of  cartilage. 
In  this  way  the  first  four  metacarpals  are  gathered  into  a  single  bundle.  .  .  . 
Lastly,  the  thumb,  or  fifth  digit,  is  constantly  represented  in  the  foot  by  a 
distinct  metatarsal  bone — at  least  in  the  Ox,  Goat,  and  Sheep.''' 

Notwithstanding  the  reasons  on  which  Lavocat  bases  his  last  interpretation 
as  to  the  metatarsals  of  the  Ox,  we  prefer  adopting  the  first.  In  fact,  if  some 
wild  Rimiinants  are  examined — Deer,  for  example — there  will  be  found  a  tarsus 
identical  with  that  of  the  Ox,  and  a  principal  metatarsal  provided  with  a  vascular 
canal,  with  two  inverted  pyramidal  expansions  ;  and,  in  addition,  two  styliform 
bones  lying  to  the  outside  and  the  inside  of  the  principal  bone  of  the  shank. 
These  bones  evidently  represent  the  metatarsals  of  the  second  and  fifth  digits  ; 
as  they  exist  at  the  same  time  as  the  lateral  ridges  on  the  principal  metatarsal 
bone,  it  appears  to  be  impossible  to  give  to  the  latter  the  same  signification. 

The  posterior  phalangeal  region  of  the  Ox  is  almost  identical  with  the  an- 
terior ;  it  is,  therefore,  needless  to  again  demonstrate  its  constitution.  That  of 
the  Sheep  and  Goat  has  no  rudimentary  phalanges  to  serve  as  a  base  for  the 
ergot,  in  the  hand  ;  but  the  two  ergots  suffice  to  represent  the  first  and  fourth 
digits,  and  so  to  include  these  animals  in  the  pentadactylous  type. 

6.  SoUpeds. — The  tarsus  of  these  animals  has  six  or  seven  bones.  In  the 
second  case,  it  is  identical  with  that  of  Carnivora  and  Man  ;  in  the  first,  the 
second  and  third  cuneiforms  are  fused.  The  metatarsus  and  posterior  phalangeal 
section  having  the  same  constitution  as  those  of  the  anterior,  the  reader  is 
referred  to  the  description  of  the  Hand  in  General. 

Article  VIII. — The  Limbs  in  General  and  their  Parallelism. 

A.  The  Limbs  in  General. — The  bony  sections  which  compose  the  limbs, 
are  destined  not  only  to  support  the  trunk  in  a  stationary  attitude,  but  also  to 
transport  it  during  progression.  This  double  use  gives  rise  to  a  difference 
between  the  anterior  and  the  posterior  members.  The  front  limbs,  being  nearer 
the  centre  of  gravity  than  those  behind,  have  to  sustain  the  largest  share  of  the 
weight.  They  ought,  consequently,  to  be  specially  organized  as  organs  of  sup- 
port. Therefore  it  is,  that  the  four  principal  bones  composing  each  of  them — 
shoulder,  arm,  forearm,  foot — although  flexed,  or  disposed  to  be  flexed,  in  an 
inverse  sense  to  one  another,  oppose  to  the  pressure  of  the  weight  of  the  trunk — 
which  tends  incessantly  to  throw  them  down — obstacles  purely  mechanical,  and 
of  such  energy  that  we  may  still  understand  how  the  body  can  be  sustained  on 
the  anterior  limbs,  if  we  suppose  all  the  muscular  masses  surrounding  these  bony 
columns  to  be  removed,  except  one. 

Thus,  the  weight  of  the  body  is  transmitted  to  the  scapula  through  the 
muscles  that  attach  that  bone  to  the  trunk.  It  then  passes  to  the  humerus,  and 
thence  to  the  radius,  to  be  thrown,  finally,  on  the  diflferent  pieces  composing 
the  foot.  Now,  the  humerus  forming  with  the  scapula  an  angle  which  is  open 
behind,  and  with  the  bones  of  the  forearm  another  angle  open  in  front,  the 
weight  of  the  body  pressing  continually  on  these  angles  tends  to  close  them, 
and  thus  cause  the  flexion  of  these  bones.  But  this  result  is  prevented  by  the 
combined  action  of  two  muscular  powers — the  biceps  and  the  extensors  of  the 


THE  LIMBS  IN  GENERAL  AND   THEIR  PARALLELISM. 


155 


forearm.  With  regard  to  the  radius, 
carpus,  and  metacarpus,  owing  to  their 
vertical  direction,  they  themselves  sup- 
port the  pressure  of  the  weight  of  the 
body  without  requiring  any  muscular 
aid.  But  the  digital  region,  being  di- 
rected obliquely  forward  and  downward, 
forms,  with  the  principal  metacarpal,  a 
third  angle  open  in  front,  for  the  main- 
tenance of  which  nature  has  given  solid, 
inert,  or  contractile  mechanical  bands. 

The  anterior  limbs  are  also  agents 
of  transport,  for  they  can  elevate  the 
trunk  by  the  spring  of  their  bony  rays, 
and  fix  themselves  on  the  ground  by 
their  free  extremities. 

The  posterior  limbs  are  less  favour- 
ably disposed  than  those  in  front  to  as- 
sume the  function  of  columns  of  support ; 
as  their  rays  are,  for  the  most  part,  in  a 
state  of  permanent  flexion,  and  joined  in 
an  angular  manner  to  one  another,  as 
may  be  seen  by  glancing  at  the  skeleton 
(Figs.  107,  108,  1,  2,  4,  5,  6).  It  is, 
therefore,  necessary  that  muscular  agency 
should  prevent  the  breaking-down  of 
these  columns.  Though  defective  as 
supports,  they  are  nevertheless  admirably 
designed  to  serve  as  agents  of  locomotion. 
The  slightest  erection  of  these  inclined 
bones  propels  the  mass  of  the  body  for- 
ward, and  this  impulsion  is  almost  wholly 
transmitted  to  the  trunk,  in  consequence 
of  the  very  intimate  union  of  the  pelvis 
with  the  vertebral  column. 

B.  Parallel  between  the  An- 
terior AND  Posterior  Limbs. — After 
what  has  just  been  said,  it  will  be  seen 
that  the  anterior  limbs  are  more  par- 
ticularly destined  for  the  support  of  the 
body,  while  the  posterior  ones  more 
especially  play  the  part  of  propelling 
agents  in  the  locomotory  acts. 

Notwithstanding  this  difference  in 
the  functions  assigned  them,  these  two 
limits  offer  in  their  conformation  such 
striking  resemblances  to  each  other,  that 
some  authors  have  been  inclined  to  con- 
sider the  posterior  as  an  exact  repetition 
of  the  anterior  limb.     The  followina:  is 


ANTERIOR   LIMB   OF   THE    HORSE   (ANTERO- 
EXTERNAL   VIEW). 

0,  Scapula ;  H,  humerus  ;  a,  radius  ;  C,  carpus ; 
M,  metacarpus ;  p,  phalanges ;  s,  sesamoid 
bone.  1,  Coracoid  process;  2,  head  of  the 
humerus;  3,  external  trochanter ;  4,  deltoid 
ridge;  5,  inferior  articular  surface  of  the 
humerus;  6,  olecranon;  7,  ulna;  9,  pisi- 
form (trapezium),  or  supercarpal  bone. 


156 


THE  BONES. 


Fig.  108. 


POSTERIOR    LIMB   OF   THE    HORSE    (ANTERO- 
EXTERNAL    VIEW). 

C,  Coxa ;  F,  femur ;  J,  tibia  ;  8,  tarsus  ;  M,  meta- 
tarsus; p,  phalanges;  S,  sesamoid.  1,  Ischium  ;  1', 
pubis;  2,  head  of  the  femur;  3,  trochanter  major; 
4,  trochanter  minor ;  5,  condyle  of  the  femur  ; 
6,  patella  ;   7,  fibula  ;  tibial  ridge  ;  9,  calcis. 


a  brief  analysis  of  the  analogies  ex- 
isting between  them. 

At  the  end  of  the  last  century, 
Winslow  and  Vicq-d'Azyr,  and  nearer 
our  own  time,  Cuvier,  Flourens, 
Paul  Gervais,  Martins,  Gegenbauer, 
Lavocat,  Foltz,  and  Sabatier,  have 
occupied  themselves  with  the  homo- 
logy of  the  anterior  and  the  posterior 
members.  All  these  anatomists  did 
not  absolutely  arrive  at  the  same 
conclusion  ;  for  several  of  them,  for- 
getting that  the  question  should  be 
examined  in  the  whole  animal  series, 
made  Man  alone  the  subject  of  their 
studies. 

Vicq-d'Azyr  and  Cuvier  recom- 
mended that  the  anterior  and  pos- 
terior limbs  of  opposite  sides  should 
be  compared.  Martins  and  Gegen- 
bauer, allowing  a  torsion  of  the 
humerus  of  180°,  advised  that  the 
two  members  of  the  same  side  should 
be  compared,  care  being  taken  to 
make  allowance  for  the  untwisting 
of  the  180°  contortion  at  the  lower 
end  of  the  humerus.  Lastly, 
Flourens  and  Lavocat  contrasted  the 
two  members  of  the  same  pair  with 
each  other,  after  placing  the  hand 
in  a  position  of  natural  pronation 
by  rotation  of  the  radius  on  the  ulna, 
and  without  turning  either  limb  or 
bone,  or  even  a  portion  of  a  bone, 
no  matter  what  kind  of  animal  may 
be  under  examination.  We  will 
adopt  the  latter  proceeding,  as  it  is 
the  simplest  and  most  natural. 

Parallel  between  the  coxa  and 
scapula. — The  analogies  existing  be- 
tween these  two  bones  are  but  little 
striking  at  first  sight ;  nevertheless, 
with  attention  there  is  no  ditficulty 
in  finding  in  the  coxa  the  three  pieces 
that  enter  into  the  composition  of 
the  shoulder  (Figs.  107,  108). 

The  ilium  represents  the  scapula. 
The  external  iliac  fossa  reminds  one 
of  the  supra-  and  subspinous  fossae. 
Occasionally,  there  is  met  with  in  the 


THE  LIMBS  IN  GENERAL   AND   THEIR  PARALLELISM.  157 

Horse  a  rudiment  of  the  crest  dividing  the  ihac  fossa  into  two  parts,  and  in 
some  animals — the  Pig,  Sheep,  and  Goat— this  crest,  which  is  the  trace  of  the 
scapular  spine,  becomes  constant  and  very  evident. 

With  regard  to  the  cotyloid  cavity,  it  repeats  in  the  posterior  limb  the  glenoid 
cavity  of  the  scapula.  There  remains  to  determine,  in  the  latter  bone,  the 
portions  analogous  to  the  ischium  and  pubis.  If  we  rely  upon  the  evidence 
afforded  by  the  muscular  insertions,  we  come  to  the  conclusion  that  the  ischium 
corresponds  to  the  coracoid  process,  and  the  pubis  to  the  clavicle  of  animals 
which  are  provided  with  one.  It  will  also  be  remarked  that  the  coxa  is  directed 
backwards,  while  the  scapula  inclines  obliquely  forwards  ;  this  opposition  in  the 
direction  of  the  bones  in  no  way  alters  their  analogies  ;  the  functions  of  the 
members  to  which  they  correspond  require  this  inverse  position. 

Parallel  hehveen  the  femur  and  hwiwus. — The  resemblance  between  these 
two  bones  is  remarkable.  Thus  there  is  found  in  the  first.  1.  An  articular 
head,  better  detached  than  that  of  the  humerus,  but  shaped  in  the  same  manner. 
2.  A  trochanter  analogous  to  the  great  tuberosity,  and  also,  like  it,  decomposable 
into  three  distinct  parts — summit,  crest,  and  convexity.  2.  A  lesser  trochanter, 
representing  the  small  tuberosity.  4.  An  eminence  for  the  insertion  of  the 
superficial  gluteus  muscle,  which  takes  the  place  of  the  deltoid  imprint.  5.  An 
inferior  articular  pulley  continued  between  the  two  condyles  by  a  non-articular 
groove  ;  this  trochlea  certainly  corresponds  to  the  median  groove  of  the  inferior 
humeral  face. 

There  are,  no  doubt,  differences  in  the  two  bones,  but  they  have  no  bearing 
upon  the  result  just  indicated.  Thus,  the  linea  aspera  of  the  femur  is  situated 
behind  ;  that  of  the  humerus  in  front.  In  the  femui'  the  two  condyles  of  the 
inferior  extremity  are  placed  behind  the  trochlea  ;  the  contrary  holds  in  the 
humerus.  These  modifications  are  necessary,  in  order  to  give  the  movements  of 
the  limbs  a  convenient  direction.  The  leg  is  flexed  backward  on  the  thigh,  while 
the  fprear  is  flexed  forward  on  the  humerus. 

Parallel  hetween  the  bones  of  the  leg  and  those  of  the  forearm. — It  is  more 
particularly  in  these  two  regions  that  the  question  of  analogies  has  been  resolved 
in  a  contradictory  manner  by  anatomists.  It  would  have  appeared  less  compli- 
cated had  it  been  studied  in  a  large  number  of  species. 

If  we  examine  the  leg-bones  of  certain  Marsupials^  in  which  the  tibia  and 
fibula  are  apart  as  in  the  radius  and  ulna  in  Man,  it  will  be  found  that :  1.  These 
two  bones  articulate  with  the  condyles  of  the  femur.  2.  The  anterior  face  of  the 
tibia  has  no  ridge.  3.  The  patella  is  attached  to  the  upper  end  of  the  fibula. 
From  this  it  might  be  concluded  that,  in  Man  and  the  domestic  animals,  the 
tibia,  with  the  exception  of  its  anterior  and  external  tuberosities,  is  the  homologue 
of  the  radius,  and  the  fibula  and  external  and  anterior  tuberosities  of  the  tibia 
are  the  homologues  of  the  body  and  inferior  extremity  of  the  ulna.  The  patella 
corresponds  to  the  olecranon  ;  the  mobility  of  the  first  cannot  be  offered  as  an 
objection  to  this  assimilation,  for  in  Bactrians  the  olecranon  forms,  like  the 
patella,  an  independent  bony  nucleus. 

Parallel  between  the  bones  of  the  posterior  and  those  of  the  anterior  foot. — The 
analogy  becomes  so  marked  when  these  two  regions  are  compared,  that  it  is 
scarcely  necessary  to  allude  to  them.  The  tarsal  bones  are  to  the  posterior  limb 
what  the  carpals  are  to  the  anterior  one  ;  it  is  even  possible  to  compare,  one  by 
one,  the  several  pieces  in  these  regions.  The  metatarsals  are  but  a  repetition  of 
the  metacarpals  ;  while  the  digital  bones  are  so  much  alike,  that  it  is  difficult  to 
distinguish  the  anterior  from  the  posterior  phalanges. 


158  THE  BONES, 

CHAPTER   III. 

THE   BONES   IN   BIRDS. 

These  animals,  destined  for  the  most  part  to  sustain  themselves  in  the  air, 
should  exhibit  in  the  conformation  of  their  skeleton  all  the  conditions  which 
may  favour  aerial  locomotion  ;  from  this  arise  the  differences  which  distinguish 
their  skeleton  from  that  of  the  Mammalia — differences  which  will  now  be  rapidly 
traced. 

Veetebeal  Column.  Cervical  vertebne. — The  cervical  spine  represents  in 
the  Bird,  as  in  the  Mammal,  a  kind  of  balancing-pole  curved  like  an  S,  which 
supports  the  head,  and  by  its  changes  in  form  and  direction  varies  the  centre  of 
gravity.  When  a  Bird  rises  in  the  air  and  flies  rapidly,  it  lengthens  the  neck 
and  stretches  out  the  head,  to  carry  the  centre  of  gravity  forwards.  But  when 
it  rests  on  the  ground,  it  makes  the  balancing-pole  assume  the  natural  and  more 
or  less  graceful  inflection,  by  throwing  the  head  backwards,  and  transferring  the 
greater  portion  of  the  weight  of  its  body  to  the  columns  of  support  formed  by 
the  posterior  Hmbs.  These  displacements  of  the  centre  of  gravity  are  executed 
in  Birds  on  a  more  extensive  scale  than  in  Mammalia  ;  the  vertebral  limbs  in  the 
former  are  also  longer,  hghter,  and  enjoy  an  excessive  mobility. 

The  vertebrae  composing  it  number  fourteen  in  Fotvls,  twelve  in  the  Fir/eon, 
fifteen  in  the  DmJc,  aijd  eighteen  in  the  Goose ;  in  the  Swan  twenty-three  have 
been  counted  ; — a  curious  variety,  which  singularly  contrasts  with  the  numerical 
unity  noticed  as  one  of  the  most  remarkable  characters  in  Mammalia  !  These 
vertebras  are  generally  longer  than  in  the  latter  animals,  and  are  particularly 
distinguished  by  the  configuration  of  the  articular  surfaces  of  the  inferior  part  or 
body.  These  are  diarthrodial  facets  convex  in  one  direction  and  concave  in  the 
other,  articulating  the  vertebral  bodies  by  a  veritable  and  reciprocal  clamping. 
In  this  manner,  the  anterior  head  of  the  body  of  each  vertebra  is  replaced  by  a 
facet  concave  on  both  sides,  and  convex  vertically  ;  while  the  posterior  extremity 
of  the  bone  bears,  instead  of  a  concavity,  a  facet  convex  in  the  lateral  sense,  and 
concave  from  above  to  below.  The  inferior  crest  of  the  body  (Fig.  109,  2,  2') 
only  exists  in  the  first  and  last  vertebrae ;  but  it  forms  a  veritable  spine, 
analogous  to  that  observed  in  the  lumbar  vertebrae  of  the  Rabbit.  The  spinous 
process  (Fig.  109,  1,  1')  only  forms  a  simple  crest  in  the  middle  part  of  the  neck  ; 
it  becomes  more  salient  in  the  vertebras  which  occupy  the  two  extremities  of  this 
region.  The  transverse  process  represents  on  the  side  of  the  vertebra  a  thick, 
obtuse,  and  irregular  tubercle,  situated  under  the  anterior  articular  process,  and 
pierced  at  its  base  by  a  large  vertebral  foramen  (Fig.  109,  4,  4').  It  is  most 
frequently  furnished  with  a  small  styloid  prolongation  (Fig.  109,  3,  3')  directed 
backwards  and  downwards,  forming  an  epiphysis  at  an  early  period,  and 
representing  a  real  undeveloped  rib. 

The  atlas  has  no  transverse  processes.  This  vertebra  is  shaped  like  a  thin 
ring,  and  is  excavated  on  its  anterior  contour  by  a  small  cavity,  into  which  is 
received  the  single  condyle  of  the  occipital  bone. 

The  axis  shows  a  very  marked  odontoid  process,  with  a  single  facet  under 
that  eminence. 

Dorsal  vertebrce  (Fig.  109,  b,  c). — These  are  seven  in  the  Fotvl  and  Figeon, 


TEE  BONES  IN  BIRDS. 


159 


and  nine  in  the  Goose  and  Duck;   they  are  nearly  always  consolidated  into  a 
single  piece  to  which  the  trunk  is  fixed,  and  which  gives  the  wings  a  sohd 


Fig.  109, 


SKELETON    OF    A    FOWL. 

From  A  to  B,  Cervical  VertebrcE .  1,  spiDous  process  of  the  third  vertebra;  2,  inferior  ridge  on  body 
of  the  same  ;  3,  styloid  prolongation  of  the  transverse  process  of  the  same;  4,  vertebral  foramen 
of  the  same  ;  1',  2',  3',  4',  the  same  parts  in  the  twelfth  vertebra.  From  B  to  C,  Dorsal  Vertebrae: 
6,  spinous  process  of  the  first ;  7,  crest  formed  by  the  union  of  the  other  spinous  processes.  From 
D  to  E,  Coccygeal  Vertebrce.  F,  G,  Head:  8,  interorbital  septum;  9,  foramen  of  communication 
between  the  two  orbits  ;  10,  premaxillary  bone  ;  10',  external  openings  of  the  nose;  11,  maxilla; 


160 


THE  BONES. 


Fig.  110. 


support  in  the  violent  efforts  that  flight  demands.  The  two  or  three  last  are 
often  even  covered  by  the  wing-bones,  and  joined  to  them.  The  inferior  crest 
of  the  body  forms  a  very  long  spine,  especially  in  the  first  vertebras.  The 
spinous  processes — flat,  wide,  short,  and  consolidated  with  each  other  by  their 
opposite  borders — constitute  a  long  crest  extending  from  the  last  cer\ical  vertebra 
to  the  bones  of  the  wings  (Fig.  lOD,  7).  The  trans- 
verse processes  widen  to  their  summit ;  in  the  FovjI 
they  are  nearly  constantly  fused  with  each  other. 

Lumbar  and  sacral  vertebne. — All  these  vertebrae 
are  formed  exactly  on  the  same  type ;  so  that  it  be- 
comes difficult,  if  not  impossible,  to  fix  the  point  where 
the  lumbar  region  ends  or  the  sacral  begins.  At  first 
independent  of  each  other,  these  vertebra?,  numbering 
fourteen,  soon  become  consolidated  with  one  another 
and  with  the  ribs  ;  but  their  primitive  separation  is 
always  indicated  by  the  lateral  septa,  which  form,  on 
their  inferior  face,  the  vestiges  of  the  transverse  pro- 
cesses. The  former  are  closely  united  to  the  latter  in 
the  dorsal  region. 

Coccygeal  vertebrce. — In  the  coccygeal  region,  the 
spine  recovers  its  mobility.  The  tail  of  the  Bird, 
indeed,  fulfils  the  office  of  a  rudder  in  directing  it  during 
flight ;  and  it  is  absolutely  necessary  that  the  vertebr* 
which  serve  as  a  base  for  the  steering  feathers  should 
preserve  their  independence,  so  as  to  allow  these  to  be 
carried  to  the  right,  left,  downwards,  or  upwards. 
These  vertebrje — seven  in  number — present  spinous 
processes  which  are  often  bifurcated,  transverse  pro- 
cesses very  developed,  and  sometimes  even  spines  more 
or  less  long  on  the  inferior  surface  of  their  bodies.  The 
last  vertebra  is  always  the  most  voluminous  ;  it  is 
flattened  on  both  sides,  and  terminates  in  a  curved-up 
point. 

Head  (Fig.  110,  f,  g).— The  head  of  the  Bird  is 
small,  and  of  a  conical  form.  The  anterior  extremity 
is  elongated,  and  terminated  by  a  pointed  or  flattened 
beak,  which  allows  the  animal  to  cut  the  air  with  more 
facility. 

Bones  of  the  cranium. — The  bones  which  compose 

the  cranium  are,  as  in  Mammalia,  an  occipital,  parietal, 

frontal,  ethmoid,  sphenoid,  and  two  temporcds.     These  bones  are  not  isolated  from 

each  other,  excepting  during  early  life  in  the  shell ;  and  the  ossifying  process 

12.  OS  quadratum  ;  13,  malar  bone.  H,  Sternum  :  14,  brisket  or  keel ;  15,  episternal  process  ;  16, 
internal  lateral  process;  17,  lateral  external  process;  18,  membrnne  which  closes  the  internal 
notch  ;  19,  membrane  of  the  exte^-nal  notch,  i.  etc.,  Superior  Ribs :  20,  posterior  process  of  the 
fifth.  J,  Inferior  ribs.  K,  Scapula.  L,  Coracoid  hone.  M,  Furculum :  m,  m,  its  two  branches. 
N,  Humerus.  0,  Ulna :  o.  radius,  p.  p',  Bones  of  carpus.  Q,  q'.  Bones  of  metacarpus.  R.  First 
phalanx  of  th°  large  digit  of  the  loinq :  r.  second  phalanx  of  the  same,  r'.  Phalanx  of  thumb. 
S,  Hium.  s'.  Ischium,  s".  Pubis  :  21.  sciatic  foramen  :  22,  foramen  ovale.  T,  Femur,  v.  Patella. 
V,  Tibia.  X,  Fibula :  y,  single  bone  of  tarsus,  y.  Metatarsus  :  23,  superior  process  representing 
a  united  metatarsal  bone ;  24,  process  supporting  the  claw.     Z,  etc..  Digits. 


HEAD  OF  AN  OWL  (NATURAL 
SIZE  ;    POSTERIOR   VIEW). 

1,  Occipital  foramen  ;  2,  single 
occipital  condyle  ;  3,  ptery- 
goid ;  4,  inferior  articular 
surface  of  the  os  quadratum  ; 

5,  anterior  process  of  ditto  ; 

6,  6,  anterior  face  of  the 
palatine  bones,  forming:  the 
guttural  orifice  of  the  nasal 
cavities;  7,  posterior  ex- 
tremity of  ditto;  8,  zygo- 
matic ;  9.  lachrymal ;  10. 
premaxilla  ;  11,  orbital  pro- 
cess ;  12,  right  zygomatic 
process  ;  12',  zygomatic  pro- 
cess on  the  opposite  side, 
united  to  the  orbital  pro- 
cess. 


TEE  BONES  IN  BIRDS.  161 

which  unites  them  is  so  rapid,  that  the  cranium,  shortly  after  hatching,  is  already 
a  single  piece.  No  detailed  description  of  the  separate  bones  will  be  given  here, 
but  only  a  few  brief  observations  which  may  be  of  some  utility. 

Thus,  the  occipital  bone  shows  for  articulation  with  the  spine  only  a  single 
condyle,  situated  under  the  occipital  foramen,  and  excavated  by  a  slight  gi'oove. 
In  Palmipedes,  this  bone  is  pierced,  behind  the  crests  which  give  attachment  to 
the  extensor  muscles,  by  two  foramina  which  penetrate  the  cranium,  and  represent 
permanent  fontanella.  The  parietal  bone  is  feebly  developed,  and  formed  from 
only  two  primary  nuclei.  The  frontal  is  the  largest  bone  of  the  cranium  ;  its 
orbital  process  (Fig.  110,  1),  incomplete,  is  supported  by  a  particular  piece 
(posterior  frontal)  fixed  between  the  principal  frontal  bone,  parietal,  and  posterior 
sphenoid,  with  which  it  is  sometimes  confounded.  The  perpendicular  lamina  of 
the  ethmoid  is  considerable,  and  forms  between  the  two  orbits  a  thin  vertical 
septum  (Fig.  109,  8).  Its  posterior  border  is  notched  opposite  to  the  optic 
foramen,  and  thus  constitutes  an  opening  which  communicates  between  the  two 
orbital  cavities  (Fig.  109,  9).  It  is  also  channeled,  near  its  upper. border,  by 
a  fissm-e  which  terminates  by  two  openings  at  its  extremities,  one  entering  the 
cranium,  the  other  the  nasal  cavities.  Tliis  fissure  and  these  foramina  pennit  the 
passage  of  the  ethmoidal  nerve,  which  in  this  way  traverses  the  orbit  before 
arriving  at  its  destination.  The  ethmoidal  cells  are  more  membranous  than 
bony  :  their  base  is  attached  to  a  very  delicate  transverse  plate,  which  is  often 
membranous  and  not  cribbled,  and  forms  part  of  the  anterior  orbital  wall.  These 
cells  replace,  at  the  same  time,  the  lateral  masses  of  the  ethmoid  and  turbinated 
bones  of  MammaUa.  The  sphenoid  appeal's  to  be  formed  of  a  single  piece,  and 
shows  on  its  sides  two  diarthrodial  facets  corresponding  to  the  pterygoids.  It  is 
pierced  by  one  foramen  for  the  passage  of  the  optic  nerves  ;  but  this  foramen 
opens  on  the  outer  and  opposite  side  of  the  posterior  notch  of  the  interoi-bital 
septum,  and  thus  allows  each  of  the  nerves  passing  through  it  to  reach  the  eye 
for  which  it  was  intended. 

It  is  worthy  of  remark,  that  an  analogous  disposition  is  also  noticed  in  the 
Rabbit.^  The  temporal  bones  present  at  their  base  an  articular  surface  correspond- 
ing to  the  square  bone  (os  qimdratum)  (Fig.  109,  12,  12').  In  the  Foivl  species, 
the  zygomatic  process  forms  a  small  flattened  tongue,  directed  forwards,  sometimes 
free,  and  at  other  times  united  by  its  superior  border  to  the  summit  of  the 
orbital  process.  These  two  eminences  are  exceedingly  short  in  Pigeons.  In 
Palmipedes  they  are  consolidated  and  confounded  so  intimately,  that  it  becomes 
impossible  to  distinguish  them  from  one  another.  From  this  union  results  a 
long  and  strong  process,  which  inclines  forward  and  meets  a  particular  prolonga- 
tion of  the  OS  unguis,  forming  with  it  a  real  bony  arch.  This  arch  limits,  below 
and  outwardly,  the  orbital  cavity. 

Bones  of  the  face. — The  supermaxilla  comprises  :  a  premaxilla,  two  nasal,  two 
lachrymal,  two  palatine,  two  pterygoid,  two  zygomatic  hones,  and  a  vomer.  The 
inferior  jaw  has  for  its  base  a  maxillary  hone,  which  articulates  with  the  cranium 
by  means  of  two  supplementary  pieces  named  the  square  hones.  The  premaxillary 
hone  (Fig.  110,  10)  is  formed,  before  hatching  is  completed,  of  two  lateral  pieces, 

'  This  analogy  is  really  striking,  and  might,  in  our  opinion,  serve  as  a  basis  for  a  new 
ietermiuation  of  the  interorbital  septum.  We  are  tempted,  indeed,  to  consider  this  bony 
lamina  as  the  inferior  sphenoid  and  the  middle  portion  of  the  ethmoid  in  Birds.  This  manner 
of  viewing  it  tends  to  confirm  the  ideas  of  M.  Tabourin  on  the  inferior  sphenoid  and  the 
ethmoid  of  Mammals. 


162  THE  BONES. 

which  represent  the  two  small  premaxillaries  of  Mammals.  This  bone  is  very 
considerable,  and  of  itself  forms  the  base  of  the  upper  beak,  the  form  of  which  it 
determines  ;  it  is  pointed  and  conical  in  the  GalUnacea,  and  wide  and  flattened 
above  and  below  in  Palmipedes.  In  front  it  circumscribes  the  external  openings 
of  the  nose,  and  is  prolonged  superiorly  into  two  lengthy  processes  which  dovetail 
between  the  nasal  bones.  Two  inferior  processes  belonging  also  to  this  bone 
concur  in  the  formation  of  the  palatine  roof.  The  supennaxillaries,  analogues  of 
the  supermaxillaries  of  Mammals,  are  two  rudimentary  bones  situated  on  the  sides 
and  at  the  base  of  the  beak.  They  form  a  part  of  the  palatine  roof  and  the  walls 
of  the  nasal  cavities.  The  nasal  bones  circumscribe  above,  inwardly,  and  even 
outwardly,  the  external  orifices  of  these  cavities.  The  palatine  hones  encircle,  as 
in  Mammals,  the  guttural  openings  of  the  nose,  and  constitute  in  great  part  the 
roof  of  the  palate ;  their  posterior  extremity  lies  against  the  pterygoids  ;  the 
anterior  joins  the  supermaxillaries  and  the  inferior  process  of  the  premaxillary 
bone.  The  pterygoids  extend  obliquely  from  the  sphenoid  to  the  square  bones, 
and  are  united  to  the  sphenoid  by  diarthrodial  articulation.  The  zygomatic  hones 
have  the  form  of  two  very  thin  stylets,  and  are  united  to  the  square  bone  by  their 
posterior,  and  consolidated  with  the  supermaxillary  by  their  anterior,  extremity. 
The  vomer  separates  the  guttural  openings  of  the  nose  from  one  another. 

The  bones  of  the  upper  jaw  are  not  fused  to  each  other  so  rapidly  as  the 
bones  of  the  cranium.  The  ascending  processes  of  the  premaxillary  and  nasal 
bones  even  remain  for  a  long  time  tmited  to  the  frontal  bone  by  a  simple 
synarthrodial  articulation.  This  arrangement  allows  the  upper  beak  to  execute 
a  certain  elevating  movement,  of  which  we  will  speak  when  describing  the 
articulations. 

The  inferior  maxillary  hone  is  originally  formed  of  a  great  number  of  distinct 
segments,  which  are  soon  united  into  a  solid  piece.  The  square,  petrous.,  or  hone 
of  the  tympanum  ought  to  be  considered  as  detached  from  the  temporal.  It  is 
prismatic  in  shape,  and  provided  on  its  upper  surface  with  a  diarthrodial  facet 
which  unites  it  to  the  temporal,  and  on  its  lower  face  with  another  facet  articu- 
lating with  the  branch  of  the  maxilla.  Outwards  it  joins  the  zygomatic  bone, 
and  inwards  the  pterygoid.  Behind,  it  gives  attachment  to  the  membrane  of 
the  tympanmn ;  and  in  front  it  presents  a  small  eminence  of  insertion,  which 
Meckel  considered  a  second  zygomatic  process. 

Thokax. — Sternum  (Fig.  109,  H  1). — The  sternum  of  Birds,  serving  as  a 
basis  of  support  to  the  muscles  moving  the  wings,  should  offer,  and  does  in 
fact  show,  a  remarkable  degree  of  strength,  because  of  the  extraordinary  volume 
of  these  muscles.  And  these  being  more  powerful  and  energetic  as  the  Bird 
exhibits  a  greater  degree  of  aptitude  for  flight,  it  results  that  the  structure  of 
the  sternum  is  solid  in  proportion  as  the  creature  is  strong  on  the  wing.  For 
this  reason,  we  may  infallibly  pronounce  as  to  the  extent  and  power  of  a  bird's 
flight  by  an  inspection  of  the  sternum  of  individuals  of  its  species.  In  this 
respect,  however,  we  only  announce  what  is  well  known  to  be  a  particular  appli- 
cation of  the  rules  established  by  the  great  law  of  concordance  between  the 
anatomical  disposition  of  organs  and  their  physiological  finality. 

Studied  in  Palmipedes.,  which  will  serve  as  a  type  for  description,  the  sternum 
presents  itself  in  the  form  of  a  large  rectangular  cuirass,  elongated  from  before 
to  behind,  of  itself  constituting  the  inferior  wall  of  the  thoracic  cavity,  and  also 
largely  protecting  the  abdominal  cavity.  Its  superior  face  is  concave,  while  the 
inferior  is  convex,  and  entirely  occupied  by  the  insertion  of  the  pectoral  muscles. 


THE  BONES  IN  BIRDS.  1G3 

It  presents,  on  the  median  line,  a  thin  and  very  salient  ridge,  named  the  brisket 
{carina  or  keel)  (Figs.  109,  14  ;  111,  B.  2),  which  in  a  remarkable  manner 
multiplies  the  points  of  attachment  of  these  muscles.  The  anterior  border 
offers  in  its  middle  a  small  eminence  of  insertion,  the  episternal  (Figs.  109,  15  ; 
111,  A  2).  Laterally,  two  articular  grooves  are  seen  which  correspond  to  the 
coracoids.  The  posterior  border  is  cut  by  two  notches  which  are  often  converted 
into  foramina  (Fig.  Ill,  b  3,  3).  On  the  lateral  borders  are  observed  small 
double  articular  facets  answering  to  the  inferior  ribs.  The  angles  which  separate 
these  two  borders  from  the  anterior  are  both  prolonged  into  a  httle  eminence, 
named  by  some  authors  the  costal  process  (Fig.  Ill,  a  33). 

In  the  Fowl,  the  sternum  is  not  so  strong  as  in  the  Goose  or  Duck.  On 
each  side  of  the  brisket  it  shows  two  wide  notches,  which  greatly  reduce  its 
substance.  These  notches  (Figs.  109,  18,  19  ;  111,  a  6,  7),  closed  in  the  fresh 
state  by  membranes,  are  distinguished  as  external  and  internal.  The  latter,  of 
greater  size  than  the  former,  extends  nearly  to  the  extremity  of  the  bone. 
From  this  division  of  the  lateral  plates  of  the  sternum,  result  two  long  and 
slender  processes  directed  backwards  (Figs.  109,  16,  17  ;  111,  a  4,  5).  The 
external  terminates  by  becoming  widened,  and  forming  a  kind  of  bony  plate, 
which  covers  the  last  inferior  ribs. 

The  sternum  of  Pigeons  is  distinguished  by  the  enormous  development  of 
the  brisket.  The  two  notches  of  the  Fowl  are  also  met  with  in  these  birds,  but 
the  internal  is  nearly  always  converted  into  a  narrow  foramen. 

This  comparative  study  of  the  sternum  in  the  chief  domesticated  birds,  leads 
us  to  appreciate  the  correctness  of  the  principles  just  enunciated,  with  regard 
to  the  form  and  extent  this  bone  may  exhibit.  The  Gallmaceous  Birds,  properly 
so  called,  which  fly  little  and  badly,  have  the  sterur.-n  singularly  weakened  by 
the  deep  notches  cut  in  its  lateral  parts.  With  Palmipedes,  the  sternum  is  wide 
and  but  slightly  notched,  so  that  the  Goose  and  Duck,  which  waddle  along  so 
awkwardly  in  our  poultry  yards,  are  capable  of  sustaining  long  and  rapid  flight, 
like  that  of  the  wild  individuals  of  the  same  species.  With  regard  to  Pigeons, 
which  are  well  known  to  be  swift  and  powerful  flyers,  may  this  advantage  not 
be  due  to  the  extraordinary  development  of  the  keel  which  constitutes  the 
brisket  ? 

Ribs  (Fig.  109,  I,  etc.).— In  the  Fowl  and  Pigeon  there  are  seven  pairs 
of  ribs  ;  and  in  the  Duck  nine  pairs.  Articulated  superiorly  with  the  dorsal 
vertebrte,  as  in  Mammals,  these  bones  are  provided,  near  their  middle,  with  a 
flat  eminence  which  commences  at  the  posterior  border,  and  is  directed  back- 
wards and  upwards,  to  rest  by  its  free  extremity  on  the  external  face  of  the  next 
rib.  These  eminences  (Fig.  109,  20)  form  an  epiphysis  at  an  early  period,  and 
are  usually  absent  in  the  first  and  last  ribs.  They  concur  in  an  efficacious 
manner  to  increase  the  solidity  of  the  thorax. 

The  costal  cartilages  of  the  Mammalia,  are  in  Birds  often  transformed  into 
veritable  inferior  ribs,  joined  to  the  superior  ribs  by  a  diarthrodial  articulation 
(Fig.  109,  J).  These  pieces  are  long  and  strong,  and  all  terminate  at  their  lower 
extremity  by  a  double  facet  which  articulates  with  the  lateral  border  of  the 
sternum  ;  they  are  nearly  always  absent  in  the  two  first  ribs.  It  is  not  rare  to 
see  the  last  united  to  the  one  before  it,  instead  of  passing  directly  to  the  sternum  ; 
in  which  case  it  comports  itself  like  the  asternal  ribs  of  Mammals. 

Anterior  Limbs.  Shoulder-bone. — The  shoulder  comprises  :  a  scapula ;  a 
particular  bone  named  the  coracoid  by  Cuvier :  and  a  clavicle,  which  forms,  in 


164 


THE  BONES. 


coalescing  with  that  of  the  opposite  side,  a  single  bone  called  the  /or A'  (furcidum)^ 
or  osfuradare.  The  scapula  (Figs.  109,  k  ;  111,  a  8)  is  narrow,  elongated,  and 
falciform,  and  shows  no  trace  of  a  spine.  Its  anterior  extremity  only  forms  a 
portion  of  the  glenoid  cavity,  and  is  united  by  means  of  a  fibro-cartilage  with 
the  fork  of  the  coracoid  bone.  The  latter  (Figs.  109,  L  ;  111  a  9)  is  so  named 
because  it  represents  the  coracoid  process  of  Mammals,  and  is  a  long  prismatic 
bone,  directed  obliquely  from  above  downwards,  and  before  to  behind.  Its 
superior  extremity  is  often  fused  with  the  scapula,  and  united  at  an  acute  angle 
with  that  bone  to  form  a  portion  of  the  articular  cavity  which  receives  the  head 
of  the  humerus.  Its  inferior  extremity  is  flattened  from  before  to  behind,  and 
responds  by  a  diarthrodial  articulation  to  the  anterior  border  of  the  sternum. 
The  coracoid  is  long  in  Birds  which  fly  slowly  ;  it  is,  on  the  contrary,  short, 
thick,  and  therefore  very  solid,  in  quick  flyers.     Th.^  fork  (Figs.  109,  M;  111,. 

Fig.  111. 


STERNUM    AND   BONES   OF   THE   WING. 

A,  Sternum  and  mng-bones  of  the  Fowl  {upper  face).  1,  Body  of  the  sternum;  2,  its  episternal 
process;  3,  3,  its  costal  proces>es  ;  4,  4,  its  lateral  external  processes;  5,  5,  its  lateral  internal 
processes;  6,  6,  internal  notches;  7.  7,  external  notches;  8,  scapula;  9,  coracoid;  10,  fork; 
11,  opening  for  the  passage  of  the  elevator  of  the  wing;  13,  humerus;  14,  air-opening  in  that 
bone;  15,  ulna;  16,  radius;  17,  ulna-cavpal  bone;  18,  radio-carpal  bone;  19,  large  metacarpal ; 
20,  small  metacarpal  ;  21,  first  phalnnx  of  the  large  digit ;  21',  second  phalanx  of  ditto  ;  22,  small 
phalanx  lying  beside  the  first  bone  of  the  large  digit,  and  representing  the  remains  of  a  third  digit ; 
23,  thumb. 

B,  Sternum  and  shoulder-hone  of  a  young  Duck  (inferior  surface).  1,  1,  Sternum ;  2,  keel ;  3,  3, 
lateral  notches  ;  4,  4,  coracoid  •,  5,  5,  fork  ;  6,  opening  for  the  passage  of  the  elevator  of  the  wing. 


B  5,  5)  is  a  single  bone,  shaped  like  a  V  or  U,  situated  at  the  base  of  the  two 
wings,  in  front  of  the  trunk,  and  in  an  oblique  direction  downwards  and  back- 
wards. The  two  branches  which  form  it  represent  the  clavicles  ;  they  meet  and 
are  united  at  their  inferior  extremities,  where  they  describe  a  curvilinear  angle 
more  or  less  open,  attached  to  the  brisket  by  means  of  a  membranous  ligament. 


THE  BONES  IN  BIRDS.  165 

Their  superior  extremity  rests  within  and  opposite  to  the  glenoid  cavity,  against 
the  scapula  and  coracoid,  forming  with  these  bones  a  remarkable  foramen, 
through  which  passes  the  tendon  of  the  elevator  muscle  of  the  wing  (Fig.  Ill, 
A  4,  B  6).  The  forks  play  the  part  of  an  elastic  spring,  whose  office  it  is  to 
prevent  the  wings  coming  towards  each  other  during  contraction  of  the  depressor 
muscles.  The  conformation  of  this  bone  is,  therefore,  like  the  sternum,  related 
to  the  extent  and  power  of  flight ;  and  for  this  reason  it  is  that,  in  swift  flyers, 
the  two  branches  of  the  furculum  are  thick,  solid,  widely  separated,  and  curved 
like  a  U  ;  while  in  those  which  fly  heavily  and  with  difficulty,  these  branches 
are  thin  and  weak,  and  joined  at  an  acute  angle.  The  latter  formation  greatly 
diminishes  its  strength,  and  lessens,  in  a  singular  manner,  the  reactionary  power 
of  the  bony  arch  it  represents. 

Bone  of  the  arm. — The  humerus  (Figs.  109,  n  ;  111,  a  13)  offers  an  articular 
oval-shaped  head,  and  an  air-opening  placed  beneath  this  eminence.  It  is  long 
in  Palmipedes,  ordinarily  so  in  the  Gallinaca,  proper,  and  very  short  in  Pigeons. 

Bones  of  the  forearm  (Figs.  109,  o,  o  ;  111,  A  15,  16).— The  radius  is  much 
less  voluminous  than  the  ulna.  The  latter  has  an  extremely  short  olecranon  ; 
and  the  two  bones  are  separated  from  one  another  in  their  middle  part  to  meet 
again  at  their  extremities,  where  they  are  united  by  ligamentous  bands  in  such 
a  way  as  to  render  the  movements  of  pronation  and  supination  impossible.  This 
mode  of  union,  which  nevertheless  does  not  prevent  the  two  bones  from  gliding 
slightly  on  each  other  in  the  direction  of  their  length,  has  been  wisely  adopted 
by  nature  in  order  that  the  wing  might  strike  the  air,  like  an  oar,  by  its  inferior 
face  ;  otherwise,  the  resistance  of  the  aerial  medium  would  make  these  two  bones 
pivot,  and  cause  the  wing  to  present  itself  to  the  air  in  a  wrong  direction. 

Bones  of  the  carpus  (Figs.  109,  p,  p'  ;  111,  a  17,  17).— These  are  only  two, 
and  are  distinguished  by  the  names  of  radius  and  ulna,  in  consequence  of  their 
corresponding  more  particularly  to  these  bones  in  other  animals. 

Bones  of  the  metacarpus  (Figs.  109,  q,  q' ;  111,  a,  19,  20).— These  also 
number  only  two,  and  are  separated  at  their  middle  portion,  to  be  consolidated 
at  their  extremities. 

Bones  of  the  digital  region. — The  wing  of  a  bird  is  composed  of  three  digits. 
One  of  them,  which  resembles  the  thumb  and  forms  the  basis  of  the  false  wing 
is  composed  of  a  single  styloid-sliaped  phalanx,  articulated  at  the  base  of  a  small 
particular  process  belonging  to  the  superior  extremity  of  the  largest  metacarpal 
bone  (Figs.  109,  r' ;  111,  A  23).  The  largest  digit  comprises  two  phalanges, 
which  succeed  the  last  bone  (Figs.  109,  R,  r  ;  111,  a  21,  21'),  The  third  digit 
is  represented  by  a  small  rudimentary  phalanx  (Fig.  109,  a  22),  which  corre- 
sponds to  the  inferior  extremity  of  the  small  metacarpal  bone,  and  lies  beside 
the  first  phalanx  of  the  large  digit  in  the  closest  manner. 

It  is  well  to  remark  that  the  hand  and  forearm  are  longer  in  proportion  to 
the  quality  of  flight ;  those  two  regions  of  the  Aving,  for  example,  are  very  short 
in  Gallinaceous  Birds. 

Posterior  Limbs,  Coxa,  or  os  iliac. — This  is  a  voluminous  and  very 
solid  piece,  particularly  in  walking  birds,  and  composed,  as  in  the  Mammalia, 
of  an  ilium,  ischium,  and  pubis.  The  ilium  (Fig.  109,  s),  very  long,  is  con- 
solidated with  the  last  two  dorsal,  the  lumbar,  and  the  sacral  vertebrae ;  it  is 
excavated  on  its  internal  face.  The  ischium  partly  incloses  the  side  of  the  pelvic 
cavity  ;  between  its  internal  border  and  the  external  border  of  the  ilium  is  an 
•orifice  which  replaces  the  great  ischiatic  notch.     Its  inferior  border  is  united  to 


166  THE  BONES. 

the  pubis.  The  latter  (Fig.  109,  s")  is  thin  and  elongated,  and  follows  the 
direction  of  the  inferior  border  of  the  ischium,  with  it  circumscribing  an  oval 
opening  more  or  less  spacious  (Fig.  109,  22).  Its  inferior  extremity  extends 
beyond  the  ischium,  to  curve  inwards  towards  that  of  the  opposite  side,  but 
without  uniting  with  it.  We  do  not,  therefore,  find  the  pelvic  symphysis  in 
Birds,  and  the  pelvis  is  slightly  open  below,  a  circumstance  which  favours  the 
passage  of  the  egg  through  the  cavity  and  out  of  the  cloaca.  The  cotyloid  cavity 
is  perforated  by  an  opening  at  the  bottom,  which  passes  through  the  bone. 

Thigh-bone. — The  femur  (Fig.  109,  t)  is  articulated  inferiorly  with  the 
patella,  tibia,  and  fibula.  In  all  walking  Birds,  Uke  the  Gallinacge,  it  is  long 
and  strong,  as  well  as  the  bones  below  it. 

Leg-bones. — The  patella  (Fig.  109,  u)  is  wide  and  thin.  The  tiUa  (Fig. 
109,  v)  terminates,  below,  by  two  condyles  separated  by  a  groove,  which  becomes 
articular  behind.  The  fibula  (Fig.  109,  x)  articulates  by  its  head  with  the 
external  condyle  of  the  femur,  and  is  consolidated  with  the  tibia  ;  it  never 
descends  to  the  inferior  extremity  of  that  bone. 

Tarsal  bones. — The  tarsus  appears  to  be  altogether  absent  in  Birds.  Never- 
theless, we  may  venture  to  consider,  as  a  vestige  of  the  bones  of  this  region,  a 
small  bony  nucleus  buried  in  a  fibro-cartilaginous  mass  which  ghdes  on  the- 
posterior  pulley  of  the  tibia.  This  nucleus  (Fig.  109,  y)  represents  the  calcaneum 
of  Mammals. 

Metatarsal  bone. — A  single  metatarsal  bone  Ls  found  in  Birds,  articulating 
superiorly  with  the  inferior  extremity  of  the  tibia,  and  terminating  inferiorly  by 
three  pulleys  which  support  the  three  principal  digits.  This  bone  (Fig.  109,  y) 
shows  in  the  Fowl,  near  its  inferior  third,  a  conical  process  turned  backwards, 
which  serves  as  a  base  for  the  spur.  Behind  its  superior  extremity,  it  exhibits 
another  which  may  be  considered  as  a  consolidated  metatarsal  bone  (Fig. 
109,  23). 

Bones  of  the  (ligital  region  (Fig.  109,  z,  etc.). — All  the  domesticated  Birds  have 
four  digits  on  the  inferior  members  :  three  principal,  directed  forwards,  and  one 
rudimentary,  carried  backwards.  The  first,  designated  as  internal,  median,  and 
external,  articulate  with  the  inferior  pulleys  of  the  metatarsal  bones.  The  in- 
ternal is  formed  by  three  phalanges,  the  second  has  four,  and  the  third  five. 
These  phalanges  are  formed  something  like  those  of  the  Carnivora  ;  the  last  is 
pointed,  conical,  and  enveloped  in  a  horny  sheath.  The  fourth  digit,  or  thumb, 
is  composed  of  three  pieces  ;  one  of  these,  the  first,  is  generally  considered  as  a 
rudimentary  metatarsal  bone.  It  is  attached  by  fibro-cartilaginous  tissue  to  the 
inner  and  posterior  aspect  of  the  inferior  extremity  of  the  principal  metatarsal 
bone. 


THEORY  OF  THE  VERTEBRAL   CONSTITUTION  OF  THE  SKELETON.     167 


CHAPTER  IV. 

THEORY  OF  THE  VERTEBRAL  CONSTITUTION  OF  THE 
SKELETON. 

In  the  series  of  vertebrated  animals,  the  bony  pieces  of  the  trunk  bearing  the 
name  of  vertebrse  are  those  which  offer  the  highest  degree  of  fixity,  and  to  which 
the  existence  or  the  arrangement  of  the  others  appears  to  be  subordinate.  This 
feature  in  organization,  recognized  by  E.  Geoffroy  Saint-Hilaire  and  Professor 
Owen,  has  caused  these  authorities  to  assert  that  the  type  of  construction  of 
vertebrated  animals  is  the  vertebra. 

After  E.  Geoffroy  Saint-Hilaire  and  Professor  Owen,  several  German,  English, 
and  French  anatomists  have  studied  the  vertebral  composition  of  the  skeleton  ; 
and  among  the  works  published  in  France  on  this  subject,  must  be  specially 
noticed  those  of  Lavocat.  In  principle,  all  the  writers  have  arrived  at  the  same 
conclusions,  and  only  differ  in  some  few  details. 

It  is  certain  that  the  base  of  the  vertebral  column  is  formed  by  a  series  of 
bony  segments.  Each  of  these  segments  is  called  an  osteodesm,  and  each  osteo- 
desm  represents  the  bodi/  or  centrum  of  a  vertebra. 

In  examining  the  dorsal  region,  it  is  evident  that  to  the  body  or  centrum  of 
a  vertebra  are  added  two  complete  osseous  arches — a  superior  and  an  inferior. 
The  superior  arch  is  formed  by  the  vertebral  laminae  ;  the  inferior  by  the  ribs,  their 
cartilages,  and  a  portion  of  the  sternum.  The  first  is  designated  the  neural  arch, 
as  it  furnishes  a  protective  case  for  the  nervous  centres  ;  and  the  second,  which 
more  particularly  protects  the  vascular  system,  is  called  the  hcemal  arch  (see 
Figs.  112,  113). 

The  hfemal  arch  may  have  prolongations  or  appendices  more  or  less  developed, 
and  comparable  to  the  apophysary  prolongations  of  the  ribs  in  Birds  and  some 
Fishes. 

Such  is  the  general  composition  of  a  typical  vertebra  ;  but  there  are  also  to 
be  distinguished  in  the  neural  and  htemal  arches  the  following  parts  : — 


H^MAL   ARCH. 

1.  Haemal  parapophysis  =  the  tuberosity  of 

the  rib. 

2.  Haemal  metapophysis  =  the  head  of  the 

rib. 

3.  Haemal  diapophysis  =  the  rib  proper. 

4.  Hsemapophysis  =  the  costal  cartilage. 

5.  Haemal  spine  =  the  corresponding  sternal 

portion. 


NEURAL   ARCH. 

1.  Neural      parapophysis  =  the      posterior 

costal  cupola. 

2.  Neural  metapophysis  =  the  anterior  costal 

cupola. 

3.  Neural  diapophysis  =  the  summit  of  the 

transverse  process. 

4.  Neurapophysis  =  the  vertebral  lamina. 

5.  Neural  spine  =  the  summit  of  the  spinous 

process. 

The  vertebrae  sometimes  depart  more  or  less  from  the  model  just  described. 
They  may  vary  not  only  from  one  species  to  another,  but  also  in  the  same 
animal,  and  even  in  the  same  region.  Thus,  the  neural  arch  may  be  absent,  as 
has  been  observed  in  certain  coccygeal  vertebrae  ;  or  the  hsmal  arch  is  incom- 
plete or  null,  as  in  the  cervical  or  lumbar  vertebrae ;  or,  lastly,  the  arches  are 
often  unequal ;  though  this  inequality  is  of  no  importance,  since  their  size  is  in 
relation  to  the  volume  of  the  parts  they  should  protect. 

Notwithstanding  these  differences   and   variations,  or  the  transformations 


168 


THE  BONES. 


experienced  by  certain  parts,  there  is  not  a  bone  in  the  skeleton  which  cannot  be 
included  in  the  vertebral  type. 


Fig.  112. 


THORACIC   OR   PECTORAL   VERTEBRA 
OF    A    MAMMAL. 

C,  Centrum  ;  n,  neural  arch ;  h,  hsemal 
arch. 


Fig.  113. 


CAUDAL  VERTEBRA  OF  THE 
TURBOT. 

c,  Centrum  ,  n,  neural  arch  ; 
h,  hsemai  arch. 


The  vertebra  being  admitted  as  the  type  of  construction  of  the  skeleton,  it 
is  easy  to  find  it  in  all  the  regions  of  the  bony  framework.     In  the  thoraco- 

Fig.  114. 


CRANIAL  VERTEBRiE  OF  THE  DOG.   (AFTER  LAVOCAT.) 

1,  Occipito-hyoideal  vertebra;  2,  parieto-maxillary  vertebra;  3,  fronto-mandibular  vertebra; 
4,  naso-turbinal  vertebra. 


THEORY  OF  TEE  YERTEBRAL   CONSTITUTION  OF  THE  SKELETON.    169 

abdominal  region,  the  centrum,  neural  arch,  and  hsemal  arch  are  readily  per- 
ceived ;  for  in  the  lumbar  vertebrae,  the  enormously  developed  transverse  process 
indicates  the  existence  of  an  intra-vertebral  arch. 

In  the  sacral  region,  the  bony  girdle  of  the  pelvis  represents  the  hsemal  arch. 
The  posterior  limbs,  articulating  with  the  bones  of  the  pelvis,  also  belong  to  the 
hsemal  arch,  and  should  be  considered  as  appendices  of  this  arch,  analogous  to 
the  costal  appendices  of  birds. 

The  cervical  region  may  be  compared  to  the  sacral  region  ;  as  in  it  the 
inferior  haemal  arch  is  represented  by  the  osseous  ring  supporting  the  anterior 
hmbs — the  scapulo-clavicular  girdle.  The  limbs  themselves  are  appendices  of 
the  cervical  haemal  arch. 

Difficulties  begin  to  appear  when  the  extremities  of  the  trunk — the  head  and 
coccyx — come  to  be  examined.  Nevertheless,  the  composition  of  the  coccyx  is 
revealed  when  the  caudal  vertebrae  of  certain  Fishes,  especially  those  of  the 
Pleuronectidae,  in  which  the  neural  and  hsemal  arches  are  complete,  are  examined 
(Fig.  113).  But  the  vertebral  constitution  of  the  head  remained  for  a  long  time 
an  insoluble  question,  or  it  was  solved  in  a  contradictory  manner  by  the 
naturalists  who  attempted  it.  Some  admitted  a  single  cranial  vertebra  ;  others 
included  three  or  four  ;  while  others,  again,  found  six  or  seven. 

These  difficulties  and  contradictory  results  may  be  understood,  when  it  is 
borne  in  mind  what  profound  modifications  the  vertebra  must  have  undergone 
to  constitute  the  bones  of  the  head. 

At  present  the  problem  appears  solved.  The  head  is  composed  of  four 
vertebrae,  in  which  are  found  the  various  parts  enumerated  in  the  description  of 
the  typical  vertebra. 

In  the  four  classes  of  vertebrata,  the  head  is  constantly  formed  of  four 
vertebrse,  which  are  determined  as  follows,  according  to  Lavocat : — 


Vertebra. 

Centrum. 

Neural  arch. 

Hjemal  arch. 

Occipito-hyoideal. 

Basilar  process 
of  the   occipi- 
tal. 

Occipital  (3  pieces). 
Mastoid   walls  of  the 
tympanum. 

Hvoideal       apparatus 
('five  pieces). 

Parieto-maxillary. 

Body     of     the 
posterior  sphe- 
noid. 

Wing    and    pterygoid 
process   of    the    pos- 
terior sphenoid. 

S(iiiamnus  portion  and 
zygomatic  process  of 
the  temporal. 

Parietal. 

Inferior  maxilla   (five 
pieces). 

Froiito-manflibular. 

Body     of     the 
anterior   sphe- 
noid. 

Wing    and    pterygoid 
pr<'cess  of  the  anterior 
splienoid. 

Posterior  Frontal  and 
its  (irhital  process. 

Frontal. 

Malar. 

Laclirvnial. 

Palatine. 

Supermaxillary. 

Preriiaxillary. 

Naso  ttnbinal. 

Vomer. 

Ftlimoid. 

Nasal. 

Turbinated. 
Sub-ethmoidal. 

170  THE  ARTICULATIONS. 

The  number  of  cranial  vertebrae  is  invariable,  as  each  is  destined  to  lodge 
the  organs  of  one  of  the  four  senses.  The  occipito-hyoideal  receives  the  principal 
organs  of  hearing  ;  the  parieto-maxillary  osteodesm  protects  the  sense  of  taste  ; 
finally,  the  organs  of  vision  are  sustained  by  the  fronto-mandibular  vertebra, 
while  the  naso-turbinal  contains  the  sense  of  smell. 

Several  anatomists,  at  the  head  of  whom  are  Huxley  and  Gegenbauer,  do  not 
entirely  share  these  views.  They  certainly  admit  the  existence  of  the  occipital 
vertebra,  but  it  appears  to  them  to  be  impossible  to  recognize  the  others.  They 
remark  that  all  the  bones  which  constitute  the  spine  are  found  in  the  primary 
cartilaginous  skeleton  ;  so  that,  in  order  to  establish  the  vertebral  constitution 
of  the  head,  it  would  be  necessary  to  allot  to  the  same  cranial  vertebra  :  1.  The 
pieces  that  are  found  in  the  cartilaginous  cranium.  2.  The  other  pieces  which  are 
developed  in  the  fibrous  tissue — those  skeletal  tegumentary  pieces  (temporals, 
parietals,  etc.).  It  must  also  be  observed  that  the  division  into  vertebral  bodies 
of  the  parts  which  form  the  base  of  the  cranium,  far  from  being  easy  in  the  lowest 
animals,  is,  on  the  contrary,  only  possible,  with  some  trouble,  in  the  highest  classes. 
So  that  if  the  vertebral  constitution  of  the  head  were  a  fact,  it  must  be  admitted 
that  the  differentiation  of  the  bones  at  the  base  of  the  cranium  is  less  advanced 
in  Mammals  than  in  the  lower  vertebrates. 

The  vertebral  type  is  not,  therefore,  universally  accepted  by  all  anatomists. 


SECOND    SECTION. 

The  Articulations. 

THE  ARTICULATIONS  IN  GENERAL. 

The  different  pieces  constituting  the  solid  framework  of  the  animal  body  are,  a-s 
has  been  said,  united  in  such  a  manner  that  they  can  move  one  upon  the  other. 
From  this  union  results  the  articulations,  or  articular  joints,  the  construction 
of  which  will  now  be  referred  to  in  a  general  manner,  before  commencing  a 
particular  description  of  each. 

Arthrology,  or  Syndesmology ,  is  the  name  given  to  that  division  of  anatomy 
which  treats  of  the  articulations.  To  form  articulations,  the  bones  correspond 
with  each  other  by  certain  determined  points  of  their  periphery,  which  are  named 
articular  surfaces.  Every  articulation  is,  therefore,  essentially  constituted  by  two 
opposite  osseous  surfaces,  simple  or  complex,  which  are  moulded  to  each  other. 
These  are  either  contiguous,  independent,  and  very  movable — continuous  with 
each  other  by  means  of  a  cartilaginous  substance  which  confines  them,  if  not  to 
total  immobility,  at  least  to  very  limited  movements  ;  or  united  by  a  fibro- 
cartilage,  the  elasticity  of  which  permits  a  certain  degree  of  displacement  between 
the  bones  in  contact. 

In  the  first  case,  the  articulations  are  classed  as  diarthroses,  or  movable 
articulations. 

In  the  second,  they  are  designated  synarthroses,  sutures,  or  immovable 
articulations. 


THE  ARTICULATIONS  IN  GENERAL. 


171 


In  the  third,  they  are  amphiarthroses,  or  mixed  articulations;  so  termed 
because  they  participate  in  the  movements  of  the  other  two  classes  :  synarthroses, 
by  the  continuity  established  between  the  articular  surfaces  ;  and  diarthroses.  by 
the  extensive  motion  they  permit. 

The  general  characters  that  distinguish  each  of  these  three  great  classes  of 
articulations  will  be  successively  studied. 

Fig.  115. 


u 


rammiQ 


1^ 


a/ 

/ 

e 

V 

pn 

4  — 

fefjfjft 

PLANS  OF   THK   DIFFERENT   CLASSES  OP   ARTICULATIONS. 

A,  Suture:  1,  periosteum ;  2,sutural  ligament.  B,  Amphiarthrosis  :  a, first  degree— 1,  periosteum; 
2,  articular  cartilage  ;  3,  interarticular  ligament :  b,  second  degree — 4,  single  cavity  in  the 
interarticular  ligament :  c,  third  degree — 5,  double  cavity  in  the  interarticular  ligament.  C, 
Diarthrosis:  b,  simple  diarthrosis — 1,  periosteum;  2,  articular  cartilage;  3,  epithelial  layer  of 
the  synovial  membrane  (dotted  line)  ;  4,  fibrous  capsule ;  5,  cul-de-sac  of  the  synovial  membrane ; 
6,  fibrous  layer  of  the  synovial  membrane  :  c,  double  diarthrosis— 7,  interarticular  meniscus ;  8, 
9,  cavities  of  the  two  synovial  membranes. 


General  Characters  of  Diarthroses. 

"We  ought  to  consider,  in  the  diarthrodial  articulations  (Fig.  115,  c,  6  and  c)  : 
1.  The  contiguous  boni/  surfaces  which  form  them.  2.  The  cartilaginous  layers 
(cartilages  of  incrustation)  which  cover  these.  3.  The  fibrous  or  fibro-cartilagi- 
nous  tissue  {articular  fihro-cartilages)  which  complete  them,  when  they  are  not 
shaped  so  as  to  be  reciprocally  adapted  to  each  other.     4.  The  ligaments  which 


172 


THE  ARTICVLATIONS. 


maintain  them  in  contact.  5.  The  serous  membranes  {synovial  capsules)  that 
cover  the  internal  face  of  the  latter,  and  which  secrete  the  synovia,  a  kind  of 
animal  oil  that  facilitates  the  gliding  of  the  articular  surfaces.  6.  The  movements 
of  which  these  articulations  may  be  the  seat.  7.  Their  methodical  classification. 
8,  Their  nomenclature. 

Articular  Surfaces. — These  surfaces  have  the  common  character  of  being 
destitute  of  asperities,  so  that  they  can  glide  with  the  greatest  facility  on  each 
other.  They  are  designated,  according  to  their  form,  by  the  names  of  facets, 
heads,  condijles,  cotyles,  glenes,  pulleys,  etc.  There  is  no  need  to  revert  to  their 
general  description,  as  they  have  already  been  suihciently  studied  in  the  osteo- 
logy ;  so  we  will  confine  ourselves  to  repeating  that  they  are  found  at  the 
extremities  of  long  bones,  on  the  faces  of  short  bones,  and  on  the  angles  of  wide 
bones.  We  may  mention,  also,  that  they  are  often  excavated  by  one  or  several 
depressions  named  synovial  fossce,  or  hollows  for  the  insertion  of  ligaments.  The 
first  are  a  sort  of  natural  reservoirs  which  receive  the  unctuous  fluid  secreted  by 
the  interarticular  serous  membranes  ;  the  second  give  attachment  to  interosseous 
ligaments. 

Cartilages  of  Incrustation. — This  designation  is  given  to  the  layers  of 
cartilaginous  matter  which,  as  it  were,  varnish  the  articular  surfaces  they  adhere 

to  by  their  inner  face  ;  their  free  surface 
is  distinguished  by  a  remarkable  polish 
and  brilliancy.  Thicker  towards  the 
centre  than  at  the  circumference  when 
they  cover  bony  eminences,  these  carti- 
lages show  an  inverse  disposition  when 
they  line  cavities.  They  are  elastic,  of 
a  pearly  whiteness,  and  resisting — though 
they  are  soft  enough  to  be  cut  by  a  sharp 
instrument  ;  in  a  word,  they  possess  all 
the  physical  characteristics  of  the  primary 
cartilage  of  bones.  They  appear  to  be 
formed  of  parallel  fibres  placed  perpen- 
dicular to  the  bony  surfaces,  and  im- 
planted in  these  by  one  of  their  ex- 
tremities ;  the  opposite  extremity  corre- 
sponding to  the  free  surface  of  the 
cartilage.  Viewed  by  the  microscope, 
they  are  found  to  present  the  characters 
of  true  or  hyaline  cartilage. 
The  fundamental  matter  is  amorphous  and  homogeneous  ;  but  under  the 
influence  of  slight  dessication,  there  appears  in  the  hyaline  substance  a  partition- 
ing formation,  which  may  be  regarded  as  an  agent  in  the  distribution  of  the 
nutritive  juices  in  the  substance  of  the  cartilaginous  tissue  (Renaut). 

The  cavities  (cartilage  capsules)  are  irregular,  and  more  or  less  wide.  They 
contain  from  one  to  five  cells  without  walls,  and  their  contents — slightly  granular 
— have  in  the  centre  of  each  cell  one  or  two  nuclei  with  nucleoH  (Fig.  1 IG).  These 
cavities  are  elongated,  and  are  directed  almost  perpendicularly  towards  the  osseous 
articular  surface  in  the  deep  layer  ;  in  the  middle  layer  they  are  round  ;  and 
they  are  lenticular,  and  parallel  to  the  surface  of  friction,  in  the  superficial  layer. 
(It  has  been  stated  that  a  membrane  lines  these  spaces.     In  addition  to  the 


SECTION   OF   BRANCHIAL   CARTILAGE   OF 
TADPOLE. 

,  Group  of  four  cells  separating  from  each 
other ;  b.  pair  of  cells  in  apposition ;  c,  c, 
nuclei  of  cartilage-cells  ;  d,  cavity  contain- 
ing tiiree  cells.  These  cells  are  embedded 
in  the  finely  granular  matrix,  or  funda- 
mental substance. 


THE  ARTICULATIONS  IN   GENERAL. 


173 


granular  matter  observed  in  the  cells,  it  is  not  rare  to  find  fat  globules.  The 
nuclei  of  the  cells  vary  from  ^^V?  *o  Wmj  o^  8,n  inch  in  diameter.  The  cells 
multiply  eudogenously.) 

The  cartilage  cells  are  insoluble  in  boiling  water  ;  consequently,  so  far  as 
their  chemical  composition  is  concerned,  they  are  distinct  from  the  fundamental 
substance. 

The  diarthrodial  cartilages  have  no  vessels  or  nerves. 

The  presence  of  cartilages  of  incrustation  in  the  articulations  is  of  the  greatest 
importance.  When  they  are  worn,  absorbed,  or  transformed  into  bone  in  con- 
sequence of  certain  articular  maladies,  the  movements  become  painful  and  very 
difficult.     With  regard  to  the  part  they  play  in  the  economy,  it  may  be  said  that : 

1.  They  favour,  by  their  smoothness,  the  gliding  and  displacement  of  the  bones. 

2.  They  attenuate,  by  their  suppleness  and  elasticity,  the  violent  shocks  to  which 
the  articulations  are  exposed.  S.  They  resist  the  wear  and  deformation  of  the 
articular  surfaces. 

Complementary  Fibro-caetilages. — There  are  two  kinds  of  complementary 
fibro-cartilages.  Some  (interosseous)  represent  circular  cushions  which  pad  the 
margins  of  certain  cavi- 
ties, filling  up  the  notches  ^'  S-  ^  ^  '^• 
that  might  render  these 
imperfect.  They  in- 
crease the  depth  of  these 
cavities,  and  protect  their 
borders  from  in  j  ury — for 
example,  the  coxo-femo- 
ral  articulation.  Others 
(infer-articular)  are  in- 
terposed between  arti- 
cular surfaces  when  these 
do  not  exactly  fit  each 
other — as  when  two  opposing  extremities  are  convex.  It  may  be  remembered 
that  the  lateral  tuberosities  of  each  tibial  surface  present,  for  articulation  with  the 
condyles  of  the  femur,  two  convex  diarthrodial  faces,  the  coaptation  of  which  is 
rendered  perfect  by  the  interposition  between  each  condyle  and  corresponding 
tibial  surface,  of  a  crescent-shaped  fibro-cartilage,  which  for  this  reason  has  been 
named  a  meniscus.  In  other  joints,  these  interarticular  fibro-cartilages  are 
shaped  like  discs  or  biconcave  lenses.  There  then  result  double  diarthroses  (Fig. 
115,  C,  e)  :  example,  the  temporo-maxillary  articulation.  (Fibro-cartilage  also 
covers  bony  surfaces  over  which  the  tendons  play,  as  on  the  trochlear  surface  of 
the  humerus,  postero-inferior  face  of  the  navicular  bone,  and  elsewhere.  In 
these  situations  it  is  named  stratiform  fibro-cartilage.)  These  organs  are  formed 
sometimes  by  fibrous,  at  other  times  by  cartilaginous  tissue  ;  their  mode  of 
association  need  not  be  referred  to  here,  though  it  may  be  observed  that  the 
cartilage  is  more  particularly  found  in  all  those  points  where  there  is  most 
articular  friction.  They  receive  very  few  vessels,  and  it  is  questionable  if  they 
have  nerves. 

Ligaments. — These  are  bands  which  unite  contiguous  diarthrodial  surfaces. 
They  are  sometimes  formed  of  white  fibrous  tissue,  and  sometimes  of  yellow  ; 
hence  their  division  into  two  great  classes  of  white  and  yeUoiv  ligaments. 

a.  The  white  ligaments  are  distinguished  by  the  pearly  whiteness  of  their 
14 


FIBRO-CARTILAGE,    MAGNIFIED    155    TIMES. 

Showing  interlacement  of  fibrous  fasciculi,  with  scattered 
groups  of  cartilage-cells. 


174 


THE  ARTICULATIONS. 


tissue  and  want  of  elasticity.  Those  which  are  found  around  the  margin  of 
articulations  are  termed  peripheral,  and  those  in  their  interior  are  designated 
interosseous  or  interarticular  ligaments. 

The  peripheral  ligaments  are  g^erallj  composed  of  parallel  fibres  collected  in 
fasciculi,  or  spread  out  as  membranes.  In  the  first  they  are  called  funicular,  or 
riMon-shaped ;  in  the  second,  they  are  termed  membraniform,  or  capsidar.  The 
funicular  ligaments  are  short,  round,  or  flattened  bands,  attached  by  their 
extremities  to  the  two  bones  they  unite  ;  they  are  lined  on  their  inner  aspect 
by  the  synovial  capsule,  and  are  covered  .externally  by  tendons,  aponeuroses, 
muscles,  vessels,  or  nerves.     The  capsular  ligaments  are  often  complete — that  is 


Fig.  118. 


Fig.  119. 

^^S 

Wl^m^^UJSlfmije'^^M^KplMwMl'' 

WHITE   OR    NON-ELASTIC   FIBBOUS 

TISSUE. 


YELLOW    OR    ELASTIC   FIBROUS  TISSUE, 
THE   LIGAMENTUM    NUCH^E. 


to  say,  they  envelop  the  whole  articulation  like  a  sack.  At  other  times  they  are 
incomplete,  and  then  they  are  simple  membranes,  binding  together  the  different 
funicular  ligaments  of  a  joint. 

The  interosseous  ligaments — less  numerous  than  the  preceding — are  often  formed 
of  interlacing  fibres ;  they  are  always  funicular,  and  fixed  by  their  extremities 
into  excavations  in  the  centre  of  articular  surfaces. 

J.  Hhe  yellow  ligaments  are  2k[[  perijyheral,  funicular,  or  7nembranous,  and  enjoy 
a  marked  degree  of  elasticity,  which  permits  them  mechanically  to  bring  back  to 
their  usual  position  the  bony  levers  that  have  been  momentarily  displaced.  These 
ligaments,  which  are  powerful  auxiliaries  to  the  muscular  forces,  give  permanent 
equilibrium  to  the  weight  in  certain  parts  of  the  body,  which  incessantly  tend  to 
fall  to  the  ground  ;  for  instance,  the  cervical  ligament  of  Solipeds  and  large 
Ruminants.  The  ligaments  are  always  assisted  in  their  action  by  atmospheric 
pressure,  which  is  exerted  over  all  the  surface  of  the  body  ;  and  also  frequently  by 
the  tendons  and  aponeurosis  of  muscles,  and  even  by  the  muscles  themselves, 
when  they  pass  over  an  articulation  or  are  inserted  in  its  vicinity.  In  several 
regions  the  ligaments  are  more  or  less  confounded  w^ith  tendons  or  aponeiu-oses — 
as  in  the  anterior  extensor  tendon  of  the  phalanges  and  superior  sesamoid  liga- 
ment, the  ligaments  of  the  femoro-tibial  articulation,  and  the  aponeuroses  of  the 
posterior  portion  of  the  superficial  gluteal  muscle. 

Synovial  Capsules. — These  are  very  thin  membranes  of  a  serous  character, 
intended  to  secrete  the  synovia.  They  are  composed  of  two  layers  :  a  deep, 
formed  by  fasciculi  of  connective  tissue  ;  the  other,  superficial,  formed  by  an 


THE  ABTIGULATIONS  IN  GENERAL.  175 

endothelium.  The  first  sometimes  adheres  intimately  to  the  inner  face  of  the 
funicular  or  membranous  ligaments  of  the  articulation  ;  at  other  times  it  is  loosely- 
attached  to  them  by  an  abundance  of  connective  tissue.  The  second  layer  is  con- 
stituted by  a  single  row  of  flattened  polygonal  cells,  except  at  the  bottom  of 
certain  grooves,  where  they  are  more  or  less  crowded.  Though  belonging  to  the 
serous  membranes,  the  synovial  membranes  do  not  form  complete  sacs,  as,  after 
lining  the  internal  surface  of  the  ligaments,  they  cease  at  the  articular  margins. 

Direct  observation  demonstrates  that  the  cartilages  have  no  covering,  and 
that  there  is  no  synovial  membrane  on  their  surface.  The  anatomists  who 
imagined  that  the  thin  pellicle,  which  can  be  rendered  evident  in  cutting  the 
surface  of  cartilage  obliquely  and  separating  it  by  teazing,  was  a  membrane,  were 
deceived,  as  this  pellicle  has  not  the  texture  of  a  serous  membrane  ;  and  it  is  not 
vascular,  for  it  has  never  been  possible  to  inject  vessels  on  the  surface  of  such 
cartilages,  nor  yet  in  their  substance.  Neither  is  it  covered  with  epithelium,  and, 
if  submitted  to  microscopical  examination,  it  has  all  the  characters  of  cartilage. 

Pathological  facts  prove  nothing  in  favour  of  the  existence  of  a  synovial 
membrane  on  cartilages. 

It  may  be  accepted,  then,  that  the  synovial  membrane  never  extends  to  the 
surface  of  articular  cartilage  ;  but,  after  being  fixed  around  the  margin  of  a 
diarthrodial  surface,  it  is  reflected  in  every  direction  to  line  the  internal  surface 
of  the  ligaments,  and  become  attached  to  the  periphery  of  the  diarthrodial  surface 
in  contact  with  the  other,  so  that  it  entirely  isolates  the  interior  of  the  joint  from 
the  peri-articular  connective  tissue. 

There  are  generally  found  within  articulations,  little  masses  of  fat  which  push 
the  synovial  membrane  enveloping  them  inwards.  Erroneously  considered  by 
Clopton  Havers  as  glands  for  the  secretion  of  synovia,  these  accumulations  of  fat 
have  been  named  synovial  fringes,-  ot  villi.  They  are  more  particularly  numerous 
in  the  neighbourhood  of  the  articular  margins — that  is,  on  the  border  of  diarthro- 
dial surfaces.  They  are  formed  by  a  prolongation  of  the  synovial  membrane, 
which  covers  some  connective  tissue  fibres  associated  with  adipose  cells,  or  an 
amorphous  substance  provided  with  nuclei. 

The  synovial  membrane,  after  lining  the  inner  surface  of  ligaments,  sometimes 
escapes  between  these,  forming  a  hernia.  The  term  synovial  culs-de-sac  has  been 
given  to  these  external  prolongations  of  the  articular  serous  membrane.  This 
membrane  often  covers  the  inner  surface  of  a  tendon  or  ligament,  in  order  to 
facilitate  their  gliding  over  a  bony  eminence. 

The  synovia  is  a  viscid,  colourless,  or  slightly  yellow  fluid,  in  its  physical 
characters  somewhat  resembling  oil ;  it  does  not  possess  them,  however,  so  far  as 
its  composition  is  concerned,  for  chemical  analysis  has  not  demonstrated  the 
presence  of  fatty  principles.  It  is  the  albumen  it  contains  which  gives  to  it  its 
viscidity,  and  which  fits  it  for  lubricating  the  articular  surfaces  over  which  it  is 
spread.  Its  use  in  the  animal  economy  is  absolutely  identical  with  that  of  the 
greasy  substances  employed  to  luliricate  the  axles  of  carriages. 

To  the  means  of  union  described  under  the  names  of  ligaments  and  synovial 
membranes,  may  be  added  atmospheric  pressure,  the  influence  of  which  is 
relatively  considerable,  as  the  experiments  of  Weber  have  demonstrated. 

Movements. — The  movements  peculiar  to  diarthrodial  articulations  are 
divided  into  seven  principal  classes  : 

1.  Simple  gliding,  the  only  movement  possible  between  two  plane  or  undu- 
lating facets. 


176  THE  ARTICULATIONS. 

2.  Flexion,  which  brings  two  bony  pieces  nearer  each  other,  by  closing  more 

or  less  their  angle  of  union. 

3.  Extension,  the  inverse  movement,  during  which  the  bones  are  straightened 

on  each  other. 

4.  Adduction,  which  brings  the  inferior  extremity  of  the  movable  bone  towards 

the  median  line. 

5.  Abduction,  the  contrary  movement  to  the  preceding. 

6.  Circumduction,  or  the  sling  movement,  during  which  the  bone  passes 

successively  through  the  last  four  positions. 

7.  Rotation,  in  which  one  bone  pivots  on  another. 

Classification  of  the  Diarthroses. — The  basis  of  this  classification  is 
founded  on  the  configuration  of  the  articular  surfaces  and  the  nature  of  the 
movements  they  permit.  This  double  base  serves  to  establish  five  kinds  of 
diathrodial  articulation  : 

1.  Enr/rfhrosis,  characterized  by  the  reception  of  an  articular  head  within  a 
cavity  of  appropriate  form.  This  articulation,  the  surfaces  of  which  are  derived 
from  a  sphere,  may  be  the  seat  of  the  most  extensive  and  varied  movements — 
flexion,  extension,  abduction,  adduction,  circumduction,  and  rotation.  Example  : 
the  coxo-femoral  articulation. 

2.  The  trochlea?!,  angular  ginglymoid,  or  perfect  hinge  articulation,  when  the 
articular  surfaces  are  formed  into  trochlea,  reciprocally  fitting  into  each  other, 
and  the  movements  of  which — flexion  and  extension  only — are  executed,  from 
before  to  behind,  with  the  precision  of  a  hinge.  Example  :  the  tibio-tarsal 
articulation. 

3.  The  piiwt,  trochoid,  or  lateral  ginglymoid  articulation,  is  a  diarthrosis  formed 
by  a  pivot  which  turns  in  a  semi-cylindrical  cavity.  Rotation  is  the  only  move- 
ment.    Example  :  the  atlo-axoid  articulation.  • 

4.  The  condyloid,  or  imperfect  hinge  articulation,  which  permits,  like  the 
preceding,  the  two  principal  movements  of  extension  and  flexion,  and  the  acces- 
sory movements  of  rotation  or  lateral  inclination.  The  articular  surfaces,  though 
very  diversely  shaped,  nevertheless  exhibit  in  all  the  articulations  one  or  more 
condyles  opposed  to  an  equal  number  of  oval  excavations.  Example  :  the  femoro- 
tibial  articulation. 

5.  Arthrodia,  or  'plamform  diarthrosis,  is  constituted  by  plane  or  nearly  plane 
iacets.  Gliding  is  the  only  possible  movement.  Example  :  the  carpo-metacarpal 
articulation. 

Nomenclature. — The  names  of  the  articulations  are  usually  those  of  the 
bones  which  form  them.  For  instance,  the  scapulo-humeral  articulation  is  the 
joint  between  the  scapula  and  humerus  ;  the  intervertehrnl  articulations  join  to 
each  other  the  various  bones  constituting  the  spine.  When  the  qualifying  name 
of  an  articulation  is  composed  of  two  elements,  as  in  the  first  instance,  it  is  well 
to  place  first  the  word  which  indicates  the  bone  usually  most  fixed. 

General  Characters  of  the  Synarthroses. 

Sutures  (Fig.  1 1 5,  a)  are  the  temporary  articulations  which  exist  only  at  an  early 
period  of  life.  They  nearly  all  disappear  in  the  adult  animal,  in  consequence  of 
the  bones  forming  them  becoming  consolidated.  They  belong  almost  exclusively 
to  the  bones  of  the  head. 

Articular  Surfaces. — The  bones  forming  these  come  in  contact  by  their 


THE  ARTICULATIONS  IN  GENERAL.  177 

borders  or  angles,  which,  for  this  purpose,  generally  present  very  uneven 
surfaces. 

Sometimes  they  arc  cut  perpendicularly  and  simply  roughened  ;  at  other  times 
they  are  bevelled,  and  joined  by  means  of  fine  laminse  or  trifling  inequalities  ; 
again,  they  are  notched  into  deep  and  sinuous  dentations  ;  and  lastly,  one  bone 
is  fixed  into  a  groove  cut  in  the  other.  It  will  be  understood  that  such  formations 
of  the  articular  surfaces  will  limit  their  movements,  and  assure  the  solidity  of 
their  union. 

Modes  of  Union, — A  fibrous  tissue  interposed  between  these  synarthrodia! 
surfaces,  unites  them  closely  to  each  other.  It  has  absolutely  the  same  texture  as 
the  primary  cartilage  of  the  bones,  and,  like  it,  possesses  the  property  of  becoming 
ossified  after  having  been  vascularized.  This  ossification,  which  causes  the 
disapppearance  of  the  sutures,  occurs  earlier  inwards  than  outwards.  The 
periosteum,  in  passing  from  one  bone  to  another,  also  concurs  in  bringing  about 
a  more  complete  synarthrosis.  It  should,  therefore,  be  included  in  their  means 
of  union. 

Movements. — These  are  very  obscure,  and  only  noticeable  in  young  animals, 
by  the  elasticity  they  communicate  to  the  bony  walls  of  the  cranium  or  face.  In 
the  adult,  they  may  be  said  to  be  null. 

Classification. — Tliere  are  four  principal  descriptions  of  sutures  .- 

1.  When  two  wide  bones  correspond  by  means  of  denticulations  fitting  into 
each  other,  the  suture  is  named  frup,  Umhosa,  serrated,  or  dentated.  Example  : 
the  articulations  unitmg  the  three  portions  of  the  parietal  bone.  2.  If  the  opposite 
borders  of  two  bones  in  contact  are  widely  bevelled,  one  inwards,  the  other  out- 
wards, it  forms  a  scaly  or  squamous  suture  {squamosa).  Example  :  the  parieto- 
temporal articulations.  3.  When  the  union  of  bones  takes  place  by  plane  or 
roughened  surfaces,  cut  perpendicularly  on  their  borders  or  angles  ;  this  constitutes 
the  harmoaia  suture,  or  suture  hij  juxtaposition  (or  apposition).  Example  :  the 
occipito-temporal  articulations.  4.  The  schiruii/Iesis,  mortised  suture,  synchron- 
drosis,  or  gomphosis,  results  from  the  reception  of  a  bony  plate  into  a  groove  more 
or  less  deep  in  another  bone.  Examples  :  the  spheno-frontal  and  supermaxillo-nasal 
articulations  ;  the  teeth  in  the  alveolar  cavities. 

General  Characters  of  the  Amphiarthroses  or  Symphyses. 

Articulae  Surfaces. — They  are  frequently  smooth,  and  formed  almost  on 
the  same  model  as  the  diarthrodial  surfaces.  They  are  covered  by  a  thin  layer  of 
cartilage  ;  but,  instead  of  being  smooth  and  polished,  they  are  more  or  less  rugged, 
without,  however,  presenting  the  anfractuous  disposition  of  the  majority  of  synar- 
throdia! surfaces. 

Modes  of  Union. — The  organs  which  perform  this  office  are  :  1.  Fibro- 
cartilage,  which  establishes  continuity  between  the  articular  surfaces.  2.  Ribbon- 
shaped  and  peripheral  ligaments  (Fig.  115,  b  a).  These  latter  do  not  differ  from 
the  analogous  bands  attaching  the  diarthrodial  articulations.  With  regard  to  the 
fibro-cartilage,  it  is  distinguished  from  the  complementary  discs  of  these  same 
articulations,  by  a  less  intimate  mixture  of  the  cartilaginous  and  fibrous  elements 
entering  into  its  composition.  The  last  may  be  sometimes  absent,  as  well  as  the 
peripheral  bands  ;  and  then  the  articulation  only  differs  from  the  synarthroses  by 
the  extent  of  motion  it  permits.  Occasionally,  the  interarticular  fibro-cartilages 
are  excavated  by  one  or  two  little  narrow  cavities  (Fig.  115,  b  b,  c)  ;  but  these 
are  never  lined  by  a  synovial  membrane,  like  the  diarthrodial  cavities. 


178  THE  ARTICULATIONS. 

Movements. — The  amphiarthroses  only  permit  of  a  see-saw  or  swinging 
movement,  the  extent  of  which  depends  on  the  thickness  of  the  intermediate 
fibro-cartilage. 

Classification. — Only  one  kind  of  amphiarthrosis  is  recognized  in  the  Horse, 
the  most,  remarkable  of  which  is  found  in  the  articulations  between  the  bodies  of 
the  vertebrae. 


CHAPTER   II. 

ARTICULATIONS   OF   MAMMALIA  IN   PARTICULAR. 

In  the  special  study  of  the  articulations,  the  same  order  will  be  followed  as  for  the 
bones  ;  the  articulations  of  the  spine  will  be  first  noticed,  then  those  of  the  head, 
thorax,  and  anterior  and  posterior  limbs. 

Preparation. — The  preparation  of  the  bones  which  have  been  described,  has  not  been  made 
the  subject  of  any  particular  recommendation,  because  it  suffices,  in  order  to  study  them,  to 
remove  the  soft  parts  by  which  they  are  surrounded,  either  by  boiling,  maceration,  or  scraping. 
But  when  we  come  to  examine  the  soft  textures,  in  order  to  do  so  profitably  it  is  necessary  to 
learn  beforehand  the  rules  whicli  should  be  followed  in  their  preparation.  The  following 
directions  are  given  with  regard  to  the  study  of  the  articulations : — 

1.  To  prepare  the  articulations,  young  subjects  are  cliosen  in  preference  to  those  advanced 
in  years,  because  the  density  of  tlie  connective  tissue  in  them  is  not  so  great,  and  this  tissue  is 
easily  removed  from  around  the  ligaments.  As  tiiese  are  prepared  with  difficulty  when  the 
external  surface  is  in  a  dry  state,  care  should  be  taken,  before  dissecting  them,  to  have  them 
excluded  from  the  air  by  covering  them  with  damp  cloths,  or  with  the  skin  of  the  animal. 

2.  It  is  convenient  to  separate  the  articulation  we  wish  to  dissect,  by  sawing  through  the 
bones  at  a  certain  distance  from  the  articular  surfaces.  The  manipulation  of  the  part  is  then 
rendered  easier,  and  its  dissection  can  be  made  under  the  most  favourable  conditions. 

3.  It  is  necessary  to  preserve,  as  carefully  as  possible,  the  muscles  surrounding  the  articula- 
tions, in  order  to  be  able  to  study  their  relations  with  the  ligaments  which  bind  these.  If  it 
be  absolutely  requisite  to  remove  them,  their  insertions  corresponding  to  the  articulation 
should  always  be  retained. 

4.  The  capsular  ligaments  should  be  first  studied,  as  they  have  soon  to  be  removed,  the 
better  to  show  the  funicular  ligaments.  Tliese,  in  their  turn,  must  be  sacrificed  in  order  to 
display,  by  different  sections,  the  interosseous  ligaments,  when  they  are  present.  Lastly,  the 
two  articular  surfaces  should  be  completely  separated,  so  as  to  examine  their  conformation. 

5.  The  synovial  membranes,  with  their  different  cuU-de-sac,  being  a  very  important  study — 
with  reference  to  the  diagnosis  and  treatment  of  articular  tumours — it  is  convenient  to  devote  a 
special  piece  to  the  examination  of  these  serous  membranes.  It  is  very  useful  to  inject  their 
interior  with  plaster  or  tallow  coloured  black,  in  order  to  distend  their  cavities,  and  thus  aid 
the  study  of  their  relations  with  ligaments,  tendons,  or  muscles. 

6.  When  an  articulation  is  completely  dissected,  it  may  be  left  exposed  to  the  air  for  some 
time.     When  the  ligaments  begin  to  dry,  they  are  more  visible  and  easier  studied. 

For  the  preparation  of  each  articulation  it  is  not  necessary  to  give  any  directions ;  a  glance 
at  the  figures  accompanying  the  description  will  suffice  to  dispel  any  embarrassment  the 
student  may  experience,  while  he  always  requires  particular  indications. 

Article  I. — Articulations  of  the  Spine. 
These  articulations  comprise  all  those  of  the  vertebrse  with  each  other. 

Preparation. — In  order  to  properly  study  the  vertebral  joints,  the  spine  of  one  subject 
should  be  freed  from  all  tlie  muscles  surrounding  it;  this  being  done,  portions  consisting  of  at 
least  two  vertebrse  from  the  cervical,  dorsal,  and  lumbar  regions,  should  be  detached  trum  it. 
In  the  portions  from  the  cervical  regions,  the  interlamellar  ligaments  and  the  capsules  of  the 


ARTICULATIONS  OF  TEE  SPINE.  179 

articular  processes  are  easily  dissected ;  and  on  the  dorsal  region  portions,  the  interspinous, 
Bupra-spinous,  interlamellar,  and  common  inferior  ligaments,  can  be  examined.  On  those 
portions  from  the  lumbar  region,  in  a  horizontal  section  through  the  spinal  canal,  the  inferior 
face  of  the  interlamellar  ligaments  and  the  common  superior  vertebral  ligament  will  be  seen ; 
while  in  those  from  the  dorsal  region,  a  good  idea  will  be  derived  of  the  common  inferior 
vertebral  ligament.  The  intervertebral  ligaments  can  be  studied  in  vertical  and  horizontal 
eections  of  the  bodies  of  the  vertebrae  from  any  region. 

A  second  subject,  which  should  be  fixed  in  the  third  position  (see  Preparation  of  the 
Muscles),  is  necessary  for  the  dissection  of  the  supra-spinous,  dorso-lumbar,  and  cervical 
ligament.  This  may  be  eflPected  by  removing  the  muscles  which  occupy  the  vertical  channels 
above  the  cervical  vertebrse  (see  Preparation  of  the  Cervical  Kegions). 

Intervertebral  Articulations. 

The  vertebrae  articulate  :  1.  By  their  bodies.  2.  By  their  spinal  or  annular 
portion.  There  results  from  this  union  two  kinds  of  articulation,  which  must  be 
studied  separately,  as  they  do  not  belong  to  the  same  class.  It  is  well  to  mention, 
however,  that  the  general  details  into  which  this  study  leads  us,  apply  only  to 
the  articulations  uniting  the  last  six  cervical  vertebrae,  all  the  dorsal  and  lumbar 
vertebrae,  and  the  first  sacral  vertebra. 

Union  op  the  Vertebra  by  their  Bodies. — The  articulations  forming 
this  union  are  so  many  amphiarthroses. 

Articular  surfaces. — The  vertebral  bodies  come  into  contact  by  the  surfaces 
which  terminate  them  before  and  behind.  In  the  cervical  region  these  surfaces 
represent,  anteriorly,  a  real  head  ;  posteriorly,  a  cotyloid  cavity  which  receives  the 
head  of  the  next  vertebra.  Beginning  from  the  first  dorsal  vertebra  and  passing 
on  to  the  sacrum,  these  surfaces  tend  to  become  effaced  and  more  and  more 
plane,  though  they  still  preserve  their  convexity  and  concavity. 

Means  of  union. — 1.  By  fibro-cartilages  interposed  between  the  articular 
surfaces.  2.  By  a  common  superior  vertebral  ligament.  3.  By  a  common 
inferior  vertebral  ligament, 

a.  Intervertebral  fihro-cartilages  (Fig.  121,  1,  1). — These  are  circular  or 
elliptical  discs,  convex  in  front,  concave  behind,  and  soUdly  fixed  by  their  faces 
to  the  articular  planes  which  they  separate.  The  fibro-cartilaginous  substance 
composing  them  consists  of  concentric  layers,  which  become  denser  and  closer  to 
each  other  as  they  near  the  circumference  ;  they  even  disappear  towards  the 
centre  of  the  disc,  where  this  substance  becomes  pulpy,  and  assumes  the  histo- 
logical characters  of  pure  cartilage.  It  may  be  remarked,  that  each  of  these 
layers  is  made  up  of  a  collection  of  thick  parallel  filaments,  which  cross  with 
those  of  other  layers  Hke  an  X,  and  are  attached  by  their  extremities  to  the 
articular  surfaces.  From  this  aiTangement  results  so  intimate  an  adherence 
between  the  vertebral  bodies  and  their  intermediate  fibro-cartilages,  that  an 
attempt  to  disunite  them  is  more  likely  to  cause  a  fracture  of  the  former.  The 
fibro-cartilages,  thicker  in  the  cervical  and  lumber  regions  than  in  the  dorsal, 
respond  by  their  circumference  to  the  two  common  ligaments.  Those  which 
separate  the  vertebrte  of  the  back  concur  to  form  the  intervertebral  cavities, 
intended  for  the  reception  of  the  heads  of  the  ribs,  and  give  attachment  to  the 
interosseous  costo-vertebral  ligaments. 

h.  Common  superior  vertebral  ligament  (Fig.  126,  1). — This  ligament  extends 
from  the  axis  to  the  sacrum,  and  is  lodged  in  the  spinal  canal.  It  is  a  long 
fibrous  band  cut  on  its  borders  into  wide  festoons.  By  its  inferior  face,  it  is 
attached  to  the  intervertebral  discs,  and  the  triangular  imprints  on  the  upper 
faces  of  the  bodies  of  the  vertebrte.     Its  superior  face  is  in  contact  with  the  dura 


180  THE  ARTICULATIONS. 

mater,  tlirough  the  medium  of  an  abundant  cellulo-adipose  tissue.  Its  borders 
are  margined  by  the  intra-vertebral  venous  sinuses  (venm  basium  vertehrarium). 

c.  Common  inferior  vertebral  ligament  (Fig.  127,  5). — Situated  under  the 
spine,  this  ligament  is  absent  in  the  cervical,  and  the  anterior  third  of  the  dorsal 
region.  It  only  really  begins  about  the  sixth  or  eighth  vertebra  of  the  latter 
region,  and  is  prolonged  in  the  form  of  a  cord — at  first  narrow,  then  gradually 
widening  until  it  reaches  the  sacrum,  on  the  inferior  surface  of  which  it 
terminates  by  a  decreasing  expansion.  From  its  commencement,  it  is  attached  to 
the  inferior  crests  of  the  bodies  of  the  vertebrae  and  the  intervertebral  discs.  By 
its  inferior  face,  it  is  in  contact  with  the  posterior  aorta. 

(Leyh  commences  this  ligament  at  the  seventh  cervical  vertebra,  and  says 
that  it  adheres  to  the  crests  on  the  bodies  of  the  dorsal  and  lumbar  vertebrae,  as 
well  as  to  the  lower  face  of  the  sacrum  and  coccyx.  At  the  fifth  dorsal  vertebra 
it  widens  and  thickens,  and  in  the  lumbar  region  is  bound  up  with  the  pillars 
of  the  diaphragm,  and  confounded  on  each  side  with  the  large  ligaments  of  the 
pelvis.) 

Union  of  the  Vertebra  by  their  Spinal  Portions. — Each  vertebra,  in 
uniting  by  its  annular  portion  with  that  which  follows  or  precedes  it,  forms  a 
double  arthrodial  joint. 

Articular  surfaces. — These  are  the  facets  cut  on  the  anterior  or  posterior 
articular  processes,  and  which  have  been  described  when  speaking  of  the  vertebrse 
themselves.     They  are  covered  by  a  thin  layer  of  cartilage. 

Means  of  union. — 1.  A  common  supra-spinous  ligament.  2.  Interspinous 
ligaments.  3.  Interlamellar  ligaments.  4.  Ligamentous  capsules,  proper  to  the 
articular  processes. 

a.  Capsules  proper  to  the  articular  processes  (Fig.  124,  5). — Each  anterior 
articular  process  is  maintained  against  the  corresponding  posterior  process,  by  a 
direct  band.  This  is  a  peripheric  capsule  attached  around  the  diarthrodial  facets, 
lined  by  a  synovial  membrane  which  facilitates  their  gliding,  and  covered, 
outwardly,  by  the  insertions  of  some  spinal  muscles.  These  capsules,  yellow  and 
elastic  in  the  cervical  region,  are  composed  of  white  fibrous  tissue  in  the  dorso- 
lumbar  region.  Very  developed  at  the  neck,  in  consequence  of  the  thickness  of 
the  articular  tubercles  they  envelop,  they  become  reduced,  near  the  middle  of 
the  back,  to  some  fibres  which  cover,  outwardly,  the  diarthrodial  facets  in 
contact. 

b.  Common  supraspinous  ligament. — This  ligament,  the  name  of  which  suffi- 
ciently indicates  its  situation,  extends  from  the  sacrum  to  the  occipital  bone,  and  is 
divided  into  two  portions — one  posterior,  or  supraspinous  dor  so-lumbar  ligament  ; 
the  other  anterior,  or  supraspinous  cervical  ligament.  These  two  ligaments, 
although  continuous  with  one  another,  yet  differ  so  strikins^ly  in  form  and 
structure  that  they  are  best  described  separately. 

1.  Supra-dorso-lumbar  ligament  (Fig.  127,  2). — This  is  a  cord  of  white 
fibrous  tissue,  which  commences  behind  on  the  sacral  spine,  and  ceases  in  front, 
about  the  inferior  third  of  the  dorsal  region,  by  insensibly  assuming  the  texture 
and  elasticity  of  the  cervical  ligament,  with  which  it  is  continuous.  It  is  attached 
in  its  course  to  the  summits  of  all  the  lumbar  spinous  processes,  and  to  the  ten  or 
twelve  last  dorsal.  On  the  sacral  spine,  it  is  confounded  with  the  superior 
ilio-sacral  ligaments.  In  the  lumbar  region,  it  is  united  on  each  side  to  the 
aponeuroses  of  the  longissimus  dorsi  muscles. 

2.  Supraspinous  cervical,  or  simply  cervical  ligament  {ligamentum  nucha,  liga- 


ARTICULATIONS   OF  THE  SPINE. 


181 


mmtum  colli)  (Fig.  120,  1,  2). — This  ligament  is  entirely  formed  of  yellow 
fibrous  tissue,  and  constitutes,  in  the  median  plane  of  the  body,  a  very  remarkable 
elastic  apparatus,  which  separates  the  superior  cervical  muscles  of  the  right  side 
from  those  of  the  left,  and  plays  the  part  not  entirely  of  an  articular  band,  but 
rather  of  a  permanent  stay,  charged  to  balance  the  weight  of  the  head. 

In  the  cervical  ligament  there  is  distinguished  a  fumriiJar  and  a  lamellar 
portion.  The  first,  usually  called  the  cord  {funicular  or  cordiform  portion)  of  the 
ligament,  is  a  wide  funiculus  which  extends  directly  from  the  first  dorsal  spinous 

Fig.  120. 


CERVICAL   LIGAMENT   AND   DEEP   MUSCLES   OF    THE   HORSE  S   NECK. 

1,  Lamellar  portion  of  the  cervical  ligament ;  2,  funicular  portion  of  the  same. 


processes  to  the  summit  of  the  head.  Divided  into  two  lateral  lips  by  a  median 
groove,  this  cord  is  continued  posteriorly  by  the  dorso-lumbar  ligament,  and  is 
inserted,  anteriorly,  into  the  tuberosity  of  the  occipital  bone.  It  is  covered  above 
by  a  mass  of  fibro-adipose  tissue,  which,  in  certain  common-bred  horses,  is  very 
abundant.  Below,  it  gives  rise,  in  its  posterior  two-thirds,  to  the  majority  of  the 
fibres  belonging  to  the  lamellar  portion.  On  the  sides,  it  receives  the  insertions 
of  several  cervical  muscles.  The  lamellar  portion — comprised  between  the  funicular 
portion,  the  spinous  processes  of  the  second  dorsal  vertebra,  and  the  cervical 


182 


THE  ARTICULATIONS. 


vertebrae,  constitutes  a  vast  triangular  and  vertical  septum,  which  itself  results  from 
the  apposition  of  the  two  laminae  that  lie  back  to  back,  and  are  united  by 
connective  tissue  ;  they  are  bordered  above  by  the  two  lateral  lips  of  the  cord.  The 
elastic  fibres  which  enter  into  their  composition  are  given  off  either  from  the 
latter,  or  from  the  spinous  processes  of  the  second  and  third  dorsal  vertebrae ; 
they  are  directed  downwards  or  forwards,  and  reach  the  spinous  processes  of  the 
last  six  cervical  vertebrae,  into  which  they  are  inserted  by  so  many  digitations, 
becoming  confounded  with  the  interspinous  ligaments  of  the  neck.  The  fibres 
of  the  two  last  digitations  are  few  in  number,  widely  separated  from  one  another, 
and  united  by  many  anastomosing  branches,  which  make  them  appear  as  a  kind 
of  wide  network.  The  lamina  of  the  cervical  ligament  are  in  relation,  outwardly, 
with  the  superior  branch  of  the  ilio-spinal  ligament,  the  intertransversalis  colli 
muscles,  and  the  complexus  muscle. 

(This  important  structure,  which  is,  in  reality, 
the  mechanical  stay  and  support  of  the  heavy  head 
and  neck  of  quadrupeds,  and  is  usually  temied  the 
ligamentvm  nucJm,  is  all  but  absent  in  Man,  being 
represented  in  him  by  a  tliin  narrow  band — or  rather 
two  thin  planes  of  fibres,  the  ligamenta  suhflava.  It 
is  described  by  Leyh  as  if  there  were  not  two  portions, 
and  that  excellent  anatomist  does  not  appear  to  insist 
suificiently  on  the  difference  between  the  dorso-nuchal 
and  the  dorso-lumbar  divisions.  Percivall,  who  almost 
entirely  neglects  the  ligaments,  also  makes  no  distinc- 
tion. The  difference  in  structure,  elasticity,  and 
situation,  wairants  the  distinction  made  by  Chauveau. 
As  already  indicated,  the  function  of  this  ligament — 
and  more  particularly  of  its  nuchal  division — is  to 
maintain  the  head  and  neck  in  their  natural  position 
during  repose,  and  to  allow  the  most  extensive  move- 
ments at  other  times.) 

c.  Interspinous  Ugaments  (Fig.  121,  3). — Fibrous 
laminae  fill  the  interspinous  spaces,  and  are  attached, 
before  and  behind,  to  the  opposite  borders  of  the  spinous 
processes,  which  they  unite.  They  are  confounded 
superiorly  with  the  supra-spinous  hgament,  and  are  continued  inferiorly  by  the 
interlamellar  ligaments — forming  two  lateral  planes  which  are  applied  against  each 
other,  hke  the  laminae  of  the  cervical  ligament,  and  covered  outwardly  by  the  inter- 
transversalis colli  muscles. 

In  the  region  of  the  neck,  the  interspinous  ligaments  are  yellow  and  elastic. 
In  the  dorso-lumbar  region,  they  are  formed  by  fasciculi  of  white  fibrous  tissue, 
loosely  united  to  each  other  at  their  extremities,  and  directed  very  obliquely 
backwards  and  downwards.  In  consequence  of  this  disposition,  and  notwith- 
standing their  inextensibility,  they  permit  the  separation  of  the  spinous  processes. 
Their  lateral  surfaces  are  divided  by  a  layer  of  grey  elastic  fibres,  which  cross  hke 
an  X  the  direction  of  the  preceding  fasciculi.  Very  abundant  in  the  anterior 
moiety  of  the  dorsal  region,  these  fibres  operate,  by  their  proper  elasticity,  in 
bringing  the  spinous  processes  towards  each  other. 

d.  Interlamellar,  or  interannular  ligaments. — Situated,  as  their  name  indicates, 
between  the  vertebral  laminae,  and  divided  into  two   lateral  moieties,  these 


INTERVERTEBRAL    ARTICULA- 
TIONS. 

A,  B,  C,  Bodies  of  three  dorsal 
■vertebrse  divided  longitudi- 
nally ami  vertically  to  show 
(1,  i)  a  section  of  the  inter- 
vertebral discs ;  2,  supra- 
spinous dorso-lumbar  liga- 
ment ;  3,  interspinous  liga- 
ment ;  4,  fibrous  fascia,  con- 
stituting the  proper  capsule 
of  the  articular  processes  in 
the  dorsal  region. 


ARTICULATIONS  OF  THE  SFINE.  183 

ligaments  appear  to  be  produced  by  the  two  fibrous  planes  of  the  preceding 
ligaments,  which,  on  arriving  at  the  base  of  the  spinous  processes,  separate  from 
one  another  to  be  carried  outwards.  Their  anterior  border  is  inserted  into  the 
posterior  margin  of  the  vertebral  lamina  in  front.  Their  posterior  border  is  fixed 
to  the  anterior  border  and  inferior  face  of  the  lamina  behind.  Their  superior 
face  is  in  relation  with  some  spinal  muscles,  and  their  inferior  face  is  in  contact 
with  the  dura  mater.  Outwardly,  they  are  confounded  with  the  capsules  proper 
to  the  articular  processes.  Yellow  and  elastic  in  the  cervical  region,  these 
ligaments  are  Avhite  and  inelastic  in  the  dorso-lumbar  region. 

Ohaeactees  proper  to  some  Intervertebral  Articulations.  1.  Inter- 
coccygeal  ana  sacro-coccijgeal  articulations. — These  articulations  are  adapted  to  the 
rudimentary  type  of  the  vertebrae  they  unite.  The  coccygeal  bones  only  come  in 
contact  by  their  bodies — their  spinal  laminse  being  reduced  to  the  merest  traces, 
or  are  altogether  absent.  The  anterior  and  posterior  articular  surfaces  of  each 
vertebra  are  convex,  and  the  interarticular  fibro-cartilages,  hollow  on  both  faces, 
resemble  a  biconcave  lens.  With  regard  to  the  peripheral  bands,  they  are  repre- 
sented by  a  bundle  of  longitudinal  fibres  spread  over  the  surface  of  the  bones, 
which  they  envelop  in  a  common  sheath. 

2.  Intersacral  articulations. — The  sacral  vertebras  being  fused  into  one  piece 
— the  OS  sacrum — there  is  no  occasion  to  study  the  true  articulations  in  this 
region.  It  may  be  remarked,  however,  that  the  supra-spinous  dorso-lumbar  liga- 
ment is  continued  on  the  sacral  spine,  and  that  there  exist  between  the  processes 
formed  by  this  spine,  true  interspinous  ligaments. 

3.  Sacro-lumhar  articulation. — In  this  articulation,  the  great  thickness  of  the 
fibro-cartilage  is  to  be  remarked  ;  and,  in  addition,  that  the  last  lumbar  vertebra 
corresponds  with  the  sacrum  not  only  by  its  body  and  articular  processes,  but 
also  by  the  oval  and  slightly  concave  facets  shown  on  the  posterior  border  of  its 
transverse  processes,  which  are  adapted  to  analogous  slightly  convex  facets  on  the 
sides  of  the  base  of  the  sacrum.  The  bundles  of  fibres  thrown  from  one  bone  to 
another  from  around  these  sacro-transversals  (real  planiform  diarthroses)  maintain 
the  articular  surfaces  in  contact,  and  cover,  outwardly,  the  synovial  membrane 
which  facilitates  their  gUding. 

4.  Articulation  of  the  tivo  last  lumbar  vertebrce. — This  is  distinguished  by  the 
presence,  between  the  transverse  processes,  of  a  planiform  diarthrosis,  like  that  of 
the  sacro-transversal  just  noticed.  These  two  articulations  are  only  found  in 
Solipeds. 

5.  Atlo-axoid  articulation. — This  is  so  far  removed  by  its  conformation  and 
special  uses  from  the  other  intervertebral  articulations,  that  it  will  be  described 
as  an  extrinsic  articulation  of  the  head  and  spine.    (See  Articulations  of  the  Head.) 

The  Movements  of  the  Spine  in  general. — Each  intervertebral  articula- 
tion is  the  seat  of  very  obscure  movements,  the  separate  study  of  which  offers 
little  interest.  But  these  movements,  when  conjoined  with  those  of  the  other 
articulations,  result  in  bending  the  whole  spine  in  a  somewhat  marked  manner, 
and  producing  either  the  flexion,  extension,  or  lateral  inclination  of  this  flexuous 
column. 

When  flexion  takes  place,  the  spine  is  arched  upwards,  the  common  inferior 
ligament  is  relaxed,  the  spinous  processes  separate  from  one  another,  and  the 
supra-spinous  ligament,  becoming  very  tense,  soon  imposes  limits  to  this  movement. 

Extension  is  effected  by  an  inverse  mechanism,  and  is  checked  by  the  tension 
of  the  common  inferior  ligament  and  the  meeting  of  the  spinous  processes. 


181 


THE  ARTICULATIONS. 


Lateral  inclination  takes  place  when  the  spine  bends  to  one  side.  This 
movement  is  very  easily  executed  in  the  cervical  and  coccygeal  regions,  but  is 
arrested  by  the  ribs  and  the  costiform  processes  in  the  dorso-lumbar  region. 

A  circumflex  movement  is  possible  at  the  two  extremities  of  the  vertebral 
column— neck  and  tail ;  for  they  pass  easily  from  extension  to  lateral  inclination, 
and  from  tliis  to  flexion,  etc. 

Owing  to  the  elasticity  of  the  intervertebral  fibro-cartilages,  the  spine  is 
endowed  with  a  very  limited  amount  of  rotation,  or  rather  of  torsion. 

For  the  special  study  of  the  movements  of  each  spinal  region,  reference  must 
be  made  to  what  has  been  already  said  (,p.  U)  regarding  tlie  mobility  of  this 
part. 

Fig.  122. 


CERVICAL   LIGAMENT   OF   THE   OX. 

L,  l',  The  two  laminse  which  form  the  cord  of  the  cervical  ligament :  1,  2,  3,  4,  the  four  anterior 
digitations  of  the  cordiform  portion.  R,  Its  accessory  portion  :  5,  first  dorsal  vertebrae ;  6,  6,  6, 
interspinous  ligament  of  the  dorsal  region. 


Differential  Characters  in  the  Vertebral  Articulations  and  Ligaments  in  the 

OTHER  Animals. 
A.  In  the  Ox  the  intervertebral  discs  are  much  thicker  than  in  the  Horse.  The  common 
inferior  vertebral  ligament  is  very  strong  in  the  lumbar  region.  The  supraspinous  dorso-lumhar 
ligamsnt  is  composed  of  yellow  elastic  tissue.  The  cervical  ligament  is  much  more  developed 
than  in  Solipeds,in  consequence  of  the  greater  weight  of  the  head ;  and  it  presents  a  conforma- 
tion altogether  special,  which  M.  Lecoq  has  made  known  in  the  following  terms :  "  On  lenving 
the  withers,  the  stipra- spinous  ligament  ceases  to  cover  the  head  of  the  spinous  processes,  and 
extends  from  each  side  in  a  wide  and  strong  band,  taking  points  of  attachment  on  the  sides  of 
the  processes,  and  becoming  separated,  on  leaving  that  of  the  first  dorsal  vertebra,  into  two 
parts — a  superior  and  inferior.  The  first  reaches  the  cervical  tuberosity  in  the  form  of  a  thick 
cord  united  to  the  cord  of  the  opposite;  the  other  thins  off  into  a  band,  which  is  attached  to 
the  posterior  half  of  the  spinous  process  of  the  axis,  and  to  that  of  the  third  and  fourth  vertebrae. 
A  production  of  the  same  kind — an  auxiliary  to  the  principal  portion — leaves  the  anterior  border 
of  the  spinous  process  of  the  first  dorsal  vertebra,  and  is  attached  to  that  of  the  fourth,  fifth, 


ARTICULATIONS  OF  THE  SPINE. 


185 


sixth,  and  seventh  vertebrae.  The  superior  border  of  this  auxiliary  ligamentous  production,  is 
concealed  between  the  two  lamiua  of  the  principal  ligament."  ' 

B.  Camel. — In  this  animal,  the  common  supraspinous  ligament  is  entirely  composed  of 
yellow  elastic  tissue ;  it  is  therefore  impossible  to  distinguish,  physically,  a  dorso-lumbar  and  a 
cervical  portion.  It  is  remarkable  for  its  thickness  and  width ;  and  its  dimensions  increase 
from  behind  to  before,  especially  from  the  second  lumbar  vertebra.  At  the  fifth,  sixth,  seventh, 
eighth,  ninth,  and  tenth  dorsal  vertebrae  an  elastic  band  is  given  off  fi  om  its  borders ;  as  this 
descends,  it  gradually  becomes  thinner  until  it  reaches  the  external  intercostal  muscles. 

From  the  ninth  dorsal  vertebra,  the  supraspinous  ligament  divides  into  two  layers,  which 
are  placed  against  the  lateral  faces  of  the  spinous  processes.     In  the  cervical  region,  the  layers 


Fig.  123, 


kt^i^l^^-^ 


^i 


x\\\-^ 


CERVICAL   LIGAMENT   OF   A    YOUNG   CAMEL. 


become  rounded,  are  joined  to  each  other  by  means  of  connective  tissue,  and  describing  an  S- 
shaped  curve,  become  inserted  into  the  occipital  bone. 

They  give  oflf,  from  their  inferior  border,  six  digitations,  which  are  attached  to  the  spinous 
processes  of  tlie  last  six  cervical  vertebrae.  An  accessory  leaf  is  situated  between  the  two 
portions  just  described :  it  is  detached  from  the  anterior  border  of  the  spinous  process  of  the 
first  dorsal  vertebra,  and  is  fixed  anteriorly  into  the  two  last  cervical  vertebrae. 

C.  Pig. — The  Pig,  remarkable  for  the  shortness  of  its  neck  and  the  limited  movements  of 
this  region,  does  not  show  any  cervical  ligament,  properly  so  called.  It  is  replaced  by  a  super- 
ficial fibrous  raphe',  extending  from  the  occipital  bone  to  tlie  spinous  process  of  the  first  dorsal 
vertebra. 


^Journal  de  MMecine  VeW-inaire,  p.  122.     Lyons,  1848. 


186  TEE  ARTICULATIONS. 

D.  Camivora. — The  Cat  has  no  cervical  ligament,  and  shows,  instead,  a  raphe  like  the 
Pig.  In  the  Dog,  the  ligament  is  reduced  to  a  simple  cord,  continued  from  the  dorso-lumbar 
ligament,  and  goes  no  further  than  behind  the  spinous  process  of  the  axis.  In  the  Cat,  the 
interspinous  ligaments  are  replaced  by  small  muscular  fasciculi ;  in  the  Dog,  this  substitution 
only  takes  place  in  the  xiervical  region.  The  laminae  of  the  first  coccygeal  vertebrae  possess 
the  principal  characters  which  distinguish  perfect  vertebrae,  and  are  united  by  vestiges  of  the 
articular  bands  which  exist  in  the  other  regions  of  the  spine. 

Aeticle  IL — Articulations  of  the  Head. 

We  will  first  study  the  two  extrinsic  articulations  which  are  the  centre  of  the 
movements  of  the  head  on  the  spine — the  atlo-axoid  and  occipito-athid  articula- 
tions. Afterwards,  we  will  pass  to  the  examination  of  the  joints  which  unite  the 
different  bones  of  the  head. 

1.  Atlo-axoid  Articulation  (Fig.  124). 

Preparation. — It  suffices  to  remove  the  soft  parts  from  around  the  articulation,  to  expose 
the  interannular,  the  interspinous,  and  the  inferior  odontoid  ligament.  To  examine  the  superior 
odontoid  ligament  and  the  synovial  membrane,  one  half  the  atlas  and  axis  must  be  separated 
by  sawing  longitudinally  through  them  from  oue  side  to  the  other. 

This  may  be  considered  as  the  type  of  the  trochoid  articulation. 

Articular  surfaces. — To  form  this  articulation,  the  axis  offers  its  odontoid 
pivot  and  the  undulated  diarthrodial  facets  at  its  base.  The  atlas  opposes  to  the 
pivot  the  concave  semi-cylindrical  surface  hollowed  on  the  superior  face  of  its 
body  ;  and  for  the  lateral  undulated  facets  it  has  analogous  facets  cut  on  the 
transverse  processes,  on  each  side  of  the  vertebral  canal. 

Mode  of  union. — 1.  An  odontoid,  or  odonto-atloid  ligament.  2.  An  inferior 
atlo-axoid  ligament.     3.  A  superior  ditto.     4.  A  fibrous  capsule. 

a.  Odontoid  ligament  (Fig.  124,  3). — Continuous  with  the  common  superior 
vertebral  ligament,  very  short  and  strong,  flattened  above  and  below,  and  triangu- 
lar in  shape,  the  odontoid  ligament  is  composed  of  glistening  white  fibres,  fixed 
behind  in  the  superior  channel  of  the  odontoid  process,  and  inserted  in  front  on 
the  transverse  ridge  which  separates  the  superior  face  from  the  inferior  arch  of 
the  atlas,  as  well  as  on  the  imprints  situated  in  front  of  this  ridge.  It  is  covered, 
on  its  lower  face,  by  the  synovial  membrane  of  the  articulation ;  and  its  upper 
surface  is  in  contact  with  the  spinal  dura  mater.  It  sends  some  bands  within  the 
condyles  of  the  occipital  bone. 

b.  Inferior  atlo-axoid  ligament. — This  is  a  wide,  thin,  and  nacrous-looking 
band,  extending  from  the  inferior  face  of  the  axis  to  the  inferior  tubercle  of  the 
atlas,  and  is  covered  by  the  longus  colli  muscle  ;  it  is  united  to  the  synovial  mem- 
brane by  its  deep  face,  and  confounded  on  its  bordei-s  with  the  fibrous  capsule  to 
be  immediately  described.     It  represents  the  common  inferior  vertebral  ligament. 

c.  Superior  atlo-axoid  ligament. — This  exactly  represents  the  interspinous  liga- 
ments of  the  other  cervical  articulations.  Yellow,  elastic,  and  formed  like  the 
two  lateral  bands,  it  is  continuous,  laterally,  with  the  capsular  Ugament.  It 
represents  the  interspinous  and  interlamellar  ligaments. 

d.  Capsular  ligament. — This,  it  may  be  said,  is  only  the  interlamellar  ligament 
proper  to  the  atlo-axoid  articulation.  It  commences  from  the  sides  of  the  pre- 
ceding ligament,  and  becomes  united  to  the  inferior  atlo-axoid,  after  contracting 
adhesions  with  the  borders  of  the  odontoid  Ugament.  In  this  way  it  encloses  the 
articulation  and  the  spinal  canal.  Before  and  beliind,  it  is  attached  to  the  anterior 
or  posterior  margin  of  the  bones  it  unites.     Its  external  face  is  in  contact  wiih 


ARTICULATIONS   OF  THE  HEAD. 


187 


the  great  oblique  muscle  of  the  head  ;  its  internal  responds,  in  its  inferior  half, 
to  the  articular  synovial  membrane,  and  its  superior  moiety  to  the  spinal  dura 
mater.     It  is  analogous  to  the  capsules  in  other  regions. 
(Leyh  describes  this  Ugament  as  the  interannular).  Fig.  124. 

Synovial  membrane. — This  lines  the  odontoid  ligament 
and  atlo-axoid  ligaments,  and  the  articular  portion  of  the 
peripheral  capsule. 

Movements. — Rotation,  the  only  movement  possible  in 
the  atlo-axoid  articulation,  is  effected  in  the  following 
manner  :  the  axis  remains  fixed,  and  the  first  vertebra, 
drawn  to  one  side  chiefly  by  the  great  oblique  muscle, 
rotates  on  the  odontoid  pivot,  carrying  the  head  with  it. 

The  rotation  movements  of  the  head  have,  therefore, 
this  diarthrosis  for  a  centre,  and  not  the  atloido-occipital 
articulation. 

In  the  Dog  and  Cat,  the  odontoid  ligament  is  replaced  by  three 
particular  ligaments :  1.  Two  lateral  cords,  rising  in  common  from  the 
summit  of  the  odontoid  process,  and  inserted,  each  on  its  own  side, 
within  the  condyles  of  tlie  occipital  bone.  2  A  transverse  ligament, 
passing  over  the  odontoid  process,  which  it  maintains  in  its  place 
against  the  itiferior  arch  of  the  atlas,  and  is  attached  by  its  extremities 
to  the  superior  face  of  the  latter.  A  small  synovial  capsule  facili- 
tates the  gliding  of  the  odontoid  process  beneath  this  ligament.  The 
articular  synovial  membrane  always  communicates  with  that  of  the 
occipito-atloid  articulation. 

In  the  Pig,  the  disposition  is  nearly  the  same  as  in  the  Caruivora. 


2.  Occipito-atloid  Articulation  (Fig.  124). 

(^Preparation. — Dissect  away  all  the  soft  parts  that  pass  from  the 
neck  to  the  head  and  cover  the  articulation,  and  more  particularly 
the  flexor,  the  recti,  and  the  small  oblique  muscles  of  the  head.  To 
expose  the  synovial  membranes,  open  the  sides  of  the  capsular 
ligament.) 


This  is  a  condyloid  articulation. 

Articular  surfaces. — In  the  atlas,  the  two  cavities  which 
replace  the  anterior  articular  processes  and  the  heads  of  the 
other  vertebrfe  ;  in  the  occipital  bone,  the  two  condyles 
flanking  the  sides  of  the  occipital  foramen. 

Mode  of  union. — A  single  capsular  ligament  envelops 
the  entire  articulation  ;  it  is  attached  by  its  anterior  border 
to  the  margin  of  the  occipital  condyles,  and  by  its  posterior 
to  the  anterior  contour  of  the  atlas.  Thin  and  slightly 
elastic  in  its  inferior  half,  this  ligament  presents,  supe- 
riorly, four  reinforcing  fasciculi :  two  middle,  which  inter- 
cross in  X — whence  the  name  "cruciform,"  sometimes 
given  to  this  ligament  (Fig.  124,  1,  1)  ;  and  two  lateral, 
which  pass  from  the  sides  of  the  atlas  to  the  base  of 
the  styloid  processes  (Fig.  124,  2,  2).  It  is  lined  by 
the  synovial  membranes,  and  is  enveloped  externally  by  a 

large  number  of  muscles,  which  protect  the  articulation  and  greatly  strengthen 
it  everywhere.     Among  these  may  be  particularly  noticed  the  recti  muscles  of 


ATLO-OXOID  AND  OCCIPI- 
TO-ATLOID ARTICULA- 
TIONS (the  upper  arch 
of  the  atlas  has  been 
removed  to  show  the 
odontoid  ligament). 

1, 1,  Middle  accessory  fas- 
ciculi ;  2,  2,  lateral 
fasciculi  of  the  capsular 
ligament  of  the  occipi- 
to-atloid articulation  ; 

3,  odontoid  ligament ; 

4,  interspinous  liga- 
ment uniting  the  second 
and  third  vertebrae  of 
the  neck ;  5,  fibrous 
capsule  uniting  the 
articular  processes  of 
these  vertebrae.  A, 
Anterior  internal  fora- 
men of  the  atlas  con- 
verted into  a  groove  by 
the  section  of  the  bone; 
B,  B,  vertebral  foramina 
of  the  atlas  ;  C,  C,  fora- 
mina replacing  the  an- 
terior notches  of  the 
axis. 


188 


THE  ARTICULATIONS. 


the  head,  the  small  oblique,  and  the  complexus.  There  is  also  the  cord  of  the 
cervical  ligament, 

Sijiiovial  membranes. — These  membranes  are  two  in  number — one  for  each 
condyle  and  coiTesponding  atloid  cavity.  Sustained  above,  below,  and  outwardly 
by  the  capsular  ligament,  they  are  related  inwardly  to  the  dura  mater  and  the 
fibrous  tractus  which,  from  the  odontoid  ligament,  is  carried  to  the  internal  face 
of  the  occipital  condyles. 

Movements. — Extension,  flexion,  lateral  inclination,  and  circumduction,  are  the 
movements  of  the  occipito-atloid  articulation. 


In  the  Pig,  Dog,  and  Cat,  this  articulation— strengthened,  as  it  is,  by  the  capsular  and 
odontoido-occipital  ligaments  already  mentioned — has  only  one  synovial  capsule. 

3.  Aeticulation  of  the  Bones  of  the  Head  with  each  other. 
If  we  except  the  articulation  which  unites  the  inferior  jaw  to  the  cranium — 
the  temporo-maxillary — and  the  hyoideal  articulations,  it  will  be  found  that  all 
the  bones  of  the  cranium  and  face  are  united  to  each  other  by  synarthrosis, 
forming  the  different  kinds  of  sutures  already  generally  described  (p.  170). 
Nothing  is  to  be  gained  by  entering  into  more  detail  with  regard  to  these  articu- 
lations, as  it  will  be  found  sufficient  to  call  to  mind  the  topographical  description 
of  each  bone  entering  into  their  formation. 

4.  Temporo-maxillary  Articulation  (Fig.  125). 

{Preparation. — Remove  the  masseter  muscle  and  the  parotid  gland.  Saw  through  the 
head  about  the  middle  liue.  Open  the  articulation  externally,  to  exhibit  the  interarticular 
meniscus.) 

The  lower  jaw,  in  its  union  with  the  cranium,  constitutes  a  double  condyloid 
articulation. 
F'g  125.  Articular  surfaces. — With   the   temporal    bone, 

these  are  the  condyle,  the  glenoid  cavity,  and  the 
supra-condyloid  process  at  the  base  of  the  zygomatic 
process.  The  glenoid  cavity  is  not  lined  by  cartilage, 
and  appears  to  be  merely  covered  by  synovial  mem- 
brane. On  the  maxillary  bone  is  the  oljlong  condyle 
situated  in  front  of  the  coronoid  process. 

Interarticular  fihro-cartilage. — The  articular  sur- 
faces just  named  are  far  from  fitting  each  other 
accurately  ;  this  is  only  accompUshed  by  the  inter- 
position of  a  fibro-cartilaginous  disc  between  the 
temporal  and  maxillary  bones.  This  disc  is  a  kind 
of  irregular  plate,  flattened  above  and  below,  thicker 
before  than  behind,  and  moulded  on  each  of  the 
diarthrodial  surfaces  it  separates.  Its  superior  face, 
therefore,  presents  :  in  front,  a  cavity  to  receive 
the  condyle  of  the  temporal  bone  ;  behind,  a  boss 
which  is  lodged  in  the  glenoid  cavity.  The  inferior 
face  is  hollowed  by  an  oblong  fossa,  in  which  the 
maxillary  condyle  is  lodged  (Fig.  125,  1). 

Mode  of  union. — A  fibrous  envelope — a  true  capsular  ligament — surrounds  the 
articulation,  aiid  is  attached  by  its  borders  to  the  margin  of  the  articular  surfaces 
it  unites.     Formed,  outwardly,  by  a  thick  fasciculus  of  white  vertical  fibres  (Fig, 


TEMPORO-MAXILLARY   ARTICU- 
LATION . 

1,  Interarticular  fibro-cartilag;e  ; 
2,  external  fasciculus  of  the 
capsular  ligament.  A,  Base  of 
the  coronoid  process ;  B,  neck 
of  the  maxillary  condyle;  C, 
mastoid  process ;  D,  external 
auditory  hiatus. 


ARTICULATIONS  OF  THE  HEAD.  189 

125,  2),  this  ligament  becomes  greyish-coloured  and  elastic  for  the  remainder  of 
its  extent,  and  greatly  diminishes  in  thickness,  especially  in  front.  Its  inner 
face  IS  covered  by  the  synovial  capsules,  and  adheres  to  the  circumference  of  the 
interarticular  fibro-cartilage.  Its  external  face  is  related,  in  front,  to  the  temporal 
and  masseter  muscles  ;  behind,  to  the  parotid  gland  ;  inwardly,  to  the  external 
pterygoid  muscle  ;  and  outwardly,  to  a  fibrous  expansion  which  separates  it  from 
the  skin.  (Leyh  mentions  a  lateral  external  and  a  posterior  ligament  for  this 
articulation,  but  Chauveau  and  Bigot  evidently  look  upon  these  as  portions  of 
the  capsular.) 

Synovial  membranes. — This  articulation  has  two  synovial  sacs — one  above  the 
other — which  are  separated  by  the  fibro-cartiiaginous  disc. 

Movements. — The  temporo-maxillary  articulation  is  the  centre  of  all  the 
movements  performed  by  the  lower  jaw.  These  are  :  depression,  elevation,  lateral 
motion,  and  horizontal  gliding. 

The  lower  jaw  is  depressed  when  it  separates  from  the  superior  one,  and  is 
elevated  when  it  approaches  this.  These  two  opposite  movements  are  executed  by 
a  mechanism  of  such  great  simplicity,  that  it  need  not  be  described  here.  Lateral 
movements  take  place  when  the  inferior  extremity  of  the  jaw  is  carried  alternately 
to  the  right  and  left.  It  then  happens  that  one  of  the  maxillary  condyles,  taking 
with  it  the  fibro-cartilage,  is  brought  into  contact  with  the  temporal  condyle, 
while  the  other  is  embedded  in  tiie  glenoid  cavity  of  the  opposite  side.  The 
horizontal  gliding  is  effected  from  behind  to  before,  or  vice  veisd.  In  the  first 
case,  the  two  maxillary  condyles  are  carried  at  the  same  time  under  the  temporal 
condyles,  bearing  with  them  the  fibro-cartilages.  In  the  second  case,  they  are 
drawn  into  the  glenoid  cavities,  and  rest  against  the  supra-condyloid  eminence, 
which  prevents  their  going  further.  It  will  be  understood,  after  this  brief 
description,  that  the  presence  of  the  fibro-cartilages  singularly  favours  the  lateral 
movements  and  horizontal  gliding  of  the  lower  jaw. 

In  the  Pig,  the  temporo-maxillary  articulation  is  formed  after  the  same  type  as  that  of 
Rodents,  and  allows  very  extensive  movements  from  before  to  behind — a  circumstance  due  to 
the  complete  absence  of  the  supra-condyloid  eminence. 

In  the  Dog  and  Cat,  the  maxillary  condyle  is  exactly  fitted  to  the  temporal  cavity.  This 
disposition,  in  giving  great  precision  to  the  movements  of  depression  and  elevation,  restrains  in 
a  singular  manner  the  lateral  and  horizontal  gliding  motions.  The  interarticular  fibro-cartilage 
is  extremely  thin  in  these  animals. 

In  the  Rabbit,  the  narrow  condyle  of  the  maxilla  moves  from  before  to  behind  and  to 
each  side,  on  the  temporal  bone,  the  articular  surface  of  which  is  very  elongated  and  destitute 
of  a  subglenoid  eminence. 

5.  Hyoideal  Aeticulations. 

(Preparation. — Disarticulate  the  lower  jaw,  and  dissect  away  from  the  right  of  each 
articulation  the  muscles  that  may  conceal  the  view.) 

These  are  of  two  kinds — extrinsic  and  intrinsic.  The  first  comprise  the  two 
tempo ro-hyoideal  articulations  ;  to  the  second  belong  the  joints  which  unite  the 
different  pieces  of  the  hyoid  bone — the  interhyoideal  articulations. 

Temporo-hyoideal  Articulations. — These  are  two  amphiarthrodial  joints, 
in  the  formation  of  which  each  great  cornu  of  the  hyoid  bone  opposes  its  upper 
extremity  to  the  hyoideal  prolongation  lodged  in  the  vaginal  sheath  of  the 
temporal  bone.  An  elastic  cartilage,  from  -^q  to  i%-  of  an  inch  in  length,  unites 
the  two  bones  in  a  solid  manner  ;  and  it  is  owing  to  the  flexibility  of  this 
cartilage  that  the  hyoid  bone  can  move  entirely  on  the  temporal  bones. 
15 


190  THE  ARTICULATIONS. 

Inter-hyoideal  Articulations. — A.  The  great  cornu  articulates  with  the 
small  one,  by  an  amphiarthrosis  analogous  to  the  preceding.  To  form  this  articu- 
lation, these  two  pieces  of  bone  are  joined  at  an  acute  angle,  through  the  medium 
of  a  more  or  less  thick  cartilaginous  band,  in  the  centre  of  which  there  is  often 
a  little  bony  nucleus— the  styloid  nucleus,  or  kerato-hyal  bone.  This  cartilage  is 
elastic  and  flexible,  and  permits  the  opening  and  closing  of  the  articular  angle  at 
the  summit  of  which  it  is  placed. 

B.  Each  styloid  cornu  is  united  to  the  body  of  the  hyoid  bone,  or  basihyal, 
by  an  arthrodial  articulation.  The  articular  surfaces  are  :  for  the  hyoideal 
branch,  the  small  cavity  terminating  its  inferior  extremity  ;  for  the  body,  the 
convex  lateral  facet  situated  at  the  origin  of  the  thyroid  cornua.  These  surfaces 
are  covered  by  cartilage,  and  enveloped  by  a  small  synovial  sac  and  a  peripheral 
fibrous  capsule.  They  can  ghde  on  each  other  in  nearly  every  direction.  (Median 
and  superior  hyoideal  capsular  ligaments  are  described  by  Leyh  as  sometimes 
present.  The  latter  unites  the  upper  and  middle  branches,  and  the  former  the 
middle  with  the  inferior  branches.  They  are  absent  when  these  branches  are 
confounded  with  the  superior  ones.) 

Article  III. —Articulations  of  the  Thorax. 

These  are  also  divided  into  extrinsic  and  intrinsic.  The  first — named  costo- 
vertebral—unite  the  ribs  to  the  spine.  The  second  join  the  different  bones  of  the 
thorax  together ;  they  comprise  :  1.  The  chondro-sternal  articulations,  2. 
Chondro-costal  articulations.  3.  The  articulations  of  the  costal  cartilages  with 
each  other.  4.  The  sternal  articulation  perculiar  to  the  larger  Ruminants  and 
the  Pig.  All  these  joints  will  be  first  studied  in  a  special  manner,  then  examined 
in  a  general  way  as  to  their  movements. 

Extrinsic  Articulations. 

Articulations  of  the  Ribs  with   the  Vertebral  Column,  or  Costo- 
vertebral Articulations. 

(Preparation.— This  is  simple.  No  difficulty  need  be  experienced  except  in  exposing  the 
interartieular  ligament,  and  this  is  efifected  by  sawing  tlirough  one  of  the  dorsal  vertebra 
transversely,  close  to  the  posterior  intervertebral  joint  formed  by  that  bone.  A  few  cuts  of  the 
bone  forceps  will  then  show  the  whole  extent  of  the  ligament.) 

Each  rib  articulates  with  the  vertebral  column  by  two  points — its  head  and 
its  tuberosity.  The  first  is  received  into  one  of  the  intervertebral  cavities 
hollowed  out  on  the  sides  of  the  spine,  and  is  therefore  in  contact  with  two  doi-sal 
vertebrfe  ;  the  second  rests  against  the  transverse  process  of  the  posterior  vertebra. 
From  this  an'angement  arises  two  particular  articulations  belonging  to  the 
arthrodial  class,  which  are  named  costo-vertehral  and  costo-transverse. 

Costo-vertebral  Articulations. — Articular  surfaces. — Pertaining  to  the 
rib,  we  have  the  two  convex  facets  of  the  head,  separated  from  each  other  by  a 
groove  of  insertion,  and  covered  by  a  thin  layer  of  cartilage.  On  the  vertebras, 
the  concave  facets  which,  by  their  union,  form  the  intervertebral  cavity ;  these 
facets  are  also  covered  with  cartilage,  and  separated,  at  the  bottom  of  the  cavity, 
by  the  con'esponding  intervertebral  disc. 

Mode  of  union. — 1.  An  interartieular  ligament  (Figs.  126,  2  ;  127,  1),  fixed 
in  the  groove  in  the  head  of  the  rib,  and  attached  to  the  superior  border  of  the 


ARTICULATIONS  OF  THE  THORAX. 


191 


intervertebral  disc,  Avhich  it  encii-cles  upwards  and  inwards,  to  unite  on  the  median 
line  with  the  ligament  of  the  opposite  side.  2.  An  inferior  peripheral  ligament 
(Fig.  127,  2,  3,  4),  flat  above  and  below,  thin  and  radiating  (whence  it  is  often 
named  the  stellate  ligament),  formed  of  three  fasciculi,  wliich  are  fixed  in  common 
on  the  inferior  face  of  the  head  of  the  rib,  and  in  diverging  are  carried  over  the 
bodies  of  the  two  vertebrte  and  the  intervertebral  disc.  Lmed  above  by  the 
synovial  membranes,  this  ligament  is  covered  below  by  the  pleura.  (Leyh  includes 
a  capsular  ligament  for  the  head  of  the  rib,  and  another  for  the  costal  tuberosity. 
He  probably  considered  the  synovial  membrane  of  these  articulations  as  such.) 

Synovial  membranes. — These  are  two  in  number — an  anterior  and  posterior, 
lying  against  each  other,  and  separated  in  part  by  the  interarticular  ligament 
they  cover.  Supported  below  by  the  stellate  ligament,  above  they  are  directly  in 
contact  with  the  levatores  costarum  muscles,  and  with  vessels  and  nerves. 

CosTO-TRANSVERSE   ARTICULATIONS.     Avticular  surfttces. — In  the  rib,  the 


Fig.  127. 


Fig.  126. 


articulations  of  the  ribs  with  the  ver- 
tebra, and  of  these  with  each  other 
(upper  plane). 

1,  Spinal  canal,  upper  face,  showing  the  common 
superior  ligament;  2,  interarticular  costo- 
vertebral ligament ;  3,  interosseous  costo- 
transverse ligament ;  4,  posterior  costo-trans- 
verse  ligament. 


ARTICULATIONS  OF  THE  RIBS  WITH  THE 
VERTEBRA,  AND  OF  THESE  WITH  EACH 
OTHER   (INFERIOR   PLANE). 

1,  Interarticular  costo-vertebral  liga- 
ment ;  2,  3,  4,  fasciculi  of  the  stellate, 
or  inferior  costo-vertebral  ligament;  5, 
common  inferior  vertebral  ligament. 


diarthrodial  facet  cut  on  the  tuberosity.  In  the  vertebra,  the  analogous  facet  on 
the  outside  of  the  transveree  process. 

Mode  of  union.  Two  ligaments  bind  this  articulation  :  1.  The  posterior  costo- 
transverse ligament  (Fig.  126,  4),  a  white  fibrous  band  attached  by  its  extremities 
behind  the  transverse  process  and  the  costal  tuberosity,  lined  by  synovial  mem- 
brane, and  covered  by  the  transverse  insertions  of  several  spinal  muscles.  2.  The 
anterior  costo-transverse.,  or  interosseous  ligament  (Fig.  126,  3),  a  fasciculus  of 
short,  thick,  white  fibres,  fixed  on  the  anterior  surface  of  the  transverse  process 
near  its  base,  and  in  the  rugged  excavation  on  the  neck  of  the  rib.  This  liga- 
ment is  invested,  posteriorly,  by  the  synovial  membrane,  and  covered  in  front  by 
pads  of  adipose  tissue  which  separate  it  from  the  costo-vertebral  articulation. 

Synovial  membrane. — This  is  a  small  particular  capsule,  kept  apart  from  the 
posterior  synovial  membrane  of  the  costo-vertebral  articulation  by  the  costo-trans- 
verse interosseous  ligament. 

Characters  peculiar  to  some  Costo-vertebral  Articulations. — 1. 
The  first,  and  sometimes  the  second,  costo-vertebral  articulation  has  no  inter- 
osseous ligament,  and  only  exhibits  one  synovial  membrane.     The  intervertebral 


192  THE  ARTICULATIONS. 

cavity  which  concurs  in  forming  the  first  is  often  excavated  between  the  last 
cervical  and  first  dorsal  vertebras. 

2.  The  two  or  three  last  costo-transverse  articulations  are  confounded  with 
the  corresponding  costo-vertebral  joints.  They  have  no  proper  serous  membrane, 
but  the  posterior  synovial  membrane  of  the  latter  is  prolonged  around  their 
articular  surfaces. 

Intrinsic  Articulations. 
A.  The  Chondro-sternal  or  Costo-sternal  Articulations. 

{Preparation. — To  show  the  articulation  of  the  ribs  with  the  cartilages,  these  with  the 
sternum,  and  the  cartilages  with  each  other,  carefully  remove  the  pleura,  the  triangularis 
sterui  muscle,  the  diaphragm,  tlie  transverse  muscle  of  the  abdomen,  then  the  pectorals,  the 
great  oblique,  the  transversalis  of  the  ribs,  and  the  intercostal  muscles.) 

The  first  eight  ribs,  in  resting  upon  the  sternum  by  the  inferior  extremity  of 
their  cartilages,  form  eight  similar  arthrodial  articulations. 

Articular  surfaces. — Each  sternal  cartilage  opposes  to  one  of  the  lateral  cavities 
of  the  sternum,  the  convex  and  oblong  facet  at  its  lower  extremity. 

Mode  of  union. — The  diarthrosis  resulting  from  the  union  of  these  two  surfaces 
is  enveloped  everywhere  by  bundles  of  white,  radiating,  fibrous  tissue,  which  con- 
stitute a  veritable  ligamentous  capsule.  The  superior  part  of  this  capsule — known 
as  the  stellate  or  superior  costo-sternal  ligament,  is  covered  by  the  triangularis 
sterui  muscle  ;  it  is  joined  to  a  fibrous  cord  lying  on  the  superior  face  of  the 
sternum,  and  which  is  confounded  in  front  with  that  of  the  opposite  side.  The 
inferior  portion — the  irtferior  stellate  or  costo-sternal  ligament — is  in  relation 
with  the  pectoral  muscles. 

Synovial  ccqysule. — There  is  one  for  each  articulation. 

Characters  proper  to  the  first  costo-sternal  articulation. — The  first  costo-sternal 
articulation  is  not  separated  from  its  fellow  of  the  opposite  side  ;  so  that  these  two 
joints  are,  in  reality,  only  one,  and  the  two  cartilages  lying  close  to  each  other 
correspond  by  a  small  diarthrodial  facet,  continuous  with  that  for  the  sternum. 
The  two  sternal  facets  are  inclined  upwards,  and  confounded  with  one  another. 
Only  one  synovial  cavity  exists  for  this  complex  articulation,  which  unites  the 
two  first  ribs  to  each  other  and  to  the  sternum. 

B.  Chrondo-costal  Articulations  uniting  the  Ribs  to  their 

Cartilages. 

These  are  synarthrodial  articulations,  the  movements  of  which  are  very 
obscure.  They  are  formed  by  the  implantation  of  the  cartilages  in  the  nigged 
cavities  the  ribs  present  at  their  inferior  extremities.  The  solidity  of  these  articu- 
lations is  assured  by  the  adherence  of  the  fibro-cartilages  to  the  proper  substance 
of  the  ribs,  and  by  the  periosteum  which,  in  passing  from  the  bone  to  the  cartilage, 
plays  the  part  of  a  powerful  peripheral  band. 

In  the  Ox,  the  sternal  ribs,  in  uniting  with  their  oartilages,  form  a  true  ginglymoid  diar- 
throsis, the  movement  of  whicli  is  facilitated  by  a  small  synovial  capsule. 

C.  Articulations  of  the  Costal  Cartilages  with  each  other. 

The  ribs,  attached  to  each  other  by  means  of  the  intercostal  muscles,  are  not 
united  by  real  articulations  ;  neither  are  their  cartilages  of  prolongation.     But 


ARTICULATIONS   OF  THE  THORAX.  ■     193 

the  asternal  cartilages  are  bound  together  by  a  small  yellow  elastic  ligament,  which 
is  carried  from  the  free  extremity  of  each  to  the  posterior  border  of  the  preceding 
cartilage  ;  the  anterior  border  of  the  first  asternal  cartilage  is  directly  united  to 
the  posterior  border  of  the  last  sternal  cartilage,  through  the  medium  of  the 
perichondrium  and  very  short  Kgamentous  bands.  This  same  asternal  cartilage 
is  also  bound  to  the  inferior  face  of  the  xiphoid  appendage  by  a  small  white 
ligament  (the  chondro-xiphoicl),  under  which  passes  the  anterior  abdominal 
artery. 

D.  Sternal  Articulation  peculiar  to  the  Ox  and  Pig. 
It  has  been  already  shown  that  in  these  animals  the  anterior  piece  of  the  sternum  is  not 
consolidated  with  the  second  portion.  Tlie  two  are  united  by  a  diurthrodial  articulation  ;  and 
for  this  purpose  the  anterior  presents  a  concave  surface,  the  posterior  a  convex  one.  Bundles 
of  peripheral  fibres  firmly  bind  tliem  to  each  other,  and  a  special  small  synovial  capsule  facili- 
tates their  movements,  which  are  very  limited. 

The  Articulations  of  the  Thorax  considered  in  a  General  Manner, 
with  Regard  to  Movements. 

The  thorax  can  increase  or  diminish  in  diameter,  in  an  antero-posterior  and 
a  transverse  direction  ;  whence  arise  the  dilatation  and  contraction  of  this  cavity — 
the  inspiratory  movements  accompanying  the  entrance  of  the  external  air  into 
the  lungs,  and  the  expiratory  movements  expelling  the  air  contained  in  these 
organs. 

The  variations  in  the  antero-posterior  diameter  of  the  chest  being  due  to 
changes  in  the  figure  of  the  diaphragm,  need  not  be  noticed  here.  But  the 
transverse  variations  being  the  result  of  the  play  of  the  costal  arches  on  tjie  spine 
and  sternum,  it  is  advantageous  to  study  the  mechanism  which  presides  in  the 
execution  of  theii'  movements. 

The  costal  arches,  being  inclined  backwards  on  the  middle  plane,  the  space 
they  enclose  in  their  concavity  is  not  nearly  so  extensive  as  if  they  were  perpen- 
dicular to  this  plane.  Owing  to  their  double  arthrodial  joints,  the  ribs  are 
movable  on  the  spine  ;  and  their  inferior  extremity,  also  movable,  rests  either 
directly  or  indirectly  on  the  sternum.  Therefore  it  is  that,  when  they  are  drawn 
forward  by  their  middle  portions,  they  pivot  on  theii'  extremities,  and  tend  to 
assume  a  perpendicular  direction,  which  is  the  most  favourable  for  the  largest 
increase  of  the  space  they  limit  ;  then  there  is  enlargement  of  the  lateral  diameter 
of  the  thorax,  which  signifies  dilatation  of  its  cavity.  The  inverse  movement,  by 
an  opposite  mechanism,  causes  contraction  of  the  chest. 

The  ribs  are  said  to  be  elevated  during  the  forward  movement,  and  depressed 
when  they  fall  backwards.  These  expressions,  though  perfectly  applicable  to  Man, 
who  stands  in  a  vertical  position,  are  not  correct  when  employed  in  veterinary 
anatomy. 

Besides  the  enlargement  of  the  thorax  in  the  transverse  and  the  antero-posterior 
directions,  it  is  necessary  to  remark  on  an  increase  in  a  vertical  direction,  caused 
by  the  displacement  of  the  sternum  forward,  due  to  elevation  of  the  ribs.  In  this 
movement,  the  costal  arches  are  erected  not  only  on  the  median  plane,  but  also 
on  the  spine.  The  inferior  extremity,  carried  forward,  also  takes  the  sternum 
with  it  ;  and  this  movement  cannot  take  place  without  that  piece  being  farther 
removed  from  the  vertebrae  above.  In  Man,  the  displacement  of  the  sternum  is 
very  marked. 


194  THE  ARTICULATIONS. 

AeTICLE   IV.---AETICULATIONS   OF   TRE   ANTERIOR   LiMBS. 

1.    SCAPULO-HUMERAL   ARTICULATION  (Fig.  128). 

(Preparation. — Detach  the  limb  from  the  trunk.  Remove  from  the  upper  extremity  those 
muscles  which  are  inserted  in  the  vicinity  of  the  glenoid  cavity  of  the  scapula  ;  turn  down  from 
its  lower  extremity  those  which  are  inserted  into  the  superior  end  of  the  humerus  or  a  little 
below,  preserving  the  attachments  of  their  tendons  with  the  capsular  ligament.  The  seapulo- 
humeralis  gracilis  muscle  may  be  allowed  to  remain,  in  order  to  show  its  relations.) 

To  constitute  this  enarthrodial  articulation,  the  scapula  is  united  to  the 
humerus,  and  forms  an  obtuse  angle  which  is  open  behind. 

Articular  surfaces. — In  the  scapula  there  is  the  glenoid  cavity — the  shallow, 
oval  fossa,  elongated  in  an  antero-posterior  direction,  notched  inwardly,  and 
excavated  at  its  centre,  or  near  the  internal  notch,  by  a  small  synovial  f  ossette.  A 
ligamentous  band,  attached  to  the  brim  of  the  cavity,  fills  up  this  notch,  and  is 
the  vestige  of  the  glenoid  ligament  of  Man.  In  the  humerus,  the  articular  head, 
fixed  between  the  large  and  small  tuberosities,  is  often  excavated  by  a  shallow 
synovial  f ossette. 

Mode  of  union. — One  capsular  ligament  (Fig.  128, 1),  a  kind  of  sac  having  two 
openings — one  inferior,  embracing  the  head  of  the  humerus ;  and  a  superior,  inserted 
into  the  margin  of  the  glenoid  cavity.  This  capsule  presents,  in  front,  two  sup- 
porting fasciculi,  which  diverge  as  they  descend  from  the  coracoid  process  to  the 
great  and  small  tuberosities.  The  aponeurotic  expansion  thus  formed  is  very 
thin  and  loose,  so  as  to  allow  the  two  bones  to  separate  to  the  extent  of  from 
-f*Q  to  y^o  of  an  inch  ;  but  it  is  far  from  being  sufficiently  strong  to  bind  them 
firmly  together.  The  articulation  is,  therefore,  strengthened  by  the  powerful 
muscles  which  surround  it,  among  which  maybe  noticed  :  1.  In  front,  the  coraco- 
radialis  (flexor  brachii),  separated  from  the  fibrous  capsule  by  an  adipose  cushion. 
2.  Behind,  the  large  extensor  of  the  forearm  and  scapulo-humeralis  gracilis  (or 
teres  minor)  muscles,  the  use  of  which  appears  to  be  to  pull  up  this  capsule  during 
the  movements  of  flexion,  so  as  to  prevent  its  being  pinched  between  the  articular 
surfaces.  3.  Outwards,  the  short  abductor  of  the  arm  and  the  infra-spinatus  (postea 
spinatus)  tendon.  4.  Inwards,  the  wide  and  strong  tendon  of  the  subscapularis 
muscle.  In  addition  to  this  powerful  retaining  apparatus,  there  is  the  atmospheric 
pressure,  the  influence  of  which  is  of  a  certain  importance.  This  may  be  proved 
by  removing  all  the  surrounding  muscles,  when  it  will  be  found  that  the  capsule 
is  not  relaxed,  nor  are  the  articular  surfaces  separated  ;  to  effect  this,  it  is  neces- 
sary to  make  an  opening  in  the  capsule,  so  as  to  allow  the  air  to  enter  its  cavity, 
when  the  surfaces  immediately  fall  apart. 

Synovial  capsule. — This  is  very  loose,  and  entirely  enveloped  by  the  peripheral 
capsule,  the  internal  surface  of  which  it  lines. 

Movements. — Like  all  the  enarthrodial  articulations,  the  scapulo-humeral 
permits  extension,  flexion,  abduction,  adduction,  circumduction,  and  rotation.  These 
various  movements,  however,  are  far  from  being  so  extensive  as  in  Man,  the  arm 
in  the  domesticated  animals  not  being  detached  from  the  trunk,  but,  on  the 
contrary,  is  fixed  with  the  shoulder  against  the  lateral  parietes  of  the  thorax. 
Flexion  and  extension  are  the  least  limited,  and  the  most  frequently  repeated 
movements  ;  their  execution  always  demands  a  displacement  of  the  two  bones, 
wliich  are  almost  equally  movable.  In  flexion,  the  scapulo-humeral  angle  is 
closed,  not  only  because  the  inferior  extremity  of  the  humerus  is  carried  back- 
wards and  upwards,  but  also  because  the  scapula  pivots  on  its  superior  attach- 


ARTICULATIONS  OF  TEE  ANTERIOR  LIMBS.  1S5 

merits  in  such  a  manner  as  to  throw  its  glenoid  angle  forward  and  upward. 
Extension  is  produced  by  an  inverse  mechanism.  During  the  execution  of  the 
other  movements,  the  scapula  remains  fixed,  and  the  humerus  alone  is  displaced, 
bringing  with  it  the  inferior  bones  of  the  limb.  If  it  is  carried  outwards,  we 
have  abduction,  or  inwards,  adduction  ;  if  the  leg  passes  successively  from  flexion 
to  abduction,  and  from  that  to  extension,  etc.,  in  describing  a  circle  by  its  lower 
extremity,  then  there  is  circumduction ;  if  it  pivots  from  left  to  right,  or  right  to 
left,  we  have  rotation. 

In  the  Pig,  Dog,  and  Cat,  the  synDvial  membrane  is  not  exactly  enclosed  by  the  fibrous 
capsule,  but  forms  in  front  a  cul-de-sac,  which  descends  in  the  bicipital  groove  to  favour  the 
gliding  of  the  coraco-radialis  tendon. 

In  Man,  the  scapulo-humeral  articulation  is  disposed  as  in  animals,  but  it  is  also  protected 
above  by  the  coraco-acromion  arch.  For  the  reasons  noted  above,  this  articulation  allows  of 
more  extensive  motion  than  in  animals.  As  remarked  by  Cruveilhier,  of  all  the  joints  in  the 
human  body,  tlie  scapulo-humeral  is  that  which  has  the  most  extensive  motion;  in  movements 
forward  and  outward,  the  humerus  can  become  horizontal;  in  those  of  circumduction  it 
describes  a  complete  cone,  which  is  more  extensive  in  front  and  laterally  than  behind  and 
inwardly. 

2.  HuMERO-RADiAL,  OE  Elbow  Aeticulation  (Fig.  128). 

(^Preparation. — Turn  down  the  inferior  extremity  of  the  flexors  of  the  forearm,  remove  the 
•olecranian,  epicondyloid,  and  epitrochlean  muscles,  taking  care  not  to  damage  the  ligaments 
to  which  they  somewhat  closely  adhere.) 

Three  bones  concur  to  form  this  articulation,  which  presents  a  remarkable 
•example  of  an  angular  ginglymus  :  the  humerus,  by  its  inferior  extremity,  and 
the  two  bones  of  the  arm  by  their  upper  extremities. 

Artkidar  surfaces. — The  humeral  surface,  already  described  at  page  102,  is 
transversely  elongated,  and  convex  from  before  to  behind.  It  presents  :  1.  A 
median  groove  excavated  by  a  synovial  fossette.  2.  An  external  groove  (humeral 
trochlea)  not  so  deep  as  the  preceding.  3.  A  kind  of  voluminous  condyle  wliich 
borders,  inwardly,  the  internal  pulley,  and  whose  antero-posterior  diameter  is 
much  greater  than  that  of  the  external  lip  of  the  trochlea  of  the  opposite  side. 
The  antibrachial  surface,  divided  into  two  portions,  is  moulded  to  the  humeral 
surface  ;  it  is,  therefore,  concave  before  and  behind,  and  is  composed  :  1.  Of  a 
double  external  groove.  2.  Of  an  internal  glenoid  cavity,  both  excavated,  on  the 
superior  extremity  of  the  radius.  3.  A  middle  ridge  for  the  middle  groove  of 
the  humerus,  separating  the  two  preceding  surfaces,  and  prolonged  on  the  ulnar 
beak,  where  it  forms  the  sigmoid  notch.  This  ridge  shows  a  small  synovial 
fossette  hollowed  out  on  the  radius  and  ulna. 

Mode  of  union. — Three  ligaments  :  two  lateral  and  an  anterior. 

a.  The  external  lateral  ligament  (Figs.  128,  8)  is  a  thick,  short,  and  strong 
funicle,  attached  above  to  the  crest  limiting  outwardly  and  posteriorly  the  musculo- 
.spiral  groove,  and  in  the  small  cavity  placed  at  the  external  side  of  the  humeral 
articular  surface.  Below,  it  is  inserted  into  the  supero-external  tuberosity  of  the 
radius.  Its  anterior  border  is  confounded  with  the  capsular  ligament,  and  is 
margined  by  the  principal  extensor  of  the  phalanges,  which  derives  from  it 
numerous  points  of  attachment.  By  its  posterior  border  it  is  in  contact  with 
the  external  flexor  of  the  metacarpus.  Its  internal  face  is  lined  by  synovial 
membrane,  and  its  external  face  is  only  separated  from  the  skin  by  the  anti- 
brachial aponeurosis,  and  some  of  the  fasciculi  from  the  origin  of  the  lateral 
extensor  muscle  of  the  phalanges.     Its  superficial  fibres  are  vertical,  and  are 


196 


THE  ARTICULATIONS. 


continuous,  behind,  with  the  arcif orm  ligamentous  bands  which  stretch  from  the 
ubia  to  the  radius.     Its  deep  fibres  are  shghtly  obUque  downwards  and  forwards. 
b.  The  lateral  internal  ligament — also  funicular — is  longer,  but  not  so  strong 

as  the  preceding.      It  arises  from 
Fig.  128.  the  small  tuberosity  on  the  inner 

side  of  the  superior  articular  face 
of  the  humerus,  and,  widening  as 
it  descends,  reaches  the  radius.  Its 
median  fibres,  which  are  the  longest, 
are  directed  vertically  downwards 
to  reach  the  imprints  situated  below 
the  bicipital  tuberosity  ;  its  anterior 
fibres,  curved  forwards,  are  united 
to  the  tendon  of  the  coraco-radialis 
muscle,  or  are  confounded  ^^■ith  the 
anterior  ligament ;  the  posterior  are 
turned  backwards,  near  their  in- 
ferior extremities,  to  join  the  arci- 
form  fibrous  fascicuU,  which  in- 
wardly unite  the  ulna  to  the  radius. 
The  middle  fibres  of  this  Ugament 
cover  the  inferior  insertion  of  the 
short  flexor  of  the  forearm,  and — in 
part  only — that  of  the  long  flexor. 
It  is  covered  by  the  ulna-plantar 
nerve  and  the  posterior  radial  artery 
and  vein. 

c.  The  anteiior  or  capsular  liga- 
ment (Figs.  128,  9)  is  a  membrani- 
form  band,  attached  by  its  superior 
border  above  the  humeral  articular 
surface,  and  by  its  inferior  to  the 
anterior  margin  of  the  radial  sur- 
face. By  its  lateral  borders,  it  is 
confounded  with  the  funicular  Uga- 
ments.  Its  internal  half  is  formed 
of  vertical  fibres  which  descend  from 
the  humerus  and  expand  over  the 
radius,  where  they  become  united 
with  the  inferior  tendon  of  the 
coraco-radialis  muscle.  In  its  exter- 
nal moiety  it  is  extremely  thin,  and 
composed  of  fibres  crossed  in  various 
directions.  Lined  internally  by 
synovial  membrane,  this  ligament  is 
in  contact,  by  its  external  surface, 
with  the  anterior  radial  vessels  and 
nerves,  the  two  flexor  muscles  of 
the  forearm,  the  anterior  extensor  of 
the  metacarpus,  and  the  anterior  extensor  of  the  phalanges.    The  two  latter  muscles 


6capul0-humeral  and  humero-radial  articula- 
tions, with  the  muscles  surrounding  them 
(external  face). 

1,  Scapulo-humeral  capsular  ligament ;  2,  short  ab- 
ductor muscle  of  the  arm  ;  3,  its  insertion  in  the 
humerus;  4,  insertion  of  the  infra-spinatus  muscle 
on  the  crest  of  the  great  tuberosity;  5,  coraco-radialis 
muscle;  tj,  its  tendon  of  origin  ;ittached  to  the 
coracoid  process;  7,  its  radial  insertion  confounded 
with  the  anterior  ligament  of  the  ulnar  articula- 
tion ;  8,  8,  external  lateral  ligament  of  that  articu- 
lation ;  9,  anterior  ligament ;  10.  aconeus,  or  small 
extensor  of  the  forearm  ;  11,  origin  of  the  external 
flexor  muscle  of  the  metacarpus;  12,  short  flexor 
muscle  of  the  forearm.  A,  Tuberosity  of  the  scapii- 
lar  spine;  B,  supra-spinous  fossa;  C,  infra-spinous 
fossa :  D,  convexity  of  the  small  trochanter ;  E, 
summit  of  the  ti-ochanter. 


ABTICDLATIONS  OF  THE  ANTERIOR   LIMBS.  197 

are  even  attached  to  it  in  a  very  evident  manner.  The  elbow  articulation,  closed 
in  front  and  on  the  sides  by  the  tliree  ligaments  just  described,  has  no  particular 
ligaments  posteriorly  ;  but  it  is  powerfully  strengthened  there  by  the  olecranian 
insertion  of  the  extensor  muscles  of  the  forearm,  and  by  the  tendons  of  origin  of 
the  five  flexor  muscles  of  the  metacarpus  or  phalanges. 

Synovial  membrane. — This  membrane  is  very  extensive,  and,  stretched  out 
on  the  internal  face  of  the  before-mentioned  hgaments,  forms,  behind,  three  great 
culs-de-sac  of  prolongment  :  a  superior,  occupying  the  olecranian  fossa,  and 
covered  by  a  fatty  cushion,  as  well  as  by  the  small  extensor  muscle  of  the  fore- 
arm ;  ^  two  lateral,  which  descend  from  each  side  of  the  ulnar  beak,  and  are 
■distinguished  as  internal  and  external — the  first  lines  the  tendon  of  the  external 
flexor  of  the  metacarpus,  the  second  facilitates  the  play  on  the  upper  radial 
extremity  of  the  four  flexor  muscles  of  the  foot  or  digits,  and  which  are  attached 
in  common  to  the  epitrochlea.  This  synovial  sac  also  furnishes  the  radio-ulnar 
articulation  with  a  diverticulum,  which  descends  between  the  bones  of  the  fore- 
arm to  below  the  adjacent  diarthrodial  facets. 

Movements. — Flexion  and  extension. 

In  flexion,  the  two  bones  do  not  approach  each  other  directly,  the  inferior 
extremity  of  the  radius  deviating  a  little  outwards.  This  is  due  more  to  the 
.sHght  obliquity  of  the  articular  grooves,  than  to  the  difference  in  thickness 
between  the  external  and  internal  extremities  of  the  humeral  surface. 

Extension  is  limited  by  the  reception  of  the  beak  of  the  olecranon  in  its  fossa, 
and  by  the  tension  of  the  lateral  ligaments  ;  so  that  the  two  bones  cannot  be 
straightened  on  one  another  in  a  complete  manner,  or  placed  on  the  same  line. 

In  the  Dog  and  Cat,  tlie  external  lateral  ligament  is  very  thick,  and  forms  in  its  inferior 
moiety  a  fibro-cartilaginous  cap  wliich  is  fixed  on  the  ulna  and  radius,  and  united  in  front  to 
the  annular  ligament  of  the  superior  radio-ulnar  joint.  This  cap,  with  the  last-named  liga- 
ment, completes  the  osteo-fibrous  ring  in  wliich  the  superior  extremity  of  the  radius  turns. 
The  internal  lateral  ligament  is  inserted,  by  two  very  short  fasciculi,  into  the  ulna  and  inner 
side  of  the  head  of  tlie  radius.  A  third  fasciculus,  deeper  and  median,  much  more  developed 
than  the  first,  and  covered  by  the  inferior  insertion  of  the  flexors  of  tlie  forearm,  descends 
between  the  radius  and  ulna  to  the  posterior  face  of  the  former,  and  is  there  inserted  near  the 
inferior  attachment  of  the  external  ligament,  which  it  appears  as  if  about  to  join. 

In  Man,  the  elbow  articulation  is  formed  nearly  on  the  same  plan  as  that  of  the  Dog  and 
Cat.     The  radius  and  ulna  move  together  when  the  forearm  is  flexed  and  extended  on  the 
humerus. 
• 

3.  Radio-ulnar  Articulation. 

Jirticular  surfaces. — The  two  bones  of  the  forearm  articulate  by  diarthrodial 
'and  synarthrodial  surfaces. 

a.  The  diarthrodial  surfaces  consist  of  four  undulated,  transversely  elongated 
facets,  two  of  which  are  radial  and  two  idnar.  The  first  border,  posteriorly,  the 
great  articular  surface  forming  the  elbow- joint ;  the  second  are  situated  beneath 
the  sigmoid  notch. 

h.  The  synarthrodial  surfaces  are  plane  and  roughened,  and  are  also  two  on 
each  bone  :  one,  superior,  extends  below  the  diarthrodial  facets  to  the  radio-ulnar 
arch  ;  the  other,  inferior,  more  extensive,  occupies  all  the  anterior  face  of  the 
ulna  from  this  arch  ;  on  the  radius  it  forms  a  very  elongated  triangular  imprint, 
which  descends  to  the  lower  fourth  of  the  bone  (see  pp.  104,  105). 

'  Some  grey  elastic  fibres  which  cover  this  cul-de-sac  externally,  have  been  wrongly 
described  as  a  posterior  membraniform  ligament. 


198  THE  ABTICV LATIONS. 

Mode  of  union. — Two  interosseous  and  two  peripheral  ligaments. 

a.  The  interosseous  ligaments,  interposed  between  the  synarthrodia!  surfaces,, 
are  composed  of  extremely  short  white  fibres  passing  from  one  to  the  other 
surface,  and  which  are  endowed  with  a  very  remarkable  power  of  resistance.  The 
inferior  always  ossifies  a  long  time  before  the  animal  is  full  grown — a  circum- 
stance which  caused  the  older  veterinary  anatomists  to  describe — and  with  some 
show  of  reason — the  radius  and  ulna  as  a  single  bone.  Ossification  of  the  superior 
ligament  is  very  rare. 

b.  The  peripheral  bands  are  bundles  of  arciform  fibres  which,  from  the  beak 
of  the  olecranon  to  the  radio-ulnar  arch,  leave  the  lateral  faces  of  the  ulna  to 
pass — some  inwards,  others  outwards — to  the  posterior  face  of  the  radius.  The 
fibres  of  the  external  ligament  are  confounded  with  the  external  humero-radial 
ligament.  The  internal  fibres  are  united  to  the  internal  humero-radial  ligament,. 
and  to  the  small  ulnar  tendon  belonging  to  the  short  flexor  of  the  forearm. 
Analogous  fibres  are  found  beneath  the  radio-ulnar  arch  ;  but  they  are  much 
shorter  and  less  apparent.  (This  is  the  external  transverse  radio-idnar  ligament 
of  Leyh.) 

Movements. — Very  obscure  in  youth ;  nearly  null  when  the  two  bones  are 
fused  together. 

In  the  Ox,  ossification  of  the  superior  interosseous  ligament  is  constant  at  adult  age. 

In  the  Dog  anti  Cat,  we  have  already  seen  (p.  107)  that  the  radius  and  uhia  are  not  fused 
to  each  other,  but  remain  independent  during  life.  They  are  united  in  their  middle  portion 
by  an  interosseous  ligament,  and  join  by  diarthrosis  at  their  two  extremities.  These  animals 
therefore  exhibit;  1.  An  interosseous  ligament.  2.  A  superior  radio-ulnar  articulation.  3. 
An  inferior  radio-ulnar  articulation. 

Interosseous  ligament. — It  is  composed  of  very  resisting  white  fibres,  attached  by  their 
extremities  to  the  bodies  of  the  bones.  Notwithstanding  their  sliortneas,  they  are  loose  enough 
to  allow  movements  taking  place  between  the  radio-ulnar  articulations. 

Superior  radio-ulnar  articulation. — This  is  a  trochoid  articulation,  which  only  allows 
movements  of  rotation  or  pivoting. 

The  articular  swr/'aees  which  form  this  articulation  are:  in  the  ulna,  the  small  sigmoid 
cavity — a  surface  excavated  in  the  lateral  sense,  and  semicircular;  in  the  radius,  a  cylindrical 
half-liinge  received  into  the  preceding  cavity. 

To  unite  these  there  is  an  annular  ligament — a  kind  of  fibrous  web  thrown  around  the 
superior  extremity  of  the  radius,  fixed  inwardly  on  the  ulna  near  the  inner  extremity  of  the 
small  sigmoid  cavity,  attached  outwardly  to  the  external  lateral  ligament  of  the  elbow^ 
articulation,  and  confounded  superiorly  with  the  anterior  ligament  of  the  same  articulation. 
This  fibrous  web,  in  uniting  with  the  fibro-cartilaginous  cap  of  the  external  humero-radial 
ligament,  and  joining  the  small  sigmoid  cavity  by  its  iiiternal  extremity,  transforms  this  last 
into  a  complete  ring,  covered  with  cartilage  in  its  bony  portion.  The  head  or  superior 
extremity  of  the  radius  is  also  encrusted,  over  its  entire  contour,  with  a  layer  of  cartilage — a  con- 
dition which  pt-rmits  it  to  glide  not  only  in  the  concave  face  of  the  small  sigmoid  cavity,  but 
also  on  the  internal  face  of  the  two  ligaments  which  complete  this  cavity. 

Inferior  radio-ulnar  articulation. — This  is  also  a  trochoid  articulation  analogous  to  the  pre- 
ceding, but  inversely  disposed.  Thus,  the  concave  articular  surface  is  hollosved  on  the  radius, 
outside  tlie  inferior  extremity;  the  convex  surface  lies  within  the  ulna.  These  two  facets  are 
very  small,  and  are  maintained  in  ctmtact  by  a  diminutive  peripheral  fibrous  capsule.  A 
strong  interosseous  ligament,  situated  beneath  the  articular  facets,  also  consolidates  this 
diatlirosis,  and  concurs  by  its  inferior  border  to  form  the  antibrachial  surface  of  the  radio-carpal 
articulation.     A  small  synovial  capsule  is  specially  devoted  to  this  articulation. 

Mechanism  of  the  radio-ulnar  joints. — The  play  of  these  two  articulations  is  simultaneous,, 
and  tends  to  the  same  end— that  is,  to  the  execution  of  the  double  rotatory  movement  which 
constitutes  supination  and  pronation. 

Supination  is  when  the  ulna  remains  fixed,  and  the  radius  pivots  on  it  in  such  a  manner  as 
to  carry  its  anterior  face  outwards.  Its  superior  extremity  then  turns  from  within  forwards — 
and  even  from  before  outwartls  if  the  movement  is  exaggerated,  in  the  articular  girdle  formed 


ARTICULATIONS  OF  THE  ANTERIOR   LIMBS.  199 

by  the  small  sigmoid  cavity  of  the  ulna  and  the  ligaments  which  complete  it.  The  inferior 
extremity  also  rolls  on  the  ulnar  facet  in  describing  a  similar  movement,  and  the  internal 
tuberosity  of  this  extremity  is  carried  forwards. 

In  the  movement  of  pronation,  this  tuberosity  is  brought  inwards,  and  the  anterior  face  of 
the  radius  comes  forward  by  an  opposite  mechanism. 

The  inferior  bone  of  the  anterior  limb  being  articulated  in  a  hinge-like  manner  with  the 
radius,  it  follows  this  bone  in  its  rotatory  movements,  the  anterior  face  of  the  metacarpus 
looking  outwards  during  supination  and  forwards  in  pronation. 

The  radio-ulnar  articulation  in  Man  resembles  that  of  the  Dog  and  Cat,  the  articular 
surfaces  only  being  larger  and  the  movements  more  extensive.  In  supination,  the  palmar  face 
is  turned  forward,  and  the  radius,  situated  on  the  outer  side  of  the  ulna,  is  in  the  same  direction 
as  the  latter.  In  pronation,  on  the  contrary,  the  palmar  face  of  the  hand  looks  backwards,  and 
the  radius — remaining  outwards  in  its  upper  part — crosses  the  ulna  in  front  in  such  a  manner 
that  its  lower  extremity  is  placed  witliiu  the  ulna. 

4.  Articulations  of  the  Carpus  (Figs.  129,  130) 

Preparation. — After  removing  the  tendons  surrounding  the  carpus,  the  ligaments  cbmmon 
to  all  the  carpal  articulations  can  be  studied.  The  anterior  and  posterior  membraniform 
ligament  can  tben  be  removed,  and  the  ligaments  proper  to  each  row,  as  well  as  those  uniting 
the  two  rows,  and  these  to  adjoining  bones,  can  be  dissected.  Some  time  is  required  for  this 
dissection,  which  is  not  difficult. 

These  comprise  :  1.  The  articulations  uniting  the  carpal  bones  of  the  first 
row  to  each  other.  2.  The  analogous  articulations  of  the  second  row.  3.  The 
radio-carpal  articulation.  4.  The  articulation  of  the  two  rows  with  each  other. 
5.  The  carpo-metacarpal  articulation. 

Articulations  which  unite  the  Bones  of  the  First  Row  to  each 
other. — These  bones,  four  in  number,  are  joined  by  the  diarthrodial  facets  on 
their  lateral  faces,  and  form  small  arthrodial  articulations.^  They  are  maintained 
in  contact  by  six  ligaments,  three  anterior,  and  three  interosseous.  The  anterior 
ligaments  are  small  flattened  bauds  carried  from  the  fourth  bone  to  the  first, 
from  the  first  to  the  second,  and  from  that  to  the  third.  The  first,  placed 
outside  rather  than  in  front  of  the  carpus,  is  covered  by  the  external  lateral 
ligament  and  the  inferior  tendon  of  the  external  flexor  of  the  metacarpus  ;  the 
others  adhere  to  the  capsular  ligament.  The  interosseous  ligaments  are  implanted 
in  the  grooves  of  insertion  which  separate  the  diarthrodial  facets.  One  of  them, 
derived  from  the  common  superior  ligament,  unites  the  first  to  the  second  bone. 
The  two  others,  situated  between  the  three  last  carpal  bones,  are  confounded 
with  the  corresponding  anterior  ligaments. 

Articulations  uniting  the  Carpal  Bones  of  the  Second  Row. — 
These  are  arthrodial  articulations,  like  the  preceding,  but  numbering  only  two. 
They  are  fixed  by  two  anterior  and  two  interosseous  ligaments.  One  of  the 
anterior  ligaments  joins  the  first  bone  to  the  second,  and  strongly  adheres  to  the 
capsular  ligament  ;  the  other  is  entirely  covered  by  the  lateral  internal  ligament, 
and  attaches  the  two  last  bones  to  each  other.  Of  the  two  interosseous  ligaments, 
the  second  alone  is  confounded  with  the  corresponding  anterior  ligament.  That 
which  is  situated  between  the  two  first  bones  is  separated  from  the  anterior 
hgament  by  one  of  the  diarthrodial  facets  between  these  bones. 

Radio-carpal  Articulation. — The  inferior  extremity  of  the  radius,  in 
becoming  united  to  the  upper  row  of  carpal  bones,  constitutes  a  diarthrosis 
which,  from  the  nature  of  the  movements  it  permits,  may  be  considered  as 
an  imperfect  hinge- joint. 

'  The  facet  uniting  the  supercarpal  to  the  first  bone  is  not  situated  on  one  of  its  faces,  but 
rather  on  the  anterior  part  of  its  circumference. 


200  THE  ARTICULATIONS. 

Articular  surfaces. — The  radial  surface,  elongated  transversely  and  very 
irregular,  presents  :  1,  Outwardly,  a  wide  groove,  limited  in  front  by  a  small 
glenoid  cavity,  and  bounded,  posteriorly,  by  a  non-articular  excavation  which 
receives  a  prolongation  of  the  second  bone  in  the  movement  of  flexion  ; 
2,  Inwardly,  a  condyle  with  a  more  extensive  curvature  than  that  of  the  pre- 
ceding groove,  and,  like  it,  completed  by  a  small  anterior  glenoid  cavity.  The 
carpal  surface,  moulded  exactly  on  the  radial,  offers  depressions  corresponding 
to  the  projections  on  it,  and  rice  verm. 

Mode  of  union. — The  radio-carpal  articulation  is  bound  by  three  ligaments 
which  entirely  belong  to  it ;  and  by  four  stronsf  ligaments  that  are  common  to 
it  and  articulations  which  will  be  studied  hereafter. 

Of  the  three  ligaments  proper  belonging  to  the  radio-carpal  articulation, 
one  forms  a  thick,  rounded  funicle,  extending  from  the  radius  to  the  fourth 
bone  in  an  oblique  direction  downwards  and  inwards,  and  concealed  by  the 
common  posterior  ligament.  The  second  (Fig.  130,  5),  much  smaller,  is  carried 
from  the  supercarpal  bone  to  the  external  side  of  the  inferior  extremity  of  the 
radius,  and  is  partly  covered  by  the  common  external  ligament.  When  the 
synovial  capsule  is  distended  by  dropsy,  it  may  form  a  hernia  at  the  outer  side 
of  the  carpus,  by  passing  between  this  small  ligament  and  the  common  posterior 
ligament.  The  third,  very  delicate,  but  always  present,  is  deeply  situated  beneath 
the  last ;  it  is  inserted,  for  one  part,  into  the  radius  near  the  first  proper 
ligament,  and  for  the  other,  into  the  second  bone  and  the  interosseous  ligament 
which  unites  the  supercarpal  to  that  bone. 

tSi/norial  membrane. — After  lining  these  three  ligaments,  and  the  four  great 
ligaments  yet  to  be  described,  this  membrane  is  prolonged  between  the  three 
first  carpal  bones,  to  cover  the  superior  face  of  the  interosseous  ligaments  which 
unite  them.  It  even  more  frequently  descends  into  the  articulation  which  joins 
the  supercarpal  to  the  first  bone  ;  though  it  also  sometimes  happens  that  this 
has  a  particular  synovial  capsule  of  its  own. 

Akticulation  of  the  Two  Rows  between  each  other. — Like  the  pre- 
ceding, this  is  an  imperfect  hinge  articulation. 

Articnlar  surfaces. — These  are  two,  and  are  both  transversely  elongated,  very 
irregular  in  their  configuration,  and  divided  into  three  portions.  The  inferior 
shows  :  behind,  three  small  condyles  placed  side  by  side  ;  in  front,  two  slightly 
concave  facets.  The  superior  corresponds  to  the  first  by  three  glenoid  cavities 
and  two  convex  facets. 

3Io(le  of  anion. — For  this  articulation,  besides  the  common  great  ligaments, 
there  are  three  particular  ligaments.  Two  of  these  are  very  short,  and  are 
situated  behind  the  carpus,  underneath  the  great  common  posterior  ligament. 
They  are  readily  perceived  by  removing  the  capsular  ligament,  and  strongly 
flexing  the  carpus.  "  The  strongest  extends  vertically  from  the  internal  bone  of 
the  superior  row  to  the  second  and  third  bones  of  the  metacarpal  row  ;  the  other 
descends  obliquely  from  the  first  bone  of  the  antibrachial  row  to  the  second 
of  the  inferior  row  "  (Rigot).  The  third  ligament  proper,  much  stronger  than 
the  other  two,  reaches  from  the  supercarpal  to  the  first  bone  of  the  inferior  row 
and  the  head  of  the  external  metacarpal  bone.  It  is  confounded,  outwardly, 
with  the  great  external  lateral  ligament  ;  inwardly,  with  the  common  posterior 
ligament.  Its  posterior  border  gives  attachment  to  the  fibrous  arch  which 
completes  the  carpal  sheath.  This  ligament  has  also  a  branch  which  is  fixed  on 
the  second  bone  of  the  upper  row  (Fig.  130,  4). 


ARTICULATIONS   OF  THE  ANTERIOR  LIMBS. 


201 


Fig.  129. 


Synovial  membrane. — This  lines  all  the  ligaments,  and  is  prolonged  above 
and  below,  between  the  carpal  bones,  to  facilitate  the  gliding  of  their  articular 
facets.  Two  upper  prolongations  ascend  between  the  three  first  bones  of  the 
antibrachial  row,  to  cover  the  inferior  face  of  the  interosseous  ligaments  uniting 
them.  Two  other  prolongations  descend  between  the  carpal  bones  of  the  second 
row  ;  the  external,  after  covering  the  first  interosseous  ligament,  passes  between 
it  and  the  corresponding  anterior  ligament,  and  communicates  with  the  synovial 
capsule  of  the  carpo-metacarpal  articulation.  The  internal 
forms  a  cul-de-sac  which  rests  on  the  interosseous  ligament. 

Carpo-Metacarpal  Articulation. — The  carpal  bones  of 
the  second  row  articulate  with  the  superior  extremity  of  the 
metacarpal  bones,  constituting  a  planiform  diarthrosis. 

Articular  surfaces. — These  are,  on  each  side,  plane  facets 
more  or  less  inclined  one  on  the  other,  and  continued  between 
each  other.  The  largest  is  in  the  middle,  and  is  generally 
hollowed  by  a  small,  shallow,  synovial  fossette. 

Mode  of  union. — There  are  the  four  great  common  liga- 
ments, and  also  six  specicd  ligaments  .-  two  anterior,  two  posterior, 
and  two  interosseous. 

Of  the  two  anterior  ligaments  (Fig.  129,  2,  2),  one  is  divided 
into  two  distinct  bands,  and  unites  the  second  bone  to  the 
principal  metacarpal  ;  the  other,  concealed  by  the  external 
lateral  ligament,  attaches  the  first  bone  to  the  head  of  the  ex- 
ternal metacarpal  bone. 

The  two  posterior  Hgaments  described  by  Rigot  do  not 
appear  to  us  to  be  suificiently  distinct  from  the  great  ligament 
to  merit  a  special  description. 

The  two  interosseous  ligaments,  completely  overlooked  by 
that  able  anatomist,  start  from  the  interstices  which  separate 
the  median  metacarpal  bone  from  the  lateral  metacarpals,  and 
join  the  interosseous  ligaments  of  the  second  row  ;  they  are 
thick  and  short.  We  have  sometimes  noted  one  or  other  of 
them  to  be  absent. 

Synovial  membrane. — This  communicates,  as  indicated  above,  with  the 
synovial  capsule  of  the  preceding  articulation.  It  furnishes  a  superior  cul-de-sac, 
which  rests  on  the  interosseous  ligament  interposed  between  the  two  last  cai-pal 
bones  of  the  second  row.  Two  inferior  culs-de-sac  descend  into  the  inter- 
metacarpal arthrodial  articulations. 

Ligaments  common  to  the  three  preceding  Articulations. — As  before 
mentioned,  these  are  four  in  number :  two  lateral,  one  anterior,  and  one 
posterior. 

a.  The  externcd  lateral  ligament  (Figs.  129,  3  ;  130,  3)  is  a  thick  funicular  cord 
composed  of  two  orders  of  fibres — a  deep-seated  and  a  superficial  order,  slightly 
crossed.  It  leaves  the  external  and  inferior  tuberosity  of  the  radius,  descends 
vertically  to  the  side  of  the  carpus,  transmits  a  fasciculus  to  the  first  bone  of  the 
upper  row,  gives  off  another  fasciculus  which  stops  at  the  external  bone  of  the 
second  row,  and  terminates  on  the  head  of  the  corresponding  metacarpal  bone. 
Traversed  obliquely  by  the  lateral  extensor  of  the  phalanges,  this  ligament  covers 
the  external  carpal  bones.  In  front,  it  is  united  to  the  capsular  ligament ;  near 
its  inferior  extremity,  it  is  confounded  with  the  strong  ligament  which  joins  the 


carpal  articula- 
tions (front 
view). 

1,  1,  Anterior  liga- 
ments uniting  the 
carpal  bones  of 
each  row ;  2, 2,  an- 
terior ligaments 
proper  to  the 
carpo  -metacarpal 
articulation  ;  3. 
common  external 
ligament ;  4,  com- 
mon internal  liga- 
ment. 


ao2 


THE  ARTICULATIONS. 


Fig.  130. 


supercarpal  bone  to  the  first  bone  of  the  inferior  row  and  to  the  head  of  the 
external  metacarpal  bone. 

b.  The  internal   lateral  ligament  (Fig.  129,  4),  analogous  to   the  preceding 

and  situated  on  the  opposite  side,  is  wider  and  thicker  than  it.     It  commences  on 

the  internal  tuberosity  of  the  radius,  and  terminates  on  the  upper  extremity  of 

the  middle  and  internal  metacarpal  bones,  after  being  attached,  by  two  distinct 

fasciculi,  to  the  third  carpal  bone  of  the  upper  row,  and 

the  two  last  of  the  metacarpal  row.      In  contact  by  its 

external  face  with  the  tendon  of  the  oblique  extensor  muscle 

of  the  metacarpus,  this  ligament  responds,  by  its  deep  face, 

to  the  synovial  membranes  of  the  carpus  and  to  the  bones 

to  which  it  is  attached.    By  its  anterior  border  it  is  united 

to  the  capsular  ligament ;  the  opposite  border  is  intimately 

confounded  with  the  posterior  ligament,  from  wliich  it  is 

impossible  to  distinguish  it. 

c.  The  anterior,  or  capsular  ligament,  is  a  membranous 
band  covering  the  anterior  face  of  the  carpal  articulations. 
Its  superior  border  is  attached  to  the  radius  ;  the  inferior 
is  inserted  into  the  superior  extremity  of  the  principal 
metacarpal  bone.  The  two  right  and  left  borders  are 
united  with  the  lateral  ligaments.  Its  external  face  is  in 
contact  with  the  tendons  of  the  anterior  extensor  muscles 
of  the  metacarpus  and  phalanges.  The  internal  face  is 
lined  at  certain  points  by  synovial  membrane,  and  adheres 
in  others  to  the  carpal  bones  and  the  anterior  ligaments 
binding  these  to  one  another.  This  ligament  is  composed 
of  transverse  fibres  more  or  less  oblique,  and  arranged  cross- 
wise ;  by  its  amplitude  it  can  adapt  itself  to  the  movements 
of  flexion  of  the  knee. 

d.  The  posterior  ligament,  one  of  the  strongest  in  the 
animal  economy,  covers  the  posterior  face  of  the  carpus, 
filling  up  the  asperities  which  roughen  it.  It  is  inserted  : 
above,  on  the  transverse  crest  surmounting  the  articular 
surface  of  the  radius  ;  by  its  middle  portion  into  all  the 
carpal  bones  ;  below,  into  the  head  of  the  principal  meta- 
carpal bone.  Confounded  inwardly  with  the  internal 
lateral  ligament,  united  outwardly  to  the  band  which  at- 
taches the  supercarpal  to  the  external  metacarpal  and  the  second  carpal  bone  of 
the  upper  row,  this  ligament  is  continued,  by  its  inferior  extremity,  with  the  carpal 
stay  (or  check  ligament)  which  sustains  the  perforans  tendon.  Its  posterior  face 
is  perfectly  smooth,  and  is  covered  by  the  synovial  membrane  of  the  carpal 
sheath. 

Movements  of  thf  Carpal  Articulations. — The  carpus  is  the  seat  of 
two  very  extensive  and  opposite  movements— flexion  and  extension;  to  wliich 
are  added  three  very  limited  accessory  movements — adduction,  abduction,  and 
circumduction. 

All  the  carpal  articulations  do  not  take  an  equal  part  in  the  execution  of 
these  movements  ;  for  it  is  easy  to  discover  that  they  are  chiefly  performed  in  the 
radio-carpal  diarthrosis,  and  in  the  imperfect  hinge  articulation  uniting  the  two 
rows  of  carpal  bones.     Each  of  these  articulations  participates  in  the  movements 


LATERAL    VIEW    OF    THE 
CARPAL  ARTICOLATIONS. 

1,  1,  Anterior  ligaments 
uniting  the  two  rows 
of  carpal  bones;  2,  2, 
anterior  ligaments  pro- 
per to  the  carpo-meta- 
carpal  articulation  ;  3, 
common  external  liga- 
ment; 4,  one  of  the 
ligaments  proper  to  the 
articulation  of  the  two 
rows  (metacarpo-supra- 
carpal) ;  5,  one  of  the 
ligaments  proper  to 
the  radio-carpal  articu- 
lation (radio-supercar- 
pal).  A,  Groove  on  the 
external  surface  of  the 
supercarpal  bone,  for 
the  passage  of  the  ex- 
ternal flexor  of  the 
metacarpus. 


ARTICULATIONS   OF  THE  ANTERIOR   LIMBS.  203 

of  the  carpus  in  nearly  the  same  proportions,  and  both  act  in  an  identical  manner. 
Their  mechanism  is  most  simple. 

In  flexmi,  the  first  tier  of  bones  rolls  backwards  on  the  radius,  the  inferior 
row  moves  in  the  same  sense  on  the  upper,  the  metacarpus  is  carried  backwards 
and  upwards,  the  common  posterior  ligament  is  relaxed,  the  capsular  ligament 
becomes  tense,  and  the  articular  surfaces,  particularly  those  of  the  second  joint, 
separate  from  each  other  in  front.  In  extensmi,  the  metacarpus  is  carried  down- 
wards and  forwards  by  an  inverse  mechanism.  This  movement  stops  when  the 
ray  of  the  forearm  and  that  of  the  metacarpus  are  in  the  same  vertical  line.  In 
flexion,  these  bones  never  directly  approach  each  other,  the  inferior  extremity  of 
the  metacarpus  being  always  carried  outwards.  It  may  also  be  remarked,  that 
the  slight  movements  of  abduction,  adduction,  and  circumduction  of  the  carpus  are 
only  possible  at  the  moment  when  the  foot  is  flexed  on  the  forearm. 

With  regard  to  the  planiform  diarthroses  articulating  the  carpal  bones  of  the 
same  row,  they  only  allow  a  simple  gliding  between  the  surfaces  in  contact ;  and 
with  the  carpo-metacarpal  arthrodia  it  is  absolutely  the  same.  The  restricted 
mobility  of  these  various  articulations  has  but  a  very  secondary  influence  on  the 
general  movements  of  the  carpus  ;  but  it  nevertheless  favours  them  by  permitting 
the  carpal  bones  to  change  their  reciprocal  relations,  and  adapt  themselves,  during 
the  play  of  the  radio-carpal  and  intercarpal  hinges,  to  a  more  exact  coaptation  of 
the  articular  planes  which  they  form. 

In  the  other  animals,  the  carpal  articulations  have  the  same  essential  characteristics  we 
have  noticed  in  Solipeds.  The  four  principal  peripheral  bands  differ  but  little  in  them; 
though  in  the  Dog  and  Cat  they  are  lax  enough  to  allow  somewhat  extensive  lateral 
movements. 

5.  Intermetacarpal  Articulations. 

Each  lateral  metacarpal  bone  articulates  with  the  middle  one,  by  means  of 
diarthrodial  and  synarthrodial  surfaces,  for  the  description  of  which  refer  to  page 
112.  An  interosseous  ligament,  composed  of  very  short  and  strong  fasciculi,  is 
interposed  between  the  synarthrodial  surfaces,  and  binds  them  firmly  together. 
Its  ossification  is  not  rare.  The  diarthrodial  facets  are  maintained  in  contact  by 
the  preceding  ligament,  and  by  the  carpal  ligaments  inserted  into  the  head  of  the 
lateral  metacarpal  bones.  The  intermetacarpal  articulations  only  allow  a  very 
obscure,  vertical,  gliding  movement. 

In  the  Ox,  there  is  only  one  intermetacarpal  articulation,  which  is  much  simpler  than 
those  in  the  Horse. 

In  the  Pig,  the  four  metacarpal  bones  correspond,  at  tlieir  upper  extremity,  by  means  of 
small  diarthrodial  facets  on  their  sides.  Fibrous  fasciculi,  derived  from  the  great  anterior  and 
posterior  ligaments  of  the  carpus,  protect  these  intermetacarpal  articulations  before  and 
behind.  Other  fibres,  situated  between  the  adjacent  faces  of  the  metacarpal  bones,  are  real 
interosseous  ligaments. 

In  the  Dog  and  Cat,  the  four  great  metacarpal  bones  articulate  with  each  other  in 
almost  the  same  manner  as  in  the  Pig,  but  their  mobility  is  greater 

6.  Metacarpo-phalangeal  Articulation  (Figs.  131,  132). 

Preparation.— In  order  to  study  the  whole  of  this  articulation,  it  is  well  to  have  an  anterior 
limb  from  the  lower  fourth  of  the  forearm.  From  this  the  tendons  of  the  flexors  and  extensors 
of  the  phalanges  are  to  be  removed,  and  then  the  suspensory  ligament  of  the  fetlock,  anterior 
capsular  ligament,  lateral  ligaments,  and  the  superficial  inferior  sesamoid  ligament,  can  be 
dissected.  To  study  the  ligaments  which  bind  the  bones  forming  the  inferior  articular 
surface,  the  first  phalanx  and  sesamoid  bones  should  be  removed,  which  allows  of  the  dissection 


2M 


THE  ARTICULATIONS. 


of  the  inter-,  lateral,  and  inferior  sesamoid  middle  and  deep  ligaments.  An  injection  of  the 
eynovinl  capsule  brings  into  relief  some  features  which  are  interesting,  from  a  surgical  point 
of  view. 

This  is  a  perfect  hinge-joint,  formed  by  the  inferior  extremity  of  the  median 
metacarpal  bone  on  the  one  part,  and  the  superior  extremity  of  the  upper  phalanx 
and  sesamoids  on  the  other. 

Articular  surfaces. — For  the  metacarpal  bone,  there  are  two  lateral  condyles 
and  a  median  antero-posterior  eminence  ;  for  the  first  phalanx,  two  glenoid 
cavities  and  an  intermediate  groove  prolonged  posteriorly  on  the  anterior  face  of 
the  two  sesamoids.  Divided  in  this  manner  into  three  portions,  the  digital 
surface  is  well  constituted  for  solidity,  because  the  pressure  transmitted  to  this 

region  is  diminished  and. 

Fig.  131.  diffused   by  the   natural 

-*-  ^  elasticity   of    the    bands 

which  unite  these   three 
pieces  to  each  other. 

3Iode  of  union. — The 
means  of  union  may  be 
divided  into  two  cate- 
gories :  1.  Those  which 
join  together  the  several 
bones  of  the  inferior  sur- 
face. 2.  Those  which 
maintain  in  contact  the 
two  opposed  articular 
surfaces. 

A.  The  firet  have  re- 
ceived the  generic  name 
of  sesamoid  ligaments, 
and  are  six  in  number  : 
an  intersesamoid  ligament y 
which  holds  together  the 
two  complementary  bones 
of  the  digital  surface ; 
three  inferior  and  two 
lateral  sesamoid  ligaments, 
which  unite  these  bones 
to  the  first  phalanx. 
a.  The  intersesamoid  ligament  is  composed  of  fibro-cartilaginous  substance, 
that  appears  to  be  the  matrix  in  which  the  two  sesamoids  were  developed  ;  as  it 
is  spread  around  these  bones,  after  being  solidly  fixed  on  their  internal  face. 
Behind,  this  ligament,  in  common  with  the  posterior  face  of  the  sesamoids,  forms 
the  channel  (Fig.  131,  5)  in  which  the  flexor  tendons  glide.  In  front,  it  occupies 
the  bottom  of  the  intersesamoid  articular  groove. 

h.  The  inferior  sesamoid  ligaments,  situated  at  the  posterior  face  of  the  first 
phalanx,  are  distinguished  as  superficial,  middle,  and  deep. 

The  superficial  ligament  (Figs.  131,  14  ;  134,  8),  the  longest  of  the  three,  is  a 
narrow  band  flattened  before  and  behind.  It  arises  from  the  middle  of  the 
fibro-cartilaginous  mass  which  completes,  posteriorly,  the  superior  articular  surface 
of  the  second  phalanx,  and,  shghtly  widening,  ascends  to  the  base  of  the  sesamoids. 


DETAILS    OF    THE    METACARPO-PHAI.ANGEAL    ARTICULATION    OF 
THE    HORSE. 


A.  Middle  inferior  sesamoidean 
ligaments.  P.  First  phalanx 
(posterior  face).  1,  Inter 
sesamoidean  ligament  (pos- 
terior fnce);  2,  2,  lateral 
sesamoidean  ligaments ;  3, 
middle  inferior  sesamoidean 
ligament. 


B.  Deep  inferior  sesamoidean 
ligaments.  P.  First  phalanx  : 
1,  Inter-sesamoidean  liga- 
ment ;  2,  2,  lateral  sesa- 
moidean ligaments;  3,  in- 
ferior deep  sesamoidean  liga- 
ment. 


ARTICULATIONS   OF  THE  ANTERIOR  LIMBS. 

Fie;.  1 
into  which  it  is  inserted  by  becoming 
confounded  with  the  intersesamoid  liga- 
ments. Its  posterior  face,  lined  by  the 
synovial  membrane  of  the  so-called  sesa- 
moid sheath,  is  covered  by  the  flexor 
tendons ;  it  partly  covers  the  middle 
ligament. 

The  middle  ligament,  triangular  and 
radiating,  is  composed  of  three  particular 
fasciculi :  two  lateral  (seen  on  each  side 
of  the  superficial  ligament  in  Fig.  131, 
A  8),  and  a  median  which  has  been 
generally  confounded  with  the  superficial 
ligament,  although  it  is  clearly  distin- 
guished from  it  by  its  inferior  insertion. 
Fixed  in  common  to  the  posterior  imprints 
of  the  first  phalanx,  these  three  fasciculi 
diverge  in  ascending  to  the  base  of  the 
sesamoids,  where  they  have  their  upper 
insertion. 

The  deep  ligament  is  constituted  by 
two  small  bands  concealed  beneath  the 
middle  ligament.  Thin,  short,  flattened 
before  and  behind,  and  intercrossed  (Fig. 
131,  B  3),  these  bands  are  fixed  to  the 
base  of  the  sesamoids  in  one  direction, 
and  in  the  other  to  the  superior  extremity 
of  the  first  phalanx,  near  the  margin  of 
its  articular  surface.  This  ligament  is 
covered  on  its  anterior  face  by  the  synovial 
membrane  of  the  articulation. 

CARPAL,     METACARPAL,     AND     INTER-PHALANGEAL 

ARTICULATIONS      OF       THE        HORSE       (POSTERO- 
LATERAL view). 
R,  Radius  ;  c,  carpus  ;  M,  metacarpus  ;  s,  navicular 

bone ;  P,  third  phalanx.     1,  Supercarpal  bone ; 

2,  its  proper  ligament  ;  3,  external   lateral  liga- 
ment   of  the    carpal    articulations    (superficial 

layei');  3,  ditto  (deep   layer);   4,  groove  for  the 

tendon  of  the  external  Hexor  of  the  metacarpus; 

5,  common    posterior    ligament    of    the    carpal 

articulations;    6,  superior  sesamoidean,  or   sus- 
pensory ligament  of  the  fetlock  ;  7,  an  originating 

branch  of  ditto  ;  8,  8,  terminal  branches  of  ditto  ; 

9,  band  given  off  by  ditto  to  the  anterior  extensor 

of  the   phalanges ;    10,   tendon   of  the    anterior 

extensor  of  the  phalanges  ;   11,  groove  formed  by 

the  posterior  face  of  the   intersesamoidean  liga- 
ment; 12,  lateral  metacarpo-phalangeal  ligament 

(superticial  layer);   12',  ditto  (deep  layer)  ;   14, 

inferior  superficial    sesamoidean    ligament ;    15, 

ditto  (deep  layer);  16.  elenoidal  fibro-cartilage  of 

the  second  phalanx  ;  17.  18,  19,  superior,  middle, 

and  inferior  bands  of  that    fibro-cartilage ;   20, 

lateral   ligament   of  the    first    inter-phalangeal 

articulation;    21.   lateral   posterior  ligament  of 

the    second    inter-phalanceal    ai'ticulation ;    22, 

anterior  lateral  ligament  of  ditto. 
16 


20» 


206  THE  ARTICULATIONS. 

e.  The  lateral  sesamoid  ligaments  are  two  thin  layers,  extending  from  the 
external  face  of  each  sesamoid  to  the  tubercle  of  insertion  on  the  side  of  the 
superior  extremity  of  the  first  phalanx  (Fig.  131,  a  2).  They  are  covered  by  the 
digital  vessels  and  nerves,  by  the  fibrous  stay  detached  from  the  suspensory  liga- 
ment to  the  anterior  extensor  tendon  of  the  phalanges,  and  by  the  supei-ficial 
fasciculus  of  the  lateral  metacarpo- phalangeal  ligament ;  they  are  covered  by 
synovial  membrane  on  their  internal  face. 

B.  The  ligaments  destined  to  unite  the  two  articular  surfaces  of  the  meta- 
cai-po-phalangeal  joint  are  four  :  tivo  lateral,  one  anterior,  and  one  posterior . 

a.  Each  lateral  ligament  comprises  two  fasciculi — a  supei-ficial  and  a  deep — 
firmly  united  by  their  adjacent  faces.  The  superficial  fasciculus  (Fig.  132,  12) 
commences  on  the  button  of  the  lateral  metacarpal  bone,  attaches  itself  to  the 
median  metacai-pal,  and  descends  vertically  to  terminate  at  the  superior  extremity 
of  the  first  phalanx.  It  covers  the  phalangeal  insertion  of  the  lateral  sesamoid 
ligament  and  the  deep  fasciculus.  The  latter,  attached  superiorly  in  the  lateral 
excavation  of  the  inferior  extremity  of  the  principal  metacarpal,  radiates  as  it 
reaches  the  sesamoid  and  the  superior  extremity  of  the  first  phalanx,  where  it  is 
fixed  by  mixing  its  fibres  with  those  of  the  lateral  sesamoid  ligament.  The  inner 
face  of  this  fasciculus  is  lined  by  the  articular  synovial  membrane  (Fig.  132, 12'). 

I.  The  anterior  ligament  (Fig.  132)  belongs  to  the  class  of  capsular  ligaments. 
It  is  a  veiy  resisting  membraniform  expansion,  which  envelops  the  anterior  face 
of  the  articulation.  Attached  by  its  upper  border  to  the  anterior  margin  of  the 
metacarpal  surface,  and  by  its  inferior  border  to  the  first  phalanx,  this  expansion 
is  confounded  at  its  sides  with  the  lateral  ligaments.  It  is  covered  by  the  extensor 
tendons  of  the  phalanges,  which  glide  on  its  surface  by  means  of  small  serous 
sacs.  Its  internal  face  adheres  throughout  its  whole  extent  to  the  synovial 
capsule. 

c.  The  posterior  ligament,^  very  appropriately  named  the  suspensory  ligament 
of  the  fetloch  (Figs.  132,  6  ;  133,  134,  4),  is  a  long  and  powerful  brace,  composed 
of  white  fibrous  tissue,  and  often  containing  fasciculi  of  fleshy  fibres  in  its  textm-e. 
Lodged  behind  the  median  metacai-pal,  and  between  the  two  lateral  metacarpal 
bones,  this  brace  is  quite  thin  at  its  origin,  but  it  soon  becomes  enlarged,  and  pre- 
serves its  great  thickness  to  the  extent  of  its  upper  fourth.  Examined  in  section, 
it  appears  to  be  formed  of  two  superposed  portions  which  are  closely  adherent  to 
each  other.  The  superficial  portion,  the  thinnest,  commences  by  three  small 
branches,  which  are  fixed  to  the  first  and  second  bones  of  the  lower  carpal  row 
(Figs.  132,  133,  5)  ;  the  deep  portion,  much  thicker,  is  attached  to  the  posterior 
face  of  the  principal  metacai"pal  for  about  ^  of  an  inch.  It  has  been 
wrongly  asserted  that  the  suspensoiy  ligament  of  the  fetlock  is  continuous  with 
the  common  posterior  ligament  of  the  cai-pus  ;  it  is,  on  the  contrary,  quite  distinct 
from  it.  The  carpal  stay  {deep  palmar  aponeurosis  of  Man)  is  alone  in  direct 
continuity  mth  the  common  posterior  ligament  of  the  cai'pus  (133,  3).  The 
suspensory  ligament  of  the  fetlock  is  bifid  at  its  inferior  extremity ;  its  two 
branches,  after  being  fixed  into  the  summits  of  the  sesamoid  bones,  give  origin  to 
two  fibrous  bands  which  pass  downwards  and  forwards  to  become  united  on  each 
side  to  the  anterior  extensor  tendon  of  the  phalanges  (Fig.  132,  9).  It  is  in  relation, 
by  its  posterior  face,  Avith  the  perforans  tendon  and  its  carpal  stay  ;  by  its  anterior 
face,  with  the  median  metacarpal  bone,  and  arteries  and  veins  ;  by  its  borders, 

'  It  coiresponds  to  the  two  muscles  which,  in  Mun,  lie  alongside  the  interosseous  meta- 
carpal muscles.     (See  Muscles  of  the  Foot.) 


ARTICULATIONS  OF  THE  ANTERIOR   LIMBS. 


207 


with  two  small  interosseous  muscles,  the  lateral  metacarpal  bones,  and  the  digital 
vessels  and  nerves. 

Synovial  membrane. — Tliis  membrane  is  prolonged  as  a  cul-de-sac  between  the 
terminal  branches  of  the  preceding  ligament.     It  is  the  distension  of  this  sac 
which  causes  the  articular  swellings  vulgarly  designated 
"  windgalls."  Fig.  133. 

Movements. — The  metacarpo-phalangeal  articulation 
permits  the  extension  and  flexion  of  the  digit,  and  some 
slight  lateral  motion  when  the  movable  osseous  segment 
is  carried  to  the  limits  of  flexion. 

In  the  Ox,  Sheep,  and  G-oat,  this  articulation  constitutes  a 
dotible  hinge,  which  resembles  the  simple  ginglymus  of  Solipeds. 

They  have  three  intersesamoid  ligaments :  two  lateral,  to  unite 
the  large  sesamoids  of  each  digit ;  and  a  median,  which  unites 
the  interual  sesamoids.  The  inferior  sesamoidean  ligamentous 
apparatus  is  far  from  showing  the  same  degree  of  development 
as  in  the  Horse.  It  is  reduced  for  each  digit  to  four  small  bands, 
which  remind  one  very  much  of  the  deep  ligament  of  the  latter 
animal,  as  it  has  been  described  by  Rigot :  two  lateral  bands  pass 
directly  from  the  sesamoids  to  the  upper  extremity  of  the  first 
phalanx ;  the  other  two,  situated  between  the  first,  intercross 
and  are  confounded  with  the  latter  by  their  extremities.  A  lateral 
tesamoid  ligament  unites  the  first  phalanx  to  the  exterual  sesamoid. 

For  each  digit  there  are  two  lateral  metacarpo-phalangeal 
ligaments— a,n  external,  analogous  to  that  of  the  Horse,  but  less 
complicated,  is  attached  by  its  inferior  extremity  to  the  first 
phalanx  only ;  the  other,  internal,  fixed  superiorly  in  the  bottom 
of  the  inter-articular  notch  of  the  metacarpal  bone,  is  inserted 
into  the  inner  face  of  the  first  phalanx  in  mixing  its  fibres  with 
those  of  the  superior  interdigital  ligament.  This  latter  is  situated 
between  the  two  first  phalanges,  and  is  composed  of  short,  inter- 
crossed fibres,  attached  to  the  imprints  which  in  part  cover  the 
internal  face  of  the  two  first  phalangeal  bones.  In  the  Sheep 
there  are  only  traces  of  this  interdigital  ligament,  and  each  internal 
metacarpal-phalangeal  gives  rise,  near  its  phalangeal  insertion,  to 
a  fibrous  branch  which  is  directed  backwards  from  the  interdigital 
Bpace,  and  is  terminated  in  the  bone  of  the  ergot  (or  posterior 
rudimentary  digit),  which  it  sustains.  The  anterior  or  capsular 
ligament,  single  as  in  Solipeds,  unites  the  two  external  lateralliga- 
ments.  The  suspensory  ligament,  single  superiorly,  is  divided  inferiorly  into  eight  branches,  two 
of  which  are  joined  to  the  periuratus  tendon,  to  form  with  it  the  double  ring  through  which  the 
two  branches  of  the  perforans  pass.  Four  other  branches,  in  pairs,  extend  to  the  summits  of 
the  sesamoids.  That  which  is  sent  to  each  external  sesamoid  gives  off,  on  the  side  of  the  first 
phalanx,  a  reinforcing  band  to  the  proper  extensor  of  the  digit.  The  two  last,  profound  and 
median,  descend  into  the  inter-articular  notch  of  the  metacarpal  bone,  after  becoming  a  single 
fasciculus ;  afterwards,  they  pass  between  two  internal  metacarpo-phalangt-al  ligaments,  and 
separate  from  each  other  in  passing  downwards  and  forwards  on  the  inner  side  of  the  first 
phalanx,  to  join  the  proper  extensor  tendon  of  each  digit. 

In  the  Pig,  Dog,  and  Cat,  for  each  metacarpo-phalangeal  there  is:  a  proper  synovial 
membrane;  an  intersesamoid  ligament;  an  inferior  sesamoid  ligament  composed  of  two  cross- 
bands;  two  small  lateral  sesamoid  ligaments;  two  lateral  metacarpo-phalangeal  ligaments, 
attached  inferiorly  to  the  first  phalanx  and  the  sesamoids ;  an  anterior  capsular  ligament,  in 
the  centre  of  which  is  found  a  small  bony  nucleus — a  kind  of  anterior  sesamoid— over  which 
glides  one  of  the  branches  of  the  common  extensor  of  the  digits.  The  suspensory  ligament  is 
replaced  by  real  palmar  interosseous  muscles  (see  the  Muscles  of  the  Anterior  Foot).  Some 
fibres  situated  between  the  first  phalanges  in  the  great  digits  of  the  Pig,  resemble  the  superior 
interdigital  ligament  of  the  Ox. 

In  Man,  the  cavity  in  the  upper  extremity  of  the  first  phalanx  is  completed  by  a  glenoid 


SECTION  OF  THE  INFERIOR 
ROW  OF  CARPAL  BONES, 
THE  METACARPAL,  AND 
THE  SUSPENSORY  LIGA- 
MENT OF  THE  FETLOCK. 

1,  Os  magnum  ;  2,  common 
posterior  ligament  of  the 
carpus  ;  3,  stay,  or  band 
for  tlie  perforans  tendon  , 
4,  suspensory  ligament  of 
the  fetlock  ;  5,  its  super- 
ficial layer ;  6,  its  deep 
fasciculus ;  7,  principal 
metacarpal  bone. 


TEE  ARTICULATIONS. 


ligament.  The  prenoid  ligaments  of  the  four  first  digits  are  united  to  each  other  by  a  trans- 
verse ligament  of  the  metacarpus.    The  articulations  are  cousolidated  by  two  lateral  ligaments. 

The  metaciirpo-plialaiigeal  articulations  allow  flexion  and  ex- 
Fig.  134.  tension  movements,  as  well  as  those  of  abduction  and  adduction; 

but  the  latter  are  limited  by  the  lateral  ligaments. 


M 


rosterior  view  of  the 
metacarpo-phalangeal 
and  inter-phalangeal 
articulations  (right 
limb). 

1,  3,  Outer  and  inner 
rudimentary  metatarsal 
bones  ;  2,  perforans  tea- 
don  and  its  check  liga- 
ment ;  4,  suspensory  liga- 
ment ;  5,  gliding  surface 
or  sheath  for  the  flexor 
tendons,  f'rmed  by  the 
posterior  face  of  the  sesa- 
moid bones,  and  interse- 
samoid.  transverse,  and 
annular  ligaments;  6, 
section  of  lateral  sesamoid 
ligament ;  7,  lateral  fasci- 
culus of  the  middle  infer 
lateral  ligament  of  the  fir 
of  the  perforatus  tendon; 
surface  of  navicular  bone; 
14,  perforatus  tendon,   15, 


7.  Abticulation  of  the  Fibst  with  the  Second 
Phalanx,  or  First  Interphalangeal  Articulation. 

(Preparation. — Kemove  the  extensor  tendon ;  throw  open  the 
metaearpo-pnalangeal  sheath,  and  turn  down  the  flexor  tendons.) 

This  is  an  imperfect  hinge-joint. 

Articular  surfaces. — On  the  inferior  extremity  of  the 
first  phalanx  are  two  lateral  condyles,  separated  by  a 
groove.  On  the  superior  surface  of  the  second  phalanx 
are  two  glenoid  cavities,  and  an  antero-posterior  ridge. 

The  latter  surface  is  completed  behind  by  a  glenoidal 
fihro-cartilage,  very  dense  and  thick  (Fig.  132, 16),  which 
also  acts  as  a  ligament.  It  is  attached,  in  one  direction, 
to  the  second  phalanx,  between  the  superior  articular 
surface  and  the  kind  of  fixed  sesamoid  which  margins  it 
behind  ;  in  the  other,  it  is  inserted  into  the  first  phalanx 
by  means  of  six  fibrous  bands  (Fig.  135,  4,  5,  6)  :  two 
superior,  which  embrace  the  inferior,  middle,  and  super- 
ficial sesamoid  ligaments  ;  two  middle,  and  two  inferior, 
which  extend  to  the  sides  of  the  inferior  extremity  of 
the  first  phalanx.  This  fibro-cartilage  is  moulded,  in 
front,  to  the  articular  surface  of  the  latter  bone,  and 
forms,  by  its  posterior  face,  a  gliding  surface  for  the 
perforans  tendon  (Figs.  132,  16  ;  134,  5).  It  is  con- 
founded, laterally,  with  the  two  branches  of  the  per- 
foratus, and  receives,  in  the  middle  of  its  superior  border, 
the  insertion  of  the  inferior  superficial  sesamoid  liga- 
ment. 

Mode  of  union. — Two  lateral  ligaments  (Fig.  135, 
7),  to  which  are  added,  behind,  the  fibro-cartilage  just 
described,  and  in  front  the  tendon  of  the  anterior  extensor 
of  the  phalanges.  These  ligaments  are  large  and  thick, 
and,  passing  obliquely  downwards  and  backwards,  are 
inserted,  superiorly,  into  the  lateral  tubercles  of  the 
inferior  extremity  of  the  first  phalanx.  They  are  at- 
tached, beneath,  to  the  sides  of  the  second  phalanx. 
Their  most  inferior  fibres  are  even  prolonged  below  that 
point  to  reach  the  extremities  of  the  navicular  bone,  and 
constitute  the  posterior  lateral  ligaments  of  the  pedal 
articulation. 

Synovicd  membrane. — This  covers  the  tendon  of  the 

•ior  sesamoid  ligament;  8,  inferior  superficial  sesamoid  ligament ;  9, 
st  interphalangeal  articulation  ;    10,   section  of  the  terminal   branch 

11,  section  of  the  lateral  cartilage  of  the  foot;  12,  postero-inferior 
13,  section  of  lateral  cartilage,  plantar  cushion,  and  wing  of  pedal  bone; 

perforans  tendon. 


ARTICULATIONS  OF  THE  ANTERIOR  LIMBS.  209 

anterior  extensor  of  the  phalanges,  the  lateral  ligaments,  and  the  glenoid  fibro- 
cartilage.  Behind,  it  forms  a  cul-de-sac,  which  extends  between  the  latter  and  the 
posterior  face  of  the  first  phalanx  (Fig.  137). 

Movements. — This  imperfect  hinge  is  the  seat  of  two  principal  movements : 
extension  and  flexion.  It  also  allows  the  second  phalanx  to  pivot  on  the  first,  and 
permits  some  lateral  movements. 

In  the  Ox,  Sheep,  and  Goat,  the  glenoid  fibro-cartilage  is  confounded  with  the  perforatus 
tendon,  and  is  only  attached  to  the  first  pliahmx  by  two  lateral  bands.  The  internal  lateral 
ligament  comprises  two  fasciculi  :  one,  very  short,  which  terminates  in  the  st-coml  phalanx ; 
and  another,  very  long,  descending  to  the  internal  face  of  the  third  phalanx.  The  external  is 
very  thin,  and  is  also  prolonged  to  the  terminal  phalanx ;  so  that  the  two  last  inteiphalangeal 
articuhitions  of  each  digit  are  fixed  by  two  common  lateral  li'j;aments  which  correspond  exactly, 
by  their  position  and  inferior  attachments,  to  the  anterior  lateral  ligaments  of  the  pedal  joint 
of  Solipeds. 

In  the  Dog  and  Cat,  the  glenoid  cartilage,  also  confounded  by  its  posterior  face  with  the 
perforatus  tendon,  only  adheres  to  the  first  phalanx  by  some  cellular  bands.  The  two  lateral 
ligaments  pass  from  the  inferior  extremity  of  the  first  phalanx  to  the  superior  extremity  of  the 
second. 

In  the  Pig,  there  is  somewhat  the  same  arrangement  as  in  Carnivora.  The  external 
lateral  ligament  is,  nevertheless,  more  like  that  of  the  Horse,  in  its  most  anterior  fasciculi  being 
prolonged  lo  the  external  extremity  of  the  navicular  bone. 

8.  Aeticulation    of    the    Second    Phalanx    with    the    Third,    Second 
Interphalangeal  Articulation,  or  Articulation  op  the  Foot. 

Preparation. — Eemove  the  hoof  according  to  the  directions  given  hereafter,  when  treating  of 
the  muscles  of  the  forearm ;  then  the  plantar  cushion,  the  flexor  tendons,  and  one  of  the  lateral 
cartilages.     A  section  like  that  shown  in  Fig.  137  is  useful  to  show  the  relations  between  the         % 
synovial  capsule  of  this  joint  and  the  bursae,  behind  the  second  phalanx. 

To  form  this  imperfect  hinge-joint,  the  second  phalanx  is  opposed  to  the  tliird, 
and  to  the  navicular  bone. 

Articular  surfaces. — On  the  inferior  face  of  the  second  phalanx  there  are  two 
lateral  condyles  and  a  median  groove.  On  the  superior  face  of  the  third  phalanx 
and  the  navicular  bone,  are  two  glenoid  cavities  separated  by  an  antero-posterior 
ridge.  The  two  bones  which  form  tliis  last  surface,  articulate  with  each  other  by 
arthrodia  ;  the  navicular  bone  presents  for  tliis  purpose  an  elongated  facet  on  its 
anterior  border  ;  the  os  pedis  also  offers  an  analogous  facet  on  the  posterior  contour 
of  the  principal  articular  surface. 

Mode  of  union. — Five  ligaments  :  a  single  interosseous  one,  which  joins  the 
navicular  to  the  pedal  bone  ;  and  four  lateral  bones,  distinguished  as  anterior  and 
posterior. 

a.  Interosseous  ligament  (Fig.  136,  2). — This  is  formed  of  very  short  fibres, 
which  are  inserted,  behind,  into  the  anterior  groove  of  the  navicular  bone  ;  and 
in  front,  into  the  posterior  border  and  inferior  face  of  the  third  phalanx.  This 
ligament  is  lined,  on  its  superior  surface,  by  the  synovial  membrane,  and  on  its 
inferior  face  is  covered  by  the  navicular  sheath. 

h.  Anterior  lateral  ligaments  (Figs.  132,  22  ;  135,  9).— These  are  two  thick, 
short,  and  wide  fasciculi,  attached  by  their  superior  extremities  to  the  lateral 
imprints  of  the  second  phalanx,  and  by  their  inferior  extremities  into  the  two 
cavities  at  the  base  of  the  pyramidal  eminence  of  the  os  pedis.  Each  ligament  is 
partly  covered  by  the  complementary  fibro-cartilage  of  that  bone,  and  appears  to 
form  a  portion  of  it.    Its  anterior  border  is  continuous  with  the  common  extensor 


210 


TEE  ARTICULATIONS. 


tendon  of  the  phalanges  ;  its  internal  face  is  covered  by  the  synovial  membrane, 
which  adheres  closely  to  it. 

c.  Posterior  lateral  ligaments  (Figs.  132,  21  ;  135,  8). — These  have  been 
already  noticed.  Each  is  composed  of  the  lowermost  fibres  of  the  lateral  ligament 
of  the  first  interphalangeal  articulation  ;  these  fibres,  after  being  attached  to  the 
?econd  phalanx,  unite  into  a  sensibly  elastic  fibrous  cord,  which  is  chiefly  fixed 


Fig.  1^5. 


M  E  r ATARSO  -  PHALANGEAL 
AND  INTER-PHALANGEAL 
ARTICULATIONS  OF  THE 
HORSE. 

These  are  almost  the  same 
as  in  the  anterior  limb. 
1,  Superficial  layer  of  the 
external  lateral  ligament 
of  the  metatarso-phalan- 
geal  articulation  ;  2,  sesa- 
moid branch  of  the  deep 
layer;  3, phalangeal  branch 
of  the  same ;  4,  superior 
branch  of  the  glenoidal 
fibro-cartilage;  5,  middle 
branch  of  ditto;  6,  inferior 
branch  of  ditto  ;  7,  lateral 
ligament  of  the  first  inter- 
phalangeal articulation ;  8, 
posterior  lateral  ligament 
of  the  pedal  articulation ; 
9, anteiior  lateral  ligament 
of  ditto. 


ARTICULATION  OF  THE  FOOT  (INFERIOR  FACE). 

P,  Inferior  face  of  the  third  phalanx.  S,  Infe- 
rior face  of  the  navicular  bone.  1,  Semilu- 
nar crest ;  2,  interosseous  ligament. 


into  the  extremity  and  superior  border  of  the  navicular 
bone,  where  the  Ugaments  join  each  other,  and  in  this 
way  form  a  kind  of  complementary  cushion  that  in- 
creases the  navicular  articular  surface.  It  also  sends 
off  a  short  fasciculus  to  the  retrossal  process,  and  a 
small  band  to  the  internal  face  of  the  lateral  fibro- 
cartilage.  Partly  concealed  by  the  latter  and  the  plantar 
cushion,  this  ligament  is  covered  inwardly  by  the  articu- 
lar synovial  membrane. 

Synovial  memlrane. — This  descends  below  the  facets 
which  unite  the  navicular  to  the  pedal  bone.  It  offers, 
posteriorly,  a  vast  cul-de-sac  which  reaches  the  posterior 
face  of  the  second  phalanx,  and  hes  against  the  two 
sesamoidean  bursse  (Fig.  137, 13).  It  also  forms  another 
much  smaller,  by  being  prolonged  between  the  two  lateral 
ligaments  of  the  same  side.  This  is  very  often  distended, 
and  it  is  liable  to  be  opened  in  the  operation  for  diseased  lateral  cartilages. 
Movements. — The  same  as  those  of  the  first  interphalangeal  articulation. 

In  the  Sheep  are  found  :  1.  An  interosseous  ligament  to  unite  the  navicular  bone  to  the 
third  phalanx.  2.  Two  anterior  lateral  ligaments  commencing:,  as  already  stated,  at  the  first 
phalanx.  3.  Two  lateral  posterior  ligaments,  passina:  to  the  posterior  face  of  the  second  phalanx 
and  the  navicular  bone  (the  internal  is  yellow  and  elastic).  4.  A  single,  anterior,  elastic  liga- 
ment, attached  above  to  the  superior  extremity  of  the  second  phalanx,  and  fixed  below  into  the 
third,  between  the  insertion  of  the  common  extensor  of  the  digits  and  that  of  the  internal 
anterior  lateral  ligament;  an  inferior  interdigital  ligament,  situated  between  the  ungueal 
phalanges,  whose  separation  from  each  other  it  limits  This  ligament  is  compose<l  of  parallel 
fibres,  whicii  extend  transversely  from  the  one  navicular  bone  to  the  other,  and  is  covered  on 


ARTICULATIONS  OF  THE  ANTERIOR  LIMBS. 


211 


its  inferior  face  by  the  skin  of  the  interdigital  Bpace.     Its  upper  face  is  in  contact  with  an 
adipose  cushion. 

In  the  Ox,  the  external  anterior  lateral  ligament,  wide  and  expanding,  is  almost  entirely 
covered  by  the  long  branch  of  the  proper  extensor  of  the  digit,  to  which  it  is  intimately 
adherent.  The  interdigital  ligament  has  a  much  more  complicated  character  than  that  of  the 
Sheep.  It  is  formed  of  fibres  intercrossed  on  the  median  line,  and  divided  at  its  extremities 
into  two  fasciculi :  a  superior  passes  over  the  perforans  tendon,  to  which  it  serves  as  a  restrain- 
ing band,  and  is  fixed  to  the  outside  of  the  inferior  extremity  of  the  first  phalanx,  after  con- 
tracting very  close  adhesions  with  a  strong  fibrous  web  which  descends  from  the  posterior 
metacarpal  region,  and  which  will  be  more  fully  noticed  when  describing  the  muscles;  an 
inferior,  shorter  than  the  preceding,  attached  to  the  internal  extremity  of  the  navicular  bone 
and  the  internal  face  of  the  third  phalanx,  becoming  confounded  with  the  perforans  tendon, 
the  plantar  cushion,  and  the  dermis  of  the  keratogenous  membrane. 


Fig.  138. 


Fig.  137. 


JffJO       i 

LONGITTIDrNAL  AND  VERTICAL  SECTION  OF  THE 
DIGITAL  REGION  IN  THE  HORSE,  SHOWING  THE 
ARRANGEMENT  OF  THE  ARTICULAR  AND  TENDI- 
NOUS SYNOVIAL  APPARATUS. 

1,  First  phalanx ;  2,  second  phalanx ;  3,  third  pha- 
lanx ;  4,  semilunar  sinus  of  ditto ;  5,  navicular 
bone ;  6,  tendon  of  the  anterior  extensor  of  the 
phalanges ;  7,  its  insertion  into  third  phalanx  ;  8, 
tendon  of  the  perforatus ;  9,  ditto  perforans  ;  10, 
its  insertion  into  the  third  phalanx;  11,  inferior 
sesamoid  ligaments ;  12,  posterior  ctd-de-sac  of 
the  first  synovial  interphalangeal  capsule;  13, 
ditto  of  second  ;  14,  infeiior  cul-de-sac  of  the 
sesamoid  bursa;  15,  superior  ditto  of  navicular 
bursa  ;  16,  inferior  ditto  of  same  ;  17,  station  of 
the  coronary  cushion;  18,  ditto  of  plantar 
cushion. 


TENDONS  AND  LIGAMENTS  OF 
THE  POSTERIOR  FACE  OF 
THE  DIGITAL  REGION  OF 
THE  OX. 

1,  Perforatus  tendon  ;  2,  2, 
its  terminal  tendons  ;   3, 

3,  theii-    bifurcation ;    4, 

4,  perforans  tendon  ;  6,  6, 
superior  branches  of  the 
inferior  interdigital  liga- 
ment attached  to  the  first 
phalanx  ;  7,  inferior  inter- 
digital ligament ;  8,  8, 
suspensory  ligament  of 
the  fetlock. 


In  the  Pig,  for  the  maintenance  of  the  second  interphalangeal  articulation,  there  are: 
1.  Two  lateral  ligaments,  carried  from  the  lateral  faces  of  the  second  phalanx  to  the  external 
and  internal  faces  of  the  third.  2.  A  third  ligament,  exactly  resembling  one  of  the  posterior 
lateral  ligaments  of  the  pedal  articulation  of  the  Horse;  this  ligament  descends  from  the 
inferior  extremity  of  the  first  phalanx  to  the  internal  extremity  of  the  navicular  bone.  Its 
analogue  of  the  inner  side  appears  to  be  altogether  absent ;  but  in  the  large  digits  there  is  an 
anterior  yellow  elastic  ligament  like  that  of  Ruminants. 

In  the  Dog,  the  two  last  phalanges  are  united  by  two  lateral  ligaments,  very  simply 
arranged.  A  third  ligament,  formed  of  elastic  tissue,  divided  into  two  lateral  portions,  and 
situated  in  front  of  the  articulation,  plays  the  part  of  a  spring,  which  mechanically  produces 
the  retraction  of  the  claw  when  the  flexor  muscles  cease  to  contract.  In  the  Cat,  this  yellow 
ligament  is  very  strong;  and  this  animal  also  exhibits  a  very  striking  obliquity  of  the  articular 


212  TEE  ARTICULATIONS. 

pulleys  by  which  the  two  phalanges  correspond  :  an  arrangement  that  permits  the  claw  to  be 
lodo'ed  between  two  digits  wlien  they  are  raised,  and  tlius  favour  its  retraction. 

Tlie  second  iuteiphalangeal  articulation  of  the  Dog  and  Cat  is  also  distinguished  by  another 
essential  arrangement.  The  articular  surface  of  the  third  phalanx  is  completed  by  a  glenoid 
fibrocartiiage  analogous  to  that  of  the  first  articulation,  but  much  thicker.  This  fibro-cartilage 
(see  Muscles  of  the  Hand)  is  fixed  into  the  posterior  projection  of  the  third  phalanx,  and 
serves,  by  its  inferior  face,  as  a  pulley  for  the  perforaus  tendon  and,  with  the  projection  just 
named,  plays  the  part  of  the  navicular  bone  in  other  animals. 

The  interphalangeal  articulations  of  Man  are  formed  on  the  same  plan  as  the  metacarpo- 
phalangeal articulations  They  are  consolidated  by  a  glenoid  and  lateral  ligaments,  and 
possess  only  the  two  movements  oi  flexion  and  extension. 

Article  V. — Articulations  of  the  Posterior  Limbs. 
1.  Articulations  of  the  Pelvis. 

{Preparation.— These  ligaments  are  all  exposed  to  view  by  carefully  removing  the  soft  parts 
connected  with  the  sacrum  and  coxae.) 

A.  Sacro-iliac  Articulation  (Figs.  139,  140).— This  is  a  pair  articulation 
which  establishes  the  union  of  the  posterior  limb  with  the  spine,  and  is  formed 
by  the  sacrum  and  coxa.     It  belongs  to  the  arthi'odial  class. 

Articular  surfaces. — On  the  sacrum,  the  irregular  diarthrodial  facet  named 
the  "  auricular,"  cut  on  the  sides  and  near  the  base  of  the  bone.  For  the  coxa, 
the  analogous  facet  on  the  internal  face  of  the  ilium. 

3fode  of  union. — By  four  ligaments,  which,  after  the  example  of  Rigot,  we 
will  name  sacro-iliac,  superior  ilio-sacral,  inferior  ilio-sacral,  and  the  sacro-sciatic. 
The  first  is  situated  immediately  around  the  articular  surfaces,  and  the  others  are 
only  in  mediate  relations  with  them. 

a.  Sacro-iliac  ligament  (Fig.  140,  1). — This  is  composed  of  thick  fibrous 
fasciculi,  which  envelop  the  whole  articulation  in  being  firmly  attached  by  their 
extremities,  to  the  imprints  around  the  diarthrodial  facets.  The  inferior  moiety 
of  this  ligament  is  covered  by  the  iliacus  muscle.  Its  posterior  half  ^  is  much 
stronger,  is  hidden  by  the  ilium,  and  gives  attachment  to  the  longissimus  dorsi 
muscle. 

h.  Superior  ilio-sacral  ligament  (Fig.  139,  13). — A  thick  and  short  funicle, 
which,  rising  from  the  internal  angle  of  the  ilium,  is  carried  backwards  to  be 
fixed  to  the  sacral  spine,  where  its  fibres  are  confounded  with  those  of  the  super- 
spinous  dorso-lumbar  ligament. 

c.  Inferior  ilio-sacral  ligament  (139,  14).— This  is  very  resisting,  triangular, 
membranous  band,  formed  of  parallel  fibres  passing  obliquely  downwards  and 
backwards.  It  is  attached,  by  its  anterior  margin,  to  the  upper  half  of  the 
sciatic  border  and  the  internal  angle  of  the  ilium,  in  becoming  confounded  with 
the  preceding  ligament.  Its  inferior  margin  is  inserted  into  the  rugged  lip  which 
borders  the  sacrum  laterally.  Its  posterior  border  is  united  to  the  aponeurosis 
covering  the  coccygeal  muscles,  and  its  external  face  is  in  contact  with  the 
principal  gluteal  and  the  long  vastus  muscles  ;  while  the  internal  lies  against  the 
lateral  sacro-coccygeal  muscle. 

d.  Sacro-sciatic  or  ischiatic  ligament  (Fig.  140,  2).— This  is  a  vast  membranous 
expansion  situated  on  the  side  of  the  pelvis,  between  the  sacrum  and  the  coxa. 
It  serves  more  as  a  means  for  enclosing  this  portion  of  the  pelvic  cavity,  than  to 
assure  the  solidity  of  the  sacro-iliac  articulation.     Its  form  is  irregularly  quadri- 

'  It  represents  the  interosseous  sacro-iliac  ligament  of  Man.  The  inferior  half  corresponds 
to  the  anterior  sacro-iliac  ligament. 


ARTICULATIONS  OF  TEE  POSTERIOR  LIMBS. 


213 


lateral,  and  permits  its  circumference  to  be  divided  into  four  borders  :  a  suj^erior, 
attached  to  the  rugged  lateral  ridge  of  the  sacrum  ;  an  inferior,  fixed  to  the  supra- 
cotyloid  ridge,  as  well  as  the  ischial  tuberosity,  and  forming  by  the  portion 
comprised  between  these  two  insertions,  with  the  small  ischiatic  notch,  the  opening 
by  which  the  internal  obturator  and  pyramidalis  muscles  leave  the  pelvis  ;  an 
anterior,  imperfectly  limited,  along  with  the  great  sciatic  notch,  circumscribes 
the  opening  through  which  the  ghiteal  vessels  and  nerves,  and  the  sciatic  nerves 
pass  ;  a  posterior,  doubled  in  the  form  of  two  layers  which  embrace  the  semi- 
membranosus muscle,  and  is  confounded  superiorly  with  the  aponeurosis  envelop- 
ing the  coccygeal  muscles.  The  external  face  of  this  ligament  is  traversed  by  the 
sciatic  nerves,  and  is  covered  by  the  long  vastus  and  the  semitendinosus  muscles, 
which  derive  numerous  insertions  from  it.     Its  internal  face  is  covered,  in  front, 


SACRO-ILIAC  AND  COXO-FEMORAL   ARTICULATIONS,  WITH  THEIR  SURROUNDIHG  MUSCLES. 

11,  Sacro-sciatic  ligament;  12,  great  sciatic  notch;  13,  superior  ilio-sacral  ligament;  14,  inferior 
ilio-sacral  ligament. 


by  the  peritoneum,  and,  posteriorly,  is  in  contact  with  the  ischio-coccygeal  and 
ischio-anal  muscles,  to  which  it  gives  attachment. 

Si/novial  memhrane. — This  lines  the  sacro-iliac  ligament,  but  only  furnishes  a 
small  quantity  of  synovia. 

MovemenU. — The  two  sacro-iliac  articulations,  being  the  centres  towards  which 
all  the  propulsive  efforts  communicated  to  the  trunk  by  the  posterior  limbs  con- 
verge, do  not  offer  much  mobility,  as  that  would  oppose  the  integral  trans- 
mission of  the  propulsion.  So  that  they  permit  only  a  very  restricted  gliding  of 
the  articular  surfaces  ;  while  the  union  of  the  sacrum  and  coxa  by  diarthrosis, 
appears  to  be  exclusively  designed  to  prevent  the  fractures  to  which  these  bones 
would  be  incessantly  exposed,  if  they  were  fixed  together  in  a  more  intimate 
manner. 

B.  Articulation  of  the  two  Cox^,  or  Ischio-pubic  Symphysis. — The 
two  coxffi  are  united  to  each  other  throughout  the  whole  extent  of  the  inner  border 
of  the  pubis  and  the  ischial  bones.  In  youth,  this  is  a  veritable  amphiarthrosis, 
fixed  by  an  interosseous  cartilage  and  bundles  of  peripheral  fibres. 

The  cartilage  is  solidly  fixed  to  the  small  rugged  eminences  which  cover  the 
adjacent  articular  surfaces,  and  becomes  ossified,  like  the  sutural  cartilages,  as 


214 


THE  ARTICULATIONS. 


the  animal  advances  in  age.  In  adult  Solipeds  the  coxae  are  constantly  tused  to 
each  other. 

The  peripheral  fibrous  fasciculi  extend  transversely  from  one  bone  to  the 
other,  above  and  below  the  symphysis  ;  those  on  the  inferior  face  are  incom- 
parably stronger  and  more  abundant  than  the  others. 

The  movements  of  this  articulation  are  most  restricted,  and  depend  solely 
upon  the  elasticity  of  the  interosseous  cartilage.     They  cease  after  its  ossification. 

The  fusion  of  the  two  coxsb  proceeds  very  slowly  in  the  female  of  the  Cat,  Dog,  Pig,  Ox, 
Sheep,  and  Goat  species. 


2.    COXO-FEMORAL    ARTICULATION  (Fig.  140). 

(Preparation. — Remove  the  muscles  surrounding  the  articulation.  To  view  the  interior, 
divide  the  capsular  ligament  by  a  circular  incision.) 

This  is  an  enarfchrosis,  formed  by  the  reception  of  the  head  of  the  femur  into 
the  cotyloid  cavity  of  the  coxa. 

Articular  surfaces. — As  already  shown,  the  cotyloid  cavity  represents  the 

segment  of  a  hollow  sphere, 
deeply  notched  on  the  inner 
side,  and  provided  at  the 
bottom  with  a  wide  depres- 
sion, the  internal  moiety  of 
which  is  destined  for  the 
insertion  of  one  of  the  inter- 
osseous ligaments,  wliile  the 
external  half  plays  the  part 
of  a  synovial  fossa.  This 
depression  is  not  covered  by 
cartilage,  and  communicates 
by  the  internal  notch  with 
the  inferior  furrow  on  the 
pubis.  The  Up  of  the  cotyloid 
cavity  is  covered  by  a  com- 
plementary fibro-cartilage — 
the  cotyloid  ligament.  This 
fibro-cartilage  is  not  inter- 
rupted at  the  notch  just 
mentioned,  but  passes  over  it, 
forming  a  remarkable  band 
(Fig.  140,  5)  that  converts 
it  into  a  foramen,  through 
which  pass  the  pubio-  or  ilio- 
femoral ligament  and  the 
vessels  of  the  articulation. 
Fixed  by  its  adherent  border 
to  the  margin  of  the  cotyloid 
cavity,  this  ligament  is  lined 
It  is  thickest  in  front  and 


sacro-iliac  and  coxo-femoral  articulations,  with  the 
small  deep  muscles  surrounding  the  latter  (inferior 
surface). 

1,  Sacro-iliac  ligament;  2,  sacro-sciatic  ligament;  3,  great 
sciatic  notch  ;  4,  anterior  portion  of  the  capsular  ligament 
of  the  coxo-femoral  articulation ;  5,  internal  band  of  the 
cotyloid  ligament ;  6,  coxo-femoral  ligament ;  7,  pubio- 
femoral  ligament ;  8,  its  insertion  into  the  femui-. 


by  synovial  membrane  on  its  faces  and  free  border, 
within. 

With  regard  to  the  head  of  the  femur,  it  will  be  remembered  that  it  is  exactly 


ARTICULATIONS  OF   THE  POSTERIOR  LIMBS.  215 

moulded  to  the  cavity,  and,  like  it,  is  excavated  by  a  nigged  fossa  which  is  entirely 
occwpied  by  the  insertion  of  the  interarticular  Ligaments. 

llode  of  union. — This  joint  is  maintained  by  a  peripheral  capsule,  and  by  an 
interarticular  band  constituting  the  coxo-femoral  ligament. 

a.  Capsular  ligament  (Fig.  140,  4). — This  is  a  membranous  sac,  like  that  of 
the  scapulo-humeral  articulation,  embracing  the  head  of  the  femur  by  its  inferior 
opening,  and  attached  by  its  opposite  border  to  the  margin  of  the  cotyloid  cavity 
and  its  surrounding  fibro-cartilage.  This  Ugament  is  composed  of  intercrossed 
fibres,  and  is  strengthened  in  front  by  an  oblique  fasciculus  which  descends  to  the 
body  of  the  femur,  along  with  the  crureus  muscle,  near  which  it  is  fixed.  Its 
internal  face  is  covered  by  the  articular  synovial  membrane,  and  its  external  face 
is  in  contact,  through  the  medium  of  adipose  cushions,  with  :  in  front,  the  crureus 
and  the  rectus  femoris  ;  behind,  the  gemini,  the  internal  obturator,  and  the 
pyramidalis  muscles  ;  outwards  and  upwards,  the  small  gluteal  muscle ;  within 
and  below,  the  external  obturator. 

h.  Coxo-femoral  ligament  {ligammtum  teres.  Fig.  140,  6). — A  thick  and  short 
funicle  of  a  triangular  shape,  deeply  situated  between  the  two  bony  surfaces,  which 
it  cannot,  notwithstanding  its  shortness,  maintain  exactly  in  contact  without  the 
other  muscular  or  ligamentous  stiiictures  enveloping  the  articulation.  In  Solipeds, 
it  is  divided  into  two  portions — a  cotyloid  and  a  puhic.  The  cotyloid  portion  is 
short  and  entirely  concealed  in  the  interior  of  the  articulation  (Fig.  140,  6).  Its 
upper  insertion  occupies  the  internal  moiety  of  the  bottom  of  the  cotyloid  cavity ; 
and  its  inferior  extremity  is  fixed  into  the  rough  fossa  in  the  head  of  the  femur. 
It  is  enveloped  by  the  synovial  membrane, 

T\iQ  puhic  portion  (Fig.  140,  7,  8)  arises,  like  the  preceding,  from  the  fossette 
in  the  head  of  the  femur,  and,  passing  upwards  and  outwards,  enters  the  internal 
notch  of  the  cotyloid  cavity,  is  inflected  downwards  on  the  fibrous  band  Avhich 
converts  that  notch  into  a  foramen,  and  is  at  last  lodged  in  the  inferior  fuiTow  on 
the  pubis,  becoming  confounded  with  the  prepubic  tendon  of  the  abdominal 
muscles,  at  the  anterior  border  of  the  pubis.  Longer  and  stronger  tlian  the  cotyloid 
portion,  this  fasciculus  is  included,  in  its  pubic  part,  between  the  two  branches  of 
the  pectineus  ;  its  interarticular  part  is  covered  by  synovial  membrane. 

Synovicd  membrane. — This  membrane  is  very  extensive  ;  it  lines  the  intemal 
face  of  the  capsular  and  cotyloid  ligaments,  and  is  reflected  on  the  interarticular 
ligaments,  to  form  around  them  a  serous  vaginal  covering.  It  is  even  prolonged 
into  the  synovial  fossa  occupying  the  centre  of  the  cotyloid  cavity. 

Movements. — The  coxo-femoral  articulation  is  one  of  the  joints  which  are 
endowed  with  the  most  varied  and  extensive  movements.  It  permits  the  flexion, 
extension,  ahduction,  adduction,  circumduction,  and  rotation  of  the  thigh  on  the 
pelvis.  The  mechanism  of  these  movements  is  so  simple,  that  they  need  no 
particular  consideration.- 

The  domesticated  animals  other  than  Solipeds,  are  distinguished  by  the  com- 
plete absence  of  the  pubio-femoral  Ligament ;  so  that  in  them  the  movements  of 
abduction,  which  are  limited  in  Solipeds  by  the  tension  of  this  ligament,  are  much 
more  extensive  ;  and  it  is  the  absence  of  the  ligament  in  question  which  explains 
the  facility  with  which  the  larger  Ruminants  are  enabled  to  strike  sideways — a 
movement  known  as  a  "  cow's  kick." 

In  Man,  the  head  of  the  femur  is  more  detached  than  in  the  domesticated  animals,  and 
the  cotyloid  cavity,  encircled  by  the  cotyloid  ligament,  is  deeper.  The  femur  is  united  to  the 
coxa:  1.  By  a  capsular  ligament.     2.  By  a  triangular  ligament,  fixed  above,  to  the  cotyloid 


216  THE  ABTICVLATIONS. 

ligament  at  the  notch,  and  below,  into  the  depression  in  the  head  of  tlie  femur.  Also,  as  the 
brothers  Weber  have  shown,  the  atmospheric  pressure  is  a  powerful  adjuuct  to  tliese  means 
of  union. 

The  coxo-femoral  articulation  of  Man  permits  more  extensive  movements  than  that  of 
animals,  and  especially  abduction  and  adduction,  which  can  be  carried  to  90  degrees. 

3.  Femoro-tibial  Articulation  (Fig.  141). ^ 

Preparation. — Remove  the  soft  parts  surrounding  the  articulation,  taking  care  not  to  wound 
the  synovial  membrane.  To  expose  the  crucial  ligaments,  make  au  antero-posterior  vertical 
section  of  the  femur  in  such  a  way  as  to  separate  the  condyles. 

This  is  the  most  comphcated  joint  in  the  body,  and  is  formed  by  the  union  of 
the  femur  with  two  of  the  thigh-bones — the  tibia  and  patella.  It  represents  an 
imperfect  hinge-joint. 

Artuular  surfaces. — To  form  this  articulation,  the  femur  opposes  its  two  con- 
dyles to  the  wide,  conve.K,  and  undulated  facets  on  the  superior  face  of  the  lateral 
tuberosities  of  the  tibia,  and  its  articular  pulley  to  the  posterior  face  of  the  patella. 

The  femoral  faces  have  already  been  described  in  detail  (p.  137)  ;  but  it  may 
be  repeated  that  the  two  condyles,  placed  side  by  side,  are  elongated  in  an  antero- 
posterior direction,  and  are  separated  by  a  non-articular  notch  called  the  inter- 
condyloid  ;  also,  that  the  femoral  trochlea,  situated  in  front  of  these  two  condyles, 
appears  to  continue  the  preceding  notch,  and  that  its  internal  border  is  much  more 
elevated  than  the  external — an  arrangement  which  explains  why  it  is  so  difficult, 
if  not  impossible,  for  the  patella  to  be  dislocated  inwards. 

The  tihial  facets  ascend  on  each  side  to  the  lateral  faces  of  the  tibial  spine. 
They  are  separated  from  one  another  by  the  antero-posterior  groove  cut  on  the 
summit  of  that  bone,  and  by  the  fossae  of  insertion  situated  at  its  base  before  and 
behind.  The  external  facet,  wider  than  the  internal,  is  devoted  in  part  to  the 
gliding  of  the  originating  tendon  of  the  popliteal  muscle. 

The  patellar  surface,  moulded  on  the  femoral  pulley,  fits  it  in  an  imperfect 
manner.  It  is  bordered,  outwardly,  by  a  small  fibro-cartilaginous  ring,  which  is 
united  to  the  fibrous  capsule  of  the  femoro-patellar  ariiculation  (Fig.  141,  1). 
Inwardly,  it  is  completed  by  the  insertion  of  the  internal  patellar  ligament,  to  be 
noticed  immediately. 

Tnterarticular  nieniscii  {semilunar  fihro-cartUages)  (Figs.  141,  a  1,  2,  3,  4  ; 
and  142,  5,  G,  7,  8). — By  this  designation  are  known  the  two  fibro-cartilages 
interposed  between  the  condyles  of  the  femm-  and  the  tibial  facets,  to  assure  their 
coaptation.  They  are  crescent-shaped  bodies,  and  present :  an  internal,  concave, 
thin,  and  sharj)  border,  embracing  the  tibial  spine  ;  an  external,  thick,  and  convex 
border  ;  a  superior  face,  excavated  and  moulded  to  one  of  the  condyles  ;  an  inferior 
face,  nearly  plane,  gliding  on  the  tibia  ;  and  two  extremities  terminated  by  liga- 
ments, and  fixed  to  the  bones  in  apposition.  The  articular  surfaces  are  not  entirely 
separated  throughout  their  extent  by  these  complementaiy  meniscii,  for  the  tibial 
spine  rubs  directly  against  the  inner  sides  of  the  femoral  condyles.  The  internal 
semilunar  fihro-cartilage,  the  widest  and  thickest,  is  inserted  by  its  anterior 
extremity  into  one  of  the  excavations  situated  in  front  of  the  spine  ;  its  posterior 

1  By  this  name  is  understood  the  joint  uniting  the  femur  to  the  tibia,  and  that  which 
articulates  it  with  the  patella.  Following  the  example  of  anthropotomists,  it  has  not  been 
deemed  necessary  to  describe  a  femoro-patellar  articulation  distinct  from  the  femoro-tibial, 
properly  so  called.  This  innovation  appears  to  be  justified  by  the  community  of  the  principal 
articular  bands  which  bind  these  two  joints,  and  by  the  reciprocal  dependence  of  their 
movements. 


ABTICULATIONS   OF  THE  POSTERIOR   LIMBS. 


217 


extremity  is  attached  in  the  fossa  behind  that  eminence.  The  external  semilunar 
fiiro-cartilage  is  fixed,  in  front,  near  the  anterior  insertion  of  the  opposite  fibro- 
cartilage  ;  its  posterior  extremity  gives  origin  to  two  slips  or  cords,  one  superior, 
the  other  inferior.  The  first,  the  strongest  and  longest,  terminates  in  the  fossa 
near  the  posterior  extremity  of  the  intercondyloid  notch.  The  second,  thin  and 
■flat,  is  inserted  on  the  posterior  outline  of  the  external  tibial  facet.  The  external 
border  of  this  meniscus  is  separated  from  the  external  lateral  ligament  by  the 
tendon  of  the  popliteus  muscle,  and  acts,  with  regard  to  this  tendon,  as  a  pulley. 
Mode  of  union. — The  bands  which  bind  this  complicated  articulation  are  veiy 


Fig.  141. 


FEMORO-TIBIAL   ARTICULATION'. 

A. — Posterior  face  :  the  posterior  lignment  has  been  removed.  1,  External  meniscus  ;  2,  fibrous 
fasciculi  fi.xiug  it  to  the  femur  ;  3,  fibrous  fascia  which  attaches  it  to  the  posterior  contour  of  the 
tibial  surface ;  4,  internal  meniscus  ;  5,  tibial  insertion  of  the  posterior  crucial  ligament ;  6, 
external  lateral  ligament ;  7,  mternal  lateral  ligament. 

B. — External  face  :  the  external  condyle  of  the  femur  and  the  meniscus  have  been  removed  to 
show  the  crucial  ligaments.  1,  Anterior  crucial  ligament;  2,  posterior  ditto;  3,  fibular  insertion 
of  the  external  lateral  ligament ;  4,  anterior  patellar  ligaments.  A,  Internal  meni.^^cus  ;  B,  anterior 
insertion  of  the  external  meniscus  ;  C,  passage  for  the  tendinous  cord  common  to  the  flexor  of  the 
metatarsus  and  the  anterior  extensor  of  the  phalanges ;  D,  anterior  and  superior  tuberosity  of 
the  tibia;  E,  tibial  crest. 

numerous.  They  will  be  successively  described  as  :  1 .  Those  which  attach  the 
patella  to  the  tibia.     2.  Those  which  unite  the  femur  with  the  tibia. 

A.  Ligaments  attaching  the  -patella  to  the  tibia. — The  patella  is  bound  to  the 
tibia  by  three  funicular  ligaments,  designated  by  the  generic  epithet  of  "  patellar." 
They  are  situated  in  front  of  the  articulation,  and  transmit  to  the  leg  the  action 
of  the  muscles  which  are  attached  to  the  patella.  They  are  distinguished  accord- 
ing to  their  position,  as  external,  internal,  and  middle  (Fig.  142,  2,  3,  4). 

a.  The  external  patellar  ligament,  the  largest  and  most  powerful,  is  a  flattened 
band,  attached,  by  its  lower  extremity,  to  the  culminating  point  of  the  anterior 
tuberosity  of  the  tibia.  Its  upper  extremity  is  fixed  to  the  anterior  face  of  the 
patella,  and  is  confounded  with  the  patellar  insertion  of  the  superficial  gluteus. 
It  is  joined  to  the  internal  ligament  by  a  veiy  resisting  aponeurotic  extension,  a 
dependency  of  the  fascia  lata. 


218  THE  ARTICULATIONS. 

b.  Tlie  interna]  patellar  ligament  also  forms  a  flattened  band,  longer,  but  not 
80  wide  or  thick  as  the  preceding.  Its  inferior  extremity  is  attached  to  the  inner 
side  of  the  anterior  tuberosity  of  the  tibia.  Its  superior  extremity  becomes  much 
thickened  and  fibro-cartilaginous,  and  is  inserted  into  a  prominence  inside  the 
patella.  This  fibro-cartilaginous  portion  (Fig.  Ii2,  3)  of  the  ligament  ghdes  on 
the  internal  border  of  the  femoral  trochlea,  and  may  justly  be  considered  as  a 
complementary  apparatus  of  the  patellar  surface.  The  ligament,  joined  to  the 
preceding  by  the  hbrous  fascia  ab-eady  mentioned,  is  confounded,  inwardly,  with 
the  aponeurosis  of  the  adductor  muscles  of  the  leg. 

c.  The  middle  patellar  ligament  is  a  round  cord,  situated,  as  its  name  indicates, 
between  the  other  two,  concealed  beneath  the  aponeurosis  which  unites  these,  and 
in  the  middle  of  the  adipose  tissue  protecting  the  synovial  capsules  in  front.  It 
leaves  the  anterior  face  of  the  patella,  and  descends  vertically  to  the  tibia,  to  be 
lodged  in  the  fossa  in  the  middle  of  the  anterior  tuberosity,  where  a  small  synovial 
bursa  facilitates  its  movements.  Its  inferior  extremity  is  inserted  into  the  most 
decUvitous  part  of  this  excavation. 

B.  Ligaments  which  attach  the  leg  and  thigh  hones. — These  are  six  in  number  : 

1.  A  femoro-patellar  capsule  maintaining  the  patella  against  the  femoral  trochlea. 

2.  Five  femoro-tibial  ligaments,  as  follows :  two  lateral,  two  external  and 
internal ;  a  posterior  ;  and  two  interarticular,  distinguished  with  reference  to 
their  inferior  insertion  into  anterior  and  posterior. 

1.  T\\Q  femoro-patellar  capsule  is  a  membranous  expansion  which  covers,  above 
and  laterally,  the  superior  synovial  membrane.  This  capsule  is  attached  by  its 
borders  around  the  femoral  trochlea  and  the  periphery  of  the  patellar  surface. 
It  is  extremely  thin  in  its  superior  part ;  but  laterally  it  is  thicker,  and  consti- 
tutes two  wide  fibrous  fasciculi  which  bind  the  patella  to  the  eccentric  sides  of 
the  two  condyles,  and  is  described  in  several  works  as  two  special  ligaments.  Its 
external  face  is  covered  by  the  insertion  of  the  superficial  gluteus  and  the  triceps 
cruralis. 

2.  Femoro-tibicd  ligaments. — a.  The  lateral  ligammts  are  two  ribbon-shaped 
cords  situated  at  the  extremities  of  the  transversal  axis  of  the  articulation,  more 
behind  than  before ;  they  are  relaxed  during  flexion,  and  very  tense  in  ex- 
tension. 

The  external,  the  shortest  and  strongest,  proceeds  from  one  of  the  hollow 
facets  on  the  external  condyle  of  the  femur,  and  is  inserted  into  the  head  of  the 
fibula  by  its  inferior  extremity,  after  gliding  over  the  external  tuberosity  of  the 
tibia  by  means  of  a  special  synovial  bursa.  It  is  covered  by  the  crural  or  tibial 
aponeurosis,  and  covers  the  tendon  of  the  popliteus,  from  which  it  is  sometimes 
separated  by  a  vesicular  synovial  membrane. 

The  internal  is  attached,  superiorly,  to  the  eminence  of  insertion  that  sur- 
mounts the  eccentric  face  of  the  internal  condyle,  and  descends  vertically  to  the 
tibia,  gliding  over  the  margin  of  its  articular  surface  by  means  of  a  small  facet 
covered  with  cartilage,  and  a  nd-de-sac  prolongation  of  the  internal  synovial 
membrane.  It  is  fixed  by  its  inferior  extremity  to  the  imprints  which  cover  the 
internal  tibial  tuberosity. 

Its  fil)res  are  disposed  in  two  layers,  which  slightly  intercross  in  X  fashion  ; 
those  passing  downwards  and  forwards  adhere  to  the  border  of  the  internal 
meniscus.  Covered  by  the  aponeurosis  of  the  adductor  muscles  of  the  leg,  this 
ligament  adheres  by  its  deep  face  to  the  internal  meniscus. 

b.  The  posterior  ligament  belongs  to  the  class  of  membranous  or  capsular 


ARTICULATIONS  OF  TEE  POSTERIOR  LIMBS.  219 

ligaments.  It  is  formed  of  two  aponeurotic  layers  separated  superiorly,  but 
confounded  inferiorly.  The  superficial  layer  is  composed  of  strong,  fibrous, 
intercrossed  fasciculi,  perforated  with  vascular  openings.  It  is  fixed,  above,  to 
the  posterior  face  of  the  femur,  below  the  external  gastrocnemius  muscle.  The 
deep  lamina  envelops,  like  a  cap,  the  femoral  condyles.  After  becoming  united, 
these  two  laminse  are  attached  to  the  posterior  face  of  the  tibia,  close  to  the 
superior  articular  face  of  that  bone.  Its  external  face  is  in  contact  with  the 
popliteal  vessels,  and  the  gastrocnemius  muscle.  Its  internal  face  is  covered 
throughout  nearly  the  whole  of  its  extent  by  the  lateral  synovial  membranes, 
embraces  the  condyles  of  the  femur,  and  adheres  to  the  posterior  crucial  liga- 
ment, as  well  as  to  the  interarticular  meniscii. 

c.  The  interosseous  ligaments  are  two  funicular  bands  lodged  in  the  inter- 
condyloid  notch.  They  are  more  commonly  designated  crucial  ligaments,  because 
they  cross  each  other  at  their  middle  part,  like  the  letter  X  (Fig.  141). 

The  anterior,  oblique  downwards  and  forwards,  is  attached  by  its  superior 
extremity  to  the  bottom  of  the  intercondyloid  notch,  and  inwardly  to  the  external 
condyle.  Its  inferior  extremity  is  fixed  in  the  groove  on  the  summit  of  the  tibial 
spine.  The  fibres  entering  into  its  formation  are  not  parallel,  but  slightly  twisted 
in  a  spiral  manner. 

The posterior,\ongeY  than  the  preceding, and  oblique  in  the  opposite  dii-ection, 
is  inserted,  inferiorly,  into  the  little  eminence  behind  the  internal  tibial  facet ; 
whence  it  goes  to  the  bottom  of  the  intercondyloid  notch,  to  be  attached  by  its 
superior  extremity  within  the  internal  condyle. 

Sgnovial  membranes. — For  this  articulation  there  are  three  synovial  mem- 
branes :  a  superior  and  two  lateral.  The  first,  very  large  and  strengthened  by 
the  femoro-patellar  capsule,  facilitates  the  gliding  of  the  patella  on  the  femoral 
pulley  ;  it  is  prolonged  in  a  cul-de-sac  below  the  insertion  of  the  crural  triceps. 
The  other  two,  which  lubricate  the  articular  surfaces  of  the  proper  femoro-tibial 
joint,  include  the  crucial  ligaments  between  them,  and  cover  the  posterior 
ligament,  the  lateral  ligaments,  and  the  fibrous  fasciculi  for  the  attachment  of 
the  meniscii.  The  external  lines,  in  addition,  the  tendon  of  the  popliteus  muscle, 
and  furnishes  a  vast  cul-de-sac  which  descends  in  the  anterior  groove  of  the  tibia, 
to  envelop  the  tendon  common  to  the  anterior  extensor  of  the  phalanges  and  the 
flexor  of  the  metatareus.  These  two  femoro-tibial  synovial  membranes  lie  against 
that  of  the  femoro-patellar  articulation,  in  front  of  the  condyles  and  the  notch 
which  separates  them,  and  if  not  always,  at  least  not  unfrequently,  they  com- 
municate with  it.  The  three  are  separated  from  the  ligaments  of  the  patella  by 
a  considerable  mass  of  adipose  tissue,  which  is  prolonged  into  the  inter-condyloid 
notch,  at  the  bottom  of  which  it  appeal's  to  be  fixed. 

The  synovial  cavities  sometimes  communicate  with  each  other,  but,  according 
to  Lesbre,  this  is  rare. 

Movements— 'T\m  imperfect  hinge-joint  can  execute  the  two  principal  and 
opposite  movements  of  flexion  and  extension,  and  a  somewhat  limited  accessory 
movement  of  rotation.  The  mechanism  of  these  movements  being  simple  enough 
to  be  readily  understood  without  any  preliminary  explanation,  they  will  not  be 
detailed  here  ;  but  some  remarks  will  be  made  with  regard  to  the  displacement 
the  fibro-cartilages  undergo,  when  the  articulation  is  in  motion. 

During  flexion  and  extension,  these  bodies,  fixed  on  the  tibial  facets,  which 
they  transform  into  glenoid  cavities,  move  with  them  on  the  condyles  of  the 
femur,  from  before  to  behind,  or  behind  to  before,  according  to  the  movement 


THE  ARTICULATIONS. 


No.  1. 


No.  2. 


executed.  But  at  the  same  time  they  also  glide  in  an  inverse  direction,  and 
to  a  very  appreciable  degree,  on  the  superior  extremity  of  the  tibia.  Therefore, 
during  flexion,  they  pass  from  behind  forward  on  this  extremity,  and  are  drawn 
backwards  during  extension. 

In  rotation — which  may  take  place  from  within  to  without,  or  from  without  to 
within — the  movement  is  produced  not  only 
Fig.  142.  by  the   pivoting  of   the   condyles   in  their 

glenoid  cavities,  but  also  by  a  fusible  dis- 
placement of  the  meniscii  on  the  tibial  sur- 
faces. 


In  the  Dog  and  Cat,  the  meniscii  are  joined 
together,  near  their  anterior  insertion,  by  a  trans- 
verse fibrous  band.  There  is  only  one  patellar  liga- 
ment, and  the  posterior  ligament  shows  in  its  sub- 
stance, two  !<mall  sesamoid  bones  against  which  the 
condyles  of  the  femur  play  inwardly,  and  which  give 
attachment,  outwardly,  to  the  originating  branches 
of  the  gastrocnemius  muscle.  There  is  no  femoro- 
patellar  capsule,  and  only  one  synovial  membrane 
for  the  whole  articulation. 

In  the  Pig  and  Sheep,  there  is  also  only  one 
ligament  ;iud  one  synovial  capsule. 


4.    TiBIO-FIBULAR   ARTICULATION. 

This  articulation  represents  a  small  plani- 
form  diathrosis,  the  movements  of  which  are 
very  limited  and  obscure.  It  is  formed  by 
the  union  of  the  irregular  diathrodial  facet 
which  occupies  the  internal  face  of  the  head 
of  the  fibula,  with  the  analogous  facet  on  the 
external  superior  tuberosity  of  the  tibia. 
Short  and  strong  interosseous  or  peripheral 
fibres  envelop  these  facets  on  every  side, 
and  maintain  them  firmly  in  contact. 

The  fibula  is  also  attached  to  the  tibia  : 
"  1.  Above,  by  two  small  ligamentous  fasci- 
culi crossed  like  the  letter  X,  wdiich  form  the 
superior  part  of  the  great  arch  through  w^hich 
pass  the  anterior  tibial  arteiy  and  vein  (Fig. 
142,  12).  2.  In  the  middle,  by  a  kind  of 
aponeurotic  membrane,  the  wddth  of  which 
diminishes  from  above  to  below,  like  that  of 
the  space  it  fills  (Fig.  142,  13).  3.  Below, 
by  a  ligamentous  cord  (Fig.  142,  14)  which 
prolongs  the  fibula  to  the  external  tuberosity 
of  the  inferior  extremity  of  the  tibia,  where 
to  the  two  external  lateral  ligaments  of  the 


LIGAMENTS  ATTACHING  THE  THREE  BONES 
OF   THE   LEG. 

No.  1.  Posterior  face.  No.  2.  Anterior  face. 
1,  Complementary  fibro-cartilagiuous 
pad  of  the  patellar  surface ;  2,  e.\ternal 
patellar  ligament;  2',  insertion  of  the 
superficial  gluteal  into  this  ligament;  3, 
internal  patellar  ligament ;  3',  its  upper 
insertion  transformed  into  a  comple- 
mentary apparatus  of  the  patellar  sur- 
face ;  4,  midijle  patellar  ligament;  5, 
external  meniscus  of  the  tibia;  6,  its 
branch  of  insertion  into  the  femur  cut 
off  at  its  origin ;  7,  its  posterior  tibial 
insertion  ;  8,  external  meniscus  ;  9,  in- 
sertion of  the  anterior  crucial  ligament 
into  the  fossa  of  the  tibial  spine ;  10, 
tibial  insertion  of  the  posterior  crucial 
ligament;  11,  inferior  insertion  of  the 
external  femoro-tibial  ligament ;  12,  13, 
14,  tibio-fibular  ligaments.  A,  Tibial 
arch ;  B,  surface  of  insertion  of  the 
popliteus  muscle  ;  C,  surface  of  insertion 
for  the  perforans  muscle. 


this  cord  bifurcates,  and  is  united 
tibio-tarsal  articulation  "  (Rigot). 


In  the  Ox,  Sheep,  and  Goat,  the  fibula  being  replaced  by  a  ligament,  there 
tibio-fibular  articulation. 


no  proper 


ARTICULATIONS  OF   THE  POSTERIOR  LIMBS.  221 

In  the  Dog  and  Cat,  the  two  principal  bones  of  the  leg  are  united  at  their  extremities 
and  middle  part :  • 

1.  At  their  superior  extremity,  by  means  of  a  small  arthrodial  articulation,  analogous  to 
that  of  the  Horse,  and,  like  it,  provided  witli  a  particular  synovial  bursa; 

2.  At  their  inferior  extremity,  by  means  of  a  second  artiirodial  articulation,  whose  action  is 
facilitated  by  a  prolongation  of  the  tibio-tarsal  synovial  membrane; 

3.  By  their  middle  part,  through  the  interposition,  between  the  two  bones,  of  an  inter- 
osseous ligament,  which  is  wide  and  membranous  in  its  upper  two-thirds,  and  formed  of 
extremely  short  and  strong  fibres  at  its  lower  third. 

5.  Aeticulations  of  TttE  Tarsus  or  Hock  (Figs.  141,  144). 

Preparntion. — Commence  by  cutting  off  the  tendons,  and  so  exposing  the  lateral  ligaments 
of  the  tibio-tarsal  diathrosis.  Tlien  the  procedure  should  be  as  for  the  carpus — dissect  suc- 
cessively the  ligaments  proper  to  each  row,  those  uniting  the  two  rows,  and  those  binding  the 
lower  row  to  the  metatarsus. 

These  comprise  :  1.  The  tibio-tarsal  articulation.  2.  The  articulation  of  the 
first  row  of  bones — the  astragalu3  and  calcaneum  or  calcis.  3.  Those  which  unite 
the  bones  of  the  lower  row.  4.  The  articulation  of  the  two  rows  with  each  other. 
5.  The  tarso-metatarsal  articulation.  The  first  is  a  perfect  ginglymoid,  and  the 
only  joint  really  movable  ;  all  the  others  are  aythrodial,  and  their  action  is  so 
restricted  that  they  appear  to  be  condemned  to  almost  absolute  immobility. 
This  intimate  union  of  the  tarsal  and  metatarsal  bones,  is  evidently  chiefly  intended 
to  guarantee  precision  in  the  movements  of  the  tibio-tarsal  articulation. 

Tibio-tarsal  Articulation. — Two  bones  alone  concur  in  the  formation 
of  this  angular  ginglymoid  joint  :  these  are  the  tibia  and  astragalus. 

Articular  surfaces. — For  the  tibia  :  1.  The  two  deep  grooves,  oblique  forwards 
and  outwards,  channeled  in  the  inferior  extremity  of  the  bone.  2.  The  salient 
tenon  which  separates  these  grooves,  and  on  which  there  is  often  a  small  synovial 
fossette.     For  the  astragalus,  the  pulley  occupying  its  anterior  face  (see  p.  145). 

Mode  of  union. — Seven  ligaments  bind  these  articulations  :  two  external 
lateral,  three  internal  lateral,  an  anterior,  and  a  posterior. 

a.  External  lateral  ligaments. — These  are  distinguished,  according  to  their 
relative  position,  into  superficial  and  deep. 

The  external  superficial  ligament  (Figs.  143,  2  ;  144,  2)  is  a  thick  funicular 
cord,  flattened  in  its  inferior  half.  It  commences  above  on  the  external  tube- 
rosity of  the  tibia,  behind  the  groove  which  divides  this  tuberosity  into  two 
parts  ;  from  thence  it  descends  almost  vertically,  fixing  itseU"  successively  to  the 
astragalus,  calcaneum,  cuboides,  middle  metatarsal  bone,  and  the  external  rudi- 
mentary metatarsal  bone.  Passing  in  front  with,  and  partly  covered  by,  the 
lateral  extensor  of  the  phalanges,  to  which  it  supplies  a  retaining  band  (Fig. 
143,  2),  this  ligament  is  confounded  behind,  and  near  its  inferior  extremity, 
with  the  calcaneo-metatarsal  ligament.  It  covers  the  external  and  deep  ligament, 
the  short  band  which  constitutes  the  external  calcaneo-astragaloid  ligament,  the 
insertion  of  one  of  the  branches  of  the  flexor  of  the  metatarsus,  and  the  small 
cuboido-cunean  (cuneiform)  ligament. 

The  external  deep  ligament  (Figs.  143,  1  ;  144, 1),  much  shorter  than  the  pre- 
ceding, is  attached,  superiorly,  to  the  anterior  part  of  the  external  tuberosity  of 
the  tibia,  and  is  directed  obliquely  backwards  and  downwards,  to  be  fixed  by  two 
fasciculi  at  the  external  side  of  the  astragalus  and  calcis.  This  ligament,  covered 
by  the  preceding,  which  crosses  it  like  an  X,  is  lined  on  its  inner  face  by  a 
synovial  membrane  of  the  articulation. 
17 


222 


THE  ARTICULATIONS. 


b.  Internal  lateral  ligaments. — These  are  also  three  funicular  bands  superposed 
on  one  another,  and  arb  consequently  designated  as  superficial,  middle,  and  deep. 
The  internal  superficial  ligament  (Fig.  14.3,  6),  the  strongest  and  longest  of 
the  three,  proceeds  from  the  internal  and  inferior  tuberosity  of  the  tibia, 
diminishing  as  it  descends  on  the  inner  side  of  the  tarsus.  It  is  fixed,  in  mixing 
with  the  astragalo-metatarsal  ligament  and  with  the  posterior  tarso-metatareal 
ligamentous  arrangement,  to  the  tuberosity  of  the  astragalus,  the  scaphoid,  the 
two  cuneifoi-m,  the  superior  extremity  of  the  principal  metatarsal,  and  that  of  the 
internal  rudimentary  metatarsal  bones. 

The  internal  middle  ligament  (Fig.  143,  5)  is  com- 
posed of  two  funicular  cords,  attached  in  common  beneath 
the  preceding  ligament  to  the  internal  tibial  tuberosity. 
These  two  fasciculi,  exactly  resembling  those  of  the  ex- 
ternal deep  ligament,  are  directed  downward  and  back- 
ward, and  terminate,  one  at  the  astragalus,  the  other 
at  the  calcis. 

The  internal  deep  ligament  (Fig.  144,  4)  is  an  extremely 
slender  fasciculus,  enveloped  by  the  synovial  membrane ; 
it  is  often  reduced  to  a  thin  shred,  scarcely  distinct  from 
the  serous  covering  surrounding  it.  It  is  attached,  in  one 
direction,  to  the  tibia  below  the  middle  ligament ;  in 
the  other,  to  the  astragalus,  and  nearly  at  the  same  point 
as  the  superior  fasciculus  of  the  middle  ligament. 

c.  Anterior  ligament. — This  is  a  membraniform  band 
formed  of  intercrossed  fibres,  stronger  outwards  than  in- 
wards, attached  by  its  upper  border  above  and  in  front 
of  the  tibial  surface,  fixed  by  its  inferior  border  to  the 
astragalus,  the  scaphoid  and  great  cuneiform  bones,  and 
the  astragalo-metatarsal  ligament ;  it  is  confounded  at  its 
sides  with  the  two  superficial  lateral  ligaments.  Its  internal 
face  is  lined  by  articular  synovial  membrane,  while  the  ex- 
ternal is  covered  by  the  flexor  of  the  metatarsus,  the  anterior 
extensor  of  the  phalanges,  the  anterior  tibial  arteiy,  and 
several  large  anastomosing  veins,  from  the  junction  of 
which  arises  the  anterior  tibial  vein. 

d.  Posterior  ligament. — This  is  the  second  membrani- 
form or  capsular  band,  which  protects  the  articulation 
posteriorly.  It  presents,  in  its  centre,  a  fibro-cartilaginous 
thickening,  on  which  gUdes  the  perforans  tendon.  It  is 
attached,  above,  to  the  tibia  ;  below,  to  the  astragalus  and 
calcis ;   at  its  sides  it  is  mixed  with  the  two  superficial 

lateral  ligaments,  and  the  astragalian  fasciculus  of  the  middle  internal  ligament. 
Its  internal  face  is  lined  by  articular  synovial  membrane  ;  the  external  is  covered 
and  lubricated  by  the  vaginal  serous  membrane,  which  facilitates  the  gliding  of 
the  perforans  tendon  in  the  tarsal  sheath. 

Synovial  membrane. — This  membrane  is  developed  at  the  internal  face  of  the 
two  capsular  ligaments,  lines  the  greater  part  of  the  three  internal  ligaments, 
and  also  the  external  deep  ligament.  It  communicates,  in  front  and  below,  with 
the  synovial  membrane  proper  to  the  articulation  of  the  two  rows  of  tarsal  bones. 
When  it  becomes  the  seat  of  dropsical  effusion,  it  is  always  distended  forwards 


parsal  articitlations 
(front  view). 

,  External  deep  ligament 
of  the  tibio-taisal  ar- 
ticulation ;  2,  2,  ex- 
ternal superficial  liga- 
ment ;  4,  internal  deep 
ligament ;  5,  internal 
middle  ligament ;  6,  In- 
ternal superficial  liga- 
ment ;  7,  astragalo- 
metatarsal  ligament ;  8, 
small  cuboido-cunean 
ligament.  A,  Pulley  of 
the  astragalus;  B,  cu- 
boidal  insertion  belong- 
ing to  tne  tendinous 
cord  of  the  flexor  of  the 
metatarsus ;  C,  vascular 
canal  of  the  tarsus. 


ARTICULATIONS   OF  THE  POSTERIOR  LIMBS.  223 

and  inwards,  because  it  is  only  sustained  at  that  place  by  the  anterior  capsular 
ligament.  But  the  effusion  may  also  elevate  the  posterior-  ligament,  and  produce 
hernia  in  the  hollow  of  the  hock,  behind  the  lateral  ligaments.  It  is  not,  there- 
fore, absolutely  correct  to  attribute  all  the  synovial  tumours  in  the  hollow  of  the 
hock  to  dilatation  of  the  tarsal  tendinous  sheath.  (See  the  figure  of  the  tendons 
and  synovial  capsules  of  the  posterior  limb,  in  the  description  of  the  perforans 
muscle.) 

Movements. — Nothing  can  be  less  complicated  than  the  mechanism  of  the 
tibio-tarsal  articulation,  this  joint  only  permitting  two  opposite  movements — 
those  oi  flexion  and  extension — which  are  so  simple  and  precise  that  we  may  dispense 
with  a  description  of  the  manner  in  which  they  are  executed.  It  may  only  be 
remarked  that,  in  order  to  prevent  contact  between  the  leg  and  foot  during  flexion, 
the  latter  fraction  of  the  limb  deviates  a  little  outwards,  owing  to  the  marked 
obliquity  of  the  articular  grooves. 

Articulation  of  the  Bones  of  the  First  Row,  or  Calcaneo-astraga- 
LOiD  Articulation. — This  is  a  compound  arthrodial  joint,  resulting  from  the 
coaptation  of  the  three  or  four  articular  facets  of  the  posterior  face  of  the  astragalus 
with  the  analogous  facets  of  the  calcis. 

This  joint  is  maintained  by  the  lateral  ligaments  of  the  tibio-tarsal  articulation, 
and  by  four  cakaneo-astragaloid  ligaments — a  superior,  external,  internal,  and  the 
last  interosseous. 

The  superior  calcaneo-astragaloid  ligament  is  formed  of  short  parallel  fibres 
thrown  across  from  one  bone  to  the  other,  and  is  situated  towards  the  superior 
extremity  of  the  pulley  of  the  astragalus  ;  it  is  lined  superiorly  by  the  synovial 
membrane  of  the  tibio-tarsal  articulation. 

The  lateral  ligaments  are  two  very  thin  fasciculi  concealed  by  the  ligaments 
which  bind,  laterally,  the  tibia  to  the  tarsal  bone. 

The  interosseous  ligament  is  very  strong,  and  occupies  a  great  portion  of  the 
rugged  excavation  which  separates  the  articular  facets. 

This  articulation  does  not  usually  possess  proper  synovial  capsules.  Two 
prolongations  of  the  synovial  membrane  of  the  two  rows,  in  ascending  between 
the  calcis  and  astragalus,  facilitate  the  gliding  of  the  two  inferior  facets.  An 
analogous  prolongation  of.  the  tibio-tarsal  synovial  membrane  is  effected  for  the 
superior  facets,  and  it  is  not  rare  to  find  this  prolongation  form  a  distinct 
capsule. 

Movements  nearly  null. 

Articulation  of  the  Bones  of  the  Second  Row  with  each  other. — 
These  bones,  four  in  number,  are  brought  into  contact  in  the  following  manner  : 
The  cuboides  responds  to  the  scaphoid  by  two  facets — one  anterior,  the  other 
posterior  ;  it  articulates  with  the  great  cuneiform  by  two  similar  facets,  the 
posterior  of  which  is  not  always  present.  The  scaphoid  is  united  to  the  two  cunei- 
forms by  the  large  convex  facet  occupying  its  entire  lower  face.  The  two  cunei- 
forms are  joined  by  means  of  a  small  articular  surface. 

The  fibrous  fasciculi  which  maintain  the  diarthrodial  surfaces  in  contact  are 
somewhat  numerous.     They  are  as  follows  : — 

1.  The  astragalo-metatarsal  ligament  and  tarso-metatarsal  apparatus,  which 
will  be  described  hereafter  ;  these  two  bands  do  not  properly;  belong  to  the  articu- 
lations of  the  second  row  of  bones. 

2.  Two  anterior  ligaments,  named  cuhoido-scaphoid  and  cuboido-cunean  (Figs. 
143,  8  ;  144,  5),  which  are  carried  from  the  cuboid  to  the  scaphoid  and  to  the 


224 


THE  ARTICULATIONS. 


great  cuneiform  bone,  one  above,  the  other  below  the  vascular  channel  formed 
between  these  three  bones. 

3.  Two  interosseous  ligaments  analogous  to  the  preceding  two.  forming  the 
superior  and  inferior  walls  of  the  aforesaid  channel. 

4.  An  interosseous  scaphoido-cunean  ligament,  passing  from  the  scaphoid  to 
the  two  cuneiform  bones. 

5.  An  interosseous  ligament,  named  the  intercunean,  is  directed  from  one 
cuneiform  bone  to  the  other,  and  is  confounded  with 
the  preceding  ligament. 

The  disposition  of  the  lubricating  membranes 
varies  with  that  of  the  articular  facets.  The  follow- 
ing is  what  is  most  generally  observed  :  A  proper 
synovial  membrane  is  specially  destined  for  the  facets 
by  which  the  scaphoid  and  gi'eat  cuneiform  bones 
correspond  ;  this  synovial  membrane  belongs  also  to 
the  two  cuboido-scaphoid  and  posterior  cuboido- 
cunean  arthrodiae.  The  anterior  cuboido-scaphoid 
diarthrosis  receives  a  prolongation  from  the  synovial 
membrane  of  the  two  rows.  The  play  of  the  anterior 
cuboido-cunean  and  intercunean  facets  is  facilitated 
by  two  prolongations  of  the  tarso-metatai'sal  synovial 
membrane. 

Movements  almost  null. 

Articulation  of  the  two  Rows  with  each 
OTHER. — This  arthrodial  joint  is  formed  by  the  union 
of  the  calcis  and  the  astragalus,  on  the  one  side,  with 
the  scaphoid  and  cuboid  bones  on  the  other.  Its 
solidity  is  assured  by  six  principal  bands  : 

1.  The  two  lateral  superficial  ligaments  of  the 
tibio-tarsal  articulation. 

2.  The  calcaneo-metatarml  ligament  (Fig.  144, 
3),  a  strong  fibrous  brace  which  unites  the  posterior 
border  of  the  calcis  to  the.cuboides,  and  to  the  head 
of  the  external  rudimentaiy  metatarsal  bone.  It  is 
confounded,  outwardly,  with  the  external  and  super- 
ficial tibio-tarsal  ligament ;  inwardly,  with  the  pos- 
terior tarso-metatarsal  band. 

3.  The  astragalo-metatarsal  ligament  (Fig.  143, 
7),  a  radiating  fasciculus,  the  fibres  of  which  leave  the 
internal  tuberosity  of  the  astragalus,  become  mixed 
up  with  the  internal  and  superficial  tibio-tarsal  liga- 
ments in  diverging  downwards  to  the  scaphoides,  the  great  cuneiform  bone,  and 
the  upper  extremity  of  the  principal  metatarsal  bone. 

4.  The  posterior  tarso-metatarsal  ligament  is  a  vast,  very  strong,  and  very 
complicated  fibrous  arrangement,  which  binds,  posteriorly,  all  the  tarsal  bones, 
and  also  fixes  them  to  the  three  portions  of  the  metatarsus.  This  band,  which  is 
crossed  by  several  tendons  and  by  the  artery  and  vein  lodged  in  the  cuboido- 
scaphoido-cunean  canal,  is  continued  below  by  the  tarsal  stay  of  the  perforans 
tendon.  It  therefore  closely  resembles  the  posterior  carpal  ligament.  Its  posterior 
face  is  covered  by  the  tendinous  synovial  membrane  lining  the  tarsal  sheath  for 


ARTICULATIONS   OF   THE   TARSUS 
(LATERAL   VIEW). 

1,  External  deep  ligament;  2, 
external  superficial  ligament ; 
2',  ring  furnished  by  the  latter 
ligament  for  the  passage  of  the 
lateral  extensor  tendon  of  the 
phalanges;  3,  calcaneo-meta- 
tarsal  ligament ;  4,  astragalo- 
metatarsal  ligament ;  5,  small 
cuboido-cunean  ligament.  A, 
Cuboidal  insertion  of  the  flexor 
muscle  of  the  metatarsus ;  B, 
anterior  orifice  of  the  vascular 
conduit  of  the  tarsus  ;C,  groove 
on  the  external  tuberosity  of 
the  tibia  for  the  gliding  of  the 
lateral  extensor  of  the  pha- 
langes ;  D,  insertion  of  the  gas- 
trocnemius tendon  of  the  leg 
into  the  os  calcis ;  E,  gliding 
surface  for  that  tendon. 


THE  ARTICULATIONS  IN   BIRDS.  22S 

the  passage  of  the  perforaiis  tendons.  It  is  confounded,  on  its  sides,  with  the 
calcaneo-metatarsal,  and  the  internal  and  superficial  tibio-tarsal  ligaments. 

5.  An  interosseous  liyamenf,  attached  to  the  four  bones  composing  this 
articulation. 

It  is  provided  with  a  particular  synovial  membrane  which  always  communi- 
cates, in  front,  with  the  tibio-tarsal  capsule.  This  membrane  is  prolonged, 
superiorly,  between  the  calcis  and  astragalus,  to  lubrify  two  of  the  facets  by 
which  these  bones  come  into  contact ;  and,  in  addition,  it  descends  between  the 
cuboid  and  scaphoid  bones,  to  form  a  third  prolongation  for  the  anterior  cuboido- 
scaphoid  arthrodia. 

Movements  almost  null. 

Takso-metataesal  Aeticulation. — This  joint,  formed  by  the  meeting  of 
the  three  tarsal  bones — the  cuboid  and  the  two  cuneiforms — with  the  three  bones 
of  the  metatarsus,  is  fixed  by  the  lateral  superficial  ligaments  of  the  tibio-tarsal 
articulation,  the  calcaneo-metatarsal  hgament,  those  which  have  been  named  the 
astragalo-metatarsal  and  tarso-metatarsal,  and  by  a  strong  interosseous  ligament 
which  naturally  forms  three  fasciculi. 

The  synovial  membrane  proper  to  this  joint  ascends  into  the  small  anterior 
cuboido-cunean  arthrodia,  and  into  that  which  unites  the  two  cuneiform  bones  ;  it 
descends  to  the  intermetatarsal  articulations. 

Movements  nearly  null. 

In  all  the  domesticated  animals  except  Solipeds,  the  tarsal  articulations  offer  some  differen- 
tial peculiarities,  the  study  of  which  is  without  interest,  as  it  is  without  utility.  It  is  only 
necessary  to  remark  that  the  immobility  of  the  tarsal  joints,  properly  so  called,  is  less  absolute 
than  in  Solipeds,  owing  to  the  peculiar  configuration  of  the  articular  surfaces  of  some  of  the 
bones  composing  them.  Thus,  in  the  Ox,  Sheep,  Goat,  and  Pig,  the  calcis  is  joined  to  the 
astragalus  by  a  real  trochlear  articulation,  and  the  latter  bone  is  united  to  the  scaphoid  by  a 
diarthrodial  joint  of  the  same  kind — a  mode  of  articulation  much  more  favourable  to  motion 
than  that  of  the  planiform  diarthrodial  joint.  In  the  Dog  and  Cat,  the  same  result  is 
obtained  by  the  reception  of  the  head  of  tlie  astragalus  into  the  superior  cavity  of  the  scaphoid. 

In  Ruminants  and  the  Pig,  it  is  also  observed  that  the  tibio-tarsal  articulation  is  formed 
by  the  tibia  and  fibula  in  the  one  direction,  and  by  the  astragalus  and  os  calcis  in  the  other. 

Lemoigne,  who  has  been  again  recently  studying  the  mechanical  arrangement  of  the  Ox's 
hock,  remarks  that,  if  the  mobility  of  all  the  tarsal  articulations  deprive  the  posterior  limb  of 
that  animal  of  the  rigidity  necessary  fur  speed,  yet  the  nature  of  the  astragalo-calcanean  articu- 
lation gives  it  great  power.  In  fact,  the  posterior  trochlea  of  the  astragalus  acts  as  an  eccentric 
on  the  calcis  during  movement,  and  gradually  separates  this  bone  in  such  a  manner  that  the 
tendon  of  the  gastrocnemius  always  remains  nearly  perpendicular  on  the  lever  arm — no  matter 
to  what  degree  the  hock  may  be  open  or  closed.   But  this  mechanism  may  perhaps  be  disputed. 


CHAPTER  III. 
THE   ARTICULATIONS  IN   BIRDS. 

The  study  of  the  articulations  in  birds  will  only  arrest  us  for  a  few  moments  ;  as 
it  will  be  confined  to  some  remarks  on  the  intervertebral  occipito-atloid  and 
temporo-maxillary  joints,  the  only  ones  exhibiting  a  special  conformation  worthy 
of  attention. 

Intervertebral  articulations. — The  great  mobility  of  the  neck  of  Birds  is  not 
only  due  to  the  fact  of  its  length,  relati^'ely  considered,  but  also  to  the  peculiar 
manner  in  which  the  vertebrae  of  this  portion  of  the  spine  are  articulated.   It  will 


226  THE  ARTICULATIONS. 

be  remarked  that  these  do  not  unite  by  their  bodies  in  the  form  of  a  continuous 
series  of  amphiarthroses,  as  in  the  domesticated  Mammals  ;  but  that,  instead  of 
these  mixed  articulations,  there  are  real  diarthroses,  which  may  be  included  in  the 
class  created  by  Cruveilhier  under  the  title  of  articulation  hij  reciprocal  ball-and- 
socket — each  vertebra  becoming  connected  with  the  adjacent  vertebra  by  means  of 
facets,  convex  in  one  sense  and  concave  in  the  sense  perpendicular  to  the  firat. 
These  facets  are  manifestly  covered  by  cartilage  of  incrustation  ;  and  it  appears 
that,  instead  of  their  being  applied  dii'ectly  against  the  opposite  facets,  which 
present  a  precisely  inverse  conformation,  they  are  separated  by  an  extremely  thin 
fibro-cartilaginous  disc,  which  resembles  the  interosseous  meniscus  of  the  temporo- 
maxillary  articulation  in  the  Carnivora  of  the  Cat  species.  Two  loose  synovial 
capsules,  separated  by  this  interarticular  lamina,  complete  the  framework  of  each 
articulation,  and  favour  the  play  of  the  vertebrae  on  one  another.  This  arrange- 
ment has  only,  so  far  as  we  are  aware,  been  observed  in  the  Swan,  and  that  very 
imperfectly  ;  but  it  probably  belongs  to  the  entire  class  of  Birds,  for  until  now 
we  have  met  with  it  in  all  the  individuals  submitted  to  examination. 

In  its  dorso-lumbar  and  sacral  portion,  the  spine  is  a  single  piece,  in  con- 
sequence of  the  consolidation  of  the  vertebrae,  and  does  not  show  any  proper 
articulations. 

In  the  coccygeal  region,  the  mobility  of  the  spine  reappears,  but  it  is  far 
from  being  so  marked  as  in  the  cervical  region  ;  the  vertebrae  here  are  united  by 
amphiarthrosis,  and  not  by  reciprocal  ball-and-socket. 

Occiinto-atloid  articulation. — It  has  been  shown  that  there  is  only  one  more  or 
less  spheroidal  condyle  of  the  occipital  bone,  and  a  single  cavity  on  the  anterior 
margin  of  the  spinal  canal  of  the  atlas.  The  occipito-atloid  articulation  is  there- 
fore a  true  enarthrosis,  with  varied  and  very  extensive  movements — a  disposition 
which  accounts  for  the  facility  with  which  Birds  can  pivot  their  heads  on  the 
superior  extremity  of  the  vertelbral  stalk. 

Temporo-maxillary  articulation. — The  play  of  this  articulation  offers  one  pecu- 
liarity, in  that  it  causes,  during  the  separation  of  the  mandibles,  not  only  the 
depression  of  the  inferior,  but  also  the  elevation  of  the  superior  mandible.  The 
arrangement  which  permits  this  movement  has  been  already  alluded  to  (p.  189)  ; 
but  yet  it  is  difficult  to  understand,  because  there  is  no  active  agent,  no  proper 
muscle  to  directly  effect  it.  Nevertheless,  the  mechanism  which  executes  it  is 
most  simple,  and  may  be  given  in  a  few  words.  Thus,  we  know  that  the  square 
bone,  interposed  between  the  temporal  and  maxillary  bones,  like  the  interarticular 
meniscus  of  Mammals,  is  united  outwardly  with  the  malar  bone,  and  inwardly 
with  the  pterygoid.  We  know  also  that  the  latter  rests,  by  means  of  a  diarthrodial 
facet,  on  the  body  of  the  sphenoid,  and  that  it  abuts  against  the  posterior  extremity 
of  the  palatine  bones  (Fig.  109) ;  while  the  first,  the  zygomaticus,  is  joined 
directly  to  the  supermaxillary  bone.  The  upper  jaw,  it  is  also  known,  is  movable 
on  the  cranium,  because  of  the  flexibility  of  the  cartilages  or  bony  plates  uniting 
these  two  portions  of  the  head.  It  may  then  be  added,  that  the  square  bone 
receives  on  its  anterior  process  one  or  two  small  muscles,  which  are  attached  to 
the  base  of  the  cranium,  and  that  these  bones  may  be  pushed,  or  rather  drawn 
forward,  by  the  contraction  of  these  muscles.  It  is  this  projecting  or  pushing, 
transmitted  to  the  upper  mandible  through  the  medium  of  the  malar  bone  on  the 
one  side,  and  the  pterygoid  bone  on  the  other,  that  produces  the  elevation  of  that 
mandible.  Nothing  is  easier  than  to  prove  it ;  it  is  only  necessary  to  take  the 
head  of  a  Bird,  denude  it  of  all  its  soft  parts,  and  press  with  the  fingers  behind 


GENERAL   CONSIDERATIONS  ON  TEE  STRIPED  MUSCLES.  227 

the  two  square  bones,  to  imitate  the  action  of  the  elevator  muscles  ;  we  then  see 
the  internal  extremity  of  the  pterygoid  bone  glide  on  the  facet  of  the  sphenoid, 
and  push  before  it  the  palatine  bone,  during  which  the  zygomatic  bone  acts  in  the 
same  manner  on  the  maxillary  ;  and  in  this  way  is  produced,  through  the  influence 
of  this  postero-anterior  propulsion,  the  ascending  movemeijit  we  undertook  to 
explain. 


THIED    SECTION. 

The  Muscles. 

After  the  study  of  the  bony  levers  and  their  articulations,  comes  the  description 
of  the  agents  whose  function  it  is  to  move  them.  These  are  the  muscles — fibrous 
organs  possessing  the  property  of  contracting  under  the  influence  of  a  stimulus. 

They  are  distinguished  as  striped  or  striated,  and  smooth  or  non-striated 
muscles,  according  to  the  character  of  the  anatomical  element  composing  them. 

The  striped  muscles  differ  from  the  smooth,  in  that,  with  the  exception  of 
the  tissue  of  the  heart,  their  contractile  power  is  immediately  placed  under  the 
influence  of  the  will.  They  are  more  particularly  concerned  in  the  functions  of 
relation,  which  cause  them  to  be  also  named  the  external  muscles,  or  muscles 
of  animal  life.  These  muscles  are  nearly  all  attached  to  the  skeleton,  and  are 
the  active  agents  in  moving  the  bony  framework  ;  they  will,  therefore,  be  the 
only  ones  referred  to  in  this  place,  in  studying  the  locomotory  apparatus. 

The  unstriped  muscles  are  removed  from  the  influence  of  the  will,  and  belong 
to  the  organs  of  vegetative  life.  They  are  also  designated  internal  muscles^ 
involuntary  muscles,  or  muscles  of  orgastic  life. 

But  before  entering  upon  the  particular  description  of  each  muscle,  we  will 
allude  to  the  general  considerations  relating  to  their  history. 


CHAPTER   I. 

GENERAL   CONSIDERATIONS   ON   THE    STRIPED   MUSCLES. 

THE    STRIPED    MUSCLES    IN     GENERAL. 

In  this  first  paragraph,  we  will  survey,  in  a  general  manner,  the  volume,  situation, 
form,  direction,  attachments,  relations,  and  names  of  the  muscles  belonging  to 
the  locomotory  apparatus. 

A.  Volume. — Nothing  is  more  variable  than  the  volume  of  the  external 
muscles.  What  a  difference  there  is,  for  example,  between  the  small  scapulo- 
humeralis  muscle  and  the  biceps  femoris  or  longissimus  dorsi,  and  what  a 
number  of  intermediate  sizes  between  these  three  points  of  comparison  !  There 
are  consequently  very  great,  great,  medium,  small,  and  very  small  muscles. 

The  weight  of  the  total  mass  of  these  organs  varies  according  to  the  species. 


228  THE  MUSCLES. 

age,  sex,  and  state  of  health ;  but  on  taking  a  general  average,  it  will  be  found 
that  it  represents  nearly  one-half  the  entire  weight  of  the  body. 

B.  Situation. — There  is  no  need  to  insist  upon  the  fact,  that  a  knowledge 
of  the  situation  of  the  muscles  is  one  of  the  firet  objects  to  be  acquired  with 
regard  to  their  arrangement. 

They  may,  like  the  bones,  be  described  in  two  ways. 

1.  In  relation  to  the  median  plane  of  the  body ;  whence  their  division  into 
pairs  and  single  muscles.  The  last,  very  few  in  number,  are  far  from  exhibiting 
the  symmetry  which  exists  in  the  bones  of  the  same  order,  as  may  be  seen  in  the 
diaphragm. 

2.  In  relation  to  the  other  organs ;  such  as  the  bones  and  surrounding 
muscles. 

C.  FoEM. — With  regard  to  their  absolute  form,  the  muscles,  again,  like  the 
bones,  are  classed  as  long,  wide,  and  short. 

Long  muscles. — These  muscles  are  more  particularly  met  with  in  the  limbs. 
Provided  with  a  principal  axis,  to  which  we  may  ascribe  the  effect  of  their 
contraction,  they  present  a  middle  portion — usually  thick,  and  tivo  extremities  of 
unequal  thickness  ;  the  most  voluminous,  always  turned  upwards,  is  metaphori- 
cally designated  the  head,  the  other  the  tail.  They  are  most  frequently  /i<s?/o/7«, 
sometimes  conical,  but  rarely  cijlindrical,  prismatic,  ov  flattened  into  thin  bands. 

Thus,  as  Bichat  remarked  a  long  time  ago,  there  are  muscles  which  have  no 
other  analogy  with  the  long  muscles  of  the  limbs  than  in  their  external  appear- 
ance. These  are  the  long  muscles  lying  above  or  below  the  spine,  and  which  are 
composed  of  a  series  of  fasciculi  indistinguishable  at  their  origin  and  distinct  at 
their  termination  ;  or  fasciculi,  each  of  which  has  a  distinct  origin  or  termination 
on  the  vertebrfe. 

Wide  muscles. — Wide  muscles  are  those  which  have  two  principal  axes,  and 
are  stretched  beneath  the  skin,  or  around  the  great  cavities  of  the  trunk,  which 
they  concur  in  enclosing  and  separating  from  one  another.  They  are  ellipticaly 
quadrilateral,  triangidar,  trapezoid,  etc. 

Short  muscles. — These  are  found  chiefly  around  the  short  bones,  or  at  the 
periphery  of  the  articulations  which  are  deeply  buried  under  enormous  muscular 
masses.  Although  their  name  indicates  that  their  three  axes  offer  nearly  the 
same  dimensions,  yet  there  is  most  frequently  one,  and  even  two,  which  pre- 
dominate. They  may  therefore  be  assimilated,  in  this  respect,  to  the  long  or 
wide  muscles. 

D.  Direction. — Cruveilhier  has  justly  remarked,  that  the  direction  of  a 
muscle  is  one  of  the  most  important  features  in  its  history  ;  for  it  allows  the 
determination  of  the  angle  of  incidence  of  the  muscle  on  its  arm  of  the  lever,  its 
power,  and  its  uses. 

With  regard  to  the  direction  of  muscles,  we  may  observe  :  1.  The  form  of 
their  principal  axis.  2.  The  relation  of  this  axis  to  the  vertical  line.  3.  Its 
comparison  with  the  axis  of  the  bony  levers  which  the  muscles  surround  or  moves. 

a.  A  muscle  is  termed  rectilinear  when  its  principal  axis  is  straight ;  it  is 
curvilinear,  or  circular,  if  this  axis  describes  a  curve  more  or  less  marked  ;  it 
becomes  inflected  when  it  proceeds  in  a  certain  direction,  and  afterwards  turns 
on  a  bony  or  cartilaginous  pulley  in  another  direction — that  is  to  say,  when  its 
principal  axis  is  broken  into  several  lines.  If  the  muscle  offers  two  axes,  it  will 
\)Qflat  or  concave,  these  being  one  or  the  other,  or  straight  or  curvilinear. 

J.  With  regard  to  the  direction  of  the  muscles  to  that  of  the  plumb-line,  it 


GENERAL   CONSIDERATIONS  ON  THE  STRIPED  MUSCLES.  229 

is  either  vertical,  horizontal,  or  oblique — expressions  which  carry  their  own  definition 
and  require  no  explanation. 

c.  If  the  direction  of  the  muscles  be  compared  with  that  of  the  bones  they 
surround  and  move,  it  will  be  found  that  they  are  either  parallel  to  these  levers, 
or  form  with  them  angles  more  or  less  acute.  The  proper  direction  of  the  bones 
being  known,  it  is  sufficient  to  indicate  that  of  the  muscles  to  clearly  establish 
this  comparison.  For  instance,  in  saying  that  the  majority  of  the  muscles  of 
the  shoulder  are  oblique  from  above  to  below,  and  from  before  to  behind,  it  is 
understood  that  these  muscles  are  parallel  to  the  scapula,  and  that  their  incidence 
•on  the  humerus  takes  place  at  a  right  angle. 

E.  Attachments  or  Insertions. — This  is  undoubtedly  the  most  essential 
part  of  the  study  of  the  muscles  ;  for  with  a  knowledge  of  their  insertions,  we 
may  determine  then-  extent  and  direction,  and  even  their  relations  and  uses. 

By  the  term  attachment,  fixed  insertion,  or  „  origin,  is  meant  the  point  of  the 
muscle  which  usually  remains  fixed  while  the  muscle  itself  contracts  ;  the  attach- 
ment, movable  insertion,  or  terminatio?i  is  the  name  given  to  that  portion  which 
is  fixed  to  the  lever  displaced  by  the  muscular  contraction.  Muscles  are  fre- 
quently met  with  the  two  insertions  of  which  are  alternately  fixed  or  movable ; 
and  in  such  cases  care  is  taken  not  to  give  these  insertions  one  or  other  of  the 
•designations. 

The  fixed  insertion  is  often  confounded  with  that  of  other  muscles  ;  the 
movable  insertion  is  generally  free  and  independent. 

The  muscles  are  sometimes  directly  attached  to  the  bones  by  the  ends  of  their 
fleshy  fibres  ;  but  most  frequently  they  are  fixed  to  these  inert  levers  through  the 
medium  of  a  tendon  or  an  aponeurosis,  the  volume  of  which  is  less  considerable 
than  that  of  the  fibres.  But  for  this  arrangement,  the  surface  of  the  skeleton 
would  not  be  sufficiently  extensive  to  give  insertion  to  all  the  external  muscles. 

F.  Relations. — The  indication  of  the  relations  of  the  muscles  completes  the 
idea  of  their  situation,  and  is  of  great  importance  from  a  surgical  point  of  view. 
They  should,  therefore,  be  studied  with  all  the  precision  possible. 

The  muscles  entertain  relations  either  with  the  skin,  the  bones,  other  muscles, 
■or  with  vessels  and  nerves. 

a.  It   is   only,  properly   speaking,  the   subcutaneous   muscles — such  as   the 
panniculus  carnosus  and  the  muscles  of  the  face — which  are  really  in  inmiediate 
contact  Avith  the  skin.     The  others  are  separated  from  it  by  the  aponeurotic -^^^-^*' 
fas(^a^  which  will  be  described  as  the  appendage  of  the  muscular  system.  '''^^ 

The  superficial  muscles  are  only  related  to  the  bones  by  their  extremities. 
Those  which  are  deeply  situated  are  immediately  applied  by  their  bodies  against 
the  bones  of  the  skeleton. 

c.  The  muscles  are  related  to  each  other  in  a  more  or  less  intimate  manner. 
Sometimes  they  adhere  closely  to  one  another ;  and  at  other  times  they  are 
separated  by  interstices  filled  with  fat  or  connective  tissue,  and  which  are  generally 
traversed  by  vessels  and  nerves. 

d.  The  connections  of  the  muscles  with  the  latter  organs  sometimes  assume 
a  remarkable  character  ;  this  is  when  one  of  them  accompanies,  like  a  satellite, 
the  vascular  and  nervous  trunks  concealed  beneath  its  deep  face.  There  is  in  this 
circumstance  an  important  fact  with  regard  to  surgical  anatomy.  The  borders  of 
these  muscles  are  usually  visible  on  the  surface  of  the  region,  and  for  this  reason 
may  become  valuable  guides  in  seeking  for  important  organs  in  their  vicinity. 

G.  Nomenclature. — a.  Before  the  time  of  Sylvius,  the  muscles  had  not 


280  THE  MUSCLES. 

received  particular  names.  Since  the  days  of  Galen  they  had  been  distinguished 
by  the  numerical  epithets  of  first,  second,  third,  etc.,  to  indicate  their  place  and 
their  order  of  superposition  in  the  regions  to  which  they  belonged.  It  is  in  this 
fashion  that  they  are  designated  in  the  Italian  work  on  the  Anatomy  of  the 
Horse  by  Ruini. 

b.  Sylvius  was  the  fii*st  to  give  the  muscles  real  names  ;  and,  his  example 
being  followed  by  succeeding  anthropotomists,  the  nomenclature  ot  these  organs 
was  soon  completed.  But  no  general  view,  no  methodic  spirit,  guided  Sylvius 
and  his  successoi-s  ;  it  was  sometimes  their  form,  and  sometimes  their  direction 
(oblique,  straight,  transverse  muscles),  position  {intercostal  muscles),  uses  (adductory 
abductor  tnusctes),  etc.,  to  which  the  muscles  owed  their  names.  Bourgelat 
applied  this  nomenclature  to  the  Horse,  but  modified  it  in  many  points. 

c.  Chaussier,  stnick  by  the  imperfections  of  the  nomenclature  introduced  into 
science  by  Sylvius,  sought  to  substitute  for  it  another,  much  more  methodical. 
This  anatomist  gave  to  each  muscle  a  name  formed  by  two  words,  indicating  the 
insertions  of  the  organ.  Girard  imported  this  ingenious  idea  into  veterinary 
anatomy.  It  was  in  applying  this  nomenclatm'e  to  the  muscles  of  the  Horse 
that  he  gave  the  name  of  supra-acromio-trochanteriiis  to  the  supra-spinatns  of 
Sylvius  and  Bourgelat,  and  subscapulo-trochanterius  to  the  subscapular  of  these 
authorities.  When  two  muscles  have  the  same  attachments,  they  are  distin- 
guished by  adding  to  the  names  which  indicate  their  insertions,  another  which 
signifies  the  relative  position  or  size  of  these  organs.  Thus,  we  distinguish  the 
long  abductor  of  Bourgelat  from  the  short  abdudor,  both  of  which  would  merit 
the  name  of  scapulo-humeral,  according  to  the  nomenclature  of  Chaussier,  by 
the  epithets  of  great  scapulo-humeral  and  small  scapido-humeral.  The  binary 
nomenclature  of  Chaussier  is  a  useful  aid  to  the  memory  of  students,  for  a 
knowledge  of  the  name  of  a  muscle  implies  that  of  its  attachments  and  uses ; 
but,  nevertheless,  notwithstanding  its  advantages,  this  new  nomenclature  did  not 
supersede  the  old  one  ;  because  it  ceased  to  be  correct  when  applied  to  com- 
parative anatomy,  the  same  muscles  not  having  the  same  insertions  in  all  the  species.^ 

*  It  is  not,  however,  that  the  ancient  nomenclature  has  more  advantages  in  this  respect 
than  the  new.  What  can  be  more  improper,  for  example,  than  the  names  of  deltoid,  spleuius, 
soleus,  digastrieus,  etc.?  Do  the  muscles  which  receive  these  designations,  considered  in 
Mammals  only,  offer  in  all  species  the  form  or  the  structure  which  justifies  the  employment 
of  these  names  in  tlie  human  species?  Are  the  distiuctive  epithets  of  great,  medium,  little,, 
etc.,  given  to  many  of  them,  reasonably  applicable  in  every  case?  May  not  the  same  objectiou 
be  urged  against  tiie  majority  of  the  names  derived  from  their  uses,  complications,  etc.  ? 

No  system  of  myological  nomenclature  is  really  philosophical,  and  we  are  of  those  who 
believe  it  to  be  indispensably  necessary  to  create  one;  indeed,  we  are  inclined  to  think  tliat  it 
would  be  simple  and  easy  to  attain  this  result  in  starting  from  a  basis  the  fixity  and  invari- 
ability of  which  should  be  well  defined.  And  this  basis  is,  in  our  opinion,  already  discovered ; 
it  is  the  principle  of  connections  founded  by  E.  Geoffroy  Saint- Hilaire  in  his  immortal  Phihsophie 
Anatomique — a  principle  to  which  modern  science  certainly  owes  its  finest  conquests. 

We  are  desirous  that  the  myolngical  nomenclature  should  rest  entirely,  in  the  first  place,  on 
the  relations  of  the  muscles  with  the  bones  of  the  skeleton,  or  with  other  organs  equally  fixed  and 
very  important ;  in  the  second  place,  on  the  reciprocal  connections  of  the  muscles. 

Such  is  our  rule  ;  and  it  is  not  precisely  new,  fur  the  older  anatomists  were  often  inspired 
by  it,  though  unwittingly,  as  the  principle  on  which  it  is  founded  was  to  them  entirely 
unknown;  this  circumstance,  however,  immediately  leads  us  to  an  appreciation  of  its  value. 
For  instance,  what  could  be  happier  than  the  name  of  intorcostals  given  to  the  inuscleB' 
situated  between  the  ribs,  and  their  distinction  into  external  and  internal  ?  Here  we  have 
names  which  indicate  the  relations  of  the  muscles  tliey  designate,  with  the  portions  of  the  skeleton 
and  the  reciprocal  connections  of  these  muscles.  It  can  also  be  applied  in  an  equally  rigorous 
manner  to  every  species.     We  may  also  cite  the  supra-costals,  the  intertransverse,  the  trans- 


GENERAL   CONSIDEEATIONS  ON   THE  STRIPED  MUSCLES.  231 

In  this  work  we  will  follow  the  nomenclature  of  Bourgelat,  which  will,  how- 
ever, be  submitted  to  some  change.  But  as  the  names  given  by  Girard  are,  in 
our  opinion,  of  some  assistance  to  students,  care  will  be  taken  to  include  them  in 
the  synonymy. 

(It  only  remains  for  me  to  add  that  Chauveau's  nomenclature  will  be  followed 
as  closely  as  possible.  It  possesses  advantages  which  are  greatly  superior  to  that 
adopted  by  Percivall ;  and  as,  in  my  opinion,  the  names  and  terms  imported  into 
science  should  be  as  nearly  alike  in  all  languages  as  may  be  compatible  with  cir- 
cumstances, in  order  to  facilitate  study,  comparison,  and  reference,  I  the  more 
readily  venture  to  take  this  course.  Percivall's  nomenclature  will,  however,  be 
added  in  brackets  to  the  synonyms,  as  well  as  that  of  Leyh  and  Gurlt,  when 
occasion  appears  to  demand  it. 

Structure  of  the  Striped  Muscles. 

There  enter  into  the  structure  of  muscles  :  1.  Muscular  tissue,  properly 
so  called.  2.  Connective  tissue  in  the  form  of  deUcate  lamellse,  aponeuroses,  or 
tendons.     3.  Vessels  and  nerves. 

A.  Muscular  Tissue. — This  tissue  is  composed  of  prismatic  fasciculi,  which 
it  is  possible  to  divide  and  subdivide  into  several  smaller  and  smaller  fasciculi, 
until  the  muscular  fibre  or  primitive  fasciculus  is  reached. 

The  muscular  fibre  is  a  kind  of  irregular  cylinder,  from  O'OIO  to  0-008  milli- 
metres in  length.  It  is  sometimes  straight,  sometimes  slightly  \\Tinkled,  but 
always  striped  either  in  a  longitudinal  or  transverse  direction,  or  both  at  once  ; 
the  transverse  striae,  being  usually  more  marked,  gives  the  fibril  a  very  elegant 
scalariform  aspect. 

This  fibre  is  formed  by  an  envelope  and  contents. 

The  envelope  is  a  very  delicate,  structureless  membrane  of  an  elastic  nature, 
named  the  sarcolemma  or  myolemma  (Fig.  146).  Flat  or  oval  nuclei  in  greater 
or  less  number  can  be  seen  on  its  inner  face. 

The  contents,  or  muscular  substance,  can  easily  be  resolved  into  parallel  fibrillce, 

verse  spinous,  the  subscapularis,  the  eupra-spinatus,  the  infra-spinatus,  etc.,  as  they  are  found  in 
a  greater  or  less  marked  degree  in  identical  conditions. 

Other  muscles  have  received  names  derived  in  part  from  their  situation,  and  in  part  from 
their  volume.  These  names  are  far  from  being  as  convenient  as  the  first ;  as  may  be  judged 
from  the  following  examples  : — 

In  the  majority  of  vertebrate  animals,  there  are  three  important  muscles  situated  above 
and  behind  the  pelvis,  and  forming  the  base  of  the  croup  ;  they  have  been  designated  gluteals, 
and  this  name  is  convenient,  because  it  designates  their  situation.  But  to  distinguish  them 
from  each  other,  regard  has  been  had  to  their  volume  ;  so  that  there  is  a  great,  a  medium,  and 
a  small  gluteus.  This  is  an  error,  however,  for  the  volume  of  the  muscles  is  subject  to  the 
greatest  variations,  and  a  voluminous  muscle  in  one  species  may  be  a  very  small  one  in 
anotlier,  and  vice  versa.  The  muscle  analogous  to  the  gluteus  maximus  in  Man  has  been 
described  by  Bourgelat  as  the  minimus,  and  by  Lafosse  and  Rigot  as  the  medius.  With  regard 
to  the  gluteus  medius  of  Man,  its  representative  in  the  lower  animals  has  been  designated  as 
the  maximus  by  the  majority  of  veterinary  anatomists.  What  confusion !  And  how  easy  it 
was  to  evade  it  by  distinguishing  these  muscles,  not  by  their  volume,  but  by  their  reciprocal 
connections,  which  are  the  same  in  every  species !  Is  it  not,  indeed,  more  natural  to  substitute 
the  names  of  superficial,  middle,  and  deep  gluteals,  for  those  of  great,  etc.  ? 

The  same  remark  is  applicable  to  the  muscles  which,  in  Man,  cover  the  anterior  aspect  of 
the  chest.  Designated  in  common,  and  justly  so,  as  pectorals,  tliese  muscles  are  wrongly 
distinguished  into  great  and  little ;  for  the  last,  which  is  already  an  enormous  muscle  in  the 
smaller  Ruminants,  is  represented  in  Solipeds  by  two  considerable  muscles,  much  more 
voluminous  than  the  muscle  analogous  to  the  great  pectoral.  It  is  only  necessary,  in  this 
case,  to  change  their  names  into  superficial  and  deep  pectorals. 


232 


THE  MUSCLES. 


B,  ULTIMATE  FIBRIL  OF 
MUSCLE  (according 
TO   BOWMAN). 

C,  Muscular  fibre  more 
highly  magnified,  its 
myolemma  being  so 
thin  and  transparent 
as  to  allow  the  ulti- 
mate   fibrillae    to    be 


in  the  fresh  muscles  of  insects ;  in  the  higher  animals,  this  disassociation  into 
parallel  fibrillae  is  generally  only  possible  in  muscles  subjected  to  the  action  of 
certain  reagents.  Other  reagents  favour  the  breaking  up  of  the  fibre  into  super- 
posed discs  ;  hence  it  has  been  concluded  that  the  fundamental  element  of  the 
primitive  muscular  fibre  was  not  a  fibril,  but  a  discoid  segment  of  fibrillae,  to  which 
Bowman  gave  the  name  of  sarcous  elements  (Fig.  143). 

Bowman  considered  that  the  transverse  striae  represent  the  lines  of  union  of 
the  sarcous  elements.  But  nowadays  the  striation  of  the  fibre  is  explained  by 
the  striation  of  the  primitive  contractile  cylinder  ;  in 
fact,  each  of  these  is  divisible  into  a  series  of  thick,  dark- 
coloured,  contractile  discs,  joined  by  bright  bands  which 
play  the  part  of  a  tissue  framework  in  the  cylinder.  In 
the  majority  of  Mammals,  the  thick  discs  are  traversed  in 
their  middle  by  a  pale  streak  named  the  intermediate  band 
or  streak  of  Hensen  ;  in  the  middle  of  each  bright  band  is 
a  thin  disc  dividing  it  into  two  parts.  In  the  Invertebrata 
the  situation  is  more  complicated,  as  is  seen  in  Fig.  147. 
Kanvier  has  remarked  that  there  is,  in  the  Skate  and 
Rabbit,  pale  and  dark  striped  muscles.  The  pale  muscles 
are  recognized  by  the  predominance  of  the  transverse 
striation  and  the  rarity  of  nuclei ;  wliile  the  fibres  of  the 
dark  muscles  present,  on  the  contrary,  a  great  number  of 
nuclei  and  prevailing  longitudinal  striation.  Lavocat  and 
Arloing  have  examined  these  difl'erences  in  the  muscular 
apparatus  of  some  Fishes,  Birds  (Fowls,  Guinea-fowls), 
and  domestic  Mammals  (Dog,  Ox,  Horse),  and  their 
observations  confirm  those  of  Ranvier,  apart  from  some  secondary  differences 
special  to  the  varied  species  on  which  they  made  their  investigations. 

The  muscular  fibres  are  united  parallel  to  each  other  to  form  secondary 
fasciculi,  which  are  surrounded  by  a  connective  sheath — the  internal  pei'imysium. 
The  secondary  fasciculi  are  laid  together  to  constitute  more  voluminous  fasciculi, 

which,  in  their  turn,  form  the  entire 
muscle.  The  connective  sheath  enveloping 
the  muscle  is  named  the  external  perimy- 
sium. 

B.  Tendons  and  Aponeuroses. — 
The  tendons  are  white,  nacreous,  round, 
or  flattened  cords  fixed  to  the  extremities 
of  the  long  muscles.  They  are  composed 
of  fasciculi  of  connective-tissue  fibres, 
covered  by  a  layer  of  flat  cells  ;  they  have  a  parallel  direction,  and  are  united  to 
one  another  by  loose  connective-tissue  sheaths. 

The  elementary  fibres  succeed  the  primitive  striped  fibres  ;  the  latter  terminate 
in  rounded  extremities,  and  are  fused  to  the  fibrous  fasciculi— hollowed  into  a  kind 
of  cup — by  an  intermediate  and  very  solid  amorphous  substance. 

The  aponeuroses  belong  almost  exclusively  to  the  wide  muscles;  they  are 
foi-med  of  several  planes  of  parallel  fibres  which  are  not  intercrossed  in  their 
middle  part  ;  at  their  superficies,  however,  the  fibrous  fasciculi  are  matted  together 
in  a  more  or  less  inextricable  manner. 

It  is  very  interesting  to  study  the  mode  of  union  of  the  muscular  fibres  with 


Fis;.  146. 


MUSCULAR  FIBRE  BROKEN  ACROSS,  SHOWING 
THE  UNTORN  SARCOLEMMA  CONNECTING 
THE   FRAGMENTS. 


GENERAL   CONSIDERATIONS   ON  THE  STRIPED  MUSCLES. 


233 


the  tissue  of  the  aponeuroses  and  tendons,  as  well  as  the  reciprocal  relations  of 
these  two  parts. 

The  muscular  fibre  may  be  found  passing  in  the  same  direction  as  the  tendon, 
or  it  may  fall  upoji  the  latter  obliquely.     In  both  cases  there  is  no  insensible 


Fig.  147. 


Fig.  148.' 


TORN  MUSCULAR  FI- 
BRE :  THE  TWO 
FRAGMENTS  ARE 
HELD  TOGETHER 
BY  THE  SARCO- 
LEMMA. 

transition  between  the  muscular  fibre  and  the  fasci- 
culus of  the  fibrous  tissue  ;  on  the  contrary,  the  con- 
tractile fibre  terminates  by  a  rounded  extremity, 
which  is  buried  in  a  corresponding  depression  in  the 
tendon  or  aponeurosis.  The  union  of  the  muscular 
with  the  fibrous  tissue  appears  to  be  effected  by  means 
of  a  kind  of  amorphous  cement,  which  is  very  solid  ; 
so  much  so,  that  when  the  muscles  are  submitted  to  a 
degree  of  traction  sufficient  to  cause  a  rupture,  this 
never  happens  at  the  point  of  union. 

The  tendons  commence  sometimes  by  a  hollow 
cone,  which  receives  on  its  internal  face  the  insertions 
of  its  muscular  fibres  ;  and  sometimes  by  a  thin  point, 
often  divided,  which  is  plunged  into  the  substance  of 
the  muscle.  It  is  worthy  of  remark,  that  a  muscle 
provided  with  two  tendons  shows  the  first-named 
arrangement  at  one  of  its  extremities,  and  the  other 
at  its  opposite  extremity  ;  so  that  all  the  fibres  which 
compose  the  muscle  offer  nearly  the  same  length,  those 
which  leave  the  summit  of  the  internal  tendon  being 
fixed  to  the  bottom  of  the  hollow  cone  formed  by  the 
second  tendon,  and  so  on  reciprocally. 

Tendons  are  not  necessarily  placed  at  the  ex- 
tremities of  muscles.  Sometimes  the  muscle  is  divided  into  two  bodies  or  bellies 
by  a  middle  tendon  ;  it  is  then  named  a  digastric  muscle, 

',  *  These  figures  are  from  Renaut's  work,  Trailed' Histologie.     Just  publisiiedby  Lecrosnier, 
Paris. 


PRIMITIVE  FIBRE  OF  THE  RED 
MUSCLE  OF  A  RABBIT,  MADE 
TENSE    BY    THROBBING. 

NS,  Superficial  nuclei ;  np, 
deep  nuclei ;  n,  nuclei  in 
profile  beneath  the  sarco- 
lemma;  GS,  sarcodic  drop 
resulting  from  the  expression 
of  the  muscular  plasma,  due 
to  the  contraction  of  the 
muscle  under  the  influence 
of  alcohol ;  G,  G,  G,  proteic 
granules  from  the  muscular 
plasma, pressed  out  and  united 
beneath  the  sarcolemma,  or 
squeezed  outside  of  it. 


THE  MUSCLES. 


The  muscular  fibres  which  are  continued  by  the  fibrous  fascicuK  may  be 
divergent  or  parallel.  In  the  first  case — the  diaphragm,  for  example — the  con- 
nective fibres  run  in  the  same  direction  as  the  muscular  fibres.  In  the  second 
case  several  arrangements  may  be  observed  : 

1.  Tendons  may  pass  in  the  same  direction  as  the  muscular  fibres.     This  is  the 
most  simple  manner  (Fig.  152,  A). 

Fig.  150.' 
Fig.  149. 


PRIMITIVK  MUSCCTLAR  FIBRE  FROM 
THE  FOOT  OF  THE  LUCAN03 
STAG-BEETLE —A  COMPLICATED 
CONTRACTILE  SEGMENT,  MADE 
TENSE  BY  THE  INTERSTITIAL 
INJECTION  OF  STRONG  ALCOHOL. 

K,  Muscular  nucleus  ;  8,  sarcolem- 
ma;  SM,  limits  of  a  contractile 
segment  of  muscular  substance  ; 
DE,  limits  of  a  thick  disc  system 
enclosing  discs ;  Ep,  principal 
thick  disc  ;  Ea,  Ea,  thick  acces- 
sory discs ;  Bi,  intervening 
bright  bands  of  the  thick  discs  ; 
BC,  limits  of  the  system  of  the 
bright  band  containing — Mp, 
the  thin  principal  disc,  and  Ma, 
Ma,  the  two  thin  accessory  discs  ; 
/,  /,  /,  lines  of  longitudinal 
striation  indicating  the  limits 
of  the  fibrillar  fasciculi. 


RELATION  OF  THE  PRIMI- 
TIVE MUSCULAR  FIBRE3 
WITH  THE  TENDON  OF 
THE  STERNO  -  HYOID 
MUSCLE   OF   THE    FROG. 

F,  Ordinary  primitive 
fibres  ;  f',  muscular 
prolongation ;  T,  ten- 
don of  insertion. 


2.  Muscular  fasciculi,  passing  altogether  from  the  same  side  to  become  united 
into  a  tendinous  cord  (Fig.  152,  B  and  C),  constitute  a  semi^enmfonn  muscle. 

3.  Muscular  fasiculi  maybe  implanted  to  right  and  left  of  the  tendon,  and 
form  ^pennated  ov  penniform  muscle  (Fig.  152,  D). 

These  various  aiTangements  of  the  muscular  fibres  with  their  tendons  demon- 
strate the  necessity  of  not  confounding  the  length  of  the  fleshy  body  of  a  muscle 

'  From  Eenaut's  work  already  mentioned. 


OENEEAL  CONSIDERATIONS  ON  TEE  STRIPED  MUSCLES. 


235 


Fig.  151. 


with  the  length  of  its  fibres  ;  for  the  latter  alone  give  an  indication  of  the  possible 
degree  of  shortening  it  is  capable  of — this  shortening  being  estimated  at  one- 
fourth  the  length  of  its  contractile  fibres.  In  glancing  at  the  different  an'ange- 
ments  shown  in  Fig.  152,  it  will  be  seen  that,  with  muscles  which  have  the  same 
total  length,  that  of  the  contractile  elements  varies  within  extensive  limits. 

C.  Vessels  and  Nerves. — The  muscular 
tissue  receives  much  blood  ;  the  fibrous  tissue 
very  little.  The  arteries  are  large  and  numerous, 
and  each  is  accompanied  by  two  veins.  The 
capillary  vessels  anastomose  in  such  a  manner 
as  to  form  rectangular  meshes,  the  greatest 
diameter  of  which  is  directed  towards  the  length 
of  the  muscle. 

Ranvier  has  remarked  that,  in  the  dark 
muscles  of  the  Rabbit,  the  vascular  network  has 
varicose  formations  which  retain  a  considerable 
mass  of  blood  in  the  interior  of  the  muscles. 

The  lymphatic  vessels  of  the  muscles  are 
few  ;  they  sometimes  penetrate  their  interior  in 
following  the  capillaries ;  at  other  times  they 
remain  on  the  sm-face,  in  the  external  perimy- 
sium. The  existence  of  lymphatics  has  not  yet 
been  demonstrated  in  tendons,  aponeuroses,  or 
synovial  membranes. 

The  nerves  emanate  from  the  cerebro-spinal 
centre.  At  their  tenninal  extremity  they  offer 
a  small  enlargement,  called  by  Rouget  the  motor 
end  plate,  and  by  Doyere  and  Kiihne  the  nervous 
colline  (hillock).  It  is  admitted  that  the  motor 
tube  traverses  the  sarcolemma,  there  losing  its 
envelope  ;  and  that  the  substance  of  the  axis- 
cylinder  is  spread  over  the  surface  of  the  muscular  fibrillae  to  form  the  motor 
plate. 

Physico-chemical  Properties  of  Striped  Muscles. 

Muscles  are  soft  organs,  remarkable  for  their  more  or  less  deep-red  colour, 
which  varies  with  the  species,  and  even  with  the  age  and  health  of  animals  of  the 
same  species. 

By  desiccation,  muscles  become  hard  and  brown ;  by  repeated  washing  they 
assume  a  straw-yellow  tint. 

Muscles  are  extensible,  elastic,  and  tenacious  ;  and  their  tenacity  is  more 
marked  during  life  than  after  death. 

It  has  been  remarked  that  the  juice  impregnating  the  muscular  tissue  has  a 
marked  acid  reaction  when  extracted  from  a  muscle  which  has  been  actively  con- 
tracting. (The  fluid  or  "  muscle  plasma  "  obtained  by  pressing  flesh,  is  either 
neutral  or  slightly  alkaline.  It  soon  coagulates  and  separates  into  two  portions — 
a  semi-solid  portion,  "  myosin,"  and  the  fluid  serum  that  at  ordinary  temperatures 
quickly  acquires  an  acid  reaction.)  It  holds  in  solution  a  variable  quantity  of 
albumen,  casein,  fat,  a  little  creatine,  creatinine,  and  a  somewhat  large  proportion 
of  sarco-lactic  acid.    The  solid  substance  of  the  muscle  may  be  partly  transformed 


TRANSVERSE  SECTION  OF  FROZEN  MUS- 
CLE,   MAGNIFIED    400    DIAMETERS. 

N,  Nerve.  M,  Muscular  fibre,  sur- 
rounded by  portions  of  six  others  : 
a,  nucleus  of  the  nerve-sheath ; 
6,  nucleus  of  the  sarcolemma ;  c, 
section  of  nucleus  of  terminal  plate 
of  nerve  ;  cf,  transverse  section  of 
terminal  plate,  surrounded  by  gran- 
ular material;  e,  transverse  section 
of  muscle  nuclei ;  /,  fine  fat-drops. 
The  angular  dark  particles  are  sec- 
tions of  sarcous  elements  ;  the  clear 
intervening  spaces  represent  the 
fluid  isotropal  part  of  the  muscle 
substance. 


236  THE  MUSCLES. 

into  gelatine  by  boiling  in  water ;  but  its  largest  portion  is  a  nitrogenous  sub- 
stance, soluble  in  dilute  hydrochloric  acid,  called  myosine,  or  muscular  fibrine  ;  it 
differs  but  little  from  the  fibrine  of  the  blood. 

Physiological  Properties  of  the  Striped  Muscles. 

In  this  paragraph  will  be  discussed  the  development  of  the  muscles,  muscular 
contractility,  and  the  part  the  muscles  play  in  locomotion, 

A.  Development  of  the  Muscles. — A  muscle  is  derived  from  a  mass  of 

Fig.  152. 


T' 


ARRANGEMENT    OF   THE   FIBRES   OF   A   MUSCLE. 


153- 


M,  Body  of  a  muscle.  T,  t',  Tendon,  a,  b,  Length  of  the  body  of  the  muscle.  A,  B,  C,  D,  Various 
modes  of  arrangement  of  the  muscular  fibres.  (From  Beaunis  and  Bouchard's  Anatomiff 
descriptive.) 

embryonic  cells.  Each  cell  becomes  considerably  elongated,  and  its  nucleus 
multiplies,  the  nuclei  extending  along  the  course  of  the  fibre.  The  cellular  mem- 
brane, enormously  developed,  forms  the  sarcolemma  ;  while  the  contents  of  the  cell, 
becoming  more  dense,  divide  longitudinally,  and  give 
rise  to  the  sarcous  elements.  When  the  muscles  are 
formed,  they  grow  by  the  augmentation  in  length 
and  thickness  of  their  primitive  fibres. 

B.  Muscular  Contractility. — Muscles  pos- 
sess the  property  of  contracting  under  the  influence 
of  a  natural  or  artificial  stimulus.  Muscular  con- 
traction is  the  phenomenon  resulting  from  the  opera- 
tion of  this  property.  Muscles  in  a  state  of  contrac- 
tion are  the  seat  of  physical  and  chemical  phenomena  ; 
they  change  their  form  and  consistence,  and  produce 
a  relatively  abundant  quantity  of  carbonic  acid, 
creatinine,  and  inosinic  acid.  During  contraction,  it  has  been  remarked  that  the 
muscular  fibres  contract  by  increasing  in  volume,  like  an  india-rubber  tube  left  to 


distribution   of   CAPILLARIES 
IN   MUSCLE. 


GENERAL   CONSIDERATIONS  ON   THE  STRIPED  MUSCLES. 


237 


itself  after  being  inflated,  and  that  the  transverse  striation  becomes  much  closer  ; 
though  the  zigzag  doubling  mentioned  by  Prevost  and  Dumas  has  not  been 
observed. 

But  these  physical  and  chemical  modifications,  important  as  they  are  from  a 
physiological  point  of  view,  cannot  longer  be  dwelt  upon  here.  It  is  particularly 
important  to  speak  of  muscular  contraction. 

A  muscle  that  contracts  becomes  shortened  ;  its  two  extremities  approach  each 
other  if  they  are  free  ;  or  one  draws  near 


Fig.  154. 


rT%^^--<i-^ 


m^^'^mx 


i 


the  other  if  the  latter  is  fixed  to  an  im- 
movable point.  If  the  extremities  of  a 
muscle  are  attached  to  two  movable 
levers,  its  contraction  will  bring  about  the 
displacement  of  one  or  other  of  these  ; 
from  this  a  movement  is  produced. 

The  degree  of  shortening  of  a  muscle 
varies,  according  to  its  being  entirely 
free,  or  having  a  resistance  to  overcome. 
The  mean  limit  of  this  shortening  is 
about  one-fourth  the  length  of  the 
muscular  fibres.  From  this  it  will  be 
understood,  that  the  movement  produced 
by  the  contraction  will  be  in  proportion 
to  the  length  of  the  fibres  ;  though  in 
this  appreciation  it  will  be  necessary  to 
keep  in  mind  the  density  and  energy  of 
the  fibre,  as  well  as  the  intensity  of  the 
stimulation  which  induces  the  con- 
traction. 

As    each  fibre    represents   a  force 
independent  in  its  action,  it  results  that  the  power  of  a  muscle  may  be  inferred  by 
the  number  of  its  fibres,  or  its  volume. 

Muscles  are  often  aided  in  their  action  by  mechanical  conditions  :  such  as  the 
disposition  of  the  levers  on  which  they  act,  the  direction  of  the  muscular  fibres 
in  connection  with  these  levers,  and,  lastly,  by  the  presence  of  bands  or  elastic 
cords. 

C.  Uses  of  Muscles. — There  are  flexor,  extensor,  abductor,  adductor,  rotatory 


PORTION  OF  AN  ELEMENTARY  MUSCULAR  FIBRE, 
WITH  FOUR  DARK-BORDERED  FIBRES  (a) 
CROSSING   ITS   SURFACE. 

b,  Capillary  blood-vessel,  with  fine  nerve-fibres 
(a  few  only  of  the  transverse  markings  of  the 
muscle  are  represented);  c,  two  of  the  dark- 
bordered  nerve-fibres  passing  over  the  ele- 
mentary fibre  to  be  distributed  to  adjacent 
fibres.  This  arrangement,  in  which  a  dark- 
bordered  nerve-fibre,  distributed  to  muscle, 
divides  into  branches,  one  of  which  passes  to 
a  vessel,  while  the  other  ramifies  upon  a 
muscle,  is  frequent.     Magnified  700  diameters. 


MUSCULAR    FIBRE    IN   A   STATE   OF    CONTRACTION    IN    THE    CENTRE  ;     THE    STRI^    APPROXIMATED, 
THE    BREADTH   OF    THE    FIBRE    INCREASED,    AND     THE     MYOLEMMA     RAISED    IN    VESICLES   ON    ITS 


and  other  muscles,  for  all  the  movements  of  which  the  articulations  are  the 
centre. 

To  determine  the  uses  of  the  muscles,  it  is  sufficient  to  know  their  insertions 
and  the  mode  in  which  the  bones  furnishing  these  insertions  articulate  with  each 
other.  • 

18 


238  TEE  MUSCLES. 

For  example,  if  a  muscle  is  situated  in  an  angle  formed  by  two  bones  which 
have  a  trochlean  articulation,  it  will  be  a  Jlexar ,-  but  if  it  is  placed  behind  the 
(Summit  of  the  angle,  it  becomes  an  extensor ;  if  it  be  located  on  the  external  side 
of  an  enarthrosis,  it  is  an  abductor ;  and  when  on  the  inner  side  of  the  joint,  or 
between  it  and  the  middle  plane  of  the  body,  it  is  then  an  adductor.  A  muscle 
may  be  rolled  obliquely  round  the  joint  it  controls — in  passing,  for  instance,  from 
the  inner  face  of  one  bone  to  the  outer  face  of  another  forming  an  articulation — and 
in  such  a  case  the/ea;ors  and  extensors  become  also  rotators  if  the  diarthroses  they 
move  permit  rotation. 

Lastly,  muscles  applied  more  or  less  obliquely  on  bones  united  by  a  trochoid, 
will  pivot  one  of  the  bones  on  the  other — for  instance,  the  great  oblique  muscle 
of  the  head. 

It  is  useless  to  multiply  examples,  for,  the  principle  being  once  understood,  it 
is  easy  in  nearly  every  case  to  determine  the  uses  of  a  muscle  when  its  situation, 
and  the  number  and  kinds  of  articulations  included  between  its  insertions,  are 
known. 

The  result  of  the  contraction  of  muscles  being  influenced  by  the  form  of  their 
principal  axis,  and  the  length  and  direction  of  their  levers,  it  is  necessary  to 
briefly  examine  these  two  points  : 

1.  The  immediate  effect  of  the  contraction  of  rectilinear  muscles  is  the  approxi- 
mation of  the  bones  to  which  they  are  attached.  This  approximation  is  usually 
brought  about  by  the  displacement  of  a  single  bone — that  which  receives  the 
movable  insertion  of  the  muscle.  Sometimes,  however,  the  two  bones  move  simul- 
taneously, or  they  are  alternately  fixed  and  movable. 

The  first  result  produced  by  a  curvilinear  muscle,  is  the  straightening  of  its 
component  fibres  ;  after  which  it  may  act  on  the  bony  levers  as  do  the  rectilinear 
muscles,  if  its  contractile  power  be  not  entirely  expended.  When  a  muscle  is  quite 
circular,  its  only  action  is  to  contract  the  opening  it  circumscribes. 

With  regard  to  the  inflected  muscles,  their  action  can  only  be  estimated  from 
their  point  of  inflection  ;  they  operate  as  if  this  point  represented  their  origin  or 
fixed  insertion, 

2.  The  muscular  powers  are  submitted  to  the  statical  and  dynamical  laws 
which  govern  the  theory  of  levers ;  for  the  bones  are  only  levers  moved  by  the 
muscles. 

In  the  locomotory  apparatus  we  find  the  three  kinds  of  lever  recognized  by 
physicists.  Thus  the  head,  extended  by  the  great  complexus  muscle,  represents 
an  interfixed,  or  lever  of  the  first  class  ;  the  foot,  extended  by  the  gastrocnemius 
muscle,  offers  an  example  of  the  inter-resisting,  or  second  kind,  when  the  limb 
remains  fixed  on  the  ground  ;  lastly,  the  lower  jaw,  raised  towards  the  upper  by 
the  masseter  muscle,  forms  an  interpuissant,  or  third  kind. 

It  is  worthy  of  remark  that  the  arm  of  resistance  in  the  bony  levers  is  always 
extremely  long  ;  a  circumstance  which  favours  speed  and  the  extent  of  movement, 
but  at  the  expense  of  power. 

On  the  other  hand,  muscles  are  rarely  perpendicular  to  the  arm  of  their  levers — 
at  least  at  the  commencement  of  their  action ;  a  second  circumstance  which 
diminishes  their  energy. 

Appendages  of  the  Muscles. 

These  are  :  1.  The  enveloping  or  containing  aponeuroses.  2.  The  serous  or 
mucous  hursse.     3.  The  tendinous  and  synovial  sheaths. 


GENEBAL    CONSIDERATIONS   ON   TEE  STRIPED  MUSCLES.  239 

A.  Containing  Aponeukoses. — These  are  layers  or  fascia  of  white  fibrous 
tissue,  which  envelop,  in  common,  all  the  muscles  of  one  or  several  adjoining 
regions — principally  those  of  the  inferior  bones  of  the  limbs,  where  they  constitute 
a  kind  of  hollow  cylinder. 

The  aponeuroses  are  formed  of  very  resisting  interwoven  fibres,  which  are 
attached  to  the  bones  at  numerous  points.  At  their  periphery  they  receive  the 
insertion  of  one  or  several  muscles,  which  keep  them  more  or  less  tense.  Their 
external  face  is  in  contact  with  a  thin  connective-tissue  layer  that  separates  them 
from  the  skin.  The  internal  face  sends  lamellar  prolongations  between  the 
muscles,  which  enclose  these  in  special  sheaths. 

The  aponeuroses  maintain  the  muscles  in  their  position,  and  sustain  them 
during  their  contraction. 

B.  Sekous  Burs^. — The  serous  or  mucous  bursae  are  small  cavities,  filled 
with  a  serous  fluid,  which  are  met  with  at  those  points  where  the  muscles  glide 
over  resisting  surfaces.  They  are  generally  orbicular  or  circular,  and  their  interior 
is  often  divided  by  fibrous  bands. 

Their  walls  are  formed  by  slightly  condensed  connective  tissue,  and  may  be 
lined  by  a  pavement  epithelium ;  in  which  case  it  is  believed  that  the  serous 
bursa  is  produced  by  the  simple  dilatation  of  one  of  the  connective-tissue  meshes. 

They  become  much  enlarged  when  pressure  or  friction  is  great  at  the  points 
where  they  are  situated.  They  may  appear  in  any  region,  when  the  conditions 
which  preside  at  their  physiological  development  are  accidentally  produced. 

C.  Tendinous  Sheaths  and  Synovial  Membranes. — Tendinous  sheaths  is 
the  name  given  to  the  half-bony,  half-fibrous,  sometimes  exclusively  fibrous, 
gliding  grooves  in  which  tendons  play  when  they  are  inflected  to  change  their 
direction,  or  when  they  glide  over  movable  articulations. 

The  tendinous  synovial  sheaths  are  serous  membranes  lining  the  tendinous 
sheaths,  and  covering  the  tendons  at  the  points  where  these  two  parts  are  in  con- 
tact.    They  secrete  a  synovial  fluid  quite  like  that  of  the  articulations. 

When  they  almost  completely  envelop  the  tendon,  and  are  afterwards  carried 
to  the  walls  of  the  sheath,  they  are  termed  vaginal. 

Their  walls  are  composed  of  :  1.  A  very  fine  connective-tissue  membrane, 
confounded  on  its  external  face  with  the  tendinous  sheath,  by  the  other  face  with 
the  tendon.  2.  A  simple  layer  composed  of  pavement  epithelium,  extended  over 
the  whole  or  a  part  of  the  internal  face  of  the  membrane. 

Manner  of  Studying  the  Muscles. 

A.  Classification. — To  facilitate  the  study  of  the  muscles,  two  methods  may  be  employed 
in  grouping  them.  The  first  consists  in  classifying  them  according  to  their  uses ;  describing, 
for  example,  all  the  flexors,  extensors,  etc.,  of  the  same  region.  In  the  second  method,  the  uses 
of  the  muscles  are  not  taken  into  account,  their  relations  only  being  considered  ;  and  they  are 
divided  into  groups  or  regions,  which  include  all  the  muscles  situated  around  a  bone.  The 
latter  is  the  method  now  adopted,  because  it  is  the  most  convenient,  useful,  and  rational. 

B.  Preparation. — We  will  limit  ourselves  to  some  general  remarks  on  the  following 
points : — 

Choice  of  a  mibject. — If  there  is  for  disposal  a  certain  number  of  subjects  from  among  which 
it  is  possible  to  make  a  selection,  the  preference  should  be  given  to  those  which  have  the  mus- 
cular system  best  developed;  not  that  large,  soft,  lymphatic  Horses  with  enormous  masses  of 
muscle  should  be  chosen,  for  these  animals  are  always  less  convenient  than  small  or  middle- 
sized,  well-bred  Horses.  Asses  and  Mules,  when  very  emaciated,  answer  well  for  the  prepara- 
tion of  the  muscles. 

Position  of  the  subject. — It  is  necessary  to  place  the  subject,  immediately  after  death,  in  a 
convenient  position,  in  order  that  the  cadaveric  rigidity  may  set  in  while  it  is  in  that  attituda 


240 


THE  MUSCLES. 


Without  this  precaution,  the  various  parts  of  the  body  may  assume  an  inconvenient  shape  oi 
direction,  and  all  attempts  to  amend  them  will  prove  almost  unavailing,  particularly  in  the 
larger  animals. 

Three  principal  positions  may  be  given  to  subjects: 

1.  The  animal  is  in  the  first  position  when  it  is  placed  on  its  back,  the  four  extremities  in 
the  air,  and  maintained  in  that  posture  by  means  of  long  cords  passed  round  the  pasterns,  and 
fixed  to  the  movable  rings  which  terminate  the  extremity  of  the  four  bars  of  the  wheeled  table 
on  which  the  subject  is  laid.  The  head  should  be  beyond  the  end  of  the  table  and  rest  upon  a 
stool.  The  animal  should  always  be  placed  in  such  a  manner  that  the  head  be  opposite  the 
fore-part  of  the  table,  so  that  the  movements  of  the  pole  or  shaft  be  not  impeded  during  the 
displacement  of  the  apparatus.  In  order  that  the  neck  be  not  twisted  to  the  right  or  left,  in 
attaching  the  fore  limbs  tiie  subject  i-hould  be  raised  so  that  the  withers  rest  lightly  on  the 
table.  According  to  the  bulk  of  the  animal  and  the  length  of  the  bars,  the  ropes  should  be 
passed  around  either  the  pasterns,  above  the  fetlocks,  or  even  above  the  knees  (Fig.  156). 

2.  To  place  the  animal  in  the  second  position,  it  is  turned  on  the  belly,  the  two  thighs 
flexed,  the  extremities  carried  beyond  the  table,  and  the  head  fixed  between  two  bars  by  meana 

Fig.  156. 


HORSE   FIXED   IN   THE   FIRST   POSITION   ON   ONE   OF   THE   WHEELED   TABLES   IN   USE   AT  THE 
LYONS   VETERINARY   SCHOOL. 


of  a  rope  passed  under  the  zygomatic  arches;  or  better,  two  cords  with  metal  hooks  may  be 
employeil,  a  hook  being  fixed  into  each  orbital  arch,  or  through  the  skin  and  masseter  muscle 
to  beneatii  the  zygomatic  arch,  the  cords  being  tied  short  to  the  uprights  of  the  table  (Fig. 
157).  A  block  of  wood  or  small  stool  may  be  employed  to  prop  the  trunk  by  placing  it  in  the 
Bublumbar  region  (Fig.  157). 

3.  The  hubject  is  in  the  third  position  when  it  rests  on  its  side. 

Rules  to  he  observed  during  the  preparation. — 1.  By  no  means,  if  possible,  remove  the  skin 
from  the  regions  to  be  dissected  until  quite  ready  to  begin  the  dissection.  If  this  is  impossible, 
then  take  the  precaution  of  enveloping  these  regions  in  damp  cloths,  or  in  the  animal's  skin, 
to  prevent  desiccation  of  the  aponeuroses  and  tiie  superficial  muscles. 

2.  To  rlissect  a  muscle,  it  is  necessary  to  remove  the  aponeuroses  or  the  other  muscles  which 
cover  it,  the  eonnective  tissue  enveloping  it,  and  the  fat,  glands,  vessels,  and  nerves  lodged  m  the 
neigiibouring  interstices.  The  aponeuroses  should  be  removed  in  shreds  by  making  them  very 
tense  with  the  forceps,  but  without  raising  them,  and  causing  the  blade  of  tlie  scalpel  to  glide 
between  the  fibrous  and  muscular  surfaces,  keeping  it  always  parallel  to  these  two  planes.     The 


GENERAL   CONSIDERATIONS   ON  THE  STRIPED   MUSCLES.  241 

coverin-  muscles  sliould  not  be  entirely  excised,  but  ought  to  be  cut  through  tlie  middle,  across 
tbeir  fibres  and  the  euds  thrown  back  ;  in  this  way  it  is  always  pc^sible  to  replace  a  muscle 
bv  brlDcring  the  two  portions  together ;  the  study  of  its  relations  is  then  much  more  easy.  The 
cellular^issue  is  got  rid  of  by  removing  it  with  the  forceps,  and  carrying  the  edge  of  the 
scalpel  in  the  re-entering  angle  formed  by  the  cellular  layer  and  the  surface  of  the  muscle. 
This  method  also  suffices  for  removing  aponeuroses  when  they  are  slightly  adherent  to  the 
muscular  fibres.  But  when  they  give  attachment  to  these  by  their  under  face,  as  may  be 
noticed  in  the  external  scapular  aponeurosis,  it  is  necessary  to  have  recourse  to  the  method 
indicated  above.     To  remove  fat,  glands,  etc.,  scissors  will  be  found  very  advantageous. 

Order  tofolloio  in  preparing  all  the  muscles  of  the  same  subject,  so  as  to  derive  most  advantage 
therefrom  1.  Place  the  subject  in  the  first  position,  and  commence  by  studying  the  muscles  of 
the  inferior  abdominal  region.  Then  excise  them,  leaving  the  posterior  extremity  of  the 
deep  pectoral  muscle,  the  prepubic  tendon,  and  the  crural  arch  intact.  The  abdommal  cavity 
having  been  emptied  of  the  viscera  it  contains,  dissect  and  study  successively  the  diaphragm. 


Fig.  157. 


HORSE   FIXED   IN   THE   SECOND   POSITION  ON   A   WHEELED   TABLE. 


the  internal  crural  region-^xcept  the  deep  muscles-the  sublumbar  region,  the  femoral  and 
posterior  crural  regions,  the  superficial  muscles  of  the  inferior  cervical  region,  and  the  pectoral 

'^^^  2'°After  detaching  for  future  use  one  of  the  anterior  limbs,  the  animal  is  placed  in  the  second 
position,  and  one  after  another  may  be  dissected  the  muscles  of  the  ear,  those  of  the  superior 
cervical  region,  the  croup  and  costal  regions-except  the  triangularis  sterni-and  the  spinal 
region  of  the  back  and  loins.  .  ,.  .  , 

3.  The  regions  of  the  anterior  limb  may  be  prepared  at  the  same  time,  or  immediately 

*  ^I'^Separate  the  two  posterior  limbs  by  sawing  the  femurs  through  their  middle,  and  proceed 
to  the  dissection  of  the  muscles  of  the  posterior  leg  and  foot. 

5.  By  means  of  another  application  of  the  saw  across  the  middle  of  the  loms,  the  pelvis  is 
completely  isolated  for  the  preparation  of  the  coccygeal  muscles,  and  the  deep  muscles  of  the 
internal  crural  region,  nearly  as  they  are  represented  in  figures  39  and  40. 

6.  The  animal  being  placed  on  its  side,  the  pectoral  cavity  is  opened  by  sawing  through 
the  ribs  near  their  extremities  ;  on  the  two  particular  portions  thus  obtained  may  be 
studied,  in  one  part,  the  triangularis  sterai,  and  in  the  other  the  deep  muscles  of  the  inferior 


242  TEE  MUSCLES. 

cervical  region,  including  the  longus  colli  and  the  anterior  and  lateral  straight  muscles  of  the 
head. 

7.  Lastly,  tlie  head  is  disarticulated  and  the  muscles  of  this  region  are  prepared. 

The  subject  may  afterwards  serve  for  the  study  of  nearly  all  the  articulations. 

Preservation  of  the  muscles.— The  muscles  may  be  preserved  by  immersing  them  in  appro- 
priate fluids,  and  the  muscular  preparations  by  drying  them. 

A  large  number  of  liquids  preserve  muscles  from  putrefaction.  We  may  mention  alcohol ; 
a  mixture  of  alcohol  and  oil  of  turpentine;  alcohol,  water,  and  chloroform;  a  solution  of 
sulphate  of  iron,  bichloride  of  mercury,  or  arsenious  acid.  The  best  preservative  fluid,  how- 
ever, is  nitric  acid  diluted  with  water,  in  the  proportion  of  one  of  the  former  to  three  of  the 
latter.  The  acid  hardens  the  muscles  and  softens  the  connective  tissue  ;  this  allows  all  the 
interstices  to  be  completely  cleared  out,  and  even  permits  the  primitive  muscular  fasciculi 
which  have  been  concealed  by  the  white  tissues,  to  be  exposed. 

Desiccation,  after  immersion  in  a  bath  of  arsenious  acid  or  sulphate  of  iron,  causes  the 
muscles  to  become  hardened  and  distorted.  It  is  therefore  a  bad  procedure,  though  it  preserves 
the  muscles.     Steeping  in  carbolized  glycerine  is  sometimes  resorted  to. 

(A  careful  dissection  of  the  muscles,  with  regard  to  their  origin,  insertion,  action,  and 
relations,  is  of  infinite  importance  to  the  student  of  human  anatomy ;  to  the  Veterinary  Student 
it  is  no  less  important,  and  more  particularly  with  reference  to  the  muscles  of  the  limbs.  A 
correct  knowledge  of  their  situation,  attachments,  and  functions  is  often  the  only  guide  the 
Veterinary  Surgeon  can  rely  upon  in  the  diagnosis  of  those  apparently  obscure  cases  of  lameness 
whicli  are  of  such  comparatively  frequent  occurrence.  In  the  words  of  Mr.  Henry  Gray,  we 
may  repeat  that  "  an  accurate  knowledge  of  the  points  of  attachment  of  the  muscles  is  of  great 
importance  in  the  determination  of  their  action.  By  a  knowledge  of  tiie  action  of  the  muscles, 
the  surgeon  is  able  at  once  to  explain  the  causes  of  displacement  in  the  various  forms  of 
fracture,  or  the  causes  which  produce  distortion  in  the  various  forms  of  deformities,  and,  con- 
sequently, to  adopt  appropriate  treatment  in  each  case.  The  relations  also  of  some  of  the 
muscles,  especially  those  in  immediate  apposition  with  the  larger  blood-vessels,  and  the  surface 
markings  they  produce,  should  be  especially  remembered,  as  they  form  most  useful  guides  to 
the  surgeon  in  the  application  of  a  ligature  to  these  vessels"  (^Anatomy,  Descriptive  and 
Surgical). 

An  accurate  knowledge  of  the  muscular  system  is  also  of  great  service  to  the  Veterinary 
Surgeon,  in  estimating  the  value  to  be  placed  upon  the  external  conformation  presented  by 
animals  intended  for  diflferent  kinds  of  labour. 

"  In  dissecting,"  says  Mr.  Holden,  "  there  are  four  principal  objects  to  be  constantly  borne 
in  mind  by  the  student :  1st,  The  impression  on  the  memory  of  those  facts  of  general  anatomy 
taught  in  tiie  lectures.  2nd,  Tlie  study  of  those  parts  of  the  body  more  especially  concerned 
in  surgical  affections  and  operations.  3rd,  The  education  of  the  sense  of  touch,  and  of  the 
hand  in  the  use  of  instruments;  and  4th,  The  education  of  the  eye  in  the  knowledge  of  the 
several  tissues  of  the  body,  in  various  positions,  and  varying  circumstances.  .  .  .  The  education 
of  the  eye  is  a  gradual  and  tedious  process,  but  one  which  is  pretty  certain  to  be  satisfactorily 
accomplished  if  the  student  do  but  use  his  hands  properly,  and  therefore  a  few  words  on  the 
manual  part  of  dissection  may  not  be  out  of  place. 

"  First,  as  to  the  instruments  requisite  for  dissection.  A  case,  containing  six  or  eight 
scalpels,  two  pairs  of  scissors,  a  pair  of  dissecting  forceps,  a  set  of  chain-iiooks,  a  blow-pipe, 
and  a  probe,  will  enable  the  student  to  make  all  requisite  dissections,  supposing  that  he  is 
allowed  the  use  of  a  saw  and  chisel  in  the  dissecting-room.  Great  variety  exists  in  dissecting- 
cases,  both  as  to  form  and  expense,  but  so  long  as  the  instruments  themselves  are  strong  and 
good,  the  simpler  the  case  the  better.  Scalpels  for  dissection  are  made  of  two  principal  shapes  ; 
in  one,  the  edge  is  bevelled  to  the  point,  the  back  being  straight;  in  the  other,  both  back  and 
edge  are  bevelled  to  a  point  midway  between  the  two.  The  latter  form  is  preferable  for  most 
purposes.  The  blade  should  not  be  more  than  an  inch  and  a  half  long,  and  never  double 
edged  ;  but  the  material  of  which  the  handle  is  constructed  is  a  matter  of  indifference. 

"  For  all  ordinary  dissection,  it  will  be  found  most  convenient  to  hold  the  scalpel  like  a 
pen  ;  but  for  cleaning  the  fascia  off  muscles  and  following  out  small  nerves,  it  is  better  to  hold 
it  reversed,  so  that  the  back  of  the  knife  may  be  against  the  tissue  which  is  to  be  preserved. 
In  making  the  first  incision  through  the  skin  of  a  limb,  or  in  any  otlier  position  where  a  long 
incision  is  required,  the  knife  may,  with  advantage,  be  held  under  the  hand,  by  which  the 
wrist  has  more  play,  and  the  student  has  the  opportunity  of  practising  a  mode  of  holding  the 
knife  which  he  will  find  very  useful  when  operating  on  the  living  body. 

"  The  forceps  should  be  broad  at  the  extremities  and  coarsely  serrated,  so  that  it  may 
retain  a  firm  hold  on  small  portions  of  tissue.     It  is  very  important  that  the  forceps  sliould  not 


MUSCLES  OF  THE  TRUNK.  243 

be  too  strong  in  the  spring,  for  in  that  case  it  becomes  so  fatiguing  to  the  hand  that  it  is 
impossible  to  continue  its  use  for  any  lengtii  of  time.  The  forceps  should  be  held  lightly 
between  the  thumb  and  the  first  and  second  fingers  of  the  left  hand,  which  may  be  steadied  by 
resting  the  little  finger  on  a  neighbouring  part. 

"  The  chain-hooks  should  be  strong,  and  bent  in  the  direction  of  the  thickness  and  not  of 
the  breadth  of  the  steel,  as  is  sometimes  done.  These  Litter  are  very  inferior,  being  liable  to  be 
unbent  under  any  considerable  strain.  Care  should  be  taken  that  tlie  chains  are  firmly  linked, 
and  that  the  central  ring  is  sufficiently  stout  to  bear  any  force  that  may  be  applied.  The 
scissors  should  be  large  and  strong,  and  it  will  be  found  advantageous  to  have  one  curved  pair, 
which  is  very  useful  in  preparing  the  ligaments. 

"  The  student  will  do  well  to  bear  in  mind  that  he  will  probably  be  called  upon  in  after  life 
to  operate  on  the  living  body,  the  only  preparation  for  which  is  careful  dissection:  he 
should  therefore,  as  far  as  possible,  conduct  all  his  dissections  as  methodically,  and  with  as 
much  care,  as  if  operating  on  the  living  body. 

"The  student  should  bear  in  mind  that  his  manual  labour  is  only  a  part  of  his  duty,  and 
will  be  thrown  away,  unless  he  at  the  same  time  study  the  description  of  the  part  upon  which 
be  is  engaged ;  he  should  not,  therefore,  carry  the  dissection  further  than  he  can  learn  the 
description  on  the  same  day,  and  at  the  subject,  and  should,  if  possible,  re-peruse  the  description 
in  the  evening,  and  always  on  the  next  morning,  before  carrying  the  dissection  any  further.") 


CHAPTEE  II. 

THE   MUSCLES   OF   MAMMALIA  IN    PARTICULAR. 

Article  I. — Muscles  of  the  Trunk. 

Subcutaneous  Region. 

This  only  comprises  a  single  muscle,  the  /leshi/  panniculus  (panniculus  cartiosus), 
which  moves  the  skin  covering  the  trunk.  Strictly  speaking,  however,  we  may 
describe  as  dermal  muscles  all  those  which  are  attached  to  the  inner  surface  of 
the  superficial  integument — the  muscles  of  the  face,  for  example. 

Fleshy  Panniculus  (Panniculus  Carnosus). 

Preparation. — Place  the  animal  on  its  side,  and  carefully  remove  the  skin,  allowing  the 
panniculus  muscle  to  remain  on  the  subjacent  muscles.  It  may  also  be  easily  prepared  on 
the  subject  placed  in  the  first  position. 

Situation — Form — Extmt. — Situated  on  the  inner  surface  of  the  skin  covering 
the  sides  of  the  thorax  and  abdomen,  this  is  an  immense  wide  muscle,  UTegularly 
triangular  in  shape,  thin  at  its  borders,  and  thicker  in  the  middle  than  elsewhere. 

The  upper  border  corresponds  to  a  curved  line,  convex  superiorly,  and 
extending  obliquely  from  the  flank  to  the  withers.  The  inferior  border  is  carried 
horizontally  from  the  flank  to  the  posterior  border  of  the  olecranian  mass  of 
muscles,  passing  along  the  upper  margin  of  the  deep  pectoral  muscle,  which  it 
covers,  and  to  which  it  adheres  somewhat  closely.  The  anterior  border  descends 
from  the  superior  extremity  of  the  shoulder  on  to  the  muscles  of  the  forearm. 

Structure — Attachments. — The  fibres  of  this  muscle  are  directed  forwards 
for  its  posterior  two-tliirds  ;  but  on  arriving  on  the  shoulder  they  gradually 
become  vertical.  They  are  continued,  on  the  margins  of  the  muscle,  by  aponeu- 
roses which  attach  it  either  to  the  internal  surface  of  the  skin,  or  the  fibrous 
fascia  of  the  superficial  muscles. 

This  muscle  has,  besides,  a  very  remarkable  insertion  into  the  humerus,  which 


244  THE  MUSCLES. 

was  noticed  by  G-,  Cuvier,  in  his  '  Le9ons  d'Anatomie  Comparee,'  and  which 
appears  to  have  been  omitted,  at  least  so  far  as  SoHpeds  are  concerned,  in  every 
treatise  on  Veterinary  Anatomy.  The  following  is  what  we  have  often  observed 
in  this  respect  :  On  reaching  the  posterior  border  of  the  ulnar  mass  of  muscles, 
the  panniculus  divides  into  two  superposed  layers — one,  superficial,  is  carried 
to  the  muscles  of  the  anterior  limb  ;  the  other,  deep,  soon  terminates  by  an 
aponeurosis,  which  is  united  to  the  deep  pectoral  muscle,  and  is  bordered  at 
its .  upper  margin  by  a  nacrous  aponeurotic  band  that  penetrates  between  the 
thorax  and  the  muscles  of  the  arm,  to  be  fixed  to  the  small  trochanter. 

Relations. — By  its  superficial  face,  with  the  skin,  to  which  it  closely  adheres  ; 
by  its  deep  face,  with  the  latissimus  dorsi,  the  dorsal  portion  of  the  trajjezius,  the 
abdominal  tunic,  the  great  oblique  muscle  of  the  abdomen,  the  serratus  magnus, 
some  external  intercostals,  the  spur  vein,  and  the  superficial  muscles  of  the 
shoulder  and  arm. 

Action. — The  animal,  in  contracting  this  muscle,  shakes  the  whole  of  the 
cutaneous  integument  which  covers  it ;  thus  preventing  insects  from  alighting  on 
the  surface  of  the  body,  or  tormenting  by  their  bites  or  stings. 

In  the  Dog,  tlie  panniculus  carnosus  is  prolonsed  over  the  croup,  and  is  united  along  the 
dorso-lumbar  spine  to  that  of  the  opposite  side.     It  is  very  developed  in  the  Cat. 

Cervical   Region. 

This  region  comprises  all  the  muscles  grouped  around  the  cervical  vertebrae — 
muscles  which  are  conspicuous  by  their  volume,  and  the  important  part  they  play 
in  the  animal  economy.  There  are  described  a  superior  and  an  inferior  cervical 
region. 

A.  SuPERioE  Cervical,  or  Spinal  Region  of  the  Neck. 
This  includes  seventeen  pairs  of  muscles,  arranged  in  four  layers  on  each  side 
of  the  cervical  ligament,  as  follows  : — 

First  Layer. 
Cervical  portion  of  the  Trapezius. 

Second  Layer. 
Rhomboideus.    Angularis  scapulm.     Spleniv^. 

Third  Layer. 
Complexus.     Trachelo-Mastoideus. 

Fourth  Layer. 

Spinalis  or  Semispinalis  Colli.  Six  Intertransversales  Colli.  Obliquus 
Capitis  anticus  or  inferioris.  Obliquus  Capitis  posticus  or  superioris.  Rectus 
Capitis  posticus  major.     Rectus  Capitus  posticus  minor. 

These  occupy  the  triangular  space  circumscribed  by  the  upper  border  of  the 
cervical  hgament,  the  transverse  processes  of  the  vertebrae  of  the  neck,  and  the 
spinous  process  of  the  second  dorsal  vertebra. 

Preparation. — Place  the  subject  in  the  second  position,  and  dissect  in  succession  the  four 
layers  of  the  region.  To  study  the  first  layer,  which  is  formed  by  the  cervical  portion  of 
tlie  trapezius,  remove  the  skin,  connective  tissue,  and  the  fascia  covering  that  muscle  (see 
Fig.  1.59).  The  preparation  and  study  of  the  second  layer,  composed  of  tlie  rhomboideus, 
angularis,  and  splenius,  is  carried  out  in  two  stages.     In  the  first,  the  trapezium  and  the 


MUSCLES  OF  THE  TRUNK. 


245 


mastoido-humeralis  is  removed,  leaving  only  the  cervical  insertions  of  the  latter  muscle ;  then 
the  limb  is  removed  by  sawing  through  the  scapula  beneath  the  insertions  of  the  angularis 
and  serratus  magnus,  as  in  Fig.  162.  But  as  neitlier  the  cervical  or  dorsal  insertions 
of  the  splenius  are  exposed,  it  is  necessary  to  proceed  to  the  second  part  of  the  operation  by 
removing  the  rhomboideus,  angularis,  and  the  superior  extremity  of  the  shoulder.  To  prepare 
the  third  layer,  which  comprises  the  great  and  small  complexus,  it  is  sufficient  to  excise  the 
splenius,  in  following  the  direction  of  the  neck,  and  to  turn  upwards  and  downwards  the  two 
portions  of  the  muscle  (see  Fig.  162).  Lastly,  the  deep  layer — the  semispinalis  and  iutertrans- 
versalis,  oblique,  and  posterior  straight  muscles,  as  well  as  the  cervical  ligament — is 
by  removing  the  complexus  and  longissimus  dursi  muscles  (see  Fig.  162). 

First  Layer. 

Cervical  Portion  of  the  Trapezius. 


for  description  of  this  muscle,  see 


Region  of  the  Back  and  Loins. 


Second  Layer. 
Rhomboideus  (Figs.  158,  6 


162,  1,  2.) 


Synonyms. — Described  by  Bourgelat  as  two  muscles,  the  "proper  elevator  of  the  shoulder  and 
the  rhomboideus,  these  were  termed  by  Girard  the  cervico-subscapularis  and  dorso-subscapularis. 
(This  is  the  rhomboideus  longus  and  brevis  of  Percivall,  and  the  dor  so- scapular  is  and  cervico- 
euhscapularis  of  Leyh.) 

Form — Situation — Direction. — This  muscle  has  the  form  of  a  very  elongated 
triangle,  and  is  situated  at  the  inner  aspect  of  the  cervical  trapezius  and  the 

Fig.  158. 


LATERAL   VIEW  OF   THE    NECK;   SUPERFICIAL   MUSCLES. 

1,  1,  Parotid  gland  ;  2,  sterno-maxillaris,  and,  14,  its  junction  with  its  fellow  of  the  opposite  side, 
3,  4,  mastoido-humeralis,  or  levator  humeri;  5.  splenius;  6,  rhomboideus;  7,  funicular  portion 
of  the  cervical  ligament,  or  ligamentum  colli;  8,  angularis  of  the  scapula;  9,  supra-  or  antea- 
spmatus;  10,  trapezius;  11,  infra-  or  postea-spinatus ;  12,  jugular  vein;  13,  subscapulo- 
hyoideiis;  15,  trachea. 

scapular  cartilage,  beneath  the  cervical  ligament,  the  direction  of  which  it  follows. 

Structure— Attachments.— It  is  composed  of  thick  fleshy  fasciculi,  the  anterior 

of  which  are  obhque  downwards  and  backwards,  the  posterior  passing  directly 


246  THE  MUSCLES. 

downwards.  These  fasciculi  are  fixed  by  their  superior  extremity  to  the  funicular 
portion  of  the  cervical  ligament  and  the  summits  of  the  spinous  processes  of  the 
four  or  five  dorsal  vertebrae  succeeding  the  first— Jixed  insertion  ;  by  their  inferior 
extremity,  to  the  inner  aspect  of  the  scapular  cartilage,  where  the  anterior 
fasciculi  are  confounded  with  those  of  the  angularis. 

Relations. — Covered  by  the  cervical  portion  of  the  trapezius,  the  scapular 
cartilage,  and  the  alponeurosis  of  the  latissimus  doi-si  muscle,  the  rhomboideus 
covers  the  sphenius,  which  is  excavated  near  its  superior  border  for  its  reception, 
as  well  as  the  aponeurosis  of  the  sen-atus  auticus  muscle  through  the  medium  of  a 
yellow  elastic  layer. 

Action. — It  draws  the  shoulder  upwards  and  forwards. 

2.  Angularis  Scapula  (Levator  Anguli  Scapula)  (Figs.  159,  4 ;  162,  3). 

Synonyms. — Trachelo-subscapularis — Girard.  Portion  of  the  serratus  ma.gnvis—Bourgelat. 
Elevator  of  the  scapula — Cuvier.  (Anterior  portion  of  the  serratus  magnus  of  Percivall.  The 
levator  anguli  scapulx  of  Man.) 

Situation — Form — Structure. — This  is  a  very  strong  muscle,  situated  in  front 
of  the  shoulder,  triangular,  flattened  on  both  sides,  thin  at  its  superior  border, 
thick  behind  and  below,  and  almost  entirely  fleshy. 

Attachments. — It  takes  its  origin  from  the  transverse  processes  of  the  five  last 
cervical  vertebras  by  five  distinct  portions,  which  are  directed  towards  the  scapula 
in  converging  towards  each  other,  and  soon  join  to  form  a  single  muscular  body, 
which  is  inserted  into  the  internal  face  of  the  scapula,  on  its  anterior  triangular 
surface. 

Relations. — This  muscle  is  confounded  at  its  inferior  border  with  the  serratus 
magnus.  It  is  covered  by  the  cervical  trapezius,  the  mastoido-humeralis,  and  the 
small  pectoral  muscle.  It  covers  the  splenius,  the  inferior  branch  of  the  latissimus 
dorsi,  and  transversalis  costarum.  Near  its  junction  with  the  serratus  magnus,  its 
internal  face  adheres  very  closely  to  the  transverse  processes  of  the  three  first  dorsal 
vertebrae . 

Action. — It  draws  forward  the  superior  extremity  of  the  scapula,  while  the 
humeral  angle  is  carried  backwards.  If  the  shoulder  becomes  the  fixed  point,  it 
can  act  in  the  extension  or  lateral  inclination  of  the  neck. 

3.  Splenius  (Figs.  162,  4,  5  ;  163,  10). 

Synonyms. — Cervico-trachelian — Girard. 

Form — Situation. — A  considerable  muscle,  flattened  on  both  sides,  triangular, 
and  comprised  between  the  cord  of  the  cervical  ligament,  the  inferior  branch  of 
the  latissimus  dorsi,  and  the  transvei-se  processes  of  the  four  first  cervical  ribs. 

Structure. — The  splenius,  aponeurotic  only  at  its  periphery,  is  composed  of 
thick  fleshy  fasciculi  which  are  all  directed  forwards  and  upwards,  to  reach  the 
head  and  the  first  cervical  vertebrae. 

Attachments. — It  is  fixed,  by  its  posterior  border,  to  the  lip  of  the  cei*vical 
ligament  and  the  summits  of  the  spinous  processes  of  the  first  dorsal  vertebrae, 
by  means  of  an  aponeurosis  which  is  continuous  behind  with  that  of  the 
serratus  anticus,  and  confounded,  by  its  inner  surface,  with  that  of  the 
complexus.  Its  anterior  border  is  cut  into  four  or  five  digitations,  which 
constitute  the  movable  insertions  of  the  muscle.  The  superior  digitation  is 
the  widest  and  thinnest,  and  terminates  in  an  aponeurosis  (Fig.  162,  5),  which 


MUSCLES  OF  THE  TRUNK. 


247 


unites  it  to  the  mastoid  tendon  of  the  trachelo-mastoideus,  and  passes  to  the 
mastoid  crest.  The  second  joins  a  very  strong  tendon  common  to  the  splenius, 
the  trachelo-mastoideus,  and  the  mastoido-humeralis,  which  tendon  is  attached  to 
the  transverse  process  of  the  atlas  (Fig.  162,  9).  The  two  or  three  others 
are  directly  inserted  into  the  transverse  processes  of  the  third,  fourth,  and  fifth 
cervical  vertebras. 

Relations.— ThQ    splenius   is    related,   outwardly,   to   the   rhomboideus,   the 


Fig.  159. 


StrPERFICIAL   MUSCLES   OF   THE   NECK   AND   SPINAL   REGION   OF   THE    BACK    AND   LCI 

1,  Dorsal  trapezius;  2,  longissimus  dorsi ;  3,  cervical  trapezius  ;  4,  angularis  scapulae;  5,  spleniu 
6,  anterior,  or  superficial  portion  of  the  mastoido-humeralis;  7,  its  humeral  iusertion  ;  7',  its 
mastoid  insertion;  8,  the  thin  aponeurosis  uniting  this  insertion  to  the  sterno-maxillaris ;  8' 
posterior  portion  of  the  mastoido-humeralis ;  9,  its  inferior  aponeurosis  inserted  into  the  inter 
stice  of  the  long  abductor  of  the  arm;  10,  sterno-maxillaris;  11,  subscapulo-hyoideus  ;  12 
portion  of  the  cervical  panniculus;  13,  portion  of  the  great  extensor  of  the  forearm  ;  14,  posterior 
belly  of  the  long  abductor  of  the  arm  ;  15,  great  pectoral  muscle. 


angularis  scapulae,  cervical  trapezius,  and  mastoido-humeralis ;  inwardly,  to 
the  complexus  and  the  two  oblique  muscles  of  the  head  ;  by  its  inferior  border, 
to  the  superior  margin  of  the  inferior  branch  of  the  longissimus  dorsi. 

Action.— It  extends  the  head  and  neck  in  inclining  them  to  one  side.     If  the 
two  act  in  concert,  the  extension  is  direct. 


248  THE  MUSCLES. 

Third  Layer. 
4.  CoMPLEXUS  (CoMPLEXUS  Major)  (Fig.  163,  6,  7). 

/Synoni/ms.— Durso-occipitalis — Ch'rard. 

/Situation — Direction — Form. — A  powerful  muscle,  included  between  the  internal 
surface  of  the  splenius  and  the  cervical  ligament,  the  oblique  direction  of  which, 
forwards  and  upwards,  it  follows  ;  it  is  triangular,  flattened  on  both  sides, 
elongated  from  before  to  behind,  and  divided  longitudinally  into  two  unequal 
portions — a  posterior  and  anterior. 

Structure. — The  posterior  portion  (Fig.  163,  6),  the  most  considerable,  is 
aponeurotic  at  its  origin,  intersected  by  linear  fibrous  bands  which  obliquely 
cross  its  direction,  and  is  formed  of  fleshy  fibres  directed  forwards.  Those  which 
compose  the  anterior  portion  (Fig.  164,  7),  intennixed  with  some  tendinous 

Fig.  160. 


LATERAL  VIEW  OF  THE  NECK  (MIDDLE  LAYER  OF  MUSCLES). 

1,  Funicular  portion  of  the  cervical  ligament;  2,  complexus  major;  3,  complexus  minor;  4,  rectus 
capitis  posticus  major;  5,  rectus  capitis  posticus  minor;  6,  stylo-maxillaris  ;  7,  carotid  artery; 
8,  pneumogastric  nerve  and  branch  of  sympathetic;  9,  longus  colli;  10,  recurrent  nerve;  11, 
inferior  scalenus;  12,  intertransversalis  colli;  13,  incision  through  rhomboideus  and  trapezius; 
14,  trachea. 

fasciculi,  are  directed  upwards,  and  appear  to  be  inserted  into  the  preceding. 
It  is  this  difference  in  the  direction  of  the  fibres  of  the  two  portions  of  the 
complexus  which  allows  them  to  be  distinguished  from  one  another ;  the  two 
being  only  really  separated  by  an  interstice  near  their  inferior  extremity. 
Superiorly,  the  muscle  is  constricted  to  form  the  summit  of  the  elongated  triangle 
it  represents,  and  terminates  by  a  strong  tendon. 

Fixed  insertions. — The  posterior  portion  derives  its  origin  :  1.  From  the 
summit  of  the  spinous  processes  of  the  first  dorsal  vertebrae,  by  a  strong 
aponeurosis  which  is  confounded  with  that  of  the  splenius  and  the  serratus 
anticus.  2.  From  the  transverse  processes  of  the  four  or  five  dorsal  vertebrae 
which  follow  the  second,  by  as  many  aponeurotic  digitations  united  by  their 
margins.  The  anterior  portion  is  fixed  :  1.  To  the  transverse  processes  of  the 
two  first  dorsal  vertebras,  by  two  tendinous  digitations  analogous  to  those  of 


MUSCLES  OF   THE  TRUNK.  249 

the  posterior  portion.  2.  To  the  articular  tubercles  of  the  cervical  vertebrae, 
by  the  inferior  extremity  of  its  fleshy  fasciculi. 

Movable  insertion.— The  movable  insertion  of  the  great  complexus  is  effected 
through  its  superior  tendon,  which  is  fixed  to  the  posterior  face  of  the  occipital 
protuberance,  beside  the  cervical  tuberosity. 

Relations. — It  is  covered  by  the  splenius  and  the  trachelo-mastoideus.  It 
covers  the  cervical  ligament,  the  upper  branch  of  the  longissimus  dorsi,  the  semi- 
spinalis  colli,  and  the  oblique  and  posterior  straight  muscles  of  the  head.  The 
aponeurotic  digitations  which  attach  it  to  the  dorsal  transverse  processes,  are 
comprised  between  the  two  branches  of  the  longissimus  dorsi.  The  interstice 
which  separates,  inferiorly,  the  two  portions  of  the  muscle  affords  a  passage  to 
the  superior  cervical  artery. 

Action. — It  is  a  powerful  extensor  of  the  head. 

5.  Teachelo-Mastoideus  (Complexus  Minor)  (Figs.  162,  6,  7  ;  163,  8,  9). 

iSf/nonj/TKS.— Dorso-mastoideus— GiVard.    {Trachelo-mastoideus— Percivall.) 

Situation — Direction. — Situated  at  the  internal  face  of  the  splenius,  in  an 
oblique  direction  upwards  and  forwards,  this  muscle  lies  along  the  anterior  border 
of  the  complexus,  and  follows  the  inferior  branch  of  the  longissimus  dorsi,  wliich 
it  appears  to  continue  to  the  head. 

Form — Structure. — This  is  a  long  muscle,  divided  into  two  fleshy,  fusiform, 
and  parallel  portions — anterior  and  posterior — wliich  we  might  strictly  consider 
as  two  distinct  muscles.  Both  are  composed  of  successive  fasciculi,  which  become 
longer  as  they  are  superficial,  and  terminate  by  a  tendon  at  their  superior 
extremity.  The  tendon  of  the  posterior  muscle  is  flattened,  and  joins  the 
mastoid  aponeui'osis  of  the  splenius.  That  of  the  anterior  muscle  is  funicular, 
and  receives,  before  its  insertion,  a  digitation  from  the  splenius  (Fig.  163,  10), 
and  another  from  the  mastoido-humeralis  (Fig.  163,  11). 

Fixed  attachments. — The  two  fleshy  portions  have  their  fixed  insertion  in 
common  with  the  anterior  portion  of  the  great  complexus  :  1.  On  the  transverse 
processes  of  the  two  first  dorsal  vertebras,  through  the  medium  of  aponeurotic 
digitations  which  serve  as  an  origin  to  the  last-named  muscle.  2.  On  the 
articular  tubercles  of  the  cervical  vertebrae,  by  the  inferior  extremity  of  their 
component  fasciculi. 

Movable  attachments. — The  terminal  tendon  of  the  posterior  muscle  passes  to 
the  mastoid  process  of  the  temporal  bone.  The  anterior  passes  to  the  transverse 
process  of  the  atlas. 

Relations. — Outwardly,  with  the  splenius  ;  inwardly,  with  the  complexus  and 
the  oblique  muscles  of  the  head.  The  tendon  of  the  posterior  fleshy  portion  is 
covered  by  the  mastoid  aponeurosis  of  the  mastoido-humeralis. 

Action. — The  trachelo-mastoideus  inclines  to  its  side  the  head  and  upper  part 
of  the  neck.     It  also  acts  as  an  extensor  of  the  head.^ 

'  Bourgelat  has  described,  by  the  name  of  long  transversal,  the  anterior  portion  of  this 
muscle,  and  attached  it  to  the  posterior  portion  of  the  splenius.  We  do  not  know  where  to  find 
one  or  other  of  these  in  the  crude  description  of  Lafosse  and  Vitet.  Girard  considered  them, 
like  ourselves,  as  a  single  muscle,  which  he  designates  the  dorso-mastoideus.  Rigot  has  united 
them  with  the  anterior  portion  of  the  great  complexus  and  the  foremost  fasciculi  of  the  short 
transverse  muscle  (inferior  branch  of  the  longissimus  dorsi),  to  make  his  long  transversal;  in 
doing  so  he  has  only  complicated  their  description.  These  two  muscular  fasciculi  being,  to 
our  view,  exactly  represented,  the  posterior,  at  least,  by  the  complexus  minor  of  authropotomists, 


250  TBE  MUSCLES. 

Fourth  Layer. 
6.  Spinalis  oe  Semispinalis  Colli  (Fig.  161,  4). 

Synonyms.— ^hoxi  spinous — Bourgelat.  Dorso-spinalis— Gerard.  (Spinalis  colli— Percivall 
Transversali*  colli  of  Man.) 

Situation. — Between  the  complexus  and  the  cervical  ligament,  on  the  laminae 
of  the  last  five  vertebrae  of  the  neck. 

Form — Structure — Attachments. — This  muscle,  a  continuation  in  the  cervical 
region  of  that  of  the  back  and  loins,  is  generally  formed  of  five  thick  and  short 
fasciculi,  strongly  aponeurotic,  directed  forwards,  upwards,  and  inwards. 

These  fasciculi,  attached  by  their  posterior  extremities^^icff/  insertion — to 
the  five  last  articular  tubercles  of  the  cervical  region,  are  fixed  by  their  anterior 
or  superior  extremities — movable  insertion — into  the  sixth,  fifth,  fourth,  third, 
and  second  spinous  processes  of  that  region. 

Relations. — Outwards,  with  the  complexus  ;  inwards,  with  the  superior  branch 
of  the  longissimus  dorsi  and  the  cervical  ligament.  By  its  anterior  face,  with 
the  laminae  of  the  cervical  vertebrae  and  the  interlamellar  ligaments. 

Action. — An  extensor  and  flexor  of  the  cervical  spine. 

7.  Intertransversales  Colli  (Fig.  162,.  9). 

Synonyms. — Intercervicals — Girard.  (The  intertransversales  of  Man-  Not  mentioned  by 
Percivall.) 

These  are  six  small,  short,  and  very  tendinous  fasciculi,  each  of  which  is 
doubled  into  two  secondary  fasciculi,  a  superior  and  inferior.  They  are  lodged 
in  the  lateral  excavations  comprised  within  the  transverse  and  articular  processes 
of  the  cervical  vertebrse,  and  are  carried  from  one  vertebra  to  another,  except 
from  the  first  to  the  second.  Covered  by  the  cervical  attachments  of  the 
majority  of  the  muscles  of  the  neck,  they  cover  the  vertebrae  to  which  they 
are  attached,  -as  well  as  the  vertebral  arteries  and  veins,  and  the  intervertebral 
foramina.     They  incline  the  neck  to  the  side. 

8.  Obliquus  Capitis  Anticus  or  Inferioris  (Fig.  161,  7). 

Synonym, — Axoido-atloideus — Girard, 

Form — Direction — Situation. — A  short,  thick,  and  broad  muscle,  oblique 
forwards  and  outwardly,  and  applied  to  the  superior  face  of  the  two  first  vertebrae 
of  the  neck. 

Structure  and  Attachments. — Its  fibres  are  nearly  all  fleshy,  parallel  to  each 
other,  and  longer  as  they  become  superficial ;  they  are  attached  by  their  posterior 
extremityr-^cce^  insertion — to  the  external  face  of  the  spinous  process  of  the  axis, 
and  by  their  anterior  extremity — movable  insertion — to  the  superior  surface  of  the 
transverse  process  of  the  atlas. 

Relatiotis. — Outwards,  with  the  splenius,  the  complexus  and  trachelo-mas- 
toideus  ;  inwards,  with  the  atlas,  the  axis,  and  the  atlo-axoid  articulation  ;  above, 
with  the  posterior  straight  muscles  of  the  head  ;  below,  with  the  anterior  great 
straight  muscle. 

we  have  thought  it  proper  to  give  it  that  name.  With  regard  to  the  muscle  generally  termed 
the  complexus  minor  by  veterinary  anatomists,  following  the  example  of  Meckel  we  will  describe 
it  as  a  portion  of  the  rectus  capitis  anticus  major. 

(Percivall  names  Girard's  axnido-occipitalis  longus  the  "  complexus  minor,"  and  his  dorso- 
mastvideus  the  "  ti  achelo-mastoideus."  Leyh,  following  Girard,  designates  the  latter  muscle 
the  dorso-mastoideus.) 


MUSCLES  OF  THE  TRUNK. 


251 


j^ction. — It  pivots  the  atlas  on  the  odontoid  process  of  the  axis  ;  it  is,  there- 
fore, the  special  rotator  of  the  head. 

9.  Small  Oblique,  Obliquus  Capitis  Posticus  oe  Supekioris  (Fig.  161,  8). 

Synonyms. — Atloido-mastoideus — Girard.    (Obliquus  capitis  superior — Percivall.     Lateral 
atloido-occipitalis  of  Leyh.     Obliquus  superior  of  Man.) 

A  short,  thick,  quadrilateral,  and  strongly  aponeurotic  muscle.    Its  fibres  are 
fixed  posteriorly — origin — to  the  lip  bordering  the  transverse  process  of  the  atlas  ; 

Fig.  161. 


CERVICAL  LIGAMENT  AND  DEEP  MUSCLES  OF  THE  NECK. 
1,  Lamellar  portion  of  the  cervical  ligament;  2,  funicular  portion;  3,  3,  semispinales  muscles 
of  the  back  and  loins ;  4,  4,  spinales  colli ;  5,  rectus  capitis  posticus  major ;  6,  small  ditto ; 
7,  great  or  inferior  oblique  muscle  of  the  head  ;  8,  small  ditto  ;  9,  9,  intertransversales  colli ;  10, 
anterior  great  straight  muscle  of  the  head  ;  11,  inferior  portion  of  scalenus  muscle;  12,  superior 
ditto. 

they  are  carried  from  thence  forward,  upward,  and  inward,  to  be  attached — 
termination — 1.  To  the  styloid  process  of  the  occipital  bones.  2.  To  the  external 
surface  of  that  bone,  on  the  imprints  which  border  the  mastoid  crest  posteriorly. 
3.  To  the  mastoid  crest  itself.  This  muscle  is  covered  by  the  mastoid  tendon  of 
the  trachelo-mastoideus,  by  the  superior  aponeurosis  of  the  splenius,  and  that  of  the 


252  THE  MUSCLES. 

mastoido-humeralis.  It  covers  the  occipito-atloid  articulation,  the  occipital  inser 
tion  of  the  posterior  straight  muscles  of  the  head,  and  the  origin  of  the  occipito- 
styloid  and  digastric  muscles.  It  inclines  the  head  on  the  atlas,  and  shghtlj 
extends  it. 

10.  Posterior  Great  Straight  Muscle  of  the  Head  (Rectus  Capitis 
Posticus  Major)  (Fig.  161,  5). 

Synonyms.— SmaU  complexus  and  great  posterior  straight  axuscle—Bourgelat.  Long  and 
short  axoido-occi  pi  talis— Gerard.  (^Complexus  minor  and  rectus  capitis  posticus  major. — 
Perdvall.  Leyh  gives  this  muscle  the  same  designation  as  Girard.  It  is  the  rectus  capitis 
posticus  major  and  medius  of  Man.) 

Form — Structure — Situation. — Elongated,  prismatic,  easily  divisible  into  two 
fasciculi — one  superficial,  the  complexus  minor  of  Bourgelat  (and  Percivall)  ;  the 
other  deep,  th.Q  great  posterior  straight  muscle  of  Bourgelat  (and  the  rectus  capitis 
posticus  major  of  Percivall) — entirely  fleshy,  and  formed  of  parallel  fibres,  this 
muscle  is  lodged,  with  the  small  posterior  straight  muscle,  in  a  triangular  space 
circumscribed  by  the  cord  of  the  cervical  ligament  and  the  internal  border  of  the 
obUque  muscles. 

Attachments. — It  is  attached,  by  its  superior  extremity,  to  the  whole  extent  of 
the  uneven  lip  which  terminates  the  spinous  process  of  the  2ix\s,-^fixed  insertion. 
Its  anterior  extremity  is  insinuated  beneath  the  small  oblique  muscle,  and  is  fixed 
to  the  occipital  bone,  behind  the  superior  insertion  of  the  gi'eat  complexus,  the 
tendon  of  which  receives  some  of  the  fibres  of  the  superficial  fasciculus — movable 
insertion. 

Relations. — Above,  with  the  complexus  ;  below,  with  the  small  straight 
muscle ;  inwards,  with  the  cord  of  the  cervical  ligament  and  the  analogous  muscle 
of  the  opposite  side  ;  outwards,  with  the  oblique  muscles. 

Action. — This  muscle,  a  congener  of  the  complexus,  aids  in  extending  the 
head. 

11.  Posterior  Small  Straight  Muscle  (Rectus  Capitis  Posticus 
Minor)  (Fig.  161,  6). 

Synonyms. — Atloido-occipitalis — Girard.  {Rectus  capitis  posticus  minor — Percivall.  The 
Atloido-occipitalis  superior  of  Leyh.     The  rectus  capitis  posticus  minor  of  Man.) 

A  very  small,  wide,  and  triangular  muscle,  flat  above  and  below,  and  lying 
immediately  upon  the  fibrous  capsule  of  the  occipito-atloid  articulation.  It  is 
attached,  posteriorly,  to  the  superior  face  of  the  atlas — origin ;  in  front,  to  the 
external  surface  of  the  occipital  bone,  below  the  preceding  muscle,  the  action  of 
which  it  #iares. 

Differential  Characteus  in  the  Muscles  of  the  Cervical  Region  in  the  other 

Animals. 

1.  Ruminants. — In  the  Ox,  the  angularis  scapulas  arises  by  six  digitations  from  all  the 
cervical  vertebr£e  except  the  first ;  the  splenius  is  little  developed,  and  is  not  attached  to  either 
the  tliird  or  fourth  cervical  vertebra. 

In  the  Carnal,  the  angularis  scaiiulae  is  very  small,  and  does  not  go  beyond  the  fifth  cervical 
vertebra  in  front.  All  the  other  muscles  in  this  region  are  very  much  reduced  in  size.  "  If 
the  splenius  exists  in  the  Camel,  it  is  so  small  that  it  often  escapes  dissection"  (Cuvier). 

2.  Pig.— The  muscles  of  tlie  superior  cervical  region  in  this  animal  are  generally  very 
developed.  The  rhomboideus  is  divided  into  two  flesliy  bodies,  one  of  which  proceeds  to  the 
occipital  protuberance,  and  the  other  to  the  rudimentary  cervical  ligament  and  the  first  dorsal 
vertebrae.  The  angularis  is  attached,  as  in  Ruminants,  to  the  six  oerviral  vertebrae  ;  sometimes 
it  even  shows  a  digitation  that  descends  to  the  atlas.     The  splenius  only  terminates  anteriorly 


MUSCLES  OF  THE  TRUNK.  253 

by  three  fleshy  portions ;  but  they  are  voluminous,  and  are  inserted,  one  into  the  atlas,  another 
into  the  mastoid  crest,  and  tlie  third  into  the  occipital  protuberance.  In  the  complexus,  the 
two  portions  are  completely  separated  from  each  other,  except  at  their  upper  extremity,  by 
the  interspace  lodging  the  superior  cervical  artery.  The  aponeurosis  attaching  the  muscle  to 
the  spinous  processes  of  the  first  dorsal  vertebrae  is  not  confounded  with  that  of  the  spleniua 
or  the  serratus  anticus  respiratory  muscle.  The  atloidean  fleshy  body  of  the  trachelo- 
mastoideus  is  scarcely  distinct  from  the  superior  branch  of  the  iongissimmo  dorsi  and  the 
intertransversales.  Lastly,  it  is  difficult  to  distinguish  the  small  posterior  straight  muscle  from 
the  deep  fasciculus  of  tlie  great  straight  muscle. 

3.  Camivora. — In  these  animals  the  muscles  of  the  superior  cervical  region  are  nearly  all 
voluminous,  as  in  the  Pig.  The  rhomboidem  is  bifid  at  its  origin,  and  its  anterior  branch  arises 
from  the  mastoid  crest.  The  angularis  is  also  attached  to  the  last  six  cervical  vertebrse.  Very 
thick  and  broad,  the  splenius  only  passes  to  the  atlas  and  mastoid  crest.  The  oblique  and 
$traight  posterior  muscles  of  the  head  are  also  remarkably  thick. 

B.  Inferioe  Cervical  or  Trachelian  Region. 
The  muscles  composing  this  region  are  situated  in  front  of  the  cervical 
vertebrae,  and  are,  for  the  most  part,  grouped  around  the  trachea,  which  they 
envelop  as  in  a  kind  of  sheath.  They  are  eleven  in  number,  and  are  :  the  cervical 
panniculus,  mastoido-humeralis,  sterno-maxillaris,  sterno-thyro-hyoideus,  suisca- 
pulo-hyoideus,  rectus  capitis  anticus  major,  rectus  capitis  anticus  minor,  rectus 
capitis  lateralis,  scalenus,  and  the  longus  colli. 

Preparation. — 1.  Place  the  animal  in  the  first  position.  2.  Remove  the  skin  of  this  region- 
in  order  to  expose  and  study  tiie  cervical  panniculus.  3.  Remove  that  muscle  and  the  parotid 
gland  to  prepare  the  mastoido-humeralis,'  the  stylo-maxillaris,  and  sterno-thyro-hyoideus.  4. 
Transversely  cut  through  the  mastoido-humeralis  near  the  angle  of  the  shoulder,  and  isolate  it 
from  the  subscapulo-hyoideua  to  expose  this  muscle  ;  taking  care  to  preserve  the  jugular  vein 
and  parotid  gland,  in  order  to  study  their  relations  with  it.  5.  Remove  the  fore  limbs ;  open 
the  thoracic  cavity  by  sawing  through  the  eight  first  ribs  near  their  superior  extremity';  take 
out  the  viscera  contained  in  tliis  cavity,  as  well  as  the  trachea,  oesophagus,  pharynx,  and 
larynx,  to  expose  the  longus  colli,  the  scalenus,  and  the  straight  muscles  of  the  head. 

1.  Subcutaneous  Muscle  of  the  Neck  (Cervical  Panniculus) 
(Figs.  159,  12  ;  174,  1). 

Synonyms.— It  has  been  described  by  Bourgelat,  and  the  majority  of  veterinary  anatomists 
who  have  followed  him,  as  two  muscles :  the  cuticularis  of  the  neck  and  the  face.  (Percivall 
includes  this  muscle  in  his  description  of  tlie  panniculus  carnosus.  It  is  the  platysma  myoide» 
of  Man.) 

This  is  a  membraniform  expansion,  partly  fleshy,  partly  aponeurotic,  which 
covers  the  muscles  of  the  neck,  the  submaxillary  space,  and  the  face. 

The  fleshy  fibres  form,  in  front  of  the  neck,  a  thin  band,  which  is  united, 
through  the  medium  of  a  fibrous  raphe,  to  that  of  the  opposite  side.  This  band 
is  in  contact  with  the  sterno-maxillaris,  sterno-thyro-hyoideus,  and  subscapulo- 
hyoideus,  as  well  as  the  jugular  vein — enveloping  them  all  as  in  a  sort  of  furrow. 
It  gradually  becomes  thinner  from  below  upwards,  in  such  a  manner  that  around 
the  upper  part  of  the  throat  it  is  only  composed  of  some  scattered  fibres.  In  the 
submaxillary  space,  and  on  the  expanding  borders  of  the  inferior  maxilla,  the  fleshy 
fibres  appear  again  of  a  certain  thickness,  but  only  to  become  attenuated  on  the 
external  surface  of  the  cheeks. 

•  These  fleshy  fibres  leave  the  carinif orm  cartilage  of  the  sternum  ^  and  inter- 

'  The  mastoido-humeralis  may  be  dissected  at  the  same  time  as  the  trapezius,  the  subject 
being  placed  in  the  second  position.  This  conveniently  permits  the  superior  insertions  of  the 
muscle  to  be  studied  (see  Fig.  159). 

*  It  will  be  seen,  on  referring  to  Fig.  159  and  its  legend,  that  we  restore  to  the  cervical 

19 


254  THE  MUSCLES. 

mediate  middle  raphe  of  the  two  muscles,  and,  directing  their  course  outwards  and 
upwards,  soon  become  confounded  with  the  aponeurosis.  The  latter,  extremely 
thin,  is  spread  over  the  mastoido-humeralis,  the  superior  cervical  muscles,  the 
parotid  region,  and  the  cheeks,  and  is  finally  attached  to  the  zygomatic  crest.  On 
an'iving  near  the  commissure  of  the  Ups,  it  is  united  to  the  buccinator  muscle  by 
a  fleshy  fasciculus  named,  in  Man,  the  risorius  Santorini  (Fig.  163).. 

The  cervical  panniculus  braces  the  muscles  it  covers,  during  their  contraction, 
and  pulls  backwards  the  commissures  of  the  lips.  We  doubt  very  much  whether 
it  has — in  the  cervical  region  at  least — any  action  on  the  skin,  for  it  adheres  but 
very  slightly  to  its  inner  surface. 

2.  Mastoido-humeralis  (Levator  Humeri)  (Figs.  158,  160,  162,  163). 

Synonyms. — The  muscle  common  to  the  arm,  neck,  and  head — Bourgelat.  Representing 
the  cleido-mastoid,  and  the  clavicular  portions  of  the  trapezius  and  deltoid  of  Man,  and  the 
trachelo-acromialis  peculiar  to  quadruped  Mammals ' — G.  Cuvier,  Lemons  d'Anatomie  Com- 
par^e,  2iid  edition.  (This  is  the  muscle  which  Percivall  namts  the  levator  humeri.  The 
above  is  the  designation  given  to  it  by  Girard  and  Chauveau.  Leyh  gives  it  the  same  designa- 
tion as  Bourgelat.) 

Extent — Sitication — Direction — (Joynposition. — This  muscle  extends  from  the 
summit  of  the  head  to  the  inferior  part  of  the  arm,  and  is  applied  to  the  scapulo- 
humeral angle  at  the  side  of  the  neck,  in  an  oblique  direction  downwards  and 
backwards.  It  is  composed  of  two  portions  lying  longitudinally,  and  somewhat 
intimately  united,  and  distinguished  into  anterior  and  posterior. 

Form — Structure — Attachments. — A.  The  anterior  or  superficial  portion  (Fig. 
159,  6)  constitutes  a  long  fleshy  band,  which  appears  to  be  united,  by  its  anterior 
border,  to  the  cuticular  muscle  of  the  neck.  Its  superior  extremity,  thin  and  Avide, 
is  attached  to  the  mastoid  process  and  crest  by  an  aponeurosis  (Fig.  159,  71),  which 
is  united,  in  front,  to  the  tendon  of  the  sterno-maxillaris  by  a  very  thin  cellulo- 
aponeurotic  fascia.  Its  inferior  extremity,  thicker  than  the  superior,  is  inserted 
by  means  of  a  very  short  aponeurosis  into  the  humerus,  on  the  salient  border 
descending  from  the  deltoid  imprint,  and  which  limits,  in  front,  the  musculo- 
spiral  groove  on  the  body  of  that  bone  (Fig.  159,  7). 

panniculus  the  sternal  band  attributed  until  now  to  the  mastoido-humeralis.  These  are  the 
considerations  which  induce  us  to  make  this  modification :  1.  This  band  is  not  distinct  from 
the  cervical  panniculus ;  a  separation  between  the  two  muscles  can  only  be  artificially  obtained. 
2.  In  dissecting  this  band  with  care,  we  can  see  that  its  fibres,  like  those  of  the  panniculus,  are 
not  mixed  with  those  of  the  mastoido-humeralis  (superficial  portion) ;  they  pass  along  the 
external  surface  of  that  muscle,  to  which  they  intimately  adhere,  it  is  true,  but  they  can  easily 
be  separated,  and  are  continuous  with  the  aponeurosis  of  the  first. 

>  At  first  sight,  we  might  hesitate  to  admit  that  this  muscle  is  formed  of  such  varied  and 
complicated  elements  as  are  enumerated  above.  Nevertheless,  it  is  a  scientific  fact ;  and  we 
will  give  a  demonstration,  as  simple  as  it  is  clear,  that  such  is  the  case — the  idea  we  owe  to 
J.  F.  Meckel.  If  we  take  the  Dog,  for  example,  and  suppose  it  to  be  possessed  of  a  clavicle 
extending  from  the  anterior  extremity  of  the  sternum  to  the  acromion,  this  clavicle  would  bisect, 
transversely,  the  inferior  portion  of  the  mastoido-humeralis,  which  would  thus  be  divided  into 
two  portions— a  superior  and  an  inferior.  Tlie  first,  extending  from  the  clavicle  to  the  mastoid 
process,  on  this  side,  and  on  the  other  to  the  mastoid  crest,  as  well  as  to  the  cervical  ligament, 
where  it  is  confounded  with  the  trapeziiis,  would  exactly  represent  the  clavicular  portion  of  the 
latter  muscle,  and  the  cJeido-mastoideus.  With  respect  to  the  inferior  portion,  it  perfectly 
resembles,  by  its  attachments,  the  clavicular  portion  of  the  deltoid.  But,  on  the  contrary,  if 
we  suppose  Man  deprived  of  a  clavicle,  the  three  muscular  fasciculi  indicated,  in  becoming 
confounded  with  each  other,  would  form  the  mastoido-humeralis  of  the  Dog,  minus  the  posterior 
portion,  or  the  trachelo-acromialis,  which  is  not  represented  in  Man. 


MUSCLES  OF  THE  TBUNK.  255 

B.  The  posterior  or  deep  portion  (Fig.  159,  9)  is  a  second  muscular  band, 
shorter  and  stronger  than  the  preceding.  It  is  attached,  above,  to  the  transverse 
processes  of  the  first  four  cervical  vertebrae  by  as  many  fleshy  bands  (Fig.  159,  8), 
which  cover  the  superficial  portion.  The  upper  digitation,  given  off  to  the  atlas, 
is  united  to  the  tendon  common  to  the  trachelo-mastoideus  and  splenius  (Figs. 
162,  9  ;  163,  9,  10,  11).  The  inferior  extremity  of  this  portion  of  the  muscle 
widens  on  the  scapulo-humeral  angle,  which  it  envelops  in  becoming  closely  united 
to  the  anterior  portion,  terminating  with  it  on  the  humerus.  An  aponeurosis, 
which  is  confounded  with  that  of  the  trapezius,  and  sends  off  a  septum  into  the 
interstice  between  the  two  portions  of  the  long  abductor  of  the  arm,  concurs  to 
fix  this  extremity  by  spreading  over  the  muscles  of  the  arm. 

Relations. — It  is  covered,  near  its  mastoid  insertion,  by  the  parotid  gland  and 
the  cervico-auricularis  muscles  ;  for  the  remainder  of  its  extent,  by  the  aponeu- 
rosis of  the  cervical  panniculus,  from  which  it  is  separated  by  a  thin  fascia  con- 
tinuous with  that  which  extends  over  the  trapezius.  It  covers  the  splenius, 
trachelo-mastoideus,  oblique  muscles  of  the  head,  subscapulo-hyoideus  (to  which 
it  adheres  intimately),  the  digastricus,  long  flexor  of  the  head,  the  angularis, 
scalenus,  small  pectoral,  supra-  and  infra-spinatus  muscles,  the  long  abductor  of 
the  arm,  and  the  coraco-radialis. 

Action. — When  the  superior  is  the  fixed  point,  it  carries  the  entire  anterior 
limb  forward.  This  muscle,  therefore,  plays  a  very  important  part  in  locomotion, 
as  it  is  called  into  action  when  the  animal  raises  the  fore  limb  in  getting  over  the 
ground.  If  the  fixed  point  of  the  muscle  is  the  limb,  it  inclines  the  head  and 
neck  to  one  side. 

3.  Steeno-maxillaeis  (Figs.  159,  10  ;  174,  4). 
Synonym. — The  sterno-mastoideus  of  IVfon. 

Form — Structure — Situation — Direction — Attachments. — ^A  long  narrow  muscle, 
almost  entirely  fleshy,  and  terminated  at  its  upper  extremity  by  a  flattened  tendon  ; 
situated  in  front  of  the  neck,  beneath  the  panniculus,  and  parallel  to  the  anterior 
border  of  the  supei'ficial  portion  of  the  mastoido-humeralis,  from  which  it  is 
separated  by  a  space  that  lodges  the  jugular  vein ;  attached,  inferiorly,  to  the 
cariniform  cartilage  of  the  &ternnm—fix£d  insertion;  and  superiorly — movable 
insertion — to  the  curved  portion  of  the  posterior  border  of  the  maxiUaiy  bone  by 
its  terminal  tendon. 

Relations. — The  muscle  is  covered  by  the  panniculus,  and  the  parotid  gland. 
It  covers  the  trachea,  the  subscapulo-hyoideus,  sterno-thyro-hyoideus,  and  the 
maxillary  gland.  Its  external  border,  parallel  to  the  anterior  border  of  the 
mastoido-humeralis,  forms  with  it  a  longitudinal  depression  termed  the  jugular 
furroiv,  because  it  lodges  the  vein  of  that  name.  Its  inner  border  is  intimately 
united,  in  its  lower  third,  to  that  of  the  opposite  muscle. 

Action. — It  directly  flexes  the  head,  when  acting  in  concert  with  its  congener  ; 
but  alone  it  turns  it  to  one  side.  Lafosse  and  Rigot  have  wrongly  considered 
this  muscle  as  a  depressor  of  the  lower  jaw,  Bourgelat  has  correctly  stated  that 
it  cannot  move  this  jaw  independently.  (Percivall  says  that  the  pair  will  assist 
in  opening  the  mouth  ;  and  Leyh  asserts  that  when  the  mouth  is  closed,  each 
muscle  will  act  as  a  flexor  to  the  head.) 

4.  Steeno-thyeo-htoideus  (Fig.  174,  6,  7). 
Form — Structure — Situation — Attachments. — Small,  ribbon-shaped,  long,  and 


256  THE  MUSCLES. 

slender  muscle  in  two  portions  ;  digastric  ;  situated  in  front  of  the  trachea  ;  con- 
founded at  their  inferior  extremity  and  united  to  those  of  the  opposite  side,  so  as 
to  form  a  single  fasciculus  which  is  attached  to  the  cariniform  cartilage  of  the 
steTimm—flxed  insertion ;  isolated  from  each  other  above  the  tendon  which  makes 
them  digastric,  and  terminating  by  their  superior  extremity — movable  insertion : 
the  first,  on  the  inferior  surface  of  the  body  of  the  hyoid  bone  in  common  with 
the  subscapulo-hyoideus ;  the  second,  on  the  posterior  border  of  the  thyroid 
cartilage. 

Relations. — Covered  by  the  sterno-maxillaris  and  the  panniculus  muscle,  they 
cover  the  anterior  face  of  the  trachea. 

Action. — Depressors  of  the  hyoid  bone  and  larynx. 

5.  Subscapulo-hyoideus  (Figs.  159,  11 ;  174,  5). 

Synonyms. — Hyoideus — Bourgelat.    (Subscapulo-hyoideiis — Percivall.) 

Form — Structure — Situation — Direction. — This  muscle  forms  a  thin  and  wide 
band,  almost  entirely  fleshy,  oblique  forwards  and  upwards,  extending  from  the 
scapulo-humeral  angle  to  the  submaxillary  space,  and  applied  to  the  side  of  the 
trachea,  which  it  slightly  crosses. 

Attachments. — It  derives  its  fixed  insertion  from  the  inner  surface  of  the 
subscapularis,  by  an  aponeurosis  which  is  detached  from  that  covering  the  latter 
muscle.  Its  movable  insertion  is  into  the  body  of  the  hyoid  bone,  in  becoming 
confounded  with  the  sterno-thyro-hyoideus,  and  in  being  intimately  united  to  the 
muscles  of  the  opposite  side. 

Relations. — Outwardly,  with  the  subscapularis,  supra-spinatus,  small  pectoral, 
mastoido-humeralis — which  closely  adheres  to  it,  the  jugular  vein,  the  sterno- 
maxillaris,  and  the  panniculus.  Inwardly,  with  the  scalenus,  the  large  anterior 
straight  muscle  of  the  head,  the  main  trunk  of  the  carotid  artery  and  the  nei^ves 
accompanying  it,  the  trachea,  thyroid  gland,  and  the  inferior  face  of  the  larynx. 
The  jugular  vein  is  entirely  separated  from  the  carotid  artery  by  this  muscle  in 
the  upper  half  of  the  neck. 

Action. — It  is  a  depressor  of  the  hyoid  bone  and  its  appendages. 

6.  Great  Anterior  Straight  Muscle  of  the  Head  (Rectus  Capitis 
Anticus  Major)  (Figs.  161  and  162,  10  ;  163,  13). 

Synonyms. — Long  flexor  of  the  head — Bourgelat.  Trachelo-suboccipitalis — Girard.  (Rectus 
capitis  anticus  major — Percivall.     Trachelo-occipitalis — Leyh.) 

Form — Structure — Situation — Direction. — A  long,  flat  muscle,  fasciculated  in 
its  posterior  half,  terminated  in  a  tendinous  cone  at  its  anterior  extremity,  and 
passing  along  the  first  cervical  vertebrae  in  front. 

Attachments. — Behind,  to  the  transverse  processes  of  the  third,  fourth,  and 
fifth  cervical  vertebrae  by  as  many  fleshy  digitations,  the  most  inferior  of  which 
are  the  \oTige?,t— fixed  insertion.  In  front,  into  the  imprints  on  the  body  of  the 
sphenoid  bone  and  the  basilar  process,  by  its  terminal  tendon — movable  insertion. 

Relations. — Outwardly,  with  the  mastoido-humeralis,  the  subscapulo-hyoideus, 
and  the  small  anterior  straight  muscle.  Inwardly,  with  the  longus  colH  and 
the  muscle  of  the  opposite  side.  In  front,  with  the  common  carotid,  the  nerves 
accompanying  this  arteiy,  and  the  guttural  pouch,  which  lines  it  near  its  movable 
insertion.  Behind,  with  the  great  oblique  muscle  of  the  head  and  the  occipito' 
atloid  articulation. 


MUSCLES  OF  THE  TRUNK  267 

Action. — It  either  directly  flexes  the  head  or  carries  it  to  one  side,  according 
as  it  acts  alone  or  with  its  fellow  of  the  opposite  side. 

7.  Small  Anterior  Straight  Muscle  of  the  Head  (Rectus  Capitis 
Anticus  Minor). 

Synonyms. — Flexor  capitis  brevis — Bourgelat.  Atloido-suboccipitalis— Girard.  (Rectiis 
capitis  anticus  minor — Fercivall.    Atloido-oocipitalia  inferior — Leyh.) 

A  small,  entirely  fleshy,  prismatic  fasciculus,  lying  to  the  external  side  of  the 
preceding  muscle  ;  attached,  posteriorly,  to  the  inferior  face  of  the  body  of  the 
atlas  ;  in  front,  to  the  body  of  the  sphenoid  bone  and  the  basilar  process,  beside 
the  great  anterior  straight  muscle.  It  is  covered  by  the  guttural  pouch,  and 
covers  the  occipito-atloid  articulation.     It  concurs  in  flexing  the  head. 

8.  Small  Lateral  Straight  Muscle  (Rectus  Capitis  Lateralis). 

Synonyms. — Flexor  capitis  parvus — Bourgelat.  Atloido-styloideus — Girard.  (Obliqum 
capitis  anticus — Percivall.     The  rectus  capitis  lateralis  of  Man.) 

Smaller  than  the  preceding,  and  prismatic  and  entirely  fleshy,  like  it,  this 
muscle  lies  on  the  side  of  the  occipito-atloid  articulation  ;  it  is  attached  to  the 
atlas,  outside  the  small  anterior  straight  mu&cle— fixed  insertion ;  and  to  the  inner 
face  of  the  styloid  process  of  the  occipital  bone — movable  insertion.  It  is  the 
congener  of  the  two  anterior  straight  muscles  of  the  head. 

9.  Scalenus  (Figs.  161,  162,  163). 

Synonyms. — Costo-tracheleus — Girard.    (Scalenus  anticus  and  posticus  of  Man.) 

Sitimtion — Direction — Composition. — Deeply  situated  at  the  inferior  part  of 
the  neck,  in  an  oblique  direction  downwards  and  backwards,  this  muscle  com- 
prises two  portions  of  unequal  dimensions,  placed  one  above  another. 

Form — Structure — Attachments. — A  The  superior  portion  {scalenus  posticus 
of  Man),  the  smallest,  is  composed  of  three  or  four  fleshy  fasciculi,  attached  by 
their  extremities  to  the  transverse  processes  of  the  last  thi-ee  or  four  cervical 
vertebras.     The  last  terminates  at  the  superior  extremity  of  the  first  rib. 

B.  The  inferior  {scalenus  anticus  of  Man),  the  most  considerable,  is  flattened 
on  both  sides,  thick  and  wide  posteriorly,  thin  and  naiTOw  anteriorly,  and  is 
composed  almost  entirely  of  fleshy  fibres  which  are  longest  as  they  are  inferior. 
It  is  attached  :  1.  To  the  transverse  processes  of  the  last  four  cervical  vertebrae 
by  short  fasciculi  scarcely  distinct  from  one  another,  the  first  of  which  is  crossed 
by  the  last  digitation  of  the  great  anterior  straight  muscle.  2.  To  the  anterior 
border  and  external  face  of  the  first  rib,  where  all  its  fibres  end. 

Relations. — The  scalenus  responds  :  by  its  external  face,  to  the  subscapulo- 
hyoideus,  mastoido-humeralis,  and  the  deep  pectoral ;  by  its  internal  face, 
to  the  longus  colli,  trachea,  common  carotid  artery  and  its  accompanying  nerves, 
and — on  the  left  side  only — to  the  oesophagus  ;  by  its  inferior  border,  to  the 
jugular  vein.  The  two  portions  of  the  scalenus  are  separated  from  each  other,  in 
front  of  the  first  rib,  by  an  interspace  traversed  by  the  nei-ves  of  the  brachial  plexus. 

Action. — When  the  first  rib  is  the  fixed  point,  this  muscle  either  directly 
flexes  the  neck  or  inclines  it  to  one  side.  When  the  neck  is  the  fixed  point,  it 
draws  forward  the  first  rib  and  fixes  it  in  this  position  dm'ing  the  dilatation  of 
the  chest,  in  order  to  aid  the  inspiratory  action  of  the  external  intercostal  muscles. 


THE  MUSCLES. 


10.  Long  Muscle  of  the  Neck  (Longus  Colli). 

Synonyms. — Flexor  longus  colli — Bourgelat.  Subilorso-atloideus — Girard.  {Longus  colli 
— Percivcdl.     Dorso-atloideus — Leyh.) 

Situation — Composition. — A  single  and  considerable  muscle,  immediately 
covering  the  inferior  aspect  of  all  the  cervical  and  the  first  six  dorsal  vertebrae, 
and  composed  of  two  lateral  portions  which  are  united  on  the  median  line,  and 
constitute,  in  certain  animals,  two  distinct  muscles. 

Structure — Attachments. — Each  lateral  portion  of  the  longus  colli  is  composed 
of  a  succession  of  veiy  tendinous  fasciculi.  The  most  posterior  of  these  is 
attached  to  the  inferior  face  of  the  bodies  of  the  first  six  dorsal  vertebrae,  and 
proceeds  directly  forward  to  reach  the  inferior  tubercle  of  the  sixth  cervical 
vertebra,  into  which  it  is  inserted  by  a  strong  tendon.  The  other  fasciculi,  less 
considerable,  and  confounded  outwardly  with  the  intertransversales  of  the  neck, 
are  carried  from  one  cervical  vertebra  to  another,  and  are  directed  forwards, 
upwards,  and  inwards,  converging  towards  those  of  the  opposite  side.  They  are 
attached  successively  :  outwardly,  to  the  transverse  processes  of  the  last  six 
cervical  vertebrae  ;  inwardly,  to  the  inferior  ridge  on  the  bodies  of  the  first  six. 
The  most  anterior  fasciculus  passes  to  the  inferior  tubercle  of  the  atlas,  into 
which  it  is  inserted  by  a  tendon  common  to  it  and  the  fasciculus  of  the  opposite 
side,  and  which  receives  the  most  superficial  fibres  of  the  tlii-ee  or  four  preceding 
fasciculi. 

Relations. — Above  and  behind,  with  the  vertebrae  which  it  covere,  as  well  as 
their  intervertebral  discs  ;  below  and  in  front,  with  the  trachea  and  oesophagus, 
and  the  vessels  and  nerves  accompanying  these  two  tubes  ;  on  the  sides,  with  the 
great  anterior  straight  and  the  scalenus  muscles  in  its  cervical  portion  ;  and  in 
its  intra-thoracic  portion,  with  the  pleurge,  and  important  vessels  and  nei-ves. 

Action. — It'  flexes  the  whole  neck,  and  the  cervical  vertebrae  on  one  another. 

Differential  Characters  in  the  Muscles  of  the  Inferior  Cervical  Eegion  in  the 
OTHER  Animals. 

A.  Ruminants.— In  the  Ox  and  Sheep,  the  arrangement  of  the  cervical  pannicului<  oflFers 
a  very  considerable  ditference  from  tliat  observed  in  Solipeda.  The  fleshy  portion  is  absent, 
or  appears  to  be  absent,  in  the  cervical  region;  tl:e  anterior  mnscles  of  the  neck  are  only 
covered  by  a  thin  fascia  developed  on  the  sides  of  tlie  neck.  When  this  fascia  reaches  tlie 
face,  it  becomes  continuous  with  the  fleshy  fibres ;  a  fasciculus  of  these  fibres  comporis  itself 
as  in  the  Horse,  and  joins  the  buccinator:  another  is  intercrossed  in  the  maxillary  space  by 
the  analogous  fasciculus  of  the  opposite  side. 

The  cervical  panniculus  in  the  Ox  is  also  distinguished  by  an  extremely  remarkable 
peculiarity,  which  it  is  necessary  to  allude  to  here: — The  fleshy  cervical  band,  altogether 
absent  in  the  Sheep,  is  not  so  in  the  Ox;  wc  have  found  it  forming,  beneath  the  above- 
mentioned  aponeurotic  fascia,  the  hmg,  thick  strip  which  has  been  described  by  veterinary 
anatomists  as  the  analogue  of  the  sterno-maxillaris  in  the  Horse.  This  strip  is  attached,  like 
the  muscular  band  which  represents  it  in  Solipeda,  to  the  anterior  point  of  the  sternum.  But 
Us  fibres,  instead  of  being  spread  outwards  over  the  mastoido-humeralis,  ascend,  perfectly 
isolated  from  that  muscle,  to  the  posterior  border  of  the  inferior  maxilla.  There  it  terminates 
(Fig.  172,  18)  by  a  flattened  tendon,  which,  after  reaching  the  anterior  border  of  the  masseter, 
is  confounded  with  the  aponeurosis  of  that  muscle,  and  sends  some  fibrous  bands  over  the 
muscles  of  the  face. 

The  two  portions  of  the  mastoido-humeralis  of  Ruminants  are  better  defined,  and  more 
oblique  on  one  another,  than  in  the  Horse.  The  superficial  partion  receives,  on  its  inner  face, 
a  small,  bright- red,  funicular  fasciculus,  which  proceeds  from  the  cartilage  of  the  first  rib,  and 
which  Meckel  is  inclined  to  consider  as  the  vestige  of  the  subclavius.  It  is  divided,  superiorly, 
into  two  branches:  one,  the  clavicular  portion  of  the  trapezius,  very  wide,  passes  to  the  mastoid 


MUSCLES  OF  THE  TRUNK.  259 

process,  the  curved  line  of  the  occipital  bone,  and  to  the  cervical  ligament,  in  becoming  con- 
founded with  the  trapezium  (Fig.  172,  22);  the  other,  the  cleido-mastoideus,  terminates  in  a 
tendon  that  joins  the  sterno-maxillaris,  and  is  inserted  into  the  basilar  process,  after 
receiving  the  fibres  of  the  long  flexor  of  the  head  (Fig.  172,  21).  The  upper  extremity  of  the 
deep  portion  of  the  mastoido-humeralis  is  inserted  into  the  atlas  by  a  flattened  tendon  alone, 
which  is  quite  distinct  from  the  atloid  insertions  of  the  splenius  and  the  trachelo-mastoideus. 

In  the  Sheep  and  Goat,  the  costal  band  that  joins  the  superficial  portion  is  absent.  The 
latter  is  divided  at  its  inferior  extremity  into  two  branches,  between  which  pass  the  biceps. 
The  upper  branch  passes  to  the  epitrnchlea. 

The  sterno-maxillaris  muscle,  instead  of  being  inserted  into  the  inferior  maxilla,  is  united 
to  the  suboccipital  branch  of  the  mastoido-humeralis,  to  be  attached  to  the  basilar  process.  At 
another  time  we  will  discuss"  the  determination  of  this  muscle,  and  that  of  the  fleshy  band  here 
considered  as  belonging  to  the  first  (see  Spinal  Nerve). 

The  sterno-thyro-hyoid  muscle  is  thicker  than  in  the  Horse,  and  not  digastric. 

The  subscapulo-hyoideus  of  Ruminants  is  but  slightly  developed,  and  might  be  termed  the 
trachelo-hyoideus,  as  it  proceeds  to  the  transverse  process  of  the  tiiird  or  fourth  cervical 
vertebra.  In  its  passage  beneath  the  basilar  branch  of  the  mastoido-humeralis  and  sterno- 
maxillaris,  it  contracts  adhesions  with  the  fibres  of  these  two  muscles. 

The  great  anterior  straight  muscle  of  the  head  descends  to  the  sixth  cervical  vertebra.  Its 
cervical  insertions  are  covered  by  a  very  strong  muscular  fasciculus,  which  is  annexed  to  it. 
Like  it,  this  fasciculus  leaves  the  sixth  cervical  vertebra,  and  is  attached  to  the  transverse 
processes  of  the  four  vertebrae  preceding  the  last,  by  becoming  confounded  with  the  inter- 
transversales,  and  finally  terminating  at  the  tracheal  process  of  the  atlas  by  fleshy  and 
aponeurotic  fibres.  This  muscular  fasciculus  singularly  strengthens  the  neck  when  it  is 
inclined  to  one  side.  In  consequence  of  its  attachments,  it  might  be  named  the  trachelo- 
atloideus  (Fig.  172,  24). 

Lastly,  in  Ruminants  the  superior  scalenus  is  very  developed,  being  a  flattened  band  which, 
gradually  expanding,  is  prolonged  to  tlie  surface  of  the  serratus  magnus. 

B.  Pig. — In  this  animal,  tlie  cervical  panniculus  is  in  two  portions :  an  inferior,  which 
comes  from  tiie  point  of  tlie  sternum ;  and  a  superior,  from  the  external  capsular  region.  They 
unite  in  front,  and  are  prolonged  in  common  on  the  muscles  of  the  face,  contracting  adhesions 
with  the  outer  surface  of  the  body  and  branebes  of  the  inferior  maxilla. 

The  other  muscles  of  the  inferior  cervical  region  are  not  unlike  those  of  Ruminants. 

Of  the  two  portions  of  the  mastoido-humeralis,  the  superficial  is  bifid  at  its  superior 
extremity.  The  posterior  branch,  the  clavicular  portion  of  the  trapezius,  is  attached  to  the 
side  of  the  occipital  protuberance ;  the  anterior  branch,  the  cleido-mastoideus,  goes  beneath 
the  external  auditory  hiatus,  to  the  crest  that  replaces  the  mastoid  process ;  the  deep  portion 
is  attached  above  to  the  atlas  only. 

In  the  Pig,  the  fterno-maxillaris  exactly  represents  that  muscle  in  the  Horse,  as  its  tendon 
passes  directly  to  the  mastoid  process. 

The  sterno-thyro-hyoideus  is  double ;  the  supplementary  branch  going  to  the  inferior  face 
of  the  thyroideus. 

The  subscapulo-hyoideus  and  great  anterior  straight  muscle  of  the  head,  resemble  those  of 
the  Ox.  The  small  straight  lateral  muscle  is  scarcely  distinct  from  the  small  oblique.  The 
superior  scalenus  extends  to  the  third  rib.  The  two  lateral  portions  of  the  longus  colli  are 
separate,  and  form  two  distinct  muscles. 

C.  Camivora. — In  the  Dog,  each  cervical  panniculus  is  in  two  portions,  as  in  the  Pig. 
The  fibres  from  tbe  breast  are  directed  in  a  diveiging  manner  over  the  face,  the  submaxillary 
space,  and  the  parotid  gland,  where  they  form  the  parotido-auricularis  muscle.  The  portion 
coming  from  the  external  scapular  region  is  thicker  and  wider;  it  covers  the  lateral  parts  of 
the  neck,  the  parotid  gland,  the  parotido-auricularis,  passes  above  the  preceding,  and  termi- 
nates on  the  face  and  in  the  submaxillary  space,  where  its  fibres  join  those  of  the  opposite  side. 

The  mastoido-humeralis  comports  itself  somewhat  as  in  Ruminants  and  the  Pig.  The 
superficial  portion  is  bifid  superiorly ;  one  of  its  branches  is  fixed  into  the  mastoid  process — 
the  cleido-mastoideus ;  the  other  into  the  mastoid  crest  and  cervical  ligament,  in  uniting  by 
aponeurosis  with  the  trapezius— the  clavicular  portii.n  of  the  trapezius.  The  deep  portion 
passes  from  the  atlas  to  the  scapular  spine. 

The  tendon  of  the  sterno-maxillaris  goes  to  the  mastoid  process.  The  sterno-thyro-hyoideus 
Is  thick  and  not  digastric,  and  commences  from  the  cartilage  of  the  first  rib. 

The  Camivora  have  no  subscapulo-hyoideus ;  but  they  possess  a  very  long  scalenus,  which 
passes  to  the  eighth  rib,  and  a  longus  colli,  which  tends  to  become  divided  into  two  lateral 
portions. 


260  THE  MUSCLES. 

Spinal  Region  of  the  Back  and  Loins. 

This  offers  for  study  seven  pairs  of  muscles,  nearly  all  of  which  have  their 
insertions  extended  over  the  dorso-lumbar  spine,  and  are  disposed  in  four  layers 
on  each  side  of  this  long  multifidious  crest.     These  muscles  are — 

In  the  Fikst  Layer. 

Trapezim.    Latissimm  Dorsi. 

In  the  Second  Layee. 

Serratus  Anticus.     Serratus  Posticus. 

In  the  Third  Layer. 
Longissimus  Dorsi.     Transversalis  Costarum. 

In  the  Fourth  Layer. 
lis  of  Back  mid  Loins. 


Preparation. — 1.  Place  the  animal  in  the  second  position.  2.  Remove  the  skin  with  the 
panniculus  and  the  mass  of  olecranian  muscles,  to  show,  in  a  first  operation,  the  trapezius  and 
latissimus  dorsi  (Fig.  159).  3.  In  a  second  operation,  remove  the  entire  fore  limb,  with 
the  latissimus  dorsi  muscle,  the  mode  of  termination  of  which  may  then  be  studied ;  then  pre- 
pare the  two  smiiU  serrated  muscles.  4.  Remove  these  two  muscles,  as  well  as  the  angularis 
of  the  scapula  and  tlie  splenius,  to  expose  the  transversalis  costarum  and  longissimus  dorsi 
(Fig.  163).  The  superior  branch  of  the  latter  remaining  covered  by  the  great  complexus, 
excise  tliis  muscle,  leaving  only  its  insertions  into  the  transverse  processes  of  the  dorsal 
vertebrae,  to  show  how  they  are  fixed  between  the  two  branches  of  the  longissimus  dorsi.  5. 
Dissect  the  semispinalis  by  removing  the  longissimus  dorsi  and  the  internal  angle  of  the  ilium. 

First  Layer. 

1.  Trapezius  (Fig.  159,  1,  3). 

Synonym. — Dorso-  and  cervico-acromialis — Girard. 

Situation — Form — Structure. — This  is  a  superficial  membraneous  muscle, 
situated  on  the  sides  of  the  neck  and  withers.  Its  shape  is  that  of  a  triangle 
base  upwards.  It  is  aponeurotic  at  its  upper  border  and  in  its  centre,  which 
allows  it  to  be  distinguished,  especially  in  emaciated  subjects,  into  a  cervical  and 
a  dorsal  portion.  The  fleshy  fibres  of  the  first  are  directed  downwards  and  back- 
wards ;  those  of  the  second  are  oblique  forwards. 

Attachments. — By  its  superior  aponeurosis,  it  is  fixed  to  the  cord  of  the  cer- 
vical ligament  and  to  the  summits  of  the  transverse  processes  of  the  first  dorsal 
vertebrae,  where  it  adheres  to  the  external  face  of  the  latissimus  dorsi.  By  its 
central  aponeurosis  and  that  of  its  summit,  it  is  attached  to  the  tuberosity  of  the 
olecranian  spine  and  the  external  scapular  aponeurosis. 

Relations. — This  muscle  is  covered  by  two  aponeurotic  planes,  the  fibres  of 
which  cross  its  owti  at  a  right  angle.  Inwardly,  it  responds  to  the  rhom- 
boideus,  splenius,  angularis,  deep  pectoral,  the  supra-  and  infra-spinatus,  and 
the  latissimus  dorsi. 

Action. — It  raises  the  shoulder,  and  carries  it  forward  or  backward,  according 
as  one  or  other  of  its  muscular  portions  contract. 

2.  Great  Dorsal  (Latissimus  Dorsi)  (Fig.  159,  2). 

Synonyms. — Dorso-humeralis — Girard.     (Latissimus  dorsi — PercivaU.) 
Form — Situation — Structure — Attachments. — A  very  broad  triangular  muscle^ 


MUSCLES  OF  THE  TBUNK. 


261 


extended  over  the  loins,  back,  and  side  of  the  thorax,  and  formed  of  an  aponeu- 
rotic and  a  muscular  portion. 

The  aponeurosis  is  attached,  by  its  superior  border,  to  the  summits  of  the 
spinous  processes  of  all  the  lumbar,  and  the  last  fourteen  or  fifteen  dorsal 
xeTtehrss—Jixed  insertion  of  the  muscle. 

The  fibres  of  the  fleshy  portion  are  detached  from  the  inferior  border  of  the 
aponeurosis,  at  the  twelfth  or  thirteenth  ribs,  to  the  cartilage  of  the  scapula. 
They  are  directed  forwards  and  downwards,  and  all  converge  into  a  flat  tendon 
which  is  inserted  into  the  internal  tuberosity  on  the  body  of  the  humerus — 
movable  insertion.    This  tendon  is  remarkable,  at  its  termination,  for  being 

Fig.  162. 


JBUSCLES   OF   THE   SPINAL  REGION  OF   THE   NECK,  BACK,  AND   LOINS  (MIDDLE   LAYER)  ;   AND   OF   THE 
COSTAL   AND    ABDOMINAL    REGION    (SUPERFICIAL    LAYER). 

1,  2,  Rhomboideus ;  3,  annularis  muscle  of  the  scapula  ;  4,  splenius ;  5,  its  mastoid  aponeurosis ; 
6,  mastoid  portion  of  the  trachelo-mastoideus ;  7,  its  tendon ;  8,  cervical  insertions  of  the 
mastoido-humeralis ;  9,  atloidean  tendon  common  to  the  mastoido-humeralis,  splenius,  and 
trachelo-mastoideus;  10,  great  anterior  straight  muscle  of  the  head;  11,  inferior  scalenus; 
12,  superior  scalenus  ;  13,  small   anterior  serratus ;   14,  posterior    ditto  ;  15,   serratus  magnus ; 

16,  anterior  fibres  of  the  rectus  abdominis,  sometimes   described  as   the  traiisversalis  costarum; 

17,  one  of  the  external  intercostals  ;  18,  great  oblique  ;  20,  rectus  abdominis;  21,  stylo-maxillaris 
portion  of  the  digastric  muscle. 

placed  at  the  external  face  of  the  teres  magnus  or  adductor  of  the  arm,  from 
which  it  receives  fibres,  and  between  it  and  the  long  extensor  of  the  forearm ; 
it  then  turns  inwards,  on  the  inferior  extremity  of  the  first,  in  such  a  manner 
that  this  extremity  is  comprised  within  a  duplicature  of  the  membranous  tendon 
of  the  latissimus  dorsi. 

Relations. — This  muscle  is  covered  by  the  skin,  panniculus  carnosus,  dorsal 
portion  of  the  trapezius,  and  the  mass  of  olecranian  muscles.  It  covers  the 
infra-spinatus  ;  the  cartilage  of  the  scapula  ;  the  rhomboideus  ;  the  anterior 
and  posterior  serrated  muscles,  the  aponeurosis  of  which  is  directly  joined  to  its 
own  ;  the  longissimus  dorsi ;  the  principal  gluteal ;  a  portion  of  the  external 
surface  of  the  last  ribs,  to  which  its  aponeurosis  strongly  adheres  ;  as  well  as  to 
the  corresponding  external  intercostals,  and  the  serratus  magnus.  Between 
the  last  rib  and  the  external  angle  of  the  ilium,  the  aponeurosis  unites  with  the 


262  THE  MUSCLES. 

small  oblique,  but  more  particularly  with  the  great  oblique,  muscle  of  the 
abdomen  :  it  is  prolonged,  posteriorly,  on  the  muscles  of  the  croup  to  constitute 
the  gluteal  aponeurosis. 

Action. — It  carries  the  arm  backwards  and  upwards  ;  and  it  may,  according 
to  a  great  number  of  authors,  serve  as  an  auxiliary  in  inspiration  when  its  fixed 
point  is  the  humerus.  According  to  others,  but  in  whose  opinion  we  do  not 
share,  it  is  an  expiratory  muscle. 

Second  Layer. 

3.  Small  Anterior  Serrated  Muscle  (Serratus  Anticus)  (Fig.  162,  13). 

Synonyms.  —  Dorso-costalis  —  Girard.  Anterior  portion  of  the  long  serrated  muscle — 
Bourgelat.  (Superficialis  costarum — Percivall,  Anterior  serrated  muscle  of  Leylj.  Serratus 
posticus  superior  of  Man.) 

Form — Situation. — This  is  a  flat,  thin,  quadrilateral  muscle,  situated  beneath 
the  rhomboideus  and  the  latissimus  dorsi. 

Structure. — It  is  composed  of  an  aponeurotic  and  a  fleshy  portion.  The  first 
is  confounded,  in  front,  with  the  aponeurosis  of  the  splenius,  and  is  insinuated, 
behind,  underneath  that  of  the  posterior  small  serratus,  with  which  it  soon 
becomes  united.  Its  inferior  border  gives  origin  to  the  muscular  portion,  a  little 
above  the  interval  which  separates  the  transversalis  costarum  and  the  longissimus 
dorsi.  Narrow  and  elongated  antero-posteriorly,  the  muscular  portion  is  com- 
posed of  bright-red  fibres  directed  obliquely  backwards  and  downwards,  which 
form  at  the  inferior  border  irregular,  and  sometimes  but  faintly  marked,  festoons. 

Attachments. — It  takes  its  fixed  insertion,  by  the  superior  border  of  its 
aponeurosis,  from  the  summits  of  the  anterior  dorsal  spines,  with  the  exception 
of  the  first,  to  the  thirteenth  inclusive.  The  movable  insertion  takes  place  on 
the  external  surface  and  anterior  border  of  the  nine  ribs  succeeding  the  fourth, 
by  means  of  the  digitations  of  the  fleshy  portion.  This  muscle  is  also  attached 
to  the  external  surface  of  these  ribs  by  a  short  fibrous  band,  which  is  detached 
from  the  internal  face  of  the  aponeurosis,  near  its  inferior  border,  and  penetrates 
the  space  between  the  longissimus  dorsi  and  the  transversalis  costarum. 

Relations. — Outwards,  with  the  rhomboideus,  serratus  magnus,  latissimus  dorsi, 
and  the  posterior  small  serratus,  which  covers  its  three  last  festoons  ;  inwards, 
with  the  longissimus  dorsi,  the  transversalis  costarum,  and  the  external 
intercostals. 

Action. — This  is  an  inspiratory  muscle,  and  it  also  serves  as  a  check  to  the 
deep  spinal  muscles. 

4.  Small  Posterior  Serrated  Muscle  (Serratus  Posticus)  (Fig.  162,  14). 

Synonyms.— Jjumho-coHtalis— Girard.  Posterior  portion  of  the  long  serrated  muscle — 
Bou/gelat.  (Superficialis  costarum — Percivall.  The  posterior  serrated  muscle  of  Leyh.  The 
serratus  posticus  inferior  of  Man.) 

Situation. — Situated  behind  the  preceding,  which  it  follows,  and  presenting 
the  same  form  and  arrangement,  this  muscle  also  offers  the  following  particular 
features  for  study  : — 

1.  Structure. — Its  muscular  portion,  which  is  thicker  and  of  a  deep-red  colour, 
is  cut  into  nine  well-defined  digitations.^  The  fibres  which  compose  it  run  in  an 
almost  vertical  direction. 

'  It  frequently  happens  that  only  eight  diiritations  are  found  in  each  muscle. 


MUSCLES  OF  THE  TRUNK.  263 

2.  Attachmmts. — Its  aponeurosis,  closely  united  to  that  of  the  latissimus 
dorsi,  which  covers  it,  is  attached  to  the  spinous  processes  of  the  dorsal  vertebrse 
succeeding  the  tenth,  and  to  some  lumbar  vertebrae.  Its  digitations  are  fixed  to 
the  posterior  border  and  external  face  of  the  nine  last  ribs. 

3.  Relations. — Outwards,  with  the  latissimus  dorsi ;  inwards,  with  the  small 
anterior  serratus,  the  longissimus  dorsi,  transversalis  costarum,  and  the  external 
intercostals.  Some  of  its  posterior  digitations  are  partly  concealed  by  those  of 
the  great  oblique  muscle  of  the  abdomen  ;  the  last,  indeed,  is  entirely  covered  by 
that  muscle. 

4.  Action. — This  is  an  expiratory  muscle,  in  consequence  of  its  drawing  the 
ribs  backwards  and  upwards. 

Third  Layer. 
5.  The  Ilio-8pinalis  Muscle  (Longissimus  Doesi)  (Fig.  163). 

Synonyms. — It  represents  the  loug  dorsal,  short  transversal,  and  long  spinous  of  Bourgelat. 
Cuvier  and  others  have  described  it  as  consisting  generally,  in  Mammalia,  of  five  particular 
muscles,  designated  as  longissimus  dorsi,  transversalis  cervicis,  semispinalis  dorsi,  and  semi- 
spinalis  colli.     It  corresponds  to  the  longissimus  dorsi,  and  transversalis  cervicis  of  Man. 

(Percivall  designates  this  important  muscle  the  longissimus  dorsi — the  name  given  to  its 
analogue  in  Man,     By  Girard,  Leyh,  and  Oliauveau,  it  is  styled  the  ilio-spinalis.) 

Extent — Situation. — This,  the  most  powerful  and  complex  of  all  the  muscles 
in  the  body,  extends  along  the  dorso-lumbar  spine,  above  the  costal  arches,  from 
the  anterior  border  of  the  ilium  to  the  middle  of  the  cervical  spine. 

Form. — It  is  elongated  from  before  to  behind,  and  flattened  above  and  below 
in  its  posterior  half,  which  represents  the  common  mass  in  Man  ;  this  mass  is 
prismatic  in  form,  thick  inwards,  and  thin  outwards.  Anteriorly,  it  is  flat  on 
both  sides,  and  bifurcates  into  two  vohmiinous  branches,  a  superior  and  inferior, 
between  which  pass  the  insertions  of  the  complexus  to  be  fixed  into  the  transverse 
processes  of  the  first  dorsal  vertebrae. 

Attachments. — 1.  Upon  the  lumbar  border,  the  external  angle  and  internal 
smface  of  the  ilium,  the  sacro-iliac  ligament,  and  the  sacrum.  2.  To  the  spinous 
processes  of  all  the  lumbar  and  dorsal,  and  last  four  cervical  vertebrae.  3.  To 
the  articular  tubercles  of  the  lumbar  vertebrae  and  the  transverse  processes  of  all 
the  dorsal,  and  the  last  fom*  cervical  vertebrae.  4.  To  the  costiform  processes 
of  the  lumbar  vertebrae,  and  the  external  surface  of  the  fifteen  or  sixteen  last  ribs. 

Structure. — If  this  muscle  is  examined  posteriorly,  in  the  part  which  forms 
the  common  mass,  it  wiU  be  found  to  be  composed  of  very  compact  fleshy  fibres, 
covered  in  common  by  a  thick  aponeurosis.  These  fibres  commence  at  the 
posterior  extremity  of  the  muscle,  and  all  proceed  forward,  stopping  to  make 
successive  insertions  on  the  various  bony  eminences  in  its  track,  and  forming 
three  diflferent  orders  of  fasciculi,  which  are  more  or  less  tendinous  at  their 
anterior  or  terminal  extremity.  These  fasciculi  are  internal  and  superficial, 
internal  and  deep,  and  external. 

The  internal  and  superficial,  or  spinal  fasciculi,  pass  to  the  summits  of  the 
spinous  processes  already  noticed  when  speaking  of  the  attachments.  These 
fasciculi  are  little,  if  at  all  distinct  posteriorly  ;  but  they  become  more  so 
anteriorly.  About  the  sixth  dorsal  vertebras,  they  separate  from  the  other 
fascicuU  to  form  the  superior  branch  of  the  muscle  (Fig.  163,  3). 

The  internal  and  deep,  or  transverse  fasciculi,  are  those  which  attach  the 
muscle  to  the  articular  tubercles  of  the  lumbar  vertebrae  and  transverse  processes 


264 


THE  MUSCLES. 


of  the  back  and  neck.    They  are  well  detached  from  each  other,  even  posteriorly, 
and  are  very  tendinous.     Anteriorly,  they  pass  into  the  inferior  branch  of  the 


fongissimus  dorsi,  which  they,  in  common  with  the  external  fasciculi,  go  to  form. 
From  profound,  they  now  become  superficial ;  and  they  are  seen  springing  up  be- 
tween the  others,  which  appear  to  separate  to  allow  them  to  pass  (Fig.  163,  4,  4). 


MUSCLES  OF  THE   TRUNK.  265 

The  external,  or  costal  fasciculi,  turn  a  little  outwards  to  reach  the  ribs  and 
costiform  processes  of  the  lumbar  region ;  they  are  not  very  apparent  in  this 
direction  (%.  163,  2,  2). 

It  win  be  easily  understood  that  all  these  fasciculi  do  not  come  from  the 
common  mass,  which  would  be  expended  long  before  its  termination  at  the  neck, 
in  consequence  of  the  successive  emissions  of  the  fasciculi  composing  it.  To 
prevent  this  exhaustion,  there  are  continually  added  to  it  numerous  bimdles  of 
fibres,  which  arise  either  from  its  aponeurotic  envelope,  or  from  the  bones  on 
which  the  primary  fasciculi  terminate,  and  comport  themselves  absolutely  like 
these,  which  they  are  charged  to  continue  to  the  neck. 

Relations. — It  is  covered  by  the  pyramidal  point  of  the  principal  gluteal 
muscle,  which  it  receives  in  a  particular  excavation,  and  by  the  aponeurosis  of 
the  latissimus  dorsi  and  the  small  serrated  muscles.  It  covers  the  inter- 
transversales  of  the  lumbar  region,  the  semispinalis  of  the  back  and  loins,  the 
levatores  costarum,  and  the  external  intercostals.  Outwards,  it  is  bordered  by 
the  transversalis  costarum. 

The  superior  branch  is  covered  by  the  complexus  and  the  semispinaHs  colli. 
Inwardly,  it  responds  to  the  cervical  ligament  and  the  analogous  branch  of  the 
opposite  muscle. 

The  inferior  branch  responds,  outwardly,  to  the  angularis  of  the  scapula  ;  it 
covers  some  intertransversales  colli,  and  the  aponeurotic  digitations  which  attach 
the  complexus  to  the  transverse  processes  of  the  first  dorsal  vertebrse.  From 
these  digitations  it  even  detaches  a  number  of  muscular  fasciculi,  which  go  to 
strengthen  this  branch  of  the  longissimus  dorsi. 

Action. — It  is  a  powerful  extensor  of  the  vertebral  column,  which,  when  it 
acts  singly,  it  inclines  to  one  side.     It  may  also  take  part  in  expiration. 

6.  Common  Inteecostal  Muscle  (Teansversalis  Costaeum  (Fig.  163,  5). 

Synonyms. — Trachelo-coatalis — Girard.     The  sacro-lumhalis  of  Man. 

Form — Situation. — A  long,  narrow,  and  thin  muscle — particularly  at  its 
extremities — situated  along  the  external  border  of  the  preceding  muscle,  with 
which  it  is  confounded  behind  the  last  rib. 

Structure — Attachments. — This  muscle,  the  structure  of  which  has  been 
complicated  by  so  many  anatomists,  is  yet  extremely  simple.  It  is  formed  of 
a  series  of  fasciculi,  directed  obliquely  forwards,  downwards,  and  outwards, 
tendinous  at  their  extremities,  and  originating  and  terminating  successively  on 
the  external  surface  of  the  ribs.  The  most  posterior  leave  the  external  border 
and  inferior  face  of  the  common  mass.  The  tendinous  digitation  of  the  anterior 
fasciculus  is  inserted  into  the  transverse  process  of  the  last  cervical  vertebra,  in 
common  with  the  inferior  branch  of  the  longissimus  dorsi. 

Relations. — Outwards,  with  the  great  and  small  serratus  ;  inwards,  with  the 
external  intercostals. 

Action. — It  depresses  the  ribs,  and  may  extend  the  dorsal  portion  of  the  spine. 

Fourth  Layer. 

Transverse  Spinous  Muscle  of  the  Back  and  Loins  (Semispinalis 

OF  THE  Back  and  Loins)  (Fig.  161,  3). 

Synonyms. — Transverso-spinous — Girard.  Dorso-lumbar  portion  of  the  semispinalis  of  Maa 
(The  spinalis  and  semispinalis  dorsi — Percivall.) 

Situation — Extent. — This  is  a  very  long  muscle,  directly  applied  to  the  super- 


266  THE  MUSCLES. 

sacral  and  dorso-lumbar  spine,  and  continuous,  in  front,  with  the  semispinalis 
colli  ;  these  two  muscles,  therefore,  measure  nearly  the  whole  length  of  the  spine. 

Structure. — It  is  formed  by  an  assemblage  of  short  fasciculi,  which  are 
flattened  on  both  sides,  tendinous  at  their  extremities,  directed  obliquely  forwards 
and  downwards,  and  a  little  inwards,  thus  crossing  at  a  right  angle  the  spinous 
processes  they  cover. 

Attachments. — These  fasciculi  are  attached,  below,  to  the  lateral  lip  of  the 
sacrum,  the  articular  tubercles  of  the  lumbar  vertebrae,  and  the  transverse 
processes  of  the  dorsal  vertebrae — origin.  They  are  fixed,  above,  to  the  spinous 
processes  of  the  sacral,  lumbar,  and  dorsal  vertebrae,  and  into  that  of  the  last 
cervical  vertebra — termination.  It  is  to  be  remarked  that  they  do  not  attain  the 
summits  of  these  spinous  processes  in  the  first  half  of  the  dorsal  region. 

i^e/a^wws.— Outwards,  with  the  lateral  sacro-coccygeal  and  longissimus  dorsi 
muscles,  which  are  confounded  with  it  near  its  posterior  extremity ;  inwards, 
with  the  sacral  spine  and  the  spines  of  the  lumbar  and  dorsal  vertebrae,  and  with 
the  interspinous  ligaments  of  these  three  regions. 

Action. — It  is  an  extensor  of  the  spine. 

Differential  Characters  in  the  Muscles  of  the  Spinal  Region  of  the  Back  and 
Loins  in  the  other  Animals. 

A.  Ruminants. — In  the  Ox,  Slieep,  and  Goat,  the  trapezius  is  thick  and  very  broad. 

In  the  Sheep,  only  the  posterior  fasciculus  of  the  muscle  annexed  to  the  latissimus  dorsi  is 
seen.  Some  of  its  fibres  are  prolonged  to  the  anterior  border  and  external  face  of  the  latissimus 
dorsi.  In  the  Camel,  the  dorsal  portion  of  the  trapezius  is  remarkable  for  its  size.  The 
latissimus  dorsi  has  a  thicker  and  wider  body  than  that  of  the  Hortse ;  it  descends  low  on  the 
ribs ;  the  aponeurotic  portion  passes  beyond  the  boss  or  hump.  In  the  longissimus  dorsi,  the 
fasciculi  are  very  distinct,  even  in  the  midst  of  the  common  mass,  where  the  external  fasciculi 
can  be  clearly  seen  to  become  attached  separately  to  the  extremities  of  the  transverse  processes 
of  the  lumbar  vertebrae. 

The  anterior  small  serrated  muscle  is  inserted,  by  its  last  digitation,  into  the  ninth  rib. 
The  posterior  serrated  is  fixed  into  the  four  last  ribs. 

B.  Pig.— Its  trapezius  is  well  developed.  The  latissimus  dorsi  is  voluminous,  and  is  attached 
to  the  surface  of  the  ribs,  which  it  covers  by  digitations  from  its  flesliy  portion.  It  is  fixed 
near  the  small  trochanter  to  the  lip  of  the  bicipital  groove.  The  inferior  branch  of  the 
hngissimus  dorsi  of  tbis  animal  is  easily  divided  into  two  portions,  traces  of  which  are  found 
in  the  Horse :  one  is  formed  by  the  costal  fasciculi,  the  other  by  the  transversal  fasciculi.  The 
latter  constitutes  the  muscle  to  which  Bourgelat  has  given  the  name  of  short  transversal. 

C.  Camivora. — Several  of  the  spinal  muscles  in  tbe  Bog  resemble  those  of  the  Pig ;  such 
are  the  trapezium,  the  latissimus  dorsi,  and  the  longissimus  dorsi.  In  animals  of  this  group,  it 
is  remarked  that  the  anterior  serrated  is  very  tiiick  and  very  developed,  and  that  it  is  attached 
to  the  eight  ribs  succeeding  the  second  by  as  many  well-marked  festoons.  The  posterior  has 
only  three  digitations,  which  are  attached  to  tbe  three  last  ribs.  The  transversalis  costarum 
exactly  resembles  the  sacro-lumbalis  of  Man ;  behind  the  last  rib,  it  constitutes  a  thick  fleshy 
body,  separated  by  a  fissure  from  the  longissimus  dorsi,  with  which  it  is  attached  to  the  coxa. 
Lastly,  the  semispinalis  of  the  back  and  loins  is  very  strong  in  the  lumbar  region,  and  is 
prolonged  on  the  coccygeal  vertebrae. 

(According  to  Leyh,  the  semispinalis  muscles  are  absent  in  the  Horse  and  Ruminants; 
they  are  found  in  the  Pig  between  tlie  spinous  processes  of  the  dorsal  and  lumbar  vertebrae, 
and  in  Camivora  between  the  spinous  processes  of  the  cervical  vertebrae.) 

Comparison  of  the  Mdscles  of  the  Back  and  Neck  in  Man  with  the  analogous 
Muscles  in  the  domesticated  Animals  (Fig.  164). 

It  is  usual,  in  human  anatomy,  to  describe  by  the  name  of  muscles  of  the  back  and  neck 
those  which  correspond  to  the  superior  cervical  region,  and  those  of  the  spinal  region  of  the 
back  and  loins  of  the  domesticated  animals.  The  muscles  of  the  inferior  cervical  region  are 
described  in  Man  as  muscles  of  the  neck,  with  the  hyoid  muscles  and  the  scalenus. 


MUSCLES  OF  THE  TRUNK. 


267 


1.  Muscles  of  the  Back  and  Cervix. 
In  the  trapezius  of  Man,  a  cervical  and  a  dorsal  portion  can  no  longer  be  distinguished. 
Abo\ie,  it  is  attached  to  the  superior  occipital  curved  line ;  below,  it  is  fixed  to  the  external 
third  of  the  upper  border  of  the  clavicle,  and  to  the  acromion  and  scapular  spine.  The  fibres 
of  the  trapezius,  which  are  fixed  into  the  clavicle,  represent  a  portion  of  the  mastoido-humeralia 
,  of  quadrupeds. 

The  latissimus  dorsi  resembles  that  of  the  Dog  and  Pig,  its  fleshy  portion  being  very 

Fig.  164. 


FIRST,   SECOND,   AND  PART   OF  THIRD   LAYER  OF   MUSCLES  OF  THE   BACK  OF   MAN;   THE   FIE8T 
LAYER    OCCUPIES   THE   RIGHT,    THE   SECOND   THE   LEFT   SIDE. 

Trapezius  ;  2,  tendinous  portion,  forming,  with  a  corresponding  part  of  the  opposite  muscle,  the 
tendinous  ellipse  on  the  back  of  the  neck  ;  3,  acromion  process  and  spine  of  scapula ;  4,  latissimus 
dorsi  ;  5,  deltoid;  6,  muscles  of  dorsum  of  the  scapula  (infra-spinatus,  teres  minor,  and  teres 
major;  7,  obliquus  externus;  8,  gluteus  medius ;  9,  glutei  maximi ;  10,  levator  anguli  scapulae; 
11,  rhomboideus  minor;  12,  rhomboideus  major;  13,  splenius  capitis,  overlying  the  splenius, 
above;  14,  splenius  colli,  partially  seen  (the  common  origin  of  the  splenius  is  attached  to  the 
spinous  processes  below  the  origin  of  the  rhomboideus  major)  ;  15,  vertebral  aponeurosis  ;  16, 
serratus  posticus  inferior;  17,  supra-spinatus ;  18.  infra-spinatus;  19,  teres  minor;  20,  teres 
major;  21,  long  head  of  triceps,  passing  between  teres  minor  and  major  to  the  arm;  22,  serratus 
magnus,  proceeding  forwards  from  its  origin  at  the  base  of  the  scapula ;  23,  obliquus  internus 
abdominis. 


developed ;  it  is  attached  to  the  external  face  of  the  four  last  ribs  by  muscular  digitations,  and 
terminates  on  the  border  of  the  bicipital  groove. 

The  rhomboideus  is  bifid,  as  in  the  smaller  Quadrupeds.  Less  developed  than  in  these 
animals,  the  levator  anguli  scapulx  is  only  fi.xed  iu  front  to  the  four  first  cervical  vertebrae. 

In  Man,  the  splenius  is  large,  but  by  its  insertions  it  resembles  that  of  Solipeds.  The 
complexus,  thick  and  broad  above,  is  incompletely  divided  into  two  fleshy  bodies,  which  are 


268  THE  MUSCLES. 

attacher],  superiorly,  to  the  sides  of  tlie  external  occipital  crest.  The  trachelo-mastoideus 
is  not  fixed  into  the  axis  and  atlas,  its  superior  extremity  passing  directly  to  the  mastoid 
process. 

There  is  nothing  particular  to  note  regarding  the  straight  posterior  and  oblique  muscles  of 
the  head ;  the  differences  they  offer  in  their  form  are  allied  to  the  conformation  of  the  bones  in 
this  region. 

Of  the  two  small  serrated  muscles,  that  which  corresponds  to  the  anterior  serrated  or 
animals  rises  very  high ;  for  it  is  attached  by  an  aponeurosis  to  the  spinous  processes  of  the 
three  first  dorsal  vertebrae,  the  seventh  cervical,  and  the  cervical  ligament. 

There  are  found  in  Man,  lying  along  the  vertebral  furrows,  several  muscles  which  represent 
the  longissimus  dorsi  and  the  transversalis  costarum  of  Solipeds.  Thus  tlie  common  mass 
covering  the  lumbar  vertebrae  behind,  is  prolonged  by  two  series  of  fleshy  and  tendinous 
fasciculi ;  one  forms  the  sacro-lumhaiis,  which  resembles  the  transversalis  costarum  of  animals ; 
the  other,  the  long  dorsal,  represents  the  inferior  branch  of  the  longissimus  dorsi.  The 
superior  branch  of  the  latter  is  found  in  the  semispinalis  colli. 

Lastly,  there  are  also  seen  in  Man  semispinalis  and  intertransversalis  muscles,  which 
correspond :  the  first,  to  the  semispinalis  of  the  back  and  loins  and  semispinalis  colli ;  the 
second,  to  the  intertransversales  of  the  loins  of  the  domesticated  species. 

2.  Muscles  of  the  Neck. 

The  mastoido-humeraUs  is  not  present  in  Man,  being  peculiar  to  Quadrupeds;  but  we 
should  see  a  portion  of  its  fasciculi  in  the  cleido-mastoideus  muscle,  and  in  the  clavicular 
portions  of  the  trapezius  and  deltoid. 

The  sterno-mastoideus  corresponds  to  the  sterno-maxillaris  of  animals;  as  in  the  Dog,  it 
is  inserted  into  the  external  face  of  the  mastoid  process  and  the  external  two-thirds  of  the 
superior  occipital  curved  line.  Below,  it  commences  by  two  fasciculi — one  from  the  sternum, 
the  other  from  the  clavicle.     We  have  already  alluded  to  this  clavicular  fasciculus. 

The  sterno-lhyro-hyoideus  is  large  and  well  developed,  resembling  in  its  disposition  that  of 
the  smaller  animals.  It  is  to  be  noted  that  the  sterno-hyoideus  portion  leaves  the  sternum,  tlie 
first  costal  cartilage,  and  the  internal  extremity  of  the  clavicle.  The  subscapulo-hyoideus  is 
digastric.  The  anterior  great  straight  muscle  of  the  head  is  attached  to  four  cervical  vertebrae, 
as  in  Ruminants  and  the  Pig.  The  anterior  small  straight,  the  lateral  small  straight,  and  the 
longus  colli,  comport  themselves  as  in  the  smaller  animals.  The  anterior  scalenus  is  very 
developed,  for  it  is  attached  to  the  six  last  cervical  vertebrae. 

Sublumbar,  or  Inferior  Lumbar  Region. 

The  muscles  of  this  region  are  deeply  situated  at  the  inferior  face  of  the 
lumbar  vertebrae  and  the  ilium,  concurring  to  form  the  roof  of  the  abdominal 
cavity,  and  are  in  more  or  less  direct  contact  with  the  viscera  contained  in  that 
cavity.  They  are  nine  pairs.  Three  of  these  have  received  the  generic  name  of 
psoas,  and  are  of  large  volume  ;  they  are  bound  by  a  strong  aponeurosis — the 
iliac  fascia,  and  are  distinguished  as  the  great  psoas,  iliac  psoas  (or  iliacus), 
and  small  psoas.  A  fourth  is  named  the  square  muscle  of  the  loins  {quadratus 
lumhorum).  The  other  five,  placed  between  the  transverse  processes  of  the 
lumbar  vertebrae,  represent,  in  consequence  of  their  connection  with  these  kind 
of  fixed  ribs,  veritable  intercostal  muscles  ;  these  are  the  intertransversales  muscles 
of  the  loins. 

Preparation.— 1.  Place  the  subject  in  the  first  position  :  open  the  abdominal  cavity  by 
completely  removing  its  inferior  walls ;  empty  the  cavity  of  the  viscera  it  contains,  and  excise 
the  diaphragm,  as  that  muscle  prevents  the  anterior  extremity  of  the  great  and  small  psoas 
muscles  being  seen.  2.  First  study  the  iliac  fascia,  its  form,  relations  with  the  long  abductor 
of  the  leg,  its  attachments,  its  continuity  with  the  tendon  of  the  small  psoas,  and  the  expansion 
reflected  from  the  aponeurosis  of  the  ^reat  abdominal  oblique  muscle.  3.  Expose  the  three 
psoas  muscles  by  removing  the  iliac  fascia,  the  two  adductors  of  the  leg,  and  the  three 
adductors  of  the  thigh.  4.  Remove  the  psoas  muscles  for  the  dissection  of  the  quadratus  and 
intertransversales. 


MUSCLES  OF  THE  TRUNK.  269 

1.  Iliac  Fascia,  oe  Lumbo-iliac  Aponeurosis  (Fig.  165,  a). 

This  is  a  very  resisting  fibrous  expansion,  covering  the  great  psoas  and  iliacus 
muscles.  Attached,  inwardly,  to  the  tendon  of  the  small  psoas,  outwardly  to 
the  angle  and  external  border  of  the  ilium,  this  aponeurosis,  as  it  extends  for- 
•wards  over  the  great  psoas,  degenerates  into  connective  tissue.  Behind,  it  also 
becomes  attenuated  in  accompanymg  the  two  muscles  it  covers,  until  near  their 
insertion  into  the  internal  trochanter  of  the  femur.  Its  external  or  inferior  face 
receives,  posteriorly,  the  insertion  of  the  crural  arch,  and  gives  attachment  to 
the  long  adductor  of  the  leg  ;  for  the  remainder  of  its  extent,  it  is  covered  by 
the  peritoneum. 

2.  Great  Psoas  Muscle  (Psoas  Magnus)  (Fig.  165,  1). 

i&j/nonj/ms.— Sublumbo-troclian  t :  n  eus— Gi'rard.   Psoas — Bourgelat.    {Lumho-femoral — Leyh.) 

Form — Situation. — This  is  a  loug  muscle,  flattened  above  and  below  at  its 
anterior  extremity,  prismatic  in  its  middle,  and  terminated  in  a  cone  at  its 
posterior  extremity.  It  lies  beneath  the  transverse  processes  of  the  lumbar 
vertebrae. 

Structure. — Almost  entirely  fleshy,  this  muscle  is  formed  of  very  delicate 
fasciculi,  which  are  directed  backwards,  and  long  in  proportion  to  their  super- 
ficial and  deep  situation.  They  all  converge  to  a  tendon  which  is  enveloped  by 
the  iliacus,  and  is  confounded  with  it. 

Attachments. — It  is  attached  :  1.  By  the  anterior  extremity  of  its  fleshy 
fasciculi  to  the  bodies  of  the  last  two  dorsal  and  the  lumbar  vertebrae,  except  the 
hindermost,  and  to  the  inferior  face  of  the  two  last  ribs  and  the  transverse 
processes  of  the  lumbar  vertebrae.  2.  By  its  posterior  tendon  to  the  internal 
trochanter,  in  common  with  the  iliacus. 

Relations. — Below,  with  the  pleura,  the  superior  border  of  the  diaphragm, 
and  the  lumbo-iliac  aponeurosis,  which  separates  it  from  the  peritoneum  and  the 
abdominal  viscera  situated  in  the  sublumbar  region  ;  above,  with  the  two  last 
internal  intercostals,  the  quadratus  lumborum,  and  the  intertransversales  muscles  ; 
inwardly  with  the  small  psoas  and  the  internal  branch  of  the  iliacus  ;  outwardly, 
for  its  posterior  third,  with  the  principal  branch  of  the  latter  muscle. 

Action. — A  flexor  and  rotator  of  the  thigh  outwards  when  its  fixed  point  is 
the  loins,  this  muscle  also  flexes  the  lumbar  region  when  the  thigh  is  a  fixed 
point.  It  is,  therefore,  one  of  the  agents  which  determine  the  arching  of  the 
loins,  and  which  operate,  during  exaggerated  rearing  or  prancing,  in  bringing 
the  animal  into  a  quadrupedal  position  again. 

3.  Iliac  Psoas  Muscle  (Iliacus)  (Fig.  165,  3). 

Synonyms.— T\\o-irochaxiixnevii&—Girard.  (Leyh  divides  this  muscle  into  two  portions, 
which  he  describes  as  the  great  and  middle  ilio-femoralis. 

Form — Situation — Direction. — This  is  a  very  strong,  thick,  and  prismatic 
muscle,  incompletely  divided  into  two  unequal  portions  by  the  groove  for  the 
reception  of  the  tendon  of  the  great  psoas  :  an  external  portion,  somewhat  con- 
siderable in  size  ;  and  an  internal,  small.  These  two  muscular  portions  lie  at 
the  entrance  to  the  pelvis,  on  the  inner  face  of  the  ilium,  in  an  oblique  direction 
downwards,  backwards,  and  inwards. 

Structure. — It  is  almost  entirely  fleshy.     The  fasciculi  forming  it  are  spread 


270 


THE  MUSCLES. 


out  in  front,  and  collected  behind,  where  they  become  slightly  fibrous,  and  unite 
with  the  tendon  of  the  great  psoas. 

Attachments. — It  has  its  fixed  insertion  on  the  whole  of  the  iliac  surface,  on 
the  external  angle  of  the  ilium,  the  sacro-iUac  hgament,  and  the  ilio-pectineal 

Fig.  165.  I 


MUSCLES   OF   THE  SUBLUMBAR,    PATELLAR,    AND   INTERNAL   CRORAL   REGIONS. 

1,  Psoas  magnus ;  1',  its  terminal  tendon  ;  2,  psoas  parvus ;  3,  iliacus ;  4,  its  small  internal  portion ; 
5.  muscle  of  the  fascia  lata  ;  6,  rectus  femoris  of  the  thigh  ;  7,  vastus  internus  ;  8,  long  adductor 
of  the  leg  ;  9,  short  adductor  of  the  leg;  11,  pectineus ;  12,  great  adductor  of  the  thigh  ;  12', 
small  adductor  of  the  thigh;  13,  semimembranosus;  14,  semitendinosus.  A,  Portion  of  the 
fascia  i/iaca ;  B,  portion  of  the  membrane  reflected  from  the  aponeurosis  of  the  abdominal  great 
oblique  muscle,  forming  the  crural  arch  (Poupart's  ligament)  ;  C,  pubic  tendon  of  the  abdominal 
muscles  ;  D,  origin  of  the  pubio-femoral  ligament. 

crest.  Its  movable  insertion  is  into  the  small  internal  trochanter,  in  common 
with  the  great  psoas. 

Relations. — Above,  with  the  ilium  ;  below,  with  the  iliac  fascia  and  the  long 
adductor  of  the  leg  ;  outwardly,  with  the  muscle  of  the  fascia  lata  and  the  origin 
of  the  rectus  femoris,  from  which  it  is  separated  by  a  space  filled  with  fat ; 
inwardly,  with  the  crural  vessels.  It  passes  between  the  vastus  internus  and  the 
pectineus,  to  reach  the  trochanter. 

Actions. — It  is  a  flexor  and  rotator  outwards  of  the  thigh. 


MUSCLES  OF  THE  TRUNK. 


271 


4.  Small  Psoas  Muscle  (Psoas  Parvus)  (Fig.  165,  2). 


according  to  Girard. 


of    the    loins — 1 
(^Psoaa  parvus — Percivall. 


Sublumbo-pubia 
The  lombo-iliacus 


3,  or    sublumbo-iliacua, 
Leyh.) 


Situation — Form — Structure.  Placed  at  the  inner  side  of  the  psoas  magnus, 
very  much  elongated,  and  semipenniform  in  shape,  this  muscle  is  terminated 
behind  by  a  flattened  tendon,  and  is  composed  of  fleshy  fibres,  the  longest  of 
which  are  anterior.  These  fasciculi  are  all  directed  backwards  and  outwards  to 
gain  the  tendon. 


Attachments.— 1.  To  the  bodies 
of  the  three  or  four  last  dorsal,  and 
to  all  the  lumbar  vertebrse,  by  the 
anterior  extremity  of  its  fleshy  fibres. 
2.  To  the  ilio-pectineal  line  and  the 
lumbo-iliac  aponeurosis,  by  the  pos- 
terior extremity  of  its  tendon. 

Relations. — By  its  inferior  face 
with  the  pleura,  the  superior  border 
of  the  diaphragm,  the  aorta  or  pos- 
terior vena  cava,  and  the  great 
sympathetic  nerve  ;  by  its  upper  face, 
with  the  psoas  magnus.  It  is  tra- 
versed, near  its  vertebral  insertions, 
by  numerous  vascular  and  nervous 
branches. 

Actions. — It  flexes  the  pelvis  on 
the  spine,  when  the  loins  are  the 
fixed  point ;  but  should  the  pelvis  be 
fixed,  it  arches  or  laterally  inclines 
the  lumbar  region.  It  is  also  the 
tensor  muscle  of  the  lumbo-iUac 
aponeurosis. 


Fig.  166. 


DEEP  MUSCLES    OF    THE   SUBLITMBAR   REGION. 

1,  Quadratus  lumborum  ;  2,  2,  intertransversales ; 
3,  small  retractor  muscle  of  the  last  rib — a  de- 
pendent of  the  small  oblique  of  the  abdomen. 


5.  Square  Muscle  of  the  Loins  (Quadratus  Lumborum)  (Fig.  166,  1). 

Synonyms. — Sacro-costalis — Girard.  (Sacro-lumbalis — Percivall.  Quadratus  lumborum  of 
Man.) 

Situation — Form — Structure — Attachments. — This  muscle  is  comprised  between 
the  transverse  processes  of  the  lumbar  region  and  the  psoas  magnus,  is  elongated 
from  before  to  behind,  flattened  above  and  below,  and  divided  into  several  very 
tendinous  fasciculi.  The  principal  fasciculus,  situated  outwardly,  takes  its  origin 
from  the  sacro-iliac  ligament,  near  the  angle  of  the  sacrum,  and  extends  directly 
forward  to  gain  the  posterior  border  of  the  last  rib,  after  being  attached  by  its 
upper  face  to  the  summits  of  the  transverse  processes  of  the  lumbar  vertebrse. 
The  other  fasciculi  are  longer  as  they  are  anterior  ;  they  leave  the  internal  border 
of  the  first,  and  are  directed  obliquely  foi-ward  and  inward,  to  be  fixed  into  the 
transverse  processes  of  the  majority  of  the  lumbar  vertebrae,  and  the  inner  face 
of  the  two  or  three  last  ribs. 

Relations. — By  its  upper  face,  with  the  intertransversales,  the  small  retractor 


E72  THE  MUSCLES. 

of  the  last  rib,  and  the  fibrous  fascia  which  unites  that  muscle  to  the  small 
oblique  of  the  abdomen.     By  its  inferior  face,  to  the  psoas  magnus. 

Actions. — It  draws  the  last  ribs  backwards,  and  inchnes  the  lumbar  spine  to 
one  side. 

6.  Intertransveesales  of  the  Loins  (Fig.  166,  2,  2). 

(^Synonym. — Litertransversales  lumborum — Percivall. ) 

These  are  very  small  flat  muscles  which  fill  the  intervals  between  the  trans- 
verse processes  of  the  lumbar  vertebrae.  Their  muscular  fibres  are  mixed  with 
tendinous  fibres,  and  are  carried  from  the  anterior  border  of  one  transverse 
process  to  the  posterior  border  of  the  other. 

They  respond,  by  their  superior  face,  to  the  longissimus  dorsi,  and  by  their 
inferior  face  to  the  quadratus,  as  well  as  the  psoas  magnus.  They  act  by  inclin- 
ing the  lumbar  region  to  one  side. 

drpfebential  characters  in  the  muscles  of  the  sublttmbar  region  in  the  otheb 

Animals. 

In  Ruminants  and  the  Pig,  the  muscles  of  this  region  so  closely  resemble  those  of 
Solipeds,  that  a  special  description  is  unnecessary.  It  may  be  remarked,  however,  that  the 
quadratus  lumborum  in  the  Sheep  is  very  developed,  and  throws  fibres  as  far  forward  as  tlie 
four  last  ribs. 

In  the  Dog,  the  psoas  magnus  is  little  developed,  and  only  commences  at  the  third,  or  even 
the  fourth  lumbar  vertebra  ;  the  iliacus  is  very  slender,  particularly  in  its  external  portion ; 
otherwise  it  is  scarcely  distinct  from  the  psoas  magnus,  with  which  it  may  be  said  to  form  one 
muscle ;  the  psoas  parvus  is  relatively  larger  than  the  great ;  it  is  not  prolonged  into  tlie 
pectoral  cavity,  and  its  anterior  extremity  is  confounded  with  the  quadratus  lumborum,  which 
is  longer  and  stronger  than  in  all  the  other  animals. 

Comparison  of  the  Subltjmbab  Muscles  of  Man  with  those  of  Animals. 

In  human  anatomy,  by  the  names  of  psoas  and  iliacus  are  described  the  psoas  magnum  and 
iliacus  of  animals.  The  psoas  magnus  of  Man  is  distinguished  from  that  of  Solipeds  by  its 
superior  insertions,  whicii  do  not  go  beyond  the  last  dorsal  vertebrae. 

The  psoas  parvus  is  often  absent :  when  present,  it  is  attached,  above,  to  the  bodies  of  the 
twelve  dorsal  vertebrae ;  below,  to  the  ilio-pectineal  crest. 

The  intertransversales  have  been  studied  with  the  muscles  of  the  back.  The  quadratus 
lumborum,  classed  by  anthropotomi.sts  with  the  abdominal  muscles,  is  distinctly  divided  into 
three  series  of  fasciculi :  ilio-costal  fasciculi,  which  pass  from  the  upper  border  of  the  ilium  to 
the  twelfth  rib;  lumbo-costal  fasciculi,  passing  from  the  transverse  processes  of  the  three  or  four 
last  lumbar  vertebrae  to  the  twelfth  rib ;  and  ilio-lumbar  fasciculi,  going  from  the  iliac  crest  to 
the  posterior  face  of  the  transverse  processes  of  all  the  lumbar  vertebrae. 

Coccygeal  Region. 
This  region  is  composed  of  four  pairs  of  muscles  destined  for  the  movementg 
of  the  tail ;  three,  named  the  sacro-cocajgeal,  are  disposed  longitudinally  around 
the  coccygeal  vertebrae,  which  they  completely  envelop  ;  the  fourth  is  designated 
the  ischio-coccygeus  {compressor  coccygeus). 

1.  Sacro-coccygeal  Muscles  (Fig.  167,  1,  2,  3). 

These  three  muscles  are  enclosed,  with  those  of  the  opposite  side,  in  a  strong, 
common  aponeurotic  sheath,  which  is  continuous  with  the  inferior  ilio-sacral 
and  sacro-sciatic  ligaments.  They  commence  on  the  sacrum,  are  directed  back- 
wards and  parallel  with  the  coccyx,  gradually  diminishing  in  thickness,  and  are 
formed  by  several  successive  fasciculi  terminating  in  small  tendons,  which  are 


MUSCLES  OF  THE  TRUNK. 


273 


inserted  into  each  of  the  coccygeal  bones.  With  regard  to  their  situation,  these 
muscles  are  distinguished  as  sacro-coccygeus  superior,  sacro-coccygeus  inferior,  and 
sacro-coccygeus  lateralis. 

A.  Sacro-coccygeus  Superior  (Erector  Coccygis). — The  fasciculi  which 
form  this  muscle  have  their  fixed  insertion  either  in  the  summits  and  sides  of  the 
three  or  four  last  processes  of  the  supra-sacral  spine,  or  from  the  coccygeal  vertebrse 
themselves.  The  tendons  for  their  movable  insertion  into  these  vertebrae  are 
always  very  short. 

This  muscle,  covered  by  the  coccygeal  aponeurosis,  in  turn  covers  the  vertebrae 
it  moves.  It  responds  :  inwardly,  to  the  analogous  muscle  of  the  opposite  side  ; 
outwardly,  to  the  lateral  sacro-coccygeus,  and,  near  its  anterior  extremity,  to  a 
very  strong  aponeurotic  expansion  which  separates  it  from  the  semispinahs 
muscle.  It  directly  elevates  the  tail,  or  pulls  it  to  one  side,  according  as  it  acts 
in  concert  with  its  fellow  or  singly. 

B.  Sacro-coccygeus  Inferior  (Depressor  Coccygis). — This  muscle  is 
thicker  than  the  precedmg ;  its  constituent  fasciculi  take  their  origin  from  the 

Fi?.  167. 


SACRO-ILIAC   AND   COXO-FEMORAL   ARTICULATIONS,   WITH    THEIR   SURROUNDING   MUSCLES. 

1,  Sacro-coccygeus  superior ;  2,  sacro-coccygeus  lateralis ;  3,  sacro-coccygeus  inferior ;  4,  ischio- 
coccygeus ;  5,  deep  gluteus;  6,  crureus. 

inferior  surface  of  the  sacrum,  towards  the  third  vertebra,  and  from  the  internal 
face  of  the  sacro-sciatic  ligament  and  the  coccygeal  bones.  It  readily  divides  into 
two  parallel  portions,  which  Bourgelat  has  described  as  two  separate  muscles. 
The  fasciculi  of  the  internal  portion  are  inserted,  by  their  posterior  extremity,  into 
the  inferior  face  of  the  first  coccygeal  vertebrae.  Those  of  the  external  portion 
are  furnished  with  strong  superficial  tendons,  nearly  all  of  which  are  for  the 
bones  of  the  tail. 

This  muscle  responds  :  outwardly,  to  the  sciatic  ligament,  the  ischio-coccygeus 
{compressor  coccygeus)  and  coccygeal  aponeurosis  ;  inwardly,  to  the  muscle  of  the 
opposite  side,  and  to  the  coccygeal  attachment  of  the  rectum ;  above,  to  the 
sacrum,  the  bones  of  the  tail,  and  the  lateral  muscle  ;  below,  to  the  rectum  and 
the  coccygeal  aponeurosis. 

It  either  directly  depresses  the  tail  or  inclines  it  to  one  side. 

C.  Sacro-coccygeus  Lateralis  (Curvator  Coccygis). — This  muscle  may 


274  THE  MUSCLES. 

be  considered  as  the  semispinalis  of  the  coccygeal  region  ;  indeed,  it  is  confounded 
with  that  muscle  of  the  back  and  loins  by  its  anterior  extremity,  and  appears  to 
continue  it  to  the  inferior  extremity  of  the  tail. 

The  fasciculi  composing  it  arise  from  the  spinous  processes  of  the  last  lumbar 
vertebrfe,  through  the  medium  of  the  semispinahs,  and  from  the  coccygeal  bones. 
The  tendons  terminating  these  fasciculi  are  deep  and  not  very  distinct. 

It  responds  :  outwardly,  at  the  posterior  extremity  of  the  longissimus  dorsi, 
to  the  inferior  ilio-sacral  ligament  and  the  coccygeal  aponeurosis  ;  inwardly,  to 
the  semispinalis  and  the  coccygeal  vertebrae  ;  above,  to  the  superior  muscle  ; 
below,  to  the  inferior  muscle,  from  which  it  is  nevertheless  separated  by  several 
small  independent  muscular  fasciculi,  which  are  carried  from  one  coccygeal 
vertebra  to  another.     (Leyh  designates  these  the  intertransversales  of  the  tail.) 

It  inchnes  the  tail  to  one  side. 

2.   ISCHIO-COCCYGEUS  (COMPRESSOR   COCCYGIS)  (Fig.  167,  4). 

A  small,  thin,  wide,  and  triangular  muscle,  situated  against  the  lateral  wall  of 
the  pelvis,  at  the  internal  face  of  the  sacro-sciatic  Ugament. 

It  is  attached,  by  an  aponeurosis,  to  that  Ugament  and  to  the  ischiatic  ridge  ; 
it  is  then  directed  upwards  to  be  fixed,  by  its  muscular  fibres,  to  the  side  of  the 
last  sacral  vertebra  and  the  first  two  coccygeal  bones. 

It  is  related,  outwardly,  with  the  sacro-sciatic  Ugament.  and  inwardly  to  the 
lateral  sacro-coccygeus  and  the  rectum. 

It  depresses  the  entire  caudal  appendage. 

Region  of  the  Head. 

The  head  has  a  large  number  of  muscles  disposed  around  the  mouth,  nostrils, 
eyelids,  the  external  ear,  inferior  maxilla,  and  os  hyoides.  They  will  be  divided 
into  five  secondary  regions. 

A.  Facial  Eegion, 

This  region  includes  those  muscles  of  the  head  which  form  a  part  of  the 
framework  of  the  lips,  cheeks,  and  nostrils.  Authors  are  far  from  being 
unanimous  with  regard  to  the  nomenclature  and  description  of  these  muscles. 
"We  recognise  eleven,  which  are  enumerated  below,  chiefly  according  to  the 
nomenclature  of  Girard.  They  are  :  the  labial  {orbicularis  oris)  ;  zygomaticus ; 
supermaxillo-labialis  (nasalis  longus,  or  levator  labii  superioris  proprius) ;  maxillo- 
labialis  {depressor  labii  inferioris) ;  mento-labialis,  suspensor  of  the  chin  (levator 
menti),  which  act  on  the  lips  ;  alveolo-labialis  {buccinator),  which  moves  the 
jaw  ;  super naso-labial is  {levator  labii  superioris  alcequi  nasi),  which  moves  lips 
and  nostrils ;  great  supermaxillo-nasalis  {dilatator  naris  lateralis),  small  super- 
maxillo-nasalis  {dilatator  naris  superior),  naso-transversalis  {dilatator  naris 
transversalis),  which  dilate  the  nostrils  and  false  nostrils  only. 

1.  Labialis,  or  Orbicularis  of  the  Lips  (Orbicularis  Oris)  (Fig.  167,  27). 

Preparation.— Remove  with  scissors  the  skin  covering  the  two  portions  of  this  muscle ; 
afterwards  the  buccal  mucous  membrane  and  subjacent  glands  within  the  lips,  to  expose  its 
internal  face. 

The  orbicularis,  disposed  as  a  sphincter  around  the  anterior  opening  of  the 
mouth,  is  regarded  as  the  intrinsic  muscle  of  the  lips,  and  is  composed  of  two 
portions  or  fasciculi — one  for  the  upper,  the  other  for  the  lower  lip.     United  to 


MUSCLES  OF  THE  TRUNK. 


27$ 


each  other  at  the  commissures  of  the  mouth,  and  confounded  with  the  superficial 
layer  of  the  buccinator,  which  they  appear  to  continue,  these  two  muscular  por- 
tions also  receive  a  large  portion  of  the  fibres  belonging  to  the  majority  of  the 
extrinsic  muscles,  such  as  the  dilatator  naris  lateralis  and  levator  labii  superioris 
alfequi  nasi. 

The  orbicularis  is  not  attached  to  the  neighbouring  bone  ;  its  component 
fibres,  affecting  a  circular  form,  have,  consequently,  neither  beginning  nor  ending, 
except  in  being  continuous  with  other  fibres. 

The  internal  face  of  the  superior  fasciculus  responds  to  a  layer  of  salivary 
glands,  which  in  part  separate  it  from  the  buccal  mucous  membrane.  The  external, 
covered  by  the  skin,  adheres  to  it  in  the  most  intimate  manner,  and  is  found 
isolated  from  it  only  on  the  median  line,  at  first  by  the  aponeurotic  expansion  of 

Fig.  168. 


SUPERFICIAL  MDSCLES    OF   THE    FACE    AND   HEAD. 

1,  Temporo-auricularis  externus,  or  attollens  maximus ;  2,  levator  palpebrae,  or  corrugator  super- 
cilii;  3,  temporo-auricularis  internus,  or  attollens  posticus;  4,  5,  zygomatico-auricularis,  or 
attollens  anticus ;  6,  orbicularis  palpebrarum;  7,  abducens,  or  deprimens  aurem ;  8,  parotid 
gland;  9,  temporal,  or  subzygomatic  vein;  10,  ditto,  artery;  11,  12.  superior  and  inferior 
maxillary  nerves-  13,  fascia  of  the  masseter  muscle;  14,  nasal  bones;  15,  supernasol-abialis,  or 
levator  labii  superioris  alseque  nasi;  16,  supermaxillo-labialis,  or  nasalis  longus  labii  superioris; 
17,  external  maxillary  or  facial  artery;  18,  facial  vein;  19,  supermaxillo-nasalis  magnus,  or 
dilatator  naris  lateralis  ;  20,  superior  maxillary  nerve ;  21,  zygomatico-labialis,  or  zygomaticus ; 
22,  parotid,  or  Steno's  duct ;  23,  masseter ;  24,  alveolo-labialis,  or  buccinator ;  25,  super- 
maxillo-nasalis parvus,  or  nasalis  brevis  labii  superioris  ;  27,  labialis,  or  orbicularis  oris  ;  28, 
maxillo-labialis,  or  depressor  labii  inferioris  ;  29,  mento-labialis,  or  levator  menti. 

the  nasalis  longus,  then  by  a  musculo-fibrous  layer  analogous  to  that  which  forms 
the  levator  menti. 

By  its  internal  face,  the  inferior  fasciculus  likewise  responds  to  the  buccal 
mucous  membrane,  and  to  some  salivary  glands.  By  its  external  face,  it  forms 
an  intimate  union  with  the  cutaneous  integument,  like  the  superior  fasciculus. 

This  muscle  plays  the  part  of  a  constrictor  of  the  anterior  opening  of  the 
mouth,  and  has  complex  functions  to  perform  in  suction,  the  prehension  of  food, 
and  in  mastication. 

2.  Zygomatico-labialis  (Zygomaticus)  (Fig.  168,  21). 

Synonyms. — Portion  of  the  cuticularis  of  Bourgelat.     The  zygomaticus  major  of  Man. 

A  very  small,  pale,  and  thin  ribbon-like  muscle,  arising  from  the  surface  of 
the  masseter,  near  the  maxillary  spine,  by  an  aponeurosis  which  is  confounded 
with  the  panniculus  ;  it  terminates  on  the  surface  of  the  buccinator,  at  a  short 


276  THE  MUSCLES. 

distance  from  the  commissure  of  the  lips.  Covered  by  the  skin,  it  covers  the 
buccinator,  and  some  of  the  superior  molar  glands,  vessels,  and  nerves. 

When  this  muscle  contracts,  it  pulls  back  the  commissure  of  the  lips. 

In  SoJipeds  there  is  also  sometimes  found  a  muscle  resembling  the  zygomaticus 
ininoi'  of  Man.  It  is  a  very  small  fasciculus  situated  under  the  preceding  muscle, 
near  its  superior  extremity.  It  appears  that  this  fasciculus  is  continued,  above, 
by  the  fibres  of  the  lachrymal  muscle,  and  is  lost,  below,  on  the  buccinator  sur- 
face, a  little  beneath  the  carotid  canal. 

3.  SUPERMAXILLO-LABIALIS  (LEVATOR  LaBII  SuPERIORIS  PrOPRIUS,  OR  NaSALIS 

LONGUS)  (Fig.  168,  16). 

Synonyms.  — Levator  labii  superioris  of  Bourgelat.  The  levator  labii  superioris  proprii  of 
Man.     {Nasalis  longus  labii  superioris — Percivall.) 

Situation — Direction— Form — Structure. — Lying  vertically  on  the  side  of  the 
face,  below  the  levator  labii  superioris  alseque  nasi,  this  muscle  is  a  thick  and 
conical  fleshy  mass,  terminated  inferiorly  by  a  tendon. 

Attachments. — It  is  attached,  by  the  upper  extremity  of  its  fleshy  body,  to  the 
external  surface  of  the  supermaxillary  and  zygomatic  bones — origin.  Its  terminal 
tendon  passes  over  the  transverse  muscle  of  the  nose,  to  unite  with  that  of  the 
opposite  side,  and  with  it  to  form  a  single  aponeurotic  expansion,  which  dips  by 
small  fibres  into  the  subcutaneous  musculo-fibrous  tissue  of  the  upper  lip. 

Relations. — Covered  by  the  lachrymal  and  levator  superioris  alfequi  muscles, 
this  muscle  in  turn  covers  the  supermaxiUary  bone,  the  bottom  of  the  false  nostril, 
the  dilatator  naris  inferioris,  and  the  transversalis  nasi. 

Actions. — It  raises  the  upper  lip,  either  directly  or  to  one  side,  as  it  acts  singly 
or  in  concert  with  its  congener  on  the  opposite  side. 

4.  Maxillo-labialis  (Depressor  Labii  Inferioris)  (Fig.  168,  28). 

Synonyms. — Depressor  labii  inferioris — Bigot.  A  dependency  of  the  buccinator  of  Man. 
(Depressor  labii  inferioris — Percivall.  Inferior  maxillo-labialis — Leyh.  Depressor  anguli  oris 
of  Man.) 

Situation — Direction — Form — Structure. — Situated  along  the  inferior  border 
of  the  buccinator,  and  following  its  direction,  this  muscle  forms  a  long  narrow 
fasciculus,  terminating  inferiorly  by  an  expanded  tendon. 

Attachments. — 1.  By  its  superior  extremity,  to  the  anterior  border  of  the 
lower  jaw,  in  common  with  the  deep  plane  of  the  buccinator— ^a;^c?  origin.  2. 
By  its  terminal  tendon,  to  the  skin  of  the  lower  lip — movat)le  insertion. 

Relations. — Outwardly,  with  the  masseter  and  the  facial  portion  of  the  cervical 
panniculus ;  inwardly,  with  the  maxillary  bone ;  in  front,  with  the  buccinator, 
with  which  it  is  directly  united  in  its  upper  two-thirds. 

Actions. — It  separates  the  lower  from  the  upper  lip,  and  pulls  it  to  the  side 
if  one  alone  acts. 

5.  Mento-labialis,  or  Muscle  of  the  Chin  (Levator  Menti)  (Fig.  168,  29). 

[Synonyms. — Percivall  appears  to  describe  this  and  the  next  muscle  as  one,  the  levator  menti. 
It  is  the  quadratus  menti  of  Man.) 

This  name  is  given  to  a  musculo-fibrous  nucleus,  forming  the  base  of  the 
rounded  protuberance  beneath  the  lower  hp  in  front  of  the  beard.  This  single 
nucleus  is  confounded,  in  front,  with  the  orbicularis  of  the  lips,  and  receives  into 
its  upper  face  the  insertion  of  the  two  posterior  middle  muscles  (levatores  menti). 


MUSCLES  OF  THE  TRUNK.  277 

6.  Intermediate  Posterior  Muscle. 

Synonyms.— M-eAins  posterior — Bourgelat.  (Levator  menti — Percivall.  Incisive  muscle  of 
the  lower  lip — Leyh.) 

Bourgelat  describes,  by  this  name,  a  small  muscular  fasciculus,  analogous  in 
every  respect  to  the  medius  anterior.  This  little  muscle  takes  its  origin  from  the 
external  surface  of  the  body  of  the  lower  jaw,  beneath  the  intermediate  and 
corner  incisors  ;  from  thence  it  descends  into  the  texture  of  the  lip,  to  unite  with 
that  of  the  opposite  side  on  the  upper  face  of  the  mento-labialis.  Several  authors 
have  described  it  as  a  dependent  of  the  last  muscle. 

7.  Alveolo-labialis  (Buccinator)  (Fig.  168,  24). 

Synonyms. — Molaris  externus  et  internus — Bourgelat.  {Buccinator — Percivall.  Leyh 
divides  this  muscle  into  two  portions ;  its  superficial  plane  he  designates  the  Buccinator,  and 
the  deep  plane  the  Molaris.) 

Preparation. — Proceed  to  the  ablation  of  the  masseter ;  dissect  the  external  surface  of  the 
muscle,  taking  care  of  the  risorius  Santorini  and  zygomaticus,  which  are  confounded  with  it. 
Then  divide  it  in  the  middle,  as  far  as  the  commissure  of  the  lips ;  turn  down  each  strip  on 
the  jaws,  and  remove  the  mucous  membrane,  in  order  to  study  the  inner  face  of  the  muscle  and 
the  attachments  of  the  superficial  plane  to  the  maxillary  bones. 

Situation — Form. — Situated  on  the  sides  of  the  face,  partly  concealed  by  the 
masseter  muscle,  and  applied  to  the  mucous  membrane  of  the  cheeks,  the  bucci- 
nator is  a  flat,  thin  muscle,  elongated  in  the  direction  of  the  head,  and  formed 
of  two  superposed  planes. 

Extent — Structure — Attachments. — The  deep  plane,  the  longest  and  least  wide, 
is  narrower  at  its  extremities  than  its  middle,  and  is  formed  of  strongly  aponeu- 
rotic muscular  fasciculi,  which  are  attached,  posteriorly  :  1.  To  the  alveolar 
tuberosity.  2.  To  the  external  surface  of  the  superior  maxillary  bone,  above 
the  last  three  molar  teeth.  3.  To  the  anterior  border  of  the  inferior  maxillary 
bone,  behind  the  sixth  molar,  in  common  with  the  depressor  labii  inferioris. 
On  reaching  the  commissure  of  the  lips,  this  muscular  layer  appears  to  be 
continued  by  small  tendon's  with  the  fibres  of  the  orbicularis. 

The  superficial  plane  only  begins  about  the  middle  of  the  deep  one,  the 
anterior  half  of  which  it  entirely  covers.  Its  fibres,  less  tendinous  than  those  of 
the  latter,  extend  from  a  median  raphe  which  also  divides  the  deep  layer  in  its 
length,  and  are  directed,  some  forwards,  some  backwards,  to  terminate  in  the 
following  manner  :  the  first  are  inserted  into  the  external  face  of  the  super- 
maxillary  bone,  above  the  first  molar  tooth  and  the  superior  interdental  space  ; 
the  second  are  attached  to  the  inferior  interdental  space  alone. 

Relations. — Externally,  with  the  masseter,  zygomaticus,  panniculus,  dilator 
naris  lateraUs,  levator  labii  superioris,  the  parotid  duct,  which  crosses  it  to  enter 
the  mouth,  and  the  facial  artery  and  veins  ;  internally,  with  the  buccal  mucous 
membrane.  The  deep  plane  is  accompanied  and  covered  at  its  anterior  border 
by  the  upper  molar  glands  ;  its  posterior  border  is  margined  by  the  inferior  molar 
teeth,  which  it  partially  covers.  The  superficial  layer  is  distinctly  separated  from 
the  deep  one  in  its  anterior  part,  which  is  attached  to  the  supermaxillary  bone. 
Behind,  these  two  planes  adhere  more  intimately  to  one  another,  though  they 
are  found  completely  isolated  by  an  interstice  in  which  one  or  two  large  veins  pass. 

Actions. — The  function  of  the  buccinator  is  particularly  related  to  mastication  : 
this  muscle,  in  fact,  pushes  between  the  molar  teeth  the  portions  of  food  which 
fall  outside  the  alveolar  arches  :  but  it  cannot  aid  in  bringing  the  two  jaws 
together,  as  Lecoq  has  correctly  observed. 


278  THE  MUSCLES. 

8.     SUPERNASO-LABIALIS   (LEVATOR   LaBII   SuPERIORIS   Al^QUI   NaSI) 

(Fig.  168,  15). 

Synonyms. — The  maxillaris  of  Bourgelat.  The  levator  labii  superioris  alxque  nasi  of  Man. 
(Levator  labii  superioris  alxque  nasi — Percivall.     Fronto-lahialis — Leyh.) 

Situation — Direction — Form — Structure. — Situated  on  the  side  of  the  face,  in 
an  obUque  direction  downwards  and  backwards,  this  is  a  wide  muscle,  flattened 
on  both  sides,  elongated  from  below  to  above,  aponeurotic  at  its  superior 
extremity,  and  divided  inf eriorly  into  two  unequal  branches,  between  which  passes 
the  dilatator  naris  lateralis. 

Attachments.— It  has  its  origin,  by  its  superior  aponeurosis,  from  the  frontal 
and  nasal  bones,  and  unites  on  the  median  line  with  the  muscle  of  the  opposite 
side.  Its  anterior  branch,  the  widest  and  thickest,  goes  to  the  external  ala  of  the 
nostril  and  to  the  upper  lip,  where  its  fibres  are  confounded  with  those  of  the 
orbicularis.     The  posterior  branch  terminates  at  the  commissure  of  the  lips. 

Relations. — Outwards,  with  the  skin  ;  inwards,  with  the  levator  labii  superioris, 
the  posterior  portion  of  the  dilatator  naris  superioris,  and  vessels  and  nerves.  Its 
posterior  branch  covers  the  dilatator  naris  lateralis,  and  the  anterior  is  covered 
by  that  muscle. 

Actions. — It  elevates  the  external  ala  of  the  nose,  the  upper  lip,  and  the  com- 
missure of  the  lips. 

9.  Great  Supermaxillo-nasalis  (Dilatator  Naris  Lateralis)  (Fig.  168, 19). 

Synonyms. — The  pyramidalis-nasi  of  Bourgelat.  The  caninus  of  Man.  (Dilatator  naris 
lateralis — Percivall.) 

Situation — Direction — Form — Structure. — This  muscle,  situated  on  the  side 
of  the  face,  between  the  two  branches  of  the  levator  labii  superioris,  in  an  almost 
vertical  direction,  is  triangular  in  form,  and  slightly  tendinous  at  its  summit. 

Attachments. — It  has  its  origin,  by  the  aponeurotic  fibres  of  its  summit,  from 
the  external  face  of  the  supermaxillary  bone,  below  its  ridge.  It  terminates,  by 
its  base,  on  the  skin  covering  the  external  wing  of  the  nostril,  its  most  posterior 
fibres  being  confounded  with  those  of  the  orbicularis  of  the  hps. 

Relations. — Outwardly,  with  the  skin  and  the  inferior  branch  of  the  levator 
labii  superioris  ;  inwardly,  with  the  anterior  branch  of  that  muscle,  and  with 
vessels  and  nerves. 

Actions. — It  dilates  the  external  orifice  of  the  nasal  cavity,  by  pulling  out- 
wards the  external  wing  of  the  nostril. 

10.  Small  Supermaxillo-nasalis  (Dilatator  Naris  Superioris) 
(Fig.  168,  25). 

Synonyms.—The  nasalis  brevis,  and  portion  of  the  subcutaneous  muscle  of  Bourgelat. 
(Nasalis  hrevis  labii  superioris  — Percivall.) 

Girard  has  described,  by  the  above  name,  a  small,  thick,  and  short  muscular 
fasciculus  which  covers  the  external  process  of  the  premaxillary  bone,  the  fibres 
of  which,  either  originating  from  that,  the  supermaxillary  bone,  or  the  internal 
face  of  the  levator  superioris  muscle,  terminate  in  the  skin  of  the  false  nostril, 
and  the  appendix  of  the  inferior  turbinated  bone. 

Rigot  has  attached  to  this  muscle  that  described  by  Bourgelat  as  the  short 
muscle.      The  latter  is  composed  of  short,  transverse  fibres,  applied  to  the 


MUSCLES  OF  THE  TRUNK.  279 

expansion  of  the  cartilaginous  septum  of  the  nose  which  projects  laterally  beyond 
the  nasal  spine.  These  fibres  abut,  by  their  most  eccentric  extremities,  against 
the  skin  of  the  false  nostril  and  the  appendix  of  the  inferior  turbinated  bone. 

To  this  muscle  we  may  attach  the  small  muscular  fasciculus  which  Bourgelat 
has  described  as  the  anterior  intermediate.  To  study  it,  it  is  necessary  to  raise 
the  upper  lip  and  remove  the  mucous  membrane  lining  it.  It  is  then  seen  that 
its  fibres,  attached  to  the  inner  side  of  the  premaxilla,  above  the  incisor  teeth, 
ascend  to  meet  those  of  the  dilatator  naris  superior,  and  to  terminate  with  them 
on  the  anterior  appendix  of  the  inferior  turbinated  bone  ;  some  fibres  become 
lost  in  the  lips. 

The  dilatator  naris  superior  acts  as  an  external  dilator  of  the  nostril  and  false 
nostril.     (Percivall  names  it  the  depressor  labii  superioris.) 

11.  Transversalis  Nasi  (Dilatator  Naris  Transversalis). 

{Synonym. — Dilatator  naris  anterior — Percivall). 

This  muscle  is  in  two  parts  :  one,  inferior,  single,  short,  and  quadrilateral, 
flattened  on  both  sides,  lies  on  the  wide  part  of  the  nasal  cartilages,  forming 
transverse  fibres  ;  the  other,  superior,  pair  muscle,  formed  of  pale  short  fibres 
passing  from  the  thin  portion  of  the  septum  nasi  which  is  laterally  bordered  by 
the  nasal  prolongation,  to  the  skin  of  the  false  nostril  and  appendix  of  the  upper 
turbinated  bone.  Covered  by  the  skin  and  the  aponeurotic  expansion  of  the  two 
elevator  muscles  of  the  upper  lip,  the  transverse  muscle  of  the  nose  covers  the 
cartilages  to  Avhich  it  is  attached,  and  is  confounded  below  with  the  orbicularis 
of  the  lips. 

Designed  to  bring  together  the  two  internal  alte  of  the  nose,  this  muscle 
ought  to  be  considered  more  particularly  as  the  dilator  of  the  nostrils  ;  and,  in 
addition,  as  an  internal  dilator  of  the  false  nostril. 

B.  Palpebral  Region. 

This  region  includes  three  muscles  which  act  upon  the  eyelids  or  the  sldn 
in  proxindty  to  the  orbit ;  these  are  the  Orbicularis  Palpebrarum,  Fronto- 
palpebral  {Corrugator  Supercilii),  Lachrymalis. 

1.  Orbicularis  of  the  Eyelids  (Orbicularis  Palpebrarum)  (Fig.  168,  6). 

This  muscle  is  a  thin  wide  sphincter  common  to  the  two  eyelids,  and  lying 
on  the  palpebral  fibrous  plate  and  the  bones  forming  the  margin  of  the  orbit. 
Its  external  surface  is  covered  by  the  skin,  to  which  it  adheres  very  closely.  A 
small  tendon  wliich  extends  from  the  lachrymal  tubercle  to  the  nasal  angle  of  the 
eye,  is  considered  as  the  origin  of  the  fibres  of  this  muscle  ;  some  of  these — 
the  most  numerous— pass  upwards  and  are  distributed  in  a  circular  manner  in 
the  upper  eyelid  ;  the  others  reach  the  lower  eyelid  and  rejoin  the  numerous  ones 
towards  the  temporal  angle  of  the  eye. 

The  contraction  of  this  muscle  determines  the  occlusion  of  the  palpebral  opening. 

2.  Fronto-Palpebral,  or  Corrugator  Supercilii  (Fig.  168,  2). 

This  is  a  short  flat  muscle,  arising  from  the  external  surface  of  the  frontal 
bone,  and  passing  downwards  and  outwards  to  mix  its  fibres  with  those  of  the 
orbicularis  at  the  supra-orbital  foramen,  which  it  covers,  and  the  skin  of  the  eye- 
brow.   It  has  been  erroneously  considered  as  an  elevator  of  the  upper  eyelid.   When 


280 


THE  MUSCLES. 


it  contracts,  it  is  limited  to  wrinkling  the  skin  of  the  eyebrow  in  drawing  it  slightly 
to  the  nasal  angle — which  it  can  do  whether  the  eyelids  are  in  contact  or  apart. 


3.  Lacheymalis  Muscle. 

((Synonym.— Not  mentioned  by  Percivall.     It  is  the  inferior  palpebral  muscle  of  Leyh.) 

A  wide  and  very  thin  muscle,  situated  superficially  below  the  eye.  It  is  con- 
tinuous, in  front,  with  the  panniculus  ;  behind,  with  the  levator  labii  superioris  ; 
above,  with  the  orbicularis  of  the  eyelids.  Its  fibres,  partly  muscular  and  partly 
aponeurotic,  leave  the  external  surface  of  the  lachrymal  and  malar  bones,  are 

directed  do«Ti  wards,  and  become 
Fig- 169.  lost  in  a  connective  tissue  fascia 

which  covere  the  buccinator ; 
some  pass  beneath  the  zygo- 
maticus  and  form  the  zygoma- 
ticus  minor, when  this  is  present. 
This  muscle  is  supposed  to 
corrugate  and  twitch  the  skin 
below  the  eye. 

c.  aueicular,  or  conchal 
Region. 

The  muscles  of  this  region 
move  the  concha,  or  pavilion 
of  the  ear  {concha  auris).  The 
largest  arise  from  the  surface 
of  the  cranial  bones  or  cord  of 
the  cervical  ligament,  and 
terminate  on  the  cartilages  of 
the  external  ear  ;  the  medium- 
sized  pass  from  one  cartilage  to 
another ;  and  the  smallest  are 
found  on  the  surface  of  the 
concha,  inside  and  out.  The 
latter  are  really  intrinsic 
muscles,  but  they  are  of  so  little 
importance  that  we  will  not 
describe  them.  The  others  are 
ten  in  number. 

In  the  first  plane  we  find 
the  zijgomatico-auricularis  {atto- 
Ims  anticus),  temper o-auricu- 
laris  externus  (attolens  maxi- 
mus),  scuto-auricularis  externus, 
three  cervico-auriculares  (re- 
trahens  externum,  medius,  inter- 
nus),  and  parotido-auricularis 
(abducens)  ;  the  second  plane,  the  temporo-auricularis  internus  {attolens  posticus), 
scuto-auricularis  internus,  tympano-auricularis  {mastoido-auricularis). 

Before  studying  these  muscles,  it  is  indispensable  to  examine  the  pieces  of 


MUSCLES  OF  THE  EXTERNAL  EAR  OF  THE  MULE. 
1,  1,  AttoUens  maximus;  2,  attoUens  posticus;  3,.  scuti- 
form  cartilage  ;  4,  scuto-auricularis  externus.  A,  auri- 
cular branches  of  the  first  cervical  nerve ;  B,  anterior 
auricular  nerve  (from  the  facial)  ;  C,  terminal  branches 
of  the  superciliary  nerve ;  D,  superficial  or  temporal 
branch  of  the  lachrymal  nerve. 


MUSCLES  OF  THE  TRUNK.  281 

cartilage  which  form  the  concha.      These  are   three   in   number  :    1.  Conchal 
cartilage.     2.  Annular  cartilage.     3.  Scutiform  cartilage. 

1.  Conceal  Cartilage. — The  principal  portion  of  the  pavilion,  this  cartilage 
determines  its  general  configuration.  In  shape  it  resembles  a  trumpet  with  a 
wide  opening  on  one  side.  Its  entrance  is  elliptical,  and  elongated  vertically, 
being  circumscribed  by  two  thin  borders  which  unite  above  at  a  point  that 
constitutes  the  summit  (apex)  of  the  organ.  Its  base,  bulging  in  a  cul-de-sac, 
terminates  in  front  by  a  constricted  infundibulum  ;  it  is  attached  to  the  margin 
of  the  auditory  hiatus  by  means  of  the  annular  cartilage,  to  the  surface  of 
the  guttural  pouch  by  a  pointed  prolongation  that  descends  outside  this  annular 
cartilage,  beneath  the  parotid  gland,  and  terminates  by  several  fibrous  filaments. 
This  portion  of  the  framework  of  the  concha  is  a  cartilaginous  plate,  rolled  on 
itself  in  such  a  manner  as  to  circumscribe,  between  its  borders,  the  entrance  to 
the  ear,  and  to  form,  inferiorly,  the  complete  infundibuliform  canal  just  men- 
tioned. (Externally,  the  integument  of  the  ear  is  covered  by  ordinary  hair,  but 
internally  there  are  long  fine  hairs,  especially  near  the  entrance ;  these  prevent 
the  intrusion  of  foreign  substances.) 

In  Ruminants,  this  cartilage  is  thin,  inclined  outwards,  and  largely  open.  In  the  Fig, 
it  differs  slightly  according  to  breed,  but  it  is  always  much  developed,  sometimes  erect,  and 
more  frequently  drooping  forward.  It  is  always  short,  pointed,  erect,  and  open  towards  the  front 
in  the  Cat.    In  the  Dog,  it  is  sometimes  short  and  straight ;  in  others  broad  and  pendant. 

2.  AjraruLAR  Cartilage. — By  this  name  is  known  a  little  ring-shaped  plate, 
placed  at  the  lower  part  of  the  conchal  cartilage,  intermediate  between  it  and  the 
auditory  canal.  The  internal  integumentary  membrane,  with  some  yellow  elastic 
fasciculi,  unites  this  cartilage  to  the  other  two  portions  between  which  it  is  situ- 
ated. Its  relations  with  these  are  such,  that  it  receives  within  its  lower  border 
the  bony  circular  prominence  forming  the  margin  of  the  auditory  hiatus,  while  it 
may  itself  be  received  into  the  infundibuliform  canal  of  the  conchal  cartilage — 
an  arrangement  resembling  the  tubes  of  a  telescope. 

3.  Scutiform  Cartilage. — This  is  a  small  cartilaginous  plate,  situated  in 
front  of  the  base  of  the  concha,  at  the  surface  of  the  temporal  muscle  ;  it  is 
irregularly  triangular,  is  attached  to  the  conchal  cartilage  by  some  muscular 
fasciculi,  and  transmits  to  that  cartilage  the  action  of  some  other  muscles  which 
are  fixed  on  the  cranial  bones. 

(The  arteries  of  the  concha  proceed  from  branches  of  the  external  carotid, 
and  the  veins  pass  to  a  trunk  of  the  same  name  ;  the  nerves  are  divisions  of  the 
facial  and  the  first  cervical  pair.) 

An  adipose  cushion,  placed  at  the  base  of  the  ear,  facilitates  the  movements  of 
the  cartilages  when  they  are  acted  upon  by  these  muscles. 

1.  Zygomaticus-auricularis  (Attollens  Anticus)  (Figs.  168,  4,  5  ;  170, 19). 

This  muscle  is  generally  composed  of  two  fleshy  bands  joined  by  connective 
tissue,  and  rising  from  the  zygomatic  process  of  the  temporal  bone  by  means  of  an 
aponeurosis  common  to  it  and  the  orbicularis  palpebrae.  The  inferior  of  these 
two  bands  is  inserted  into  the  outside  of  the  base  of  the  concha,  its  fibres  mixing 
with  those  of  the  abducens ;  the  superior  band  terminates  on  the  outer  border 
of  the  scutiform  cartilage. 

Placed  immediately  beneath  the  skin,  this  muscle  partly  covers  the  superior 
extremity  of  the  parotid  gland,  and  the  zygomatic  process. 

It  draws  the  ear  forward. 


282  TEE  MUSCLES. 

2.  Temporo-auricularis  Externus  (Attolens  Maximus)   (Figs.   168,  1 ; 
169,  1,  1  ;  170,  3,  4). 

A  very  thin,  wide  muscle,  covered  by  the  skin,  lying  on  the  temporal  muscle, 
united  posteriorly  to  the  retrahens  externus,  in  front  and  outwardly  to  the 
attollens  maximus.  It  arises  from  the  whole  of  the  parietal  crest  or  ridge,^ 
mixing  in  its  upper  half  or  third  with  the  muscle  of  the  opposite  side  ;  it  termi- 
nates, by  one  portion,  on  the  inner  margin  of  the  scutiform  cartilage,  and  by 
another,  on  the  inner  side  of  the  conchal  cartilage,  by  means  of  a  thin  fascia  that 
covers  part  of  the  former  cartilage  and  the  external  scuto-auricularis. 

It  acts  as  an  adductor  of  the  concha,  drawing  it  inwards ;  it  also  carries  it 

Fig.  170. 


MUSCLES  OF   THE    EAR. 

1,  Retrahens  externus;  2,  attollens  posticus;  3,  4,  attollens  maximus;  5,  scutiform  cartilage; 
6,  scuto-auricularis  externus;  7,  posterior  auricular  artery;  8,  portion  of  the  zygomaticus-auii- 
cularis;  9,  orbital  process;  10,  temporo-auricularis  internus ;  11,  temporal  muscle;  12,  scutiform 
cartila£;e  ;  13,  ditto  ;  14,  concha  of  the  ear  ;  15,  scuto-auricularis  externus  ;  16,  internal  scuto- 
auricularis;   17,  abducens;  18,  corrugator  supercilii ;    19,  zygomaticus-auricularis. 


forwards,  and  concurs  in  making  it  pivot  on  itself, 
the  ear  forward. 


as  to  bring  the  opening  of 


3.  Scuto-Auricularis  Externus  (Figs.  169,  4  ;  170,  6). 

This  muscle  may  be  said  to  be  a  dependency  of  the  preceding,  the  action  of 
which  it  transmits  to  the  conchal  cartilage,  and  renders  it  more  complete. 

Extending  from  the  external  face  of  the  scutiform  cartilage  to  the  inner  side 

'  Owing  to  this  crest  bordering  the  temporal  fossa,  Girard  has  thought  proper  to  give  to 
the  two  muscles  of  the  ear  attached  thereto,  the  name  of  temporo-auriculares ;  but  it  would  be 
more  appropriate  to  designate  them  the  parieto  auricularea. 


MUSCLES  OF  THE  TRUNK.  283 

of  the  concha,  and  generally  composed  of  two  fasciculi,  it  is  covered  by  the  skin 
and  the  conchal  band  of  the  attollens  maximus,  while  it  covers  part  of  the  internal 
scuto-auricularis  muscle. 

When  this  muscle  contracts,  it  principally  participates  in  producing  the 
rotatory  movement  that  carries  the  opening  of  the  concha  outwards. 

4.  Cekvico-auriculares  (Retrahentes  Aurem)  Muscles  (Fig.  168). 

Three  in  number,  and  situated  behind  the  ear,  these  muscles  are  broad,  thin 
bands,  extending  from  the  cervical  ligament  to  the  conchal  cartilage.  With 
regard  to  their  position  at  their  origin,  they  may  be  distinguished  as  external^ 
middle,  and  internal ;  the  situation  of  their  point  of  insertion  in  the  concha  also 
permits  their  being  classed  as  superior,  middle,  and  inferior. 

The  retrahens  externus,  or  superior  or  superficial  cervico-auricularis,  closely 
united  to  the  attollens  maximus,  and  covered  by  the  skin,  covers  the  medius  and 
internus  muscles.  Attached  by  iis  terminal  extremity  to  the  middle  of  the 
posterior  face  of  the  concha,  it  draws  that  cartilage  backwards  and  downwards. 

The  retrahens  medius,  or  middle  cervico-auricularis,  comprised  at  its  origin 
between  the  other  two,  and  intimately  attached  to  them,  especially  the  deep  one, 
is  in  relation  with  the  skin  for  the  greater  part  of  its  superficies.  Its  terminal 
extremity  is  very  wide  and  thin,  and  passes  over  the  upper  end  of  the  parotid 
gland,  to  be  inserted  outwardly  into  the  base  of  the  concha,  after  being  slightly 
insinuated  beneath  the  abducens.  This  is  a  rotator  muscle,  turning  the  opening 
of  the  ear  outwards  and  backwards. 

The  retrahens  internus,  or  inferior  or  deep  cervico-auricularis,  concealed  beneath 
the  upper  extremity  of  the  parotid,  to  which  it  adheres  closely,  is  inserted  at  the 
base  of  the  concha.     Its  action  is  similar  to  that  of  the  middle  muscle. 

5.  Parotido-auricularis  (Abducens,  or  Deprimens  Aurem) 
(Figs.  168,  7  ;  170,  17). 

Lying  on  the  external  face  of  the  parotid  gland,  this  is  a  long,  thin,  ribbon- 
like  band,  narrower  and  thicker  at  its  upper  than  its  lower  extremity.  It  arises 
on  the  tissue  of  the  gland,  and  terminates  outside  the  base  of  the  concha,  below 
the  inferior  commissure  formed  by  the  two  borders  of  that  cartilage. 

Covered  externally  by  a  very  thin  portion  of  the  cervico-facial  panniculus, 
the  abducens  is  an  abductor  of  the  ear,  inclining  it  outwards. 

6.  Temporo-auricularis  Internus  (Attollens  Posticus)  (Fig.  170,  2). 

Situated  beneath  the  superficial  muscle  of  this  name,  and  partly  covered  by 
the  retrahens  externus,  this  muscle  is  long  and  triangular  in  shape,  bright-red  in 
colour,  and  extending  transversely  on  the  surface  of  the  temporalis  ;  it  is  attached, 
inwardly,  to  the  sagittal  or  spur-like  ridge  of  the  parietal  bones,  and  outwardly, 
by  means  of  a  small  tendon,  to  the  inner  side  of  the  concha,  within  the  terminal 
insertion  of  the  retrahens  externus  auricularis.     It  is  an  adductor  of  the  ear. 

7.  Scuto-auricularis  Internus  (Fig.  170,  16). 

This  is  a  muscle  composed  of  two  short,  pale  fasciculi,  which  cross  each  other 
very  obliquely,  are  concealed  beneath  the  scutiform  cartilage  and  the  scuto- 
auricularis  externus,  and  lie  directly  on  the  adipose  cushion  of  the  ear.     They 


284  TEE  MUSCLES. 

arise  from  the  inner  face  of  the  scutiform  plate,  pass  backwards,  and  termi- 
nate at  the  base  of  the  concha,  behind  the  infundibuhform  cavity  which  that 
cartilage  forms  at  its  root.  This  muscle  is  antagonistic  to  the  external  muscle 
of  this  name,  as  it  turns  the  opening  of  the  ear  outwards,  and  even  backwards. 

8.  Mastoido-auricularis. 

This  name  is  given  to  a  very  thin  fasciculus  lying  vertically  on  the  inner 
side  of  the  cartilage,  at  the  entrance  to  the  ear.  Arising  from  the  margin  of 
the  auditory  external  hiatus,  and  attached  to  the  base  of  the  concha,  this  little 
muscle,  in  contracting,  constricts  the  cartilaginous  tube  with  which  it  is  in  contact. 

D.  Masseteric,  or  Temporo-maxillary  Region. 

This  region  comprises  five  pair-muscles  for  the  movement  of  the  lower  jaw. 
These  are  :  the  masseter,  temporalis,  pterygoidms  internus,  pterygoideus  externuSy 
and  digastricus. 

Preparation.— \.  First  study  the  digastricus  and  its  stylo-maxillary  portion,  with  the 
internal  pterygoid,  in  preparing  the  hyoid  muscles  as  they  are  represented  in  Fig.  171.  2. 
Expose  the  pterygoideus  extemus,  by  removing  in  this  preparation  the  hyoid  bone  and  its 
dependencies,  as  well  as  the  two  preceding  muscles.  3.  To  dissect  the  temporalis,  excise  the 
external  pterygoideus  from  its  inferior  border,  an  operation  which  exposes  the  orbital  fasciculus 
of  the  temporalis ;  then  turn  over  the  piece,  saw  oflF  the  orbital  process  at  each  end,  and  remove 
the  eye  and  auricular  muscles.  4.  Dissect  the  masseter,  in  clearing  away  from  its  external 
surface  the  cuticularis  and  the  vessels  and  nerves  which  cover  it. 

1.  Masseter  (Fig.  168,  23). 

Synonyms. — Zygomatico-maxillaris — Girard. 

Situation — Form — Structure. — Applied  against  the  external  face  of  the  branch 
of  the  lower  jaw,  the  masseter  is  a  short,  wide,  and  very  thick  muscle,  flattened 
on  both  sides,  irregularly  quadrilateral,  and  formed  of  several  superposed  planes, 
two  of  which  are  perfectly  distinct  towards  the  temporo-maxillary  articulation, 
by  the  somewhat  different  direction  of  their  fibres.  These  are  divided  by  a 
considerable  number  of  intersections,  and  are  covered  by  a  strong  aponeurotic 
layer,  which  becomes  gradually  thinner  backwards  and  downwards. 

Attachments. — The  fasciculi  of  the  masseter  have  their  fixed  insertion  on  the 
zygomatic  crest.  Their  movable  insertion  is  on  the  imprints  which  cover  the 
upper  half  of  the  ramus  of  the  inferior  maxilla. 

Relations. — It  responds,  by  its  superficial  face,  to  the  facial  portion  of  the 
cervical  panniculus,  to  the  nerves  of  the  zygomatic  plexus,  and  several  venous  and 
arterial  vessels  ;  by  its  deep  face,  to  the  inferior  maxillary  bone,  the  buccinator 
and  depressor  labii  inferioris  muscles,  the  superior  molar  glands,  and  two  large 
venous  branches ;  by  its  inferior  border,  with  the  parotid  duct,  and  the  glosso- 
facial  artery  and  vein  ;  by  its  superior  and  posterior  border,  to  the  parotic  gland. 
Its  deep  plane  responds,  anteriorly,  with  the  temporo-maxillary  articulation,  and 
is  so  intimately  confounded  with  the  temporalis,  that  it  is  impossible  to  define 
the  respective  limits  of  the  two  muscles. 

Action. — This  muscle,  the  special  elevator  of  the  lower  jaw,  plays  an  important 
part  in  mastication.  It  always  acts  as  a  lever  of  the  third  class — the  middle 
Une,  which  represents  the  resultant  of  all  its  constituent  fibres,  passing  behind 
the  last  molar. 


MUSCLES  OF  THE  TRUNK.  285 

2.  Temporalis. 

Synonyms. — Temporo-maxillaria — Girard. 

Situation — Form — Structure. — Situated  in  the  temporal  fossa,  to  which  it  is 
moulded,  and  which  it  fills,  this  muscle  is  flattened  from  above  to  below,  divided 
by  strong  tendinous  intersections,  and  covered  by  a  nacrous  aponeurotic  layer. 

Attachments. — It  takes  its  origin  :  1.  In  the  temporal  fossa  and  on  the  bony 
crests  which  margin  it.  2.  By  a  wide  fasciculus,  paler  than  the  other  portion  of 
the  muscle,  but  not  unconnected  with  it,  from  the  imprints  situated  behind  the 
crest  surmounting  the  orbital  hiatus.  It  terminates  on  the  coronoid  process  and 
the  anterior  border  of  the  branch  of  the  lower  jaw. 

Relations. — This  muscle  covers  the  temporal  fossa,  and  is  covered  by  the 
attoUens  muscles,  scutiform  cartilage,  internal  scuto-auricularis,  the  fatty  cushion 
at  the  base  of  the  ear,  and  by  another  adipose  mass  which  separates  it  from  the 
ocular  sheath.  Its  deep  fasciculus  responds,  by  its  internal  face,  to  the  two 
pterygoid  muscles. 

Action. — It  brings  the  lower  jaw  in  contact  with  the  upper,  by  acting  as  a 
lever  of  the  first  kind  ;  but  the  orbital  portion  of  the  muscle  elevates  the  inferior 
maxilla  and  moves  it  laterally  by  a  lever  of  the  third  kindo 

3.  Pterygoideus  Internus. 
Synonyms. — Portion  of  the  spheno-maxillaris  of  Bourgelat. 

Sitimtion — Form — Structure.— Sit\ia.ted  in  the  intermaxillary  space,  opposite 
the  masseter,  the  pterygoideus  internus,  although  not  so  strong  as  that  muscle, 
yet  so  closely  resembles  it  in  form  and  structure  as  to  be  named  by  "Winslow  the 
internal  masseter. 

Attachments. — 1.  To  the  palatine  crest  and  subsphenoidal  process— ;/?a;e^ 
insertion.  2.  In  the  hollow  excavated  on  the  inner  face  of  the  branch  of  the 
lower  jaw — movable  insertion. 

Relations. — Outwardly,  with  the  pterygoideus-externus,  the  orbital  fasciculus 
of  the  temporal,  the  maxillo-dental  nerves,  mylo-hyoideal,  and  lingual  muscles, 
arteries  and  veins,  and  the  inner  surface  of  the  bone  which  receives  its  movable 
insertion.  Inwardly,  with  the  tensors  palati— external  and  internal,  the 
guttural  pouch,  the  hyoideus  magnus,  hyoid  bone,  digastricus,  the  hypoglossal 
and  glosso-pharyngeal  nerves,  glosso-facial  artery  and  vein,  the  hyoglossus  longus 
and  brevis  muscles,  the  laryngo-pharyngeal  apparatus,  the  Stenonian  duct,  and 
the  submaxillary  glands. 

Action. — It  is  an  elevator  of  the  lower  jaw,  and  also  gives  it  a  very  marked 
lateral  or  diductive  motion.  If  the  left  muscle  acts,  this  movement  carries  the 
inferior  extremity  of  the  lower  jaw  to  the  right ;  if  it  be  the  right  muscle,  then 
in  the  contrary  direction. 

4.  Pterygoideus  Externus. 

(Synoraj/w.— Portion  of  the  spheno-maxillaris  of  Bourgelat. 

Form — Situation — Strmture — Attachments. — A  small,  short,  and  very  thick 
muscle,  situated  within  and  in  front  of  the  temporo-maxillary  articulation, 
formed  of  shghtly  tendinous  fasciculi  which  leave  the  inferior  face  of  the 
21 


286  THE  MUSCLES. 

sphenoid  bone  and  the  suhsphenoidal  process,  and  are  directed  backwards  and 
upwards  to  be  fixed  to  the  neck  of  the  inferior  maxillary  condyle. 

Relations. — Outwardly,  with  the  orbital  fasciculus  of  the  temporalis  muscle 
and  the  temporo-maxillary  articulation.  Inwardly,  with  the  numerous  nerves 
emanating  from  the  inferior  maxillary  branch,  and  with  the  internal  pterygoid 
and  tensors  palati. 

Action. — When  the  two  external  pterygoids  act  in  concert,  the  inferior 
maxilla  is  pulled  forward  ;  but  if  only  one  contract,  the  propulsion  is  accompanied 
by  a  lateral  movement,  during  which  the  extremity  of  the  jaw  is  carried  to  the 
opposite  side. 

5.   DiGASTRICUS   (StYLO-MAXILLARIS). 

Synonyms. — Bourgelat  has  made  two  distinct  muscles  of  this — the  digastricus  and  stylo- 
maxillaris.  Girard  lias  described  it  as  the  stylo-maxillaris.  (Percivall  has  evidently  followed 
Bourgelat's  example,  and  divided  the  muscle  into  digastricus  and  stylo-maxillaris.  Leyh 
adopts  the  same  course.) 

Form — Structure — Situation — Direction. — Composed  of  two  fleshy  bodies 
more  or  less  divided  by  intersections,  and  united  at  their  extremities  by  a  median 
tendon,  this  muscle  is  situated  in  the  intermaxillary  space,  and  extends  from  the 
occiput  to  near  the  symphysis  of  the  chin,  describing  a  curve  upwards. 

Attachments. — It  takes  its  origin  from  the  styloid  process  of  the  occipital 
bone,  by  its  superior  fleshy  body.  It  terminates  :  1.  On  the  curved  portion  of 
the  posterior  border  of  the  lower  jaw  by  a  considerable  fasciculus,  which  is 
detached  from  the  superior  fleshy  body.^  2.  On  the  internal  face  of  the  same 
bone  and  the  straight  portion  of  its  posterior  border,  by  aponeurotic  digitations 
which  succeed  the  muscular  fibres  of  the  inferior  fleshy  body. 

Relations.— The  superior  belly  of  the  muscle  responds,  superficially,  to  the 
parotid  gland  and  the  tendon  of  insertion  of  the  sterno-maxillaris  ;  deeply,  to 
the  guttural  pouch,  the  submaxillary  gland,  and  the  larynx  and  pharynx.  The 
median  tendon  passes  through  the  ring  of  the  hyoideus  magnus.  The  lower 
belly  is  in  contact,  outwards,  with  the  ramus  of  the  inferior  maxilla  ;  inwards, 
with  the  mylo-hyoideus  muscle. 

Action. — When  this  muscle  contracts,  it  acts  at  the  same  time  on  the  hyoid 
bone,  which  it  raises  in  becoming  straight,  and  on  the  lower  jaw,  which  it  pulk 
backwards  and  depresses  at  the  same  time. 

E.  Hyoideal  Region. 

This  region  includes  six  muscles  grouped  around  the  os  hyoides,  which  they 
move.  Five  of  these  are  pairs  :  the  mylo-hyoideus,  genio-hyoideus,  stylo-hyoideus, 
kerato-hyoideus  {hyoideus  parvus),  and  the  occipito-styloideus.  The  single  one  is 
the  hyoideus  transversus. 

Prepara(/on.— Separate  the  head  from  the  trunk,  and  remove  the  muscles  of  the  cheeks  on 
one  side,  with  the  parutid  gland.  2.  The  branch  of  the  inferior  maxilla  being  thus  exposed,  it 
is  sawn  through  in  two  places;  at  first  beliind  the  last  molar,  then  in  front  of  the  first.  3. 
After  having  separated  the  pterygoids  and  the  stylo-maxillaris  from  the  upper  fragment  or 
condyle,  and  the  coronoid  process,  it  is  torn  off  by  pulling  it  backwards ;  then  the  pterygoids 
and  digastricus  are  excised.    4.  The  inferior  fragment  of  the  jaw  bearing  the  molar  teeth  is 


1  This  is  the  fasciculus  which  Bourgelat  has  described  as  a  distinct  muscle,  and  named  the 
ttylo-maxillaris. 


MUSCLES  OF  THE  TRUNK.  287 

turned  down  by  isolating  the  mylo-hyoideus  from  the  mucous  membrane.  5.  Carefully  remove 
the  tongue  by  separating  its  extrinsic  muscles  from  the  genio-hyoideus,  the  anterior  appendix 
of  the  hyoid  bone,  the  transverse  muscle,  and  the  small  hyoideus. 

The  dissection  having  been  performed  in  this  manner,  the  large  hyoideal  branch  may  Ijp 
separated  from  the  small,  by  sawing  through  the  head  longitudinally,  leaving  the  symphysis 
menti  intact,  and  turning  down  the  corresponding  half  to  the  side  already  dissected,  as  well  as 
the  great  hyoid  branch,  the  pharynx,  larynx,  and  soft  palate. 

1.  Mylo-hyoideus. 

jPorm — Situation — Structure. — A  membranous  muscle  situated  in  the  inter- 
maxillary space,  flattened  from  side  to  side,  elongated  in  the  direction  of  the 
head,  thinner  and  narrower  below  than  above,  and  formed  entirely  of  fleshy  fibres 
which  extend  transversely  from  its  anterior  to  its  posterior  border.  Inferiorly, 
it  is  composed  of  a  small  fasciculus,  which  is  distinguished  from  the  principal 

Fig.  171. 


HYOIDEAL   AND   PHARYNGEAL   REGIONS. 

1,  Neck  of  inferior  maxilla ;  2,  hard  palate  ;  3,  molar  teeth  ;  4,  buccal  membrane ;  5,  submaxillary 
glands ;  6,  soft  palate ;  7,  tendon  of  hyoideus  magnus  through  which  the  tendon,  8,  of  the 
digastricus  passes;  9,  lower  portion  of  digastricus  ;  10,  stylo-hyoideus ;  11,  buccal  nerve;  12, 
zygomatic  arch;  13,  orbital  branch  of  fifth  pair  of  nerves;  14,  articular  process  of  temporal 
bone;  15,  right  cornu  of  hyoid  bone;  16,  hyo-glossus  longus,  or  Kerato-glossus  ;  17,  lingual 
nerve;  18,  18,  tongue;  19,  angle  of  left  branch  of  inferior  maxilla;  20,  submaxillary  gland, 
left  side  ;  21,  subscapulo-hyoideus  ;  22,  great  hypoglossal  nerve  ;  23,  hyo-thyroideus  ;  24,  sterno- 
hyoideus ;  25,  sterno-thyroideus ;  26,  subscapulo  hyoideus ;  27,  thyroid  gland ;  28,  external 
carotid  artery ;  29,  pneumogastric  nerve  ;   30,  stylo-hyoideus  ;   31,  genio-hyoideus. 

portion  by  the  slightly  different  direction  of  its  fibres,  and  which  covers  in  part 
the  external  surface  of  the  muscle. 

Attachments. — It  originates  from  the  mylo-hyoid  line  by  the  anterior 
extremities  of  its  fibres.  Its  movable  insertion  takes  place  on  the  inferior  face 
of  the  hyoid  body,  on  its  anterior  appendix,  and  on  a  fibrous  raph6  which  extends 
from  the  free  extremity  of  this  appendix  to  near  the  genial  surface,  and  which 
unites,  on  the  median  line,  the  two  mylo-hyoidean  muscles. 

Relations. — By  its  external  face,  with  the  inferior  maxilla,  the  digastricus, 
and  the  submaxillary  lymphatic  glands.  By  its  internal  face,  with  the  sublingual 
gland,  the  Whartonian  duct,  the  hypoglossal  and  lingual  nerves,  the  genio-glossus, 
hyo-glossus  longus  and  brevis,  and  genio-hyoideus.  Its  superior  border  responds 
to  the  internal  pterygoid. 

Action. — In  uniting  on  the  median  line  with  that  of  the  opposite  side,  this 


288  THE  MUSCLES. 

muscle  fonns  a  kind  of  wide  band  or  brace  on  which  the  tongue  rests.     "When  it 
contracts,  it  elevates  this  organ,  or  rather  applies  it  against  the  palate. 

2.  Genio-hyoideus. 

Form — Strmture — Situation. — ^A  fleshy,  elongated,  and  fusiform  body,  tendinous 
at  its  extremities,  but  especially  at  the  inferior  one,  and  applied,  with  its  fellow 
of  the  opposite  side,  to  the  mylo-hyoidean  brace. 

Attachments. — By  its  inferior  extremity  it  is  fixed  to  the  genial  surface — 
origin  ,-  by  its  superior,  it  reaches  the  free  extremity  of  the  anterior  appendix  of 
the  hyoid  body — termination. 

Relations. — Outwards  and  downwards,  with  the  mylo-hyoideus  ;  inwards,  with 
its  fellow,  which  is  parallel  to  it ;  above,  with  the  genio-glossus. 

Action. — It  draws  the  hyoid  bone  towards  the  anterior  and  inferior  part  of 
the  intermaxillary  space. 

3.  Stylo-hyoideus. 

Synonyms. — The  hyoideus  magnus  of  Percivall.     The  kerato-hyoidetis  magnus  of  Leyh. 

Form — Structure — Situation — Direction. — Thin  and  fusiform,  this  muscle, 
smaller  than  the  preceding,  and,  like  it,  tendinous  at  both  its  extremities,  is 
situated  on  the  side  of  the  laryngo-phaiyngeal  apparatus  and  the  guttural  pouch, 
behind  the  large  branch  of  the  hyoid  bone,  the  direction  of  which  it  follows. 

Attachments. — Above,  to  the  superior  and  posterior  angle  of  the  styloid  bone — 
Hxed  insertion ;  below,  to  the  base  of  the  comu  of  the  os  hyoides — movable  insertion. 

Relations. — Outwards,  with  the  pterygoideus  intemus ;  inwards,  with  the 
gattural  pouch,  the  pharynx,  and  hypoglossal  nerve.  Its  anterior  border  is 
separated  from  the  posterior  border  of  the  styloid  bone  by  the  glosso-facial  artery 
and  glosso-phaiyngeal  nerve ;  along  the  posterior  border  lies  the  upper  belly  of 
the  digastricus.  Its  inferior  tendon  is  perforated  by  a  ling  for  the  passage  of  the 
cord  intermediate  to  the  two  portions  of  the  latter  muscle. 

Action. — It  is  antagonistic  to  the  preceding  muscle,  drawing  the  body  of  the 
hyoid  bone  backwards  and  upwards. 

4.  Kerato-hyoideus  (Hyoideus  Paevus). 

(Synonyms. — This  is  the  hyoideus  parvus  of  Percivall,  and  the  small  kerato-hyoideus  of 
Leyh.) 

A  very  small  fasciculus,  triangular  in  shape,  and  flattened  on  both  sides.  In- 
serted, on  one  side,  into  the  posterior  border  of  the  styloid  comu  and  the  inferior 
extremity  of  the  styloid  bone  ;  and  on  the  other,  to  the  superior  border  of  the 
thyi'oid  cornu.  It  responds,  outwardly,  to  the  hyo-glossus  brevis  and  the  lingual 
artery  ;  inwardly,  to  the  buccal  mucous  membrane. 

It  approximates  the  cornua  of  the  os  hyoides  to  each  other. 

5.   OCCIPITO-STYLOIDEUS. 

Synonyms.— This  is  the  muscle  which,  up  to  the  present  time,  has  been  described  by 
veterinary  anatomists  as  the  stylo-hyoideus.  This  name  has  been  given  to  the  muscle  named 
by  Girard  the  kerato-hyoideus  magnus. 

A  small,  flat,  and  triangular  muscle  hke  the  preceding,  yet  thicker  and  more 
spread,  filling  the  space  comprised  between  the  styloid  process  of  the  occipital 


MUSCLES  OF  THE  TRUNK,  289 

and  the  horizontal  portion  of  the  posterior  border  of  the  styloid  bone.  Its 
fasciculi  become  longer  as  they  are  situated  posteriorly,  are  rather  tendinous,  and 
are  earned  from  one  of  these  bones  to  the  other.  Outwardly,  it  responds  to  the 
parotid  gland  ;  inwardly,  to  the  guttural  pouch,  which  it  covers  for  its  whole 
extent ;  its  posterior  border  is  largely  confounded  with  the  superior  insertion  of 
the  digastricus.  When  this  muscle  acts,  it  causes  the  os  hyoides  to  swing,  caiTy- 
ing  its  inferior  extremity  backwards  and  downwards. 

6.  Hyoideus  Transversus. 

By  this  name  Bourgelat  has  described  a  short  riband  of  parallel  muscular 
fibres,  which  unites  the  superior  extremities  of  the  styloid  cornua,  and  approxi- 
mates them  to  each  other. 

Differential  Characters  of  the  Muscles  of  the  Head  ik  the  other  Animals. 
1.  Facial  Region. 

Ruminants. — There  are  found  in  the  Ox  : 

1.  An  orbicular  muscle  of  the  lips,  analogous  to  that  in  the  Horse. 

2.  A  buccinator  of  the  same  kind  (Fig.  172,  5). 

3.  A  zygomaticus,  stronger  and  redder  than  in  Solipeds.  Its  aponeurosis  of  origin,  covered 
by  the  panniculus,  extends  upon  the  surface  of  the  masseter  muscle  as  far  back  as  the  zygo- 
matic arch,  to  which  it  is  attached  (Fig.  172,  7). 

4.  A  levator  labii  superioris  alsequi  nasi,  continued,  above,  with  the  inferior  border  of  the 
frontal  or  fronto-cuticularis  muscle  ;  and  divided,  inferiorly,  into  two  branches,  which  comprise 
between  them  the  levator  labii  superioris  and  the  dilator  naris  lateralis.  These  two  branches, 
however,  are  not  disposed  as  in  Solipeds,  the  anterior  covering  the  preceding  muscles,  and  the 
posterior,  of  but  little  importance,  passing  beneath  them  to  lose  itself  in  the  substance  of  the 
upper  lip  (Fig.  172,  3). 

5.  A  levator  labii  superioris  proprius,  which  gains  the  middle  of  the  muzzle  by  passing 
along  the  inner  side  of  the  nostrils  (Fig.  172,  1). 

6.  Two  additional  levator  labii  superioris  muscles  to  the  above,  considered  as  accessories  to 
the  first,  and  which  originate  with  it.  Each  terminates  by  a  ramifying  tendon  that  passes 
under  the  nostril  to  mix  in  the  tissue  of  the  upper  lip  (Fig.  172,  1',  1'). 

7.  A  dilator  naris  lateralis,  situated  between  the  supermaxillo-labialis  and  its  two  accessory 
muscles,  and  deriving  its  origin,  in  common  with  these  three  muscles,  in  front  of  the  maxillary 
spine  (Fig.  172,  2). 

8.  A  depressor  labii  inferioris,  confounded  with  the  buccinator,  and  having  no  terminal 
tendon. 

9.  A  levator  menti,  attached  to  the  body  of  the  inferior  maxillary  bone,  as  in  the  Horse, 
by  two  middle  posterior  muscles.  No  anterior  middle  muscle  has  been  found  by  us;  and  it  is 
certain  that  there  is  no  dilator  naris  transversalis  or  dilator  naris  superioris  present. 

In  the  Sheep,  the  levator  labii  superioris  does  not  exist ;  apart  from  this  peculiarity,  there 
is  DO  difference  between  the  facial  mu»cles  of  this  animal  and  the  Ox. 

Pig. — This  animal  has  no  levator  labii  superioris,  or  dilator  naris  transversales  muscles.  The 
dilator  naris  superior  is  present ;  it  is  short,  very  thick,  and  situated  near  the  margin  of  the 
nostrils.  The  levator  labii  superioris  proprius  and  the  dilator  naris  lateralis  are  replaced  by 
three  fleshy  bodies,  nearly  parallel,  lying  on  tiie  side  of  the  face.  The  superior  originates  in 
the  lachrymal  fossa,  and  terminates  by  a  tendon  in  the  middle  of  the  snout.  The  inferior,  with 
the  middle,  leaves  the  imprints  in  front  of  the  zygomatic  ridge,  and  is  continued  at  its  inferior 
extremity  by  a  tendon  divided  into  several  fibrillse,  which  pass  below  the  nostril  to  be  united 
to  the  tendon  of  the  superior  portion :  this  is  done  in  such  a  manner  that  the  external  opening 
of  the  nose  is  encircled  on  the  inner  side  by  a  kind  of  fibrous  cravat,  which,  when  these  two 
muscles  contract,  carries  this  opening  outwards.  It  will  also  be  understood  that  the  superior 
fleshy  body,  acting  alone,  ought  to  elevate  the  snout,  while  the  inferior  depresses  it  in  drawing 
it  to  one  side.  With  regard  to  the  intermediate  fleshy  mass,  it  is  the  representative  of  the 
dilator  naris  lateralis  of  the  Ox,  and  terminates  in  a  great  quantity  of  tendinous  fibrillae  at 
the  internal  ala  of  the  nose. 

Camivora. — In  the  Dog  and  Cat  the  following  peculiarities  are  found : — 

The  orbicularis  oris  is  quite  rudimentary. 


290  THE  MUSCLES. 

The  buccinator  is  very  thin,  and  formed  of  only  one  muscular  plane. 

The  zyijomaticus  is  continued,  superiorly,  with  the  attollens  anticus. 

The  levator  lahii  superioris  represents  a  wide,  undivided,  muscular  expansion,  united 
superiorly  to  the  panniculus  of  the  forehead,  and  terminating  inferiorly  on  the  upper  lip. 

The  levator  lahii  superioris  and  dilator  naris  lateralis  constitute  a  single  fleshy  body  formed 
of  several  parallel  fasciculi,  which  take  their  origin  above  the  supra-orbital  foramen,  and 
terminate  together  at  the  external  wing  of  the  nose  and  in  the  upper  lip. 

There  is  no  dilator  naris  superioris,  or  dilator  naris  transversalis. 

The  middle  anterior  (depressor  alx  nasi)  is  perfectly  developed. 

The  mento-labialis  and  its  suspensory  muscle,  the  middle  posterior,  are  scarcely  apparent. 

2.  Palpebral  Region. 
The  lachrymalis  in  the  Ox  is  more  developed  and  thicker  than  in  the  Horse.     Its  most 
anterior  fibres  glide  under  the  zygomaticus,  and  are  lost  on  the  surface  of  the  buccinator ;  while 

Fig.  172. 


SUPERFICIAL  MUSCLES   OF   THE   OX'S   HEAD. 

1,  Dilator  naris  superioris  ;  1,  1',  accessory  fasciculi  of  the  same  ;  2,  dilator  naris  lateralis  ;  levator 
labii  superioris  ;  4,  lachrymalis;  5,  depressor  labii  inferioris  ;  6,  buccinator  confounded  with  the 
preceding;  7,  zygomatico-labialis;  8,  frontal,  or  cuticularis  muscle  of  the  forehead ;  9,  orbicular 
muscle  of  the  eyelids;  10,  zygomaticus;  11,  attollens  maximus;  12,  scutiform  cartilage; 
13,  external  scuto-auricularis ;  14,  mastoid  process;  15,  masseter ;  16,  stylo-hyoideus ;  17, 
digastricus  ;  18,  sterno-maxillary  fasciculus  belonging  to  the  cervical  panniculus;  19,  subscapulo- 
hyoideus;  20,  sterno-maxillaris,  or  mastoideus;  21,  anterior  branch  of  the  superficial  portion  of 
the  mastoido-humeralis ;  22,  superior  branch  of  ditto ;  23,  deep  portion  of  same  muscle ;  24, 
trachelo-atloideus,  peculiar  to  Ruminants  and  Pachyderms ;  25,  great  anterior  straight  muscle 
of  the  head. 


the  most  posterior  pass  above  the  aponeurotic  tendon  of  the  zygomaticus  and  become  confounded 
with  tiie  panniculus.  This  muscle  unites,  above,  with  the  orbicularis  palpebrarum  in  a  more 
intimate  manner  than  in  the  Horse,  so  that  it  is  almost  impossible  to  define  the  limits  of  the 
two  (Fig.  172,  4).     The  lachrymalis  is  absent  in  the  Pig. 

3.  Masseteric  or  Temporo-maxillary  Region. 
In  Ruminants,  the  masseter  and  temporalis  are  not  so  large  as  in  Solipeds.     In  the 
Camivora,  however,  they  offer  a  remarkable  development.     The  origin  of  the  pterygoideus 


MUSCLES  OF  THE  TRUNK. 


291 


internus  in  Ruminants  is  nearer  the  middle  line  than  in  the  Horse.  Its  obliquity  is  also 
greater,  and  the  movements  of  diduction  it  gives  the  lower  jaw  are  more  extensive.  In  all  the 
animals,  other  than  Solipeds,  the  stylo-maxillaris  fasciculus  of  the  digastricus  is  entirely  absent, 
and  the  muscle  has  only  a  single  belly  extending  directly  from  the  occipital  to  the  maxillary 
bone.  In  the  Ox  is  found  a  siball  square  muscle,  formed  of  transverse  fibres,  which  unites  the 
two  digastric  muscles  by  passing  beneath  the  base  of  the  tongue.  This  muscle,  in  contracting, 
may  raise  the  hyoideal  apparatus,  and  in  this  way  supplement  the  tendon  of  the  digastricua 
and  the  inferior  ring  of  the  stylo-hyoideus. 

4.  Hyoideal  Region. 

The  two  flesliy  planes  composing  the  mylo-hyoideus  are  more  distinct  in  Ruminants  than 
in  the  Horse.     The  stylo-hyoideus  of  these  animals  commences  by  a  long  thin  tendon.     The 
muscle  has  no  ring  for  the  passage  of  the  digastricus. 
a  feature  observed  in  all  the  domesticated  animals 
except  Solipeds. 

In  the  Carnivora,  the  stylo-hyoideus,  formed  by 
a  narrow,  very  thin,  and  pale  fleshy  band,  commences 
on  the  mastoid  portion  of  the  temporal  bone  by  a 
small  tendon;  the  lerato-hyoideus  is  remarkable  for 
its  relatively  considerable  volume;  the  occipito- 
styloideus  and  the  hyoideus  transversus  are  absent. 

COMPAEISON   OF    THE   MOSCLES  OF   THE   HuMAN   HeAD 
■WITH   THOSE    OF   THE    DOMESTICATED   AnIMALS. 

In  Man,  there  are  described  as  muscles  of  the 
head,  the  epicranial  muscles,  muscles  of  the  face,  and 
those  of  the  lower  jaw.  The  hyoid  and  digastric 
muscles  are  reckoned  in  the  region  of  the  neck.  Here 
tliey  will  be  placed  in  the  region  of  the  head. 

1.  Epicranial  Muscles. 
The  middle  portion  of  the  human  cranium  is 
covered  by  an  aponeurosis  that  adheres  closely  to  the 
hairy  scalp,  but  glides  easily  on  the  surface  of  the 
bones.  To  the  circumference  of  this  epicranial 
aponeurosis  are  attached  four  muscles,  which  move 
it.  One  of  them,  attached  behind  to  the  superior 
occipital  curved  line,  is  named  the  occipital  muscle; 
another,  fixed  in  front  of  the  forehead,  is  called  the 
frontal  muscle ;  the  other  two,  double  and  lateral,  are 
inserted  on  the  face  of  the  temporal  bone  (ir  the  ex- 
ternal ear,  and  are  designated  auricular  muscles. 
These  epicranial  muscles  move  the  scalp  forwards, 
backwards,  and  sideways. 

2.  Muscles  of  the  Face. 
These  are  fourteen  in  number,  ten  of  which  are 
found  in  the  domesticated  animals.     We  commence 
by  describing  these  common  muscles  (Fig.  170). 

1.  The  orbicularis  oris,  which  has  a  fasciculus  that 
passes  to  the  skin  from  the  columna  of  the  nose;  this 
fasciculus  is  termed  the  depressor  of  the  columna,  or 
moustache  muscle  (naso  lahialis). 

2.  The  buccinator,  corresponding  to  the  buccinator 
of  animals.  Besides  its  oflSce  in  mastication,  it  takes 
an  important  part  in  the  blowing  of  wind  instruments. 

3.  The  superficial  elevator  of  the  wing  of  the  nose  and  the  upper  Up.  It  resembles  the 
levator  labii  superioris,  descends  from  the  orbital  margin  of  the  supermaxilla,  passes  along  the 
wing  of  the  nose,  and  is  lost  in  the  upper  lip. 

4.  The  deep  elevator  of  the  wing  of  the  nose  and  the  upper  lip,  the  analogue  of  which  is 
found  in  the  dilator  naris  lateralis. 


muscles  of  the  human  head 
(superficial  layer). 
,  Frontal  portion  of  the  occipito-fron- 
talis  ;  2,  its  occipital  portion ;  3,  its 
aponeurosis  ;  4,  orbicularis  palpebra- 
rum ;  5,  pyramidalis  nasi ;  6,  com- 
pressor nasi;  7,  orbicularis  oris;  8, 
levator   labii  superioris  alasque  nasi ; 

9,  levator  labii   superioris    proprius ; 

10,  zygomaticus  minor;  11,  zygo- 
maticus  major ;  12,  depressor  labii 
inferioris ;  13,  depressor  anguli  oris ; 
14,  levator  labii  inferioris ;  15,  super- 
ficial portion  of  masseter  ;  16,  its  deep 
portion ;  17,  attrahens  aurem ;  18, 
buccinator;  19,  attollens  aurem;  20, 
temporal  fascia  covering  temporal 
muscle ;  21,  retrahens  aurem  ;  22, 
anterior  belly  of  the  digastricus,  with 
tendon  passing  through  pulley ;  23, 
stylo-hyoid  muscle ;  24,  mylo-hyoi- 
deus ;  25,  upper  part  of  sterno-mas- 
toid  ;  26,  upper  part  of  trapezius — 
the  muscle  between  25  and  26  is  the 
splenius. 


292  TEE  MUSCLES. 

5.  The  zygomaticus,  the  presence  of  which  is  constant  in  all  species. 

6.  The  small  zygomaticus,  represented  in  the  Horse  by  only  the  small  oblique  fasciculus 
sometimes  found  beueath  the  zygomaticus. 

The  small  zygomaticus  and  the  two  elevators  of  the  lips  are  lachrymal  muscles;  by  their 
simultaneous  contraction  they  express  discontent  and  melancholy.  The  zygomaticus,  on  the 
contrary,  is  the  muscle  of  laughter ;  it  draws  the  commissures  of  the  lips  outwards. 

7.  The  caninus,  or  dilator  naris  lateralis  of  animals,  is  attached  beneath  the  infra-orbital 
foramen,  and  terminates  in  the  skin  of  the  upper  lip. 

8.  The  risorius  of  Santorini. 

9.  The  muscle  of  the  chin  (jnento-lahialis). 

10.  The  myrtiformis,  or  middle  anterior  of  Bourgelat. 

The  other  facial  muscles  of  Man,  whose  analogues  it  is  difBcult  or  impossible  to  find  in 
animals,  are : — 

11.  The  triangularis  of  the  lips,  which  is  inserted  into  the  anterior  face  of  the  inferior 
maxilla,  and  is  carried  upwards  to  the  commissure  of  the  lips.  By  its  contraction  it  gives  the 
face  an  expression  of  melancholy  or  contempt. 

12.  The  quadratus  menti,  which,  after  been  attached  to  the  maxilla  within  the  mental 
foramen,  passes  upwards  on  the  skin  of  the  lower  lip,  which  it  depresses,  and  thus  contributes 
to  the  expression  of  fear  or  dismay. 

13.  The  transversalis  nasi  {comprei<sor  nasi),  a  muscle  which  is  fixed  into  the  supermaxilla 
and  on  the  bridge  of  the  nose,  where  it  is  confounded  with  the  opposite  muscle. 

14.  The  dilator  of  the  ala  of  the  nostril,  a  very  small  triangular  fasciculus  applied  to  the 
external  part  of  the  nostril,  whicli,  by  contracting,  it  elevates. 

3.  Muscles  of  the  Lower  Jaw. 
There  is  nothing  remarkable  to  be  noted  in  tlie  masseter,  temporal,  or  pterygoid  muscles. 
The  upper  belly  of  the  digastricus  is  not  attached  directly  to  the  inferior  maxilla,  as  it  is  in 
Solipeds. 

4.  Hyoideal  Muscles, 

These  are  only  three  in  number : — 

1.  The  mylo-hyoideus. 

2.  The  stylo-hyoideus,  which  commences  at  the  styloid  process  of  the  temporal  bone,  and 
shows  a  ring  for  the  tendon  of  the  digastricus. 

3.  The  genio-hyoideus. 

We  do  not  find  in  Man  the  occipito-styloideus,  kerato-hyoideus,  or  the  hyoideus-transversus. 

Axillary  Region. 

This  comprises  two  muscles,  pairs,  placed  beneath  the  sternum,  in  the  axilla 
which  terminate  on  the  anterior  limb.  These  are  the  superficial  and  deep 
pectorals} 

Preparation. — 1.  Place  the  animal  in  the  first  position.  2.  Unfasten  one  of  the  forelimbs, 
and  allow  it  to  hang,  so  as  to  separate  it  from  the  opposite  one.  3.  Eemove  the  skin  with 
care,  and  dissect,  on  the  side  corresponding  to  the  detached  limb,  the  two  muscles  which  form 
the  superficial  pectoral.  4.  Prepare  the  deep  pectoral  on  the  opposite  side.  To  do  this, 
remove  the  panniculus  cautiously,  so  as  not  to  injure  the  muscle  about  to  be  examined ;  divide 
the  superficial  pectoral  transversely,  and  turn  back  the  cut  portions  to  the  right  and  left ;  divide 
also  the  mastoido-humeralis  and  cervical  trapezius  near  their  insertion  into  the  limb,  and 
reflect  them  upon  the  neck. 

1.  Superficial  Pectoral  (Pectoralis  Anticus  and  Transversus) 
(Figs.  174,  9,  10  ;  175,  3). 

Synonyms. — Muscle  common  to  the  arm  and  {orearm— Bourgelat.  Pectoralis  magnus  of 
Man.  (Percivall  and  Leyh  describe  three  pectorals,  others  four ;  but,  as  will  be  seen  in  this 
work,  the  two  pectorals  are  each  divided  into  two  portions,  which,  for  practical  purposes,  agrees 
with  those  who  describe  four.     This  muscle  is  the  Pectoralis  transversus  of  Percivall.     Leyh 


For  a  justification  of  the  employment  of  tliese  new  denominations,  see  the  note  at  p.  230. 


MUSCLES  OF  THE  TRUNK.  298 

divides  this  muscle  into  two  portions,  which  he  designates  the  sterno-radialis  and  small  sterno- 
humeralis.) 

Situation — Composition. — This  muscle  is  situated  between  the  two  anterior 
limbs,  occupies  the  inferior  surface  of  the  chest,  and  is  formed  by  two  portions 
which  adhere  closely  to  each  other,  but  are  yet  perfectly  distinct.  Following 
the  example  of  Girard,  we  will  describe  these  as  two  particular  muscles  by  the 
names  of  sterno-humeralis,  and  sterno-aponeuroticus . 

A.  Sterno-humeralis  (Pectoralis  ksT\G\5^).— Form— Structure.— T\A%  is 
a  short,  bulky  muscle,  flattened  above  and  below,  contracted  at  its  termination, 
and  composed  almost  entirely  of  thick  parallel  fibres. 

Direction  and  Attachments. — It  commences  on  the  anterior  appendage  and 
the  inferior  border  of  the  sternum,  and  is  directed  obUquely  backwards,  down- 
wards, and  inwards,  to  reach  the  anterior  ridge  of  the  humerus,  where  it 
terminates  by  an  aponeurosis  corumon  to  it,  the  mastoido  humeralis,  and  the 
sterno-aponeuroticus. 

Relations. — Externally,  to  the  skin,  from  which  it  is  separated  by  connective 
tissue,  and  to  the  inferior  extremity  of  the  cervical  panniculus  ;  internally,  to 
the  sterno-aponeuroticus  and  sterno-prescapularis.  Its  anterior  border  forms, 
with  the  mastoido-humerahs,  a  triangular  space  occupied  by  the  subcutaneous, 
or  "  plate,"  vein  of  the  arm. 

Action. — It  acts  principally  as  an  adductor  of  the  anterior  limb. 

B.  Sterno-aponeuroticus  (Pectoralis  Transversus). — Form — Structure 
— Direction — Attachments. — A  very  wide,  thin,  and  pale  quadrilateral  muscle 
formed  of  parallel  fleshy  fibres,  which  arise  from  the  entire  inferior  border  of 
the  sternum,  to  pass  at  first  outwards,  then  downwards,  and  terminate  in  the 
following  manner  :  the  anterior  fibres  go  to  the  aponeurosis  which  attaches  the 
mastoido-humeralis  and  pectoralis  anticus  to  the  anterior  ridge  of  the  humerus  ; 
the  posterior  fibres  are  also  continued  by  a  very  thin  fascia,  which  is  spread 
inside  the  limb  to  the  external  face  of  the  antibrachial  aponeurosis. 

Relations. — By  its  superficial  face,  with  the  skin,  which  adheres  intimately  to 
it  by  means  of  dense  connective  tissue,  and  with  the  pectoralis  anticus,  which 
covers  its  anterior  border.  By  its  deep  face,  with  the  two  portions  of  the  other 
pectoral,  the  flexor  brachii,  and  the  long  extensor  of  •  the  forearm  ;  it  also 
responds,  by  this  face,  to  the  antibrachial  aponeurosis  and  the  subcutaneous  vein 
of  the  forearm,  which  it  maintains  applied  against  that  aponeurosis. 

Action. — It  is  an  adductor  of  the  anterior  limb,  and  a  tensor  of  the  anti- 
brachial aponeurosis. 

2.  Deep  Pectoral  (Pectoralis  Magnus  and  Parvus) 
(Figs.  174,  11,  13  ;  175,  1). 

Synonym. — The  pectoralis  parvus  of  Man 

Volume — Situation — Composition. — An  enormous  muscle,  situated  beneath 
the  thorax,  and  composed,  like  the  preceding,  of  two  perfectly  distinct  portions, 
described  by  Girard  as  two  muscles,  and  designated  by  him  as  the  sterno- 
trochineus  and  sterno-prescapularis. 

A.  Sterno-trochineus. — Pectoralis  magnus  of  (Percivall,  Rigot,  and) 
Bourgelat.     (The  great  sterno-humeraUs  of  Leyh.) 

Volume — Extent. — This  muscle,  the  largest  of  the  two,  is  considerable  in 


294 


TEE  MUSCLES. 


Fiff.  174. 


volume.     Extending  from  the  ninth  or  tenth  rib  to  the  upper  extremity  of  the 
arm,  it  at  first  lies  beneath  and  against  the  abdomen,  then  beneath  the  chesty 

and  at  last  is  comprised  between  the  walls  of 
the  latter  cavity  and  the  internal  face  of  the 
anterior  limb. 

Form. — It  is  thin  and  flat  above  and  below 
in  its  posterior  third,  thicker  and  depressed 
from  side  to  side  in  its  middle  third,  and 
narrow  and  prismatic  in  its  anterior  third. 
Its  general  form  may  be  compared  to  that 
of  a  somewhat  irregular  triangle,  elongated 
from  before  to  behind,  which  would  have  a 
very  short  posterior  border,  a  longer  internal 
or  inferior  border,  and  an  external  or  superior, 
still  more  extensive. 

Structure. — It  is  entirely  composed  of 
thick,  parallel,  fleshy  fasciculi,  all  of  which 
leave  the  posterior  or  internal  border  of  the 
muscle  to  gain  its  narrow  or  anterior  extremity. 
These  fasciculi,  as  they  approach  the  superior 
border,  become  longer,  and  those  which  proceed 
from  the  posterior  border  commence  by 
aponeurotic  fibres.  Unfrequent  intersections 
of  fibrous  tissue  exist  towards  the  anterior 
extremity  of  the  muscle. 

Attachments. — It  originates:  1.  From  the 
tunica  abdominalis  by  the  aponeurotic  fasciculi 
of  its  posterior  border.  2.  By  its  internal 
border,  from  the  posterior  two-thirds  of  the 
inferior  border  of  the  sternum.  It  terminates, 
by  its  anterior  extremity,  on  the  internal 
tubercle  at  the  head  of  the  humerus,  the  tendon 
of    origin  of   the  coraco-humeralis,  and   the 

„^^^ \        n««        fascia  enveloping  the  coraco-radialis.   Through 

^W////  m  ISlllllllllllill        ^^®  medium  of  this  fascia,  it  is  inserted  into 

Wmm  ^^U        ^^^  external  lip  of  the  bicipital  groove  formed 

by  the  external  trochanter,  and  is  united  to 
the  two  terminal  branches  of  the  supra-spinatus 
muscles  (see  Figs.  174,  12  ;  181,  5). 

Relations. — Its  deep  face,  which  is  suc- 
cessively superior  and  internal,  covers  the  ex- 
ternal oblique  and  the  straight  muscle  of 
the  abdomen,  the  serratus  magnus,  lateralis- 
stemi,  and  pectoralis  parvus,  as  well  as  some 
thoraco-muscular  nerves  ;  all  these  relations 
are  maintained  by  means  of  a  loose  and 
abundant  connective  tissue.  Its  superior  face, 
which  alternately  looks  downwards  and  out- 
wards, responds  :  to  the  skin,  from  which  it  is  separated  by  a  slight  cellulo- 
fibrous  fascia  ;  to  the  pectoralis  transversus  ;  and  to  the  muscles,  vessels,  and 


MUSCLES   OF   THE   AXILLARY   AND 
CERVICAL   REGIONS. 

1,  Portion  of  the  cervical  panniculus ; 
2,  anterior  portion  of  the  mastoido- 
humeralis ;  3,  posterior  portion  of 
ditto;  4,  sterno-maxillaris  ;  5,  sub- 
scapulo-hyoideus  ;  6,  7,  sterno-thyro- 
hyoideus  ;  8,  scalenus ;  9,  pectoralis 
anticus ;  10,  pectoralis  transversus  ; 
11,  pectoralis  magnus;  12,  portion 
of  the  fascia- enveloping  the  coraco- 
radialis,  receiving  part  of  the  fibres 
of  the  pectoralis  magnus;  13,  pec- 
toralis parvus  ;  14,  its  terminal 
aponeurosis. 


MUSCLES   OF  THE  TEUNK.  295 

nerves  of  the  inner  aspect  of  the  arm,  through  the  medium  of  the  sub-brachial 
aponeurosis  of  the  panniculus  and  a  considerable  quantity  of  connective  tissue. 
Its  upper  border  adheres  in  an  intimate  manner  to  the  last-named  muscle,  and  is 
bordered  by  the  spur  (external  thoracic)  vein.  The  large  vascular  trunks  which 
leave  the  chest  to  reach  the  anterior  limb,  pass  above  its  anterior  extremity,  in 
crossing  its  direction. 


Action. — It  puUs  the  whole  limb  backwards,  in  pressing  on  the  angle  of  the 
shoulder. 

B.  Sterno-peescapulakis. — (The  pectoralis  parvus  of  Percivall  and  Bour- 
gelat.)— Form — Situation — Direction.— A  long  prismatic  muscle,  contracted  at  its 
two  extremities,  situated  in  front  of  the  preceding,  arising  from  the  sternum, 
directed  forwards  and  outwards  towards  the  scapulo-humeral  angle,  and  after- 
wards reflected  upwards  and  backwards  on  the  anterior  border  of  the  shoulder, 
which  it  foUows  to  near  the  cervical  angle  of  the  scapula. 

Structure  and  Attachments. — It   is   formed   of   very  large   fleshy   fasciculi. 


296  THE  MUSCLES. 

analogous  to  those  of  the  pectoraUs  magnus,  which  originate,  by  their  inferioi 
extremities,  from  the  sides  of  the  sternal  keel  and  the  cartilages  of  the  first 
three  or  four  ribs.  They  follow  the  direction  of  the  muscle,  and  terminate,  one 
above  the  other,  on  a  short  aponeurosis  which  covers  the  supra-spinatus,  and  is 
confounded  with  the  external  aponeurosis  of  the  scapula  (Fig.  174,  14). 

Relations. — In  its  axillary  portion,  this  muscle  responds,  inwardly,  to  the 
lateralis  sterni,  the  first  sternal  cartilages,  and  the  corresponding  intercostal 
muscles  ;  outwards,  to  the  pectoralis  magnus  and  transversus.  In  its  prescapular 
portion,  it  is  in  relation,  outwardly,  with  the  mastoido-humeralis  and  trapezius  ; 
inwardly,  with  the  subscapulo-hyoideus,  the  scalenus,  and  the  angularis  of  the 
scapula ;  behind,  with  the  supra-spinatus,  which  is  separated  from  it  by  the 
external  scapular  aponeurosis. 

Action. — This  muscle  is  a  congener  of  the  pectoralis  magnus,  and  pulls 
the  scapula  backwards  and  downwards.  It  is  also  a  tensor  of  the  scap|j|ar 
aponeurosis. 

DiETERENTIAL   ChABAOTERS  IN   THE   MuSCLES  OF   THE   AXILLARY   REGION   IN   THE 

OTHER  Animals. 

With  regard  to  the  pectoralis  anticus  and  transversus,  it  is  remarked  that  in  the  Ox, 
Sheep,  and  Pig,  the  former  is  small  and  less  distinct  from  the  latter  than  in  Solipeds ;  and 
that  in  the  Dog  and  Cat,  the  latter  is  very  thin  and  narrow. 

In  the  Ox,  the  pectoraUs  parvus  is  scarcely  distinct  from  the  pectoralis  magnus,  and 
which  does  not  extend  beyond  the  inferior  extremity  of  the  supra-spinatus.  In  the  Sheep, 
this  muscle  is  quite  confounded  with  the  pectoralis  magnus.  In  the  Pig,  the  pectoralis  parvus 
resembles  that  of  the  Horse.  Its  inferior  extremity  only  covers  the  first  clirondo-sternal 
articulation ;  the  superior  extremity  is  more  voluminous.  With  regard  to  the  pectoralis 
magnus,  it  terminates  on  the  summit  of  the  external  trochanter,  after  detaching  a  short  branch 
to  the  tendon  of  the  coraco-humeralis.  The  pectoralis  parvus  of  the  Dog  is  very  feeble,  and 
terminates  with  the  principal  muscle  on  the  humerus. 

Costal  Region. 

In  each  costal  region  we  find  fifty-three  muscles,  which  concur,  more  or  less 
directly,  in  the  respiratory  movements.  These  muscles  are  :  1.  The  serrafus 
magnus.  2.  Seventeen  external  intercostals.  3.  Seventeen  internal  intercostals. 
4.  Seventeen  levatores  costarum.     5.  The  triangularis  sterni.^ 

Preparation. — 1.  Place  the  subject  in  the  second  position.  2.  Remove  the  fore  limb  and 
all  the  muscles  attaching  it  to  the  trunk,  by  sawing  through  tlie  scapula  as  shown  in  Fig. 
162,  in  order  to  expose  the  serratus  magnus;  finish  the  dissection  by  taking  away  all  the  yellow 
fibrous  tissue  which  covers  its  posterior  dentations.  3.  Study  the  external  intercostals  and 
the  levatores  costarum,  after  removing  the  great  oblique  muscle  of  the  abdomen,  the  serrati 
muscles,  the  transversalis  costarum,  and  the  longissimus  dorsi.  4.  Excise  some  external 
intercostals  in  order  to  show  the  corresponding  internal  ones.  5.  The  triangularis  sterni  is 
dissected  on  another  portion,  wliich  is  obtained  in  separating  the  sternum  from  the  thorax, 
by  sawing  through  the  sternal  ribs  a  little  above  their  inferior  extremity. 

1.  Sereatus  Magnus  (Fig.  162,  15). 

Synonyms. — Costo-subacapularis — Grirard.  Posterior  portion  of  the  serratus  magnus  of 
Bourgelat.     (A  portion  of  Percivall's  serratus  magnus.) 

Form — Situation. — A  very  wide  muscle,  disposed  like  a  fan,  split  up  into 

'  Veterinary  anatomists  describe  in  this  region  a  muscle  which  they  designate  the  costo- 
gternalis,  lateralis  sterni,  or  transveralis  costarum,  but  we  consider  it  a  fasciculus  detached  from 
the  rectus  abdominis  (see  Inferior  Abdominal  Region). 


MUSCLES  OF  THE  TRUNK.  297 

digitations  at  its  inferior  border,  applied  against  the  thoracic  walls,  and  partly 
concealed  by  the  shoulder. 

Structure.— It  is  composed  of  divergent  fleshy  fibres,  all  of  which  converge 
towards  the  superior  extremity  of  the  scapula,  and  are  covered  by  a  very  strong 
aponeurosis  that  gradually  diminishes  from  above  to  below,  and  only  adheres  to 
the  muscle  in  its  inferior  part. 

Attachments.— \.  To  the  external  face  of  the  eight  sternal  ribs.  2.  To  the 
anterior  triangular  surface  of  the  internal  face  of  the  scapula,  behind  the 
angularis,  with  which  it  is  confounded.  3.  To  the  whole  extent  of  the  posterior 
triangular  surface  of  that  bone. 

On  reaching  the  scapula,  the  aponeurosis  separates  from  the  fleshy  fibres,  and 
is  inserted  alone  into  the  fibrous  plane  which  covers  the  muscular  fasciculi  of  the 
subscapularis. 

i^eZaftows,— Outwardly,  and  through  the  medium  of  an  abundant  supply  of 
connective  tissue,  which  facilitates  the  play  of  the  limb  against  the  lateral  wall 
of  the  thorax,  to  the  subscapularis,  supra-spinatus,  adductor  of  the  arm,  latissimus 
dorsi,  and  the  mass  of  olecranian  muscles  ;  inwardly,  to  the  first  seven  external 
intercostals,  to  the  sides  of  the  sternum,  and  to  the  anterior  small  serratus.  Its 
four  posterior  digitations  cross  the  first  five  of  the  great  oblique  muscle  of  the 
abdomen,  and  are  covered  by  a  prolongation  of  the  abdominal  tunic. 

Action. — With  that  of  the  opposite  side,  this  muscle  constitutes  a  vast  brace 
or  girth  on  which  the  thorax  rests  when  the  animal  is  supported  on  its  anterior 
limbs  ;  it  therefore  acts,  in  relation  to  the  trunk,  as  a  suspensory  ligament. 
When  it  contracts,  its  fixed  point  being  the  thoracic  walls,  it  pulls  the  superior 
extremity  of  the  scapula  downward  and  backward,  and  causes  this  portion  of  the 
limb  to  perform  a  swinging  movement  which  carries  the  inferior  angle  upwards 
and  forwards.  If  the  limb  is  the  fixed  point,  then  it  raises  the  thorax  between 
the  two  anterior  limbs,  and  assists  in  the  respiratory  movements  by  elevating 
the  ribs. 

2.  External  Intercostals  (Figs.  161,  162). 

Situation — Form. — These  muscles  fill  the  spaces  between  the  ribs,  but  do  not 
descend  beyond  their  inferior  extremities  ;  they,  therefore,  do  not  occupy  the 
intervals  between  the  cartilages.  They  are  flattened,  fleshy  bands,  gradually 
diminishing  in  thickness  from  above  to  below. 

StriKture — Attachments. — Each  external  intercostal  muscle  is  composed  of  a 
series  of  muscular  fasciculi,  intermixed  with  numerous  aponeurotic  fibres,  both 
of  which  pass  obliquely  backwards  and  downwards,  from  the  posterior  border  of 
the  preceding  to  the  external  face  of  the  succeeding  rib. 

Relations. — Outwardly,  to  the  different  muscles  applied  against  the  thoracic 
walls  ;  inwardly,  to  the  internal  intercostals. 

3.  Internal  Intercostals  (Fig.  163,  16). 

These  are  placed  at  the  internal  face  of  the  preceding,  which  they  exactly 
repeat  with  regard  to  their  general  form,  but  from  which  they  differ  in  the 
following  points  : — 

1.  Very  thick  between  the  costal  cartilages,  these  muscles  are  reduced  at  the 
upper  part  of  the  intercostal  spaces  to  a  thin  aponeurotic  layer,  supported  only 
by  some  fleshy  fibres.  They,  therefore,  gradually  diminish  in  thickness  from 
below  upwards. 


298  THE  MUSCLES. 

2.  Their  fasciculi  are  less  tendinous  than  those  of  the  external  intercostals, 
and  are  carried  obliquely  forward  and  downward,  from  the  anterior  border  of 
the  posterior  rib  to  the  posterior  border  and  internal  face  of  the  rib  in  front ; 
so  that  the  fibres  of  the  external  and  internal  intercostals  cross  each  other  like 
the  letter  X. 

3.  Outwardly,  they  respond  to  the  external  intercostals ;  inwardly,  to  the 
costal  pleura. 

Action  of  the  intercostal  muscles. — The  function  of  these  muscles  has  been  for 
a  long  time,  and  is  even  now,  much  discussed  ;  and  it  may  be  said  that  there 
were  never,  perhaps,  more  diverse  or  contrary  opinions  given  on  any  subject 
than  on  this,  Berard,  who  has  summed  up  the  elements  of  the  discussion 
with  the  greatest  judgment,  considers  the  external  intercostals  as  inspiratoiy 
muscles,  and  the  internal  ones  also  as  inspiratory  by  those  fasciculi  which  occupy 
the  spaces  between  the  costal  cartilages  ;  the  remainder,  the  majority,  are 
expiratory. 

4.  Levatores  Costarum. 

Synonyms. — Transverso-costales — Girard. 

Small,  flat,  triangular,  muscular,  and  tendinous  fasciculi,  constituting,  it 
might  be  said,  the  heads  of  the  external  intercostals,  from  which  they  are 
scarcely  distinguishable  in  the  first  and  last  costal  intervals. 

They  arise  from  the  transverse  processes  of  the  doi-sal  vertebras,  and  are 
directed  backwards  and  outwards,  gradually  expandmg,  to  terminate  on  the 
external  face  of  the  one  or  two  ribs  which  succeed  their  fixed  insertion.  Out- 
wardly, they  are  in  contact  with  the  longissimus  dor  si ;  inwardly,  with  the 
external  intercostals. 

The  levatores  costarum  draw  the  ribs  forward,  and  are  consequently  inspu-atory 
muscles. 

5.  Triangularis  Sterni. 

Synonyms. — Sternalis — Bourgelat.  Sterno-costalis — Girard.  (The  sterno-costales  of  Per- 
civall,  and  sterno-costalis  of  Leyh.) 

Form — SitvMtion. — This  muscle,  flattened  above  and  below,  elongated  from 
before  to  behind,  and  dentated  at  its  external  or  superior  border,  is  situated  in 
the  thoracic  cavity,  above  the  sternum  and  the  cartilages  of  the  true  ribs. 

Attachments. — It  is  fixed,  by  its  internal  border,  on  the  superior  face  of  the 
sternum,  to  the  ligamentous  cord  which  circumscribes  it  outwardly.  It  has  its 
movable  insertion  on  the  cartilages  of  the  sternal  ribs,  the  first  excepted,  by 
means  of  digitations  from  its  external  border. 

Structure. — It  is  formed  of  strongly  aponeurotic  muscular  fasciculi,  which 
are  directed  from  the  internal  to  the  external  border. 

Relations. — Inwardly,  with  the  pleura ;  outwardly,  with  the  cartilages  to 
which  it  is  attached,  the  internal  intercostals,  and  the  internal  thoracic  vein  and 
artery. 

Action. — The  triangularis  of  the  sternum  concurs  in  expiration,  by  depressing 
the  costal  cartilages.  (Leyh  asserts  that  if  the  fixed  point  be  the  sternum,  this 
muscle  pulls  the  ribs  forwards,  and  so  widens  the  thorax  ;  but  if  the  fixed  point 
is  the  ribs,  the  sternum  will  be  raised  and  the  thoracic  space  diminished.) 


MUSCLES  OF  THE  TRUNK.  299 

Differential  Characters  in  the  Muscles  of  the  Costal  Region  in  the  other 
Animals. 

The  muscles  of  the  costal  region  caunot  be  tlie  same  ia  number  in  all  the  domesticated 
animals ;  the  intercostals  and  levatores  costarum,  for  instance,  must  vary  in  number  with  that 
of  the  ribs.  Beyond  this,  the  differem^es  are  slight.  In  the  Ox,  the  serratus  magnus  is  very 
extensive,  and  the  portion  which  passes  to  the  posterior  triangular  surface  of  the  scapula  is 
readily  distinguished  from  the  anterior  by  its  diminished  thickness,  the  larger  proportion  of 
aponeurotic  iibres  it  contains,  and  the  flattened  tendon  by  means  of  which  it  is  inserted.  In 
the  Pig,  it  is  remarked  that  the  internal  intercostals  are  prolonged— maintaining  a  certain 
thickness — to  near  the  vertebral  spine. 

Comparison  of  the  Thoracic  Muscles  of  Man  with  those  of  the  Domesticated 
Animals. 

The  muscles  of  the  axillary  and  costal  regions  and  the  diaphragm,  are  named  the  thoracic 
muscles  in  Man. 

The  pectoral  muscles  are  distinguished  into  great  and  small.  The  pectoralis  magnus  corre- 
sponds to  the  pectoralis  anticus  and  trausversus  of  the  Horse.  It  is  attached,  on  one  side,  to 
the  inner  two-thirds  of  the  clavicle,  the  anterior  face  of  the  sternum,  and  the  cartilages  of  the 
first  six  ribs ;  on  the  other,  to  the  anterior  border  of  the  bicipital  groove,  and,  by  a  fibrous 
expansion,  to  the  aponeurosis  of  the  arm.  The  costal  fasciculi  are  distinctly  separated  from 
the  clavicular  atid  sternal  fasciculi 

The  small  pectoral,  which  corresponds  to  tlie  pectoralis  magnus  and  parvus,  is  inserted,  on 
the  one  part,  into  the  external  face  of  the  third,  fourth,  and  fifth  ribs ;  on  the  other  part,  by  a 
tendon  to  the  anterior  border  of  the  coracoid  process. 

In  Man,  there  is  found  a  muscle  whicli  does  not  exist  in  animals;  this  is  the  subdavius,  a 
very  slender  fasciculus  situated  beneath  the  clavicle,  and  attached  to  the  cartilage  of  the  first 
rib  and  the  external  portion  of  the  lower  face  of  the  clavicle  (see  Fig  164,  5). 

The  serratus  magnus  does  not  show  any  distinct  aponeurosis  on  its  surface ;  it  arises  from 
the  eight  first  ribs,  and  its  digitations  are  grouped  into  three  princip;d  fasciculi. 

Lastly,  in  Man  the  internal  intercostals  are  prolonged  to  the  vertebral  column  by  small 
muscles,  named  intra-costals.  • 

INFERIOR   ABDOMINAL   REGION. 

The  lateral  and  inferior  walls  of  the  abdominal  cavity  are  formed  by  a  wide 
musculo-aponeurotic  envelope,  which  rests,  by  its  periphery,  on  the  sternum, 
ribs,  lumbar  vertebrae,  ilium,  lumbo-iliac  aponeurosis,  and  the  pubis.  This 
envelope  is  concave  on  its  superior  surface,  and  results  from  the  assemblage  of 
four  pairs  of  large  membraneous  muscles  aiTanged  in  superposed  layers.  Reckon- 
ing them  from  without  inwards,  these  are  designated  the  (/reat,  or  external  oblique, 
the  small,  or  internal  oblique,  the  great  straight,  and  the  transverse  muscle. 
Covered  outwardly  by  an  expansion  of  yellow  fibrous  tissue — the  tunica  abdomi- 
nalis — and  separated  from  those  of  the  opposite  side  by  the  linea  alba — a  medium 
raphe  extending  from  the  sternum  to  the  pubis — these  muscles  support  the 
intestinal  mass,  and  by  their  relaxation  or  contraction  adapt  themselves  to  the 
variations  in  volume  which  these  viscera  may  experience. 

Preparation.—Miex  placing  the  animal  in  the  first  position,  a  wide  opening  is  to  be  made 
in  the  pectoral  cavity  by  the  ablation  of  a  certain  number  of  ribs,  which  should  be  divided 
inferiorly,  above  the  costal  attachments  of  the  great  oblique  muscle.  The  heart  and  lungs  are 
removed;  then  an  incision  is  made  in  the  diaphragm,  to  allow  the  digestive  viscera  contained 
in  the  abdominal  cavity  to  be  taken  away.  It  is  not  absolutely  necessary,  however,  to  empty 
that  cavity,  and  if  its  contents  be  allowed  to  remain,  several  punctures  should  be  made  in  the 
large  intestine  to  prevent  the  accumulation  of  gas,  and  the  too  great  distension  of  the  abdominal 
parietes. 

These  preliminary  precautions  having  been  adopted,  then  proceed  in  the  following 
manner : — 


SOO  TEE  MUSCLES. 

1.  Remove  the  skin  from  tliis  region,  and  with  it  the  panniculus  carnosus,  in  order  to  study 
the  external  surface  of  the  abdominal  tunic.  2.  The  dissection  of  the  great  oblique  muscle  is 
accomplished  by  removing  the  yellow  fibrous  envelope  from  the  fleshy  portion  of  the  muscle, 
together  with  the  sterno-trochineus.  The  inguinal  ring  should  be  exposed  by  the  ablation  of 
the  dartos  muscle,  the  sheath  and  penis,  or  the  mammae.  3.  On  the  opposite  side,  the  small 
oblique  is  uncovered  by  excising  the  great  oblique,  leaving,  however,  that  portion  of  the 
aponeurosis  which  is  mixed  up  with  that  of  the  first  muscle.  4.  The  latter  having  been 
studied,  dissect  the  great  straight  muscle  of  the  abdomen  on  the  same  side,  in  separating  from 
the  white  line,  by  a  longitudinal  incision,  the  aponeurosis  common  to  the  two  oblique  muscles, 
dividing  this  aponeurosis  and  the  fleshy  portion  of  the  internal  oblique  by  another  incision 
extending  transversely  from  the  umbilicus  to  the  middle  of  the  lumbar  region,  and  laying  back 
one  of  the  musculo-aponeurotic  suctions  on  the  thigh,  the  other  on  the  ribs.  5.  The  transverse 
muscle  is  dissected  on  the  same  side  as  the  external  oblique  lias  been.  To  expose  it,  nothing 
more  is  necessary  than  to  make  two  incisions  similar  to  the  foregoing,  but  including  the  two 
oblique  and  the  straight  muscle,  throwing  back  the  two  portions  as  above.  6.  Lastly,  open 
the  entire  abdominal  cavity  by  cutting  through  the  transverse  muscle  in  the  same  way;  then 
study  the  muscular  digitations  of  that  muscle,  the  internal  orifice  of  the  inguinal  canal,  and 
the  layer  reflected  from  the  aponeurosis  of  the  great  oblique  muscle. 

1.  Abdominal  Tunic  (Tunica  Abdominalis,  Tunica  Elastica). 

The  vast  expansion  of  yellow  elastic  fibrous  tissue  spread  over  the  two 
external  oblique  muscles  of  the  abdomen  is  so  named. 

Very  thick  towards  the  prepubic  tendon  of  the  abdominal  muscles  and  in  the 
vicinity  of  the  linea  alba,  this  expansion  gradually  thins  as  it  approaches  the 
sternum,  and  disappears  near  the  abdominal  insertion  of  the  pectoralis  magnus. 
It  also  diminishes  in  thickness  as  it  extends  from  the  linea  alba  ;  and  when  it 
reaches  the  fleshy  portion  of  the  great  oblique  muscle  it  becomes  reduced  to  an 
extremely  thin  layer,  the  fasciculi  of  which  separate  more  and  more  from  one 
another,  until  they  completely  disappear.  Anteriorly,  however,  it  is  seen  to  be 
prolonged  on  each  side  to  the  posterior  digitations  of  the  serratus  magnus. 
Posteriorly,  it  furnishes  some  bundles  of  fibres,  which  are  detached  from  the 
surface  of  the  common  tendon,  and  are  carried  between  the  thighs  to  be  lost  on 
the  internal  crural  muscles. 

The  abdominal  tunic  is  covered  by  the  skin  and  panniculus  carnosus,  from 
which  it  is  separated  by  an  abundance  of  connective  tissue.  In  the  male,  its 
external  surface  gives  attachment  to  the  suspensory  ligaments  of  the  prepuce, 
and  to  the  dartos  ;  and  in  the  female,  to  the  elastic  capsule  which  envelops  each 
mammary  gland.  By  its  internal  face,  it  closely  adheres  to  the  aponeurosis  of 
the  great  oblique  muscle  ;  though  it  is  easily  separated  from  the  fleshy  portion. 
It  is  traversed  by  several  openings,  which  aflford  passage  to  the  subcutaneous 
vessels  and  nerves  of  the  abdominal  region. 

Use. — The  abdominal  tunic  acts  as  an  immense  elastic  girth  or  bandage, 
which  aids  the  muscles  in  sustaining  the  weight  of  the  intestines.  As  the 
digestive  organs  increase  in  volume,  this  tunic  increases  in  thickness. 

In  the  Pig,  Dog,  and  Cat,  it  is  reduced  to  a  simple  cellulo-aponeurotic  layer,  owing  to 
the  stomach  and  intestines  in  these  animals  exercising  but  a  small  amount  of  pressure  on  the 
abdominal  parietes. 

2.  White  Line  (Linea  Alba). 

The  white  line  (lima  albn)  is  a  fibrous  cord  comprised  between  the  internal 
border  of  the  two  great  straight  muscles,  and  is  considered  as  beiQg  foiToed  by 
the  intercrossing,  on  the  median  line,  of  the  aponeuroses  belonging  to  the  oblique 
and  transverse  muscles.    Attached,  in  front,  to  the  inferior  sm'face  of  the  xiphoid 


MUSCLES  OF  THE  TRUNK.  301 

appendage,  this  cord  is  confounded,  behind,  with  a  large  tendon,  the  fr&pubic  or 
common  tendon  of  the  abdominal  muscles,  which  is  fixed  to  the  anterior  border  of 
the  pubis  (Figs.  140,  a  ;  176, 10).  This  tendon,  covered  by  the  abdominal  tunic, 
contributes  to  form  the  internal  commissure  of  the  inguinal  ring,  and  gives 
origin  to  the  pubio-femoral  ligament. 

Towards  the  union  of  its  posterior  third  with  its  two  anterior  thii'ds,  the 
white  line  widens,  so  as  to  form  a  lozenge-shaped  space,  in  the  centre  of  which  is 
found  the  remains  of  the  umbiHcus  and  the  umbilical  cord  (Fig.  147,  o). 

3.  Geeat  Oblique,  or  External  Oblique  of  the  Abdomen  (Obliquus 
Abdominis  Externus)  (Figs.  162,  18  ;  176,  1). 

Synonyms.     Oosto-abdominalis—  Girard. 

Situation — Composition. — This  muscle,  the  largest  and  the  most  superficial  of 
the  four,  is  situated  on  the  side  and  floor  of  the  abdomen,  and  is  composed  of  a 
fleshy  and  an  aponeurotic  portion. 

Form^  Structure,  and  Attachments  of  the  fleshy  portion. — This  is  composed  of 
fibres  directed  obliquely  downwards  and  backwards,  and  presents  itself  as  a  wide 
muscular  band,  narrower  before  than  behind,  applied  to  the  inferior  surface  of 
the  last  thirteen  or  fourteen  ribs.  Its  superior  border  is  concave,  and  attached  : 
1.  To  the  external  surface  of  the  ribs  just  mentioned  by  as  many  slightly 
aponeurotic  digitations,  the  first  four  of  which  cross  the  dentations  of  the  great 
serratus.  2.  To  the  aponeurosis  of  the  latissimus  dorsi,  from  the  last  rib  to  the 
external  angle  of  the  ilium  (Fig.  162,  18).  Its  inferior  border,  convex  and 
sinuous,  is  continuous  with  the  aponeurosis  ;  it  descends,  in  front,  to  the  cartila- 
ginous circle  of  the  false  ribs,  which  it  projects  beyond  posteriorly,  increasing  in 
this  as  it  nears  the  lumbar  region. 

Form,  Structure,  and  Attachments  of  the  Aponeurosis. — This  is  narrow  and 
thin  in  front,  wide  and  thick  behind,  of  a  triangular  form,  and  composed  of 
white,  nacrous-looking  fibres  passing  in  the  same  direction  as  the  fibres  of  the 
fleshy  portion,  with  the  inferior  border  of  which  it  is  continuous  by  its  external 
border.  Its  internal  border  is  inserted  into  the  white  Une  and  the  prepubic 
tendon  ;  and  its  posterior  border,  extending  from  the  external  angle  of  the  ilium 
to  the  anterior  border  of  the  pubis,  responds  to  the  plicature  of  the  flank, 
embraces  the  corresponding  crm-al  muscles,  and  establishes  the  Une  of  demarcation 
between  the  trunk  and  the  abdominal  limb. 

The  aponeurosis  of  the  great  oblique  gives  rise,  at  its  posterior  border,  to  two 
very  remarkable  fibrous  layers,  which  appear  to  be  produced  by  the  doubling  of 
this  aponem'osis.  One  of  these  layers  descends  on  the  internal  muscles  of  the 
thigh  to  constitute  the  crural  aponeurosis  (Fig.  176,  4)  ;  while  the  other  is 
reflected  upwards  and  forwards,  to  enter  the  abdominal  cavity.  This  reflected 
layer  of  the  great  oblique  aponeurosis  is  named  the  crural  arch  {ligament  of 
Poupart  or  Fallopius)  (Fig.  165,  b). 

Near  the  prepubic  tendon  of  the  abdominal  muscles,  and  immediately  before 
its  division  into  two  layers,  the  aponeurosis  of  the  external  oblique  is  pierced 
by  a  large  oval  aperture  (the  external  abdominal  ring)  (Fig.  176,  5),  the  mferior 
orifice  of  the  canal  through  which  passes  the  cord  of  the  testicle  in  the  male, 
and  the  mammary  vessels  in  the  female.  This  channel  has  been  named  the 
inguinal  canal. 

The  description  of  the  femoral  aponeurosis,  the  crural  arch,  and  the  inguinal 


302  THE  MUSCLES. 

ring — a  necessary  complement  of  the  great  oblique  muscle — will  be  given  here* 
after. 

Relations  of  the  Great  Oblique  Muscle. — Externally,  to  the  pectoralis  magnus 
and  the  abdominal  tunic,  which  latter  separates  it  from  the  skin  and  the  panni- 
culus.  By  its  deep  face,  it  is  related  to  the  ribs,  into  which  it  is  inserted,  as 
well  as  with  their  cartilages,  the  corresponding  intercostal  muscles,  the  small 
oblique,  and  the  rectus  abdominis.  The  latter  even  appears  to  be  attached, 
through  the  anterior  moiety  of  its  external  border,  to  the  fleshy  portion  of  the 
great  oblique,  by  means  of  a  sHght  layer  of  yellow  elastic  tissue,  which  covers, 
to  a  small  extent,  the  deep  face  of  the  two  muscles. 

Action. — The  external  oblique,  in  contracting,  compresses  the  abdominal 
viscera,  flexes  the  vertebral  spine,  and  acts  as  an  expiratory  muscle.  (By  its 
compression  on  the  abdominal  viscera,  it  concurs  in  the  acts  of  defecation, 
micturation,  and  parturition.) 

Internal  Crural  Aponeurosis. — This  fibrous  layer  descends  from  the 
plicature  of  the  flank  on  to  the  patella  and  the  inner  surface  of  the  leg.  Out- 
wardly, it  is  confounded  with  the  aponeurosis  of  the  fascia  lata  ;  inwardly,  it 
degenerates  into  connective  tissue.  It  covers  the  long  adductor  of  the  leg,  part 
of  the  short  adductor,  the  vastus  internus,  and  the  crural  vessels  at  their  exit 
from  the  abdominal  cavity. 

Crural  Arch. — As  already  mentioned,  this  is  the  reflected  layer  of  the 
great  oblique  aponeurosis,  and  is  also  named  the  ligament  of  FaUopius  and 
Poiqxtrfs  ligament.  It  is  a  wide,  flat  band,  attached  by  its  extremities  to  the 
external  angle  of  the  ilium  and  the  anterior  border  of  the  pubis.  Its  anterior 
face  (Fig.  165,  b)  forms,  inwardly,  the  posterior  wall  of  the  inguinal  canal ;  it 
gives  attachment,  outwardly,  to  the  posterior  fibres  of  the  small  oblique  muscle. 
Its  posterior  face,  applied  against  the  superior  extremity  of  the  patellar  muscles, 
the  long  adductor  of  the  leg,  the  pectineus,  and  the  crural  vessels  on  their 
leaving  the  abdomen,  embraces  all  these  parts  as  in  a  vast  arch,  and  from  this 
peculiarity  it  derives  its  name.  Its  superior  border  is  inserted,  for  its  external 
half,  into  the  lumbo-iliac  aponeurosis.  In  its  middle  part  it  is  much  thinner, 
and  is  prolonged  to  the  external  surface  of  the  long  adductor  muscle  of  the  leg 
and  the  iliac  fascia,  to  be  at  last  mixed  up  with  the  latter.  Within  the  pectineal 
insertion  of  the  small  psoas  muscle,  it  forms  the  anterior  margin  of  the  crural 
ring :  a  triangular  orifice  circumscribed  on  the  other  side  by  the  anterior  border 
of  the  pubis,  the  iliacus,  and  the  long  adductor  of  the  leg,  and  through  which 
pass  the  crural  vessels  as  they  leave  the  abdomen  by  the  crural  arch.^  The 
inferior  border  is  continuous  with  the  femoral  aponeurosis  and  that  of  the  great 
oblique  muscle. 

Inguinal  Canal. — This  is  an  infundibuliform  canal,  compressed  laterally, 
through  which  the  spermatic  cord  and  external  pudic  artery  pass  from  the 
abdomen  in  the  male,  and  the  external  mammary  vessels  in  the  female. 

Situated  on  the  side  of  the  prepubic  region,  in  an  oblique  direction  do^vn- 
wards,  backwards,  and  inwards,  and  measuring  from  two  to  two  and  a  half  inches 
in  length,  this  canal  lies  between  the  crural  arch,  which  constitutes  its  posterior 

'  This  orifice  is  covered  by  a  very  thin  aponeurotic  layer,  which  is  prolonged,  above,  on 
the  crural  vessels,  behind,  into  the  pelvic  cavity,  and  which  appears  to  be  continuous,  inferiorly, 
with  the  upper  border  of  Poupart's  ligament.  This  layer  is  perhaps  only  a  dependency  of  the 
subperitoneal  aponeurosis ;  and  if  so,  it  represents  the  only  vestige  of  the  fascia  transversalis 
It  has  been  possible  to  discover  in  Solipeds. 


MUSCLES  OF  THE  TRUNK.  303 

wall,  and  the  fleshy  portion  of  the  small  obUque  muscle,  which  forms  the  anterior 
wall. 

Its  inferior  (external)  or  cutaneous  orifice,  also  named  the  inguinal  or  external 
abdominal  ring,  is  much  larger  than  the  superior  {^internal).  Pierced  in  the 
aponeurosis  of  the  great  oblique,  in  the  angle  formed  by  the  union  of  the  internal 
border  with  the  posterior  border  of  the  aponeurosis,  this  opening  is  oval  in 
form,  directed  obliquely  backwards  and  inwards,  which  permits  it  to  be  described 
as  having  tivo  lips  or  pillars,  and  two  extremities  or  commissures. 

The  pillars,  distinguished  into  anterior  and  posterior,  are  composed  of  the 
arciform  fibres  from  the  aponeurosis  of  the  great  oblique  muscle. 

The  commissures,  internal  and  external,  result  from  the  union  of  the  two 
pillars  at  their  extremities.  The  internal  is  limited  by  the  prepubic  tendon  of 
the  abdominal  muscles. 

The  superior  (internal)  ov  peritoneal  orifice  of  the  inguinal  canal,  is  situated 
in  front  of,  and  directly  opposite  to,  the  crural  ring.  It  is  a  simple  dilatable  slit, 
comprised,  like  the  canal  itself,  between  the  crural  arch  and  the  small  oblique 
muscle.  Not  well  defined  at  its  extremities,  this  opening  includes  the  neck  of 
the  vaginal  sheath. 

4.  Small  or  Internal  Oblique  Muscle  of  the  Abdomen  (Obliquus 
Abdominis  Internus)  (Figs.  163,  17' ;  176,  6). 

Synonyms. — Ilio-abdominalis — Girard. 

Situation — Composition. — Situated  beneath  the  preceding,  which  exactly  covers 
it,  this  muscle  is,  like  it,  composed  of  a  fleshy  and  aponeurotic  portion. 

Form,  Structure,  Position,  and  Attachments  of  the  muscular  portion. — The 
muscular  portion  is  very  thick,  triangular,  and  flabelliform,  and  occupies  the 
region  of  the  flank.  Its  superior  border  is  united,  by  a  thick,  yellow,  elastic 
production,  to  the  aponeurosis  of  the  latissimus  dorsi,  and  a  peculiar  small 
muscle,  named  by  the  Germans  the  retractor  costce,  {retractor  of  the  last  rib), 
which  we  consider  as  a  dependency  of  the  small  oblique  muscle.  Its  posterior 
border  is  slightly  raised,  and  lies  against  the  crural  arch,  from  which  it  separates, 
inwardly,  to  form  the  inguinal  canal.  Its  anterior  and  inferior  border  is  convex, 
irregular,  and  thinner  than  the  other  portions  of  the  muscle,  and  is  continuous 
with  the  aponeurosis.  All  the  fibres  entering  into  the  composition  of  this 
muscular  portion  are  spread  like  a  fan,  and  leave  the  external  angle  of  the  ilium 
and  the  external  fourth  of  the  crural  arch,  to  be  directed,  the  posterior  fibres 
backwards  and  inwards,  the  middle  fibres  downwards,  and  the  anterior  fibres 
forwards  to  reach  the  antero-inferior  border  of  the  muscle. 

Form,  Structure,  and  Attachments  of  the  Aponeurosis. — The  aponeurosis  is 
irregularly  triangular,  and  formed  of  nacrous-looking  fibres,  which  are  directed 
like  the  muscular  fibres,  and  cross  in  X  fashion  the  aponeurotic  fibres  of  the  external 
oblique.  It  succeeds  the  antero-inferior  border  of  the  muscular  portion,  and  is 
separated,  superiorly,  into  several  digitations  which  reach  the  internal  face  of  the 
last  asternal  cartilages.  Throughout  the  whole  extent  of  its  internal  border  it  is 
fixed  to  the  white  line. 

Relations. — Externally,  with  the  external  oblique.  The  aponeuroses  of  the 
two  muscles,  which  are  merely  superposed  outwardly,  are  blended  inwardly  in 
80  intimate  a  manner,  that  it  might  be  considered  their  respective  fasciculi  were 


301 


THE  MUSCLES. 
Fig.  176. 


M0SCLES   OF   THE    INFERIOR    ABDOMINAL   REGION    (ASS). 

I,  Abdominal  tunic ;  0,  umbilicus.  1,  Panniculus  camosus  detached  from  the  tunica  abdominalii 
and  turned  to  the  left ;  2,  3,  portion  of  the  great  oblique  turned  over  to  the  left ;  4,  femoral 
aponeurosis;  5,  external  abdominal  ring;  6,  muscular  portion  of  the  small  oblique  muscle; 
7,  aponeurosis  of  ditto;  8,  strips  of  the  tunica  abdominalis  and  aponeuroses  of  the  great  and 
small  oblique  muscles  turned  over  to  the  right;  9,  rectus  abdominis;  10,  prepubic  tendon; 
11,  muscular  portion  of  the  transversalis  abdominis;  12,  aponeuroses  of  that  muscle;  13,  left 
pectoi  alls  magnus  ;  14,  section  of  right  ditto  ;  15,  pectoralis  anf icus  and  transversus ;  16,  inferior 
extremity  of  the  mastoido-humeralis ;  17,  muscle  of  the  fascia  lata:  18,  long  adductor  of  the 
leg;  19,  19',  short  adductors  of  the  leg. 


MUSCLES  OF  THE  TRUNK.  305 

woven  into  each  other.  The  small  oblique  covers  the  rectus  and  transversalis 
abdominis. 

Action. — This  muscle,  a  congener  of  the  preceding,  compresses  the  abdominal 
viscera,  depresses  the  last  ribs,  and  causes  the  flexion — either  direct  or  lateral — of 
the  vertebral  column. 

The  retractor  muscle  of  the  last  rib. — This  small  muscle,  flattened  on  each  side 
and  triangular  in  form,  originates  by  aponeurotic  fibres  from  the  summits  of  the 
first  two  or  three  transverse  processes  of  the  lumbar  region.  It  terminates  on 
the  posterior  border  of  the  last  rib.  Covered  by  the  last  digitation  of  the 
posterior  serratus  and  by  the  great  oblique,  it  covers  in  turn  the  transversalis 
abdominis.  In  contracting,  it  draws  the  last  rib  backwards,  and  fixes  it  in  that 
position,  in  order  to  permit  the  expiratory  action  of  the  internal  intercostal 
muscles.  It  therefore  plays  the  same  part,  in  regard  to  these  muscles,  that  the 
scalenus  does  to  the  external  intercostal  muscles  (Fig.  162,  17). 

5.  Geeat  Straight  Muscle  of  the  Abdomen  (Rectus  Abdominis) 
(Figs.  162,  20  ;  176,  9). 

Synonym. — Stemo-pubialia — Girard. 

Situation — Extent — Form — Stricture. — This  is  a  wide  and  powerful  muscular 
band,  extending  from  the  sternum  to  the  pubis,  included  between  the  aponeurosis 
of  the  internal  oblique  and  that  of  the  transversalis  muscles,  narrower  at  its 
extremities  than  in  its  middle,  and  divided  by  numerous  transverse  and  zig-zag 
fibrous  intersections.  These  strongly  adhere  to  the  aponeurosis  of  the  small 
oblique  muscle,  are  nearer  to  each  other,  and  more  distinct,  in  front  than  behind, 
and  are  produced  by  small  tendons  which  are  placed  at  certain  distances  on  the 
course  of  the  muscular  fasciculi,  making  it  somewhat  of  a  polygastric  muscle. 

Attachments. — In  front :  1.  To  the  prolonging  cartilages  of  the  last  four 
sternal  and  the  first  asternal  ribs.  2.  To  the  inferior  face  of  the  sternum. 
Outwardly,  by  the  anterior  moiety  of  its  external  border,  to  the  internal  face  of 
the  great  oblique.  Behind,  to  the  anterior  border  of  the  pubis,  through  the 
medium  of  the  common  tendon,  which  is  a  direct  continuation  of  the  rectus 
abdominis. 

Relations. — By  its  inferior  face,  and  in  front,  with  the  pectoralis  magnus  and 
great  oblique  ;  for  the  remainder  of  its  extent,  with  the  aponeurosis  of  the  small 
oblique.  By  its  superior  face,  with  the  transversalis  muscle  and  the  cartilages  of 
several  ribs.  By  its  internal  border,  with  the  white  hue,  which  separates  it  from 
the  opposite  muscle. 

Action. — It  draws  the  thorax  backwards,  and  compresses  the  abdominal 
viscera.  It  is  also  the  principal  flexor  of  the  spine.  (Leyh,  remarking  that 
it  shares  in  the  functions  of  the  preceding  muscles,  adds  that  it  draws  the  pelvis 
forwards  during  copulation.) 

6.  Transverse  Muscle  of  the  Abdomen  (Transversalis  Abdominis) 
(Figs.  163,  18  ;  176,  12,  12). 

Synonyms. — Lumbo-abdominalis — Girard.    (The  costo-abdoniinalis  internus  of  Leyh.) 

Sittmtion — Composition. — This  muscle  is  situated  immediately  outside  the 
peritoneum,  and  forms  the  deep  layer  of  the  abdominal  parietes.  It  is  musculai 
outwardly,  and  aponeurotic  for  the  remainder  of  its  extent. 


306 


THE  MUSCLES. 


Form,  Structure,  and  Attachments  of  the  muscular  portion. — It  presents  a  band 
elongated  from  before  to  behind,  extending  from  the  sternum  to  the  transverse 
processes  of  the  last  lumbar  vertebrae,  following  in  its  course  the  direction  of  the 
cartilages  of  the  ribs,  and  composed  of  parallel  fibres  passing  from  one  border  to 
the  other. 

Its  superior  border,  concave,  is  attached  :  1.  To  the  internal  sm-face  of  the 
asternal  ribs  by  digitations  placed  opposite  those  of  the  diapliragm,  but  the 

Fig.  177. 


MUSCLES  OF   THE  ANTERIOR   ASPECT  OF   THE  BODY  OF   MAN.      ON  THE    LEFT   SIDE   THE   SUPERFICIAL 
LAYER   IS   SEEN;   ON   THE   RIGHT,   THE    DEEPER   LAYER. 

1,  Pectoralis  major;  2,  deltoid;  3,  anterior  border  of  the  latissimus  doi-si  ;  4,  serratus  magnue ; 
5,  subclavius,  right  side  ;  6,  pectoralis  minor  ;  7,  coraco-brachialis  ;  8,  biceps,  with  its  two  heads ; 
9,  coracoid  process  of  the  scapula;  10,  serratus  magnus,  right  side;  11,  external  intercostal 
muscle  of  the  fifth  intercostal  space;  12,  external  oblique;  13,  its  aponeurosis  with  the  linea 
alba ;  14,  Poupart's  ligament ;  15,  external  abdominal  ring ;  16,  rectus  muscle  of  right  side ; 
17,  pyramidalis  muscle;  18,  internal  oblique;  19,  conjoined  tendon  of  internal  oblique  muscle 
and  Poupart's  ligament. 


majority  of  which  do  not  mix  with  them.  2.  To  the  extremity  of  the  transverse 
processes  of  the  lumbar  region  by  a  thin  fibrous  layer.  Its  inferior  border  is 
convex,  and  continuous  with  the  aponeurosis. 

Form,  Structure,  and  Attachments  of  the  aponeurosis. — This  is  triangular- 
shaped,  with  the  base  behind,  and  with  its  fibres  running  in  a  direction  trans- 
verse to  the  median  line.  Closely  laid  one  against  another  in  front,  these  fibres 
separate  behind,  and  form  only  a  very  thin  and  incomplete  layer. 

By  its  external  border,  the  aponeurosis  is  joined  to  the  inferior  margin  of 


MUSCLES  OF  THE  TRUNK  307 

the  muscular  portion.  Its  internal  border  is  fixed  to  the  xiphoid  cartilage  and 
the  white  line.  Its  posterior  border,  badly  defined,  appears  to  join  the  crural 
arch  only  on  its  outer  aspect. 

Relations. — Outwards,  with  the  inferior  extremity  of  the  asternal  ribs  and 
their  cartilages,  with  the  rectus  abdominis,  the  small  oblique,  and  the  depressor 
muscle  of  the  last  rib  ;  inwardly,  with  the  peritoneum,  from  which  it  is  separated 
by  the  subperitoneal  aponeurosis — an  extremely  fibrous  layer  which,  in  Man  and 
some  animals,  becomes  much  thickened  towards  the  crural  arch,  where  it  forms 
adhesions.     It  has  been  described,  in  human  anatomy,  as  the  fascia  transversalis. 

Action. — It  compresses  the  abdominal  viscera  when  it  contracts,  and  presses 
them  against  the  vertebral  column. 

Differential  Characters  in  the  Muscles  of  the  Abdominal  Kegion  in  the  otheb 

Animals. 

A.  Ruminants. — The  development  of  the  tunica  ahdominalis  is  in  proportion  to  the 
volume  of  the  digestive  viscera.  This  membrane  is,  therefore,  very  wide  and  thick  in  Rumi- 
nants. 

The  obliquus  externus  has  no  femoral  aponeurosis;  its  aponeurosis  is  therefore  entirely 
reflected  in  the  abdominal  cavity.  The  inguinal  canal  is  very  short ;  its  upper  orifice  is  very 
narrow,  and  it  is  situated  near  where  the  two  portions  of  the  long  adductor  of  the  leg  unite 
(Goubaux);  its  inferior  opening  is  very  elongated  from  before  to  behind,  and  without  to 
within. 

The  muscular  portion  of  the  small  oblique  occupies  the  entire  space  comprised  between  the 
posterior  border  of  the  last  rib,  the  extremity  of  the  transverse  processes  of  the  lumbar  vertebrae, 
and  the  external  angle  of  the  ilium.  The  small  retractor  of  the  last  rib  is  not  distinct  from  the 
principal  muscle.  The  rectus  abdominis  is  wide  behind,  with  tendinous  intersections  more 
marked  at  its  superior  than  its  inferior  face ;  the  aponeurosis  of  the  transversalis  is  much 
thicker  and  more  resisting  than  in  Solipeds. 

The  prepubic  tendon  of  the  abdominal  muscles  is  large,  and  attached  to  the  inner  face  of 
the  short  adductors  of  the  leg  by  two  ligamentous  bands ;  this  attachment  depresses  the  lower 
part  of  the  abdominal  wall,  and  therefore  it  is  that,  in  Ruminants,  there  is  a  concave  depression 
in  front  of  the  pubis. 

B.  Pig  and  Camivora. — The  tunica  ahdominalis  is  reduced  to  an  insignificant  layer. 
The  external  oblique  is  remarkable  for  the  enormous  development  of  its  muscular  portion  and 
the  narrowness  of  its  aponeurosis.     The  internal  oblique  resembles  that  of  Ruminants. 

Comparison  of  the  Abdominal  Muscles  of  Man  with  those  of  Animals. 

With  the  exception  of  some  sligbt  diff'erences,  the  abdominal  muscles  of  Man  resemble 
those  of  the  smaller  animals.  The  tunica  ahdominalis  does  not  exist,  but  is  represented  by  a 
layer  of  connective  tissue  which  separates  the  skin  from  the  aponeurosis  of  the  obliquus 
externus.  The  muscular  portion  of  this  muscle  has  no  attachment  to  the  aponeurosis  of  the 
great  dorsal. 

The  aponeurosis  of  the  obliquus  internus  is  divided  into  two  layers  at  the  external  border  of 
the  rectus  muscle;  the  anterior  is  consolidated  with  the  external  oblique,  and  passes  in  front 
of  the  rectus;  the  posterior  is  united  to  the  transversalis,  and  passes  behind  that  muscle. 

The  aponeurosis  of  the  transversalis  is  divitied  into  two  layers,  only  one  of  which  femains 
behind  the  rectus;  this  is  named  the  semilunar  fold  of  Douglas. 

The  rectus  offers  three  transverse  fibrous  intersections  in  its  length  (linem  transversse).  At 
its  upper  extremity,  it  divides  into  three  branches:  the  internal  is  attached  to  the  xiphoid 
appendage  and  the  cartilage  of  the  seventh  rib;  the  middle,  to  that  of  the  sixth  rib;  the 
external,  to  the  cartilage  of  the  fifth  rib. 

"  To  the  rectus  is  annexed  a  small  triangular  muscle,  the  pyramidalis,  which  is  not 
found  in  animals.  This  muscle  is  about  2^  inches  long;  is  sometimes  absent;  most  developed 
in  children ;  is  attached  by  its  base  to  the  pubis,  between  the  spine  and  the  symphysis ;  and 
by  its  summit  is  continuous  with  a  tendon  which  is  lost  in  the  white  line,  and  constitutes, 
with  that  of  the  opposite  siile,  a  fibrous  cnrd  whicii  may  be  followed  to  the  umbilicus"* 
(Beaunis  and  Bouchard). 

Lastly,  at  the  inner  aspect  of  all  the  abdominal  muscles,  beneath  the  peritoneum,  is  a  fibrous 


308  THE  MUSCLES. 

layer— the  fascia  traneversalis.  Thi8  fascia  is  not  distinctly  limited  upwards  or  outwards; 
below,  it  is  fixed  to  the  crural  arch,  in  the  vicinity  of  the  inguinal  canal,  and  sends  a  layer  to 
the  surface  of  the  cord  spermatic. 

Diaphragmatic  Region. 

This  is  composed  of  a  single  muscle,  the  diaphragm. 
Diaphragm. 

Preparation. — Place  the  subject  in  the  first  position;  open  the  abdomen  and  remove  the 
viscera  it  contains,  as  well  as  the  large  vascular  trunks  lying  upon  the  sublumbar  region ; 
detach  the  peritoneum  from  the  fleshy  portion  of  the  muscle,  in  order  to  show  the  digitationa 
of  the  latter  more  distinctly,  taking  care  not  to  allow  the  air  to  enter  the  thoracic  cavity,  as  it 
■would  destroy  the  tense  and  concave  form  of  tlie  diaphragm. 

Situation — Direction. — The  diaphragm  is  a  vast  musculo-aponeurotic  partition, 
separating  the  thoracic  from  the  abdominal  cavity,  between  which  it  is  placed  in 
an  oblique  direction  downwards  and  forwards. 

jTorm. — It  is  flattened  before  and  behind,  eUiptical,  wider  above  than  below, 
concave  posteriorly,  and  convex  anteriorly. 

Structure. — This  muscle  comprises  :  1.  A  central  aponeurotic  portion  desig- 
nated the  phrenic  centre,  which  is  incompletely  divided  into  two  leaflets  by  the 
pillars  or  crura — fleshy  columns  which  descend  from  the  sublumbar  region.  2. 
A  peripheral  or  circumferential  portion,  forming  a  wide  muscular  band  around 
the  phrenic  centre. 

The  phrenic  centre  (also  named  the  speculum  Helmontii^  or  mirror  of  Hehnont) 
is  composed  of  white,  glistening,  radiating  fibres  which,  originating  from  the 
pillars,  extend  in  every  direction  to  join  the  muscular  fibres  of  the  peripheral 
portion.  It  is  pierced,  in  its  right  leaflet,  by  a  large  opening  for  the  posterior 
vena  cava  {foramen  dextrum). 

The  crura  ov  pillars  are  two  in  number — a  right  and  left.  The  right  crus  or 
pillar,  the  most  considerable,  is  a  very  thick,  fleshy  fasciculus  which  commences 
under  the  loins  by  a  strong  tendon,  united  to  the  inferior  common  vertebral 
ligament.  It  descends  to  the  phrenic  centre,  to  which  it  gives  a  heart-shaped 
appearance.  Near  its  inferior  extremity,  it  presents  an  opening  for  the  passage 
of  the  oesophagus  and  pneumogastric  nerves,  in  the  abdominal  cavity  {foramen 
sinistruni).  The  left  pillar  is  a  small  triangular  fasciculus,  partly  separated  from 
the  preceding  by  an  orifice  {hiatus  aorticus)  for  the  transmission  of  the  posterior 
aorta,  vena  azygos,  and  thoracic  duct.  It  also  arises  from  the  sublumbar 
region  by  a  tendon,  which  is  confounded  with  that  of  its  congener. 

The  peripheral  muscular  portion  is  continuous,  by  its  concentric  border,  with 
the  central  aponeurosis.  Its  eccentric  border  is  divided  into  dentations.  Above, 
and  on  the  left  side,  it  nearly  always  joias  the  left  pillar  ;  but  on  the  right  side  it 
stops  at  a  certain  distance  from  the  corresponding  pillar,  so  that  towards  this 
point  the  phrenic  centre  is  not  enveloped  by  the  peripheral  portion,  and  is  in 
contact  with  the  sublumbar  region. 

Attachments. — 1.  To  the  bodies  of  the  lumbar  vertebrae  by  the  tendons  of  its 
two  pillars,  which  tendons  are  confounded  with  the  inferior  common  vertebral 
Ugament.  2.  By  the  external  contour  of  its  muscular  portion,  to  the  superior 
face  of  the  xiphoid  cartilage  ^  and  the  inner  face  of  the  last  twelve  ribs,  near 

'  This  sternal  fasciculus  sometimes  shows  a  depression,  in  which  the  serous  membranes  of 
the  abdomen  and  thorax  come  into  contact.  If  this  fosette  enlarges,  it  is  converted  into  an 
opening  through  which  hernia  of  the  intestine  into  the  cavity  of  the  chest  may  take  place. 


MUSCLES  OF  THE  TRUNK. 


309 


their  inferior  extremities  or  cartilages.  The  digitations  forming  the  last  inser- 
tions do  not  intercross,  in  Solipeds,  with  those  of  the  transversalis  muscle  of  the 
abdomen,  being  separated  by  an  interval  which  is  wider  behind  than  before. 

Relations. — Anteriorly,  it  is  covered  by  the  pleura,  and  responds,  mediately, 
to  the  base  of  the  lung.  The  posterior  aspect,  covered  by  the  peritoneum,  is  in 
contact  with  the  greater  part  of  the  viscera  contained  in  the  abdominal  cavity — 

Fig.  178. 


DIAPHRAGM   OF   THE   HORSE   (POSTERIOR   FACE). 

1,  1',  The  two  portions  of  the  right  crus  or  pillar;  2,  left  crus  or  pillar  ;  3,  tendons  of  the  pillars; 
4,  4',  peripheral  muscular  portion ;  5,  left  leaflet  of  the  aponeurotic  portion  ;  5,  5',  right  leaflet 
of  the  same ;  6,  posterior  vena  cava ;  7,  oesophagus  passing  through  the  opening  in  the  right 
pillar  ;  8,  posterior  aoi-ta  between  the  two  pillars  ;  9,  cartilaginous  circle  of  the  ribs  ;  10,  11, 
section  of  the  psoas  muscle  ;  12,  section  of  a  lumbar  vertebra;  13,  section  of  the  common  mass; 
14,  retractor  muscle  of  the  last  rib  ;  15,  xiphoid  appendage  of  the  sternum. 


the  stomach,  colon,  spleen,  and  liver  ;  the  latter  is  even  attached  to  this  surface 
for  a  portion  of  its  extent. 

On  each  side  of  the  pillars,  the  circumference  of  the  muscle  forms  an  arch 
which  passes  over  the  great  and  small  psoas  muscles. 


310  THE  MUSCLES. 

Action.— The  diaphragm,  in  contracting,  tends  to  become  an  inclined  plane  ; 
its  central  portion  is  carried  backwards,  and  the  antero-posterior  diameter  of  the 
chest  is  increased.  It  is,  therefore,  essentially  an  inspiratory  muscle.  It  may 
also  raise  the  ribs  by  making  the  mass  of  abdominal  viscera  its  fixed  point ; 
it  then  acts  as  a  reflected  muscle,  to  which  these  viscera  serve  as  a  pulley.  (The 
diaphragm  also  aids  the  other  abdominal  muscles  in  expulsive  efforts,  and,  when 
affected  with  iiTegular  spasmodic  contractions,  produces  the  peculiar  phenomenon 
in  Man  and  some  of  the  lower  animals,  known  as  hiccough.) 

Differential  Characters  of  the  Diaphragm  in  the  other  Animals. 

In  the  Ox,  the  pillars  of  the  diaphragm  are  very  lon<:];  and  voluminous.  "  The  attachments 
of  the  muscular  portion  are  much  farther  distant  from  the  cartilaginous  circle  than  in  the 
Horse,  particularly  at  the  superior  part ;  this  disposition  explains  the  innocuousness  of  puncture 
of  the  paunch  in  the  middle  of  the  last  intercostal  space ;  for  in  the  Horse,  when  the  instru- 
ment is  passed  through  this  part,  it  penetrates  the  thorax  "  (communicated  to  M.  Lecoq  by 
M.  Tahourin). 

In  the  Sheep,  we  have  not  remarked  that  the  costal  attachments  were  more  forward  than 
in  the  Horse. 

Rigot  erroneously  states  that,  in  the  Pig  and  Dog,  the  oesophagus  passes  between  the  two 
pillars  of  the  diaphragm ;  on  several  occasions  we  have  convinced  ourselves  that  this  tube 
traverses  the  right  pillar,  as  in  tiie  other  animals. 

Comparison  of  the  Diaphragm  of  Man  with  that  of  Animals. 

In  the  human  diaphragm,  the  aponeurotic  portion  is  divided  into  three  leaflets,  which  has 
caused  it  to  be  termed  the  aponeurotic  trefoil.  Between  the  middle  and  right  leaflet  is  the 
orifice  through  which  the  inferior  vena  cava  passes.  The  openings  for  the  passage  of  the 
oesophagus  and  the  aorta  are  situated  between  the  two  pillars.  There  are  frequently  met  with, 
in  Man,  one  or  two  small  accessory  pillars,  separated  from  the  large  pillars  by  an  aperture  that 
afibrds  a  passage,  on  the  right  side,  to  the  vena  azygos  and  the  sympathetic  nerve,  and  on  the 
left  side,  to  one  of  the  lumbar  veins  and  the  other  sympathetic  nerve. 

The  peripheric  muscular  portion  always  joins,  posteriorly,  the  central  muscular  portion. 

Article  II. — Muscles  of  the  Anterior  Limbs. 

These  are  divided  into  four  principal  groups  :  the  muscles  of  the  shoulder, 
arm,  forearm,  and  foot. 

Muscles  of  the  Shoulder. 

These  muscles  are  grouped  around  the  scapula,  and  all  act  upon  the  arm, 
which  they  extend,  flex,  abduct,  adduct,  etc.  They  form  two  regions  :  an 
external  or  supra-scapular^  and  an  internal  or  subscapular . 

A.  External  Scapular  Region. 

This  comprises  four  muscles  :  the  long  abductor  of  the  arm  {teres  externus), 
the  short  abductor  (postea  spinatus  minor,  or  teres  mitior),  the  supra-spinatus,  and 
infraspinatus.  These  muscles  are  applied  to  the  external  surface  of  the  scapula, 
aud  are  covered  by  an  aponeurotic  layer. 

Preparation  of  the  external  scapular  region. — Separate  the  limb  from  the  trunk ;  remove  the 
trapezius  and  mastoido-humeralis,  to  expose  the  external  surface  of  the  aponeurosis;  take 
away,  also,  the  small  pectoral  muscle,  after  studying  its  mode  of  insertion  into  this  fascia. 

This  being  accomplished,  next  remove  the  latter  muscle  to  show  the  supra-spinatus,  the 
infra-spinatus,  and  long  abductor  muscle  of  the  arm  ;  leaving  only  the  strip  which  attaches  the 
anterior  portion  of  the  latter  to  the  tuberosity  of  the  scapular  spine. 

To  study  the  short  abductor  muscle,  it  is  only  necessary  to  cut  the  long  abductor  and  supr» 


MUSCLES  OF  THE  ANTERIOR  LIMBS. 


311 


spinatus  across,  and  to  throw  back  the  sections :  an  operation  requiring  some  care,  because  of 
the  intimate  adherence  of  the  short  abductor  to  the  infra-spinatus. 


1.  External  Scapular  Aponeurosis. 

This  aponeurosis,  to  which  the  pectoralis 
parvus  and  long  adductor  of  the  arm  act  as  tensors, 
gives  origin,  by  its  internal  face,  to  several  septa 
which  penetrate  between  the  scapular  muscles, 
and  form  around  them  more  or  less  complete 
contentive  sheaths.  Its  external  face  is  separated 
from  the  skin  by  the  panniculus  carnosus,  trape- 
zius, mastoido-humeralis,  and  the  aponeurotic 
fascia  which  unites  the  last  two  muscles.  It  is 
continuous,  in  front,  with  the  thin  fibrous  ex- 
pansion extended  over  the  internal  scapular 
muscles  ;  behind  and  downwards,  it  is  prolonged 
over  the  muscles  of  the  arm  and  insensibly  de- 
generates into  connective  tissues  ;  above,  it  is 
attached  to  the  fibro-cartilaginous  prolongation 
of  the  scapula. 

2.  Long  Abductor  of  the  Arm  (Teres  Ex- 
TERNus),  OR  Scapular  Portion  of  the 
Deltoid  (Fig.  179,  1,  1). 

Synonyms.  —  Scapiilo-humeralis  magnus  —  Girard. 
(Teres  major — Percivall.  Great  scapulotrochiterius — Leyh.) 

Situation — Composition — Form  — Direction . — 
This  muscle  is  situated  beneath  the  scapular 
aponeurosis,  behind  the  infra-spinatus,  and  is 
composed  of  two  portions  placed  one  above  the 
other,  separated  by  a  superficial  interspace.  The 
posterior  portion,  the  most  considerable,  is  elon- 
gated from  above  to  below,  bulging  in  its  middle, 
narrow  at  its  extremities,  plane  on  its  external 
and  convex  on  its  internal  surface.  It  accompanies 
the  posterior  border  of  the  infra-spinatus,  and  is 
lodged  in  a  depression  in  the  large  extensor  muscle 
of  the  forearm. 

The  anterior  portion,  much  shorter  than  the 
preceding,  extends  over  the  infra-spinatus  and 
short  abductor,  by  sUghtly  crossing  the  direction 


Fig.  179. 


EXTERNAL   MUSCLES   OF   THE 
RIGHT    ANTERIOR    LIMB. 


1,  1,  Long  abductor  of  the  arm;  1', 
its  humeral  insertion;  2,  supra- 
spinatus  ;  3.  infra-spinatus  ;  3',  its  tendon  of  insertion  ;  4,  short  abductor  of  the  arm ;  5,  biceps ; 
6,  anterior  brachialis ;  7,  large  extensor  of  the  forearm  ;  8,  short  extensor  of  the  forearm ;  9, 
anconeus;  11,  anterior  extensor  of  the  metacarpus;  11',  its  tendon;  12,  aponeurosis  separating 
that  muscle  from  the  anterior  brachialis;  13,  oblique  extensor  of  the  metacarpus;  14,  anterior 
extensor  of  the  phalanges ;  14',  its  principal  tendon;  15,  the  small  tendinous  branch  it  furnishes 
to  the  lateral  extensor ;  16,  lateral  extensor  of  the  phalanges ;  16',  its  tendon  ;  17,  the  fibrous 
band  it  receives  from  the  carpus;  18,  external  flexor  of  the  metacarpus;  19,  .its  metacarpal 
tendon;  20,  its  supra-carpal  tendon;  ulnar  portion  of  the  perforans  ;  22,  tendon  of  the  perforans, 
23,  its  carpal  ligament ;  24,  its  reinforcing  phalangeal  sheath  ;   25,  tendon  of  the  perforatus. 


312  TEE  MUSCLES. 

of  these  two  muscles.  Thick  inferiorly,  this  portion  diminishes  considerably 
towards  its  superior  extremity. 

Structure  and  Attachments. — The  first  portion  is  generally  paler  than  the 
second,  and  is  composed  of  longitudinal  fleshy  fibres  deeply  intersected  by  tendi- 
nous strips.  It  takes  its  origin,  by  its  superior  extremity,  from  the  dorsal  angle 
of  the  scapula.  The  anterior  portion  is  deeper-coloured  and  more  tendinous 
than  the  other.  Its  superior  extremity,  included  within  two  fibrous  folds 
resulting  from  the  duplicature  of  the  scapular  aponeurosis,  is  fixed,  through  the 
medium  of  these,  to  the  tuberosity  of  the  scapular  spine. 

These  two  muscular  bodies  unite  inferiorly,  and  terminate  together  on  the 
deltoid  imprint  or  crest  by  tendinous  and  muscular  fasciculi. 

Relations. — Outwardly,  to  the  scapular  aponeurosis,  with  which  it  may  be  said 
to  form  one  body  ;  inwardly,  to  the  infra-spinatus,  the  short  abductor  of  the 
arm,  and  the  large  and  short  extensors  of  the  forearm. 

Action. — It  gives  a  very  marked  abduction  movement  to  the  humerus,  and 
also  makes  it  pivot  outwards.  It  acts,  besides,  as  a  flexor  of  that  bone,  when  its 
action  is  combined  with  that  of  the  adductor  of  the  arm.  It  should  also  be  con- 
sidered as  a  powerful  tensor  of  the  scapular  aponeurosis. 

3.  Short  Abductor  of  the  Arm  (Postea  Spinatus  Minor),  or  Teres 
Minor  (Fig.  128,  2,  3). 

Synonyms. — Scapulo-humeralis  minor — Girard.  (Scapulo'trochiterim,  medimi  and  parvum 
^Leyh.) 

Volume — Situation — Direction. — A  small  elongated  muscle,  situated  below  the 
preceding  and  the  subspinatus,  along  the  posterior  border  of  the  scapula,  the 
direction  of  which  it  follows. 

Form — Structure. — In  its  inferior  half  it  is  prismatic,  muscular,  divided  by 
fibrous  intersections,  and  easily  separated  into  several  irregular  fasciculi.  In  its 
superior  half  it  is  flattened,  entirely  tendinous,  and  split  into  several  digitations, 
the  longest  of  which  are  behind. 

Attachments. — It  originates  :  1.  Through  the  medium  of  its  tendinous  digita- 
tions, from  the  posterior  border  of  the  scapula  and  the  linear  imprints  in  the 
infra-spinous  fossa.  2.  From  the  small  tubercle  situated  on  the  external  side 
of  the  margin  of  the  glenoid  cavity,  by  a  short  tendon.  It  tenninates  on  the 
humerus,  between  the  crest  of  the  external  tubercle  and  the  deltoid  imprint. 

Relations. — Outwardly,  with  the  infra-spinatus  and  the  long  abductor ; 
inwardly,  with  the  large  extensor  of  the  forearm,  the  short  extensor,  and  the 
capsule  of  the  scapulo-humeral  articulation. 

Action. — Like  the  preceding,  this  muscle  is  an  abductor  and  outward  rotator 
of  the  humerus. 

4.  Supra-spinatus  (AfJTEA-SPiNATUS)  (Figs.  179,  2  ;  181,  5). 

iSi/Tioni/mg.—Supra-acromio-trocliiterius— Girard.  (^Antea  spinatus — Percivall.  Anterior 
spinatus — Leyh.) 

Form — Situation. — This  muscle  is  thick  and  prismatic,  stronger  below  than 
above,  representing  a  very  elongated  pyi-amid,  and  completely  filling,  and  even 
projecting  beyond,  the  supra-scapular  fossa. 

Structure — Attachments. — It  is  almost  entirely  formed  of  fleshy  fibres,  which 
are  attached,  by  their  superior  extremities,  to  the  cartilage  of  prolongation  of  the 


MUSCLES  OF  THE  ANTERIOR  LIMBS.  313 

scapula,  the  inner  face  of  the  scapular  aponeurosis,  the  supra-scapular  fossa,  and 
the  anterior  border  and  cervical  angle  of  the  scaT^nlsi— fixed  insertion.  These 
fibres,  on  reaching  the  inferior  extremity  of  the  muscle,  form  two  very  thick, 
short,  and  slightly  tendinous  branches,  united  to  each  other  by  the  enveloping 
flexor  brachii  or  biceps  aponeurosis.  The  external  branch  reaches  the  summit  of 
the  external  trochanter  of  the  humerus ;  the  internal  is  inserted  into  the  corre- 
sponding part  of  the  internal  trochanter — movable  insertion. 

Relations. — Outwards,  with  the  scapular  aponeurosis,  to  which  its  fibres  adhere 
in  the  most  intimate  manner ;  inwards,  with  the  scapula  and  the  subscapularis 
muscle  ;  forwards,  with  the  small  pectoral ;  and  behind,  with  the  scapular  spine 
and  the  infra-spinatus.  The  two  terminal  branches  cover  and  embrace  the  flexor 
brachii  tendon,  and  the  capsule  of  the  scapulo-humeral  articulation. 

Action. — This  muscle  is  an  extensor  of  the  humerus,  and  a  tensor  of  the 
envelopuig  flexor  brachii  aponeurosis.  With  regard  to  the  articulation  of  the 
shoulder,  it  plays  the  part  of  a  powerful  ligament — a  function  it  shares  with 
the  majority  of  the  other  scapular  muscles. 

5.  Infra-spinatus  (Postea-spinatus)  (Fig.  179,  3,  3'). 

Synonym. — Subacromio-trochiterius — Girard. 

Situation — Form. — Situated,  as  its  name  indicates,  in  the  infra-spinatus  fossa, 
this  muscle  is  wide,  thin,  and  flattened  on  both  sides  at  its  superior  extremity, 
thick  and  prismatic  in  its  middle,  and  conoid  at  its  inferior  extremity,  which  is 
terminated  by  two  short  branches — an  external  and  internal. 

Structure. — The  muscular  fibres  are  directed,  like  the  muscle  itself,  forward 
and  downward ;  they  are  deeply  mixed  with  strong  aponeurotic  layers.  Of  the 
two  branches  in  which  it  terminates  inferiorly,  the  external  is  the  strongest,  and 
is  entirely  constituted  by  a  powerful  tendon  ;  the  internal  is  both  muscular  and 
aponeurotic. 

Attachments. — All  the  fleshy  fasciculi  of  this  muscle  are  fixed,  either  dii'ectly, 
or  through  the  medium  of  the  internal  aponeurotic  layers :  1.  To  the  whole 
extent  of  the  infra-spinatus  fossa.  2.  To  the  scapular  spine  and  its  tuberosity. 
3.  To  the  cartilage  of  prolongation  of  the  scapula.  4.  To  the  internal  face  of 
the  scapular  aponeurosis— ^a;^^  insertion.  The  movable  insertion  of  the  muscle 
takes  place,  on  the  external  tuberosity,  by  its  two  terminal  branches,  the  internal 
passing  within  the  convexity  ;  and  the  strong  tendon  constituting  the  external 
branch  (Fig.  179,  3')  gliding,  by  means  of  a  synovial  bursa,  over  the  surface  of 
this  convexity,  and  attaching  itself  to  the  roughened  facet  which  forms  the  crest 
of  the  external  tuberosity. 

Relations. — It  is  covered  by  the  anterior  portion  of  the  long  abductor  of  the 
arm,  and  by  the  scapular  aponeurosis.  It  covers  the  scapula,  its  cartilage,  the 
fixed  insertion  of  the  large  extensor  of  the  forearm,  and  the  short  abductor,  which 
adheres  to  it  in  the  most  intimate  manner  at  its  superior  or  aponeurotic  portion. 
Its  anterior  border  responds  to  the  scapular  spine  and  supra-spinatus  muscle  ;  the 
posterior  is  bordered  by  the  long  abductor  of  the  arm.  Its  inferior  extremity 
protects,  outwardly,  the  capsule  of  the  scapulo-humeral  articulation,  and  is  con- 
cealed beneath  the  mastoido-humeralis. 

Action. — The  infra-spinatus  acts  on  the  humerus  as  an  abductor  and  outward 
rotator. 


314  TEE  MUSCLES. 


B.  Internal  Scapular  REaiON. 

This  is  composed  of  four  muscles  :  thi*ee  principal — the  subscapularis,  adductor 
of  the  arm  {teres  internus),  and  the  flexor  hrachii — are  situated  on  the  internal 
face  of  the  scapula,  and  are  covered  by  a  very  small  fibrous  fascia  which  is  formed 
of  some  scattered  parallel  fibres  that  run  in  a  transverse  direction.  The  fourth, 
named  the  small  scapulo-humeraUs,  is  a  very  slender  fasciculus  deeply  lodged 
behind  the  articulation  of  the  shoulder. 

Preparation. — Turn  over  the  limb  which  has  served  for  the  dissection  of  the  preceding 
region,  and  remove  the  slight  internal  scapular  fascia.  Be  careful  to  preserve  the  termina- 
tion of  the  latissimus  dorsi  muscle,  in  order  that  its  relations  and  adhesions  with  the  adductor  of 
the  arm  may  be  studied ;  leave  also  the  humeral  insertion  of  the  pectoralis  magnus,  so  that  its 
union  with  the  tendon  of  the  coraco-humeralis  may  be  noted  ;  in  a  word,  prepare  the  region  ae 
it  is  represented  in  Fig.  181.  With  regard  to  the  small  scapulo-humeral  muscle,  it  ought  to 
be  dissected  at  the  same  time  as  the  short  flexor  of  the  forearm. 


1.  Subscapularis  (Fig.  181,  3). 

Synonym. — Subscapulo-  trochineus — Girard. 

Situation — Direction — Form. — This  muscle,  lodged  in  the  subscapular  fossa, 
the  name  of  which  it  bears,  has  the  same  oblique  direction  as  the  scapula.  It  is 
wider  above  than  below,  and  divides  superiorly  into  three  portions  ;  so  that  its 
form  exactly  repeats  that  of  the  excavated  surface  it  covers. 

Structure. — The  muscular  fibres  of  the  subscapularis  slightly  converge  towardsi 
its  inferior  extremity,  and  all  end  in  a  very  strong,  wide,  and  short  tendon. 
They  are  intermixed  with  deep  and  superficial  tendinous  fibres,  which  singularly 
increase  the  tenacity  of  the  muscle ;  the  superficial  fibres  are  spread  over  the 
internal  surface  in  glistening,  nacrous  layers. 

Attachments. — The  subscapularis  has  its  origin  from  the  whole  extent  of  the 
fossa  of  that  name.  Its  movable  insertion  takes  place  on  the  internal  tuberosity 
of  the  humerus,  by  means  of  a  voluminous  tendon  it  offers  at  its  inferior  ex- 
tremity. A  particular  small  synovial  bursa  facilitates  the  gliding  of  this  tendon 
over  the  eminence  into  which  it  is  inserted. 

Relations. — Externally,  with  the  scapula.  Its  internal  face  is  applied  against 
the  serratus  magnus,  from  which  it  is  separated  by  a  thick  layer  of  connective  tissue, 
as  well  as  by  the  rudimentary  fascia  covering  the  three  muscles  of  the  internal 
scapular  region  in  common.  Its  anterior  border,  margined  by  the  supra-spinatus, 
adheres  closely  to  that  muscle  in  its  upper  two-thirds,  and  forms  with  it,  by  its 
inferior  third,  the  intermuscular  space  that  lodges  the  subscapular  vessels  and 
nerves.  Its  posterior  border  responds  to  the  adductor  of  the  arm,  with  which  it 
also  unites  for  the  greater  part  of  its  extent ;  it  is  isolated  from  this  muscle,  in  its 
inferior  third,  by  the  interspace  lodging  the  subscapular  vessels  and  nerves.  Its 
terminal  tendon  covers  the  capsule  of  the  scapulo-humeral  articulation,  which  it 
powerfully  binds  ;  it  is  in  part  covered  by  the  tendon  of  origin  of  the  coraco- 
humerahs  muscle,  which  ghdes  over  its  surface  as  on  a  pulley,  by  means  of  a 
synovial  bursa. 

Action.— This  muscle  is  principally,  and  perhaps  exclusively,  an  adductor  of 
the  arm.     It  may  be  admitted,  however,  that  it  rotates  the  humerus  inwards. 


MUSCLES   OF  TEE  ANTERIOR  LIMBS.  315 

2.  Adductoe  of  the  arm  (Teres  Internus,  or  Teres  Major)  (Fig.  181,  4). 

%riom!/Tn8.— Subscapulo-humeralis—  Girard.     (Great  scapulo-humeralis—Leyh.) 

Form — Situation — Direction. — A  long  muscle,  flattened  on  both  sides,  bulging 
in  its  middle,  contracted  at  its  extremities,  thick  at  its  anterior,  and  thin  at  its 
posterior  border.  It  is  situated  behind  the  preceding,  in  the  same  oblique  direc- 
tion, and  is  parallel  with  the  posterior  portion  of  the  long  abductor,  which  it 
appears  to  repeat  in  the  internal  scapular  region. 

Structure. — It  is  almost  entirely  muscular,  showing  only  some  tendinous  fibres 
at  its  external  surface  and  upper  extremity.  Its  inferior  extremity  is  terminated 
by  a  flat  tendon,  which  also  belongs  to  the  latissimus  dorsi,  and  which  has  been 
already  described  (see  p.  260). 

Attachments. — It  arises  from  the  dorsal  angle  of  the  scapula,  and  the  posterior 
border  of  the  subscapular  muscle — origin  ;  it  passes  to  the  internal  tuberosity  of 
the  humerus,  to  be  attached  by  its  inferior  tendon — termination. 

Relations. — Outwards,  with  the  aponeurosis  of  the  latissimus  dorsi  and  that 
of  the  long  extensor  of  the  forearm,  which  isolates  it  from  the  large  extensor 
muscle  ;  inwards,  with  the  sen-atus  magnus,  from  which  it  is  separated  by  the 
fibrous  and  cellular  layers  mentioned  in  the  description  of  the  subscapularis.  Its 
inferior  extremity  covers  the  short  flexor  and  middle  extensor  of  the  forearm  ;  it 
is  covered  by  the  long  branch  of  the  coraco-humeralis,  and  by  the  vessels  and 
nerves  which  send  their  ramifications  to  the  arm,  forearm,  and  foot. 

Action. — This  muscle  adducts  the  arm,  and  causes  it  to  rotate  inwards.  If  it 
contracts  at  the  same  time  as  the  long  abductor,  it  du'ectly  flexes  the  humerus. 

3.  Coraco-humeralis,  Coraco-brachialis,  or  Omo-brachialis 
(Fig.  181,  10). 

Synonym. — Middle  seapulo-humeralis — Leyh. 

Volume — Situation — Direction. — A  small  elongated  muscle,  which  appears  to 
belong  to  the  arm  rather  than  the  shoulder,  as  it  is  situated  at  the  internal  face 
of  the  humerus,  which  it  slightly  crosses.  If  it  is  described  as  in  the  subscapular 
region,  it  is  because  of  its  attachments  and  action,  which  are,  in  every  respect, 
analogous  to  those  of  the  other  muscles  of  the  shoulder. 

Attachments — Form — Structure. — It  commences  on  the  beak  of  the  coracoid 
process  by  a  small  flat  tendon,  which  is  at  first  included  between  the  supra-spinatus 
and  subscapularis,  but  afterwards  leaves  the  interstice  formed  by  these  two  muscles, 
to  be  inflected  and  glide  over  the  terminal  tendon  of  the  latter.  This  small 
tendon  is  succeeded  by  two  muscular  branches — one  deep,  the  other  superficial. 
The  first  is  a  wide,  thin,  and  short  band,  almost  entirely  muscular,  attached  to 
the  body  of  the  humenis  above  the  internal  tuberosity.  The  second  forms  a  fleshy 
body  of  a  certain  thickness,  flattened  on  both  sides,  and  strongly  aponeurotic ; 
the  fasciculi  composing  it  are  longer  as  they  are  more  posterior,  and  are  inserted, 
by  their  inferior  extremities,  into  the  imprints  on  the  anterior  face  of  the 
humenis. 

Relations. — This  muscle  is  covered  by  the  flexor  brachii,  and  by  the  pectoralis 
magnus,  which  is  partly  attached  to  its  tendon.  It  covers  the  internal  insertion 
of  the  subscapularis,  the  humerus,  the  common  tendon  of  the  latissimus  dorsi, 
the  adductor  of  the  arm,  and  a  small  portion  of  the  short  flexor  and  middle 
extensor  of  the  forearm.     Its  posterior  border  is  margined  by  the  vessels  and 


316  THE  MUSCLES. 

nerves  on  the  inner  aspect  of  the  arm.     The  anterior  humeral  nerve  passes 
between  its  two  branches,  along  with  an  arterial  and  venous  ramification. 

Action. — It  is  an  adductor  of  the  arm,  and  makes  it  also  pivot  inwards.  Its 
direction  and  attachments  do  not  permit  it  to  produce  rotation  outwards,  though 
it  has  been  stated  to  do  so  by  several  authors. 

4.  Small  Scapulo-humeralis  (Scapulo-humeralis  Gracilis,  vScapulo- 
humeralis  posticus). 

(Synonyms. — Not  mentioned  by  Percivall.  Leyh,  in  addition  to  the  above  designation, 
names  it  the  tensor  of  the  capsular  ligament.) 

The  scapulo-humeralis  gi-acilis  is  a  very  small  cylindrical  fasciculus,  compiised 
between  the  large  extensor  of  the  forearm  and  the  capsule  of  the  scapulo-humeral 
articulation  ;  it  derives  its  origin  above  the  margin  of  the  glenoid  cavity  of  the 
scapula,  and  tenninates  below  the  head  of  the  humerus  by  a  thin  tendon,  which 
insinuates  itself  between  the  fibres  of  the  short  flexor  of  the  forearm.  This 
muscle  appears  to  be  peculiar  to  Solipeds,  and  has  been  regarded  by  Rigot  as 
intended  to  raise  the  capsule  of  the  scapulo-humeral  articulation  during  flexion, 
so  as  to  prevent  its  being  pinched  between  the  articular  surfaces. 

Differential  Charactebs  in  the  Muscles  of  the  Shoulder  in  the  other  Animals. 

The  Carnivora  are  the  only  animals  which  oflPer  somewhat  notable  differences  in  the 
muscles  of  the  shoulder. 

Thus,  the  long  abductor  of  the  arm,  very  developed,  has  an  anterior  portion  arising  directly 
from  the  acromion  process,  and  a  posterior  portion  which  springs  from  the  whole  extent  of  the 
scapular  spine,  by  a  short  aponeurosis.  The  supra- spinatus  is  considerable,  and  terminates  in 
a  single  branch  that  goes  to  the  great  trochanter. 

The  infra- spinatus  is  not  so  large  as  the  preceding,  and  is  also  undivided  at  its  inferior 
extremity :  it  is  the  inferior  branch  which  is  absent. 

The  coraco-humeralis  is  very  short,  and  is  composed  of  a  single  fasciculus,  which  terminates 
above  the  humeral  insertion  of  the  adductor  of  tlie  arm. 

In  the  Pig,  the  disposition  of  this  muscle  is  the  same ;  it  is  very  tendinous. 

In  the  Camel,  on  the  external  surface  of  the  scapular  region  is  an  elastic  layer  which 
extends  over  all  the  limb,  and  is  worthy  of  notice.  It  arises  from  the  borders  of  the  cervical 
ligament,  covers  the  shoulder  and  arm,  and  is  thickest  behind  the  scapulo-humeral  angle, 
where  the  abductors  and  extensors  of  the  forearm  separate.  It  descends  on  the  forearm  in 
front  of  the  humero-radial  articulation,  and  reaches  the  lower  third  of  the  anterior  face  of  that 
region,  where  it  divides  into  two  portions.  The  narrower  and  thinner  of  these  go  to  the  front 
of  the  knee,  where  it  gradually  disappears  in  becoming  thinner  and  lighter-coloured;  the 
largest  division  passes  behind,  and  joins  an  equally  elastic  layer  which  comes  from  the  inner 
surface  of  the  olecranian  muscles  and  the  elbow ;  it  reaches  behind  the  knee,  where  it  divides 
into  several  strips,  some  of  which  are  fixed  into  the  inner  border  of  the  carpus  and  metacarpus, 
and  others  on  the  flexor  tendons  of  the  phalanges,  behind  the  metacarpo-phalangeal  articulations. 

This  very  remarkable  elastic  apparatus  tends  incessantly  to  flex  the  bone  of  the  anterior 
limb;  and  to  its  presence  must  certainly  be  attributed  the  characteristic  locomotion  of  the 
Camel — ^jerking  and  almost  passive  flexion  of  the  metacarpus  on  the  forearm,  and  the  forearm 
on  the  arm. 

In  the  Camel,  it  is  also  remarked  that  the  long  abductor  of  the  arm  is  entirely  muscular,  and, 
superiorly,  is  only  attaclied  to  the  acromion  spine. 

Comparison  of  the  Muscles  of  the  Shoulder  op  Man  with  those  of  Animals. 

As  muscles  of  the  shoulder,  there  are  only  described  the  deltoid,  infraspinatus,  teres  minor 
and  major,  and  the  subscapularis ;  the  coraco-brachialis  being  included  in  the  region  of  the 
arm,  while  the  small  scapulo-humeralis  is  absent  (see  Fig.  180). 

The  deltoid,  represented  in  part  by  the  long  abductor  of  the  arm  of  Solipeds,  is  a  large, 
triangular,  flat  muscle,  that  covers  the  articulation  of  the  shoulder.  Its  fibres  are  inserted 
into  the  external  third  of  the  anterior  border  of  the  clavicle,  the  external  border  of  the  aero- 


MUSCLES  OF  THE  ANTERIOR  LIMBS. 


317 


mion,  and  the  inferior  border  of  the  scapular  spine  for  the  whole  of  its  width ;  below,  it  i» 
attached,  through  the  medium  of  a  tendon,  to  the  deltoid  imprint. 

By  their  disposition,  the  supra-spinatus,  infraspinatus,  and  subscapularis  resemble  the 
muscles  of  Carnivora.  The  teres  major,  after  establishing  relations  with  the  latissimus  dorsi, 
as  in  Solipeds,  is  fixed  into  the  inner  lip  of  the  bicipital  groove. 

Muscles  of  the  Arm. 

These  muscles,  grouped  around  the  humenis,  are  attached  to  the  forearm  by 
their  inferior  extremities.     Those  situated  in  front  flex  this  portion  of  the  limb, 
while  those  behind  extend  it.     The  first  form  the 
anterior  brachial  region;   the  second,  the  posterior  I'lg.  180. 

brachial  region. 

A,  Anterior  Brachial  Region. 

This  region  is  composed  of  only  two  muscles — the 
lo7ig  and  short  flexors  of  the  forearm. 

1.  Long  Flexor  of  the  Forearm  (Flexor 
Brachii,or  Brachial  Biceps)  (Figs.  128, 159, 181). 

Synonyms. — Coraco-cubitalis,  or  coraco-radialis,  according 
to  Girard.     (Scapula-  or  coraco-radialis — Leyh.) 

Preparation. — Place  the  limb  on  its  internal  face,  throw 
back  the  brachial  insertion  of  the  mastoido-humeralis,  pectora- 
lis  auticus,  and  pectoralis  transversus,  over  the  external  muscles 
of  the  forearm  ;  excise,  lengthways,  the  inferior  extremity  of 
the  supra-spinatus,  to  show  the  originating  tendon  of  the  muscle. 
The  inferior  insertion  may  be  studied  with  that  of  the  short 
flexor  muscle. 

Form — Situation — Direction — Structure. — A  long, 
cylindrical  muscle,  thick  m  its  middle  portion,  bifid 
inferiorly,  situated  in  front  of  the  humerus,  in  an 
oblique  direction  downwards  and  backwards,  tendinous 
at  its  two  extremities,  divided  by  a  great  number  of 
strong  fibrous  intersections,  one  of  which,  nearly 
central  and  much  more  considerable  than  the  others, 
is  a  veiy  resisting  cord  that  traverses  the  muscle 
throughout  its  length,  and  becomes  continuous  with 
the  tendons  at  its  extremities. 

Attachments. — This  muscle  has  its  origin  at  the 
base  of  the  coracoid  process  by  a  superior,  round,  and 
thick  tendon  (Fig.  128,  6)  that  reaches  the  bicipital 
groove,  on  which  it  is  moulded  in  becoming  fibro-cartilaginous,  and  over  which 
it  glides  by  means  of  a  synovial  sac,  to  be  inflected  backwards  and  confounded 
with  the  body  of  the  muscle.  Its  inferior  tendon,  extremely  short  and  strong, 
terminates  on  the  superior  and  internal  tuberosity  of  the  radius — the  bicipital 
tuberosity — in  becoming  united  to  the  capsular  ligament  of  the  elbow-joint,  and 
insinuating  itself  beneath  the  internal  ligament  of  this  articulation.  At  its 
origin,  this  tendon  gives  off  a  somewhat  resisting  fibrous  band,  which  is  spread 
over  the  surface  of  the  anterior  extensor  of  the  metacarpus,  and  is  confounded 
with  the  antibrachial  aponeurosis. 

Relations. — It  covers  an  adipose  cushion,  which  separates  it  from  the  capsule 
23 


MUSCLES   OF    ANTERIOR   ASPECT 

OF  man's  upper  arm. 

1,  Coracoid  process  of  scapula ; 
2,  coraco-clavicular  liga- 
ment (trapezoid),  passing  up- 
ward to  clavicle  ;  3,  coraco- 
acromial  ligament,  passing 
to  acromion ;  4,  subscapu- 
laris ;  5,  teres  major ;  6, 
coraco-brachialis ;  7,  biceps  ; 
8,  upper  end  of  radius ;  9, 
brachiaiis  anticus ;  10,  in- 
ternal head  of  triceps. 


f 


318 


TEE  MUSCLES. 


of  the  scapulo-humeral  articulation,  the  anterior  face  of  the  humerus,  the  coraco- 

humeralis,  and  the  articulation 


Fig.  181, 


INTERNAL   ASPECT   OF   LEFT   ANTERIOR   LIMB. 

1,  Prolonging  cartilage  of  scapula;  2,  inner  surface  of 
scapula ;  3,  subscapulavis ;  4,  adductor  of  the  arm,  or 
teres  internus ;  5,  supra-  or  antea-spinatus ;  6,  long 
extensor  of  the  forearm,  or  portion  of  the  caput  magnum  ; 
7,  large  extensor  of  the  forearm,  the  other  portion  of  the 
caput  magnum  ;  8,  middle  extensor,  or  caput  medium ; 

9,  humeralis   obliquus,  or   short  flexor   of  the  forearm  ; 

10,  coraco-humeralis  ;  11,  upper  extremity  of  humerus; 
12,  coraco-radialis,  or  flexor  brachii ;  13,  lower  extremity 
of  humerus ;  14,  brachial  fascia ;  15,  anterior  extensor 
of  the  metacarpus,  or  extensor  metacarpi  magnus;  16, 
belly  and  aponeurotic  termination  of  the  flexor  brachii ; 
17,  ulna;  18,  oblique  flexor  of  the  metacarpus;  19, 
internal  flexor  of  the  metacarpus,  or  epicondylo-meta- 
carpus;  20,  radius;  21,  tendon  of  the  oblique  extensor; 
22,  large  metacarpal  bone;  23,  flexor  tendons  of  the 
foot ;  24,  suspensory  ligament ;  25,  internal  rudimentary 
metacarpal  bone;  26,  extensor  tendon  of  the  foot;  27, 
metacarpo-phalangeal  sheath  ;  28,  lateral  cartilages  of 
the  foot ;  29,  podophylla;. 

ligrament  of  the  ulnar  articulation,  and  those  muscles  of 
epicondyle. 


of  the  elbow.     It  is  covered  : 

1.  By  the  supra-spinatus,  be- 
tween the  two  branches  of 
which  it  passes.  2.  By  a 
special  aponeurotic  sheath,  the 
tensor  of  which  is  the  above- 
named  muscle,  with  the  pecto- 
ralis  magnus  (see  Fig,  179, 12, 
in  which  this  aponeurosis  has 
been  partly  preserved).  This 
sheath  separates  the  flexor 
brachii  from  the  mastoido- 
humeralis,  the  pectoralis  trans- 
versus,  and  from  its  congener 
— the  short  flexor. 

Action. — This  muscle  is  a 
flexor  of  the  forearm,  and  a 
tensor  of  the  antibrachial 
aponeurosis.  It  acts,  besides — 
through  the  cord  which  tra- 
verses its  entire  length — as  an 
inextensible  band  that  me- 
chanically opposes  the  flexion 
of  the  scapulo-humeral  angle 
while  the  animal  is  standing, 
and  when  the  forearm  is  main- 
tained fixed  by  the  contrac- 
tion of  the  humero-olecranian 
muscles, 

2.  Short  Flexor  of  the 
Forearm  (Humeralis  Ob- 
liquus, Brachialis  An- 
Ticus,    Humeralis     Ex- 

TERNUS)  (Fig.  128,  12). 

Synonyms.  —  Humero  -  cubitalis 
obliquus,  or  liumero-radialis  — 
Girard.  (Humero-radialis — Leyh.) 
Preparation. — Lay  the  limb  on 
its  internal  face,  and  remove  the 
abductors  of  the  arm,  the  infm-spi- 
natus,  and  the  large  and  shnrt  ex- 
tensors of  the  forearm,  in  urder  to 
expose  the  middle  and  upper  ex- 
tremity of  this  muscle.  Tlien  turn 
the  limb  on  its  external  face  to 
dissect  the  inferior  extremity.  To 
study  it  in  all  its  details,  it  is  a  good 
plan  to  cut  through  the  internal 
the  forearm  which  are  attached  to  the 


MUSCLES   OF  THE  ANTERIOR   LIMBS.  319 

Form — Structure — Situation — Direction. — This  is  a  very  thick  muscle,  almost 
entirely  fleshy,  voluminous  in  its  superior  part,  and  constricted  inferiorly.  It 
is  lodged  in  the  musculo-spiral  groove  of  the  humerus,  the  direction  of  which  it 
exactly  follows  as  it  turns  round  the  bone  to  cover,  successively,  its  posterior 
face,  external  face,  anterior  face,  and  the  capsule  belonging  to  the  elbow 
articulation,  until  it  finally  reaches  the  inner  side  of  the  radius. 

Attachments. — The  muscular  fibres  have  their  fixed  insertion  on  the  posterior 
face  of  the  humerus,  below  the  articular  head.  They  terminate,  inferiorly,  on 
a  flat  tendon,  which  they  almost  entirely  cover.  This  tendon  ghdes  in  a  trans- 
verse groove  situated  on  the  inner  face  of  the  radius,  below  the  bicipital  tube- 
rosity, and  afterwards  passing  under  the  internal  hgament  of  the  elbow- joint, 
it  divides  into  two  very  short  fasciculi ;  one  of  these  goes  to  the  radius,  and  the 
other  to  the  ulna,  where  it  is  mixed  up  with  the  bundles  of  arciform  fibres  which 
unite,  on  the  inner  side,  the  two  bones  of  the  forearm. 

Relations. — We  already  know  the  parts  this  muscle  covers.  It  is  covered, 
inwardly,  by  the  adductor  of  the  arm  and  the  middle  extensor  of  the  forearm  ; 
posteriorly  and  externally,  by  the  large  and  short  extensors  of  that  bone.  Its 
inferior  extremity,  comprised  between  the  anterior  extensor  of  the  metacarpus 
and  the  flexor  brachii,  passes  below  the  antibrachial  band  of  the  latter,  as  under 
a  fibrous  bridge. 

Action. — It  is  simply  a  flexor  of  the  forearm. 

B.  PosTERioE  Brachial  Region. 

This  is  composed  of  four  muscles,  which  have  their  movable  insertion  in 
common  on  the  summit  of  the  olecranon,  and  are  consequently  designated 
olecranian  muscles.  With  reference  to  their  action,  they  are  also  designated 
extensors  of  the  forearm,  and  are  distinguished  into  long,  short,  middle,  and  small.^ 

The  first  three  of  these  muscles  resemble  the  triceps  hrachialis  (or  triceps 
extensor  cuUti)  of  Man — the  large  extensor  representing  the  long  or  middle  portion, 
the  short  extensor  the  external,  and  the  middle  extensor  the  internal.  The  small 
extensor  takes  the  place  of  the  anconeus  or  elbow  muscle  of  some  authorities. 

Preparation.— The  muscles  of  this  region  ought  to  be  studied  before  those  of  the  preceding 
■region.  To  dissect  the  large  and  short  extensors,  it  is  necessary  to  lay  the  limb  on  its  inner 
face,  remove  the  slight  fibrous  layer  wliich  covers  these  two  muscles,  and  raise  the  abductors 
of  the  arm,  which  in  great  part  conceal  their  origin.  The  limb  is  kept  in  the  same  position 
for  the  dissection  of  the  small  extensor,  which  is  not  easily  accomplished,  as  it  is  almost 
entirely  concealed  by  the  short  extensors,  which,  besides,  closely  adhere  to  it.  To  dissect  the 
long  and  middle  extensors,  it  suffices  to  turn  the  limb  on  its  external  surface  and  cut  away  the 
vessels,  nerves,  and  lymphatics  which  partly  cover  the  latter;  care  must  also  be  taken  to 
isolate  the  muscle  annexed  to  the  latissimus  dorsi. 

1.  Large  Extensor  of  the  Forearm  (Caput  Magnum),  or  Long  Portion 
OF  the  Triceps  Brachialis  (Figs.  179,  7  ;  181,  7). 

5?/non«/ms.— Scapulo-olecranius  magnus— G/rarfi.  The  long  portion  of  the  triceps  brachi- 
alis of  Man.     (Portion  of  llie  caput  magnum  of  the  triceps  extensor  brachii— Percivall.) 

Volume— Form— Situation.— An    enormous,   short,  and  triangular  muscle, 

>  In  veterinary  -works,  and  in  preceding  editions  of  this  work,  there  has  been  described  in 
this  region  a  fifth  muscle— the  lonq  extensor  of  the  forearm.  This  has  now  been  moved  to  the 
region  of  the  back  and  loins,  wliere  it  is  annexed  to  the  latissimus  dorsi,  because  of  its  relations 
with  that  muscle. 


320  THE  MUSCLES. 

occupying,  with  the  short  extensor,  the  space  comprised  between  the  posterior 
border  of  the  scapula  and  the  humerus. 

Structure  and  Attachments.— Th.Q  fleshy  mass  constituting  this  muscle  is 
formed  of  very  thick  fasciculi,  among  which  are  found  some  aponeurotic  bauds. 
These  fasciculi  have  their  origin  on  the  dorsal  angle  and  the  axillary  border  of 
the  scapula,  either  directly,  or  through  the  medium  of  two  strong  fibrous  layers, 
between  which  they  are  at  first  included.  They  are  afterwards  directed  back- 
wards and  downwards,  and  converge  towards  a  thick  tendon  which  occupies  the 
posterior  and  inferior  angle  of  the  triangle  represented  by  this  muscle.  The 
tendon  terminates  by  attaching  itself  to  the  summit  of  the  olecranon,  after 
receiving  a  great  number  of  fibres  from  the  short  extensor,  and  after  gliding, 
by  means  of  a  synovial  capsule,  over  the  eminence  which  serves  for  its  insertion. 

Relations. — The  external  surface  is  covered  by  a  thin,  fibrous,  white-and- 
yellow  layer,  which  separates  it  from  the  panniculus ;  it  has  near  the  upper 
border  an  excavation  into  which  is  received  the  posterior  portion  of  the  long 
abductor.  Its  internal  face  responds  to  the  latissimus  dorsi,  the  adductor  of 
the  arm,  and  the  long  extensor.  Its  posterior  border  is  margined  by  the  latter 
muscle  ;  the  superior  follows  the  axillary  border  of  the  scapula,  and  is  attached 
to  it  to  constitute  the  fixed  insertion  of  the  muscle  ;  the  inferior  border  responds 
to  the  short  and  middle  extensors. 

Action. — It  is  an  extensor  of  the  forearm. 

2.  Short  Extensor  of  the  Forearm  (Caput  Medium),  or  External 

Portion  of  the  Triceps  (Fig.  179,  8). 

Synmym. — Humero-olecranius  externus— GiVard. 

Sittmtion — Direction — Form — Strmture. — This  muscle  is  situated  between  the 
humerus  and  the  inferior  border  of  the  preceding  muscle,  and  is  directed 
obliquely  downwards  and  backwards.  It  is  thick  and  short,  flattened  and 
aponeurotic  at  its  upper  extremity,  prismatic,  and  entirely  formed  of  thick 
parallel  muscular  fascicuU  for  the  remainder  of  its  extent. 

Attachments. — One  of  its  attachments  is  on  the  humerus,  to  the  curved  line 
extending  from  the  deltoid  ridge  to  the  base  of  the  articular  head  (see  for  this 
line  Fig.  62,  above  4),  by  the  short  aponeurosis  of  its  superior  extremity-^a^ei 
insertion ;  the  other  is  to  the  olecranon,  either  directly,  or  through  the  tendon 
of  the  large  extensor — movable  insertion. 

Relations. — The  prismatic  shape  of  this  muscle  offers  three  faces,  which 
respond  :  externally,  to  the  two  abductors  of  the  arm  and  to  a  slight  fibrous 
layer  continuous  ;  above,  with  that  which  covers  the  large  extensor  ;  and  below, 
with  the  antibrachial  aponeurosis  ;  internally,  to  the  small  extensor — from  which 
it  is  difficult  to  separate  it — to  the  short  flexor  of  the  forearm,  and  to  the  anterior 
extensor  of  the  metacarpus  ;  superiorly,  to  the  large  extensor,  which  closely 
adheres  to  it. 

Action. — An  extensor  of  the  forearm. 

3.  Middle  Extensor  of  the  Forearm  (Caput  Parvum),  or  Internal 

Portion  of  the  Triceps  (Fig.  181,  8). 

SyTWJij/m?.— Humero-olecranius  intemus — Girard.     (Caput  parvum — PercivaU.) 

Situation — Direction — Form — Structure. — This  muscle  is  situated  at  the 
internal  face  of  the  humerus,  along  the  inferior  border  of  the  large  extensor = 


MUSCLES  OF  THE  ANTERIOR   LIMBS. 


S21 


^ig.  182. 


It  is  oblique  downwards  and   backwards,  pyriform,  enlarged  at  its   superior 
extremity,  contracted  inferiorly,  where  it  terminates  by  two  small  flat  tendons. 

Attachments. — It  originates,  by  its  superior  extremity,  from  the  inner  aspect 
of  the  humerus,  behind  and  above  the  tuberosity  on  its  body.     One   of   its 
terminal  tendons  is  attached  to  the  summit  of  the 
olecranon  ;  the  other  glides  over  a  small  convexity 
on  the  inner  side  of  that  eminence,  and  goes  to  be 
inserted  a  little  lower  than  the  first. 

Relations. — Above,  with  the  inferior  border  of  the 
large  extensor  ;  outwards,  with  the  humerus,  the 
short  flexor,  and  short  extensor  of  the  forearm  ;  in- 
wards, with  the  humeral  insertion  of  the  latissimus 
dorsi  and  the  abductor  of  the  arm,  the  long  branch 
of  the  flexor  brachii,  the  vessels  and  nerves  on  the 
inner  side  of  the  arm,  and  the  long  extensor  of  the 
forearm. 

Action. — An  extensor  of  the  forearm. 

4.  Small  Extensor  of  the  Fokearm  or 
Anconeus  (Fig.  128,  10). 

Synonym. — Humero-olecranius  minor — Girard. 

Form — Structure — Situation — Relations. — This  is 
a  small,  thick,  and  prismatic  muscle,  almost  entirely 
fleshy,  situated  behind  the  elbow  articulation.  It 
is  applied  against  the  synovial  cul-de-sac  which 
ascends  into  the  olecranian  fossa,  and  to  which  it  is 
strongly  attached  ;  it  is  hidden  by  the  short  extensor, 
from  which  it  is  not  easily  distinguished. 

Attachments. — It  originates  from  the  margin  of 
the  olecranian  fossa,  chiefly  above  and  outwards.  It 
terminates  by  being  inserted  into  the  anterior  and 
external  part  of  the  olecranon. 

Action. — This  little  muscle,  a  congener  of  the 
preceding,  raises  the  articular  capsule  it  covers,  and 
prevents  its  being  pinched  between  the  bony  surfaces. 

Differential  Characters  in  the  Muscles  of  the  Arm 
IN  THE  other  Animals. 

In  all  animals,  the  long  flexor  of  the  forearm,  or  flexor 
brachii,  is  less  thick  and  tendinous  than  in  Solipeds. 

In  the  Pig,  Dog,  and  Cat,  it  comports  itself  in  a 
special  manner  at  its  inferior  extremity ;  it  is  attached  at 
first  to  the  bicipital  tuberosity,  and  also  furnishes  a  small 
tendinous  branch  which  glides  over  the  inner  side   of  the 


deep    muscles    on 
ternal    aspect 

anterior   LIMB. 


THE     EX- 

)f    right 


1,  Scapula;  2,  coracoid  process 
of  scapula  ;  3,  flexor  brachii ; 
4,  superior  extremity  of  humerus ;  5,  external  tuberosity  of  humerus ;  6,  humeralis  obliquus ; 
7,  body  of  humerus ;  8,  biceps ;  9,  anterior,  or  great  extensor  of  the  metacarpus  ;  10,  ulna ; 
11,  extensor  pedis,  or  anterior  extensor  of  the  phalanges;  12,  ulnaris  accessorius,  or  ulnar  portion 
of  the  perforans  ;  13,  lateral  extensor  of  the  metacarpus,  or  extensor  suffraginis  ;  14,  oblique 
extensor  of  the  metacarpus;  15,  flexors  of  the  foot;  16,  trapezium;  17,  annular  ligament;  18, 
carpal  ligament  of  perforans  tendon,  20;  19,  perforatus  tendon;  21,  tendon  of  anterior  extensor  of 
metacarpus;  22,  small  metacarpal  bone;  23,  suspensory  ligament;  24,  lateral  band  of  metacarpo- 
phalangeal sheath ;  25,  perforans  tendon ;  26,  branch  of  the  suspensory  ligament  joining  the 
extensor  pedis,  27. 


822  THE  MUSCLES. 

radius  by  means  of  a  synovial  bursa,  and  is  fixed  within  the  ulna,  towards  the  base  of  the 
olecranon. 

The  flexor  brachii  or  biceps  of  the  Camel,  is  manifestly  decomposable  iuto  two  muscular 
portions,  united  above  in  a  tendon.  The  inner  portion  is  the  largest  and  somewhat  fusiform,  and 
is  attached  directly  to  the  radius  by  its  muscular  fibres.  The  other  portion,  situated  external 
to  and  in  front  of  the  preceding,  ends  in  a  bifurcated  tendon,  one  branch  of  which  goes  to  the 
bicipital  tuberosity :  the  other,  succeeded  by  a  small  fleshy  fasciculis,  joins  the  body  of  the 
anterior  extensor  of  the  metacarpus. 

The  short  flexor  of  the  forearm,  or  humeralis  ohliqum,  is  terminated  in  the  Pig,  Dog,  and 
Cat,  by  a  small  tendon  which  is  fixed  in  the  ulna,  beluw  the  ulnar  branch  of  the  flexor 
brachii. 

The  middle  extensor  of  the  forearm  and  anconeus  of  these  animals  are  remarkable  for  their 
volume. 

Comparison  of  the  Muscles  of  the  Arm  of  Man  with  those  of  Animals. 

In  Man,  three  muscles  are  situated  in  front  of  tlie  humerus — the  biceps,  coraco-humeralis, 
and  the  humeralis  ohliquus  -,  behind  are  found  the  triceps  brachialis,  and  the  anconeus. 

The  biceps,  which  corresponds  to  the  flexor  brachii  of  animals,  commences  on  the  scapula 
by  two  heads,  which  unite  towards  the  upper  part  of  the  humerus.  The  long  portion  is 
detached  from  the  upper  part  of  the  rim  of  the  glenoid  cavity  ;  the  shortest  commences  from 
the  summit  of  the  coracoid  process.  The  inferior  tendon  of  the  biceps  gives  ofi",  before  fixing 
itself  on  the  bicipital  tuberosity,  a  fibrous  layer  which  is  confounded  with  the  antibrachial 
aponeurosis. 

The  coraco-humeralis  has  only  one  fleshy  body. 

As  in  the  Carnivora  and  Pig,  the  humeralis  ohliquus  terminates  on  the  ulna,  below  the 
coronoid  process. 

The  triceps  brachialis  exactly  represents,  by  its  three  heads,  the  large,  middle,  and  short 
extensors  of  the  forearm  of  animals  (see  Fig.  180). 

There  is  nothing  particular  with  regard  to  the  anconeus. 

Muscles  of  the  Forearm. 

These  muscles,  nine  in  number,  distributed  in  two  regions — anterior  and 
posterior — envelop  the  bones  of  the  forearm  on  every  side  except  the  internal, 
where  the  radius  is  in  mediate  contact  with  the  skin.  They  all  terminate  on 
the  different  sections  of  the  hand  or  anterior  foot,  which  they  flex  or  extend, 
and  are  contained  in  a  common  fibrous  sheath,  which  constitutes  the  antibrachial 
aponeurosis. 

Antibrachial  Aponeurosis. 

This  retaining  fascia  forms  a  very  strong  and  resisting  envelope,  which  is 
firmly  fixed  around  the  antibrachial  muscles  by  the  insertions  it  has  on  the  bones 
of  the  forearm,  being  attached  to  the  olecranon,  the  internal  aspect  of  the 
radius,  and  to  the  inferior  extremity  of  that  bone,  both  inwards  and  outwards. 

Its  external  face  is  covered  by  the  superficial  vessels  and  nerves,  which  are 
separated  from  the  skin  by  a  very  thin  fibrous  layer,  more  particularly  observable 
on  the  inner  side,  where  it  covers  the  antibrachial  aponeurosis  in  a  very  evident 
manner  ;  it  is  rendered  tense  by  the  pectoralis  transversus.  Up  to  the  present 
time,  this  fibrous  layer  has  not  been  distinguished  from  the  aponeurosis  it  covers. 
The  inner  face  of  the  latter  gives  rise  to  several  septa,  which  penetrate  the 
interstices  of  the  muscles  to  form  around  some  of  them  special  retention  sheaths  ; 
it  adheres  to  several  of  them  very  intimately.  At  its  upper  border,  this  aponeu- 
rosis receives,  inwardly,  the  insertion  of  the  annexed  muscle  of  the  latissimus 
dorsi  ;  in  front,  the  accessory  band  of  the  flexor  brachii ;  outwardly,  it  is  con- 
tinuous with  the  fascia  covering  the  external  face  of  the  olecranian  muscles. 
Inferiorly,  it  is  prolonged  around  the  knee  to  form  the  tendinous  sheaths  of  that 


MUSCLES  OF  THE  ANTERIOR  LIMBS.  323 

The  antibrachial  aponeurosis  is  made  tense  by  the  contraction  of  the  annexed 
muscle  of  the  latissimus  dorsi,  and  that  of  the  flexor  brachii.  With  reference  to 
the  pectorahs  transversus,  which  has  hitherto  been  regarded  as  intended  to  play 
the  same  part,  it  can  only  act  on  the  fascia  which  covers,  externally,  the  anti- 
brachial aponeurosis. 

Preparation  of  the  muscles  of  the  forearm. — The  preparation  of  these  muscles  is  extremely 
simple,  as  it  suflBces  to  remove  the  antibrachial  aponeurosis  and  the  interstitial  cellulo-adipose 
tissue,  to  expose  and  to  isolate  them  from  each  other.  No  special  recommendations  need  there- 
fore be  given,  as  a  glance  at  Figs.  179,  181,  182,  and  183  will  guide  the  student  in  his  dissec- 
tion, and  supplement  the  manual  details  which  would  be  superfluous  here. 

Nevertheless,  as  the  terminal  insertions  of  some  of  these  muscles  are  enclosed  witliin  the 
hoof,  and  as  it  is  indispensable,  in  order  to  expose  them,  to  remove  this  horny  case,  some 
explanation  will  be  given  as  to  the  manner  in  which  this  should  be  effected,  particularly  as 
the  apparent  difficulty  and  labour  too  frequently  cause  this  part  to  be  omitted  in  the  dissecting- 
rooms. 

1.  The  instruments  necessary  to  remove  the  hoof  are  :  a  scalpel,  toe-knife,  hammer,  and  a 
pair  of  pincers. 

2.  The  limb  siiould  be  in  a  vertical  position,  held  by  one  or  two  assistants,  and  the  foot 
placed  on  a  table,  stool,  or  very  soliti  block  of  wood. 

3.  Pass  the  scalpel  as  deeply  as  possible  around  the  coronet,  to  separate  the  wall  of  the 
hoof  from  the  organized  tissues. 

4.  With  the  knife  and  hammer,  split  the  wall  into  four  or  five  pieces  by  vertical  incisions. 

5.  When  the  wall  is  thus  divided,  it  is  sufficient  to  insert  the  knife  under  the  fragments, 
and,  making  it  serve  as  a  lever,  tear  them  off;  pincers  may  also  be  used  for  this  purpose,  each 
of  the  pieces  being  twisted  from  the  sole. 

6.  To  remove  the  sole,  the  blade  of  the  scalpel  should  be  passed  between  its  upper  face  and 
the  plantar  stufuce  of  the  third  phalanx ;  afterwards  the  toe-knife  may  be  inserted  in  the 
interval  at  the  bulbs  of  the  frog,  so  as  to  slightly  raise  the  external  border  of  the  sole.  This  is 
then  seized  by  the  pincers  and  pulled  off,  along  with  the  frog,  in  a  single  piece,  by  a  powerful 
twisting  movement,  aided  by  the  assistants,  who  press  on  the  limb  in  a  contrary  direction. 

A.  Antekior  Antibrachial  Region. 

In  Solipeds,  this  region  includes  four  extensor  muscles.  Two  act  on  the 
entire  foot ;  these  are  the  anterior  extensor  and  the  oblique  extensor  of  the  meta- 
carpus. Two  others — the  anterior  and  the  lateral  extensor  of  the  phalanges— 
terminate  in  the  digital  region. 

1.  Anterior  Extensor  of  the  Metacarpus  (Extensor  Metacarpi  Magnus) 
(Figs.  179,  11  ;   181,  15  ;   182,  9). 

Synonyms — Epicondylo-premetacarpeus — Girard.  It  represents  the  two  external  radials 
of  Man.     (Humero-metacarpeus — Leyh.) 

Situation — Direction — Form — Structure. — This  muscle,  situated  in  front  of 
the  radius,  in  an  almost  vertical  direction,  is  composed  of  a  muscular  body  and 
a  tendon.  The  first  has  the  form  of  an  inverted  cone,  is  intersected  by  some 
aponeurotic  layers,  and  is  composed  of  muscular  fibres  slightly  arciform  at  their 
superior  extremities.  The  tendon,  at  first  rounded,  then  flattened,  commences 
below  the  middle  third  of  the  radius,  and  succeeds  the  inferior  extremity  of  the 
muscular  portion. 

Attadiments. — This  muscle  has  its  fixed  insertion  :  1.  By  the  upper  extremity 
of  its  fleshy  fibres,  on  the  crest  that  limits,  behind  and  below,  the  musculo-spiral 
groove  of  the  humerus.  2.  Above  and  in  front  of  the  inferior  articular  surface 
of  the  humerus,  by  means  of  a  strong  fibrous  band  common  to  it  and  the 
anterior  extensor  of  the  phalanges,  and  which  expands  on  the  deep  face  of  these 


324  THE  MUSCLES. 

two  muscles  in  becoming  intimately  united  with  the  capsular  ligament  of  the 
elbow  articulation.  Its  movable  insertion  takes  place  on  the  anterior  and 
superior  tuberosity  of  the  large  metacarpal  bone,  by  the  inferior  extremity  of  its 
tendon. 

Relations. — The  muscular  portion  is  covered  by  the  antibrachial  aponeurosis 
and  the  short  extensor  of  the  forearm.  It  covers  the  anterior  face  of  the  radius, 
as  well  as  the  elbow  articulation  ;  outwards  and  behind,  it  is  in  contact  with  the 
inferior  extremity  of  the  short  flexor  of  the  forearm  or  humeralis  obliquus,  the 
aponeurosis  of  which  adheres  intimately  to  the  arciform  portion  of  the  fibres  of 
the  anterior  extensor  of  the  metacarpus,  and  appears  to  attach  this  muscle  to  the 
deltoid  imprint.  Its  tendon  covers  a  small  portion  of  the  anterior  aspect  of  the 
radius,  and  enters  the  internal  vertical  groove  channeled  in  front  of  the  inferior 
extremity  of  that  bone  ;  afterwards  it  passes  over  the  capsular  ligament  of  the 
carpus,  and  is  maintained  against  that  membranous  expansion  by  a  wide  fibrous 
sheath,  through  which  it  glides  by  the  aid  of  two  synovial  membranes  (Fig.  183). 
This  tendon  is  crossed  above  the  knee  by  that  of  the  oblique  extensor,  which 
passes  to  its  surface. 

Action. — The  name  of  this  muscle  indicates  its  function ;  it  extends  the 
metacarpus  on  the  forearm. 

2.  Oblique  Extensor  of  the  Metacarpus  (Extensor  Metacarpi 
Obliquus)  (Figs.  179,  13  ;  181,  21 ;  182,  14). 

Synonyms. — Cubito-premetacarpeus,  or  radio-premetacarpeus — Girard.  It  is  the  repre- 
sentative of  the  long  abductor  and  short  extensor  of  the  thumb  in  Man.  (Extensor  metacarpi 
obliquus  vel  parvus — Percivall.     Badio-metacarpeus — Leyh.) 

Situation — Form — Structure — Direction. — A  small  muscle  situated  at  the 
internal  side  of  the  radius,  beneath  the  anterior  extensor  of  the  phalanges, 
penniform  in  shape,  strongly  aponeurotic,  and  terminated  by  a  tendon  which 
turns  obhquely  round  the  anterior  aspect  of  the  radius,  in  passing  downwards 
and  inwards  to  reach  the  oblique  channel  on  the  inferior  extremity  of  that  bone, 
and  to  pass  thence  to  the  inside  of  the  knee. 

Attachments. — It  has  its  origin  on  the  external  side  of  the  radius ;  its 
terminal  tendon  is  fixed  into  the  head  of  the  internal  metacarpal  bone,  by  its 
fibres  becoming  mixed  with  those  of  the  internal  ligament  of  the  carpus. 

Relations. — It  is  covered  by  the  anterior  extensor  of  the  phalanges  and 
the  antibrachial  aponeurosis.  It  successively  covers  the  anterior  face  of  the 
radius,  the  tendon  of  the  anterior  extensor  of  the  metacarpus,  the  radial  groove 
lodging  its  tendon,  and  in  which  it  glides  by  means  of  a  small  synovial  bursa,  as 
well  as  the  internal  ligament  of  the  carpus. 

Action. — It  extends  the  metacarpus,  and  may  make  it  pivot  from  within 
forwards. 

3.  Anterior  Extensor  of  the  Phalanges  (Extensor  Pedis) 
(Figs.  179,  14  ;  181,  15  ;  182,  9). 

Synonyms. — Epicondylo-prephalangeus — Girard.  The  extensor  communis  digitorum  of 
Man.     (Eumero-prephalangeus — Leyh.) 

Situation — Direction — Extent — For7n — Strticture. — This  is  a  long  vertical 
muscle,  situated  external  to  and  behind  the  anterior  extensor  of  the  metacarpus, 
which  it  resembles  in  being  composed  of  a  fleshy  and  a  tendinous  portion.     The 


MUSCLES  OF  TEE  ANTERIOR  LIMBS.  325 

muscular  portion  extends  from  the  inferior  extremity  of  the  humerus  to  above 
the  lower  third  of  the  radius  ;  it  is  fusiform  in  shape,  intersected  by  aponeurotic 
layers,  and  bifid  at  its  superior  extremity.^  The  tendinous  portion  forms  two 
unequal  cords,  which  succeed  the  two  terminal  branches  of  the  muscular  part, 
and  lie  closj  to  each  other.  These  two  cords  enter  the  most  external  of  the 
three  grooves  in  front  of  the  inferior  extremity  of  the  radius,  and  reach  the 
anterior  face  of  the  carpal  capsular  ligament,  against  which  they  are  maintained 
by  an  annular  ligamentous  apparatus.  After  passing  from  beneath  this  ring,  the 
smallest,  which  is  the  most  external,  joins  the  tendon  of  the  lateral  extensor  (Fig. 
179,  15).  The  principal  branch  (Fig.  179,  14')  continues  its  course  on  the 
anterior  aspect  of  the  middle  metacarpal  bone  and  articulation  of  the  fetlock, 
until  it  arrives  in  front  of  the  digit ;  here  it  terminates  on  the  os  pedis,  after 
widening  in  a  remarkable  manner,  and  after  receiving,  laterally,  at  the  middle  of 
the  first  phalanx,  a  reinforcing  band  which  appears  to  be  given  off  from  the 
inferior  extremity  of  the  suspensory  ligament  of  the  fetlock. 

Attachments. — It  has  its  fixed  attachment  by  the  superior  extremity  of  its 
muscular  body.  1.  Below  the  crest  that  limits,  posteriorly,  the  musculo- 
spiral  groove  of  the  humerus.  2.  In  front  of  the  inferior  extremity  of  the 
humerus.  3.  To  the  anterior  border  of  the  external  ligament  of  the  elbow-joint. 
4.  To  the  external  and  superior  tuberosity  of  the  radius.  5.  To  the  external 
border  of  that  bone.  Its  principal  tendon  is  inserted  into  the  pyramidal  process 
of  the  third  phalanx,  after  being  successively  attached  to  the  capsular  ligament 
of  the  fetlock-joint  and  the  anterior  surfaces  of  the  first  two  phalanges. 

Relations. — The  muscular  portion,  covered  by  the  antibrachial  aponeurosis, 
covers  the  articulation  of  the  elbow,  the  anterior  face  of  the  radius,  and  the 
oblique  extensor  of  the  metacarpus ;  it  responds,  in  front,  to  the  anterior 
extensor  of  the  same  bone,  to  which  it  is  intimately  attached  by  its  upper  half  • 
behind,  to  the  lateral  extensor  of  the  phalanges.  The  tendinous  cords  cover  the 
different  parts  already  enumerated  in  describing  the  course  of  the  muscle — that 
is,  the  anterior  face  of  the  radius,  the  carpal  joints,  the  principal  metacarpal  bone, 
the  articulation  of  the  fetlock,  and  the  first  two  phalanges.  A  vaginal  synovial 
membrane  envelops  them  at  the  knee,  to  facilitate  their  gliding  in  the  radial 
groove  and  on  the  anterior  aspect  of  the  capsular  ligament  of  the  carpus  ;  while 
the  inner  surface  of  the  principal  tendon  is  covered,  in  front  of  the  fetlock,  by  a 
small  vesicular  capsule,  and,  still  lower,  by  the  synovial  membranes  of  the  two 
inter-phalangeal  articulations. 

Action. — This  muscle  extends  the  third  phalanx  on  the  second,  that  on  the 
first,  and  this  again  on  the  metacarpal  bone.  It  may  also  concur  in  the  extension 
of  the  entire  foot  on  the  forearm. 

(Two  small  muscles,  which  should  be  only  considered  as  heads  of  this  anterior 
extensor,  have  been  particularly  described  by  Thiernesse  and  Phillips,  and  named 
after  these  authors. 

The  7nuscle  of  Phillips,  according  to  Leyh,  is  long  and  thin  ;  it  commences 
on  the  lateral  external  ligament  of  the  ulnar  articulation  and  the  external 
superior  tuberosity  of  the  radius  ;  it  is  directed  obliquely  downwards  and 
forwards,  lying  beside  the  muscular  portion  of  the  common  extensor.  Towards 
the  middle  and  outer  aspect  of  the  radius,  it  gives  off  a  small  tendon,  which 
passes  in  the  same  sheath  as  the  preceding,  in  front  of  the  carpus,  and  continues 

'  This  division,  which  has  been  noticed  by  several  writers,  has  not  been  shown  in  Fig.  179 
This  is  it  mistake,  us  it  is  constantly  present. 


326  THE  MUSCLES. 

its  course  between  the  two  tendons  of  the  extensors  of  the  phalanges  to  the  near 
fetlock,  where  it  becomes  mixed  with  that  of  the  lateral  extensor,  a  little  above 
the  first  phalanx. 

The  muscle  of  Thiernesse  is  smaller  than  that  of  Phillips,  and  situated  at  its 
inner  side.  It  arises,  in  front  of  the  transverse  ligament  of  the  ulna,  by  a 
muscular  portion,  becomes  thinner  as  it  descends,  and  terminates  by  a  fine 
tendon  which  is  confounded  with  that  of  the  common  extensor,  towards  the 
lower  third  of  the  forearm.) 

4.  Lateral  Extensor  of  the  Phalanges  (Extensor  Suffraginis) 
(Figs.  179,  16  ;  182,  13). 

Synonyms. — Cubito  or  radialis-prephalangeus,  according  to  Girard.     The  extensor  minimi 
digiti  of  Man. 

Direction — Situation — Extent — Form — Structure. — A  small  vertical  muscle, 
situated  at  the  external  side  of  the  forearm,  between  the  preceding  and  the 
external  flexor  of  the  metacarpus,  and  formed  of  a  fleshy  body  and  a  tendon. 
The  body,  not  very  considerable,  and  flattened,  extends  from  the  upper  extremity 
of  the  radius  to  its  lower  fourth.  The  tendon  (Fig.  179,  16'),  at  first  rounded, 
then  flattened,  reaches  the  gliding  groove  which  divides  the  external  inferior 
tuberosity  of  the  radius  into  two  portions,  passes  to  the  external  side  of  the 
carpus,  crossing  the  lateral  ligament  common  to  the  articulations  of  this  region, 
and  arrives  at  the  anterior  surface  of  the  principal  metacarpal  bone,  where  it 
receives  the  small  tendinous  branch  detached  from  the  anterior  extensor,  as  well 
as  a  strong  fibrous  band  coming  from  the  external  side  of  the  carpus  (Fig.  179, 
17).  Afterwards,  descending  alongside  the  external  border  of  the  principal 
tendon  of  its  congener,  and  united  to  it  by  a  fibrous  fascia,  it  gains  the  articula- 
tion of  the  fetlock,  and  expanding,  terminates  at  the  upper  extremity  of  the  first 
phalanx. 

Attachments. — 1.  By  its  muscular  body,  to  the  external  tuberosity  of  the 
radius,  the  external  ligament  of  the  elbow  articulation,  and  to  the  bodies  of  the 
two  bones  of  the  forearm — origin.  2.  By  the  inferior  extremity  of  its  tendon, 
to  the  capsule  of  the  metacarpo-phalangeal  articulation,  and  in  front  of  the 
superior  extremity  of  the  first  phalanx — termination. 

Relations. — Its  muscular  portion,  enveloped  in  a  special  aponeurotic  sheath, 
responds  :  in  front,  to  the  anterior  extensor  of  the  phalanges  ;  behind,  to  the 
external  flexor  of  the  metacarpus,  and  the  perforatus  and  perforans  muscles  ; 
outwards,  to  the  antibrachial  aponeurosis.  The  tendon,  surrounded  by  a  vaginal 
synovial  sheath,  in  passing  over  the  carpus,  covers,  beyond  the  knee,  the  anterior 
aspect  of  the  metacarpus  and  the  anterior  ligament  of  the  metacarpo-phalangeal 
articulation,  over  which  it  glides  by  means  of  a  small  vesicular  synovial  bursa. 
It  is  covered  by  a  slight  fascia,  which  separates  it  from  the  skin,  and  which  is 
also  spread  over  the  tendon  of  the  anterior  extensor. 

Action. — This  muscle  is  an  extensor  of  the  digit,  and  also  concurs  in  the 
extension  of  the  entire  foot  on  the  forearm. 

In  the  Ass,  this  muscle  is  proportionately  much  smaller  than  in  the  Horse. 

B.  Posterior  Antibrachial  Region. 

This  is  composed  of  five  flexor  muscles  grouped  vertically  behind  the  bones 
of  the  forearm.     Three  are  situated  superficially,  and  act  on  the  whole  of  the 


MUSCLES  OF  TEE  ANTERIOR   LIMBS.  327 

foot ;  these  are  the  external  flexor,  oblique  flexor,  and  the  internal  flexor  of  the 
metacarpus.  The  other  two,  fixed  to  the  digit  by  their  inferior  extremity,  and 
covered  by  the  preceding,  are  designated  the  superficial  and  deep  flexors  of  the 
phalanges. 

Superflcial  Layer. 

1.  ExTEENAL  Flexor  of  the  Metacarpus  (Flexor  Metacarpi  Externus), 
OR  Posterior  UtNARis^  (Fig.  179,  18). 

Synonyms. — Epicondylo-supercarpeus — Girard.     (Humero-supercarpeus  externus — Leyh.) 

Situation. — The  external  flexor  of  the  metacarpus  is  situated  at  the  external 
side  of  the  forearm,  between  the  lateral  extensor  of  the  phalanges  and  the 
oblique  flexor. 

Form — Structure — Attachments. — This  muscle  is  elongated  from  above  to 
below,  flattened  on  both  sides,  thick  in  the  middle,  and  intersected  by  very 
strong  aponeurotic  bands.  It  commences  on  the  summit  of  the  epitrochlea  by 
a  very  powerful,  but  extremely  short  tendon.  Inferiorly,  it  terminates  by  a 
second  tendon  longer  than  the  preceding,  and  divides  into  two  branches,  an 
anterior  and  a  posterior.  The  latter  (Fig.  179,  20),  short  and  wide,  is  inserted 
into  the  pisiform  bone  in  becoming  mixed  with  the  oblique  flexor.  The  former 
(Fig.  179,  19),  roimded  and  funicular  in  shape,  glides  by  means  of  a  synovial 
bursa  in  the  channel  excavated  on  the  external  aspect  of  the  pisiform  bone,  and 
which  is  converted  into  a  canal  by  a  little  fibrous  apparatus  ;  this  branch  is  after- 
wards fixed  on  the  head  of  the  external  metacarpal  bone,  by  being  confounded 
with  the  external  hgament  of  the  carpus. 

Relations. — Covered  by  the  antibrachial  aponeurosis,  this  muscle  covers  the 
two  flexors  of  the  digit.  Its  anterior  border  responds  to  the  lateral  extensor  of 
the  phalanges  ;  the  posterior  to  the  oblique  flexor.  Its  superior  tendon  lies 
behind  the  external  ligament  of  the  elbow- joint,  and  is  covered  deeply  by  the 
external  cul-de-sac  of  the  synovial  capsule  belonging  to  that  articulation. 

Action. — It  flexes  the  foot  on  the  forearm.  (Leyh  observes  that  it  is  more 
particularly  concerned  in  what  is  known  as  "  high  action.") 

2.  Oblique  Flexor  of  the  Metacarpus  (Flexor  Metacarpi  Medius), 
or  Anterior  Ulnaris  (Fig.  180,  18). 

Synonyms. — Epitrochlea  supercarpeus — Girard.     (Humero-metacarpeus  internus — Leyh.) 

Situation — Form — Structure. — This  muscle,  situated  behind  and  within  the 
forearm,  is  an  exact  counterpart  of  the  preceding  in  form  and  structure. 

Direction. — Bourgelat  has  improperly  named  it  an  oblique  flexor,  for  its  direc- 
tion is  vertical  like  that  of  the  other  muscles  of  this  region. 

Attachments. — It  has  its  origin  :  1.  On  the  base  of  the  epitrochlea  by  the 
tendinous  fibres  of  its  superior  extremity.  2.  On  the  olecranon,  by  a  small,  very 
thin,  and  very  pale  fleshy  band,  which  is  annexed  to  the  principal  muscular  body, 
and  soon  unites  with  its  posterior  border.     Its  inferior  tendon  is  undivided,  and 

'  It  is  known  that  the  bony  eminences,  hitherto  termed  in  veterinary  anatomy  "  epitrochlea  " 
and  "  epicondyle,"  correspond  :  the  first,  to  the  epicondyle  of  Man,  the  second,  to  the  epi- 
trochlea. It  need  excite  no  surprise,  therefore,  to  see  the  denominations  given  by  Girard  to 
the  muscles  of  the  posterior  antibrachial  region  changed  as  above. 


828  THE  MUSCLES. 

terminates  on  the  pisiform  bone,  along  with  the  external  flexor,  to  which  it  is 
intimately  attached. 

Relations. — By  its  superficial  face,  with  the  antibrachial  aponeurosis,  which 
strongly  adheres  to  its  tendon  ;  by  its  deep  face,  with  the  flexors  of  the  phalanges. 
Its  anterior  border  is  covered  by  the  internal  flexor ;  the  posterior  responds  to 
the  external  flexor. 

Action. — It  is  a  congener  of  the  preceding. 

3.  Internal  Flexor  of  the  Metacarpus  (Flexor  Metacarpi  Internus), 
OR  Palmaris  Magnus  (Fig.  181,  19). 

Synonyms. — Epitrochlea  metacarpeus — Girard.     (Humero-metacarpeus  internus — Leyh.) 

Situation— Form — Structure — Attachments. — This  muscle  is  situated  within 
the  forearm,  against  the  posterior  face  of  the  radius,  and  in  its  general  features 
resembles  its  congeners,  the  two  preceding  muscles.  It  is,  however,  not  so  wide, 
is  thinner,  and  less  aponeurotic.  Its  upper  extremity  is  fixed,  by  tendinous 
fibres,  to  the  base  of  the  epitrochlea  at  the  same  point  as  the  oblique  flexor,  with 
which  it  is  confounded — origin.  Its  inferior  extremity  terminates  in  a  long,  thin, 
funicular  tendon  which  passes  through  a  fibrous  sheath  at  the  inner  side  of  the 
knee,  and  is  inserted  into  the  head  of  the  internal  metacarpal  bone — movable 
insertion. 

Relations. — It  is  covered  by  the  antibrachial  aponeurosis,  and  covers  the 
oblique  flexor,  the  perforatus  and  perforans,  as  well  as  important  blood-vessels 
and  nerves.  Its  anterior  border  responds  to  the  radius.  A  synovial  sheath 
envelops  its  terminal  tendon,  and  facilitates  its  movements  in  the  fibrous  canal 
through  which  it  passes. 

Action. — It  is  a  congener  of  the  preceding. 


4.  Superficial  Flexor,  Sublimis  of  the  Phalanges,  or  Flexor  Pedis 
Perforatus  (Figs.  179,  181,  182). 

Synonyms. — Epitrochlo-phalangeus — Girard.  (Humero-coronarls  or  humero-phalangeus — 
Leyh.) 

Situation. — The  superficial  flexor  of  the  phalanges  is  situated,  with  its  fellow, 
the  perforans,  beneath  the  flexors  of  the  metacarpus,  which  form  around  them  a 
kind  of  muscular  envelope. 

Form — Structure — Extent. — It  is  composed  of  a  muscular  and  tendinous 
portion.  The  first,  long,  thin,  prismatic,  and  divided  by  a  great  number  of 
aponeurotic  intersections,  extends  from  the  inferior  extremity  of  the  arm  nearly 
to  the  carpus.  The  tendon,  continuous  with  the  inferior  extremity  of  the 
muscular  portion,  receives  at  its  origin  an  enormous  fibrous  production  {superior 
carpal  or  check  ligam,ent),  that  arises  from  the  eminence  of  insertion  situated  at 
the  posterior  face  of  the  end  of  the  radius,  and  which  contracts  somewhat 
intimate  adhesions  with  the  antibrachial  aponeurosis,  as  well  as  with  the 
perforans. 

After  being  thus  reinforced,  this  tendon  passes  through  the  carpal  sheath 
and  arrives  behind  the  fetlock,  where  it  forms  a  ring  (Fig.  183,  21)  for  the 
passage  of  the  tendon  of  the  deep  flexor.  To  this  peculiarity  is  owing  the  de- 
signations of  mrforatus  and  perforans.,  given  to  the  two  flexors  of  the  phalanges. 


MUSCLES  OF   THE  ANTERIOR  LIMBS. 


Fig   183 


Afterwards,  it  is  inflected  forwards  over  the  sesamoid  groove,  and  terminates  by 
two  branches  towards  the  middle  of  the  digital  region. 

Attachments. — It  takes  its  origin,  in  common  with  the  perforans,  at  the 
summit  of  the  epitrochlea,  and  is  inserted, 
by   the    bifurcations    of    its    tendon,   into 
the  extremities  of  the  pulley  formed  behind 
the  superior  extremity  of  the  second  phalanx. 

Relations.  —  The  muscular  portion, 
covered  by  the  external  and  the  oblique 
flexors  of  the  metacarpus,  may  be  said  to 
be  embedded  in  the  perforans,  to  which  it 
adheres  in  the  most  intimate  manner.  The 
tendon  covers  that  of  the  latter  muscle,  and 
is  in  turn  covered  by  the  fibrous  expansions 
of  the  two  metacarpal  and  metacarpo- 
phalangeal sheaths,  which  are  now  to  be 
described. 

Carpal  sheath  is  the  name  given  to  a 
very  remarkable  annular  apparatus,  formed 
by  the  superficial  face  of  the  common  pos- 
terior ligament  of  the  carpus,  and  by  a  thick 
expansion  of  white  fibrous  tissue,  together 
constituting  a  perfect  arch  thrown  across  like 
a  bridge,  from  the  pisiform  bone  to  the  inner 
side  of  the  carpus.  This  arch  is  continuous, 
above,  with  the  antibrachial  aponeurosis, 
and  is  prolonged,  below,  over  the  metacarpal 
portion  of  the  flexor  tendons.  An  extensive 
synovial  membrane  covers  the  internal  aspect 
of  the  carpal  sheath,  envelops  the  perforatus 
and  perforans  in  their  passage  through  this 
canal,  ascends  above  the  carpus,  and  descends 
below  the  lower  third  of  the  metacarpal 
region  (Fig.  183,  4,  4),  where  it  is  insinuated 
between  the  tendon  of  the  perforans  and  its 
carpal  ligament.  This  synovial  membrane 
is  strengthened  in  its  middle  portion  by  the 
walls  of  the  carpal  sheath  ;  so  that  when 
hypersecretion  takes  place  in  it,  this  is  only 
perceived  by  a  swelling  above  the  knee,  ex- 
ternally, between  the  posterior  face  of  the 
radius  and  the  flexor  muscles  (Fig.  183,  3), 
and  another  swelling  at  the  tendons  behind 
the  metacarpus. 

The  Metacarpo-phalangeal  sheath  is 
formed  by  the  sesamoid  groove,  the  posterior 


TENDONS  AND  SYNOVIAL   SHEATHS  OF  THE 
ANTERIOR    LIMB    OF   THE    HORSE. 

M,  Metcarpal  bone  ;  El,  lateral  extensor  of 
the  phalanges  ;  Ea,  anterior  extensor  of 
the  phalanges  ;  Fs,  tendon  of  the  super- 
ficial flexor  of  the  phalanges  (perforatus); 
Fp,  tendon  of  the  deep  flexor  of  the 
phalanges  (perforans)  ;  Ls,  suspensory- 
ligament  of  the  fetlock.  1,  Bursa  for 
the  tendon  of  the  anterior  extensor  of 
the  metacarpus ;  2,  supero-external  cul- 
de-sac  of  the  radio-carpal  bursa;  3,  superior  cul-de-sac  of  the  carpal  bursa;  4,  4,  inferior  portion 
of  same ;  5,  cul-de-sac  of  the  capsule  of  the  metacarpo-phalangeal  articulation  ;  6,  7,  8,  superior, 
middle,  and  inferior  culs-de-sac  of  the  sesamoid  bursa;  9,  inferior  extremity  of  the  same  exposed 
by  excision  of  the  reinforcing  sheath  of  the  perforans  tendon. 


330  THE  MUSCLES. 

face  of  the  principal  navicular  ligaments,  that  of  the  glenoid  fibro-cartilage  of  the 
first  interphalangeal  articulaticn,  and  by  the  posterior  pulley  of  the  second 
phalanx  (Fig.  183,  5).  It  is  completed  by  a  very  wide  membranous  expansion 
applied  against  the  flexor  tendons,  closely  adherent  to  the  perforatus  on  the 
median  line  of  the  digit,  and  fixed,  laterally,  to  the  phalangeal  bones  by 
the  aid  of  three  special  fibrous  bands  (Fig.  184,  6,  7,  8).  A  very  extensive 
vaginal  synovial  membrane  covers  the  internal  walls  of  this  passage,  and  is 
reflected  on  the  flexor  tendons  ;  it  ascends  along  these  tendons  to  the  inferior 
extremities  of  the  lateral  metacarpals  (Fig.  183,  6),  and  forms,  inferiorly,  a 
somewhat  large  cul-de-sac  which  envelops  the  perforans  tendon  (Fig.  183,  9), 
and  behind  the  second  phalanx  lies  against  the  posterior  cul-de-sac  of  the 
articular  synovial  membrane  of  the  foot,  and  also  against  the  superior  cul-de-sac  of 
the  navicular  sheath  (Fig.  137,  14).  The  metacarpo-phalangeal  sheath  is  also 
named  the  ffreat  sesamoid  sheath ;  but  this  designation  is  more  frequently 
applied  to  the  synovial  membrane  lining  its  walls.  When  this  bursa  is  distended 
by  the  fluid  it  secretes,  it  projects  at  all  those  points  where  it  is  not  supported 
by  the  fibrous  walls  of  the  metacarpo-phalangeal  sheath.  Then  are  formed  above 
the  metacarpo-phalangeal  articulation,  and  between  the  suspensory  ligament  of 
the  fetlock  and  flexor  tendons,  as  well  as  below  the  fetlock — between  the  fibrous 
bands  which  attach  the  sheath  to  the  first  phalanx — those  small  tumours  named 
"windgalls"  (Fig.  183,  6,  7,  8).  The  inferior  cid-de-sac  (Fig.  183,  9)  seldom 
appears  externally,  as  it  is  sustained  by  the  reinforcing  sheath  of  the  perforans 
tendon. 

Action. — This  muscle  flexes  the  second  phalanx  on  the  first,  that  on  the  meta- 
carpus, and  the  entire  foot  on  the  forearm.  Its  tendon,  through  the  influence 
of  the  fibrous  band  which  attaches  it  to  the  posterior  face  of  the  radius,  acts 
mechanically  as  a  stay  while  the  animal  is  standing,  by  maintaining  the  meta- 
carpo-phalangeal angle. 

5.  Deep  Flexor  of  the  Phalanges,  or  Flexor  Pedis  Perforans 
(Figs.  179,  181,  182,  183). 

Synonyms. — Cubito-phalangelis,  or  radio-phalangeus — Girard.  (Humero-rndio-phdlangeus — 
Leyh.) 

Situation — Composition — Extent. — This  muscle  is  situated  immediately  behind 
the  radius,  and  is  composed  of  three  portions  which  unite  at  the  carpus,  to  be 
continued  to  the  inferior  extremity  of  the  digit  by  a  long  and  powerful  tendon. 

Form,  Structure,  and  Attachments  of  the  muscular  lioriion  of  the  perforans. — 
The  three  muscular  portions  may  be  distinguished,  in  regard  to  their  origin,  into 
humercd,  ulnar,  and  radial. 

The  humeral  portion  is  the  most  considerable,  and  lies  beside  the  perforatus  ; 
being  three  or  four  times  the  volume  of  that  muscle,  it  is  easily  divided  into 
several  very  tendinous  fasciculi,  which  leave  the  summit  of  the  epitrochlea  along 
with  the  superficial  flexor.  The  ulnar  portion,  situated  between  the  external 
flexor  and  the  oblique  flexor  of  the  metacarpus,  is  very  short  and  conoid,  thick 
at  its  superior  extremity,  contracted  at  its  inferior,  to  which  succeeds  a  long  flat 
tendon,  united  below  to  the  principal  tendon  ;  it  has  its  origin  on  the  summit 
and  the  posterior  border  of  the  olecranon.  The  radial  jwrtion  (or  radialis 
accessorius)  ^  is  the  smallest,  and  is  deeply  concealed  beneath  the  epitrochlean 

'  It  represents  the  flexor  longus  pollicis  of  Man. 


MUSCLES   OF  THE  ANTERIOR  LIMBS. 


muscular  portion.  The  fibres  composing  it  are  fixed  to  the  posterior  surface  of 
the  radius,  where  they  are  slightly  divergent,  and  collect  upon  a  small  particular 
tendon,  which  is  confounded  with  the  common  tendon  after  contracting  adhesions 
with  the  radial  band  of  the  perforatus. 

Course  and  Attachments  of  the  tendon. — The  tendon  which  succeeds  these 
three  portions,  enters  the  carpal  sheath  with  that  of  the  superficial  flexor. 
Towards  the  middle  of  the  metacarpal  region,  it  receives  a  strong  fibrous  band 
from  the  great  posterior  ligament  of  the  carpus  (Figs.  179,  23  ;  182,  18), 
traverses  the  sesamoid  annular  apparatus  of  the  perforatus  tendon 
between  the  two  terminal  branches  of  that  tendon,  over 
the  pulley  on  the  posterior  face  of  the  second  phalanx, 
and  afterwards  widens  to  form  a  large  expansion  desig- 
nated the  plantar  aponeurosis. 

This  aponeurosis  glides,  by  its  anterior  face,  over  the 
inferior  surface  of  the  navicular  bone,  by  means  of  a 
particular  synovial  membrane — the  navicular  sheath — 
and  is  covered,  posteriorly,  by  a  fibrous  layer,  noticed  for 
the  first  time  by  H.  Bouley,  who  considered  it  a  reinforcing 
sheath  for  the  perf orans  tendon.  It  is  finally  inserted  into 
the  semilunar  crest  of  the  os  pedis,  and  the  median 
imprints  situated  behind  this  crest,  becoming  confounded 
at  its  sides  with  the  tissue  of  the  lateral  fibro-cartilages. 

The  navicular  sheath  is  vesicular  in  form  ;  it  covers 
the  navicular  bone  and  the  single  ligament  of  the  pedal 
articulation,  becomes  reflected  on  the  plantar  aponeurosis 
in  front  of  this  ligament,  and  ascends  to  the  inferior  cul- 
de-sac  of  the  sesamoid  sheath,  where  it  is  again  reflected 
and  continued  by  itself.  It  therefore  forms  two  cids-de- 
sac — one  superior,  the  other  inferior — which  are  readily 
perceived  in  a  longitudinal  and  vertical  section  of  the  digital 
region  (Fig.  137,  15,  16).  The  first  is  in  contact  with 
the  posterior  cul-de-sac  of  the  synovial  membrane  of  the 
pedal  articulation,  and  is  separated  from  the  inferior  sac 
of  the  sesamoid  sheath  by  a  transverse  layer  of  yellow 
fibrous  tissue,  which  attaches  the  perf  orans  tendon  to  the 
posterior  face  of  the  second  phalanx.  The  second  is 
situated  beneath  the  interosseous  ligament  which  unites 
the  navicular  bone  to  the  third  phalanx. 

The  reinforcing  sheath  of  the  perforans  tendon  is 
formed  by  a  fibrous  membrane,  applied  against  the  pos- 
terior face  of  the  plantar  aponeurosis.  This  membrane 
adheres  intimately  below,  to  the  expansion  it  covers,  and 
ends  in  becoming  entirely  confounded  with  it.  It  is  fixed, 
at  its  borders,  to  the  inferior  extremity  of  the  first  phalanx,  by  means  of  two 
lateral  bands  (Fig.  184,  3,  4),  and  to  the  metacarpo-phalangeal  sheath  by  a  small 
median  band.  The  latter  passes  on  to  the  lower  end  of  the  great  sesamoid 
synovial  sheath,  and  divides  it  into  two  lobes,  which  are  very  visible  when  the 
sheath  has  been  distended  by  injection. 

Relations. — The  epitrochlean  muscular  portion  is  covered,  at  its  origin,  by 
the  external  cul-de-sac  of  the  elbow-joint,  which  sac  also  covers  the  other  muscles 


FLEXOR  TENDONS  OF  THE 
PHALANGES  IN  THE  HORSE. 

I,  Perforatus  tendon  ;  2, 
tendon  of  the  perforans 
at  its  exit  from  between 
the  two  branches  of  the 
perforatus ;  3,  3,  its  in- 
sertion in  the  semilu- 
nar crest ;  4,  4,  the  two 
lateral  bands  of  its  re- 
inforcing sheath  ;  5,  5, 
fibrous  expansion  of  the 
metacarpo  -  phalangeal 
sheath ;  6,  7,  8,  its  lateral 
bands  ;  9,  9,  suspensory 
ligament  of  the  fetlock. 


332  THE  MUSCLES. 

attached  to  the  epitrochlea — the  external  and  oblique  flexors  of  the  metacarpus. 
It  responds,  anteriorly,  with  the  radius  and  radial  portion  of  the  muscle  ;  pos- 
teriorly, with  the  perforatus  ;  externally,  with  the  external  flexor  of  the  meta- 
carpus ;  inwardly,  with  the  internal  and  oblique  flexors  of  the  same  ray. 

The  ulnar  portion,  covered  by  the  antibrachial  aponeurosis,  covers  the  epi- 
trochlean  portion. 

The  radial  division  is  comprised  between  the  latter  and  the  posterior  face  of 
the  radius. 

The  tendon  is  in  contact,  posteriorly,  with  that  of  the  perforatus  ;  anteriorly, 
with  the  posterior  ligament  of  the  carpus,  the  suspensory  ligament  of  the  fetlock, 
and  the  sesamoid  groove  ;  by  its  sides,  with  the  vessels  and  nerves  of  the  digit. 
Its  terminal  expansion  is  covered  by  the  plantar  cushion,  which  adheres  to  it,  in 
front,  in  the  most  intimate  manner  ;  it  covers  the  navicular  bone. 

Admis. — This  muscle  flexes  the  phalanges  on  one  another  and  on  the  meta- 
carpus. It  also  concurs  in  the  flexion  of  the  entire  foot  on  the  forearm.  The 
band  which  attaches  its  tendon  behind  the  carpus,  as  well  as  its  phalangeal  rein- 
forcing sheath,  gives  it  the  mechanical  power  necessary  to  support  the  angle  of 
the  metacarpo-phalangeal  articulation  and  the  digital  region,  while  the  animal  is 
in  a  standing  posture. 

(In  the  "  Deep  Flexor,"  of  Chauveau's  description,  we  find  included  two 
portions  which  are  separately  named  and  described  by  Percivall  and  Gurlt. 
These  are  the  ulnaris  accessorius  and  radlaUs  accessorius  of  the  former,  and  the 
cuUto-ulnar  and  radial  branches  of  the  latter.  These,  in  reality,  are  portions 
of  the  perforans,  and  have  been  so  designated  in  this  treatise.  Though  arising 
independently,  they  terminate  in  the  perforans  tendon  before  it  leaves  the  carpal 
sheath,  and  join  with  it  in  flexing  the  metacarpus  and  phalanges.) 

DiFFEKENTlAL    CHARACTERS   IN   THE   MuSCLES   OF   THE  FOREARM   IN   THE   OTHER   AnIMALS. 

A.  Ruminants. — In  the  Ox,  Sheep,  and  Camel,  the  anterior  extensor  of  thp.  metacarpus 
comports  itself  as  in  Solipeds. 

The  oblique  extensor  of  the  same  region,  terminates  inside  the  upper  extremity  of  the  prin- 
cipal metacarpus. 

The  anterior  extensor  of  the  phalanges  offers  a  remarkable  arrangement.  It  is  divided 
throughout  its  leugtb  into  two  parallel  portions:  an  external,  which  forms  the  common  extensor 
of  the  digits ;  and  an  internal,  the  proper  extensor  of  the  internal  digit. 

a.  The  fleshy  body  of  the  common  extensor  (Fig.  185,  3)  is  a  little  more  voluminous  than 
that  of  the  second  muscle.  Its  tendon  (3')  commences  near  the  inferior  third  of  the  radius, 
passes  over  the  knee,  tlie  metacarpal  bone,  and  the  metacarpo-phalangeal  articulation.  On 
arriving  at  tlie  origin  of  the  digits  it  bifurcates,  and  each  of  its  branches  goes  to  be  inserted 
into  the  pyramidal  process  of  tlie  third  phalanx  (3").  This  muscle,  in  extending  the  digits,  brings 
them  together,  as  Lecoq  has  judiciously  remarked. 

b.  The  proper  extensor  of  the  internal  digit  (Fig.  185,  4)  much  resembles  the  common 
extensor  in  volume,  form,  and  direction.  Its  tendon  (4')  passes,  with  that  terminating  the 
latter  muscle,  into  one  of  the  inferior  grooves  of  the  radius  and  over  the  capsular  ligament  of 
the  carpus,  where  the  two  cords  are  enveloped  by  a  common  synovial  sheath.  Arrived  at  the 
metacarpo-phalangeal  articulation,  this  tendon  is  placed  at  the  eccentric  side  of  the  internal 
digit,  and  descends,  gradually  expanding,  until  it  reaches  the  inferior  extremity  of  this  bone; 
towards  the  middle  of  the  first  phalanx,  it  receives  from  the  suspensory  ligament  of  the  fetlock 
two  constraining  bands  similar  to  those  which,  in  Solipeds,  bind  the  anterior  extensor  of  the 
phalanges  on  the  same  bone.  This  tendon  bifurcHtes  inferiorly ;  one  of  its  branches  is  attached 
to  the  anterior  face  of  the  second  phalanx ;  tlie  other,  much  wider  than  tiie  first,  covers  the 
common  external  lateral  ligament  of  the  two  inter-phalaugeal  articulations,  and  terminates  on 
the  whole  external  side  of  the  third  phalanx.  In  the  Sheep,  this  second  branch  is  slender,  and 
is  directed  towards  the  heel,  which  it  envelops  by  uniting  its  iibres  with  the  perforans  tendon 
and  the  plantar  cushion. 


MUSCLES   OF   TEE  ANTERIOR   LIMBS. 


Fig.  185. 


The  lateral  extensor  of  the  phalanges  of  Ruminants  is  thicker  than  in  the  Horse,  and  con- 
stitutes tlie  proper  extensor  of  the  external  digit  (Fig.  185,  5).  Its  terminal  tendon  (4',  6,  7) 
comports  itself  exactly  the  same  as  thnt  of  the  proper  extensor  of  the  internal  digit,  and,  con- 
sequently, does  not  merit  special  description.  We  may  remark, 
with  Lecoq,  that  tiiese  two  muscles  separate  the  digits  from 
each  other  in  extending  tliem;  they  are,  therefore,  to  a  certain 
point,  antagonists  of  the  common  extensor. 

The  oblique  flexor  of  the  metacarpus  in  the  Camel  has  a 
very  thin  ulnar  portion,  rather  aponeurotic  tliau  muscular. 
The  inferior  tendon  of  that  muscle,  at  its  insertion  into  the  pisi- 
form bone,  detaches  a  baud  to  the  internal  border  of  the  carpus. 
In  this  animal,  the  internal  flexor  is  attached  to  the  superior 
extremity  <>f  the  internal  border  of  the  metacarpus. 

The  perforatus  of  the  Ox  and  Sheep  is  composed  of  two  por- 
tions, the  tendons  of  which  unite  towards  the  middle  of  tlie 
metacarpal  region.  The  single  tendon  (Fig.  186, 1,  2,  3)  which 
results  from  this  union  afterwards  divides  into  two  branches, 
each  of  which  comports  itself,  in  regard  to  the  digits,  as  the 
single  perforatus  tendon  does  in  the  Horse,  except  tliat  they 
receive  from  the  suspensory  ligament  a  fibrous  band  analogous 
to  that  which,  in  Solipeds,  goes  to  the  perforans  tendon.  This 
band  (Fig.  185,  13)  concurs  in  the  formation  of  the  annular 
ligament  through  which  the  latter  tendon  passes. 

In  the  Camel,  the  muscular  portion  of  tiie  perforatus  is  not 
present,  but  is  represented  by  a  tendinous  band,  the  arrangement 
of  which  is  curious.  It  arises  from  the  common  posterior  liga- 
ment of  the  carpus,  and  at  its  origin  adheres  firmly  to  the  branch 
of  the  suspensory  ligament  of  the  fetlock  which  descends  from  the 
pisiform  bone  ;  it  goes  behind  the  perforans  tendon,  where  it  is 
completely  covered  by  a  very  strong  white  membrane,  and  about 
the  middle  of  the  metacarpus  it  divides  into  two  branches  which 
separate  at  a  very  acute  angle.  Each  of  these  branches  glides  in 
the  sesamoidean  sheath,  the  posterior  wall  of  which  is  formed 
by  a  strong  layer  that  is  attached  to  the  sides  of  the  suspensory 
ligament  and  sesamoid  bones.  Below  these  bones,  these  two 
branches  bifurcate  in  their  turn  :  whence  results  four  branches, 
which  are  inserted  by  pairs  into  the  upper  extremity  of  the  two 
secondary  phalanges,  as  in  the  other  Ruminants. 

In  the  Ox,  tlie  terminal  tendon  of  the  perforans  does  not 
receive  any  carpal  band ;  this  goes  to  the  perloratus.  Above  the 
fetlock,  it  divides  into  two  branches,  one  for  each  digit,  which, 
after  traversing  the  perforatus,  terminates  behind  the  inferior 
face  of  the  third  phalanx.  There  it  is  blended  with  the  plantar 
cushion,  the  inferior  interdigital  ligament,  and  a  fibrous  fascia 
already  noticeil  in  the  description  of  that  ligament.  This  layer 
arises  from  the  aponeurosis  covering  the  flexor  tendons  in  the 
metacarpal  region  ;  it  descends  on  the  heels,  behind  and  outside 
the  digits,  remains  united  to  that  of  the  other  digit  by  an  in- 
termediate fibrous  fascia,  and  is  attached  to  the  enveloping 
sheaths  of  the  flexor  tendons,  as  well  as  to  the  superior  inter- 
digital ligament.  Each  terminates  inferiorly,  in  becoming 
united  to  the  proper  extensor  of  the  digit,  the  plantar  cushion, 
the  inferior  digital  ligament,  and  the  deep  flexor  of  the 
phalanges. 

There  is  not,  properly  speaking,  a  phalangeal  reinforcing 
sheath  ;  though  we  may  consider  as  such  the  superior  fasciculi 
of  the  inferior  interdigital  ligament  (Fig.  186,  6). 

Of  the  three  portions  of  the  perforans  in  the  Camel,  the 


MUSCLES  OF  THE  FOREARM  OP 
THE    OX    (INTERNAL   FACE). 

1,  Anterior  extensor  of  the 
metacarpus  ;  1',  insertion  of 
its  tendon ;  2,  oblique  ex- 
tensor; 3,  common  extensor 
of  the  digits ;  3',  its  tendon  ; 
3",  termmal  bifurcation  of 
that  tendon  ;  4,  proper  ex- 
tensor of  the  internal  digit ; 
4',  its  tendon ;  5,  proper 
extensor  of  the  external 
digit ;  5',  its  tendon  ;  6,  its 
branch  of  insertion  into  the 
second  phalanx  ;  7,  branch 
to  the  third  phalanx;  8, 
external  flexor  of  the  meta- 
carpus ;  9,  olecranian  por- 
tion of  the  perforans ;  10, 
tendon    of    the    perforans ; 

11,  tendon  of  the  perforatus; 

12,  suspensory  ligament  of 
the  fetlock;  13,   the    band 
it    furnishes    to    the    per- 
foratus to  form  the  ring  through    which  the  perforans  passes ;  14,  the  external   band  it   gives 
off  to  the  proper  extensor  of  the   external  digit ;  15,  flexor  brachii ;   16,  anterior  brachial ;  17, 


24 


334 


THE  MUSCLES. 


radial  is  the  largest.  The  tendons  of  the  three  divisions  become  united  in  the  carpal  sheath, 
and  the  resulting  tendon  is  easily  divisible  into  two  as  far  as  the  middle  of  the  metacarpus; 
there  it  bifurcates,  each  branch  passing  into  the  terminal  bifurcation  of  the  band  which  repre- 
sents the  perforatus  and  goes  to  be  inserted  into  the  third  phalanx,  where  it  is  covered  by  a 
small  reinforcing  sheath. 

B.  Pig  (Fig.  187). — In  this  animal,  the  anterior  extensor  tendon  of  the  phalanges  passes  to  the 
superior  extremity  of  the  inner  large  metacarpal  bone,  and  that  of  the  oblique  extensor  to  the  small 
internal  metacarpal. 

Instead  of  the  anterior  extensor  of  the  -phalanges,  four  muscles  are  found — 

1.  The  proper  extensor  of  the  great  internal  digit  alongside  the  anterior  extensor  of  the 

metacarpus ;  its  tendon  terminates  in  an  expansion  on  the  outside  of  the  great  internal  digit, 

after  receiving,  inwardly,  a  band  from  the  corresponding  interosseous  muscle.     It  gives  off, 

towards  the  middle  of  the  metacarpus,  a  very  thin  branch  which 

goes  to  the  outside  of  the  small  internal  digit. 

2.  The  proper  extensor  of  the  great  external  digit,  the  largest 
of  tlie  four,  terminates  in  the  same  manner  as  the  preceding,  on 
the  outside  of  the  great  external  digit. 

3.  The  common  extensor  of  the  two  internal  digits,  is  con- 
tinued by  a  tendon  which  bifurcates  above  the  metacarpus,  and 
gives  off  a  branch  that  reaches  the  pyramidal  process  of  the  small 
phalanx  of  the  internal  digit,  while  the  other  branch — the  most 
important — passes  into  the  space  between  the  metacarpals  of  the 
great  digits,  and  bifurcates,  in  its  turn,  in  front  of  the  metacarpo- 
phalangeal articulation,  to  terminate  on  the  pyramidal  process  of 
each  of  the  great  digits. 

4.  The  common  extensor  of  the  two  external  digits,  much 
smaller  than  the  preceding,  is  in  great  part  concealed  beneath  the 
proper  extensor  of  the  great  external  digit.  Its  somewhat  thin 
tendon  bifurcates  in  front  of  the  metacarpus,  to  give  a  branch  to 
the  small  external  digit,  going  to  the  pyramidal  process ;  and  a 
second  branch  that  goes  to  the  principal  tendon  of  the  preceding 
muscle,  from  which  it  soon  becomes  detached  to  gain  the  small 
phalanx  of  the  great  external  digit. 

Lastly,  there  is  in  the  Pig  a  representative  of  the  proper 
extensor  of  the  thumb  and  index,  but  its  tendon — the  thickness 
of  a  thread — is  lost  in  that  of  the  common  extensor  of  the  two 
internal  digits. 

There  is  also  a  round  pronator  along  the  anterior  border  of 
the  internal  ligament  of  the  elbow-joint,  as  well  as  a  short  supi- 
nator. The  latter,  extremely  thin,  has  no  humeral  insertion ;  it  is 
thrown  diagonally  on  the  anterior  and  upper  face  of  the  radius. 

With  regard  to  the  tendon  of  the  lateral  extensor  of  the  pha- 
langes,  or  proper  extensor  of  the  external  digit,  this  spreads  out  on 
the  outer  face  of  that  digit. 

With  regard  to  the  muscles  of  the  posterior  antibrachial  region, 
it  is  remarked  that :  1.  The  anterior  branch  of  the  terminal  tendon 
of  the  external  flexor  of  the   metacarpus  passes  to  the  head  of 
the  outer  metacarpal  bone.     2.  The  internal  flexor  terminates  on 
the  metacarpal  of  the  great  external  digit.     3.  The  perforatus  ia 
formed  by  two  muscular  bodies,  each  terminated  by  a  tendon  in- 
serted, inferiorly,  into  the  second  phalanx  of  one  of  the  great  digits.      4.  The  perforans  is 
divided  into  four  terminal  branches,  which  arrive  at  the  last  phalanx  of  the  great  and  small 
digits. 

The  external  flexor  of  the  metacarpus  is  almost  transformed  into  a  flat  fibrous  cord,  extending 
from  the  epitrochlea  to  the  pisiform  bone,  and  to  the  outer  side  of  the  carpus,  where  it  expands. 
The  oblique  flexor  of  the  metacarpus  is  reduced  to  a  thin  muscular  cord  without  an  ulnar 
insertion. 

The  internal  flexor  of  the  metacarpus,  the  most  developed  of  the  three,  is  inserted  below  on 
the  metacarpal  of  the  small  internal  digit. 

The  muscular  portion  of  the  perforatus  throws  off  a  fasciculus  to  the  perforans,  and  bifurcates 
inferiorly  ;  the  superficial  branch  passes  out  of  the  carpal  slieath,  and  terminates  by  a  tendon, 
in  the  ordinary  manner,  on  the  second  phalanx  of  the  great  external  digit ;  the  deep  branch 


TENDINOUS  AND  LIGAMEN- 
TOUS APPARATUS  OF  THE 
POSTERIOR  FACE  OF  THE 
DIGITAL  REGION  IN  THE 
OX    (POSTERIOR    LIMB). 

1,  Perforatus  tendon ;  2,  2, 
its  terminal  branches  ; 
3,'  3,  their  bifurcation ; 
4,  4,  perforans ;  6,  6,  su- 
perior bands  of  the  in- 
ferior digital  ligament 
attached  to  the  first  pha- 
lanx ;  7,  inferior  inter- 
digital  ligament ;  8,  8, 
suspensory  ligament  of 
the  fetlock. 


MUSCLES  OF  THE  ANTERIOR   LIMBS.  335 

furnishes  a  fasciculus  to  tl,e  perforans,  after  which  it  enters  the  carpal  sheath  with  the  latter, 
ami  terminates  on  the  great  internal  digit. 

The  perforans  presents  an  epitrochlean  portion,  divided  into  two  fasciculi,  between  which 
is  interposed  the  perforatus— an  ulnar  portion  very  like  that  of  the  Horse,  but  inserted  to 
tlie  inner  side  of  the  olecranon ;  and  an  extremely  rudimentary  radial  portion.  These  three 
portions  unite  into  a  common  tendon  which,  on  reaching  the  middle  of  the  metacarpus,  quadri- 
furcates  to  give  a  branch  to  each  of  the  digits ;  the  two  branches  for  the  small  digits  pass 
beneath  a  band  which,  from  the  sesamoid  bones,  is  carried  to  the  inner  side  of  the  second 
plialanx,  and  takes  the  place  of  the  ring  of  the  perforatus. 

Co  Camivora.— In  the  Dog  and  Cat,  the  anttrior  extensor  of  the  metacarpus  divides,  at 

Fig.  187. 


ANTERIOR   ANTIBRACHIAL    REGION   OF   THE   PIG   (EXTERNAL   AND   INTERNAL   FACES). 

1,  Anterior  extensor  of  the  metacarpus ;  2,  oblique  extensor  of  the  metacarpus ;  3,  proper  extensor 
of  the  great  internal  digit ;  3',  its  tendon,  which  gives  off  a  thin  branch  to  the  small  internal 
digit;  4,  proper  extensor  of  the  great  external  digit;  4',  its  tendon;  5,  common  extensor  of  the 
two  internal  digits;  5',  its  tendon  before  bifurcation;  6,  common  extensor  of  the  two  external 
digits ;  6',  its  tendon  before  bifurcation  ;  7,  proper  extensor  of  the  small  external  digit  (lateral 
extensor  of  the  phalanges)  ;  7',  its  tendon. 


its  lower  extremity,  into  two  branches,  which  exactly  resemble  those  of  the  terminal  tendons  of 
the  two  external  radial  muscles  of  Man  :  one  is  inserted  into  the  metacarpus  of  the  index,  the 
other  into  the  metacarpus  of  the  medius  (Fig.  188,  a,  5,  6,  7). 

The  oblique  extejisor  passes  to  the  metacarpus  of  the  thumb ;  it  furnishes,  besides,  a  small 
particular  branch  that  glides,  by  means  of  a  sesamoid,  over  the  third  bone  of  the  inferior  row 
of  the  carpus,  and  is  blended  with  the  posterior  ligament  of  the  carpus  (Fig.  188,  a,  8  ;  B,  4 ; 
D,  8);  it  separates  the  thumb  from  the  other  digits,  but  we  think  it  scarcely  adapted  for  the 
function  of  extensor. 

The  anterior  extensor  of  the  phalanges  of  Solipeds  is  replaced  by  a  single  muscle,  the  com- 
mon extensor  of  the  digits,  terminated  by  a  quadrifurcated  tendon,  whose  branches  are  distributed 
to  the  four  great  digits  (Fig.  188,  a,  9,  9'). 

The  tendon  of  the  lateral  extensor  is  divided  into  three  branches,  which  are  inserted  on  the 
anterior  face  of  the  three  outer  digits,  and  are  blended   with  the  tendons  of  the  common 


336  THE  MUSCLES. 

extensor,  or  with  the  fibrous  bands  furnishecJ  to  tliese  tendons  by  the  interosseous  metacarpal 
muscles. 

The  external  flexor  of  the  metacarpus  comports  itself  as  in  the  Pig.  But  tlie  oblique  flexor 
is  covered  by  the  perfoiatus,  and  its  olecranian  portion,  thicker  than  in  tlie  other  animals,  is 
only  united  to  the  principal  fleshy  body  altogether  inferiorily.  The  internal  flexor  is  slender 
and  conoid  ;  its  tendon,  thin  and  long,  reaches  the  metacarpus  of  the  index. 

The  'perforatum  of  the  Dog  und  Cat  has  a  long,  wide,  and  superficial  body,  separated  from 
the  perforans  by  the  oblique  flexor  of  the  metacarpus.  Its  tendon  passes  outside  the  carpal 
sheath,  and  is  divided  into  four  branches,  attached  by  their  inferior  extremity  to  the  second 
phalanx  of  the  four  principal  digits. 

For  the  perforans,  it  is  noted  : 

1.  That  the  radial  portion  of  the  muscle  (the  long  flexor  of  the  thumb  in  Man)  commences 
towards  the  superior  extremity  of  the  radius  (Fig.  188,  c,  4). 

'2.  That  the  ulnar  division  is  a  semi-penniform  muscle,  attached  by  the  superior  extremities 
of  its  fibres  to  nearly  the  whole  extent  of  the  posterior  face  of  the  ulnar  (Fig.  188,  c,  3). 

3.  That  the  epitrochlean  portion  sends  off,  above  tlie  knee,  a  small  particular  fasciculus 
terminating  in  a  very  thin  tendon,  which  becomes  lost  in  the  fibrous  arch  of  the  carpal  sheath 
(Fig.  188,  c,  6).     This  small  muscle  represents  the  palmaris  brevis  of  Man. 

The  terminal  tendon  divides  into  five  branches,  one  for  each  digit  (Fig.  188,  d,  4,  etc.). 

There  have  been  already  described  in  these  animals : 

1.  Two  external  radial  muscles,  only  distinct  at  their  terminal  extremity,  and  confounded 
for  the  remainder  of  their  extent.  This  is  the  anterior  extensor  of  the  metacarpus  in  Solipeds 
(Fig.  188,  A,  5,  6,  7). 

2.  A  long  abductor  of  the  thumb,  which  appears  to  be  the  representative  of  the  analogous 
muscle,  and  the  short  extensor  of  the  same  digit  in  Man.  It  is  the  oblique  extensor  of  the 
metacarpus  in  the  Horse  (Fig.  188,  a,  8). 

3.  A  common  extensor  of  the  digits ;  the  anterior  extensor  of  the  phalanges  in  the  Horse 
(Fig.  188,  A,  11). 

4.  A  proper  extensor  of  the  three  external  digits,  the  proper  extensor  of  the  little  finger  in 
Man,  or  lateral  extensor  of  the  phalanges  in  the  Horse  (Fig.  188,  a,  10). 

5.  A  posterior  ulnar,  or  external  flexor  of  the  metacarpus  in  the  Horse  (Fig.  188,  a,  13). 

6.  An  anterior  ulnar,  or  oblique  flexor  of  the  metacarpus  in  the  Horse  (Fig.  188,  D,  6). 

7.  A  great  palmar,  corresponding  to  the  internal  flexor  of  the  metacarpus  in  the  Horse 
(Fig.  188,  B,  8). 

8.  A  small  palmar,  a  dependency  of  the  deep  flexor  of  the  phalanges  (Fig.  188,  c,  6). 

9.  A  flexor  suhlimis  of  the  phalanges  (Fig.  188,  D,  1). 

10.  A  deep  flexor  of  the  phalanges  (Fig.  188,  c.  .5 ;  D,  3). 

11.  A  long  flexor  of  the  thumb,  united  to  the  preceding  muscle  (the  radial  portion  of  the 
perforans  (Fig.  18S,  c,  4). 

But  in  Carnivora  there  are  five  additional  museles,  which  are  not  generally  found  in  the 
other  animals.  These  are :  the  proper  extensor  of  the  thumb  and  index,  long  supinator,  short 
supinator,  round  pronator,  and  the  square  pronator.    A  special  description  will  be  given  of  these. 

Muscles  proper  to  the  Forearm  of  Carnivora. 

1.  Proper  Extensor  of  the  Thumb  and  Index  (Fig.  188,  a,  11;  b,  3). 

Synonyms. — The  extensor  secundi  internodii  pnUicis  and  extensor  indicts  of  Man. 

This  is  a  very  small  muscle,  composed  of  a  fleshy  body  and  a  tendon.    The  first  is  thin  and 

fusiform,  and  is  situated  under  the  lateral  extensor;  it  has  its  origin  with  the  oblique  extensor 

of  the  metacarpus  at  the  external  side  of  the  radius.     The  tendon  crosses  the  anterior  aspect  of 

the  knee,  enveloped  by  the  synovial  sheath  of  the  common  extensor  of  the  digits,  under  which 

it  passes.     It  divides  into  two  branches,  one  of  which  goes  to  the  thumb,  the  other  to  the  index.' 

2.  Long  Supinator  (Fig.  188,  a,  12;  c,  8). 

This  muscle  only  exists  in  the  rudimentaiy  state  in  Carnivora.  Its  existence  in  the  Dog 
has  even  been  denied,  but  this  is  an  error;  our  researches  have  demonstrated  that  it  is  present, 
in  a  more  or  less  evident  manner,  in  all  breeds. 

It  is  a  very  delicate  baud,  situated  in  front,  and  on  the  inner  side  of  the  anterior  extensor 


'  In  very  powerful  Horses,  and  more  frequently  in  the  Ox,  we  have  met  with  traces  of  this 
muscle  in  the  form  of  a  deep  fasciculus  situated  in  front  of  the  lateral  extensor. 


MUSCLES  OF  THE  ANTERIOR  LIMBS. 

Fig.  188. 
B  C. 


337 


MUSCLES  OF  THE  FOREARM  AND  PAW  OF  THE  DOG. 

i.  Anterior  superficial  region.— 1,  Short  flexor  of  the  forearm  (iinterior  brachial) ;  2,  long  flexor  of 
the  forearm  (brachial  biceps)  ;  3,  anconeus ;  4,  round  pronator  ;  5,  anterior  extensor  of  the 
metacarpus  (external  radial)  ;  6,  its  tendon  of  insertion,  destined  for  the  lourth  metacarpal  l.one  ; 

7,  that  which  goes  to  the  third  ;  8,  external  oblique  of  the  metacarpus  (long  abductor  and  short 
extensor  of  the  thumb);  9,  common  extensor  of  the  digits;  9',  its  terminal  tendon  at  the  point 
where  it  divides  into  four  branches  ;  10,  proper  extensor  of  the  three  external  digits,  or  lateral 
extensor  of  the  phalanges  in  the  horse  ;  10',  its  terminal  tendon  at  the  commencement  of  its 
trifurcation  ;  11,  proper  extensor  of  the  thumb  and  index;  11',  its  terminal  tendon;  12,  12,  long 
supinator  ;   13,  external  flexor  of  the  metacarpus  (posterior  ulnar). 

B.  Deep  anterior  region.— I,  Round  pronator ;  2,  short  supinator  ;  3,  proper  extensor  of  the  thumb 
and  index  ;  4,  oblique  extensor  of  the  metacarpus  ;  5,  superior  insertion  of  the  anterior  extensor 
of  the  metacarpus  ;  6,  ditto  of  the  anterior  extensor  of  the  phalanges  ;  7,  proper  extensor  of  the 
three  external  digits;  8,  internal  flexor  of  the  metacarpus  (great  palmar);  9,  levator  humeri; 
10,  11,  long  and  short  flexors  of  the  forearm. 

C.  Deep  posterior  region. — 1,  Round  pronator  ;  2,  square  pronator ;  3,  ulnar  portion  of  the  perforans  ; 

4,  radial  portion  of  the  same  (long  flexor  of  the  thumb)  ;  5,  terminal  tendon  of  the  same;  6, 
tendon  of  the  small  palmar  (division  of  the  perforans)  ;  7,  anterior  extensor  of  the  metacarpus  ; 

8,  long  supinator  ;  9,  epicondyloid  insertion  of  the  perforatus,  perforans,  and  oblique  and  internal 
flexors  of  the  metacarpus;  10,  olecranian  insertion  of  the  oblique  flexor;  11,  supercarpal  inser- 
tion of  the  same;  12,  terminal  tendon  of  the  internal  flexor  ;  13,  proper  extensor  of  the  external 
digits  ;  14,  coraco-radialis  ;   15,  tendon  of  the  extensors  of  the  forearm. 

D.  Superficial  posterior  region,  and  the  special  muscles  of  the  foot  or  hand. — 1,  Perforatus;  1',  its 
tendon  divided  at  its  passage  behind  the  carpal  sheath;  2.  ditto,  its  terminal  branches;  3,  per- 
forans ;  3',  its  tendon  divided  after  its  exit  from  the  carpal  sheath  ;  4,  ditto,  its  terminal  branches  ; 

5,  tendon  of  the  internal  flexor  of  the  metacarpus  ;  6,  oblique  flexor  (anterior  ulnar) ;  7,  inferior 
extremity  of  the  long  supinator;  8,  terminal  tendon  of  the  oblique  extensor  of  the  metacarpus; 

9,  short  abductor  of  the  thumb;  10,  opponent  of  the  thumb;  11,  short  flexor  of  the  thumb; 
12,  adductor  of  the  thumb,  transformed,  in  the  dos,  into  the  adductor  of  the  index  ;  13,  short 
flexor  of  the  small  digit;  14.  adductor  of  the  small  digit;  15,  opponent  of  the  small  digit; 
16,  16  metacarpal  interosseous  muscles,  a,  a,  a.  Bands  which  maintain  the  flexor  tendons  on 
the  metacarpo-phalangean  articulations,  and  limit  the  separation  of  the  digits;  collectively,  they 
represent,  in  a  rudimentary  state,  the  palmar  aponeurosis  of  Man. 


338  THE  MUSCLES.  ' 

of  the  metacarpus,  taking  its  origin,  along  with  that  muscle,  from  the  crest  limiting  the 
musculo-spiral  groove  of  the  humerus,  behind  the  ridge ;  and  terminating  within  the  inferior 
extremity  of  the  radius  by  fleshy  and  aponeurotic  fibres.  This  small  muscle  can  have  but  a 
very  limited  influence  on  the  movements  of  the  bones  of  the  forearm,  because  of  its  trifling 
volume.     As  its  name  indicates,  it  acts  in  supination. 

3.  Short  Supinator  (Fig.  188,  b,  2). 
A  triangular  and  slightly  divergent  muscle,  covered  by  the  anterior  extensor  of  the  meta- 
carpus and  the  common  extensor  of  the  digits.  It  has  its  origin  in  the  soiall  fossa  situated 
outside  tlie  humeral  trochlea,  by  a  flat  tendon  which  is  confounded  with  the  external  lateral 
ligament  of  the  elbow-joint.  It  terminates  above  the  anterior  face  and  the  inner  side  of  the 
radius,  by  the  inferior  extremities  of  its  fleshy  fibres.  Covered  by  the  two  preceding  muscles, 
it  covers  the  elbow  articulation  and  the  bone  receiving  its  insertion.  It  ought  to  be  considered, 
in  Carnivora,  as  the  principal  supinator;  it  pivots  the  radius  on  the  ulna,  so  as  to  turn  the 
anterior  face  of  the  first  bone  outwards. 

4.  Round  Pronator  (Fig.  188,  b,  1 ;  c,  1). 
Situated  on  the  inner  and  upper  part  of  the  forearm,  between  the  great  palmar  or  internal 
flexor  of  the  metacarpus  and  the  mterior  extensor  of  the  same  ray,  the  round  pronator  is  a 
thick  and  short  muscle,  which  originates  on  the  small,  epicondyloid  tuberosity  of  the  humerus, 
and  terminates  at  the  internal  side  of  the  radius  by  aponeurotic  fibres. 

5.  Square  Pronator  (Fig.  188,  o,  2). 
This  muscle  is  situated  immediately  behind  the  bones  of  the  forearm,  beneath  tlie  muscular 
masses  of  the  posterior  antibrachial  region.  It  extends  from  the  insertion  of  the  flexors  of  the 
forearm  to  near  the  carpus,  and  is  formed  of  transverse  fibres  which  pass  directly  from  the 
ulna  to  the  radius.  It  is,  then,  no  longer,  as  in  Man,  a  square  muscle  attached  only  to 
the  lower  fourth  of  these  two  bones.  The  two  pronators  are  antagonists  of  the  short  supinator, 
turning  forwards  the  anterior  face  of  the  radius  and  metacarpus. 

Comparison  of  the  Muscles  of  the  Forearm  of  Man  with  those  of  Animals. 

All  the  muscles  of  the  forearm  of  Man  are  more  or  less  perfectly  represented  in  the  forearm 
of  Carnivora. 

In  Man,  these  muscles  are  described  in  placing  the  forearm  in  a  state  of  supination,  and 
are  divided  into  three  regions :  anterior,  external,  and  posterior. 

1.  Anterior  Region. 
This  comprises  eight  muscles  : 

1.  The  round  pronator,  absent  in  animals  except  the  Carnivora.  This  muscle  forms  the 
internal  oblique  prominence  in  the  bend  of  the  elbow.  It  leaves  the  epitrochlea  and  the 
coronoid  process  of  the  ulna,  terminating  on  the  middle  third  of  the  external  face  of  the  radius. 

2.  The  great  palmaris,  which  corresponds  to  the  internal  flexor  of  the  metacarpus  of  the 
Horse.  Situated  within  the  preceding,  it  is  attached,  above,  to  the  epitrochlea ;  below,  to  the 
base  of  the  second  metacarpal.     It  is  more  especially  a  flexor  of  the  hand. 

3.  The  small  palmaris,  the  presence  of  which  is  not  constant,  and  is  represented  in  the  Dog 
by  a  portion  of  the  deep  flexor  of  the  phalanges. 

4.  The  superficial  flexor  or  perforatus  has  two  planes  of  muscular  fibres.  The  superficial 
plane  is  destined  to  the  tendons  of  the  medius  and  annularis ;  the  deep  plane  to  the  tendons 
of  the  index  and  little  finger.  These  tendons  are  fixed  into  the  secondary  phalanges  of  the 
above-named  digits. 

5.  The  anterior  ulnar  resembles  the  oblique  flexor  of  the  metacarpus  of  the  Horse.  It  is 
inserted,  above,  into  the  epitrochlea  and  the  olecranon;  below,  in  the  pisiform  bone.  Its 
action  is  transmitted,  by  a  fibrous  band,  from  this  bone  to  the  fifth  metacarpal.  It  flexes  the 
hand  by  inclinin";  it  inwards. 

6.  The  deep  flexor  or  perforans  is  resolved  into  two  fasciculi :  one,  the  internal,  for  the  little 
finger,  the  annularis,  and  the  medius;  the  other,  the  external,  for  the  index.  The  three  first 
tendons  are  at  first  united  to  each  other  by  fibrous  bands,  and  together  pass  through  a  sheath 
formed  by  the  perforatus. 

7.  The  proper  flexor  of  the  thumb,  represented  in  the  Dog  by  the  radial  portion  of  the 
perforans.  It  is  attached,  for  one  part,  to  the  upper  three-fourths  of  the  anterior  face  of  the 
radius,  the  interosseous  aponeurosis,  and  the  coronoid  process  of  the  ulna ;  on  the  other  part, 
to  the  second  phalanx  of  the  thumb. 


MUSCLES  OF  THE  ANTERIOR  LIMBS. 


8.  The  square  pronator,  a  thick,  quadrilateral  muscle  with  transverse  fibres,  situated  at  the 
deep  and  inferior  portion  of  the  forearm.  This  muscle  in  the  Dog  is  much  more  extensive  in 
length. 

2.  External  Region. 

The  muscles  of  this  region  are  four  in  number,  two  of  which,  the  supinators,  are  only 
represented  in  Carnivorous  animals : — 

I.  The  long  supinator  forms  a  prominent  mass  at  the  bend  of  the  elbow.    It  is  attached  to 


Fig.  189. 


Fig.  190. 


BCPEBFICIAL  MUSCLES  OF   HUMAN    FOREARM. 

1,  Biceps,  with  its  tendon ;  2,  Vjrachialis  an- 
ticus  ;  3,  triceps  ;  4,  pronator  radii  teres  ; 
5,  flexor  carpi  radialis ;  6,  palmavis  lon- 
gus ;  7,  a  fasciculus  of  flexor  sublirais 
digitorum ;  8,  flexor  carpi  ulnaris;  9, 
palmar  fascia;  10,  palmans  brevis ;  11, 
abductor  pollicis;  12,  flexor  brevis  pol- 
licis ;  13,  supinator  longus ;  14,  extensor 
ossis  metacarpi,  and  extensor  primi  inter- 
nodii  pollicis. 


DEEP   LAYER   OF    SUPERFICIAL    MUSCLES    OF 
HUMAN    FOREARM. 

1,  Internal  lateral  ligament  of  elbow-joint ; 
2,  anterior  ligament ;  3,  orbicular  ligament 
of  radius  ;  4,  flexor  profundus  digitorum  ; 
5,  flexor  longus  pollicis  ;  6,  pronator  quad- 
ratus ;  7,  adductor  pollicis ;  8,  dorsal  in- 
terosseous of  middle,  and  palmar  inter- 
osseous of  rmg,  finger ;  9,  dorsal  inter- 
osseous muscle  of  ring-finger,  and  palmar 
interosseous  of  little  finger. 


the  inferior  third  of  the  external  border  of  the  humerus,  and  to  the  base  of  the  styloid  procesB 
of  the  radius.     It  is  a  flexor  of  the  forearm,  not  a  supinator,  as  its  name  indicates. 

2.  The  first  external  radial  is  represented  by  a  portion  of  the  anterior  extensor  of  the 
metacarpus  of  animals.  It  commences  at  the  inferior  part  of  the  external  border  of  the  humerus, 
and  terminates  at  the  posterior  part  of  the  base  of  the  second  metacarpal. 

3.  The  second  external  radial,  also  represented  by  a  portion  of  the  anterior  extensor  of  the 
metacarpus,  terminates  at  the  base  of  the  third  metacarpal. 

4.  The  short  supinator,  a  muscle  bending  round  the  upper  third  of  the  radius,  is  the 
essential  agent  in  supination. 


340  THE  MUSCLES. 

3.  Posterior  Region. 
The  muscles  of  this  region,  divi8il)le  into  two  layers,  are:— 

1.  Tiie  common  extensor  of  the  digits— &\denoT  extensor  of  the  phalanges  of  the  Horse — 
divided  iiito  four  tendinous  branches  which  pass  to  all  the  fingers,  except  the  thumb. 

2.  The  proper  extensor  of  the  little  finger,  whose  tendon  is  joined  to  the  brancli  of  the 
common  exlen^or  tliat  passes  to  the  auricularis — the  lateral  extensor  of  animals. 

3.  The  posterior  ulnar,  corresponding  to  the  external  iiexor  of  the  metacarpus  of  tiie  Horse. 
It  goes  to  the  epicondyle  at  the  upper  extremity  of  the  fifth  metacarpal. 

4.  Tiie  long  abductor  of  the  thumb,  resembling  a  portion  of  the  oblique  extensor  of  the 
metacarpus  of  animals.  This  muscle  is  attached  to  the  posterior  face  of  the  ulna  and  radius, 
and  the  upper  extremity  of  the  first  metacarpal. 

5.  The  short  extensor  of  the  thumb,  which  is  also  represented  in  animals  by  a  portion  of  the 
oblique  extensor  of  the  metacarpus. 

6.  The  long  extensor  of  the  thumb,  arising  from  the  ulna,  and  inserted  into  the  second 
phalanx  of  the  thumb.  This  muscle  limits,  inwardly,  the  excavation  termed  the  anatomical 
snuff-hox. 

7.  Tiie  proper  extensor  of  the  index,  whose  tendon  is  confounded  with  the  branch  of  the 
common  extencor  passing  to  this  digit. 

These  two  latter  muscles,  blended  in  the  Dog,  exist  only  in  a  rudimentary  state  in  the 
other  animals. 

We  will  say  nothing  of  the  anconeus,  placed  in  the  antibrachial  region  by  anthropotomists, 
and  which  has  been  described  in  the  posterior  brachial  region. 

Muscles  of  the  Anterior  Foot  or  Hand 
These  will  be  studied  successively  in  Carnivora,  the  Pig,  Solipeds,  and  Ruminants. 

A.  Muscles  of  the  Anterior  Foot  or  Hand  of  Carnivora. 
All  the  muscles  of  the  human  hand  are  found  in  that  of  Carnivora,  tome  perfectly  developed, 
others  quite  rudimentary.  These  muscles  are:  1.  The  short  abductor  of  the  thumb.  2.  The 
opponent  of  the  thumb.  H.  The  short  flexor  of  the  thumb.  4.  An  adductor  of  the  index— adductor 
of  the  thumb  in  Man.  5.  The  cutaneous  palmar.  6.  The  adductor  of  the  small  digit.  7.  The 
short  flexor  of  the  small  digit.  S.  The  opponent  of  the  small  digit.  9.  The  thvee  lumbr id.  10. 
Four  interosseous  metacarpals. 

1.  Short  Abductor  of  the  Thumb  (Fig.  188,  d,  9). 
This  is  rudimentary,  like  the  digit  it  is  intended  to  move,  and  is  situated  behind  the 
metacarpal  bone  of  the  thumb ;  it  is  composed  of  very  pale  fleshy  fasciculi,  which  are  continued 
inferiorly  by  some  tendinous  fibres.  It  has  its  origin  at  the  carpal  arch,  and  terminates  on  the 
metacarpal  bone  of  the  thumb,  as  well  as  at  the  external  side  of  the  superior  extremity  '  of  the 
first  phalanx.     It  is  a  flexor  and  abductor  of  the  thumb. 

2.  Opponent  op  the  Thumb  (Fig.  188,  d,  10). 
This  vestige  of  the  thick  short  muscle  which  bears  the  same  name  in  Man  is  situated 
beneath  and  within  the  preceding,  in  a  slightly  oblique  direction  downwards  and  outwards. 
Pale  and  almost  entirely  muscular,  it  is  attached  to  the  posterior  ligament  of  the  carpus  and 
the  metacarpal  bone  of  the  thumb.  Owing  to  the  conformation  of  this  digit  in  Carnivora,  this 
muscle  cannot  act  as  it  does  in  Man  in  producing  the  opposition  of  the  thumb  ;  it  only  draws 
it  towards  the  axis  of  the  hand,  and  is  therefore  merely  an  adductor  of  the  thumb. 

3.  Short  Flexor  of  the  Thumb  (Fi^'.  188,  d,  11). 
A  very  small  muscle,  deeper  in  colour  than  the  other  two,  and  situated  between  them,  the 
adductor  of  the  index,  and  the  fourth  interosseous  muscle.   It  is  fixed,  by  its  superior  extremity, 
in  the  mass  of  the  posterior  carpal  ligament,  and  attached,  below,  to  the  internal  side  of  the 
first  phalanx.     It  is  a  somewhat  extensive  flexor  of  the  thumb. 

4.  Adductor  op  the  Index  (Fig.  188,  d,  12). 
Synonym.— The  adductor  of  the  thumb  in  Man. 
Elongated,  prismatic,  compressed  on  each  side,  included  between  the  third   and   fourth 

'  It  is  necessary  to  remember  that  the  position  of  the  digits  is  considered  in  relation  to  the 
axis  of  the  hand— that  is,  the  median  line  separating  the  medius  from  the  annularis. 


MUSCLES  OF  THE  ANTERIOR  LIMBS.  341 

interosseous  muscles,  and  concealed  by  tlie  tendinous  portion  of  the  common  flexor  of  the 
digits,  this  muscle  is  attached,  superiorly,  to  the  posterior  carpal  ligament  with  the  third 
interosseous  muscle.  It  is  fixed,  inferiorly,  by  means  of  a  small  flattened  tendon,  along  the 
superior  and  internal  side  of  the  first  phalanx  of  the  index.  It  is  regarded  as  the  adductor  of 
the  thumb  in  Man  transformed  into  an  adductor  of  the  index,  in  consequence  of  the  atrophy  of 
the  fifth  digit. 

5.  Cutaneous  Palmar  (Palmaris  Brevis). 

A  thick,  hemispherical,  musculo-adipose  body,  forming  the  base  of  the  exterior  tubercle 
placed  behind  the  carpus.  It  adheres  intimately  to  the  skin  by  its  superficial  face,  and  deeply 
to  the  aponeurosis  covering  the  muscles  of  the  hand. 

6.  Adductor  of  the  Small  Digit  (Fig.  188,  d,  14). 

This  muscle  is  superficially  situated,  external  to,  and  behind  the  outer  metacarpal  bone,  and 
is  composed  of  a  thick,  conical  fleshy  body,  concave  on  its  anterior  surface,  convex  posteriorly, 
and  of  a  long,  thin,  and  flat  tendon,  which  succeeds  tlie  inferior  extremity  of  the  muscular 
portion. 

It  is  attached,  by  the  superior  extremity  of  the  latter,  to  the  pisiform  bone;  the  tendon 
terminates  out»i  le  the  superior  extremity  of  tiie  first  phalanx  of  the  small  digit. 

This  muscle  separates  that  digit  from  the  axis  of  the  hand,  and  is  therefore  an  abductor 
and  not  an  adductor,  as  its  name  would  indicate.  That  name  has  been  given  to  it  in  Man, 
because  the  hand  has  been  considered  in  a  state  of  supination,  a  position  in  which  it  is 
effectively  an  adductor  in  regard  to  the  median  plane  of  the  body.  If  this  name  has  been 
preserved  here,  it  is  owing  to  a  desire  not  to  import  any  new  element  of  confusion  into  a 
nomenclature  already  too  complicated. 

7.  Short  Flexor  of  the  Small  Digit  (Fig.  188,  d,  13). 

Situated  within  the  preceding,  in  a  slightly  oblique  direction  downwards  and  outwards, 
flattened  before  and  behind,  triangular,  and  almost  entirely  muscular,  this  muscle  derives  its 
origin  from  a  ligament  which  unites  the  pisiform  bone  to  the  metacarpal  region,  and  terminates 
inferiorly  on  the  tendon  of  the  adductor,  whose  congener  it  is.  It  may  also  concur  in  the 
flexion  of  the  small  digit,  though  to  a  very  limited  degree. 

8.  Opponent  of  the  Small  Digit  (Fig.  188,  d,  15). 

A  muscle  elongated  from  above  downwards,  flattened  before  and  behind,  situated  under  the 
perforans  tendons,  behind  the  second  interosseous  muscle,  in  a  direction  sliglitly  downwards 
and  outwards.  It  originates  from  the  posterior  ligament  of  the  carpus,  and  terminates  within 
the  superior  extremity  of  the  first  phalanx  of  the  external  digit  by  a  small  tendon.  It  acts  as 
an  adductor  by  drawing  the  small  digit  towards  the  axis  of  the  hand. 

9.  LuMBRicr. 

These  small  muscles,  which  owe  their  name  to  the  resemblance  they  bear  to  the  lumbricales 
or  earthworms,  are  only  three  in  number  in  Carnivora.  They  occupy  the  interval  between  the 
four  chief  branches  of  the  perforans  tendon,  from  which  they  have  their  origin  ;  they  terminate, 
by  a  small  fibrous  digitation,  on  the  extensor  tendons  of  the  three  external  digits.  It  is  often 
impossible  to  trace  them  so  far ;  for  they  are  frequently  observed  to  stop  within  and  above  the 
first  phalanx  of  tlie  digits  for  which  they  are  destined.  Their  functions  cannot  be  rigorously 
defined  in  Carnivora. 

10.  Metacabpa    Interosseous  Muscles  (Fig.  188,  d,  16,  16). 

These  are  four  thick  and  prismatic  muscular  fasciculi,  elongated  from  above  to  below, 
bifid  at  their  inferior  extremity,  placed  parallel  to  one  another,  in  front  of  the  flexor 
tendons,  from  which  they  are  separated  by  a  thin  aponeurotic  layer,  and  behind  the  four  large 
metacarpals. 

They  have  their  origin  on  the  posterior  and  lateral  faces  of  these  bones,  as  well  as  on  the 
posterior  carpal  and  intermetacarpal  lis;aments.  Each  terminates,  by  the  two  branches  of  its 
inferior  extremity,  on  the  great  sesamoids  of  the  digit  to  which  it  corresponds.  There  they  are 
continued  by  a  small  tendon,  which  joins  the  chief  extensor  of  the  digit.  These  muscles 
oppose  undue  extension  of  the  digits  while  the  animal  is  standing,  flex  them  on  the  metacarpal 
bones,  and  maintain  the  extt-nsor  tendons  on  the  anterior  aspect  of  the  plialanges. 


342 


THE  MUSCLES. 


B.  Muscles  of  the  Anterior  Foot  in  the  Pig. 
In  our  notes  on  the  myology  of  this  animal,  we  find  : 

1.  A  muscle  which  originates  in  tlie  substance  of  the  metacarpo-supercarpal  ligament,  and 
tenuiuates  on  tlie  proper  extensor  of  the  small  external  digit  by  a  librous  strip  joined  to  the 
external  fasciculus  of  the  first  interosseous  muscle;  it  is  also  attached  to  the  external  sesamoid. 
This  is,  no  doubt,  the  representative  of  the  short  flexor  of  the  small  digit  ia  Man  and  the 
Caniivora, 

2.  A  single,  but  very  voluminous  lumhricus,  fixed,  at  the  one  part,  to  the  perforans  tendon, 
and  at  the  other,  to  the  proper  extensor  tendon  of  tlie  small  internal  digit  (index),  as  in  the 
preceding  muscle. 

3.  Four  interosseous  metacarpal  muscles,  similar  to  those  in  the  Dog,  and  whose  terminal 
digitations  join  the  proper  extensor  tendons.     The  interosseous  muscles  of  the  two  small  digits 

are  not  only  divided  at  their  inferior  extremity,  but 
Fig.  191.  throughout  their  whole  length  are  observed  to  be  two 

veij-  distinct  fasciculi,  one  superficial  and  external,  the 
other  deep  and  internal.  The  fibrous  membraue  cover- 
ing these  muscles,  and  which  separates  them  from 
the  perforans  tendons,  is  much  thicker  than  in  the 
Carnivora. 

C.  Muscles  of  the  Anterior  Foot  in 

SOLIPEDS. 

In  Solipeds,  only  two  liimbrici  and  two 
interosseous  metacarpal  muscles  have  to  be 
described. 

1.  The  lumhrici  originate  at  the  right  and 
the  left  of  the  perforans  tendon,  above  the 
sesamoid  annular  band  of  the  perforatus.  They 
each  terminate  by  a  thin  tendon,  which  is  lost 
in  the  fibrous  layer  enveloping  the  elastic 
cushion  of  the  ergot  of  the  fetlock. 

2.  The  interosseous  muscles  {anterior  lum- 
hrici— PercivaU)  have  been  wrongly  considered 
by  French  veterinary  anatomists  as  lumbrici 
muscles,  and  are  described  by  them  as  the 
superior,  or  great  lumhrici.  Situated  within  the 
rudimentary  metacarpal  bones,  these  two  little 
muscles  are  formed  of  a  very  delicate  fleshy 
mass  embedded  in  the  fibrous  tissue  surround- 
ing the  head  of  the  metacarpal  bones,  and  of 
a  long  tendon  which  descends  to  the  metacarpo- 
phalangeal articulation,  to  be  confounded  with 
the  band  furnished  to  the  anterior  extensor  of 
the    phalanges   by   the   suspensory   ligament. 

Sometimes  this  tendon  is  directly  united  to  one  of  the  extensors  of  the  phalanges. 
These  two  muscles  represent  the  interossei  of  the  lateral  digits.     With  regard 
to  those  of  the  median  digit,  they  are  transformed,  as  we  have  already  seen,  into 
a  fibrous  brace  which  constitutes  the  suspensory  ligament  of  the  fetlock. 

D.  Muscles  op  the  Anterior  Foot  in  Ruminants. 
These  animals  have  no  muscles,  properly  speaking,  in  the  region  of  the  foot ;  in  fact,  we  only 
find  in  them  the  suspensory  ligament  of  the  fetlock,  which  is  the  interosseous  of  the  two 
complete  digits. 

Comparison  of  the  Hand  of  Man  with  that  op  Animals. 
The  muscles  of  Man's  liand  are  numerous  and  well-developed,  in  consequence  of  the  extent 


MUSCLES  OF   human    HAND. 

,  Annular  ligament;  2,  2,  origin  and 
insertion  of  the  abductor  pollicis 
muscle ;  3,  flexor  ossis  metacarpi,  or 
opponens  pollicis ;  5,  deep  portion  of 
flexor  brevis  pollicis;  6,  adductor 
pollicis ;  7,  7,  lumbricales  muscles 
arising  from  the  deep  flexor  tendons, 
upon  which  the  figures  are  placed ; 
8,  a  tendon  of  deep  flexor ;  9,  tendon 
of  flexor  longus  pollicis ;  10,  abductor 
minimi  digitii  ;  11,  flexor  brevis 
minimi  digitii;  12,  pisiform  bone; 
13,  first  dorsal  interosseous  muscle, 
the  abductor  indicis. 


MUSCLES  OF  THE  POSTERIOR  LIMBS.  343 

and  variety  of  the  movements  of  its  various  parts.  They  are  divided  into  three  groups :  the 
external,  or  group  of  the  thenar  eminence,  induce  the  movements  of  the  thumb;  the  internal, 
or  group  of  the  hypothenar  eminence,  those  of  the  little  finger ;  and  the  middle  group,  occupy' 
ing  the  metacarpal  spaces,  comprising  the  interosseous  muscles.  In  addition,  there  is  found  in 
the  hand  a  cuticularis  muscle,  the  cutaneous  palmaris  (palmaris  hrevis). 

The  cutaneous  palmaris  occupies  two-thirds  of  the  hypothenar  eminence;  its  fibres  are 
directed  downwards  and  inwards.     It  corrugates  the  skin  on  the  ulnar  border  of  the  hand. 

A.  Muscles  of  the  Thenar  Eminence. 
The.>e  muscles,  nearly  all  present  in  the  Dog,  are  : 

1.  The  short  adductor  of  the  thumb,  whose  fibres,  leaving  the  lower  portion  of  the  anti- 
brachial  aponeurosis,  the  process  of  the  trapezius  and  the  scaphoides,  are  succeeded  by  a 
tendon  which  is  inserted  into  tiie  upper  extremity  of  the  first  phalanx  of  the  thumb. 

2.  The  opponent  (opponens)  of  the  thumb,  which  passes  from  the  anterior  part  of  the 
trapezium  to  the  external  border,  and  near  the  anterior  face  oi'  the  first  metacarpal. 

3.  The  short  flexor  of  the  thumb,  a  muscle  adjoining  the  preceding,  and  which  ia  resolved 
into  two  series  of  fibres— a  deep  and  a  superficial. 

4.  The  short  adductor  of  the  thumb,  a  triangular  muscle,  occupying  the  outer  half  of  the 
hollow  of  the  palm.  It  is  attached  to  the  os  magnum,  along  the  entire  length  of  the  third 
metacarpal  bone  and,  by  a  tendon,  to  the  sesamoid  and  supero-internal  tuberosity  of  the  first 
phalanx  of  the  thumb. 

B.  Muscles  of  the  Hypothenar  Eminence. 
These  muscles  are  :  1.  The  abductor  of  the  little  finger,  a  small  fusiform  muscular  body,  which 
is  attached,  above,  to  the  pisiform  bone,  and  below  to  the  supero-internal  part  of  the  first  phalanx. 

2.  The  short  flexor  of  the  little  finger,  situated  without  the  preceding,  fixed  in  one  part  to 
the  process  of  the  unciform  bont ,  and  in  the  other  to  the  inner  part  of  the  first  phalanx. 

3.  The  opponent  (opponens)  of  the  little  finger,  a  triangular  muscle,  situated  below  the 
preceding.  It  is  inserted  into  the  process  of  the  unciform  bone,  then  into  the  inner  border  of 
the  fifth  metacarpal  and  the  adjacent  portion  of  its  anterior  face. 

C.  Interosseous  Muscles. 

"  The  interosseous  muscles  are  situated  in  each  interosseous  space,  two  for  each  space,  and 
are  divided  into  dorsal  and  palmar.  As  there  are  four  interosseous  spaces,  there  ought  to  be 
eight  muscles;  but  it  is  usual  to  exclude  the  short  adductor  of  the  thumb,  because  (if  its 
special  insertions ;  this  reduces  the  total  number  of  interosseous  muscles  to  seven — four  dorsal 
and  three  palmar. 

"These  small  muscles  arise  from  the  lateral  faces  of  the  metacarpals  to  the  lateral  and 
upper  portions  of  the  first  phalanges.  By  their  contraction,  they  incline  these  phalanges 
laterally,  and  consequently  carry  the  corresponding  digit  inwards  and  outwards." 

It  may  be  added  that  the  lumbrici  muscles  are  small  muscular  and  tendinous  fasciculi, 
annexed  to  the  tendons  of  the  deep  flexor  of  the  phalanges ;  their  tendons  terminate  on  the 
external  side  of  the  four  last  digits,  in  becoming  blended  with  the  interossei. 

Article  III. — Muscles  of  the  Posterior  Limbs. 
These  form  four  principal  groups  :  the  muscles  of  the  croup,  thigh,  leg,  and  foot. 
Muscles  of  the  Gluteal  Region,  or  Croup. 

This  region  is  composed  of  three  superposed  muscles,  which  are  applied 
to  the  ilium,  and  are  distinguished  according  to  their  relative  situation  as  the 
suf)erficial,  middle,  and  deep  gluteus.'^ 

They  are  covered  by  a  thick  fibrous  fascia — a  prolongation  of  the  aponeurosis 
of  the  great  dorsal — which  is  continued  backwards  over  the  muscles  of  the 
posterior  crural  region,  where  it  is  confounded  with  the  superficial  layer  of  the 
fascia  lata.  This  gluteal  apotieurosis  is  fixed  to  the  external  angle  of  the  ilium 
and  the  supersacral  spine.  By  its  deep  face  it  gives  attachment  to  several 
fasciculi  of  the  superficial  and  middle  glutei. 

'  For  the  justification  of  the  employment  of  these  new  denominations,  see  note,  p.  230 


344 


TEE  MUSCLES. 


Preparation. — 1.  Place  the  animal  on  its  side,  or,  better,  in  the  second  position.  2.  Remove 
the  skin  from  this  region  in  order  to  show  the  gluteal  apoueurosis,  and  to  study  its  extent, 
attachments,  and  relations.  3.  Cut  away  this  aponeurosis  to  expose  the  anterior  point  of  the 
middle  gluteus 'and  the  muscular  portion  of  the  superticial.  To  prepare  the  apoueurotic 
portion  of  the  latter  muscle,  the  sacro-sciatic  insertion  of  the  long  vastus  must  be  detached  by 
the  scalpel  and  thrown  downwards.  4.  Incise  the  superficial  gluteus  near  its  femoral  insertion, 
and  reverse  it  on  the  sacral  spine,  so  as  to  lay  bare  the  external  face  of  the  middle  or  principal 
^duteus.  5.  Divide  this  muscle  near  its  femoral  insertions,  taking  care  not  to  inj  ure  these,  and 
remove  the  whole  of  its  mass,  studying  raeanwhUe  the  nature  of  its  relations  to  the  parts 
it  covers;  the  deep  or  small  gluteus  then  becomes  apparent,  and  may  be  conveniently 
examined. 

To  render  the  dissection  and  study  of  these  muscles  easier,  the  hind  quarters  may  be 
arranged  as  in  Fig.  192.  A  special  upright  support  passes  between  the  last  ribs,  and  a 
horizontal   lever  maintains  the  lumbar  region  fixed  in  a  kind  of  metallic  fork.      By  this 

arrangement  the  croup  and  hips  are 
Fjg.  192.  kept  in  a  good  direction,  the  mass 

I/,    ^  ^  C  I  being  made  tense,  so  that  they  can 

be  dissected  nearly  in  their  normal 
relations. 

1.  SupEEFiciAL  Gluteus 
(Gluteus  Exteenus) 
(Fig.  193,  2,  4). 

Synonyms.  —  Ilio-trochanterius 
medius — Girard.  Gluteus  minor 
— Boxirgelat.  Gluteus  medius — 
Rigot  and  Lafosse.  The  gluteus 
magnus  of  Man.  (^Ilio-trochanterius 
externus — Leyh.) 

Coinposition —  Situation . — 
This  muscle  is  composed  of 
two  portions— one  anterior, 
the  other  posterior,  closely 
joined,  and  situated  beneath 
the  gluteal  fascia.  They  form 
the  most  superficial  portion  of 
the  fleshy  masses  of  the  croup 
and  inner  face  of  the  thigh. 

Form — Structure —  Attach- 
ments.— A.  The  anterior  'por- 
tion (the  mperflcial  or  middle 
gluteal  muscle  of  veterinary  anatomists)  comprises  a  muscular  and  an  aponeu- 
rotic division.  The  first  is  triangular  in  shape,  deeply  notched  in  its  upper 
border,  so  that  it  is  sometimes  divided  into  two  parts — an  external  and  an 
internal.  Its  fasciculi  are  very  thick  and  loosely  united  ;  they  all  pass  back- 
wards and  downwards,  to  converge  in  a  flattened  tendon  which  terminates  the 
inferior  angle  of  the  muscle.  The  aponeurosis,  also  triangular,  is  confounded 
in  front  with  the  posterior  border  of  the  muscular  portion  and  its  terminal 
tendon,  and  is  insinuated  behind,  beneath  the  posterior  portion  ;  it  degenerates 
into  connective  tissue  at  its  inner  and  upper  border.  The  anterior  part  of  the 
muscle  has  it?,  fixed  insertion  :  1.  On  the  internal  aspect  of  the  gluteal  aponeu- 
rosis, by  the  superior  extremity  of  its  muscular  fasciculi.  2.  On  the  postero- 
external angle  of  the  ischium,  and  the  sciatic  ligament,  by  the  internal  border 
of  its  aponeurotic  portion.  It  has  its  movable  insertion,  by  means  of  its  terminal 
tendon,  on  the  small  external  or  third  trochanter  of  the  femur. 


T,  Table ;  A,  showing  the  principal  support ;  B,  posterior 
horizontal  bar ;  C,  blunt  point  at  the  end  of  the  branches 
of  the  T  placed  at  the  extremity  of  the  posterior  branch; 
D,  anterior  horizontal  branch  terminated  by  vertical 
branches,  E,  on  which  the  last  pair  of  ribs  rest ;  L, 
notched  lever  which  keeps  the  animals  hind  quarters  on 
the  support  ad  hoc. 


MUSCLES  OF  THE  POSTERIOR   LIMBS 


M5 


B  The  posterior  portion  ^  (anterior  portion  of  the  long  vastus  of  veterinary 
anatomists),  the  largest  of  the  two,  is  applied  to  the  aponeuroses  of  the  pre- 
cedincr  and  extends  from  the  sacral  spine  to  the  inferior  extremity  of  the  thigh. 
It  is ''prismatic,  very  broad  at  its  upper  end,  and  singularly  contracted  at  the 
opposite  extremity.  A  wide  and  strong  fibrous  band,  which  becomes  aponeurotic 
towards  the  superior  extremity  of  the  muscle,  covers  the  inner  face  in  its  inferior 
portion.  The  muscular  fibres  appear  to  become  longer  as  they  are  more  pos- 
terior ;  all  pass  from  the  upper  end  to  coUect  on  the  tendinous  layer. 

The  muscle  arises,  by  the  superior  extremity  of  its  fasciculi,  on  the  gluteal 
fascia  sacral  spine,  sacro-sciatic  ligament,  the  enveloping  aponeurosis  of  the 
coccygeal  fascia,  and  the  ischiatic  tuberosity.  It  terminates  :  1.  On  the  circular 
imprint  situated  behind  the  trochanter  minor,  by  a  branch  detached  from  the 

Fig.  193. 


StJPERFICIAL  MUSCLES   OF   THE   CROUP    AND    THIGH   OF   THE    HORSE. 

1   Middle  gluteus  ;  2,  anterior  portion  of  the  superficial  gluteus;  3,  tensor  fascia  latae  ;  4,  posterior 
'  portion  of  the  superficial  gluteal ;  5,  biceps  femoris ;  5',  semitendinosus  ;  6,  semimembranosus. 

deep  tendon.     2.  On  the  anterior  face  of  the  patella,  along  with  the  external 
patellar  ligament,  by  the  inferior  extremity  of  that  tendon. 

i?^/a^wws.— Externally,  with  the  gluteal  fascia,  which,  in  being  prolonged  on 
the  posterior  portion,  increases  in  thickness,  and  becomes  more  or  less  elastic. 
Inwardly,  with  the  middle  gluteus  (gluteus  maximus),  the  trochanter  major,  and 
deep  layer  of  the  fascia  lata,  which  isolates  it  from  the  vastus  externus  ;  with 
the  anterior  face  of  the  patella,  on  which  it  glides  by  means  of  a  synovial  bursa 
before  being  inserted  ;  with  the  sciatic  nerves  and  great  adductor  of  the  thigh. 
By  its  anterior  border  it  is  closely  united  to  the  muscle  of  the  fascia  lata ;  by 
»  Lesbre  proposes  to  name  it  the  accessory  of  the  superficial  gluteus. 


346  TTJE  MUSCLES. 

its  posterior  border  it  has  relation,  inferiorly,  with  the   biceps  femoris,  and 
higher,  with  the  semiteudinosns,  which  slightly  covers  it. 

Ad mi. — This  muscle  has  been  justly  considered  by  Lafosse  as  an  abductor 
of  the  thigh.  Bourgelat  wrongly  regarded  it  as  an  extensor,  and  Girard  and 
Rigot  have  repeated  his  error.  Lecoq  has  proved  that  it  rather  produces  flexion 
than  extension.  The  posterior  portion  is  an  abductor  of  the  entire  limb  and  an 
extensor  of  the  thigh,  when  the  sacrum  is  its  fixed  point ;  it  plays  a  part  in 
rearing,  when  the  fixed  point  is  the  leg. 

2.  Middle  Gluteus  (Gluteus  Medius,  Gluteus  Maximus) 
(Figs.  193,  1  ;  194,  1). 

Synonyms. — Ilio-troclianterius  magnus — Girard.  Gluteus  maximus — Bourgelat,  Lafosse, 
Bigot,  etc.     Gluteus  medius  of  Man.     (Superior  portion  of  the  great  ilio-trochanterius — Leyh.) 

Volume — Situation. — This  muscle,  the  largest  of  the  glutei,  is  of  considerable 
volume,  and  is  applied  against  the  iliac  fossa,  the  sacro-sciatic  ligament,  and  the 
longissimus  dorsi. 

Form  and  Structure. — It  is  elongated  from  before  to  behind,  wide  and  very 
thick  in  its  middle,  prolonged  forward  by  a  thin  point,  and  terminated  behind 
by  three  branches  of  insertion — two  tendinous  and  one  muscular.  The  muscular 
fasciculi  entering  into  its  composition  are  generally  very  thick,  and  more  or  less 
long  ;  all  converge  towards  the  posterior  insertions  of  the  muscle. 

Attachments. — 1.  By  the  superior  or  anterior  extremities  of  the  muscular 
fasciculi,  to  the  internal  aspect  of  the  gluteal  fascia,  the  aponeurosis  of  the 
longissimus  dorsi,  the  superior  face  and  the  two  anterior  angles  of  the  ilium, 
the  two  ilio-sacral  ligaments,  and  a  small  portion  of  the  sacro-sciatic  ligament. 
2.  On  the  trochanter  major  by  its  three  posterior  branches  :  the  first,  or  median, 
is  a  thick,  round  tendon  fixed  on  the  summit ;  the  anterior  is  formed  by  a 
second  wide,  thin,  and  flat  tendon,  which  is  inserted  into  the  crest,  after  gliding 
over  the  convexity  ;  the  posterior  is  a  small,  triangular,  fleshy  slip,  aponeurotic 
at  its  anterior  border,  by  means  of  which  it  is  attached  behind  the  trochanter. 
This  slip  corresponds  to  the  pjramidalis  muscle  of  Man. 

Relations. — Covered  by  the  gluteal  fascia  and  the  superficial  gluteal  muscle, 
it  covers  the  longissimus  dorsi,  which  receives  its  anterior  point,  the  iliac  fossa, 
the  deep  gluteal,  the  ilio-sacral  and  sacro-sciatic  ligaments,  the  sciatic  nerves, 
and  the  gluteal  nerves  and  vessels.  Near  the  external  angle  of  the  ilium  it  is 
bordered  by  the  fascia  lata  and  the  iliacus,  which  are  closely  united  to  it. 

Action. — When  its  fixed  point  is  superior,  this  muscle  extends  and  abducts 
the  thigh  ;  but  when  the  femur  is  fixed,  it  causes  the  pelvis  to  rock  on  the 
superior  extremity  of  that  bone,  and  assists  in  the  act  of  rearing.  In  the  first 
instance  it  acts  as  a  lever  of  the  first  order ;  in  the  second,  as  one  of  the  third  order. 

3.  Deep  Gluteus  (Gluteus  Internus)  (Fig.  167,  5). 

Synonyms. — Ilio-trochanterius  parvus— GiVarcZ.  Gluteus  medius — Bourgelat.  Gluteus 
minimus — Lafosse  and  Bigot.     The  gluteus  minimus  of  anthropotomists. 

Form — Situation. — A  small,  short,  thick,  and  quadrilateral  muscle,  flattened 
above  and  below,  situated  beneath  the  preceding,  and  above  the  coxo-femoral 
articulation. 

Structure  and  Attachments. — It  is  composed  of  voluminous  muscular  and 
tendinous  fasciculi,  which  arise  from  the  neck  of  the  ilium  and  the  supra -cotyloid 
ridge,  to  be  directed  outwards  and  backwards,  and  terminate  within  the  con- 
vexity of  the  trochanter  major. 


MUSCLES  OF  TEE  POSTERIOR  LIMBS. 


347 


Belatiom.— Its  upper  face  responds  to  the  middle  gluteus;  the  inferior 
covers  the  coxo-femoral  articulation,  and  strongly  adheres  to  the  fibrous  capsule 
of  that  joint.  This  face  is  also  separated  from  the  rectus  parvus  and  the  origin 
of  the  rectus  femoris  by  a  very  strong  fibrous  layer,  which  extends  from  the 
external  border  of  the  ilium  to  the  base  of  the  trochanter  major.  Its  posterior 
border  is  in  relation  with  the  anterior  gemellus  of  the  pelvis. 


fig.  194. 


SUPERFICIAL   MUSCLES   OF    THE    CROUP   AND   THIGH.    ^ 

1,  Middle  gluteus,  or  gluteus  maximus ;  2,  anterior  spinous  proce.ss  of  ilium;  3,  muscle  of  the 
fascia  lata,  or  tensor  fascia  lata;  4,  superficial  gluteus,  or  gluteus  externus ;  *,  great  trochanter 
of  femur;  5,  fascia  lata;  6,  patella,  with  insertion  of  rectus,  7,  biceps  femons,  or  adductor 
magnus  ;  8,  superior  and,  9,  lateral  coccygeal  muscles;  10,  semitendinosus  and  semimembranosus; 
11,  12,  triceps  abductor  femoris;  13,  fascia  of  the  thigh  ;  14,  vastus 


vastus  externus. 


Action.— It  is  the  special  abductor  of  the  thigh,  and  is  also  an  accessory 
rotator  of  the  femur  inwards.'     (Leyh  says  it  is  a  congener  of  the  preceding 

>  Lesbre  is  of  opinion  that  the  middle  gluteus,  such  as  it  has  been  described  here,  com- 
prises two  superposed  muscles  which  are  distinct  at  their  troclianterian  insertion  :  the  super- 
ficial  is  the  middle  gluteus  of  Man,  and  the  deep  the  small  gluteus  of  anthropotomists. 
Therefore  the  muscle  we  have  described  as  the  deep  gluteal  in  the  Horse  has  no  representative 
in  Man.  Lesbre  proposes  to  name  it  the  abducens  trochanter ius.  It  should  be  the  homotype 
of  the  inferior  branch  of  the  infra-spinatus,  which  is  also  absent  in  man,  and  which  it  would  be 
reasonable  to  describe,  by  analogy,  as  the  abducens  trochiterius. 


348  THE  MUSCLES. 

muscb,  and  therefore  an  extensor  of   the  thigh.     It  may  also  maintain  the 
capsular  ligament  tense.) 

Differential  Characters  in  the  Muscles  of  the  Gluteal  Region  in  the  other 

Animals. 

A.  Ruminants. — In  the  Ox,  Sheep,  and  Goat,  the  two  portions  of  the  superficial  gluteus 
are  less  distinct  than  in  Solipeds  (see  Fig.  197).  They  form  one  muscle,  remarkably  de- 
veloped, the  inner  face  of  which  has  no  point  of  attachment  on  the  femur;  it  glides  behind  the 
trochanter  by  means  of  a  vast  bura;i,  which  is  often  the  seat  of  pathological  alterations — 
synovial  tumours  which  constitute  the  swellings  or  gout  of  the  larger  Ruminants.  Another 
synovial  bursa,  liable  to  tlie  same  malaiiies,  covers  the  patellar  tendon  of  the  muscle  on  its 
passage  over  the  external  condyle  of  the  femur,  and  facilitates  its  gliding  on  that  bony 
eminence.  Before  joining  the  external  patellar  ligament,  this  tendon  shows  a  very  thick, 
fibro-cartilaginous  enlargement,  and  receives  some  of  the  fibres  of  the  external  vastus. 

Another  arrangement  in  this  muscle,  which  it  is  essential  to  recognize  in  a  surgical  point 
of  view,  is  the  union  of  the  anterior  border  of  the  superficial  gluteus  oi  the  Ox  with  the /a«aaZato, 
the  two  layers  of  which  comprise  that  muscle  between  them,  and  closely  adhere  to  each  of 
its  faces.  It  very  frequently  happens  tiiat,  in  emaciated  cattle,  this  fascia  is  ruptured  at  the 
trochanter,  and  the  latter,  instead  of  gliding  on  the  inner  face  of  the  superficial  gluteus,  slips 
before  its  anterior  border  to  pass  through  tlie  solution  of  continuity,  where  it  is  fixed  so  firmly 
that  it  is  sometimes  necessary  to  cut  across  the  fibres  of  the  muscle  in  order  to  give  the  limb 
liberty  of  movement. 

The  middle  gluteus,  not  so  thick  as  in  the  Horse,  is  not  prolonged  so  far  forward  on  the 
longissimus  dorsi ;  and,  on  the  contrary,  the  deep  gluteus,  more  developed  than  in  Solipeds,  is 
readily  divisible  into  two  portions,  of  which  Rigot  has  made  two  distinct  gluteals.  In  the 
Camel,  the  middle  gluteus  does  not  go  beyond  the  border  of  the  ilium  in  front.  The  posterior 
portion  of  the  superficial  gluteus  has  an  attachment  to  the  external  border  of  the  femur. 

B.  Pig. — The  gluteal  muscles  of  this  animal  resemble  those  of  the  Sheep,  though  the 
posterior  portion  of  the  superficial  gluteus  does  not  always  have  a  bursa  for  its  passage  over  the 
external  condyle  of  the  femur. 

C.  Carnivora. — The  superficial  gluteus,  in  its  general  arrangement,  resembles  that  of 
Man ;  its  posterior  portion,  which  is  scarcely  distinct,  arises  from  the  sacrum,  and  terminates, 
by  an  aponeurosis,  below  and  behind  the  trochanter  major.  This  aponeurosis  receives,  in  front, 
a  small  fleshy  band,  which  arises  by  tendinous  fibres  from  the  surface  of  the  middle  gluteus, 
next  the  external  angle  of  the  ilium.  In  these  animals,  also,  the  middle  gluteus  does  not  go 
beyond  the  lumbar  border  of  the  ilium,  and  terminates  behind  by  a  single  branch. 

Comparison  of  the  Gluteal  Muscles  of  Man  with  those  of  Animals. 
The  gluteal  muscles  are  distinguished,  in  regard  to  their  volume,  into  great,  medium,  and 
small  (see  note,  p.  230). 

The  medium  gluteus  does  not  extend  beyond  the  crest  of  the  ilium  in  front. 
With  regard  to  the  gluteus  mazimus,  it  is  inserted  inwardly  into  the  sacrum  and  the  coccyx ; 
below,  into  the  external  bifurcation  of  the  linea  aspera,  from  the  trochanter  major  to  the  middle 
third  of  the  femur,  as  in  Solipeds. 

The  gluteus  parvus  is  proportionately  more  extensive  than  in  the  Horse. 
• 

Muscles  of  the  Thigh. 

These  have  been  divided  into  three  secondary  regions,  which  are  :  the 
anterior  femoral  or  patellar,  t\ie  posterior  femoral,  and  the  internal  femoral  region. 

A.  Anterioe  Femoral  Region. 

This  region  comprises  three  muscles  situated  in  front  of  the  femur  :  the 
muscle  of  the  fascia  lata,  the  crural  triceps,  and  the  gracilis. 

Preparation. — 1.  Place  the  subject  in  the  first  position.  2.  Study  the  fascia  lata  muscle 
immediately  after  removing  the  skin  from  tliis  region.  3.  Take  away  this  muscle  and  the 
superficial  gluteus,  the  semitendinosis  and  semimembranosis,  the  two  adductors  of  the  leg, 
the  pectineus,  and  the  two  adductors  of  the  thigh,  to  expose  the  three  portions  of  the  triceps. 
Separate  these  three  muscular  divisions  from  one  another,  commencing  above  where  they 
are  scarcely  adherent.     Dissect  the  gracilis  at  the  same  time. 


MUSCLES  OF  THE  POSTERIOR  LIMBS.  349 


1.  Muscle  of  the  Fascia  Lata  (Tensor  Fascia  Lat^,  Tensor  Vagina 
Femoris  (Fig.  193,  3). 

Synonyms. — Ilio-aponeuroticus — Girard.  (Tensor  vaginx — Percivall.  Ischio-rotuleus  ex- 
ternus — LeyK). 

Form — Situation. — A  flat  and  triangular  muscle,  situated  in  front  of  the 
superficial  gluteus,  and  outside  the  external  vastus. 

Structure — Attachments. — It  comprises  :  1.  A  flabelliform  muscular  portion, 
covered  on  its  faces  by  tendinous  fibres,  and  attached,  superiorly,  to  the  external 
angle  of  the  ilium.  2.  An  aponeurosis  named  the  fascia  lata,  continuous  with 
the  inferior  border  of  the  muscular  portion,  and  soon  divided  into  two  super- 
posed layers — one  superficial,  the  other  deep.  The  latter  is  insinuated  between 
the  posterior  portion  of  the  superficial  gluteus  and  the  external  vastus,  joins  the 
terminal  tendon  of  the  anterior  portion  of  that  muscle,  and  is  inserted  into  the 
external  border  of  the  femur.  The  first,  which  also  appears  to  divide  into  two 
layers,  is  spread  outwardly  over  the  superficial  gluteus,  where  it  is  confounded 
with  the  gluteal  aponeurosis  ;  and  inwardly,  over  the  internal  crural  muscles,  to 
become  united  to  the  femoral  aponeurosis.  Below,  it  is  prolonged  to  the  patella, 
into  which  it  is  fixed  ;  it  is  even  continued  below  that  bone,  to  join  the  terminal 
aponeurosis  of  the  posterior  branch  of  the  long  superficial  gluteus. 

Relations. — Outwards,  with  the  skin  ;  inwards,  with  the  external  vastus,  the 
anterior  rectus,  and  the  iliacus  ;  behind,  with  the  superficial  and  middle  glutei. 
In  front,  to  a  cluster  of  lymphatic  glands,  where  it  receives,  on  its  aponeurosis, 
the  insertion  of  the  panniculus  carnosus. 

Action. — It  flexes  the  femur  by  raising  the  entire  limb,  and  renders  tense  its 
own  terminal  aponeurosis. 

(In  speaking  of  the  uses  of  this  muscle,  Leyh  states  that — in  addition  to  its 
being  a  flexor  of  the  thigh  and  an  extensor  of  the  leg  through  its  action  on  its 
aponeurosis — it  maintains  the  position  of  the  limb  while  the  animal  is  standing, 
and  allows  the  other  muscles  to  become  relaxed.) 


2.  Crural  Triceps.* 

An  enormous  muscle  lying  against  the  anterior  and  lateral  aspects  of  the 
femur,  composed  of  three  portions  which  are  not  very  distinct  from  each  other 
for  the  greater  part  of  their  extent,  and  which  are  separately  described  as  the 
anterior  rectus  or  straight  muscle,  and  the  vastus  externus  and  internus. 

A.  Anterior  Straight  Muscle  of  the  Thigh  (Rectus  Femoris), 
Middle  Portion  of  the  Triceps  (Figs.  194,  6  ;  197,  16). 

Synonyms. — The  ilio-rotuleua  of  Girard.    (Rectus— Percivall.    Anterior  ilio-rotuleus — Leyh.) 

This  muscle  is  embedded  between  the  two  lateral  portions  of  the  triceps,  and 
extends  from  the  cotyloid  angle  of  the  ilium  to  the  patella,  in  a  direction  slightly 
obUque  forwards  and  downwards. 

Form— Structure. — Elongated,  thick,  and  fusiform,  the  rectus  femoris  offei-s, 
at  its  superior  extremity,  two  short  and  flattened  tendinous  branches  ;  its  middle 
portion  is  formed  of  pale-red  muscular  fibres  lying  close  to  each  other,  and 

'  Following  the  example  of  M.  Cruveilhier,  we  will  describe  by  this  name  the  triceps  cruris 
of  the  older  anatomists,  and  the  anterior  rectus  of  the  thigh. 
25 


850  THE  MUSCLES. 

marked  by  tendinous  intersections  :  its  inferior  extremity  is  enveloped  by  a  vast 
aponeurotic  cone. 

Attachments. — It  originates,  by  its  two  superior  branches,  from  the  imprints 
which  surmount,  forwards  and  outwards,  the  lip  of  the  cotyloid  cavity.  It 
terminates,  by  its  inferior  extremity,  on  the  anterior  face  of  the  patella. 

Belations.—Extevnallj,  internally,  and  posteriorly,  with  the  two  other  portions 
of  the  triceps ;  anteriorly,  with  the  tensor  of  the  fascia  lata.  Its  superior 
extremity,  included  between  the  iliacus  and  the  deep  gluteus,  is  separated  from 
the  coxo-femoral  capsule  by  a  little  adipose  cushion,  which  is  insinuated  between 
its  two  branches. 

Action. — An  extensor  of  the  leg  and  flexor  of  the  thigh. 

B.  Vastus  Externus  (Fig.  201,  11).— Form— Extent— Sitimtion.— This  is  a 
thick  and  wide  muscular  mass,  flattened  on  each  side,  extending  from  the 
superior  extremity  of  the  femur  to  the  patella,  and  situated  to  the  outer  side  of 
the  rectus  femoris. 

Structure  and  Attachments. — The  fasciculi  composing  this  muscle  are  inter- 
mixed with  strong  aponeurotic  layers,  and  originate  from  the  whole  outer  surface 
of  the  femur  and  the  external  half  of  its  anterior  face  ;  they  are  directed  for- 
wards and  downwards,  to  terminate  either  on  the  anterior  rectus,  or  on  the 
superior  face  and  external  side  of  the  patella. 

Relations. — Outwardly,  with  the  fascia  lata  and  superficial  gluteus  ;  inwardly, 
with  the  rectus  femoris  and  the  vastus  internus,  which  is  intimately  confounded 
with  it  except  towards  the  superior  extremity  of  the  femur,  where  the  two 
muscles  are  distinctly  separate  ;  behind,  with  the  femur  and  the  posterior  portion 
of  the  superficial  gluteus. 

Action. — It  is  an  extensor  of  the  leg. 

C.  Vastus  Internus  (Figs.  195,  7  ;  203,  17). — This  muscle  is  not  very 
distinct  from  the  preceding  for  the  greater  part  of  its  extent,  and  forms  with 
it  a  deep  and  wide  channel,  in  which  the  rectus  femoris  is  lodged.  It  is  a 
repetition  of  the  vastus  externus,  in  so  far  as  its  form,  structure,  extent,  attach- 
ments, and  action  are  concerned  ;  but  it  possesses  the  following  peculiarities  : — 

The  fibres  entering  into  its  composition  arise  from  the  whole  internal  face 
and  the  inner  half  of  the  anterior  face  of  the  femur,  and  are  inserted,  some  on 
the  aponeurosis  of  the  rectus  femoris,  others  on  the  internal  patellar  ligament,  the 
corresponding  side  of  the  patella,  and  on  the  superior  face  of  the  same  bone,  in 
common  with  the  vastus  externus. 

Relations. — By  its  external  face,  to  the  latter  muscle  and  the  rectus  femoris  ;  by 
its  internal  face,  to  the  internal  crural  aponeurosis,  the  long  adductor  of  the  leg, 
the  iliacus,  pectineus,  and  to  the  long  branch  of  the  great  adductor  of  the  thigh. 

3.  Anterior  Gracilis  (Crureus,  Rectus  Parvus)  (Figs.  197,  6  ;  203,  15). 

Synonyms. — Gracilis  anterius — Rigot.  Ilio-femoral  gracilis — Girard.  (Crureus  vel  cruralis 
— Percivall.) 

A  small  cylindrical  muscle,  situated  in  front  of  the  capsule  of  the  coxo- 
femoral  articulation,  alongside  the  fibrous  fasciculus  that  strengthens  the  anterior 
portion  of  this  membranous  ligament. 

Attachments. — It  originates  from  the  ilium,  very  near,  and  to  the  outside 
of,  the  external  branch  of  the  rectus  femoris;  it  afterwards  insinuates  itself 
between  the  two  vasti,  and  terminates  on  the  anterior  aspect  of  the  femur  by 
aponeurotic  fasciculi. 


MUSCLES  OF  TEE  POSTEBIOR  LIMBS.  351 

Belations. — This  muscle  is  included  between  the  three  portions  of  the  triceps 
and  the  capsular  ligament  of  the  coxo-femoral  articulation,  to  which  it  strongly 
adheres. 

Action. — It  appears  to  raise  (or  render  tense)  the  capsular  ligament  during 
flexion  of  the  femur. 

B.  Posterior  Crural  Kegion. 

This  region  is  constituted  by  three  muscles  situated  behind  the  thigh.  These 
are  the  biceps  femoris,  the  semitendinosus,  and  the  semimembranosus. 

Preparation. — Place  the  subject  in  the  second  position,  allow  one  hind  leg  to  lie  unfastened, 
and  incline  the  body  to  the  correspnniling  side,  leaving  the  other  liinb  attached  to  the  sup- 
porting bar,  with  the  thigh  slightly  flexed  to  make  these  muscles  tense.  These  preliminary 
arrangements  being  adopted,  proceed  in  the  following  manner :  1.  Make  a  transverse  incision 
through  the  short  adductor  of  the  thigh,  and  turn  back  the  two  portions  to  the  right  and  left, 
so  as  to  expose  the  whole  of  the  semimembninosus,  which  is  to  he  afterwards  dissected  from 
the  semitendinosus  and  the  great  adductor  of  the  thigh.  2.  After  removing  the  aponeurosis 
covering  the  biceps  femoris  and  the  semitendinosus,  the  latter  is  to  be  dissected  by  circum- 
scribing as  carefully  as  possible  its  two  superior  insertions.  3.  The  biceps  is  then  to  be 
prepared.  The  biceps  femoris  and  semitendinosus  can  be  easily  dissected  in  a  limb  arranged 
as  in  Fig.  192. 

1.  Biceps  Femoris  (Triceps  Abductor  Femoris)  (Figs.  193,  5  ;  194,  7). 


'^ms. — Ischio-tibialis  externus — Girard.  A  portion  of  the  long  vastus — Bourgelat, 
Lafosse,  Bigot.  (The  biceps  abductor  femoris  of  Percivall.  Anterior  pubio-ischio-tibialit — 
Leyh.) 

Situation — Extent — Direction. — This  muscle  is  situated  behind  the  thigh  and 
the  glutei  muscles,  and  extends  from  the  sacral  spine  to  the  superior  extremity 
of  the  leg. 

Form  and  Structure. — It  is  narrow  at  its  upper  extremity,  and  very  wide  and 
thin  inferiorly. 

Its  muscular  fibres  are  partly  attached,  by  their  superior  extremities,  to  a 
longitudinal  aponeurotic  layer,  which  gives  the  muscle  a  penniform  appearance  ; 
they  terminate,  inferiorly,  in  a  strong  aponeurosis  united  to  that  of  the  fascia 
lata. 

Attachments. — It  arises,  above,  from  the  crest  of  the  ischial  tuberosity,  where 
the  aponeurosis  which  gives  it  its  penniform  appearance  is  inserted. 

Its  terminal  aponeurosis  is  spread  over  the  tibial  muscles  to  constitute  the 
fascia  of  the  leg,  and  is  inserted  into  the  tibial  crest. 

Belations. — The  gluteal  aponeurosis,  in  the  portion  where  it  becomes  semi- 
elastic,  adheres  to  the  external  surface  of  the  biceps  femoris.  In  front,  the 
muscle  is  related  to  the  posterior  portion  of  the  superficial  gluteus  ;  behind,  to 
the  semitendinosus  ;  within,  to  the  external  muscles  of  the  leg  and  the  sciatic 
nerves. 

Action. — It  flexes  the  leg  and  renders  tense  the  tibial  fascia,  when  its  fixed 
point  is  the  pelvis.     It  rocks  the  pelvis  on  the  femur  when  the  leg  is  fixed. 


2.  Semitendinosus  (Biceps  Rotator  Tibialis)  (Figs.  193,  5' ;  194,  10). 

Synonyms — Ischio-tibialis  medius  or  posticus — Girard.     (Posterior  sacro-ischio-tibialis — 
eyh.    Percivall  describes  this  and  the  next  muscle  by  the  name  of  adductor  tibialis.) 

Situation — Extent — Direction. — This  muscle  is  situated  behind  the  preceding 


352  THE  MUSCLES. 

and  the  superficial  gluteus,  and  extends  from  the  sacral  spine  to  the  leg,  describ- 
ing a  curv«,  the  convexity  of  which  is  posterior. 

jTorm — Structure. — It  is  elongated  from  above  to  below,  bifid  at  its  superior 
extremity,  thick  and  prismatic,  but  nevertheless  flattened  on  both  sides.  Its 
muscular  fibres  are  of  a  pale-red  colour,  are  parallel  to  each  other,  and  follow 
the  general  direction  of  the  muscle  ;  they  terminate,  inferiorly,  on  an  aponeurosis, 
by  a  flat  tendon.  In  its  middle  portion,  the  body  shows  traces  of  the  inter- 
section which  has  obtained  for  this  muscle  the  name — semitendinosus,  in  Man. 

Attachments. — This  muscle  arises,  above,  by  one  of  its  branches,  from  the 
sacral  spine  and  the  sacro-sciatic  hgament,  in  common  with  the  posterior  portion 
of  the  superficial  gluteus,  with  which  it  exchanges  some  fibres ;  ^  by  the  other 
branch,  which  is  the  shortest,  from  the  ischial  tuberosity.  Its  inferior  aponeu- 
rosis is  confounded  with  that  of  the  tibia  ;  the  tendon  glides  over  the  internal 
surface  of  the  tibia,  and  is  inserted  into  its  anterior  crest. 

Belations. — Its  sacro-sciatic  branch  is  covered  by  the  gluteal  aponeurosis,  and 
covers  the  superficial  gluteus.  For  the  remainder  of  its  extent,  it  is  related  : 
posteriorly,  to  that  aponeurosis  ;  anteriorly,  to  the  sciatic  nerves  ;  externally,  to 
the  superficial  gluteus  and  gastrocnemius ;  internally,  to  the  semimembranosus 
and  the  great  adductor  of  the  thigh. 

Action. — It  is  a  flexor  of  the  leg,  and  tensor  of  the  tibial  aponeurosis,  when 
its  fixed  point  is  above  ;  when  the  leg  is  fixed,  it  becomes  one  of  the  active 
agents  in  rearing. 

3.  Semimembranosus  (Adductor  Magnus)  (Figs.  193,  6  ;  194,  10  ;  195,  13). 

Synonyms. — Ischio-tibialis  internua — Girard.     (Great  iscMo-femoralis—Leyh). 

Situation — Volume — Extent — Direction. — Situated  within  the  semitendinosus, 
and  shorter  and  thinner  than  it,  the  semimembranosus  extends  from  the  ischium 
to  the  inferior  extremity  of  the  femur,  and  follows  an  oblique  direction  down- 
wards and  forwards. 

Eorm — Structure. — Elongated  vertically,  flattened  on  each  side,  prismatic,  thick 
at  its  anterior,  and  very  thin  at  its  posterior  borders.  It  is  also  voluminous  at 
its  upper  extremity,  which  has  a  small  prolongation,  the  point  of  which  ascends 
to  the  base  of  the  tail ;  it  is  contracted,  and  terminated  by  a  short  tendon,  at  its 
inferior  extremity.  It  is  formed  of  thick  muscular  fasciculi,  which  all  terminate, 
below,  on  the  terminal  tendon. 

Attachments. — Above  :  1.  To  the  aponeurosis  of  the  coccygeal  muscles,  by  the 
thin  prolongation  from  its  superior  extremity.  2.  To  the  ischial  tuberosity,  and 
the  inferior  face  of  the  ischium.  Below,  to  the  small  eminence  situated  within 
the  internal  condyle  of  the  femur. 

Belations.— lnwa,Tds,  with  a  very  thin  prolongation  from  the  gluteal  aponeu- 
rosis, and  with  the  ischo-cavernous  muscle  and  short  adductor  of  the  leg ;  out- 
wards, with  the  semitendinosus,  the  biceps  femoris,  and  the  sciatic  nerves  ;  in 
front,  with  the  great  adductor  of  the  thigh,  which  is  so  intimately  united  to  it 
that  some  difficulty  is  experienced  in  separating  their  fibres. 

Action. — It  is  an  adductor  of  the  limb  and  an  extensor  of  the  thigh,  when 
its  fixed  point  is  above ;  but  when  the  femur  is  fixed,  it  is  an  auxiliary  in 
rearing. 

*  The  portion  of  this  muscle  whicli  is  attached  to  the  sacral  spine,  certainly  represents  the 
meet  inferior  part  of  the  superficial  gluteus  of  Man. 


MUSCLES  OF  THE  POSTERIOR  L1MB8.  S58 

C.  Internal  Crural  Region. 

This  region  comprises  nine  muscles,  applied  in  three  superposed  lasers  against 
the  inner  aspect  of  the  thigh.  These  are  :  the  lonfi  and  short  adductor  of  the  leff, 
forming  the  superficial  layer  ;  the  pectineus  and  the  small  and  great  adductors  of 
the  thujh,  forming  the  middle  layer.  Those  of  the  deep  layer — that  is,  the  quad- 
rate crural  {quadratus  femoris),  external  obturator,  internal  obturator,  and  gemilli  of 
tlie  pelvis — are  not  all  situated  on  the  inner  face  of  the  femur,  one  of  them  being 
contained  within  the  pelvic  cavity.  With  these  muscles — which  do  not  present 
a  very  considerable  volume — another  region  might  \)q  formed  and  designated  the 
deep  pelvi-crural,  or  coxo-femoral  region. 

Preparation. — 1.  Place  tlie  subject  in  the  first  position.  2.  Prepare  on  one  side  the  two 
muscles  of  the  superficial  layer,  by  removing  the  slight  fibrous  layer  covering  them,  the  internal 
crural  aponeurosis,  and  the  inferior  parieties  of  the  abdomen.  3.  To  expose,  on  the  opposite 
side,  the  three  muscles  of  the  middle  layer,  cut  through  tlie  two  adductors  of  the  leg,  and  turn 
them  back  to  the  right  and  left;  separate  tlie  semimembranosus  from  the  great  adductor  of  the 
thigh  ;  it  may  be  even  useful,  in  order  to  study  the  latter  muscle,  to  remove  the  entire  mass  of 
the  three  ischio-tibial  muscles.  4.  Dissect  the  small  deep  muscles  on  a  separate  piece,  as  shown 
in  Figs.  195  and  197. 

First  Lager. 
1.  Long  Adductor  of  the  Leg  (Sartorius)  (Figs.  195,  8  ;  201,  15). 

Synonymi. — Sublumbo-tibialis — Girard.     {Internal  ilio-rotuleus — Leyh.) 

Form — Situation — Direction. — This  muscle  is  long,  thin,  and  flattened,  narrow 
at  its  inferior  extremity,  and  situated  at  first  within  the  abdominal  cavity,  at  the 
entrance  to  the  pelvis  ;  afterwards,  inside  the  thigh  ;  it  is  oblique  from  above  to 
below,  behind  to  before,  and  within  to  without. 

Structure. — It  is  formed  of  parallel  muscular  fibres.,  which  extend  from  its 
superior  to  its  inferior  border  ;  and  it  terminates,  inferiorly,  by  an  aponeurosis 
which  is  confounded  with  that  of  the  short  adductor. 

Attachments. — It  originates,  superiorily,  from  the  inferior  face  of  the  iliac 
fascia,  near  the  tendon  of  the  psoas  parvus  ;  and  it  is  inserted,  by  means  of  its 
terminal  aponeurosis,  not  on  the  supero-internal  tuberosity  of  the  tibia,  but  on 
the  internal  patellar  ligament,  in  common  with  the  short  adductor. 

Relations. — It  is  covered  by  the  crural  aponeurosis  and  Poupart's  ligament, 
and  covers  the  iliacus,  psoas  magnus,  the  anterior  femoral  nerve,  and  the  vastus 
internus.  Superiorly,  its  inner  border  forms  the  limit — with  the  pectineus  and 
the  anterior  border  of  the  short  adductor — to  a  triangular  space  occupied  by  the 
crural  vessels  ;  below  this  space,  the  two  adductors  of  the  leg  are  closely  adherent 
to  each  other. 

Action. — It  adducts  the  leg,  and  flexes  the  femur. 

2.  Short  Adductor  of  the  Leg  (Gracilis)  (Fig.  195,  9). 

Synonyms. — Subpubio-tibialis — Girard.     (Pubio-tibialis — Leyh.) 

Form — Situation — Direction. — A  large  quadrilateral  muscle,  thin  at  its 
borders,  situated  inside  the  thigh  in  an  oblique  direction  downwards  and  out- 
wai-ds.     It  forms  the  base  of  what  is  called  the  Jf at  of  the  thigh. 

Structure. — Formed  of  parallel  muscular  fibres,  which  extend  from  its  superior 
to  its  inferior  border,  this  muscle  is  tendinous  at  its  origin,  is  covered  by  an 
albugineous  layer,  and  terminates  inferiorly  in  a  wide  aponeurosis. 


354 


THE  MUSCLES. 


Attachments. — It  originates,  by  the  whole  extent  of  its  superior  border,  from 
the  under  surface  of  the  ischio-pubic  symphysis,  and  is  united  to  the  muscle  of 
the  opposite  side — origin.  Its  terminal  aponeurosis,  united  to  that  of  the  sar- 
torious,  is  inserted  on  the  internal  patellar  ligament  and  the  internal  face  of  the 
tibia — movable  insertion ;  posteriorly,  it  is  united  to  the  aponeurosis  of  the  semi- 
tendinosus,  and  with  it  forms  the  tibial  aponeurosis  enveloping  the  tibial  muscles. 

Relations. — Its  superficial  face  is  covered  by  a  cellulo-fibrous  layer,  and  by 
the  saphena  vessels  and  nerves.     It  covers,  by  its  deep  face  the  pectineus,  the 


MUSCLES  OF  THE  STJBLUMBAR,  PATELLAR,  AHD  INTERNAL  CRURAL  REGIONS. 
1,  Psoas  magnus ;  1',  its  terminal  tendon;  2,  psoas  parvus;  3,  iliacus;  4,  its  small  internal  portion; 
5,  tensor  of  the  fascia  lata;  6,  rectus  femoris;  7,  vastus  internus ;  8,  sartorius ;  9,  gracilis;  11, 
pectineus;  12,  adductor  magnus;  12',  adductor  parvus;  13,  semimembranosus;  14,  semitendi- 
nosus.  X,  Portion  of  the  iliac  fascia  ;  B,  portion  of  the  layer  reflected  from  the  aroneurosis  of  the 
obliquus  abdominis  externus,  forming  Poupart's  ligament;  C,  pubic  tendon  of  the  abdominal 
muscles ;  D,  origin  of  the  pubio-femoral  ligament. 


adductors  of  the  thigh,  the  semimembranosus  and  semitendinosus,  and  the 
internal  femoro-tibial  ligament.  It  is  traversed  at  its  origin,  and  altogether  in 
front,  by  a  very  large  vein. 

Action. — An  adductor  of  the  limb  and  a  tensor  of  the  tibial  aponeurosis. 


MUSCLES  OF  THE   POSTERIOR   LIMBS.  355 

Second  Layer. 
3.  Pectineus  (Fig.  195,  11). 

Synonyms.  — Superpubio-femoralis — Girard.  Its  anterior  branch  corresponds  to  the  pectineus, 
and  the  posterior  to  the  middle  adductor,  in  Man.     (^Anterior  pubio-jemoralis — Leyh.) 

Situation — Direction — Form. — Situated  beneath  the  preceding,  in  an  oblique 
direction  downwards,  forwards,  and  outwards,  this  muscle  is  conoid,  thick,  and 
bifid  at  its  superior  extremity,  contracted  at  its  inferior  extremity. 

Structure  and  Attachments. — Its  fasciculi  arise  either  from  the  anterior  border 
and  inferior  surface  of  the  pubis,  or  from  the  surface  of  the  pubio-femoral  liga- 
ment, which  passes  between  its  two  hranches—Jixed  insertion.  They  are  enveloped, 
at  their  inferior  extremity,  by  a  tendinous  cone,  which  is  attached,  on  the  inner 
aspect  of  the  femur,  to  the  imprints  surrounding  the  nutrient  foramen — movable 
insertion. 

Belations. — Inwards,  with  the  short  adductor  of  the  leg  ;  outwards  and 
forwards,  with  the  femoral  insertion  of  the  psoas  magnus  and  iliacus,  the  vastus 
internus,  the  crural  vessels,  and  the  sartorius  ;  behind,  with  the  gracilis,  and, 
near  its  superior  extremity,  with  the  obturator  externus. 

Action. — This  muscle  is  an  adductor  and  flexor  of  the  thigh,  and  more  par- 
ticularly a  rotator  inwards  of  the  same  femur. 

4.  Small  Adductor  of  the  Thigh  (Adductor  Parvus,  Adductor  Brevis) 

(Figs.  195,  12'  ;  203,  14). 

Synonyms. — The  anterior  portion  of  the  biceps  femoralis  of  Bourgelat,  and  of  the  subpubio- 
femoralis  of  Girard.'  (Middle  pubio-femornlis  of  Leyh.  A  portion  of  the  adductores  femoris 
of  Percivall,  and  which  he  has  named  the  adductor  brevis.) 

Situation — Direction. — Situated  beneath  the  gracilis,  between  the  pectineus 
and  the  adductor  magnus  ;  it  passes  in  an  oblique  direction  downwards  and 
outwards. 

Form — Structure. — It  is  flat  from  before  backwards,  thick  and  narrow  at  its 
upper  extremity,  thin  and  wide  inferiorly.  Its  muscular  fibres  are  of  a  pale-red 
colour,  nearly  parallel  to  each  other,  and  sometimes  very  indistinct — superficially, 
at  least — from  those  belonging  to  the  adductor  magnus  ;  inferiorly,  they  become 
aponeurotic. 

Attachments. — Above,  to  the  inferior  face  of  the  pubis  —origin  ;  below,  to  the 
roughened  quadrilateral  surface  on  the  posterior  and  middle  aspect  of  the  femur, 
in  common  with  the  short  branch  of  the  adductor  magnus — termination. 

'Relations. — Inwards,  with  tlie  gracilis  ;  outwards,  with  the  obturator 
externus  ;  in  front,  with  the  pectineus  ;  behind,  with  the  adductor  magnus. 

5.  Great  Adductor  of  the  Thigh  (Adductor  Magnus,  Adductor  Longus) 

(Fig.  195,  12) 

Synonyms. — Posterior  portion  of  the  biceps  femoralis  of  Bourgelat,  and  of  the  subpubio- 
femoralis  of  Girard.     (Posterior  pubio-femoralis — Leyh.) 

Situation — Direction. — The  great  adductor  is  situated  beneath  the  preceding 

*  After  mature  deliberation,  we  have  decided  on  describing  as  two  muscles  the  biceps 
femoralis  of  Bourgelat.  and  to  give  to  them  the  names  of  small  and  great  adductors  of  the  thigh, 
by  which  Bichat  has  designated  the  corresponding  muscles  in  the  lower  extremity  of  Man.  We 
have  thought  it  our  duty,  in  this  instance,  to  follow  the  example  given  us  by  several  German 
authors. 


356 


THE  MUSCLES. 


muscle,   between  the  small   adductor  and   the  semimembranosus,   proceeding 
obliquely  downwards  and  outwards. 

Form — Structure. — It  is  a  long,  thick,  prismatic  muscle,  flat  before  and  behind, 
terminating,  inferiorly,  by  two  branches  of  unequal  length,  and  almost  entirely 
composed  of  parallel  muscular  fibres,  which  are  generally  distinguished  from  the 
fasciculi  of  the  small  adductor  by  their  deeper  colour. 

Attachmmts. — Above,  to  the  lower  face  of  the  ischium  and  to  the  single 

tendinous    band   which    at- 
F'g- 196.  taches   the  two   muscles  of 

the  flat  of  the  thigh  to  the 
pelvic  symphysis  —  origin. 
Below  :  1.  By  its  external 
branch,  the  thickest  and 
shortest,  to  the  quadrilateral 
scabrous  surface  on  the  pos- 
terior face  of  the  femur,  out- 
side the  small  adductor.  2. 
By  its  internal  branch — the 
longest  and  thinnest — to  the 
supero-internal  condyle  of 
the  femur,  in  conmion  with 
the  semimembranosus  and 
the  internal  femoro-tibial 
ligament  —termination. 

Relations. — Inwards,  with 
the  short  adductor  of  the  leg  ; 
behind,  with  the  semimem- 
branosus ;  in  front,  with  the 
small  adductor,  the  external 
obturator,  and  the  inferior 
extremity  of  the  quadratus 
femoris.  Its  external  border, 
thinner  than  the  internal, 
partly  covers  the  superior  ex- 
tremity of  the  latter  muscle,  and  is  separated  from  the  sciatic  nerves  and  the 
biceps  femoris  by  an  aponeurotic  layer.  The  crural  vessels  pass  between  its  two 
branches,  one  of  which,  the  internal,  is  related  anteriorly  and  near  its  insertion  to 
the  vastus  internus. 

Action. — This  muscle  is  an  adductor  and  extensor,  as  well  as  a  rotator  out- 
wards of  the  femur. 

Third  Layer. 

6.  QuADEATE  Crural  (Quadratus  Femoris,  Ischio-Femoralis) 

(Figs.  196,  14  ;  197,  10). 

Synonyms. — The  gracilis  internus  of  Bourgelat,  and  the  ischio-femoral  gracilis  of  Girard. 
(Not  described  by  Percivall.     Small  ischio-femoralis  of  Leyh.     The  quadratus  femoris  of  Man.) 

Situation — Direction — Form — Structure. — Situated  on  the  posterior  face  of 
the  femur,  between  the  great  adductor  and  external  obturator,  and  oblique 
downwards  and  outwards,  the  quadratus  femoris  is  a  small  flat  band,  formed  of 
parallel  muscular  fibres,  slightly  tendinous  at  their  inferior  extremity. 


DEEP   MUSCLES  OF   THE   COXO-FEMORAL   REGION. 

9,  Deep  gluteus,  10,  origin  of  the  rectus  femoris;  11,  rectus 
parvus;  13,  obturator  externus ,  14,  quadratus  femoris; 
15,  depressor  coccygis. 


MUSCLES  OF  THE  POSTERIOR  LIMBS.  357 

Attachments. — Above,  to  the  inferior  surface  of  the  ischium,  in  front  of  the 
ischial  tuberosity — oriffin ,-  terminating,  below,  on  the  linear  imprint  on  the 
posterior  face  of  the  femur,  a  little  below  the  trochanter  internus  (Fig. 
197,  10). 

Relations. — In  front  with  the  posterior  face  of  the  femur  and  external 
obturator.  Behind,  and  inwardly,  with  the  adductor  magnus.  Outwards,  with 
the  sciatic  nerves  and  the  gemellus  posticus. 

Action. — It  is  an  extensor  and  adductor  of  the  femur.  In  our  opinion,  its 
mode  of  attachment  will  not  permit  it  to  rotate  this  bone  either  inwards  or  out- 
wards— at  least  in  Sohpeds. 

7.  Obtueator  Externus  (Fig.  196,  13). 

Synonym. — Subpubio-trochauterius  externus— (riVar^i. 

Form — Structure — Situation — Direction. — A  short,  thick,  flat  muscle,  tri- 
angular, fasciculated,  fleshy  and  aponeurotic,  very  delicate  in  texture,  and 
placed  almost  horizontally  beneath  the  pelvis,  at  the  margin  of  the  obturator 
foramen,  which  it  covers,  and  from  which  it  derives  its  name  of  obturator. 

Attachments. — 1.  To  the  inferior  surface  of  the  pubis  and  ischium,  by  the 
internal  extremities  of  its  fasciculi— ^^a-^^/  itisertion.  2.  To  the  trochanteric  fossa, 
by  the  external  extremities  of  these  fasciculi — movable  insertion. 

Eelations. — Inferior ly,  with  the  pectineus,  the  two  adductors  of  the  thigh, 
and  the  quadratus  femoris ;  superiorly,  with  the  capsule  of  the  hip-joint,  and 
the  internal  obturator. 

Action. — An  adductor  and  rotator  outwards  of  the  thigh. 

8.  Obturator  Internus  (Figs.  196, 197). 

Synonym. — Subpubio-trochanterius  internus — Girard. 

Situation. — This  muscle  is  situated  in  the  pelvic  cavity,  above  the  oval 
foramen,  and  is,  consequently,  opposite  the  external  obturator. 

Form — Structure — Attachnents. — It  is  formed  of  two  portions.  One  is  very 
thin,  and  composed  of  slightly  tendinous,  divergent  muscular  fasciculi,  which 
arise  from  around  the  obturator  foramen,  are  directed  outwards,  and  terminate 
in  a  tendon  belonging  to  the  other  portion.  The  latter,  elongated  and  penni- 
form,  is  situated  in  the  pelvis,  and  extends  from  the  anterior  angle  of  the 
sacrum  to  the  inferior  extremity  of  the  femur,  following  the  direction  of  the 
ischial  border  of  the  ilium,  into  which  it  is  inserted.  The  tendon  to  which  it 
owes  its  penniform  shape  is  inflected  outwards,  behind  the  supra-cotyloid  crest 
or  sciatic  ridge,  joins  the  gemelli,  and  terminates  in  the  bottom  of  the  tro- 
chanteric fossa. 

Relations. — In  its  intra-pelvic  portion,  this  muscle  responds  :  outwards  and 
downwards,  to  the  ilium,  pubis,  ischium,  and  external  obturator  ;  inwards  and 
upwards,  to  the  peritoneum,  important  vessels  and  nerves,  and  to  a  fibrous  layer 
that  separates  it  from  the  bladder.  In  its  extra-pelvic  portion,  it  is  in  relation 
with — behind,  the  middle  gluteal  muscle  and  the  sciatic  nerves  ;  in  front,  with 
the  gemelH.  A  synovial  sheath  facilitates  the  gliding  of  its  tendon  in  the  groove 
in  which  it  turns. 

Action. — It  is  a  rotator  of  the  thigh  outwards,  and,  contrary  to  the  opinion  of 
the  majority  of  authors,  we  believe  it  to  produce  abduction  rather  than  adduc- 


358  TEE  MUSCLES. 

tion,  if  at  any  time   its  position  allows   it  to  execute   either   of  these  two 
movements. 

9.  Gemelli  (Fig.  197,  8,  8,  9). 

Synonyms. —  Ischio  -  trochanterius  —  Girard.  (Gemini — Percivall.  Bifemoro  -  calcaneus — 
Leyh.) 

The  two  small  muscles  which  receive  this  name  are  far  from  presenting  the 
same  arrangement  in  every  subject ;  but  we  will  describe  that  which  appears  to 
be  the  most  frequent.  Two  little  elongated  muscular  fasciculi  are  usually  found, 
one  above,  the  other  below,  the  tendon  common  to  the  two  portions  of  the 
obturator  internus.  These  two  fasciculi  (Fig.  197,  8,  8),  arise  from  the  external 
border  of  the  ischiiun,  follow  the  direction  of  the  above-mentioned  tendon,  and 
are  inserted  into  it  by  the  external  extremities  of  their  fibres,  exactly  representing 
the  gemeUi  of  Man.    But  there  is  also  a  third  (Fig.  191,  9),  wide,  flat,  and  often 

Fig.  197. 


COCCYGEAL   AND    DEEP    MUSCLES    SURROUNDING   THE    COXO-FEMORAL   ARTICULATION. 

1,  Erector  coccygeus ;  2,  curvator  coccygeus;  3,  depressor  coccygeus ;  4,  compressor  coccygeus;  5, 
deep  gluteus;  6,  rectus  parvus ;  7,  tendon  of  the  internal  obturator;  8.  8,  gemelli;  9,  accessory 
fasciculus  of  the  gemelli;  10.  quadratus  femoris ;  11,  sacro-sciatic  ligament;  12,  great  sacro- 
sciatic  foramen ;  13,  superior  ilio-sacral  ligament ;  14,  inferior  ilio-sacral  ligament. 

very  voluminous,  situated  between  the  preceding  and  the  obturator  externus  ;  it 
is  attached,  by  its  inner  border,  to  the  external  border  of  the  ischium,  contracting 
intimate  adhesions  with  the  other  two  and  with  the  tendon  of  the  obturator 
internus,  and  becoming  inserted  by  the  whole  extent  of  its  external  border  into 
the  trochanteric  fossa. 

Relations. — Posteriorly,  to  the  sciatic  nerves  ;  anteriorly,  to  the  capsule  of 
the  hip-joint  and  the  obturator  externus,  through  the  medium  of  an  adipose 
cushion. 

Action. — Like  the  preceding  muscle,  these  rotate  the  thigh  outwards,  and 
perhaps  tend  to  produce  its  abduction. 

Differential  Characters  in  the  Muscles  op  the  Thigh  in  the  other  Animals. 
1.  Anterior  Crural  Region. 

In  the  Ox,  Sheep,  and  Goat,  the  iensor  of  the  fa»cia  lata  is  much  wider  than  in  Sclipeds ; 
that  of  the  Camel  is  so  developed  that  it  completely  euvelo|  s  the  triceps  cruralis.     In  the 


MUSCLES  OF  TEE  POSTERIOR  LIMBS. 


Dog  and  Cat,  the  same  muscle  shows,  in  front,  a  supernumerary  fasciculus — a  thick  and  long 
strip  mixed  inwardly  with  the  sartorius,  and  extending  vertically  from  the  external  angle  of 
the  ilium  to  the  patella,  into  whicli  it  is  inserted  by  a  short  aponeurosis. 

The  rectus  femor is,  in  the  Dog  ami  Sheep,  has  only  one  branch  of  origin. 

The  rtctus  -parvus,  that  very  thin  muscle,  does  not  exist  in  Solipeds  and  Carnivora. 

2.  Posterior  Crural  Region. 

A.  Ruminants. — In  the  Ox,  Sheep,  and  Goat,  the  hiceps  femoris  is  but  little  distinct 
from  tlie  posterior  portion  of  the  superficial  gluteus.  It  is  longer  and  paler  than  in  the  Horse, 
and  its  fibres  are  not  penniform  as  in  Solipeds. 

The  semitendinosus  has  no  sacral  prolongation:  it  arises  only  from  the  ischium. 

The  semimembranosus  is  divided,  inferiorly,  into  two  branches :  one,  very  thick,  passes  to 
the  femur;   the  other,  much  smaller,  termi- 
nates by  a  tendon  which  is  insinuated  iieueath  ''S°  1^^* 
the  internal  lateral  ligament  of  the  femoro- 
tibial   articulation,  to   gain  the  superior  ex- 
tremity of  the  tibia. 

In  the  Camel,  an  important  peculiarity 
should  be  noticed.  In  the  posterior  crural 
region  is  found  an  elastic  apparatus  n  sem- 
bling  that  in  the  anterior  limb  of  this  animal. 
This  is  in  the  form  of  a  thick  fascia,  whicii 
descends  from  the  supra-spinous  ligament  and 
the  aponeurotic  sheath  of  the  coccygeal 
muscles,  is  attached  to  the  ischial  tuberosity, 
largely  covers  the  space  between  the  biceps 
femoris  and  semitendinosus,  crosses  the  sinus 
of  the  femoro-tibial  angle,  and  lies  on  the 
retaining  aponeurosis  of  the  popliteus  and 
lateral  extensor  of  the  phalanges.  Here  it 
divides  into  two  portions  :  the  smaller  is  com- 
posed of  fasciculi  a  little  apart,  which  pass 
backwards  and  mix  with  similar  fasciculi  from 
the  inner  surface  of  the  thigh,  and  become 
attached  to  the  tendon  of  tho  gastrocnemius; 
the  larger  portion  descends  in  front  of  the 
tarsus  and  metatarsus,  and  terminates  towards 
the  lower  third  of  that  bone,  on  the  surface 
of  the  extensor  tendons  of  the  iligits.  The 
use  of  this  elastic  layer  is  to  flex  all  the  articu- 
lations of  the  abdominal  limb  in  a  passive 
manner. 

The  biceps  femoris  in  the  Camel  resembles  that  of  the  Horse. 

The  semitendinosus  is  narrow  in  the  middle,  where  it  lias  an  aponeurotic  tint. 

The  semimembranosus  is  thicker  thnn  the  last-mentioned,  but,  like  it,  it  is  constricted  in 
the  middle  and  expanded  at  its  inferior  extremity.  It  is  attached,  by  its  muscular  fibres,  to  a 
salient  ridge  above  the  internal  condyle  of  the  femur,  and,  by  a  short  fibrous  layer,  to  the 
internal  femoro-tibial  ligament. 

B-  Pig. — The  biceps  femoris  of  this  animal  is  arranged  like  that  of  the  Sheep. 

The  semitendinosus  and  semimembranosus  liave  a  small  point  that  ascends  towards  the  root 
of  the  tail,  and  represents  the  sacro-sciatic  branch  of  these  two  muscles  in  Solipeds. 

C.  Carnivora. — In  these  animals,  the  biceps  femoris  proceeds  from  the  ischium,  and 
divides,  inferiorly,  into  two  unequal  brandies:  an  anterior,  the  largest,  terminates  by  an 
aponeurosis  which  goes  to  the  external  patellar  ligament  and  tibial  crest;  and  a  posterior, 
attached  to  the  tibial  aponeurosis  above  and  external  to  the  gastrocnemius  tendon. 

The  semitendinosus  and  semimemhranosus  are  as  in  the  smaller  Ruminants. 


SUPERFICIAL   MUSCLES   OF   THE   CROUP   AND 
THIGH    IN    THE   COW. 

1,  Middle  gluteal ;  2,  2,  biceps  femoris,  anterioi 
portion  ;  3,  ditto,  posterior  portion ;  4,  semi- 
tendinosus ;  5,  tensor  of  the  fascia  lata. 


3.  Internal  Crural  Region. 

A.  Ruminants. — The  sartorius  in  the  Ox  and  Sheep  is  traversed,  near  its  origin,  by  the 
femoral  artery.  In  the  Camel,  the  gracilis  is  bifid ;  the  anterior  branch  is  the  smallest.  The 
pectineus  of  the  Ox,  single  at  its  upper  extremity,  is  divided  into  two  branches  at  its  inferior 


860  THE  MUSCLES. 

extremity.  One  of  these  branches,  thin  and  pale,  is  prolonged  to  near  the  internal  condyle  of 
the  femur,  while  the  principal  stops,  as  in  the  Horse,  on  the  posterior  face  of  the  bone. 

The  adductor  parvus  is  scarcely  distinct  from  the  adductor  magnus.  The  latter  is  undivided 
at  its  inferior  extremity,  which  stops  at  the  posterior  face  of  the  femur,  without  going  to  the 
inner  condyle  of  that  bone. 

The  obturator  intemus  has  no  upper  portion;  it  is  united  to  the  obturator  externus  in 
passing  through  the  obturator  foramen. 

B   Pig. In  this  animal,  the  internal  crural  muscles  offer  somewhat  the  same  arrangement 

as  in  the  Ox. 

C.  Carnivora. — In  the  Dog  and  Cat,  tlie  sartorius  arises  from  the  external  angle  of  the 
ilium,  and  by  its  muscular  portion  is  prolonged  to  the  inner  face  of  the  tibia.  The  gracilis  is 
much  thinner  and  narrower  than  in  the  other  animals.  The  adductor  parvus  is  a  little,  distinct 
muscle,  which  begins  on  the  inferior  face  of  the  pubis,  and  terminates  at  the  posterior  face  of 
the  femur,  below  the  quadratus  femoris.  The  adductor  magnus  is,  on  the  contrary,  a  wide, 
thick,  undivided  muscle,  attached  to  nearly  the  whole  extent  of  the  linea  aspera  of  the  femur. 

There  is  nothing  particular  to  note  with  regard  to  the  quadratus  femoris  and  the  obturators; 
the  gemelli  are  always  composed  of  two  small,  distinct  fasciculi,  which  comport  themselves  as 
in  Man. 

Comparison  of  the  Muscles  of  Man's  Thigh  with  those  of  the  Thigh  op  Animals. 
The  muscles  of  the  thigh  in  Man  are  divided  into  three  regions,  as  in  animals. 

1.  Anteeior  Muscles. 

The  rectus  parvus  is  not  found  in  Man;  nevertheless,  there  are  reckoned  three  anterior 
muscles  of  the  thigh,  because  the  sartorius,  which  corresponds  to  the  sartorius  of  animals,  is 
included  in  this  region. 

The  sartorius  is  a  very  long  muscle,  the  width  of  which  at  most  is  about  two  fingers' 
breadth.  It  is  attached  above,  not  to  the  lumbo-iliac  aponeurosis,  but  to  the  anterior  and 
superior  iliac  spine;  it  is  afterwards  directed  downwards  and  inwards,  to  pass  round  the 
internal  condyle  of  the  femur,  and  terminate  by  an  expanding  tendon  at  the  crest  of  the  tibia. 

The  tensor  of  the  fascia  lata  shows  the  same  general  arrangement  observed  in  animals.  It 
is  the  same  with  the  triceps  femoris.  The  rectus  femoris  arises  by  two  tendinous  branches:  one 
is  detached  from  the  anterior  and  inferior  iliac  spine;  the  other  from  the  brim  of  the  cotyloid 
cavity. 

2.  Muscles  of  the  Posterior  Region. 

These  are  three  in  number :  the  femoral  or  crural  biceps,  semitendinosus,  and  semimembranosus. 

The  biceps  femoris  is  represented  in  8olipeds  by  the  posterior  portion  of  the  biceps  femoris.  It 
is  an  elongated  muscle  arising  by  two  heads :  tlie  long  head  comes  from  the  ischiatic  tuberosity ; 
the  shortest  from  tlie  middle  of  the  linea  aspera.  After  their  union,  these  two  heads  give  rise 
to  a  tendon  which  is  fixed  into  the  head  of  the  fibula,  and  sends  an  expansion  over  the  tibial 
aponeurosis. 

The  semitendinosus  arises  in  common  with  the  long  head  of  the  biceps ;  its  inferior  tendon 
lis  reflected  beneath  the  internal  tuberosity  of  the  tibia,  to  be  fixed  into  the  crest  of  that  bone. 
This  tendon,  with  that  of  the  sartorius,  forms  the  aponeurotic  expansion  called  the  goose's  foot. 

The  semimembranosus  is  voluminous  in  its  lower  portion,  and  arises,  like  the  other  two, 
from  the  tuberosity  of  the  ischium;  its  fibres  pass  to  a  tendon  which,  on  reaching  the  inner 
Bide  of  the  knee,  terminates  in  the  three  pieces  composing  that  articulation  (see  Fig.  200). 

3.  Muscles  of  the  Internal  Region. 

In  books  on  human  anatomy,  these  muscles  are  snmetimes  designated,  from  their  action,  by 
the  generic  name  of  adductors.  They  comprise :  the  internal  rectus,  peftineus.  first  or  middle 
adductor,  second  or  small  adductor,  and  third  or  great  adductor.  The  square  crural,  the 
obturators,  and  the  gemelli  are  described  among  the  posterior  muscles  of  the  pelvis.  They 
will,  however,  be  briefly  alluded  to  liere. 

The  internal  rectus  corresponds  to  the  gracilis  of  animals.  It  is  a  thin  muscle,  bordering 
the  inner  side  of  the  thigh.  It  is  attached,  above,  to  the  symphysis  pubis ;  below,  to  the  crest 
of  the  tibia,  in  common  with  the  sartorius  tendon. 


MUSCLES  OF  THE  POSTEBIOB  LIMBS.  361 

The  pedineus  repeats  the  anterior  branch  of  the  pectiueus  of  the  Horse.  It  is  inserted, 
below,  into  the  internal  bifurcation  of  the  linea  aspera  of  the  femur. 

The  first  adductor  corresponds  to  the  posterior  branch  of  the  pectineus  of  Solipeds.  It  is 
represented  by  a  voluminous  muscular  mass,  which  arises  from  the  spine  of  the  pubis  and 
terminates  on  the  middle  third  of  the  linea  aspera. 

The  second  or  small  adductor  corresponds  to  the  muscle  of  the  same  name  in  animals.  It  is 
inserted  into  the  same  points  as  the  preceding. 

The  third  or  great  adductor  is  attached,  above,  to  the  ischiatic  tuberosity  and  to  the  whole 

Fig.  199.  Fig.  200. 


MUSCLES  OF   THE   ANTERIOR   FEMORAL 
REGION   IN   MAN. 

I,  Crest  of  the  ilium  5  2,  its  antero- 
superior  spinous  process ;  3,  gluteus 
medius  ;  4,  tensor  vaginse  femoris ;  5, 
sartorius  ;  6,  rectus ;  7,  vastus  externus ; 
8,  vastus  internus ;  9,  patella ;  10, 
iliacus  internus;  11,  psoas  magnus; 
12,  pectineus;  13,  adductor  longus; 
14,  portion  of  adductor  magnus;  15, 
gracilis. 


MUSCLES   OF    THE    POSTERIOR    FEMORAL 
AND  GLUTEAL   REGION   IN   MAN. 

I,  Gluteus  medius ;  2,  gluteus  maximus  ; 
3,  vastus  externus,  covered  by  fascia 
lata ;  4,  long  head  of  biceps ;  5,  short 
head  ;  6,  semitendinosus  ;  7,  7,  semi- 
membranosus ;  8,  gracilis ;  9,  portion 
of  inner  border  of  adductor  magnus ; 
10,  edge  of  sartorius  ;  11,  politeal 
space;  12,  gastrocnemius,  with  its  two 
heads. 


of  the  lower  branch  of  the  ischium  by  aponeurotic  fibres.  It  afterwards  divides  into  two 
branches :  the  external  branch,  entirely  muscular,  is  fixed  into  the  entire  interspace  of  the 
linea  aspera ;  the  internal  branch  gives  rise  to  a  tendon  which  goes  to  the  inner  condyle  of  the 
femur.  Between  these  two  branches  is  found,  as  in  the  Horse,  the  ring  of  the  adductors,  in 
which  pass  the  large  vessels  of  the  thigh. 

The  quadratus  femoris  of  Man  is  nearly  horizontal,  as  it  is  attached,  inwardly,  to  the 
external  border  of  the  ischium,  and  outwardly,  between  the  great  and  small  trochanters. 

The  obturator  internus  and  gemelli  resemble  those  of  the  Dog. 


362  THE  MUSCLES. 

Muscles  of  the  Leg. 

These  muscles,  nine  in  number,  are  grouped  around  the  two  principal  bonea 
of  the  leg,  so  as  almost  to  completely  envelop  them,  leaving  only  the  internal 
face  of  the  tibia  uncovered.  Like  those  of  the  forearm,  they  form  two  particular 
regions  :  an  anterior  and  a  posterior ;  and  they  are  sheathed  in  common  by  the 
tibial  aponeurosis — a  very  solid  fibrous  covering,  which  in  every  respect  corresponds 
to  the  antibrachial  aponeurosis. 

Tibial  Aponeurosis. 

This  aponeurosis  is  formed  of  several  superposed  layers  which  are  intimately 
united,  and  receives,  superiorly,  the  insertion  of  the  biceps  femoris,  the  semi- 
tendinosus,  and  the  gracilis,  which  may  be  considered  as  its  tensor  muscles. 

It  is  continued,  inferiorly,  over  the  tarsus  and  the  metatarsal  region,  in 
becoming  singularly  attenuated,  and  in  covering  the  fibrous  bands  which  bind 
and  retain  the  anterior  tibial  muscles  in  the  bend  of  the  hock.  Its  external 
surface  is  separated  from  the  skin  by  a  very  thin  fibrous  expansion  ;  its  internal 
face  furnishes  special  and  very  firm  sheaths  around  the  majority  of  the  tibial 
muscles. 

The  tibial  aponeurosis  is  attached  to  the  internal  surface  and  crest  of  the 
tibia,  as  well  as  to  the  summit  of  the  calcis.  The  latter  attachment  takes  place 
by  a  thick  fibrous  band,  the  singular  and  complicated  arrangement  of  which 
has  not  yet  been  exactly  described.  It  is  situated  in  front  of  the  tendon  of  the 
gastrocnemius,  or  between  that  tendon  and  the  deep  layer  of  the  posterior  tibial 
muscles.  By  its  borders,  it  is  continuous  with  the  tibial  aponeurosis  or  fascia. 
Superiorly,  it  adheres  most  intimately  to  the  perforatus  tendon,  near  the  point  where 
the  latter  originates ;  then  it  sends  off  a  thick  fasciculus  that  descends  to  the 
gastrocnemius  tendon.  Below  this,  it  appears  to  divide  into  two  branches — an 
external  and  internal — which  are  united  to  the  calcanean  cap  of  the  perforatus 
tendon,  and  are  attached  to  the  sides  of  the  os  calcis  in  such  a  manner,  that 
near  its  insertion  the  gastrocnemius  tendon  is  found  to  be  enveloped  by  a  complete 
fibrous  sheath,  formed  partly  by  the  perforatus  tendon  and  partly  by  the  band 
just  described.  This  latter,  therefore,  constitutes  a  strengthening  apparatus  for 
the  tendon  of  the  gastrocnemius — a  structure  noticed  by  Girard,  who  made  it  a 
branch  of  insertion  of  the  semitendinosus  ;  and  not  without  reason,  perhaps, 
because  it  arises  from  the  tibial  aponeurosis,  which,  in  part  at  least,  is  itself 
derived  from  the  semitendinosus  muscle. 

Preparation  of  the  Muscles  of  the  tegr.— Separate  the  limb  from  the  trunk  by  sawing  through 
the  femur  at  its  middle.  Dissect  the  insertions  of  the  superficial  gluteus,  the  biceps  femoris, 
the  gracilis,  and  the  semitendinosus,  to  observe  the  continuity  of  these  muscles  with  the 
tibial  aponeurosis :  study  the  insertions  of  this  aponeurosis,  particularly  that  which  it  has  on 
the  summit  of  the  os  calcis.  To  expose  the  muscles,  remove  their  aponeurotic  envelope,  leaving, 
however,  the  band  it  forms  in  front  of  the  tendon  of  the  gastrocnemius,  as  well  as  the  bands 
•which  retain  the  tendons.  Eemove  the  hoof  in  the  manner  already  indicated  for  the  anterior 
extremity,  and,  finally,  separate  the  muscles  from  one  another — an  operation  so  very  simple 
as  not  to  require  any  special  directions. 

A.  Anterior  Tibial  Region. 
This  is  composed  of  three  muscles  :  the  flexor  of  the  metatarsus,  the  anterior 
extensor,  and  the  lateral  extensor  of  the  phalanges.    The  first  is  deep-seated,  the 
other  two  are  superficial. 


MUSCLES  OF    THE  POSTERIOR   LIMBS  363 

1.  Anterior  Extensor  of  the  Phalanges  (Extensor  Pedis)  (Fig.  201,  20). 

Synonyms.— FemoTO-piepheilaugeus—Girard.    The  exten8or  longus  digitorum  pedis  of  Man. 

Situation — Direction— Extent. — This  muscle,  situated  in  front  of  the  leg  and 
foot,  follows  the  direction  of  these  two  sections  for  their  whole  extent. 

Form — Strmture. — It  is  formed  of  a  muscular  body  and  a  tendon.     The  first 

Fig.  201. 


EXTERNAL   DEEP   MUSCLES   OF    RIGHT   POSTERIOR   LIMB. 

1,  Crest  of  the  ilium;  2,  inferior  sacro-sciatic  ligament;  3,  sacro-sciatic  ligament;  4,  obturator 
ligament;  5,  tuberosity  of  the  ischium;  6.  anterior  tuberosity  of  the  ilium;  7,  deep  gluteus, 
8,  its  insertion  into  the  great  trochanter,  9  ;  10,  iliacus;  11,  vastus  externus;  12,  rectus  femoris  ; 
13,  great  sciatic  nerve;  14,  gracilis;  15,  sartorius;  16,  patella;  17,  lateral  ligament;  18,  oblique 
flexor  of  the  phalanges,  or  flexor  pedis  accessorius ;  19,  peroneus ;  20,  extensor  pedis;  21, 
soleus,  or  plantaris  ;  22,  gastrocnemius;  23,  flexor  pedis;  24,  tendon  of  oblique  flexor  of  the 
phalanges;  26,  perforatus  tendon;  26, lateral  ligament  of  perforatus  tendon;  27,  28,  annular  liga- 
ment ;  29,  tendon  of  lateral  extensor  of  the  phalanges,  or  peroneus  ;  30,  external  rudimentary 
metatarsal  bone 

is  fusiform,  flat  on  each  side,  aponeurotic  at  its  superficies  in  its  superior  moiety, 
and  tendinous  internally  in  its  inferior  moiety.  The  tendon,  at  first  round,  then 
flat,  commences  a  little  above  the  inferior  fourth  of  the  tibia,  and  reaches  the 
anterior  face  of  the  principal  metatarsus,  where  it  receives  the  extensor  brevis, 


364  TEE  MUSCLES. 

the  tendon  of  the  peroneus,  and  a  funicular  prolongation  of  the  tibial  aponeurosis. 
It  afterwards  descends  on  the  fetlock,  where  it  comports  itself  exactly  as  the 
corresponding  tendon  in  the  anterior  extremity  (see  the  extensor  pedis  in  the 
fore  limb,  p.  324). 

Attachments. — Above,  in  the  digital  fossa  between  the  trochlea  and  external 
condyle  of  the  femur,  through  the  medium  of  the  tendinous  portion  of  the  flexor 
metatarsi— ^j-et?  insertion.  Below,  on  the  capsular  ligament  of  the  metatarso- 
phalangeal articulation,  the  anterior  face  of  the  two  first  phalanges,  and  the 
pyramidal  process  of  the  os  pedis. 

Relations. — The  muscular  portion  responds :  outwardly,  with  the  tibial 
aponeurosis ;  inwardly,  to  the  flexor  metatarsi ;  posteriorly,  to  the  peroneus. 
The  tendon  successively  covers  :  the  anterior  aspect  of  the  tibia,  the  anterior 
capsular  ligament  of  the  tarsus,  the  pedal  muscle,  the  anterior  face  of  the 
principal  metatarsal,  the  articulation  of  the  fetlock,  and  the  two  first  phalanges. 
It  is  covered  by  the  tibial  aponeurosis,  and  by  three  annular  fibrous  bauds  which 
maintain  the  tendon  in  the  bend  of  the  hock.  One  of  these  bands — the  superior 
— is  fixed  by  its  extremities  to  the  tibia,  a  little  above  the  tibio-tarsal  articulation  ; 
it  is  common  to  the  muscle  we  are  describing,  and  to  the  flexor  metatarsi.  The 
middle  band,  attached  to  the  cuboid  branch  of  the  latter  muscle  and  the  inferior 
extremity  of  the  os  calcis,  is  for  the  anterior  extensor  of  the  phalanges.  The 
inferior  maintains  the  two  extensors  against  the  superior  extremity  of  the 
principal  metatarsal. 

Action. — This  muscle  extends  the  digit  and  flexes  the  entire  foot. 

2.  Lateral  Extensor  of  the  Phalanges  (Peroneus)  (Fig.  201,  19). 

Synonyms. — Peroneo-prephalangeus— GiVard.  The  peroneus  brevis  of  Man.  (Tibio- 
prephalangeus — Leyh.) 

Situation — Form — Structure — Extent — Direction. — Situated  on  the  external 
side  of  the  leg,  between  the  preceding  and  the  deep  flexor  of  the  phalanges,  it  is 
composed  of  a  muscular  portion  and  a  tendon.  The  fii-st,  elongated,  prismatic, 
and  slightly  penniform,  extends  in  the  direction  of  the  leg,  from  the  superior 
extremity  of  that  region  to  beyond  its  inferior  extremity.  The  tendon  succeeds 
the  lower  end  of  the  muscular  portion,  and  traverses  the  groove  on  the  middle 
of  the  infero-external  tuberosity  of  the  tibia,  passing  to  the  external  side  of  the 
tarsus,  where  it  is  enclosed  in  a  very  firm  sheath,  and  is  inflected  forwards  to 
become  united  to  the  tendon  of  the  anterior  extensor,  near  the  middle  of  the 
metatarsal  region. 

Attachments. — It  is  attached,  by  the  superior  extremity  of  its  muscular  fibres, 
to  the  external  femoro-tibial  ligament,  to  the  whole  extent  of  the  fibula,  and  to 
the  fibrous  partition  which  separates  this  muscle  from  the  perforans — origin.  It 
terminates  in  the  tendon  of  the  anterior  extensor. 

Relations. — Its  muscular  body  is  enveloped  in  a  special  containing  aponeu- 
rosis, which  separates  it,  in  front,  from  the  anterior  extensor,  and  behind  from 
the  perforans.  The  tendon  covers  the  tibia,  and  margins  the  external  and 
superficial  ligament  of  the  tibio-tarsal  articulation  ;  this  ligament  suppHes  a 
fibrous  ring  for  the  formation  of  its  reflected  sheath.  A  bursa  facilitates  its 
motion  in  the  interior  of  this  sheath. 

Action. — It  acts  Uke  the  preceding. 


MUSCLES  OF  TEE  POSTERIOR  LIMBS. 


3.  Flexok  of  the  Metatarsus  (Flexor  Metatarsi)  (Fig.  202). 

Synonyms. — Tibio-premetatarsus— GtVard.     Its  muacular  portion  represents  the   tibialis 
anticus  of  autliropotomists. 

This  muscle  is  situated  beneath  the  anterior  extensor  of  the  phalanges,  on  the 
external  surface  of  the  tibia,  and  is  composed  of  two  distinct  portions— one  muscu- 
lar, the  other  aponeurotic,  not  united  from  end  to  end, 
but  placed  parallel  one  before  the  other. 

A.  Tendinous  Portion  (Fig.  202,  1). — Course — 
Attachments. — This  is  a  strong,  pearly- white  cord,  com- 
prised between  the  muscular  portion  and  the  anterior 
extensor  of  the  phalanges.  It  commences  at  the  inferior 
extremity  of  the  femur,  in  the  fossa  between  the  trochlea 
and  the  external  condyle  ;  it  afterwards  passes  through 
the  superior  groove  of  the  tibia,  where  it  is  enveloped 
by  a  prolongation  from  one  of  the  synovial  membranes 
of  the  femoro-tibial  articulation,  giving  origin,  below 
this  groove,  to  the  muscular  fibres  of  the  anterior  ex- 
tensor of  the  phalanges.  Lower,  it  receives  some  of 
the  fasciculi  from  the  muscular  portion,  to  which  it 
sends,  in  exchange,  several  aponeurotic  layers  ;  it  passes 
under  the  superior  annular  band  in  front  of  the  hock, 
in  company  with  the  anterior  extensor,  and  reaches  the 
level  of  the  trochlea  of  the  astragalus,  where  it  is 
perforated  to  form  a  ring  for  the  passage  of  the  inferior 
extremity  of  the  muscular  portion.  It  finally  terminates 
in  two  branches  :  a  large  one,  inserted  in  front  of 
the  superior  extremity  of  the  principal  metatarsus  (Fig. 
202,  4)  ;  the  other,  narrower,  deviates  outwards  to  reach 
the  anterior  surface  of  the  cuboid  bone  (Fig.  202,  3). 

Relations. — In  front,  with  the  anterior  extensor  of 
the  phalanges  ;  behind,  with  the  muscular  portion  and 
the  anterior  capsular  ligament  of  the  tarsus. 

Action. — This  tendon  enjoys  the  curious  property  of 
bending  the  hock  by  an  action  altogether  mechanical, 
whenever  flexion  of  the  superior  bones  of  the  limb  takes 
place.  It  is,  therefore,  a  conducting  cord  which  regu- 
lates the  movements  of  flexion  in  the  hock,  and  con- 
forms them  to  those  taking  place  in  the  other  joints, 
without  requiring  the  intervention  of  an  active  agency 
for  the  execution  of  these  movements. 

Another  function  has  also  been  attributed  to  it — 
that  of  passively  opposing  the  flexion  of  the  femur  on 
the  tibia  while  the  animal   is  standing,  and   in  this 

way  serving  as  an  adjunct  to  the  muscular  force  which  supports  the  weight  of 
the  body.  But,  in  our  opinion,  this  is  incorrect ;  as,  in  order  that  it  may  perform 
this  task,  it  would  be  necessary  for  the  foot  to  be  maintained  in  a  fixed  position 
by  the  contraction  of  its  extensor  muscles.  But  these  muscles  are  really  the 
heads  of  the  gastrocnemius,  which  have  their  origin  behind  the  femur,  and 
which  undoubtedly  tend  to  flex  that  bone  on  the  tibia — that  is,  to  determine 


FLEXOR  METATARSI. 
Tendinous  portion ;  2,  Ha 
attachment  to  the  femur; 
3,  its  cuboid  branch ;  4, 
its  metatarsal  branch  ;  5, 
muscular  portion ;  6,  its 
tendon  passing  through 
the  ring  of  the  tendinous 
portion  ;  7,  cuneiform 
portion    of  this    tendon; 

8,  its  metatarsal  branch ; 

9,  anterior  extensor  of  the 
phalanges  drawn  outwards 
by  a  hook.  A,  Lateral 
extensor;  B,  tibial  inser- 
tion of  the  middle  patel- 
lar ligament;  C,  femoral 
trochlea 


866  THE  MUSCLES. 

the  movement  it  is  supposed  to  prevent.  And  experiment  clearly  shows  that  we 
are  justified  in  this  opinion  ;  for  division  of  this  tendon  in  the  living  animal 
does  not  interfere  in  the  slightest  degree  with  its  natural  attitude,  either  when 
standing  at  liberty  or  when  compelled  to  stand.^ 

B.  Muscular  Portion. — Situation — Form — Structure. — Situated  between 
the  tendinous  cord  and  the  tibia,  this  portion  is  elongated  from  above  to  below, 
very  wide  at  its  superior  part  and  narrow  inferiorly,  where  it  terminates  in  a 
bifid  tendon. 

Attachments. — It  originates,  by  the  upper  extremity  of  its  muscular  fibres, 
from  the  tibia,  below  and  on  the  sides  of  the  groove  through  which  the  tendon 
passes  ;  its  most  superficial  fibres  are  even  attached  to  the  aponeurotic  sheath 
which  envelops  the  lateral  extensor.  Its  terminal  tendon  (Fig.  201,  6)  traverses 
the  annular  ligament  which  the  tendinous  portion  forms  at  its  inferior  extremity, 
and  becomes  inserted,  by  one  of  its  branches,  in  front  of  the  superior  extremity 
of  the  principal  metatarsal  bone,  along  with  the  analogous  branch  of  the 
tendinous  division  (Fig.  200,  8).  The  other  ramification  is  directed  to  the 
inside  of  the  tarsus,  to  be  attached  to  the  second  cuneiform  bone  (Fig.  202,  7). 

Relations. — In  front,  with  the  tendinous  portion  of  the  muscle  and  the 
anterior  extensor  of  the  phalanges  ;  behind,  with  the  external  face  of  the  tibia. 
The  tendon,  after  traversing  the  annular  ligament  of  the  cord,  covers  the 
metatarsal  branch  of  the  latter,  and  is  in  turn  covered  by  the  anterior  extensor. 

Action. — It  is  an  active  agent  in  flexing  the  foot  on  the  leg. 


B.  Posterior  Tibial  Region. 

This  region  includes  six  muscles,  which  are  arranged  in  two  superposed 
layers  behind  the  tibia.  The  superficial  layer  is  formed  by  the  gastrocnemii, 
soleus  or  plantaris,  and  the  superficial  flexor  of  the  phalanges.  The  deep  layer  is 
composed  of  the  popliteus,  the  deep  flexor,  and  the  oblique  flexor  of  the  phalanges. 

•  J.  F.  Meckel  rightly  considers  this  tendinous  cord,  not  as  a  portion  of  the  anterior  tibial, 
but  as  a  dependency  of  tlie  extensor  longus  digitorum.  It  would  be  wrong,  however,  to 
describe  it  apart  fioin  the  anterior  tibial,  properly  so-called— that  is,  the  muscular  portion  of 
our  flexor  metatarsi,  the  two  being,  in  their  action,  essentially  one. 

Is  there  anything  in  the  human  species  analogous  to  this  fibrous  cord?  After  much 
hesitation,  we  answer  in  the  affirmative,  and  give  it  as  our  opinion  that  this  tendon  represents 
the  peroneus  tertius  in  Man.  These  are  our  reasons  tor  making  tliis  assertion,  hazardous  as  it 
certainly  is  at  first  sight:  In  Man,  the  peroneus  tertius  cannot  always  be  easily  distinguished 
from  the  extensor  loiigus  digitorum ;  so  that  these  two  muscles  may  be  regarded  as  a  single 
one  until  reaching  the  instep,  where  it  extenda  to  the  phalanges  of  the  toes  on  the  one  part,  nnd 
the  metatarsus  on  the  other.  Precisely  the  same  arrangement  is  found  in  Solipeds  ;  the  single 
muscle  divides  into  two  fasciculi,  one  for  the  digital  region  (anterior  extensor  of  the  phalanges), 
the  other  to  the  metatarsal  region  (tendon  of  our  flexor  metatarsi).  This  tendon,  then,  exactly 
represents  the  fasciculus  of  the  long  common  extensor  of  the  toes  (in  Man),  which  goes  to  the 
metatarsus,  and  is  designated  the  peroneus  tertius. 

But  to  this  it  may  be  said  :  Your  peroneus  tertius  in  the  Horse  has  no  relation  whatever  to 
the  peroneus,  and  does  not  this  prove  that  you  are  in  error?  No ;  for  if  this  muscle  is  attached 
to  the  fibula  in  Man,  it  is  because  the  principal  muscle  on  which  it  depends  is  inserted  there 
itself.  But  as  the  anterior  extensor  of  tlie  phalanges  of  the  Horse— that  is,  the  common 
extensor  of  the  toes— is  not  inserted  into  the  fibula,  and  has  no  connection  with  it  in  any  way, 
its  metatarsal  fasciculus— or  rather  its  tendinous  cord  or  peroneus  tertius— ought  to  be  absolutely 
in  the  same  condition.  We  repeat,  however,  that  this  opinion  may  be,  perhaps,  a  little 
hazardous ;  and  we  give  it  with  reserve,  though  we  have  some  reasons  for  considering  it  to  be 
correct. 


MUSCLES  OF  TEE  POSTEBIOB  LIMBS. 


367 


!.  Gastrocnemius,  or  Gemelli  of  the  Tibia  (Gastrocnemius  Externus) 
(Figs.  201,  22  ;  203,  20). 

Synonyms. — Bifemoro-calcaneus — Girard. 

Situation— Comj)ositio7i—Extent.— The  gemelli  of  the  leg,  situated  behind  the 

Fig.  203. 


MUSCLES   ON   INNER   ASPECT   OF   LEFT    POSTERIOR   LIMB. 

1,  Crest  of  the  ilium;  2,  section  through  it;  3,  sacro-sciatic  ligament;  4,  pyriformis;  5,  posterior 
portion  of  sacro-sciatic  ligament ;  6,  tuberosity  of  ischium  ;  7,  anterior  portion  of  ischium,  sawn 
through;  8,  pubis;  9,  obturator  foramen;  10,  external  iliac  artery  and  vein,  11;  12,  obturator 
artery  and  vein  (the  figures  are  placed  on  the  internal  obturator  muscle);  13,  long  adductor  of 
the  leg,  or  sartorius;  14,  small  adductor  of  the  thigh,  or  adductor  parvus;  15,  short  adductor 
of  the  leg,  or  gracilis;  16,  rectus  of  the  thish  ;  17,  vastus  internus  ;  18,  patella,  with  insertion 
of  rectus;  19,  upper  extremity  of  tibia;  20,  gastrocnemius;  21,  popliteus ;  22,  oblique  flexor 
of  the  phalanges,  or  flexor  pedis  accessorius,  with  its  tendon,  34;  23,  perforans  muscle,  with  its 
tendon,  35  ;  24,  flexor  metatarsi  ;  25,  anterior  extensor  of  the  phalanges,  or  extensor  pedis  ;  26, 
annular  ligament ;  27,  tendon  of  flexor  metatarsi,  and  its  cunean  branch.  28  ;  29,  tendon  of  the 
superficial  flexor  of  the  phalanges;  30,  tendon  of  gemelli  or  gastrocnemius;  31,  os  calcis ; 
32,  astragalus;  33,  perforatus  tendon ;  34,  tendon  of  oblique  flexor  joining  the  perforans 
tendon,  35 ;  36,  large  metatarsal  bone ;  37,  extensor  pedis  tendon  ;  38,  terminal  knob  of  small 
metatarsal  bone. 


femoro-tibial  articulation,  below  the  ischio-tibial  muscles,  constitutes  two  thick 


368  THE  MUSCLES. 

fleshy  fasciculi  distinct  from  one  another  only  at  their  superior  extremity,  being 
confounded  for  the  remainder  of  their  extent,  and  continued  inferiorly  by  a 
single  tendon  which  extends  to  the  point  of  the  os  calcis. 

Form — Stnicture. — Both  of  these  muscular  masses  are  flattened  on  both 
sides,  thick  in  the  middle,  narrow  at  the  extremities,  and  intersected  by  strong 
tendinous  bands.  By  their  union  they  form  a  wide  channel,  open  in  front,  which 
embraces  the  femoro-tibial  articulation  and  the  muscles  of  the  deep  layer. 

The  tendon,  at  first  fasciculated,  then  single  and  funicular,  receives  that  of 
the  soleus,  and  is  reinforced  by  a  fasciculus  from  the  fibrous  band  annexed  in 
front  to  the  tendon  of  the  perforatus  (see  the  description  of  the  tibial  aponeurosis, 
p.  362).  An  aponeurotic  layer  which  covers  the  gastrocnemius,  is  continued 
downwards,  partly  with  the  fibrous  band,  and  partly  with  the  tendon  of  the 
muscle  itself. 

Attachments. — The  external  gemellus  arises  on  the  femur,  from  the  rugged 
lip  which  margins  the  supra-condyloid  fossa  in  front ;  the  internal,  from  the 
collection  of  tubercles  which  constitutes  the  crest  of  the  same  name.  The 
terminal  tendon  of  the  two  bellies  is  fixed  on  the  summit  of  the  os  calcis,  not  at 
its  anterior  part,  but  posteriorly  ;  this  being  lubricated  by  a  bursa  that  forms  a 
gliding  surface  on  which  the  tendon  rests  during  extreme  flexion  of  the  foot 
(Fig.  101,  1). 

Relations. — By  their  superficial  face,  to  the  three  ischio-tibial  muscles,  and 
the  tibial  aponeurosis  ;  by  their  deep  face,  to  the  perforatus — which  adheres 
intimately  to  the  vastus  externus — to  the  posterior  ligament  of  the  femoro- 
tibial  articulation,  the  popliteal  muscle  and  vessels,  the  great  sciatic  nerve,  and 
the  oblique  and  deep  flexor  muscles  of  the  phalanges.  The  tendon  lies  beside 
that  of  the  perforatus,  which  is  twisted  around  and  completely  envelops  it  at 
its  inferior  extremity,  in  common  with  the  fibrous  band  from  the  tibial  aponeu- 
rosis. The  two  tendons  form  what  is  usually  termed  the  tendon  of  the  hock,  or 
tendo  Achilles. 

Action. — The  gastrocnemius  extends  the  foot  upon  the  tibia.  It  acts  as  a 
lever  of  the  first  order  when  the  limb  is  raised  from  the  ground,  and  as  one  of 
the  second  order  when  the  hoof  is  placed  on  the  ground.  It  maintains  the 
tibio-tarsal  angle  while  the  animal  is  standing,  and  in  progression  gives  to  the 
hock  that  spring  which  carries  the  body  forward. 

2.  Soleus  (Plantaeis)  (Fig.  201,  21). 

Synonyms. — Bourgelat  and  liis  successors  have  erroneously  assimilated  it  to  the  plantaris  of 
Man.  In  regarding  this  little  muscle  as  the  soleus,  we  conform  to  the  well-founded  opinion 
of  Cuvier.     It  is  the  peroneo-calcaneus  of  Girard. 

Form — Situation. — This  is  a  thin,  long,  and  riband-shaped  rudimentary 
muscle,  situated  at  the  external  side  of  the  leg,  between  the  tibial  aponeurosis 
and  the  muscular  portion  of  the  perforans. 

Attachments. — It  is  fixed,  by  its  superior  extremity,  behind  the  supero-external 
tuberosity  of  the  tibia  ;  and  terminates,  inferiorly,  by  a  small  tendon,  which  joina 
that  of  the  gastrocnemius. 

Action. — It  is  a  feeble  auxihary  of  the  last-named  muscle. 


MUSCLES  OF  THE  POSTERIOR  LIMBS.  369 

3.  SuPEEFiciAL  Flexor  of  the  Phalanges  (Flexor  Perforatus, 
Gastrocnemius  Internus)  (Figs.  201,  25  ;  203,  30). 

fi'j/no/ij/ms.— Femoro-phalangeus — Girard.  It  is  represented  in  Man  by  the  plautaris  and 
flexor  brevis  digitorum,  or  perforatus.  Tliese  two,  in  the  majority  of  Mammalia,  are  united 
from  end  to  end  to  form  a  single  muscle. 

Form — -Structure. — The  perforatus  of  the  posterior  limb  is  only  represented, 
in  reality,  by  a  long  tendinous  cord  that  is  somewhat  muscular,  slightly  thickened, 
and  fusiform  in  its  upper  fifth,  which  forms  the  body  of  the  muscle. 

Origin — Direction  and  Relations — Termination. — It  originates,  by  its  upper 
extremity,  in  the  supra-condyloid  fossa,  descends  between  the  two  portions  of  the 
gastrocnemius — to  the  external  of  which  it  is  intimately  related — on  the  posterior 
face  of  the  femoro-tibial  articulation,  and  on  the  three  posterior  deep  tibial 
muscles.  On  reaching  the  inferior  extremities  of  the  muscular  bellies  of  the 
gastrocnemius,  it  becomes  exclusively  tendinous,  and  is  directly  united  to  the 
fibrous  band  which  reinforces  the  tendon  of  the  hock.  It  afterwards  disengages 
itself  below  the  gastrocnemius,  and  is  placed  at  the  internal  side  of  its  tendon, 
then  on  its  posterior  surface,  and  in  this  position  gains  the  summit  of  the  os 
calcis.  There  it  becomes  widened  to  form  a  fibrous  cap,  which  is  covered  by  a 
large  vesicular  synovial  membrane  ;  it  is  moulded  to  the  posterior  region  of  this 
bony  eminence,  which  it  completely  envelops  in  order  to  be  fixed  on  its  lateral 
portions,  and  is  united  to  the  calcanean  band  from  the  tibial  aponeurosis.  From 
this  point  the  tendon  of  the  perforatus  is  prolonged  behind  that  of  the  perforans, 
to  the  posterior  face  of  the  second  phalanx,  where  it  terminates  in  exactly  the 
same  manner  as  the  analogous  muscle  of  the  anterior  limb. 

Action. — It  flexes  the  second  phalanx  on  the  first,  and  this  on  the  metacarpus 
It  also  concurs  in  the  extension  of  the  foot.  Its  principal  office,  however,  is  that 
of  a  mechanical  stay,  destined  to  sustain  the  equilibrium  of  the  body  while  the 
animal  is  in  a  standing  posture,  by  preventing  the  diminution  of  the  angle  of 
the  hock  and  that  of  the  fetlock — the  femur  being  fixed  by  the  contraction  of  the 
crural  triceps  and  the  gluteal  muscles. 

Beep  Layer. 
4.  PoPLiTEUS  (Fig.  203,  21). 

Synonyms. — The  abductor  tibialis  of  Bourgelat,  and  femoro-tibialis  obliquus  of  Girard. 

Situation — Direction — Form — Structure. — Situated  behind  the  tibia,  below 
the  femoro-tibial  articulation,  this  muscle  is  oblique  downwards  and  inwards, 
short  and  triangular,  tendinous  at  its  supero-external  angle,  and  formed,  for  the 
remainder  of  its  extent,  of  divergent  fleshy  fibres,  the  longest  of  which  are  the 
most  inferior. 

Attachments. — 1.  In  the  lowest  of  the  two  fossae  on  the  outside  of  the  external 
condyle  of  the  femur,  by  its  tendon — origin.  2.  On  the  supero-posterior  trian- 
gular surface  of  the  body  of  the  tibia,  by  the  inferior  extremity  of  its  muscular 
fibres — termiyiation. 

Relations. — Posteriorly,  with  the  gastrocnemius  and  perforatus.  In  front, 
with  the  posterior  ligament  of  the  femoro-tibial  articulation,  and  the  pophteal 
vessels.  Outwards,  with  the  oblique  and  deep  flexors  of  the  phalanges.  Inwards, 
with  the  semitendinosus  and  tibial  aponeurosis.  The  tendon,  concealed  at  its 
origin  beneath  the  external  femoro-tibial  ligament,  glides,  by  its  deep  face,  over 


370 


TEE  MUSCLES. 


the  contour  of  the  external  semilunar  cartilage  and  the  posterior  portion  of  the 
external  facet  on  the  tibia. 

Action. — It  flexes  the  tibia,  and  gives 
^'S-  2^"*-  it  a  slight  rotatory  movement  outwards. 

5.  Deep  Flexoe  of  the  Phalanges 
(Flexor  Perforans,  Flexor  Pe- 
dis) (Figs.  201,  23  ;  203,  23). 

Synonyms.  —  Tibio-phalangeus  —  Girard. 
The  flexor  perforans  and  flexor  longus  pollicis 
pedis  of  Man.    {Great  tibio-phalangeus — Leyh.) 

Extent — Situation — Direction — Com- 
position.—Extending  from  the  superior 
extremity  of  the  leg  to  the  third  phalanx, 
and  situated  behind  the  tibia  and  foot, 
the  direction  of  which  it  follows,  this 
muscle  is  composed  of  a  muscular  body 
and  a  tendon. 

Form,  Structure,  mid  Attachments  of 
the  muscular  portion. — This  is  thick  and 
prismatic,  and  incompletely  divided  into 
two  portions — an  internal,^  and  an  ex- 
ternal,^ which  is  the  most  voluminous. 
It  is  attached  :  1.  To  the  posterior  face 
of  the  tibia,  on  the  linear  imprints  which 
occupy  the  inferior  triangular  surface. 
2.  To  the  supero-external  tuberosity  of 
the  same  bone.  3.  To  the  peroneus. 
4.  To  the  interosseous  ligament  uniting 
that  bone  to  the  tibia. 

Direction  and  Attachments  of  the 
tendon. — The  tendon  commences  above 
the  inferior  extremity  of  the  tibia, 
where  it  is  usually  double,  each  muscular 
portion  being  succeeded  by  a  tendon, 
the  volume  of  which  is  in  harmony  with 
the  size  of  the  muscle  from  which  it 
proceeds.  The  single  tendon  resulting 
from  the  union  of  these  two  primary 
ARTICULAR  CAPSULES  AND  BURs^  IN  THE  ^^^s,  cutcrs  thc  groovc  f ormed  by  the 
POSTERIOR  LIMB  OF  THE  HORSE.  iuuer  facc  of  thc  OS  calcis,  where  it  is 

I,  Tibio-tarsal  capsule  (bulging  anteriorly);  2,      retained      by     a      fibrOUS      arch     which 

ibid,  (bulging  posteriorly);  3  superior  cW-cfe-     transforms  this  channel  into  a  perfect 

sac  ot  the  tarsal  bursa;    4,  inferior  cul-de-sac  ^ 

of  the    same;    5,    capsule    of  the    metatarso 

phalangeal  articulation ;  6,  7,  8,  superior,  middle,  and  inferior  culs-de-sac  of  the  sesamoid  bursa  ; 
9,  posterior  cul-de-sac  of  capsule  of  the  first  interphalangeal  articulation ;  10,  inferior  part  of  the 
sesamoid  bursa  completely  exj)osed  by  excision  of  the  reinforcing  membrane  of  the  perforans 
tendon;  11,  lateral  cul-de-sac  of  the  second  interphalangeal  or  pedal  articulation.  T,  Tibia; 
M,  matatarsus;  C,  lateral  cartilage  turneii  outwards  and  forwards;  Fs,  perforatus  tendon;  Fp, 
perforans  tendon  ;  Ls,  suspensory  or  superior  sesamoid  ligament. 


The  tibialis  posticus  of  Man. 


*  The  flexor  longus  pollicis  of  Man. 


MUSCLES   OF  THE  POSTERIOR  LIMBS.  371 

sheath,  named  the  tarsal  sheath.  It  glides  in  the  interior  of  this  canal  by 
means  of  a  very  extensive  bursa,  which  extends  upwards  on  the  posterior  liga- 
ment of  the  tibio-tarsal  articulation,  and  is  prolonged  inferiorly  to  the  middle 
third  of  the  metatarsus.  The  tendon  of  the  perforans  afterwards  descends, 
vertically,  behind  the  suspensory  ligament,  receiving  from  it  a  strong  fibrous 
band  (the  suhtarsal  ligament),  analogous  to  that  of  the  fore  limb,  but  less 
voluminous  ;  it  then  passes  through  the  annular  portion  of  the  perforatus,  is 
inflected  with  that  muscle  over  the  sesamoid  groove,  glides  on  the  posterior 
articulating  surface  of  the  second  phalanx  and  that  on  the  navicular  bone, 
thinning  out  into  a  plantar  aponeurosis,  which  is  provided  with  a  phalangeal 
reinforcing  sheath,  and  finally  terminates  on  the  semilunar  crest  of  the  os  pedis. 
This  tendon,  therefore,  on  leaving  the  tarsus,  comports  itself  exactly  like  that  of 
the  anterior  limb. 

Relations. — Outwards,  with  the  lateral  extensor  of  the  phalanges,  the  soleus, 
and  the  tibial  aponeurosis.  Inwards,  with  this  aponeurosis  and  the  oblique  flexor. 
Behind,  with  the  gastrocnemius,  the  perforatus,  and  the  fibrous  band  of  the  tendon 
of  the  hock.     In  front,  with  the  tibia. 

The  tendon  glides  in  the  tarsal  sheath  by  means  of  a  very  extensive  bursa  that 
ascends  on  the  posterior  ligament  of  the  tibio-tarsal  articulation,  behind  which  it 
appears  as  a  soft  tumour  (thoroughpin)  when  it  is  distended  by  synovia  (Fig. 
204,  3).     The  bursa  descends  to  about  the  lower  third  of  the  metatarsal  region. 

Action. — This  muscle  flexes  the  phalanges  on  one  another  and  on  the  meta- 
tarsus. It  may  also  extend  the  foot  in  pressing,  during  its  contraction,  behind 
the  tibio-tarsal  articulation.  In  addition  to  this,  its  tendon  acts,  while  the 
animal  is  standing,  as  a  mechanical  support  to  the  phalanges  and  the  articular 
angle  of  the  fetlock. 

In  the  Ass  and  Mule,  the  tendon  of  the  perforans  does  not  receive  any  sub- 
tarsal  ligament,  this  being  absent  in  them. 

6.  Oblique  Flexor  of  the  Phalaijges  (Flexor  Accessorius) 
(Fig.  203,  '22) 

Synonyms. — Peroneo-phalangeus— G/rard.  The  tibialis  posticus  of  Man.  (Small  tihio- 
phalangeua — Leyh.) 

Situation — Direction — A  muscle  situated  behind  the  tibia,  between  the  pop- 
liteus  and  the  perforans,  in  a  direction  slightly  oblique  downwards  and  inwards. 

Form — Structure. — It  is  composed  of  a  fleshy  fusiform  body,  intersected  by 
numerous  fibrous  bands,  and  provided  with  a  funicular  tendon  inferiorly 

Attcichments. — The  superior  extremity  arises  behind  the  external  tuberosity 
of  the  tibia — origin.  The  tendon  is  united,  by  its  inferior  extremity,  to  that  of 
the  perforans  towards  the  upper  third  of  the  metatarsal  region — termination. 

Relations. — The  muscular  portion  responds  :  in  front,  to  the  perforans,  the 
popliteus,  and  the  posterior  tibial  artery  ;  behind,  to  the  gastrocnemius  and  the 
perforatus.  The  tendon,  at  first  lodged  in  a  muscular  channel  in  the  perforans 
and  covered  by  the  tibial  aponeurosis,  afterwards  enters  a  tortuous  sheath  at  the 
inner  side  of  the  tai-sus,  and  which  is  formed  by  the  groove  that  inchnes  behind 
the  infero-internal  tuberosity  of  the  tibia. 

Action. — It  is  a  congener  of  the  deep  flexor. 


872 


THE  MUSCLES. 


Differential  Characters  in  the  Muscles  of  the  Leg  in  the  other  Animals. 
1.  Anterior  Tibial  Region. 


A.  Ruminants. 


Fi^.  205. 


external  muscles  of  the  leg  of 
the  ox. 


1,  Originating  tendon  of  the  muscle  which 
represents  the  anterior  extensor  of  the 
phal.inges  and  the  flexor  metatarsi  in 
the  horse ;  2,  its  flexor  fasciculus  ;  5, 
that  which  forms  the  common  extensor 
of  the  digits ;  5',  the  tendon  of  this 
fasciculus  ;  6,  its  terminal  bifurcation  ; 
3,  the  long  lateral  peroneus;  3',  its 
tendon;  4,  origin  of  the  anterior  tibial 
(the  muscular  portion  of  the  flexor 
metatarsi  in  the  horse)  ;  7,  proper  ex- 
tensor of  the  external  digit  (short 
lateral  peroneus);  8,  its  tendon  ;  9,  its 
insertion  into  the  second  phalanx  ;  10, 
its  insertion  into  the  third  phalanx  ;  11, 
external  belly  of  the  gastrocnemius ; 
ir,  its  tendon  ;  12,  soleus;  13,  tendon 
of  the  perforatus  ;  14,  perforans  ;  14', 
its  tendon;  15,  suspensorj'  ligament  of 
the  fetlock;  16,  the  band  it  gives  off 
to  the  perforatus  tendon ;  17,  that 
which  it  sends  to  the  proper  extensor 
of  the    external    digit 


Among  these  animals,  the  Ox  presents: 

1.  A  complex  muscle,  which  is  represented  in  the 
Horse  by  the  anterior  extensor  of  the  phalanges,  and 
the  tendon  of  the  flexor  metatarsi.  Single  at  its 
superior  extremity,  which  begins  by  a  tendon  arising 
from  the  digital  fossa  situated  between  the  trochlea 
and  the  external  condyle  of  the  femur  (Fig.  205,  1), 
this  muscle  comprises  in  its  middle  part  three  fleshy 
divisions,  which  are  terminated  inferiorly  by  tendons. 

One  of  these  divisions,  situated  in  front  of,  and 
within  the  other  two,  has  its  tendon  prolonged  to  the 
extremity  of  the  principal  metatarsal  bone,  and  is  also 
inserted  into  the  cuneiform  bones.  It  is  a  flexor  of 
the  metatarsal  region,  and  replaces  the  tendon  which 
performs  this  function  in  Solipeds  (Fig.  205,  2). 

The  second,  placed  external  to  the  preceding,  con- 
stitutes a  common  extensor  of  the  digits,  the  tendon  of 
which  cumports  itself  exactly  like  that  of  the  anterior 
limb  (Fig.  205,  5,  5',  6). 

The  third,  concealed  by  the  other  two,  forms  the 
proper  extensor  of  the  internal  digit,  and  resembles  its 
fellow  in  the  fore  extremity. 

2.  An  anterior  tibhd  muscle  (muscular  portion  of 
the  flexor  metatarsi  of  the  Horse).  It  is  a  triangular, 
muscular  body,  lodged  in  the  antero-external  fossa 
of  the  tibia,  into  the  upper  part  of  wliich  it  is  in- 
serted, and  is  succeeded  by  a  tendon  that  commences 
towards  the  middle  of  the  tibia.  This  tendon  passes 
through  a  ring  pierced  iu  the  tendon  of  the  muscle 
that  represents  the  tendinous  portion  of  the  flexor 
metatarsi ;  it  then  deviates  inwards,  and  is  fixed  into 
the  cuneiform  bones  and  superior  extremity  of  the 
principal  metatarsal  bone  (Fig.  205.  4). 

3.  A  proper  extensor  of  the  external  digit  (lateral 
extensor  of  the  phalanges  in  Solipeds,  the  peroneus 
brevis  lateralis  in  Man),  the  fleshy  body  of  which  is 
altogether  similar  to  that  of  the  analogous  muscle 
in  the  Horse,  and  is  terminated  by  a  long  tendon 
which  resembles  that  of  the  proper  extensor  of  the 
internal  digit  (Fig.  205,  7,  8,  9,  10). 

4.  A  muscle  which  represents  the  peroneous  hngtis 
in  Man,  and  of  which  in  Solipeds  there  is  not  a  trace. 
This  muscle  commences  by  a  short,  conical,  muscular 
body  in  front  of  the  supero-external  tuberosity  of  the 
tibia,  and  terminates  by  a  long  tendon,  the  direction 
of  which  is  as  follows  :  included  at  first,  like  the 
muscular  portion,  between  the  proper  extensor  of  the 
external  digit  and  the  triple  muscular  fasciculus 
already  described,  it  arrives  on  the  outside  of  the 
tarsus,  passes  through  the  fibrous  groove  of  the  proper 
extensor,  where  it  is  enveloped  by  a  special  synovial 
membrane,  passes  over  the  latter  in  slightly  crossing 
its  direction,  and  is  inflected  at  first  backwards,  then 
outwards,  by  insinuating  itself  underneath  the  ex- 
ternal tibio-tarsal  ligament,  and  the  calcaneo-meta- 
tarsal  and  the  posterior  tarso-metatarsnl  lijjaments, 
which  retain  it  in  a  chaimel  on  the  inferior  face  of 


18,   the   pedal 
muscle  ;   19,  the  insertion  of  the  biceps  femoris  on  the  patella,  and  its  external  ligament. 


MUSCLES  OF  THE  POSTERIOR  LIMBS.  373 

the  cuboido-scaphoid  bone.  It  is  finally  inserted  into  the  deep  face  of  the  second  cuneiform 
bone,  and  the  external  side  of  the  superior  extremity  of  the  metatarsus,  by  a  small  branch 
detached  from  the  outer  side  of  the  principal  tendon. 

All  these  muscles  are  similarly  disposed  in  the  Sheep  and  Goat. 

B.  Pig.— The  anterior  tibial  muscles  of  this  animal  resemble  those  of  Ruminants,  with  the 
exception  of  some  peculiarities  of  secondary  importance,  among  which  the  following  may  be 
cited : 

The  muscular  fasciculus  which  replaces  the /e.cor  metatarsi  in  the  Horse,  terminates  on  the 
scaphoid  and  the  second  cuneiform  bone.  The  common  extensor  of  the  digits  has  four  tendons — 
one  for  each  digit.  The  proper  extensors  have  two  each — one  for  the  small  digit,  and  the  other 
for  the  great.  The  anterior  tibial  passes  to  the  second  cuneiform  bone.  The  peroneus  longus 
lateralis  is  inserted,  by  its  tendon,  into  the  upper  extremity  of  the  internal  metatarsus. 

C.  Camivora.— Four  muscles  are  described  in  these  animals  :  1.  An  anterior  tibial.  2. 
A  long  common  extensor  of  the  digits.  3.  A  long  lateral  peroneus.  4.  A  short  lateral 
peroneus. 

1.  Anterior  tibial. — Situated  in  front  of  the  tibia,  and  more  voluminous  than  tlie  common 
extensor  of  the  digits,  the  superior  extremity  of  which  it  covers,  this  muscle  has  its  origin  on 
the  crest  and  external  tuberosity  of  the  tibia.  It  receives,  near  the  inferior  third  of  this  bone, 
an  extremely  thin  muscular  baud  which  proceeds  from  the  fibula,  and  which  we  may  with 
justice  compare  to  the  proper  extensor  of  the  big  toe  in  Man.  Then  it  terminates  by  a  tendon 
on  the  metatarsal  bone  of  the  internal  digit;  when  this  bone  is  connected  with  a  digital 
region,  the  third  phalanx  receives  a  particular  branch  from  this  tendon,  which  represents  the 
tendinous  portion  of  the  small  proper  extensor  fasciculus  annexed  to  the  anterior  tibial.  This 
muscle  responds:  in  front,  to  the  tibial  aponeurosis;  inwards  and  backwards,  to  tiie  tibia; 
outwards,  to  the  common  extensor  of  the  digits.  Its  tendon  is  fixed  in  the  bend  of  the  liock 
by  a  fibrous  band,  the  arrangement  of  which  is  singular  enough  to  deserve  mention  here. 
Attached  in  front  of  the  inferior  extremity  of  the  tibia,  this  band  gives  origin,  by  its  internal 
extremity,  to  a  strong  ligament  which  passes  under  the  tendon  of  the  anterior  tibial  muscle  to 
reach  the  anterior  face  of  the  tarsus,  wliere  it  unites  closely  with  the  capsular  ligament  of  this 
region,  and  terminates  on  the  superior  extremity  of  tlie  metatarsal  bone  of  the  middle  digit. 
This  ligament  binds  the  inferior  extremity  of  the  tibia  to  tlie  metatarsus,  and  prevents  undue 
extension  of  the  tibio-tarsal  articulation.  It  is,  perhaps,  the  representative  of  the  tendon  of 
the  anterior  tibial  reginn  in  the  Horse. 

2.  Long  common  extensor  of  the  digits. — This  muscle  is  composed  of  a  fusiform  fleshy  body, 
and  a  quadrifurcated  tendon.  The  flesliy  body,  situated  beneath  the  tibial  aponeurosis, 
between  the  anterior  tibial  and  the  lateral  peroneal  muscles,  covers  the  external  face  of  the 
tibia  and  the  small  fasciculus  of  tiie  proper  extensor  of  the  thumb;  it  originates  by  a  short 
and  strong  tendon,  from  the  inferior  extremity  of  the  femur,  between  the  external  condyle  and 
the  trochlea.  The  tendon  is  continuous  with  the  inferior  extremity  of  the  fleshy  portion, 
passes  beneath  the  band  of  the  anterior  tibial,  through  another  fibrous  ring  at  the  cuboid  bone, 
and  is  inserted,  by  its  four  terminal  branches,  into  the  four  large  digits,  in  the  same  manner 
as  the  analogous  tendon  in  the  fore  limb. 

3.  Long  lateral  peroneus. — This  muscle  is  composed  of  a  very  short,  conical,  fleshy  portion, 
succeeded  by  a  long  tendon.  Tlie  former  originates  in  front  of  the  tuberosity  of  the  supero- 
external  tuberosity  of  the  tibia,  and  does  not  appear  to  have  any  connection  with  the  fibula. 
Included  between  the  common  extensor  of  the  digits  and  the  short  lateral  peroneus,  it  is 
covered  by  the  tibial  aponeurosis,  and  covers  the  anterior  tibial  vessels.  The  tendon  descends 
parallel  with  tlie  fibula  to  its  inferior  extremity,  over  which  it  glides  in  becoming  inflected. 
On  reaching  the  cuboides,  t  enters  a  groove  excavated  on  its  external  surface,  gives  off  a  short 
isolated  branch  to  the  superior  extremity  of  the  first  metatarsal  bone,  afterwards  crosses  trans- 
versely the  direction  of  the  tarsus  in  passing  behind  the  inferior  row  of  bones,  and  terminates 
on  the  metatarsus  of  the  thumb.  On  its  way,  behind  the  cuboides,  this  tendon  gives  ofi"  another 
branch,  which  we  have  every  reason  to  believe  is  constantly  present ;  it  is  a  short,  interosseous 
fasciculus,  that  at  first  penetrates  between  the  cuboides  and  the  external  metatarsal  bone,  then 
between  the  latter  and  the  second  metatarsal. 

This  muscle  carries  the  inferior  extremity  of  the  limb  outwards,  and  when  the  foot  Is  much 
extended  it  may  act  as  a  flexor. 

4.  Short  lateral  peroneus. — In  Camivora,  this  muscle  is  formed  by  two  fasciculi — a  superior 
and  inferior,  which  may  be  described  as  two  distinct  muscles. 

The  superior  fasciculus  is  a  very  weak  muscular  portion,  attached  to  the  upper  third  of  the 
anterior  border  of  the  fibula,  and  a  funicular  tendon  succeeding  its  inferior  extremity  about 
the  middle  of  the  tibia.     Tiiis  tendon  glides  over  the  inferior  extremity  of  the  fibula,  behind 


374  THE  MUSCLES. 

the  long  lateral  peroneus,  which  it  passes  under  ami  crosses,  in  descending  to  the  phalanges 
of  the  external  digit,  where  it  is  united  to  the  tendinous  branch  of  the  common  extensor 
belonging  to  this  digit. 

The  inferior  fasciculus  has  its  origin  on  the  anterior  border  and  external  aspect  of  the 
peroneus,  by  penniform  fibres,  which  join  a  short,  but  more  voluminous  tendon  than  that  of 
the  preceding  fasciculus.  This  tendon,  with  tlie  last,  enters  the  posterior  groove  in  the  fibula, 
and  is  attached,  by  its  inferior  extremity,  to  the  upper  end  of  the  external  metatarsus,  outside 
the  branch  furnished  by  the  long  lateral  peroneus  to  that  bone. 

The  superior  fasciculus  acts  as  a  proper  extensor  of  the  external  digit.  The  inferior  is  an 
abductor  of  the  foot. 

2.  Posterior  Tibial  Region. 

A.  Ruminants.— In  the  Ox,  Sheep,  and  Goat,  tlie  muscular  portion  of  the  perforatum 
is  thicker  than  in  Snlipeds.  The  portion  of  the  per/oratis  which  represents  the  tibialis  posticus 
is  also  better  defined  than  in  them ;  it  is  lodged  in  a  depression  on  the  principal  portion,  and 
can  easily  be  traced  from  the  supero-external  surface  of  the  tibia,  where  it  originates.  The 
tendon  does  not  differ  from  that  in  the  fore  limb;  but  the  bands  which  descend  from  the 
metatarsus  to  the  heels,  to  be  united  witli  the  two  terminal  branches  of  this  tendon,  are  much 
smaller  than  those  in  tiie  metacarpal  region. 

In  the  Camel,  the  popliteus  is  altogether  confined  to  the  upper  and  posterior  part  of  the 
tibia.  The  perforatus  is  almost  exclusively  tendinous ;  in  its  deeper  portion  there  is  a  slight 
expansion  in  which  there  are  a  few  muscular  fibres.  The  perforans  has  a  very  small  fusiform 
muscle  ;  its  tendon  glides  on  the  internal  face  of  the  oscalcis,  in  a  slight  depres.sion  representing 
the  tarsal  bursa;  it  unites  with  the  oblique  flexor,  and  comports  itself  as  in  the  anterior  limb. 
The  oblique  flexor  of  the  phalanges  is  remarkable  for  its  volume;  instead  of  being  an  accessory 
to  the  deep  flexor,  as  in  the  other  species,  it  alone  forms  the  principal  head  of  the  perforans 
tendon,  the  essential  fleshy  body  of  which  is  found,  on  the  contrary,  to  be  represented  in  the 
majority  of  the  other  animals,  by  the  analogue  of  the  long  flexor  of  the  great  toe. 

B.  Carnivora.— The  soleus  is  absent  in  the  Dog,  but  it  is  found  in  the  Cat.  The 
muscular  body  of  the  perforatus  is  prismatic,  voluminous,  and  entirely  blended— in  its  upper 
two-thirds  at  least— with  the  external  head  of  the  gastrocnemius;  these  two  muscles  have 
therefore  a  common  origin.  The  tendon  is  quadrifurcated,  as  in  the  anterior  Umb ;  it  offers 
on  its  surface,  shortly  before  its  division,  several  thin  muscular  bands,  traces  of  the  fleshy 
portion  of  the  common  short  muscle  of  the  toes  in  Man.  Several  of  these  bauds  come  from 
the  perforans  tendon,  and  all  pass  to  the  four  terminal  branches  of  the  muscle.  The  terminal 
tendon  of  the  perforans  is  divided  into  four  or  five  branches,  one  for  each  digit. 

The  posterior  tibial  is  not  united,  inferiorly,  to  this  tendon,  but  constitutes  a  perfectly 
distinct  muscle  situated  between  the  deep  and  oblique  flexors  of  the  phalanges.  Formed  by  a 
very  small  fleshy  body  and  a  long  thin  tendon,  it  arises  above  the  peroneus,  from  the  posterior 
surface  of  the  tibia.  Its  tendon  lies  beside  that  of  the  oblique  flexor,  and  with  it  enters  the 
groove  behind,  and  within  the  inferior  extremity  of,  tlie  tibia.  Enveloped  by  a  synovial  mem- 
brane proper  to  its  passage  through  this  groove,  this  tendon  soon  leaves  it  to  pass  to  the  free 
surface  of  the  posterior  tarso-metatarsal  ligament,  with  which  it  is  blended  towards  the  middle 
of  the  tarsus. 

Comparison  of  the  Muscles  of  the  Leg  of  Man  with  those  of  Animals. 

In  Man,  the  muscles  of  the  leg  are  divided  into  three  regions :  an  anterior,  external,  and 
posterior. 

1.  Anterior  Region  (Fig.  20t5). 
This  includes  three  muscles  : 

1.  The  anterior  tibial,  which  corresponds  to  the  fleshy  portion  of  the  flexor  of  the  meta- 
tarsus, and  the  imperforate  tendon  of  which  is  fixed  into  the  first  cuneiform. 

2.  The  common  long  extensor  of  the  toes,  which  represents  the  anterior  extensor  of  the 
phalanges  of  the  Horse.  This  muscle  is  attached,  above,  to  the  external  tuberosity  of  the 
tibia  and  the  upper  three-fourths  of  the  inner  face  of  tlie  fibula :  its  tendon  divides  into  two 
fasciculi,  the  internal  of  which  furnishes  a  branch  to  the  second,  third,  and  fourth  toes,  and 
tiie  external  goes  to  the  fifth. 

3.  The  proper  extensor  of  the  great  toe,  represented  in  the  Dog  by  a  small  fasciculus 
blended  with  the  anterior  tibial,  is  an  elongated  semi-penniform  muscle  that  arises  from  the 
inner  face  of  the  fibula  and  the  interosseous  ligament,  and  terminates  on  the  second  phalanx  of 
the  great  toe,  after  receiving  the  pedal  tendon  (extensor  brevis  digitorum). 


MUSCLES  OF  THE  POSTERIOR  LIMBS. 


375 


2.  External  Kkgion  (Fig.  206). 

This  region  is  only  composed  of  two  muscles  :  the  long  and  short  peroneus. 

The  first,  which  does  not  exist  in  Solipeds,  is  a  penniform  muscle  attached  to  the  upper 
third  of  the  fibula,  the  external  tuberosity  of  the  tibia,  and  the  internal  face  of  the  tibial 
aponeurosis,  by  the  superior  extremities  of  its  muscular  fibres.  The  flat  tendon  which  termi- 
nates it  is  fixed  to  the  outer  portion  of  the  base  of  the  first  metatarsal. 

The  second  corresponds  to  the  lateral  extensor  of  the  phalanges  of  the  Horse,  and  is  found 


Fig.  206. 


Fi^.  207. 


,5 


SUPERFICIAL   POSTERIOR   MUSCLES    OF   THE 
HUMAN    LEG. 

1,  Biceps  forming  outer  ham-string ;  2,  ten- 
dons forming  ianer  ham-string ;  3,  popli- 
teal space  ;  4,  gastrocnemius  ;  5,  5,  soleus ; 
6,  tendo-Achilles  ;  7,  posterior  tuberosity 
of  OS  calcis  ;  8,  tendons  of  peroneus  longus 
and  brevis  passing  behind  the  outer  ankle  ; 
9,  tendons  of  tibialis  posticus  and  flexor 
longus  digitorum  passing  into  the  foot 
behind  the  inner  ankle. 


OF  THE   HUMAN  LEG   (ANTERIOR 
TIBIAL   REGION). 

1,  Quadriceps  extensor  inserted  into  the  pa- 
tella (the  figure  is  on  the  tendon  of  the 
rectus,  the  vastus  internus  and  externus 
being  on  each  side) ;  2,  subcutaneous  sur- 
face of  the  tibia  ;  3,  tibialis  anticus ;  4, 
extensor  longus  digitorum ;  5,  extensor 
proprius  pollicis  ;  6,  peroneus  tertius ;  7, 
peroneus  longus;  8,  peroneus  brevis;  9,  9, 
borders  of  the  soleus  muscle;  10,  part  of 
the  inner  belly  of  the  gastrocnemius  ;  11, 
extensor  brevis  digitorum  (the  tendon  in 
front  of  the  cipher  is  that  of  the  peroneus 
tertius ;  that  behind  it,  the  peroneus  brevis). 

in  all  animals.  It  is  penniform,  and  is  attached  above,  by  its  fleshy  fibres,  to  the  lower  two- 
thirds  of  the  external  face  of  the  fibula ;  below,  by  its  tendon,  to  the  upper  extremity  of  the 
fifth  metatarsal. 

These  two  muscles  determine  very  complicated  movements  in  the  region  of  the  foot 

3.  Posterior  Region  (Fig.  207). 
The  posterior  tibial  muscles  form  two  layers :  a  superficial  and  a  deep. 


876  TEE  MUSCLES. 

The  first  comprises  the  crural  triceps  and  the  plantarie.  The  triceps  itself  is  composed  ol 
the  gastrocnemius,  of  which  we  will  say  nothing,  and  the  soleus.  The  latter  is  flattened  from 
before  to  behind,  attached  to  the  upper  third  of  tlie  fibula,  the  oblique  line  of  the  tibia,  and 
the  middle  tliird  of  the  inner  border  of  this  bone,  and  terminated  by  an  aponeurotic  lamina 
which  is  blended  with  the  tendo-Achilles.  The  plantaris  is  formed  by  a  small  fusiform 
muscular  body,  situated  beneath  the  external  gemellus,  then  by  a  long  slender  tendon,  which 
is  confounded  with  the  inner  border  of  the  tendo-Achilles,  or  is  inserted  into  the  os  calcis. 

The  deep  layer  is  composed  of  four  muscles  : 

1.  The  popliteus,  which  in  its  attachments  and  position  resembles  that  of  animals. 

2.  The  common  long  flexor  of  the  toes,  corresponding  to  the  oblique  flexor  of  animals.  It  is 
an  elongated  penniform  muscle,  fixed  above  to  the  oblique  line  and  middle  third,  of  the 
posterior  face  of  the  tibia.  Its  tendon  is  inflected  beneath  the  external  malleolus,  passes  in 
front  below  the  astragalus,  receives  the  accessory  of  the  long  flexor,  and  then  divides  into  four 
branches  for  the  four  lesser  toes. 

3.  The  posterior  tibial,  represented  by  a  portion  of  the  perforans  of  animals ;  its  tendon  is 
reflected  beneath  the  internal  malleolus  of  the  tibia,  and  is  attached  to  the  scaphoid  process. 

4.  The  proper  long  flexor  of  the  great  toe,  also  represented  by  a  portion  of  the  perforans. 
This  muscle  is  voluminous  and  prismatic,  and  is  attached  above  to  the  lower  two-thirds  of  the 
posterior  face  of  the  fibula.  Its  tendon  is  reflected  inwards  on  the  astragalus  and  the  groove 
in  the  os  calcis,  crosses  the  tendon  of  the  common  long  flexor,  and  terminates  on  the  posterior 
extremity  of  the  third  phalanx  of  the  great  toe. 

Muscles  of  the  Posterior  Foot. 

In  Solipeds  are  found  :  1.  Tivo  lumhrici  and  hvo  ifiterosseous  muscles, 
corresponding  to  those  of  the  anterior  limb.     2.  A  pedal  muscle. 

Pedal  Muscle  (Extensor  Pedis  Brevis,  Extensor  Brevis  Digitorum). 

Synonym. — The  tarso-prephalangeus  of  Girard. 

This  is  a  small  riband-shaped  fasciculus,  situated  in  front  of  the  principal  meta- 
tarsal bone,  beneath  the  extensors  of  the  phalanges.  It  is  attached,  by  its  inferior 
extremity,  to  the  internal  surface  of  the  tendon  common  to  these  two  muscles,  and 
by  its  upper  extremity  to  the  lower  end  of  the  os  calcis  (and  astragalus).  It  aids 
in  extending  the  digit  (flexing  the  hock,  and  probably  keeping  the  tendons  tense.) 
Differential  Characters  in  the  Muscles  of  the  Posterior  Foot  in  the  other  Animals. 

A.  Huminants. — This  is  the  only  muscle  in  the  region  of  the  foot  met  with  in  Rumi- 
nants. It  is  attached,  iiiferiorly,  to  the  tendon  of  the  common  extensor  and  that  of  the  proper 
extensor  of  the  internal  digit. 

B.  Pig. — This  animal  possesses:  1.  A  pedal  muscle  attached,  below,  to  the  two  branches  of 
the  common  extensor  of  the  large  digits.  2.  Four  interosseous  metatarsal  muxcles,  whicli  do  not 
appear  to  diff'er  in  their  general  arrangement  from  the  metacarpal  interosseous  muscles. 

C.  Carnivora. — In  the  Dog  and  Cat  there  exist  in  the  region  of  the  posterior  foot : 

1.  A  pedal  muscle,  composed  of  three  fasciculi  which  have  their  origin  either  fiom  the 
inferior  extremity  of  the  os  calcis,  or  from  the  tendinous  sheaths  in  the  bend  of  the  hock  ;  they 
terminate  on  the  second,  third,  and  fourth  digits,  by  small  tendons  joined  to  the  branches  of 
the  common  extensor. 

2.  Tlie  muscular  digitations  annexed  to  the  tendon  of  the  perforatus,  traces  of  the  fleshy 
portion  of  the  ^exor  brevis  digitorum  of  Man. 

3.  A  flexor  pedis  accessorius,  or  perforans,  a  small  undeveloped  muscle  commencing  outside 
the  tarsus,  and  terminating  by  a  very  delicate  aponeurosis  on  the  posterior  face  of  the  perforans 
tendon. 

4.  Two  or  three  pale  and  rudimentary  bands,  situated  inside  the  tarsus  and  near  the 
internal  digit.     These  are  *he  vestiges  of  the  muscles  proper  to  the  great  toe  in  Man. 

5.  An  adductor  of  the  little  toe  (abductor  minimi  digit)  is  a  thin,  elongated  muscle,  carried 
obliquely  from  the  posterior  tarso-metatarsal  ligament  to  the  internal  side  of  the  first  phalanx 
of  that  digit. 

6.  Four  interosseous  metatarsal  muscles,  resembling  the  analogous  muscles  of  the  metacarpal 
region. 

7.  LxLmhrici  similar  to  those  of  the  anterior  limb. 


MUSCLES  OF  THE  POSTERIOR   LIMBS. 


377 


Comparison  of  the  Muscles  of  the  Foot  in  Man  with  those  of  Animals. 

In  Man,  there  are  distinguished  the  muscles  of  the  dorsal  region,  the  plantar  region,  and 
the  interosseus  muscles. 

I.  Dorsal  Eegion. 

This  only  contains  one  muscle,  the  pedal  {extensor  hrevis  digitorum).  It  is  attached, 
behind,  to  the  antero-external  part  of  the  upper  face  of  the  os  calcis,  by  several  aponeurotic 
layers ;  its  fleshy  fasciculi,  four  in  number,  are  prolonged  by  as  many  tendons  destined  to  the 
first  four  toes ;  three  of  them  pass  along  with  the  tendons  of  the  common  extensor. 

2.  Plantar  Region. 

This  is  subdivided  into  three  regions :  a  middle,  internal,  and  external. 

The  first  comprises  :  1,  The  common  short  flexor  of  the  toes,  which  is  represeuted  in  Soli- 


Fig.  209. 


FIRST  LAYER  OF  PLANTAR    MUSCLES  OF 
HUMAN  FOOT. 

1,  Os  calcis  ;  2,  posterior  part  of  plantar  fascia 
divided  transversely  ;  3,  abductor  pollicis ; 
4,  abductor  minimi  digitii ;  5,  flexor 
brevis  digitorum  ;  6,  tendon  of  flexor 
longus  pollicis  ;  7,  7,  lumbricales. 


THIRD    AND    PART    OF    SECOND    LATER   OF 
PLANTAR   MUSCLES    OF    HUMAN   FOOT. 

1,  Incised  plantar  fascia ;  2,  musculus  acces- 
sorius;  3,  tendon  of  flexor  longus  digi- 
torum ;  tendon  of  flexor  longus  pollicis  ; 
5,  flexor  brevis  pollicis  ;  6,  adductor  pol- 
licis ;  7,  flexor  brevis  minimi  digitii ;  8, 
transversus  pedis ;  9,  interossei  muscles, 
plantar  and  dorsal ;  10,  convex  ridge 
formed  by  the  tendon  of  the  peroneus  lon- 
gus in  its  oblique  course  across  the  foot. 


peds  by  a  portion  of  the  perforatus.  It  is  attached  to  the  infero-internal  tuberosity  of  the 
03  calcis,  and  to  the  upper  face  of  the  middle  plantar  aponeurosis.  It  has  four  tendons,  which 
are  inserted  into  the  second  phalanges  of  the  first  four  toes,  after  forming  rings  through  which 
pass  the  tendons  of  the  common  long  flexor. 

2.  The  accessory  of  the  long  flexor,  the  fibres  of  which  pass  to  the  tendons  of  the  common 
flexor. 

3.  The  lumbrici,  four  in  number,  and  analogous  to  those  of  the  hand. 

The  internal  plantar  region  is  composed  of  three  muscles,  which  are  found  in  a  rudimentary 
condition  in  the  Dog. 

L  The  short  adductor  of  the  great  toe,  which  extends  fiom  the  internal  tuberosity  of  the  os 
calcis  to  the  internal  sesamoid  and  the  first  phalanx  of  the  great  toe. 


878  THE  MUSCLES. 

2.  The  short  flexor  of  the  great  toe,  which  arises  from  the  third  cuneiform  and  the  tendon  of 
the  posterior  tibial,  and  terminates  by  two  branches  on  the  external  sesamoid  and  the  internal 
Besamoid  of  the  great  toe. 

3.  Tlie  short  adductor  of  the  great  toe,  a  muscle  formed  by  two  fasciculi,  and  having  a 
common  termination  on  the  external  sesamoid.  One  of  these  fasciculi  arises  from  the  inferior 
face  of  the  cuboides,  the  third  cuneiform,  and  the  base  of  the  third  and  fourth  metatarsal ;  it 
has  been  formerly  described  as  the  oblique  adductor.  The  other  has  its  origin  from  the 
inferior  face  of  the  three  last  metatarso-phalangeal  articulations :  this  has  also  been  called 
the  transverse  adductor. 

The  external  plantar  region  likewise  comprises  three  muscles,  which  are — 

1.  The  short  abductor  of  the  little  toe,  which  is  detached  from  the  internal  tuberosity  of  the 
08  calcis.  and  is  inserted  into  the  external  portion  of  the  first  phalanx  of  the  little  toe. 

2.  Tlie  short  flexor  of  the  little  toe  is  attached,  behind,  to  the  sheath  of  the  long  peroneus 
and  to  the  process  of  the  fifth  metatarsal ;  in  front,  to  the  external  part  of  the  first  phalanx  of 
the  little  toe. 

3.  The  opponens  of  the  little  toe,  concealed  beneath  the  preceding,  is  inserte  1  at  one  end  to 
the  sheath  of  the  long  peroneus,  and  at  the  other  to  the  external  border  of  the  fifth  metatarsal. 

3.  Interosseous  Muscles. 
These  are  divided  into  dorsal  and  plaritar  interoseei.    Their  disposition  is  nearly  the  same 
as  in  the  hand. 


CHAPTER  III. 
THE    MUSCLES   IN   BIRDS. 


In  Birds,  we  find  the  majority  of  the  muscles  already  described  ;  though  they 
are  appropriate  by  their  form,  volume,  arrangement,  etc.,  to  the  particular 
conformation  of  the  skeleton  in  these  animals. 

To  undertake,  in  this  essentially  practical  work,  a  special  description  of  all 
these  muscles,  would  be  to  depart  from  the  object  aimed  at ;  and  we  therefore 
confine  ourselves  to  those  points  which  present  most  interest,  so  far  as  animal 
mechanics  is  concerned. 

1.  Tendons. — The  tendons  in  birds  present  in  the  inferior  limbs  and  at  the 
extremity  of  the  wings  an  amount  of  ossification  more  or  less  extensive  along 
their  course.  This  transformation  of  the  fibrous  tissue  of  the  muscles  is  not  the 
effect  of  senility,  for  it  is  noticed  in  very  young  animals. 

The  tendons,  in  losing  the  greater  part  of  their  elasticity,  doubtless  gain  in 
tenacity ;  and  this  allows  them  to  transmit  to  the  bony  levers  the  muscular 
efforts  in  a  more  integral  manner. 

It  is  also  observed  that  the  partial  ossification  of  the  tendons  does  not 
exclusively  belong  to  the  limbs  ;  for  it  is  not  rare  to  meet  with  this  change  m 
other  regions,  as  in  the  neck  of  wading  birds.  In  the  museum  of  the  Vetermary 
School  at  Lyons  is  the  skeleton  of  a  heron  which  shows  this  peculiarity  in  the 
highest  degree  ;  the  cervical  vertebrae  are  roughened  by  a  multitude  of  filiform 
bony  stylets,  all  directed  backwards,  and  which  have  originated  from  the  ossifi- 
cation of  the  tendinoiLs  fibrillae  annexed  to  the  muscles  of  the  cervical  region. 

2.  The  Pectoral  Muscles. — The  two  alternative  movements  which  produce 
flight — the  elevation  and  depression  of  the  wings — being  due  to  the  action  of 
the  pectoral  muscles,  these  merit  special  notice. 

The  superficial  or  great  pectoral,  "  which  alone  weighs  heavier  than  all  the 


THE  MUSCLES  IN  BIRDS.  379 

other  muscles  of  the  bird  put  together,  is  attached  to  the  furculum,  to  the  great 
ridge  of  the  sternum,  and  to  the  last  ribs  ;  it  is  inserted  into  the  very  salient 
rugged  outline  of  the  humerus.  It  is  by  this  muscle  that  birds  are  able  to  give 
those  powerful  strokes  of  the  wings  which  are  necessary  in  flight." 

The  deep  or  small  pectoral  is  "  placed  in  the  angle  formed  by  the  body  of  the 
sternum  and  its  crest,  and  in  the  interval  between  the  furculum  and  the  coracoid 
bone.  Its  tendon  passes  through  the  foramen  formed  by  the  union  of  the 
furculum,  the  coracoid  bone,  and  the  scapula,  as  over  a  pulley  ;  it  is  inserted 
above  the  head  of  the  humerus,  which  it  raises.  It  is  by  means  of  this  arrange- 
ment that  nature  has  been  able  to  place  an  elevator  and  depressor  at  the  inferior 
surface  of  the  trunk  so  far  from  the  centre  of  gravity,  without  which  the  bird 
would  have  been  liable  to  lose  its  equihbrium  and  tumble  over  head  foremost  in 
the  air." ' 

Cuvier,  adopting  the  nomenclature  of  Vicq-d'Azyr,  called  this  muscle  the 
middle  pectoral,  and  he  gave  the  name  of  small  pectoral  to  a  triangular  fasciculus 
which  leaves  the  lateral  angle  of  the  sternum  and  the  base  of  the  coracoid  bone, 
to  be  inserted  under  the  head  of  the  humerus.  In  our  opinion,  this  tendon  does 
not  belong  to  the  pectoral  region,  but  to  that  of  the  shoulder  ;  and,  with  J.  F. 
Meckel,  we  are  inclined  to  consider  it  as  the  curaco-humeralis,  which  has  followed 
the  coracoid  process  in  its  development.^ 

3.  The  Diaphragm. — "  In  Birds,  the  diaphragm  is  so  differently  disposed 
from  what  it  is  in  the  higher  Yertebrata,  that  its  existence  has  been  successively 
described  and  misunderstood,  admitted  and  refuted,  and  is  still  looked  upon  as 
problematical  by  a  large  number  of  anatomists.  Nevertheless,  this  muscle  exists, 
and  its  development  is  in  perfect  harmony  with  the  importance  of  its  functions. 
It  is  composed  of  two  planes,  which  at  their  origin  are  confounded  with  each 
other,  but  soon  become  separated  and  pursue,  one  a  transverse,  the  other  an 
oblique  direction.  The  transverse  plane  is  triangular  in  form,  and  is  carried 
horizontally  from  the  right  to  the  left  ribs  against  the  inferior  surface  of  the 
lungs.  The  oblique  plane  is  convex  in  front,  concave  behind,  and  extends  from 
the  dorsal  aspect  of  the  spine  to  the  sternum,  dividing  the  cavity  of  the  trunk 
into  two  secondary  cavities — the  thorax  and  abdomen. 

"  In  Birds,  as  in  Mammals,  the  diaphragm  is  therefore  intended  to  perform 
two  principal  functions  ;  but  to  do  this  perfectly  in  the  former,  it  is  doubled. 
So  far,  then,  from  this  inspiratory  muscle  being  absent  in  birds,  or  from  its 
existing  in  a  rudimentary  degree,  they  are  really  provided  with  two  diaphragms  : 
1.  A.  pulmonary  diaphragm,  which  presides  in  the  dilatation  of  the  lungs.  2. 
A  thoracic  abdominal  diaphragm,  which  partitions  the  great  cavity  of  the  trunk, 
and  concurs  in  the  inspiration  of  the  air  by  dilating  the  large  aerial  reservoirs 
lying  at  its  posterior  surface.  Of  these  two  muscular  planes,  the  first  is  analogous 
to  that  portion  of  the  diaphragm  which,  in  Man  and  the  Mammalia,  is  inserted 

'  Cuvier,  Lemons  d'Anntomie  Compar^e. 

*  E.  Geoffrey  Saint- Hilaire,  in  his  memoir  on  the  bones  of  the  sternum  (Philonophie 
Anatomique,  vol.  i.  p.  89),  in  comparing  the  pectoral  muscles  of  Fishes  to  those  of  Birds,  also 
employs  the  nomenclature  of  Vicq-d'Azyr,  and  recognizes  three  pectorals  as  well.  We  are, 
however,  obliged  to  confess  ourselves  as  in  opposition  to  the  great  master  who  has  estal)lished 
rules  to  follow  in  the  classification  of  organs,  in  consequence  of  liis  having  limited  his  com- 
parisons to  the  two  classps  of  Vertebrata  he  had  principally  in  view.  If  he  had  extended  his 
observations  to  the  Mammalia,  and  in  them  sought  for  the  analogue  of  the  pectoralis  parvus, 
he  wonkl  have  discovered  it,  as  we  have  done,  in  the  region  of  the  shoulder,  and  not  in  that  of 
the  sternum. 


THE  MUSCLES. 


into  the  sternum  and  the  ribs  ;  the  second  manifestly  represents  the  pillars  of 
the  diaphragm." 

This  description,  taken  from  the  work  of  Sappey,  an  observer   as  con- 
scientious as  he  is  talented,  gives  a  perfectly  exact  idea  of  this  muscle. 


CHAPTER  IV. 

GENERAL  TABLE   OP  THE   ATTACHMENT   OF  THE 
MUSCLES   IN   SOLIPEDS. 

I.  Vertebral  Column. 

A.  Cervical  Vertebrae. 

1.  Atlas. 

The  atlas  gives  attachment  to  nine  pairs  of  muscles  : — 

a.  By  the  surface  representing  the  spinous  process,  to  the — 

Rectus  capitis  posticus  minor. 
6.  By  its  transverse  processes,  to  the — 

1.  Spleniua. 

2.  Trachelo-mastoideus. 

3.  Obliquus  capitis  anticua. 

4.  Obliquus  capitis  posticus. 

5.  Mastoido-humeralis. 
c.  By  its  body,  to  the — 

1.  Rectus  capitis  anticus  minor. 

2.  Rectus  capitis  lateralis. 

3.  LonguB  colli. 

2.  Axis. 

The  axis  gives  insertion  to  six  pairs  of  muscles  : — 

a.  By  its  spinous  process,  to  the — 

1.  Semispinalis  colli.  , 

2.  Obliquus  capitis  anticus. 

3.  Rectus  capitis  posticus  major. 

b.  By  its  transverse  processes,  to  the — 

1.  Intertransversales  colli. 

2.  Mastoido-humeralis  muscles. 

A7id  by  the  inferior  face  of  its  body,  to  the — 

3.  Lougus  colli. 

8.  Third,  Fourth,  Fifth,  Sixth,  and  Seventh  Cervical  Vertebra. 
These  vertebrae  give  insertion  to  the  following  muscles  : — 

a.  By  their  spinous  processes,  to  the — 

1.  Semispinalis  colli. 

2.  Longissimus  dorsi. 

b.  By  their  articular  tubercles,  to  the — 

1.  Complexus. 

2.  Trachelo-mastoideuB. 

3.  Semispinalis  colli. 

4.  Intertransversales  colli. 


GENERAL   TABLE  OF  THE  ATTACHMENT  OF  MUSCLES  IN  SOLIPEDS.    381 

c.  By  their  transverse  processes,  to  the — 

1.  Angularis  scapulae. 

2.  Splenius  (3rd  and  4th). 

3.  Mastoido-humeralis  (3rd  and  4th). 

4.  Tranaversalis  costarum. 

5.  Semispinalis  colli. 

6.  Longissimus  colli  (inferior  branch). 

d.  And  by  the  inferior  faces  of  their  bodies,  to  the — 

1.  Rectus  capitis  anticus  major. 

2.  Longus  colli. 

B.  Dorsal  Vertebra. 

The  dorsal  vertebrae  give  insertion  : — 

a.  By  their  spinous  processes,  to  the — 

1.  Splenius  (1st  to  5th  or  6th). 

2.  Complexus  (Ist  to  6th). 

3.  Trachelo-mastoideus  (Ist  and  2ud). 

4.  Trapezius. 

5.  Latissimus  dorsi  (4th  to  18th). 

6.  Rhomboideus  (2nd  to  7th). 

7.  Serratus  anticus  (2ud  to  13th). 

8.  Serratus  posticus  (10th  to  18th). 

9.  Longissimus  dorsi. 

10.  Semispinalis  of  the  back  and  loins. 
6.  By  their  transverse  processes,  to  the — 

1.  Complexus. 

2.  Trachelo-mastoideus. 

3.  Longissimus  dorsi. 

4.  Semispinalis  of  the  back  and  loins. 

5.  Levatores  costarum. 

c.  By  their  bodies,  to  the — 

1.  Longus  colli  (Ist  to  6th). 

2.  Psoas  magnus  (17th  to  18th). 

3.  Psoas  parvus  (16th  to  18th). 

C.  Lumbar  Vertebrae. 

The  lumbar  vertebrae  give  insertion  : — 

a.  By  their  spinous  processes,  to  the— 

1.  Latissimus  dorsi. 

2.  Serratus  posticus  (Ist  to  3rd). 

3.  Longissimus  dorsi. 

4.  Semispinalis  of  the  back  and  loins. 

b.  By  their  articular  tubercles,  to  the  — 

1.  Longissimus  dorsi. 

2.  Semispinalis  of  the  back  and  loins. 

c.  By  their  transverse  processes,  to  the — 

1.  Psoas  magnus. 

2.  Quadratus  lumborum. 

3.  Intertransversales  of  the  loins. 

4.  Transversus  abdominis. 

5.  Longissimus  dorsi. 

d.  By  their  bodies,  to  the — 

1.  Psoas  magnus. 

2.  Psoas  parvus. 

3.  Crura  of  the  diaphragm. 


THE  MUSCLES. 

D.  Sacrum. 

The  sacrum  gives  insertion  to  the — 

1.  Longissimus  dorsi. 

2.  Semispinalis  of  the  back  and  loina- 

3.  Erector  coccygis. 

4.  Curvator  coccygis. 

5.  Depressor  coccygis. 

6.  Iscbio-coccygeal  muscles. 

7.  Biceps  femoris. 

8.  Semitendinosus. 

9.  Obturator  internus. 

E.  Coccyx. 

The  coccyx  gives  insertion  to  the 

1.  Erector  coccygis. 

2.  Depressor  coccygis. 

3.  Curvator  coccygis. 

4.  Ischio-coccygeal  muscles  (Ist  and  2nd  coccygeal  vertebm). 

II.  Head. 
A.  Bones  of  the  Cranium. 

1.  Occipital. 

The  occipital  gives  insertion  to  nine  pairs  of  muscles  : — 

1.  Complexus. 

2.  Obliquus  capitis  posticus. 

3.  Rectus  capitis  posticus  major. 

4.  Rectus  capitis  posticus  minor. 

5.  Rectus  capitis  aiiticus  major. 

6.  Rectus  capitis  anticus  minor. 

7.  Rectus  capitis  lateralis. 

8.  Digastricua 

9.  Occipito-styloid, 

2.  Paeietal. 
The  parietal  gives  attachment  to  one  muscle  : — 

Temporalis. 

3.  Frontal. 

The  frontal  gives  insertion  to  the — 
Levator  labii  superioris  proprius. 

4.  Sphenoid. 

The  sphenoid  gives  attachment  to  four  muscles  : — 

1.  Rectus  capitis  anticus  major. 

2.  Rectus  capitis  anticus  minor. 

3.  Pterygoideus  inteinus. 

4.  Pterygoideus  externua. 


GENERAL  TABLE  OF  TEE  ATTACHMENT  OF  MUSCLES  IN  S0LIFED8.    383 

5.  Temporal. 
The  temporal  gives  insertion  to  five  muscles  : — 

1.  Splenius. 

2.  Trachelo-mastoideus. 

3.  Obliquus  capitis  postioua. 

4.  Mastoido-humeralis. 

5.  Temporalis. 

B.  Bones  of  the  Face. 
1.  Superior  Maxilla. 
The  supermaxilla  gives  insertion  to  the  following  muscles  x— 

1.  PanniculuB. 

2.  Buccinator. 

3.  Levator  labii  superioris  propria. 

4.  Dilator  naris  lateralis. 

5.  Masseter. 

2.  Premaxilla, 

The  premaxilla  gives  insertion  to  the — 

1.  Dilator  naris  superior. 

2.  Levator  menti. 

3.  Palatine. 
The  palatine  gives  insertion  to  the — 

Pterygoideus  intemus. 

4.  Malar. 
The  malar  gives  insertion  to  one  muscle,  the^ 
Levator  labii  superioris  proprius. 

5.  Lachrymal. 
The  lachrymal  gives  insertion  to  one  muscle,  the— 
Lacbrymalis. 

6.  Nasal. 
The  nasal  gives  insertion  to  one  muscle,  the — 

Levator  labii  superioris  proprius. 

7.  Inferior  Maxilla. 
The  inferior  maxilla  gives  insertion  to  the  following  muscles  :-^ 

1.  Sterno-maxillaris. 

2.  Buccinator. 

3.  Depressor  labii  iiiferiore 

4.  Levator  menti. 

5.  Masseter. 

6.  Temporalis. 

7.  Pterygoideus  intemu8. 

8.  Pterygoideus  extemuB. 

9.  Digastricus. 

10.  Mylo-hyoideus. 

11.  Genio-hyoideus. 


t  THE  MUSCLES. 

C.  Hyoid. 

The  hyoid  gives  insertion  to  the  following  muscles  : — 

a.  By  its  body  and  its  thyroid  cornua — 

1.  Sterno-hyoideus. 

2.  Subscapulo-hyoideus. 

3.  Mylo-hyoideua. 

4.  Genio-hyoideus. 

5.  Stylo-hyoideus. 

6.  Hyoideus  magnus. 

7.  Hyoideus  transversus. 

6.  By  its  branches  (styloid  cornua  aad  styloid  bones) — 

1.  Stylo-hyoideus. 

2.  Hyoideus  magnus. 

3.  Ocoipito-styloideus. 

III.  Bones  of  the  Thorax. 
A.  The  Ribs  and  their  Cartilages. 

The  ribs  and  costal  cartilages  give  attachment  to  seventeen  muscles  :— 

1.  Scalenus  (Ist). 

2.  Serratus  anticus  (5th  to  9th). 

3.  Serratus  posticus  (9th  to  18th). 

4.  Longissimus  dorsi  (3rd  to  18th). 

5.  Transversalis  costarum. 

6.  Psoas  magnus  (17th  to  18th). 

7.  Quadratus  lumborum  (16th  to  18th). 

8.  Serratus  magnus  (1st  to  8th). 

9.  External  iutercostals. 

10.  Internal  intercostals. 

11.  Levatores  costarum. 

12.  Triangularis  stemi  (2nd  to  8th). 

13.  Obliquus  abdominis  extemus  (5th  to  18th). 

14.  Obliquus  abdominis  internus  (asternal  cartilages). 

15.  Eectus  abdominis  (asternal  cartilages). 

16.  Transversalis  abdominis. 

17.  Diaphragm  (7th  to  18th). 

B.  Sternum. 

The  sternum  gives  attachment  to  nine  muscles  :  — 

1.  Panniculus  cervicalis  of  the  neck. 

2.  Sterno-maxillaris. 

3.  Sterno-thyro-hyoideus. 

4.  Superficial  pectorals. 

5.  Deep  pectorals. 

6.  Triangularis  sterni. 

7.  Eectus  abdominis. 

8.  Transversalis  abdominis. 

9.  Diaphragm. 


GENEBAL  TABLE  OF  THE  ATTACHMENT  OF  MUSCLES  IN  SOLIPEDS.    885 

IV.  Thoracic  Limb. 
A.  Bones  of  the  Shoulder. 

Scapula. 
The  scapula  gives  attachment  to  seventeen  muscles  :— 

a.  By  its  external  face,  to  the — 

1.  Supra-spinatuB. 

2.  Infra-spinatus. 

3.  Teres  minor. 

4.  Teres  externus. 

5.  Trapezius. 

6.  Mastoido-humeralie. 

6.  By  its  internal  face,  to  the— 

1.  Rhomboideus. 

2.  Angularis  scapulae. 

3.  Serratus  magnus. 

4.  Subscapularis. 

5.  Scapulo-humeralis  gracilis. 

c.  By  its  anterior  border,  comprised  between  the  cervical  angle  and  the  coracoid  process, 

to  the — 

1.  Sterno-prescapularis. 

2.  Biceps. 

3.  Coraco-humeralis. 

4.  Supra-spinatus. 

d.  By  its  posterior  border,  comprised  between  the  dorsal  angle  and  the  corresponding 

portion  of  the  humeral  angle,  to  the — 

1.  Caput  magnum. 

2.  Scapulo-ulnaris. 

3.  Teres  major. 

4.  Deltoid. 

5.  Teres  minor. 

B.  Bones  of  the  Arm. 

Humerus. 
The  humerus  gives  attachment  to  twenty-four  muscles  :— 

a.  By  its  superior  extremity,  to  the — 

1.  Supra-spinatus. 

2.  Infra-spinatuB. 

3.  Subscapularis. 

4.  Scapulo-humeralis  gracilis. 

5.  Posterior  deep  pectoral. 

6.  Panniculus  camosus. 

b.  By  its  body,  to  the^ 

1.  Deltoid. 

2.  Teres  minor. 

3.  Coraco-humeralis  by  two  pointa 

4.  Teres  major. 

5.  Brachialis  anticus. 

6.  Caput  medium. 

7.  Caput  parvum. 

8.  Anconeus. 

9.  Extensor  metacarpi  magnus. 
10.  Extensor  pedis. 


386  THE  MUSCLES. 

11.  Latissimus  dorsi. 

12.  Mastoido-humeralis. 

13.  Anterior  superficial  pectoral. 

e.  By  its  inferior  extremity,  to  the — 

1.  Extensor  pedis. 

2.  Flexor  metacarpi  externus. 

3.  Flexor  metacarpi  obliquua. 

4.  Flexor  metacarpi  internua. 

5.  Flexor  pedis  perforatus. 

6.  Flexor  pedis  perforaus. 

C.  Bones  of  the  Forearm. 

1.  Radius. 
The  radius  gives  attachment : — 

a.  By  its  upper  extremity,  to  the — 

1.  Biceps. 

2.  Extensor  pedis. 

3.  Extensor  suflFraginia. 

6.  By  its  body,  to  the — 

1.  Brachialis  anticus.  « 

2.  Extensor  metacarpi  obliquas. 

3.  Extensor  pedis. 

4.  Extensor  suffraginis. 

5.  Flexor  pedis  perforans. 

2.  Ulna. 
The  ubia  gives  attachment  to  nine  muscles  : — 

a.  By  its  upper  extremity  {olecranon),  to  the— 

1.  Caput  niagnus. 

2.  Scapulo-ulnaris. 

3.  Caput  medium. 

4.  Caput  parvum. 

5.  Anconeus. 

6.  Flexor  metarcarpi  obliquufl. 

7.  Flexor  pedis  perforans. 

0.  By  its  body,  to  the — 

1.  Brachialis  anticus. 

2.  Extensor  sufifraginis. 

D.  Bones  of  the  Carpus. 

PisiFOEM  Bone. 

The  supercarpal  bone,  the  only  bone  of  the  carpus  which  has  muscular 
attachments,  gives  attachment  to  two  muscles  : — 

1 .  Flexor  metacarpi  externus. 

2.  Flexor  metacarpi  medius. 

E.  Bones  of  the  Metacarpus. 
1.  Principal  Metacarpal. 
The  principal  metacarpal  gives  attachment  to  a  single  muscle  ^— 

By  its  superior  extremity,  to  the — 
Extensor  metacarpi  magnus. 


GENERAL  TABLE  OF  THE  ATTACHMENT  OF  MUSCLES  IN  SOLIPEDS.    387 

2.  External  Rudimentary  Metacarpal. 
This  gives  attachment  to  a  single  muscle  : — 

Flexor  metacarpi  externizs. 

3.  Internal  Rudimentary  Metacarpal. 
This  gives  attachment  to  two  muscles  : — 

1.  Extensor  metacarpi  obliquus. 

2.  Flexor  metacarpi  intemua. 

F.  Bones  of  the  Digital  Region. 

1.  First  Phalanx. 
This  gives  attachment  to  two  muscles  : — 

1.  Extensor  pedis. 

2.  Extensor  suflfraginis. 

2.  Second  Phalanx. 
This  gives  attachment  to  two  muscles  : — 

1.  Extensor  pedis. 

2.  Flexor  pedis  perforatus. 

3.  Third  Phalanx. 

The  third  phalanx,  or  os  pedis,  gives  attachment  to  two  muscles : — 

1.  Extensor  pedis. 

2.  Flexor  pedis  perforans. 

V.  Abdominal  Limb. 
A.  Bones  of  the  Haunch. 

Coxa. 
The  coxa  gives  attachment  to  thirty-two  muscles  : — 

a.  By  the  ilium,  to  the — 

1.  Longissimus  dorsi. 

2.  Iliacus. 

3.  Psoas  parvus. 

4.  Quadratus  lumborum. 

5.  Compressor  coccygis. 

6.  Obliquus  abdominis  externus. 

7.  Obliquus  abdominis  internus. 

8.  Transversalis  abdominis  (through  the  medium  of  the  crural  arch). 

9.  Gluteals. 

10.  Tensor  vaginae  femoris. 

11.  Rectus  femoris. 

12.  Rectus  parvus. 

13.  Obturator  internus. 

b.  By  the  pubis,  to  the — 

1.  Obliquus  abdominis  externus. 

2.  Rectus  abdominis. 

3.  Transversalis  abdominis  (through  the  medium  of  the  crural  arch). 

4.  Gracilis. 
6.  Fectineus. 


TEE  MUSCLES. 


6.  Adductor  parvus. 

7.  Obturator  externus. 

8.  Obturator  internus. 

e.  By  the  ischium,  to  the — 

1.  Superficial  gluteus. 

2.  Biceps  femoris. 

3.  Semitendinosus. 

4.  Semimembranosus. 

5.  Gracilis. 

6.  Adductor  magnus. 

7.  Quadratus  femoris. 

8.  Obturator  extemus. 

9.  Obturator  internus. 
10.  Gemelli  of  the  pelvis. 


B.  Bones  of  the  Thigh. 

Femur. 
The  femur  gives  attachment  to  twenty-four  muscles ; 

a.  By  its  upper  extremity,  to  the — 

1.  Psoas  magnus. 

2.  Iliacus. 

3.  Superficial  gluteus. 

4.  Middle  gluteus. 

5.  Deep  gluteus. 

6.  Obturator  extemus. 

7.  Obturator  internus. 

8.  Gemelli  of  the  pelvis. 

b.  By  ite  body,  to  the — 

1.  Superficial  gluteus, 

2.  Fascia  lata. 

3.  Vastus  extemus. 

4.  Vastus  internus. 

5.  Rectus  parvus. 

6.  Pectineus. 

7.  Adductor  parvus. 

8.  Adductor  magnus. 

9.  Quadratus  femoris,  ^ 

10.  Gastrocnemius. 

11.  Flexor  pedis  perforatus. 
e.  By  its  inferior  extremity,  to  the — 

1.  Semimembranosus. 

2.  Adductor  magnus. 

3.  Extensor  pedis. 

4.  Flexor  metatarsi. 

5.  Popliteus. 

C.  Bones  of  the  Leg. 

1.  Tibia. 
The  tibia  gives  attachment  to  eleven  muscles  :— 

o.  By  its  upper  extremity,  to  the — 

1.  Flexor  metatarsi. 

2.  Soleus. 

3.  Flexor  pedis  perforans. 


QENEBAL  TABLE  OF  THE  ATTACHMENT  OF  MUSCLES  IN  SOLIPEDS.     38? 

4.  Flexor  accessorius. 

5.  Sartorius  (through  the  medium  of  the  internal  patellar  ligament). 

b.  By  its  body,  to  the — 

1.  Biceps  femoris. 

2.  Semitendinosus. 

3.  Gracilis  (in  common  with  the  long  adductor). 

4.  Flexor  metatarsi. 

5.  Popliteus. 

6.  Flexor  pedis  perforans., 

2.  Fibula. 
The  fibula  gives  insertion  to  two  muscles  : — 

1.  Extensor  suifraginis. 

2.  Flexor  pedis  perforans. 

3.  Patella. 
The  patella  gives  insertion  to  five  muscles  : — 

1.  Tensor  vaginae  femoris. 

2.  Rectus  femoris. 
3   Vastus  externus. 

4.  Vastus  internus. 

5.  Superficial  gluteus  (posterior  portion). 


D.  Bones  of  the  Tarsus. 

Calcis. 
The  calcis  gives  insertion  to  the— 

Gastrocnemius. 

Cuboid. 
The  cuboid  gives  insertion  to  the — 
Flexor  metatarsi. 

Second  Cuneiform. 
This  gives  attachment  to  one  muscle,  the — 
Flexor  metatarsi. 

E.  Bones  of  the  Metatarsus. 

The  principal  metatarsal  gives  insertion  to  one  muscle,  the 
Flexor  metatarsi. 

F.  Bones  of  the  Foot. 

1.  First  Phalanx. 
The  first  phalanx  gives  insertion  to  one  muscle,  the — 


Anterior  extensor  of  the  phalanges. 


390  THE  MUSCLES. 

2.  Second  Phalanx. 

The  second  phalanx  gives  insertion  to  two  muscles  t— 

1.  Extensor  pedis. 

2.  Flexor  pedis  perforatus. 

3.  Third  Phalanx. 
The  third  phalanx  gives  insertion  to  two  muscles  ?— 

Extensor  pedis. 
Flexor  pedis  perforans. 


BOOK   II. 
THE    DIGESTIVE    APPARATUS. 

CHAPTER  I. 

General  Considerations  on  the  Digestive  Apparatus. 

We  have  considered  the  animal  as  a  machine  composed  of  various  levers  and 
capable  of  various  movements ;  but  it  will  be  easily  understood  that  the  working 
of  this  machine  will  cause  the  wear  or  decomposition  of  the  molecules  which 
enter  into  the  construction  of  its  organs,  and  that  these  springs  or  animated 
wheels  demand  for  their  maintenance  an  incessant  supply  of  new  materials, 
in  order  to  repair  their  continual  losses.  Animals,  therefore,  are  under  the 
necessity  of  taking  aliment,  from  which  they  extract  those  reparative  principles 
that,  distributed  to  all  the  organs,  are  assimilated  to  their  proper  substance. 

The  organs  in  which  this  work  of  preparation  and  absorption  of  the  organiz- 
able  material  is  carried  on,  are  collectively  named  the  digestive  apparatus — one  of 
the  most  important  of  those  which,  as  we  shall  see,  successively  complicate  and 
perfect  the  animal  machine.  This  apparatus  does  not,  properly  speaking, 
constitute  an  essentially  distinctive  characteristic  of  animality,  as  there  are 
animals  without  a  digestive  cavity  ;  but  it  is  yet  one  of  the  most  salient 
attributes,  for  the  exceptions  just  mentioned  are  extremely  rare.  Considered  in 
the  Vertebrata,  this  apparatus  appears  as  a  long  tube,  most  frequently  doubled 
on  itself  many  times,  dilated  at  intervals,  and  provided  along  its  course  with 
several  supplementary  organs,  the  majority  of  which  are  of  a  glandular  nature. 
This  tube  extends  the  whole  length  of  the  animal's  body,  and  opens  externally 
by  two  orifices,  one  of  these  serving  for  the  introduction  of  aliment,  the  other 
for  the  expulsion  of  the  residue  of  digestion.  These  openings  are  at  the 
extremities  of  the  alimentary  canal. 

The  conformation  of  this  apparatus  is  not  incidentally  the  same  in  all  the 
individuals  composing  the  sub-kingdom  of  Vertebrata  ;  on  the  contrary,  it 
presents  very  numerous  varieties,  according  to  the  habits  and  modes  of  life  of 
these  individuals,  and  this  makes  its  study  interesting  from  two  points  of  view  : 
in  relation  to  the  science  of  zoology,  and  to  that  of  veterinary  hygiene,  which 
derives  from  this  study  valuable  indications  concerning  the  regime  of  the 
domesticated  animals. 

But  this  diversity  of  characters  does  not  suffice  to  establish  sharply  defined 
limits  between  the  conformations  that  are  distinguished  by  it.  There  is,  in 
reality,  but  one  typical  form  of  digestive  apparatus,  and  the  same  principle 
'prevails  in  its  construction  throughout  the  entire  series.  Thus,  whichever  of 
the  Vertebrata  we  may  be  studying,  its  alimentary  tube  will  be  found  composed 


392        GENERAL   CONSIDERATIONS  ON  THE  DIGESTIVE  APPARATUS. 

of  a  collection  of  dilatations  or  tubuliform  cavities,  which  succeed  each  other 
from  before  to  behind  in  the  following  order  :  the  mouth,  jihari/nx,  msophagm^ 
stomach,  and  intestine. 

This  system  of  cavities  is  divided,  physiologically,  into  two  principal  sections. 
The  first  comprises  the  mouth,  pharjux,  and  oesophagus— the  compartments 
in  which  are  carried  on  those  digestive  operations  termed  }yreparatory,  because 
they  prepare  the  aUment  for  the  subsequent  modifications  that  constitute  the 
essential  phenomena  of  digestion  ;  the  second  section  is  formed  by  the  stomach 
and  intestines,  where  these  phenomena  take  place. 

Each  of  these  two  sections  is  furnished  in  its  course  with  annexed  organs, 
which  are  present  in  the  majority  of  Vertebrata  ;  these  are  the  salivary  glands 
for  the  cavities  of  the  first  category,  and  the  liver,  immreas,  and  spleen  for  those 
of  the  second. 

In  considering  the  general  position  of  these  various  parts — principally  in 
Mammals  and  Birds— it  is  found  that  the  first  section  of  the  digestive  canal  and 
its  appended  organs  are  lodged  beneath  the  upper  jaw  and  the  base  of  the 
cranium,  and  under  the  cervico-thoracic  portion  of  the  vertebral  spine.  The 
second  section,  with  its  annexes,  occupies  the  great  abdominal  cavity. 

In  Man,  these  two  sections  are  divided  into  supra-diaphragmatic  and  infra- 
diaphragmatic  regions,  because  of  their  relations  to  the  diaphragm. 

The  constituent  parts  of  the  first  category  might  be  termed,  by  reason  of 
their  functions,  the  preparatory  organs  of  the  digestive  apparatus ;  and  those  of 
the  second,  or  abdominal  portion,  the  essential  organs  of  digestion. 

These  various  organs,  with  those  of  the  respiratory  and  genito-urinary 
apparatus,  have  received  the  name  of  viscera,  and  the  term  splanchnology  is  often 
given  to  that  branch  of  anatomy  devoted  to  their  study.^ 

These  new  organs  differ  so  notably  from  those  already  described,  that  it  is 
necessary  to  enter  into  some  generalities  as  to  their  nomenclature,  arrangement, 
form,  structure,  and  physical  or  chemical  characteristics. 

Nomenclature  in  splanchnology  does  not  rest  on  any  scientific  basis  ;  the 
name  of  organs  being  sometimes  derived  from  their  form — as  the  amygdalm  ; 
sometimes  from  their  direction — rectum-  sometimes  also  from  their  uses — the 
(esophagus,  salivary  glands ,-  their  length— duodenum ;  the  names  of  the  anatomists 
who  have  described  them — the  drnt  of  Stem,  Fallopian  tube ;  and  at  times  these 
names  are  purely  conventional,  as  the  spleen. 

They  are  distinguished  as  hollow  and  solid  organs. 

1.  The  HOLLOW  ORGANS  have  a  more  or  less  considerable  cavity,  capable 
of  being  increased  or  diminished,  but  they  are  not  of  a  definite  shape  or  size. 
Their  consistency  varies  with  their  state  of  plenitude  or  vacuity,  and  they  are 
single  or  double,  symmetrical  or  asymmetrical. 

In  all  cases,  the  walls  of  the  hollow  organs  are  composed  of  two  or  more 
membranes,  which  we  will  now  describe  in  a  general  manner. 

•  The  deaignation  viscera  (from  veseor,  "  I  nourish  ")  has  been  given  to  the  organs  which  aid 
in  nutrition,  and  the  term  Splanchnology  (from  ffn\a.yx>'ov,  a  "  viecus  "  or  "  intestine  ")  has  been 
bestowed  on  that  division  of  anatomy  which  treats  of  these  organs.  Splanchnology,  thus 
understood,  comprises  the  study  of  the  digestive,  respiratory,  urinary,  and  circulatory  apparatus. 
But  the  description  of  the  latter  forms  a  separate  category,  desiguated,  in  tlie  language  of  tlie 
schools,  Angiology.  On  the  other  hand,  however,  several  authorities  include  in  Splanchnology 
the  organs  of  generation,  and  others  even  add  the  organs  of  sense.  There  is,  therefore,  no, 
accord  in  the  limits  given  to  the  definition  of  Splanchnology ;  and  this  being  the  case,  we  have 
thought  it  best  to  omit  this  expression  and  the  distinction  sought  to  be  established  by  it. 


GENERAL   CONSIDERATIONS   ON  THE  DIGESTIVE  APPARATUS.        393 


a.  The  innermost  is  called  the  mucous  membrane,  because  of  the  mucus 
with  which  its  free  surface  is  always  covered.  It  is  continuous  with  the  skin  at 
the  natural  openings  ;  and  from  its  similarity  of  organization,  it  has  been  named 
the  internal  or  re-entering  skin,  or  internal  tegumentanj  membrane. 

It  should  be  remarked,  however,  that  the  comparison  of  the  mucous  membrane 
with  the  skin  only  holds  good  at  the  two  ends  of  the  apparatus — anteriorly,  from 
the  mouth  to  the  stomach  ;  posteriorly,  at  the  margin  of  the  anus. 

A  mucous  membrane  comprises  a  superficial  or  epithelial  layer  and  a  deep 
portion  which  constitutes  the  dermis,  or  chorion  {corium). 

The  epithelium^  is  a  very  thin,  inert  pellicle,  entirely  composed  of  epithelial 
cells  united  by  an  almost  insignificant  quantity  of  amorphous  matter  {Mastema). 
The  cells  are  flat  or  polygonal,  round  or  cylindrical,  polyhedral,  or  very  irregular 
in  shape.  In  consequence  of  these  diverse  forms,  there  is  pavement  (or  flat, 
simple,  tesselated,  or  squamous),  spherical  (or  spheroidal),  and  cylindrical  or  conical 
(or  columnar)  epithelium.  If  the  cells  are  furnished  with  small  filiform  appendages, 
named  vihratile  cilia,  the  epithelium  is  then  designated  ciliated.    When  the  cells 


Fig.  210. 


Fig.  211. 


Fig.  212. 


COLUMNAR  EPITHELIUM. 

1,  Nucleus  of  the  cell ; 
2,  membrane  of  the 
cell  raised  from  its 
contents  by  the  ab- 
sorption of  water. 


COLUMNAR   CILIATED   EPITHELIUM 
(magnified    310    DIAMETERS). 

a,    Nucleated    cells    resting    on    their 
smaller  extremities  ;  6,  cilia. 


SQUAMOUS  EPITHELIUM   FROM 
THE    MOUTH. 

The  large  scale  is  magnified 
310  diameters,  and  exhibits 
a  nucleus  with  nucleolus  in 
the  centre,  and  secondary 
nucleated  cells  forming  the 
body  of  the  scale. 

are  arranged  in  a  single  layer  on  the  surface  of  the  corium,  the  epithelium  is  said 
to  be  simple ;  it  is  stratified  (or  laminar)  when  the  cells  are  arranged  in  strata 
upon  each  other.  In  stratified  epithelium,  the  shape  of  the  cells  is  not  the  same 
on  the  surface  and  beneath  it,  and  it  is  named  after  the  form  of  the  superficial 
layer  :  examples — stratified  tesselated  epithelium.,  stratified  cylindrical  epithelium. 

The  mucous  dermis,  or  corium,  is  composed  of  connective  tissue,  the  thickness, 
elasticity,  vascularity,  and  sensibility  of  which  varies  with  the  situation  and  the 
function  of  organs.  The  corium  is  thin  and  almost  destitute  of  elastic  fibres 
when  applied  to  the  bony  walls  of  a  cavity ;  on  the  contrary,  it  is  thick,  elastic, 
and  slightly  adherent  when  it  lines  organs  which — like  the  stomach,  oesophagus, 
and  intestines — are  capable  of  increasing  or  diminishing  in  capacity.  The  fasciculi 
of  the  connective  tissue  in  the  deeper  layers  of  the  corium  are  loosely  united,  but 
nearer  the  surface  they  lie  closer  ;  sometimes  they  form,  under  the  epithelium, 
an  amorphous  surface-layer,  the  basement  (or  limitary)  membrane.  In  certain 
places  (intestine),  the  dermis  has  a  layer  of  smooth  muscular  fibres  which  can  be 
resolved  into  two  planes  (the  muscularis  mucosce). 

The  sub-epithelial  face  of  the  corium  is  scarcely  ever  smooth,  but  offers 
minute  prolongations  named  villosities,  or  papillm,  which  are  very  varied  in  their 
form  and  size  ;  it  is  more  or  less  marked  by  depressions,  named  follicles.  The 
villi  are  observed  on  the  deep-seated  mucous  membranes  (intestine)  ;  they  are 


394        GENERAL   CONSIDERATIONS   ON  THE  DIGESTIVE  APPARATUS. 


Fig.  213. 


CONICAL  VILLI  ON  MUCOUS  MEM- 
BRANE OF  SMALL  INTESTINE 
(MAGNIFIED    19    DIAMETERS). 

a,  Zone  of  follicles  surrounding  b. 
solitary  gland ;  6,  apertures  of 
simple  follicles. 

Fig.  214. 


more  particularly  the  vascular  and  absorbent  organs.  The  ^M_/?^7/fl?  are  found  in 
the  vicinity  of  the  natural  apertures,  and  are  rich  in  nerves  ;  they  are  more 
especially  the  organs  of  sensibility.  The  follicles, 
lined  by  one  or  other  form  of  cell,  are  exclusively 
organs  of  secretion. 

b.  The  second  membrane  met  with  in  the  walls 
of  the  hollow  organs  is  of  a  muscular  nature. 

The  mvsndar  membrane  is  formed  of  unstriped 
fibres,  the  slow  contraction  of  which  is  involun- 
tary. In  certain  organs — those  adjoining  the 
natural  apertures — the  unstriped  fibres  are  re- 
placed by  striped,  which  are  under  the  influence 
of  the  will,  or  have  the  same  physiological  and 
reflex  properties  as  the  smooth  fibres — as  in  the 
oesophagus. 

{Unstrijied  or  smooth  bands  of  muscles  are 
composed  of  long  fusiform  cells  with  staff -shaped, 
elongated  nuclei,  the  cells  varying  from  ttVs"  ^^ 
-^  of  an  inch  in  length,  and  from  s^^s  ^^  ttW 
of  an  inch  in  breadth.) 

c.  When  the  organs  are  lodged  in  one  of  the 
great  splanchnic  cavities,  such  as  the  chest  or 
abdomen,  they  have  a  third  membrane — a  serous 
layer,  which  lines  the  cavity,  and  is  reflected 
around  the  viscera  contained  in  it,  so  as  to 
envelop  them  more  or  less  completely.  This 
layer  has,  therefore,  an  adherent  face,  applied 
either  against  the  walls  of  the  cavity  or  the 
external  surface  of  the  splanchnic  organs ;  and 
a  free  face,  always  in  contact  with  itself. 

A  sei-ous  membrane  is  composed  of  two  layers  : 
a  deep,  connective  portion,  analogous  to  the 
mucous  corium ;  and  a  superficial,  which  is  only 
tesselated  epithelium.  The  free  surface  of  this 
epithelium  is  perfectly  smooth,  and  lubricated  by 
a  limpid  serosity  to  facilitate  the  gliding  of  the 
parts  the  membrane  covers.  (The  epithelium  is 
a  simple  tesselated  layer  of  flattened  and  poly- 
gonal nucleated  cells,  about  y^Vo-  of  an  inch  in 
diameter.) 

2.  The  SOLID  ORGANS  are  either  contained 
in  the  splanchnic  cavities  or  situated  outside 
them,  in  the  midst  of  connective  tissue,  which, 
in  becoming  more  dense  around  them,  often 
forms  a  fibrous  covering. 

Like  the  hollow  organs,  they  are  single — 
spleen,  liver ;  or  in  pairs — kidneys ;  and  sym- 
metrical or  asymmetrical  in  shape.  They  are 
retained  in  their  situation  by  their  vessels  and 
nerves,  by  adherence  to  the  neighbouring  organs,  or  by  particular  serous  bands. 


FUSIFORM  CELLS  OF  SMOOTH 
MUSCULAR   FIBRE. 

Two  cells  in  their  natural  state, 
one  showing  the  staff-shaped  nu- 
cleus ;  6,  a  cell  with  its  nucleus, 
c,  brought  distinctly  into  view  by 
acetic  acid. 


GENERAL   CONSIDERATIONS  ON  THE  DIGESTIVE  APPARATUS.        395 

With  the  exception  of  the  lungs  of  animals  that  have  respii;^d,  all  the  solid 
organs  have  a  density  greater  than  water.  Their  iveight  and  volume  offer 
numerous  differences,  which  are  individual,  or  peculiar  to  the  species  to  which 
they  belong.  Nevertheless,  each  organ  possesses  a  certain  volume  and  weight 
which  might  be  termed  physiologic  ;  when  the  organ  is  above  or  below  this 
average,  we  are  warranted  in  saying  that  it  is  in  a  pathological  condition. 

Solid  organs  are  more  or  less  round  in  form,  and  their  surface  is  traversed 
by  a  variable  number  of  furrows,  which  indicate  their  division  into  lobes  or 
lobules. 

Their  colour  is  diverse  ;  they  may  be  very  pale — parotid  gland ;  or  very  dark 
— liver,  spleen ;  or  uniform,  or  of  different  shades — varieties  which  are  most 
frequently  due  to  the  mode  of  distribution  of  the  vessels,  or  to  the  presence  of 
certain  anatomical  elements.  The  colour  of  organs  is  not  always  the  same  in 
the  deeper  parts  and  at  the  surface,  especially  when  they  are  enveloped  by  a 
thick,  opaque  membrane — for  instance,  the  testicle.  Lastly,  the  coloration  is  less 
intense  after  death  than  during  life,  and  particularly  if  the  animal  to  which  the 
organs  belonged  has  been  killed  by  effusion  of  blood. 

The  consistence  of  organs  depends  on  their  internal  formation,  and  the  nature 
of  their  constituent  elements  ;  there  are  soft  organs — such  as  the  lungs,  and 
resisting  organs— as  the  testicles.  As  a  general  rule,  the  consistency  of  organs 
diminishes  after  putrefaction  has  set  in. 

Cohesion  is  the  resistance  that  organs  offer  to  the  forces  which  tend  to  tear 
them  ;  it  depends  upon  the  texture  of  the  organs,  and  the  more  or  less  abundance 
of  fibrous  and  elastic  tissue  in  their  structure.  Cohesion  is  very  different  from 
consistency  ;  thus,  such  an  organ  as  the  lung  may  be  easily  compressed,  but  may 
be  very  difficult  to  tear. 

If  organs  are  examined  with  regard  to  their  structure,  it  will  be  observed  that 
all  have  a  thin  or  thick  fibrous  covering,  which  throws  septa  into  their  interior, 
and  which  support  their  proper  tissue  ;  this  tissue  varies  with  the  nature  of  the 
organs.  It  will  also  be  found  that  they  are  traversed  by  a  more  or  less  considerable 
number  of  blood-vessels — arteries  and  veins.  These  vessels  expand  into  a  capillary 
network,  the  meshes  of  which  have  a  shape  closely  allied  to  that  of  the  elements 
of  the  proper  tissue.  The  number  and  volume  of  the  vessels  of  an  organ  give 
an  exact  idea  of  its  importance,  and  of  the  activity  of  the  physiological  phenomena 
taking  place  in  it.  Finally,  into  the  composition  of  organs  enter  superficial  and 
deep  lymphatic  vessels  and  nerves,  which  generally  follow  the  arteries.  The 
nerves  show  in  their  course  small  ganglionic  enlargements. 

All  the  solid  organs  are  either  glands,  or  are  apparently  glandular.  The 
function  of  glands  is  to  elaborate  or  eliminate  certain  fluid  or  semifluid  products, 
which,  thrown  out  in  hollow  organs,  are  absorbed  by  their  internal  surface,  or 
excreted. 

The  very  simple  (or  tubular)  glands  consist  of  a  straight  or  convoluted  tube, 
or  of  a  small  vesicular  cavity  opening  on  a  tegumentary  membrane  ;  they  are 
lined  on  their  inner  face  by  one  or  more  layers  of  cells.  As  an  example,  there 
may  be  cited  the  tubular  glands  of  the  stomach  and  intestines. 

But  there  are  also  conglomerate  glands — organs  more  complex,  but  which  are 
merely  masses  of  simple  glands.  There  are  tubular  glands,  like  the  kidneys  and 
testicles ;  racemose  glands,  such  as  the  salivary  gla7ids  and  pancreas ;  or  a 
network  of  glands,  like  the  liver.  In  these  the  essential  anatomical  element — 
the  polygonal,  cylindrical,  or  spherical  gland-cell — is  situated  on  the  inner  face 


396  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

of  a  tube — as  in. the  kidney ;  or  a  vesicle,  as  is  seen  in  i\ie  pancreas ;  or  deposited 
without  any  order  in  the  meshes  of  a  plexus  of  canaliculi,  as  occurs  in  the  liver. 

The  conglomerate  glands  are  provided  with  a  common  excretory  duct,  that 
commences  in  their  mass  by  a  great  number  of  arborescent  ramifications.  The 
walls  of  this  duct  are  composed  of  an  elastic,  and  sometimes  contractile,  connective 
tissue  membrane,  covered  on  its  inner  face  by  an  epithehum,  which  may  or  may 
not  be  of  the  same  character  as  that  of  the  gland. 

For  a  long  time  there  have  been  classed  as  glands  certain  organs  without 
excretory  ducts,  and  having  only  analogies  to  glands.  The  majority  of  these 
belong  to  the  lymphatic  apparatus,  and  will  be  considered  hereafter ;  but  it 
may  be  mentioned  here  that  they  are  all  composed  of  masses  of  cells  ;  some  are 
small  and  simple — these  are  the  closed  follicles,  solitary  or  agminated,  and  dis- 
persed beneath  the  intestinal  mucous  membrane ;  the  others  are  more  complex 
and  voluminous,  and  form  lymphatic  glands. 

To  the  vascular  system,  but  more  particularly  to  the  lymphatic  apparatus, 
are  annexed  other  glandiform  organs,  the  fundamental  structure  of  which, 
analogous  in  principle  to  that  of  the  lymphatic  glands,  is,  nevertheless,  dis- 
tinguished from  them  by  certain  peculiarities — such  are  the  spleen,  thymus 
gland,  and  thyroid  body. 

This  is  the  limit  to  which  the  generalities  relating  to  the  viscera  that  form 
the  object  of  splanchnology,  must  be  confined.  We  will  now  pass  to  a  descrip- 
tion of  the  digestive  apparatus  in  Mammals. 


CHAPTER   II. 

THE   DIGESTIVE   APPARATUS   IN   MAMMALIA. 

We  will  study,  successively  :  1.  The  preparatory  organs,  which  include  the 
mouth,  the  salivary  glands  annexed  to  that  cavity,  the  pharynx,  and  the  otso- 
phagus.  2.  The  essential  organs,  comprising  the  stomach  and  intestine,  and  their 
annexes — the  liver,  pancreas,  and  spleen ;  with  the  abdominal  cavity,  which 
contains  and  protects  these  organs. 

Article  I. — Preparatory  Organs  of  the  Digestive  Apparatus. 
The  Mouth. 

The  mouth — the  first  vestibule  of  the  alimentary  canal — is  a  cavity  situated 
between  the  two  jaws,  elongated  in  the  direction  of  the  larger  axis  of  the  head, 
and  having  two  openings  :  an  anterior,  for  the  introduction  of  food,  and  a 
posterior,  by  which  the  aliment  passes  into  the  pharynx. 

The  mouth  should  be  studied  in  six  principal  regions  :  1.  The  lips,  which 
circumscribe  its  anterior  opening.  2.  The  cheeks,  forming  its  lateral  walls.  3. 
The  palate,  which  constitutes  its  roof  or  superior  wall.  4.  The  tongue,  a  muscular 
appendage,  occupying  its  inferior  wall.  5.  The  soft  palate  {velum  pendulum 
palati),  a  membranous  partition  situated  at  the  posterior  extremity  of  the  buccal 
cavity,  which  it  separates  from  the  pharynx,  and  concurs  in  the  formation — by  a 
portion  of  its  inferior  face  and  border — of  the  isthmus  of  the  fauces,  or  posterior 
opening  of  the  mouth.     G.  The  dental  arches  fixed  on  each  jaw. 


THE  MOUTH.  3!9fJ 

We  will  study  each  of  these  regions  in  particular,  before  passing  to  the 
examination  of  the  mouth  in  general. 

Preparation. — The  whole  of  the  mouth  ought  to  be  examined  in  an  antero-posterior  and 
vertical  section  of  the  head  (see  description  of  the  soft  palate). 

1.  The  Lips  (Fig.  168). 

These  are  two  membranous  movable  folds,  placed  one  above  the  other  belo-gf 
the  anterior  opening  of  the  mouth,  which  they  circumscribe.  There  is,  con- 
sequently, a  superior  and  an  inferior  lip,  united  at  each  side  by  a  commissure. 

Each  lip  offers  for  study  an  external  and  internal  face,  and  a  free  and  an 
adherent  border. 

The  external  surface  is  convex,  and  presents,  on  the  median  line  :  in  the  upper 
lip,  a  slight  projection  which  divides  it  into  two  lateral  lobes  ;  in  the  inferior  hp, 
and  altogether  posteriorly,  the  single  prominence  named  the  tuft  of  the  chin. 
This  face,  formed  by  the  skin,  is  garnished  with  line,  short  hairs,  amongst  which 
may  be  remarked  long,  coarse  bristles,  the  roots  of  which  are  implanted  per- 
pendicularly in  the  integument,  and  pass  beyond  its  deep  surface,  to  be  lodged 
in  the  subjacent  muscular  tissue.  These  pilous  tentacles  ought  to  be  considered 
as  real  tactile  organs,  because  several  sensitive  nerve-filaments  penetrate  to  the 
bottom  of  their  follicles,  and  they  have  a  very  remarkable  vascularization. 

The  internal  surface,  constituted  by  the  buccal  mucous  membrane,  and 
moulded  on  the  incisor  teeth,  is  concave,  smooth,  rose-coloured,  and  often 
stained  with  black  spots.  In  the  superior  lip,  particularly,  may  be  remarked 
numerous  orifices  opening  on  the  summits  of  three  small  papillae  ;  these  are  the 
openings  of  the  excretory  canals,  by  which  the  labial  glands  discharge  their  fluid 
into  the  interior  of  the  mouth. 

The  free  border,  thin  and  sharp,  shows  the  line  of  demarcation  that  separates 
the  two  teguments. 

The  adherent  border  is  limited,  in  the  buccal  cavity,  by  a  groove  formed  by 
the  mucous  membrane  in  passing  from  the  incisor  arches  to  the  inner  side  of  the 
lips.  Beyond  the  mouth  it  is  not  indicated  by  any  peculiarity  of  structure  or 
arrangement,  the  skin  being  continued  directly  from  the  neighbouring  parts  on 
the  lips. 

The  commissures  mark,  on  each  side,  the  point  of  union  between  the  free 
borders  of  the  two  lips.  They  are  rounded  in  Solipeds,  and  offer  nothing 
remarkable  otherwise. 

Steuctuke.— Each  lip  is  composed  of  two  tegumentary  layers  :  one  cutaneous, 
the  other  mucous,  between  which  is  found  muscular  tissue  and  glands,  and  the 
general  elements  of  every  organization — vessels  and  nerves. 

1.  Tegumentary  layers. — The  skin  adheres  closely  to  the  subjacent  tissues, 
and  apart  from  the  characters  already  indicated,  there  is  nothing  more  to  be  sayi 
at  present  with  regard  to  its  disposition,  as  it  will  be  studied  more  completely 
with  the  organs  of  sense.  With  regard  to  the  mucous  membrane,  it  may  be 
remarked  that  its  dermis  is  thick  and  dense,  and  lies  on  a  layer  of  salivary 
glands  ;  it  is  provided  with  simple  conical  papillae,  and  is  covered  by  stratified 
tesselated  epithelium.     (It  is  sometimes  streaked  with  pigment.) 

2.  Muscles. — These  are  :  the  labialis  or  orbicularis  oris — the  sphincter  of  the 
buccal  apertm-e,  and  common  to  the  two  lips  ;  in  the  upper  lip,  the  aponeurotic 
expansion  of  the  levator  labii  swperioris  propriu^,  the  musculo-fibrous  tissue  which 

28 


398  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

separates  this  expansion  from  the  cutaneous  integument,  and  the  terminal  inser- 
tion of  the  levator  labii  superioris  alcBqui  nasi  and  the  dilator  naris  lateralis  ;  in 
the  inferior  lip,  the  tuft  of  the  chin  and  its  suspensory  muscles — the  levatores  menti. 
All  these  muscles  having  been  studied  in  detail  in  the  Myology  (p.  274),  there  is 
no  necessity  for  their  being  again  described. 

3.  Labial  glandules. — These  form  an  almost  continuous  layer  between  the 
mucous  membrane  and  the  orbicularis  muscle.  They  are  small  secretory  organs, 
similar  in  their  structure  and  uses  to  the  salivary  glands,  and  will  be  described 
when  these  come  under  notice. 

4.  Vessels  and  nerves. — The  blood  is  carried  to  the  lips  by  the  palato-labial, 
and  the  superior  and  inferior  coronary  arteries.  It  is  returned  to  the  heart  by  the 
satellite  veins  of  the  two  last  vessels.  The  lymphatics  are  very  numerous,  and 
pass  to  the  glands  between  the  branches  of  the  lower  jaw.  The  nerves  are  of  two 
kinds  :  the  motor,  which  are  given  off  from  the  facial  nerve,  and  are  distributed 
in  the  muscular  tissue  of  the  lips  to  cause  its  contraction  ;  the  sensitive 
nerves — from  the  maxillary  branches  of  the  fifth  cranial  pair — are  distinguished 
by  their  number  and  considerable  volume,  and  are  nearly  all  distributed  to  the 
cutaneous  integument,  which  they  endow  with  an  exquisite  sensibility. 

Functions. — The  lips  serve  for  the  prehension  of  solid  and  liquid  food  ;  they 
retain  it  in  the  mouth  after  its  introduction  thereto,  and  they  prevent  the  escape 
of  the  saliva.  They  ought  also  to  be  regarded — especially  the  upper  lip — as  veiy 
delicate  tactile  organs. 

2.  The  Cheeks  (Fig.  168). 

These  are  two  membranous  walls,  which  enclose  the  molith  laterally.  In  the 
interior  of  the  buccal  cavity  they  are  limited  :  behind,  by  the  posterior  pillars  of 
the  tongue  ;  in  front,  by  the  lips,  with  which  they  are  confounded  around  the 
commissures  ;  above  and  below,  by  the  furrow  formed  by  the  gingival  mucous 
membrane,  where  it  is  reflected  from  the  molar  arches  on  to  the  cheeks. 

The  greatest  diameter  of  the  cheeks  is  antero-posterior,  like  that  of  the  cavity 
it  encloses.  The  vertical  diameter  is  very  small,  especially  behind  ;  anteriorly, 
however,  the  cheeks  assume  a  certain  amplitude  by  the  separation  of  the  jaws. 

Structure. — The  cheeks  are  formed  by  the  buccal  mucous  membrane,  external 
to  which  we  find  muscular  tissue  and  glands.  Vessels  and  nerves  are  supplied  for 
the  conveyance  of  nutritive  fluids,  sensibility,  or  the  stimulus  to  contractility. 

1.  Mucous  membrane. — The  external  face  of  this  membrane  is  closely  attached 
to  the  buccinator  muscle,  and  to  the  inferior  molar  glands.  Its  free  face  presents, 
at  the  level  of  the  third  upper  molar  tooth,  the  buccal  opening  of  the  parotid 
duct,  at  the  summit  of  a  variably-sized  tubercle.  On  the  face  of  each  dental 
arch  there  is  also  remarked  a  linear  series  of  little  salient  points,  analogous  to 
the  large  parotideal  tubercle  ;  these  are  the  excretory  orifices  of  the  molar  glands. 
Its  structure  is  the  same  as  the  mucous  membrane  of  the  lips.  (It  is  of  a  pale 
colour,  and  sometimes  stained  in  patches  with  pigment.) 

2.  Muscular  tissue. — This  is  the  buccinator  or  alveolo-labialis  muscle  already 
described.  It  may  be  remembered  that  the  external  face  of  this  muscle  is  covered 
by  the  masseter,  the  superior  molar  glands,  and  the  skin  ;  while  the  internal 
responds  to  the  mucous  membrane  and  the  inferior  molar  glands. 

3.  Glands. — These  are  two  masses  of  glandular  lobules,  known  as  the  molar 
glands.     They  will  be  described  with  the  salivary  glands. 


THE  MOUTH. 


Is  and  nerves. — The  external  maxillary,  coronary,  and  buccal  arteries  carry 
blood  to  the  cheeks.     The  veins  empty  them- 
selves  into  the  sateUite    branches    of    these  Fig.  21  o    . 
arteries. 

The  lymphatics  proceed  to  the  submaxillary 
glands.  The  nerves  are  of  the  same  kind,  and 
proceed  from  the  same  source,  as  those  sup- 
plying the  lips  :  being  the  seventh  pair  of 
cranial  nerves  for  the  muscular  layer,  and  the 
fifth  pair  for  the  integuments  (with  filaments 
of  the  sympathetic  for  the  blood-vessels  and 
labial  glands.) 

Functions. — The  cheeks  are  very  active 
agents  in  mastication,  by  constantly  pushing 
the  aliment,  through  the  action  of  the  bucci- 
nator, between  the  dental  grinding  surfaces. 

3.  The  Palate  (Fig.  215). 

Preparation. — Separate  the  head  from  the  trunk ; 
saw  through  the  branches  of  tlie  inferior  maxilla  above 
the  angle  of  the  jaw,  and  from  the  crown  of  the  last 
molar  tooth,  so  as  to  pass  between  the  curtain  of  the 
soft  palate  on  the  one  part,  and  the  base  of  the  tongue 
on  the  other,  leaving  the  latter  organ  adherent  to  the 
lower  jaw.  This  last  should  be  removed  from  the 
upper  jaw  by  cutting  through  the  masseter  and  bucci- 
nator muscles,  and  so,  exposing  the  hard  and  soft 
palates  in  such  a  manner  as  to  render  easy  the  special 
dissections  necessary  for  their  study.  For  the  palate, 
these  dissections  are  limited  to  the  removal  of  the 
mucous  layer  covering  the  deep  venous  network,  and 
to  the  partial  excision  of  this,  which  allows  the  artery 
and  palatine  nerves  to  be  seen  (see  Fig.  215). 

The  palate  (hard  palate),  palatine  arch,  or 
upper  luall  of  the  mouth,  is  circumscribed,  in 
front  and  on  the  sides,  by  the  superior  dental 
arch,  and  limited,  behind,  by  the  anterior 
border  of  the  soft  palate.  It  is  a  parabolic 
surface,  exactly  representing,  in  its  configura- 
tion, the  bony  palate  (Fig.  50). 

On  its  surface  is  remarked  a  median  groove, 
which  partitions  it  into  two  equal  divisions, 
and  which  commences  quite  in  front,  at  the 
base  of  a  small  tubercle.  Curved  transverse 
furrows,  twenty  in  number  (Leyh  gives  from 
sixteen  to  eighteen),  divide  each  of  these 
halves  into  an  equal  number  of  salient  arches, 
the  concavities  of  which  are  turned  backwards, 
and  which  become  narrower  and  less  marked 
as  they  are  more  posterior.  (These  arches  and 
furrows  aid  in  retaining  the  aliment  which  the 
tongue  carries  towards  the  palate  during 
deglutition.) 


THE   HARD  AND  SOFT  PALATE   OF  THE 
HOESE. 

The  mucous  membrane  has  been  removed 
from  the  right  side,  and,  with  the 
glandular  layer,  from  the  soft  palate. 
1,  The  ridges  of  the  palatine  mucous 
membrane  ;  2,  venous  network  of  the 
deep  layer,  which  is  incised  at  the 
external  side  to  show  the  palatine 
artery,  3,  accompanied  by  the  fila- 
ments of  the  palatine  nerve  ;  4,  car- 
tilaginous digitation,  over  which  passes 
and  is  inflected  the  palatine  artery ; 
5,  aponeurosis  of  the  soft  palate;  5', 
terminal  extremity  of  the  tendon  of 
the  tensor  palati,  forming  by  its  ex- 
pansion the  staphyline  aponeurosis ;  6, 
the  pharyngo-staphyhnus ;  7,  the  pa- 
lato-staphylinus;  8,  staphyline  nerves. 


400  THE  DIGESTIVE  APPABATUS  IN  MAMMALIA. 

Structure. — The  palate  lies  on  the  bony  vault  formed  by  the  palatine  and 
supermaxillary  bones.     It  includes  in  its  structure  : 

1.  A  fibrous  membrane,  applied  to  the  bone  just  mentioned,  which  sustains 
a  remarkably  developed  venous  network,  constituting  a  veritable  erectile  tissue, 
and  gives  to  the  palate  a  greater  or  less  degree  of  thickness,  according  to  its  state 
of  turgescence  (Fig,  215,  2). 

2.  A  mucous  layer,  extremely  adherent,  by  its  deep  face,  to  the  preceding 
tissue,  and  of  a  whitish  aspect  in  the  horse.  The  corium,  formed  entirely  of 
connective  tissue,  shows  numerous  conical  papillas,  especially  at  the  posterior 
part  of  the  palate.  The  epithelium  fills  up  the  depressions  between  the  papillse  ; 
it  is  stratified,  squamous,  and  remarkable  for  the  great  thickness  of  its  horny 
layer. 

3.  Two  voluminous  artmes — the  palatine — are  lodged  in  the  bony  fissures  of 
the  palatine  roof.  These  arteries  proceed  parallel  to  each  other,  and  unite  in 
front  by  anastomosing  to  form  a  single  trunk,  which  enters  the  incisive  foramen. 
It  is  of  importance  to  know  their  disposition,  from  a  surgical  point  of  view,  as  care 
ought  to  be  taken  not  to  wound  them  when  abstracting  blood  from  the  palate. 
The  blood  carried  by  these  arteries  arrives  in  the  deep-seated  erectile  membrane, 
and  is  finally  removed  by  two  very  short  venous  trunks,  which  do  not  pass  with 
the  palatine  arteries  into  the  palatine  canal,  but  only  into  the  palatine  fissure. 

4.  Sensory  nerves,  which  accompany  the  arteries,  and  are  derived  from  the 
superior  maxillary  branch  of  the  fifth  pair  of  cranial  nerves. 

Functions. — The  palate  has  a  passive,  but  important,  share  in  mastication 
and  deglutition  ;  furnishing  the  tongue,  as  it  does,  with  a  firm  basis  in  the 
movements  it  executes  when  passing  the  food  between  the  molar  teeth,  and  in 
carrying  the  ahmentary  mass  backwards  to  the  pharynx. 

4.  The  Tongue  (Figs.  221,  223,  251,  306). 

Preparation. — 1.  By  means  of  a  strong  saw  without  a  back,  make  an  antero-posterior  and 
vertical  section  of  the  head,  in  order  to  study  the  general  disposition  of  the  tongue.  2.  From 
another  head  remove  the  lower  jaw,  leaving  the  tongue  in  the  intermaxillary  space,  to  examine 
the  external  conformation  of  the  organ  (see  the  dissection  of  the  palate).  On  a  third  head, 
kept  for  the  study  of  the  muscles,  these  parts  are  exposed  in  the  following  manner :  The 
masseter  is  entirely  removed,  and  the  cheek  is  detached  from  the  lower  jaw  and  turned  over 
on  the  upper  jaw ;  then  the  branch  of  the  inferior  maxilla  is  sawn  through  transversely,  at 
first  behind,  next  in  front  of  the  molar  teeth  :  the  upper  piece  of  bone  should  be  detached  by 
disjointing  it  behind  the  temporo-maxillary  articulation,  after  destroying  the  capsular  liga- 
ment and  dividing  the  insertions  of  the  pterygoid  muscles.  With  resrard  to  the  inferior  piece, 
it  is  reversed  in  such  a  way  as  to  put  the  line  of  the  molars  downwards,  and  the  inferior  border 
of  the  bone  upwards  in  the  bottom  of  the  intermaxillary  space.  To  do  this,  it  is  sufficient  to 
separate  the  buccal  mucous  membrane  from  the  mylo-hyoideus  muscle,  proceeding  from  above 
to  below.  Tiie  dissection  thus  prepared,  serves  not  only  for  the  study  of  the  muscles  of  the 
tongue,  but  also  for  those  of  the  deep  salivary  glands,  the  pharynx,  larynx,  guttural  pouches, 
the  nerves  and  arteries  of  the  head,  etc.  It  is  always  better,  in  order  to  facilitate  this  dissec- 
tion, to  keep  the  jaws  apart  by  fixing  a  piece  of  wood  or  bone  between  the  incisor  teeth 
immediately  after  the  death  of  the  animal. 

llie  lingual  canal. — The  inferior  wall  (or  floor)  of  the  mouth,  circumscribed 
by  the  lower  alveolar  arches,  forms  an  elongated  cavity  named  the  lingual  canal 
(or  space),  which  lodges  the  organ  designated  the  tongue.  This  canal  occupies, 
in  its  anterior  third,  the  superior  surface  of  the  body  of  the  inferior  maxilla.  For 
the  remainder  of  its  extent,  it  is  formed  by  a  double  groove  in  the  floor  of  the 
mouth,  at  the  sides  of  the  tongue.  It  exhibits  the  suhlimiiutl  crest  oxi^  the  barhs^ 
of  which  we  will  speak  when  describing  the  sublingual  and  maxillary  glands. 


THE  MOUTH.  401 

Situation  of  the  tongue. — The  tongue  occupies  the  whole  length  of  this 
elongated  cavity,  and  thus  extends  from  the  back  part  of  the  mouth  to  the 
incisor  teeth,  lying  in  the  intermaxillary  space,  where  it  rests  on  a  kind  of 
wide  sling  formed  by  the  union  of  the  two  mylo-hyoidean  muscles  (see  Fig. 
307,  7). 

External  conformation. — It  is  a  fleshy  organ,  movable  in  the  interior  of  the 
buccal  cavity,  and  almost  entirely  enveloped  by  the  mucous  membrane  which 
lines  that  cavity.  In  Solipeds,  it  forms  a  kind  of  triangular  pyramid,  flattened 
on  each  side,  fixed  to  the  os  hyoides  and  the  inferior  maxilla  by  the  muscles 
which  form  the  basis  of  its  structure,  or  by  the  membrane  that  covers  the 
organ. 

Its  form  permits  it  to  be  divided,  for  the  study  of  its  exterior,  into  three  faces, 
three  borders,  and  two  extremities. 

The  superior  face,  or  dorsum  of  the  tongue,  narrower  in  front  than  behind, 
is  roughened  by  numerous  papilla  which  give  it  a  downy  aspect.  Two  of  these 
papillae  are  remarkable  for  their  enormous  volume,  their  lobulated  appearance, 
and  the  situation  they  occupy  at  the  bottom  of  two  excavations  placed  side  by 
side,  near  the  base  of  the  organ — the  lingual  lacunce,  or  foramen  ccecum  of  Mor- 
gagni.  This  face  corresponds  to  the  palatine  arch  or  roof,  when  the  jaws  are 
together.  The  lateral  faces,  wider  in  the  middle  of  the  tongue  than  at  its 
extremities,  are  limited  by  the  internal  surfaces  of  the  inferior  maxillary  branches. 
On  them  are  seen  several  large  papillse,  and  the  orifices  of  the  lingual  glandulce. 

These  two  faces  are  separated  from  the  former  by  two  lateral  borders,  which 
correspond  to  the  superior  alveolar  arches  when  the  mouth  is  exactly  closed. 
"With  regard  to  the  third  or  infeiior  border,  its  existence  may  be  said  to  be 
fictitious  ;  by  it  enter  the  muscles  which  constitute  the  substance  of  the  tongue, 
and  it  is  by  it,  also,  that  the  organ  is  fixed  at  the  bottom  of  the  intermaxillary 
space. 

The  posterior  extremitg,  or  base  of  the  tongue,  is  limited,  in  the  interior  of 
the  mouth,  by  a  furrow  which  borders  the  base  of  the  epiglottis.  It  presents 
a  thick,  median,  mucous  fold,  plaited  in  difl'erent  ways,  and  carried  over  the 
anterior  aspect  of  the  epiglottic  cartilage.  Two  other  folds,  more  anterior,  also 
formed  by  the  buccal  membrane,  unite  with  the  soft  palate  on  each  side  of  the 
base  of  the  tongue  ;  these  are  the  posterior  pillars  of  the  organ  (or  the  glosso- 
epiglottic  ligaments  of  Man),  and  comprise  in  their  substance  a  voluminous 
collection  of  glands.  Behind  these  pillars  are  two  triangular  spaces,  included 
between  the  velum  pendulum  palati  and  the  base  of  the  tongue,  each  of  which 
has  an  excavation  perforated  with  openings — a  veritable  amygdaloid  cavity — which 
represents  the  amygdalce  (tonsils)  of  Man  and  the  Carnivora  ;  it  is  a  kind  of 
common  confluent  for  the  numerous  glandulae  accumulated  outside  the  mucous 
membrane  that  lines  this  excavation. 

The  anterior  extremity  of  the  tongue  is  quite  free,  from  the  middle  of  the 
interdental  space,  and  moves  at  liberty  in  the  interior  of  the  buccal  cavity  :  it  is 
also  termed  the  free  portion  of  the  tongue,  in  distinction  to  the  remainder  of 
the  organ,  which  is  named  the  fixed  portion.  This  free  portion  is  flattened 
above  and  below,  and  slightly  widened  or  spatulated.  Its  superior  face  is 
plane,  or  nearly  so,  and  prolongs  that  of  the  fixed  portion.  The  inferior, 
slightly  convex,  and  perfectly  smooth,  is  continuous  with  the  lateral  faces  of 
the  organ,  and  rests  on  the  body  of  the  inferior  maxilla  ;  it  is  fixed  to  that  bone 
by  a  median  fold  of  mucous  membrane — the  anterior  pillar,  or  frcBuum  lingvm. 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


The  borders,  in  joining  each  other  in  front,  describe  a  parabolic  curve  which  is 
in  contact  with  the  incisive  arches. 

Structure. — The  tongue  offers  for  study,  in  regard  to  its  structure  :  1.  The 
mucous  membrane  enveloping  the  organ.  2.  The  muscular  tissue  which,  in 
reality,  forms  its  mass.     3.  The  vessels  and  Jierves  distributed  to  it. 

1.  Mucous  membrane. — This  membrane — a  continuation  of  that  lining  the 
mouth — is  reflected  at  the  bottom  of  the  canal  on  the  sides  of  the  tongue,  covers 
the  upper  surface  of  the  organ,  and  envelops  the  whole  of  its  free  portion. 
Its  dermis,  or  corium,  has  not  the  same  thickness  throughout,  but  is  incom- 
parably thinner  and  less  dense  on  the  sides  of  the  fixed  portion  and  the 
inferior  plane  of  the  free  part ;  on  the  dorsum  of  the  tongue  it  is  difficult  to 
cut  it.  Its  deep  face  receives  the  insertion  of  a  large  number  of  the  muscular 
fibres  of  the  organ,  and  for  the  greater  part  of  its  extent  it  adheres  in  the  most 
intimate  manner  to  these  fibres,  though  its  adherence  is  not  so  close  at  those 
points  where  it  is  in  contact  with  the  labial  glands. 

Its  superficial  face  is  not  smooth,  but  shows  a  prodigious  quantity  of  minute 


Fig.  216. 


Fig.  217. 


COMPOSITE   PAPILLA   FROM   THE   TONGUE 
OF    THE    DOG. 

1,  Corium  ;   2,  epithelium. 


SIMPLE   FILIFORM    PAPILLA    FROM    THE 
POINT   OF    THE   HOKSE'S    TONGUE. 

1,  Corium  ;  2,  epithelium. 


prolongations  or  papillce,  which,  accordmg  to  their  shape,  are  distinguished  as 
filiform,  fungiform,  and  calijciform  papillce. 

The  filiform  papillce  (Fig.  217)  are  formed  by  thin  prolongations  terminating  in 
a  point,  each  being  covered  by  an  epithehal  sheath  which  greatly  increases  its 
dimensions.  They  are  simple  or  composite,  having  at  their  summit  secondary  pro- 
longations, much  smaller,  and  provided  also  with  an  epithelial  covering.  These 
filiform  papillfe  are  largest  on  the  middle  part  of  the  dorsum  of  the  tongue,  where 
they  present  a  tufty  appearance  ;  towards  the  point  of  the  organ  they  are  embedded 
in  epithelium,  and  are  scarcely  apparent  in  the  minute  elevations  on  its  surface. 

The  fungiform  pcqnllcB  (p.  capitatce)  (Fig.  219,  2)  are  club  or  sponge-shaped 
elevations  of  the  derm,  attached  to  the  membrane  by  a  short  pedicle.  Their 
surface  is  convex  and  smooth,  or  studded  with  filiform  papillifi.  They  are 
scattered  irregularly  over  the  dorsum  of  the  tongue,  among  the  filiform  papillae, 
and  are  most  numerous  on  the  posterior  third  of  its  surface. 

The  calyciform  papillcB  (fossuJate,  circumvallate,  or  Jetiticular  pa^nllce)  (Fig.  219) 
are  really  f imgif  orm,  but  instead  of  projecting  above  the  free  surface  of  the  dermis, 
they  are  placed  in  a  depression  in  this  membrane.  They  are  surrounded  by  a 
slightly  elevated  ring,  within  which  is  a  narrow  fossa  around  the  pedicle  of  the 
papilla  ;  several  papiUae  may  be  contained  within  one  cup-shaped  cavity.     They 


THE  MOUTH. 


403 


only  exist  at  the  base  of  the  tongue,  where  two  of  their  number,  very  developed 
and  composite,  correspond  to  the  blind  foramina  of  Morgagm  (foramen  ctecum). 
At  the  base  of  a  certain  number  of  the  fungiform  and  calyciform  papillae  is  a 
band  of  adenoid  tissue. 

It  is  generally  beheved  that  these  three  kinds  of  papillae  have  each  a  distinct 
function ;  the  filiform  are  to  retain  the  alimentary  and  sapid  substances  on  the 
surface  of  the  tongue,  the  fungiform  are  tactile  organs,  and  the  calyciform  are 
gustatory. 

2.  Muscles. — Beneath  the  mucous  membrane,  on  the  dorsal  surface  of  the 
tongue,  is  a  cylindrical  fibrous  cord,  which  sometimes  attains  the  thickness  of  a 
large  goose-quill.  This  cord  is  situated  in  the  median  plane,  near  the  middle 
part  of  the  organ,  and  is  from  2  to  3  inches  long.  It  may  be  considered  as  a 
fibrous  support  to  the  muscular  tissue,  and  it  sometimes  directly  adheres  to  the 
deep  surface  of  the  mucous  membrane.    At  other  times,  it  is  only  connected 


Fig.  218. 


FORAMEN  OF  MORGAGNI  IN 
THE  horse's  tongue  (SEEN 
FROM  above). 


VERTICAL    section    OF   A   FORAMEN    C^CUM    OF   THE 
horse's   TONGUE. 

1,  1,  Borders  of  the  calyx  ;  2,  fungiform  papillsc  occupying 
it ;  3,  section  of  the  ring  of  lymphoid  tissue  ;  4,  racemose 
glands ;  5,  muscular  fibres  of  the  tongue. 


with  that  membrane  by  a  very  short  lamellar  prolongation,  and  is  then  buried  a 
little  deeper  among  the  fibres  of  the  superior  muscular  layer. 

(The  German  hippotomists  designate  this  the  cartilage  of  the  tongue.  It  is 
only  found  in  Solipeds,  and  was  first  described  by  Briihl,  who  gave  it  this  desig- 
nation. Leyh  states  that  it  is  composed  of  dense  fibro-cartilage,  surrounded  by 
connective  and  adipose  tissue  ;  that  it  is  from  4  to  7  inches  long,  and  f  to  1  inch 
in  thickness  ;  and  that  it  commences  about  an  inch  from  the  anterior  appendix 
of  the  hyoid  bone.) 

A  similar  cord,  but  not  so  strong  or  well-defined,  is  sometimes  found  at  the 
inferior  surface  of  the  free  portion  of  the  tongue. 

Intrinsic  muscles. — In  studying  the  proper  substance  of  the  tongue  in  two 
sections — one  vertical  and  longitudinal,  the  other  transverse — there  is  seen, 
under  the  dorsal  mucous  membrane,  a  layer  of  red  fibres,  close  in  their  texture, 
and  very  adherent  to  that  membrane.  Amongst  these  fibres,  there  are  some 
which  aifect  a  longitudinal  direction,  but  the  majority  are  vertical  or  transverse, 
and  all  are  interlaced  in  the  most  intimate  manner.  It  appears  as  if  this  layer 
(the  lingualis  superficialis  of  Man)  were  perfectly  independent  of  the  other 
muscular  fibres,  the  insertion  of  which  it  receives.  It  also  forms  a  portion  of 
those  which  writers  have  named  the  intrinsic  muscles  of  the  tongue,  and  which 


404  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

comprise  a  superior  and  inferior,  a  transverse  and  a  vertical  linguaUs  muscle, 
found  on  the  inferior  aspect  of  the  free  portion  of  the  organ.  An  attentive 
examination,  however,  reveals  that  the  fibres  proper  to  this  submucous  layer  are 
continuous  with  those  which,  coming  from  a  point  situated  beyond  the  tongue, 
form  the  muscles  named,  in  consequence,  extrinsic,  and  that  they  are  only  the 
prolongations  of  these.  This  division  of  the  tongue  into  two  orders  of  muscular 
fasciculi  does  not,  for  this  reason,  possess  the  importance  generally  accorded 
to  it. 

Extrinsic  muscles. — If  the  muscular  fibres  of  the  tongue  appear  to  be  one 
mass  in  the  superior  layer  just  referred  to,  it  is  not  so  when  they  are  followed 
beyond  this  layer  ;  on  the  contrary,  we  see  them  separate  from  one  another,  and 
even  admit  between  them — at  least  in  the  fixed  portion — a  certain  amount  of 
adipose  tissue,  which  is  particularly  abundant  towards  the  base,  where  it  forms 
a  mass  called  the  fattij  nucleus  of  Baur  ;  then  they  collect  into  fasciculi,  or  per- 
fectly distinct  muscles. 

In  Solipeds,  these  muscles  number  five  pairs  :  1.  The  stylo-glossus.  2.  The 
great  hyo-  or  hasio-glossus.  3.  The  genio-glossus.  4.  The  small  hyo-glossus 
(the  superior  lingual  of  some  authorities).     5.  The  pharyngo-glossus. 

Stylo-glossus  (Hyo-glossus  Longus)  (Fig.  220,  1). 

Synonym. — Kerato-glossus  externus — Leyh.     The  stylo-glossus  of  Man. 

This  is  a  very  long  riband-shaped  band,  formed  of  bright-red  parallel  fibres, 
and  extending  from  the  styloid  bone,  or  great  cornu  of  the  os  hyoides,  to  each 
side  of  the  free  extremity  of  the  tongue. 

It  arises  from  the  external  surface  of  the  large  cornu,  near  its  inferior 
extremity,  by  a  very  thin  aponeurosis  ;  it  terminates  near  the  tip  of  the  tongue, 
in  expanding  over  the  inferior  surface  and  borders  of  the  organ,  and  mixes  its 
fibres  with  those  of  the  opposite  muscle. 

In  the  fixed  portion  of  the  tongue,  this  muscle  is  related  :  outwardly,  to  the 
mylo-hyoideus,  sublingual  gland,  hngual  nerve,  and  the  Whartonian  duct  ;  m- 
wardly,  to  the  genio-glossus  and  great  hyo-glossus  muscles.  The  whole  of  its 
free  portion  is  covered  by  the  buccal  membrane. 

In  contracting,  this  muscle  pulls  the  tongue  towards  the  back  of  the  mouth  ; 
it  inclines  it  to  one  side  when  acting  independently  of  its  fellow  on  the  opposite 
side. 

Great  Hyo-glossus,  Basio-glossus  (Hyo-glossus  Brevis)  (Fig.  220,  2). 

Synonym. — Hyo-glossus — Leyh. 

A  wide  muscle,  flattened  on  both  sides,  thicker  than  the  preceding,  and  com- 
posed of  fibres  passmg  obliquely  forward  and  upward,  the  longest  of  which  are 
anterior. 

Its  origin  occupies  the  whole  side  of  the  body  of  the  os  hyoides,  from  the 
extremity  of  the  cornu  to  that  of  the  spur  process.  Its  fibres,  after  becoming 
detached  from  this  point  of  insertion,  are  insinuated  beneath  the  preceding 
muscle,  spread  out  under  the  mucous  membrane  covering  the  lateral  aspect  of 
the  tongue,  and  for  the  most  part  are  reflected  inwards,  nearly  to  the  superior 
face,  to  constitute  the  transverse  fibres  of  the  organ. 


THE  MOUTH. 


405 


It  is  in  relation,  outwardly,  with  the  mylo-hyoideus,  stylo-glossus,  the  great 
hypo-glossal  nerve,  Wharton's  duct,  and  the  hngual  mucous  membrane  ;  inwardly, 
with  the  small  hyo-glossus,  the  small  cornu  of  the  os  hyoides,  the  pharyngo- 
glossus,  genio-glossus,  lingual  artery,  the  terminal  divisions  of  the  glosso-pharyn- 
geal  nerves,  and  great  and  small  hypo-glossals. 

It  retracts  the  tongue  in  depressing  its  base,  according  as  it  acts  singly  or 
simultaneously  with  its  fellow. 

(In  1850,  Briihl  described  as  the  middle  descending  sft/Io-glossus,  a  long, 
narrow  muscle  arising  from  the  lower  extremity  of  the  inner  face  of  the  styloid 
bore,  or  large  cornu  of  the  os  hyoides,  and  terminating  near  the  tip  of  the  tongue, 
where  it  is  covered  by  the  hyo-glossus.  It  has  since  been  described  as  the 
internal  or  small  kerato-glossus.     Its  action  is  the  same  as  the  stylo-glossus.) 

Genio-glossus  (Genio-hyo-glossus)  (Fig.  220,  4). 

This  is  a  beautiful  muscle,  the  fibres  of  which  are  disposed  Uke  a  fan  in  the 
vertical  and  median  plane  of  the  tongue. 

It  arises  from  the  inner  surface  of  the  lower  jaw,  near  the  symphysis,  by  a 


MUSCLES   OF   THE   TONGUE,   SOFT   PALATE,    AND    PHARYNX. 

1,  Stylo-glossus ;  2,  great  hyo-glossus ;  3,  the  same,  covered  by  the  submucous  layer  formed  by  the 
expansion  of  the  small  hyo-glossus ;  4,  genio-glossus  ;  5,  pharyngo-glossus  ;  6,  palato-pharyngeus  ; 
7,  hyo-pharyngeus ;  8,  thyro-pharyngeus ;  9,  crico-pharyngeus ;  10,  oesophagus;  11,  12,  tensors 
palati ;  13,  stylo-hyoideus ;  14,  hyoideus  magnus ;  15,  genio-hyoideus ;  16,  hyo-thyroideus  [ 
17,  sterno-thyroideus  ;  18,  crico-thyroideus. 


tendon  parallel  to  that  of  the  genio-hyoideus.  From  this  tendon  are  detached 
a  multitude  of  divergent  fibres  which  pass  backwards,  upwards,  and  forwards,  to 
reach  the  upper  surface  of  the  tongue,  and  become  continuous  with  the  vertical 
fibres  of  the  submucous  layer. 

The  two  genio-glossi  lie  together  on  the  median  plane  of  the  tongue,  except 
towards  their  origin,  where  they  are  constantly  kept  apart  by  adipose  tissue. 
Their  inferior  border  responds  to  the  genio-hyoid  muscles,  and  their  anterior 
fibres  are  partly  included  between  the  two  mucous  layers  of  the  frgenum  linguae. 
They  are  related,  by  their  external  face,  to  the  great  hyo-glossus,  the  stylo-glossus, 


406 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


the  sublingual  gland,  the  lingual  artery,  and  the  terminal  branches  of  the  three 
lingual  nerves. 

The  action  of  the  genio-glossus  is  complex  ;  according  to  the  portion  of  its 
fibres  which  contract,  it  will  carry  the  tongue  forwards,  pull  it  into  the  buccal 
cavity,  or  draw  it  downwards  into  the  floor  of  the  mouth. 

Small  Hyo-glossus  (Lingualis)  (Fig.  220,  3). 

Synonym. — Lingualia  superior  of  Man. 

Under  this  name  is  described  a  thin  band,  formed  of  parallel  fibres,  which  is 
exposed  immediately  on  removing  the  mucous  membrane,  with  the  subjacent 
glands,  from  the  base  of  the  tongue.  This  band  arises  from  the  inner  side  of 
the  articulation  uniting  the  body  of  the  os  hyoides  to  its  small  cornu.    It  passes 


Fig.  222. 


Fig.  221. 


ONE   LOBE   OF   A  RACE- 
MOSE  GLAND.  FOLLICULAR  GLAND   FROM   THE   ROOT  OF  THE 
1,  Envelope  of  connec-  tongue. 

tive  tissue;  2  excre-  j^  Epithelium;    2,  papilla   of  mucous  mem- 

tory  duct ;  3,  glandu-  ^rane  ;  3,  cavity  of  the  follicle  ;  4,  invest- 

lar  vesicle,  or  acini.  j^g  ^^s^t  of  the  gland  composed  of  connective 

tissue  ;    5,  fibro-vascular  matrix,  forming  its 

parenchyma,    and    containing,    6,    6,    the 

closed  capsules  or  follicles. 

above  the  transverse  muscle  of  that  bone,  which  it  crosses  perpendicularly,  is 
surrounded  at  this  point  by  a  great  mass  of  adipose  tissue,  and  is  prolonged 
directly  forward,  beneath  the  lingual  mucous  membrane.  Its  fibres  then  vanish, 
either  on  the  superior  aspect  of  the  tongue  or  on  its  sides,  or  they  descend 
obliquely  in  crossing  the  direction  of  the  hyo-glossus,  to  join  the  superior  border 
of  the  stylo-glossus. 

(This  muscle  contracts  and  retracts  the  tongue.) 


Pharyngo-glossus  (Palato-glossus)  (Fig.  220,  5). 

A  rudimentary  muscle  formed  of  parallel  fibres,  which,  from  their  origin  on 
the  lateral  wall  of  the  pharynx,  pass  outside  the  articular  angle  of  the  branches 
of  the  OS  hyoides,  and  between  the  hyo-glossus  and  genio-glossus,  mixing  with, 
and  intercrossing  their  fibres. 

3.  Labial  glands. — The  numerous  glands  of  the  tongue  may  be  divided  into 
racemose  (or  lobulated)  glands,  and  closed  follicles  (or  follicular  glands). 


TEE  MOUTH.  407 

Th&racemose  glands  (Fig.  221)  are  spread  on  the  sides  and  base  of  the  tongue. 
Near  its  upper  border  they  form  two  rows,  which  are  rendered  visible  by  the 
presence  of  a  small  tubercle  placed  beside  each  of  them.  At  the  base  of  the  tongue 
they  are  found  beneath  the  fungiform  and  calyciform  papillae,  as  well  as  beneath 
the  layer  of  closed  follicles  which  lines  the  isthmus  of  the  fauces. 

At  the  entrance  to  this  passage,  the  lingual  mucous  membrane  is  mammillated, 
and  each  elevation  has  an  orifice.  This  arrangement  is  connected  with  the 
presence,  at  this  part  of  the  tongue,  of  the  closed  follicles  (Figs.  222,  223),  which 
are  more  or  less  voluminous  and  aggregated,  and  separated  from  the  muscles  by 
a  continuous  layer  of  racemose  glands.  They  are  composed  of  an  envelope  of 
dense  connective,  and  a  mass  of  adenoid  tissue,  which  has  in  its  centre  a 
cavity  that  communicates  with  the  orifice  above  the  follicle,  and  is  lined  by  the 
lingual  epithelium,  minus  its  horny  layer. 

4.  Vessels  and  nerves. — The  tongue  is  supplied  with  blood  by  two  arteries, 
the  lingual  and  sublingual;  the  blood  is 
removed  by  three  large  veins,  two  of  which 
enter  the  external  maxillary,  and  the  third 
the  internal  maxillary  vein.  The  lymphatics 
constitute  a  very  fine  superficial  network, 
the  emergent  branches  of  which  pass  to 
the  submaxillary  glands.  The  7ierves  are 
the  Ungual,  the  glosso-pharyngeal,  and 
the  great  hypo-glossal ;  the  latter  is  a 
motor  nerve,  and  consequently  supplies  the 
muscles  ;  the  others  are  exclusively  sensi-  ^ 

'  T    ,     -1      .     1  •       ,       ,  SECTION   OF   AN   AMYGDALOID   FOLLICLE 

tive,  and  are  distributed  more  particularly  of  the  horse's  tongue. 

to  the  mucous  membrane.  1^  Follicle  cut  through  the  middle ;  2,  follicle 

Functions. — The    tongue     serves    for  divided  beyond  its  centre ;  3,  section  of  a 

the  prehension  of  liquids  in  all  animals,  '■"''°'°''  ^^"^'^ '  *'  ^'''''• 
and  for  solid  ahment  in  the  Ox.  It  concurs,  with  the  jaws,  in  propelling  the 
substances  to  be  crushed  between  the  molar  teeth  during  mastication  ;  and 
it  is,  besides,  one  of  the  essential  organs  of  deglutition.  It  is  able  to  play  this 
important  and  complex  part,  through  the  varied  movements  it  can  execute  in  the 
interior  of  the  mouth  ;  and  the  extent  of  these  movements  demands  a  moment's 
notice.  They  are  of  two  kinds  :  those  which  influence  only  the  form  of  the 
organ,  and  those  which  cause  it  to  submit  to  various  displacements.  They  result 
in  either  compressing  it  from  side  to  side,  above  to  below,  or  curving  it  longi- 
tudinally, and  even  transversely.  These  movements  are  principally,  but  not 
exclusively,  due  to  the  action  of  the  intrinsic  fibres  ;  they  are  perfectly  indepen- 
dent of  the  movements  which,  as  a  whole,  produce  the  total  displacement  of  the 
tongue.  With  regard  to  these  latter,  they  may  result  in  carrying  the  tongue 
beyond  the  mouth,  or  withdrawing  it  into  that  cavity,  inclining  it  to  one  side, 
raising  it  against  the  palate,  depressing  it  on  the  floor  of  the  mouth,  or,  finally, 
lifting  it  towards  the  pharynx.  It  is  worthy  of  remark  that  these  movements 
do  not  alone  result  from  the  action  of  the  proper  Ungual  muscles  above  described  ; 
those  belonging  to  the  os  hyoides,  to  which  is  attached  the  spur  process, 
concur  also  in  producing  them.  But  this  process  is  not  the  only  organ  thus 
attached  to  the  hyoideal  apparatus  ;  the  larynx  and,  through  it,  the  pharynx,  are 
placed  in  the  same  conditions,  and  are  obliged  to  follow,  like  the  tongue,  the 
movements  of  the  bony  framework  supporting  them. 


408  TEE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

There  consequently  results,  between  these  three  organs,  a  remarkable  unity 
of  action,  which  is  readily  explained  by  the  part  they  all  take  in  the  one  common 
act  of  deglutition. 

5.  Soft  Palate  (Figs.  215,  224). 

Preparation.— Tihe  soft  palate  is  studied  :  1.  On  the  antero-posterior  and  vertical  section  of 
the  head  (Fig.  220).  2.  On  the  portion  intended  to  show  the  interior  of  the  pharynx  (see  the 
preparation  of  this  region).  3.  On  the  portion  represented  in  Fig.  215,  the  mode  of  dissecting 
which  has  been  indicated  at  page  399 ;  in  removing  the  mucous  membrane  and  glandular 
layer,  the  fibrous  membrane  and  the  two  intrinsic  muscles  are  exposed.  The  extrinsic  muscles 
should  be  studied  with  those  of  the  pharynx. 

Situatio7i — Form. — The  soft  palate  {palatum  molle,  velum  pendulum  palati)  is 
suspended  hke  a  partition  between  the  mouth  and  the  pharynx,  and  by  its 
posterior  border  circumscribes  the  orifice  that  establishes  a  communication 
between  these  two  cavities. 

This  partition,  which  continues  the  hard  palate  posteriorly,  represents  in  its 
external  form  a  membranous  valve,  oblique  downwards  and  forwards,  much 
longer  than  it  is  wide,  and  exhibiting  for  study  two  faces  and /<??«•  borders. 

The  inferior  or  anterior  face,  towards  the  mouth,  shows  longitudinal  folds 
and  transverse  ridges,  with  multitudes  of  orifices  belonging  to  the  submucous 
glandulas.  On  its  sides  it  is  united  to  the  base  of  the  tongue  by  means  of  two 
thick  mucous  columns,  designated  the  posterior  pillars  of  the  tongue.  The 
superior  or  posterior  face  forms  the  anterior  wall  of  the  pharynx  ;  it  only  exhibits 
some  very  shght  longitudinal  ridges. 

The  two  latercd  borders  are  inserted  into  the  walls  of  the  two  cavities  which 
the  soft  palate  separates.  The  anterior  border,  continuous  with  the  palate,  is 
attached  to  the  palatine  arch,  and  follows  the  curve  described  by  it.  The 
posterior  border — the  only  free  one — is  concave,  and  closely  embraces  the  base  of 
the  epiglottis,  which  is  usually  found  lying  against  the  posterior  surface  of  this 
curtain.  This  border  is  continued  at  its  extremities  by  two  thin  prolongations, 
which  can  be  followed  on  the  lateral  walls  of  the  pharynx  to  the  oesophageal 
infundibulum,  above  which  they  unite  in  the  form  of  an  arch.  These  prolonga- 
tions are  the  posterior  pillars  of  the  soft  palate,  in  contradistinction  to  the  two 
mucous  folds  at  the  base  of  the  tongue,  which  constitute,  by  their  relation  to 
this  partition,  veritable  anterior  pillars.  This  posterior  border  concurs  in  cir- 
cumscribing what  is  named  the  isthmus  of  the  fauces—  an  aperture  constantly 
closed  in  Solipeds,  in  consequence  of  the  great  development  of  the  soft  palate ; 
it  is  only  dilated  for  the  passage  of  the  alimentary  substances  passing  into  the 
pharynx.  The  isthmus  of  the  fauces  is,  therefore,  not  merely  an  opening  ;  it  is 
a  passage  which  has  for  its  inferior  wall  the  base  of  the  tongue  as  far  as  the 
epiglottis  ;  for  its  upper  wall,  the  anterior  face  of  the  soft  palate  ;  and  for  its 
sides  the  posterior  pillars  of  the  latter. 

Steucture.— To  give  the  most  simple  idea  of  the  structure  of  the  soft 
palate,  it  may  be  said  that  the  mucous  membrane  of  the  palate,  and  that  of  the 
floor  of  the  nasal  cavities,  is  prolonged  behind  the  palatine  arch,  parallel  to  one 
another,  and  become  joined  towards  the  free  border  of  this  curtain  ;  and  it 
might  be  further  shown  that,  in  the  space  between  these  two  mucous  membranes, 
there  is  a  fibrous  membrane,  muscles,  a  glandular  layer,  vessels,  and  nerves ; 
besides  these,  there  are  no  other  elements  in  the  organization  of  the  soft  palate. 


THE  MOUTH.  40S 

They  may  be  studied  in  the  following  order  :  1.  Fibrous  membrane.    2.  Muscles. 
3.  Mucous  membranes.     4.   Vessels  and  nerves. 

1.  Fibrous  membrane  (Fig.  215,  5). — This  membrane,  remarkable  for  its 
power  of  resistance,  forms  a  real  framework  for  the  soft  palate,  of  which  it  only 
occupies  the  anterior  moiety.  It  is  attached  in  front  of  the  palatine  arch,  and  is 
prolonged  posteriorly  by  a  particular  muscle,  the  palato-pharyngeus. 

2.  Muscles. — Of  these  muscles,  which  are  all  pairs,  there  are  those  which 
constitute  a  layer  situated  in  the  middle  of  the  soft  palate  itself,  and  represent 
the  intrinsic  muscles ;  these  are  the  pharyngo-staphylinus  {palato-pharyngeus) 
and  the  palato-staphylinus  {circumflexus  palati).  The  others,  the  peristaphylinus 
— external  and  internal  {tensors  palati  external  and  internal),  are  only  inserted 

Fig.  224. 


MEDIAN    LONGITUDINAL   SECTION   OF   THE    HEAD    AND    UPPER   PART   OF    NECK. 

1,  Upper  lip;  2,  premaxilla ;  3,  hard  palate;  4,  tongue;  5,  septum  nasi;  6,  nasal  bone;  7,  palatine 
arch;  9,  pterygoid  bone;  10,  epiglottis;  11,  entrance  to  the  Eustachian  tube;  12,  arytenoid 
cartilage;  13,  cricoid  cartilage;  14,  oesophagus;  15,  frontal  bone  and  sinus;  16,  cerebrum; 
17,  corpus  callosum  ;  18,  cerebellum;  19,  sphenoid  bone;  20,  medulla  oblongata;  21,  cervical 
ligament ,  22,  spinal  cord  ;  23,  occipital  bone ;  24,  24,  atlas ;  25,  25,  dentata ;  26,  trachea. 

into  the  organ  by  their  terminal  extremities,  and  therefore  act  as  extrinsic 
muscles. 

Pharjmgo-staphylinus  (Palato-pharyngeus)  (Fig.  215,  6) 

In  removing  the  mucous  and  glandular  layers  which  cover  the  anterior  face 
of  the  soft  palate,  there  is  exposed  a  wide  and  thin  muscular  fasciculus  succeed- 
ing the  fibrous  layer  behind,  and  occupying  the  posterior  half  of  the  entire 
organ.  The  fibres  of  which  this  muscle  is  composed,  mixed  in  the  median  line 
with  those  of  the  muscle  of  the  opposite  side,  are  directed  backwards  and 
outwards,  the  most  posterior  following  the  curve  of  the  free  border  of  the 
curtain.  Arriving  near  the  lateral  border,  they  are  reflected  upwards,  passing 
between  the  pharyngeal  mucous  membrane  and  the  middle  constrictor  of  the 
pharynx,  with  which  it  appears  to  be  confounded  posteriorly  ;  but  with  a  little 
attention  it  can  be  followed  to  the  superior  border  of  the  thyroid  cartilage,  into 


410  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA^ 

which  it  is  inserted,  after  making  a  somewhat  long  track  mider  the  mucous 
membrane  of  the  pharynx. 

This  muscle  stretches  the  curtain,  and  draws  its  free  border  from  the 
oesophageal  inf  undibulum,  during  pharyngeal  deglutition. 

Palato-staphylinus  (Azygos  Uvulae)  (Fig.  215,  7). 

(%nont;m8— Staphyleus— Gi'mrd.  Circumflexm  palati—Percivall.  The  azygos  uvulas  of 
Man.) 

A  small,  elongated,  cyUndrical,  bright-red  muscle,  opposed,  in  the  median 
line,  to  that  of  the  other  side,  and  extending  over  the  inferior  surface  of  the 
preceding,  from  the  palatine  arch  to  the  free  border  of  the  soft  palate,  which  it 
pulls  forward  and  upward  to  dilate  the  isthmus  of  the  fauces.  It  arises  by  a 
small  glistening  tendon,  not  from  the  palatine,  but  from  the  staphyline  aponeu- 
rosis (Fig.  215,  7).  The  fascia  which  the  two  muscles  form  is  for  the  most  part 
covered,  in  its  middle  portion,  by  the  fibres  of  the  tensores  palati. 

Sometimes,  and  especially  in  the  Ass  and  Mule,  the  fibres  of  this  muscle 
are  directly  attached  to  the  palatine  arch,  in  becoming  more  or  less  insinuated 
into  the  substance  of  the  glandular  layer. 

Peristaphylinus  Extemus  (Tensor  Palati)  (Fig.  220,  11) 

(Synonym. — The  circumflexus  of  Man.) 

This  is  a  small,  elongated  muscle,  flattened  on  both  sides,  bulging  in  its^ 
middle,  thin  and  tendinous  at  its  extremities,  and  extending  obliquely  forward 
and  downward  from  the  styloid  process  of  the  temporal  bone,  where  it  has  its 
origin,  to  the  pterygoid  trochlea.  Its  terminal  tendon  glides  and  is  inflected 
inwards  on  this  pulley,  to  be  afterwards  spread  out  and  confounded  with  the 
fibrous  framework  of  the  soft  palate,  which  causes  the  framework  to  represent 
an  expansion  of  the  tendon. 

The  muscle  is  covered,  outwardly,  by  the  pterygoidei  muscles ;  it  is  related, 
internally,  to  the  next  muscle,  which  separates  it  from  the  Eustachian  tube. 

It  is  a  tensor  and  depressor  of  the  aponeurosis  of  the  soft  palate. 

Peristaphylinus  Intemus  (Levator  Palati)  (Fig.  220,  12). 

(Synonyms.— Stylo-pharyngeus—Percivall.     The  levator  palati  of  Man.) 

This  is  formed  by  a  pale  and  thin  band,  which  arises  with  the  preceding 
muscle,  descends  between  it  and  the  Eustachian  tube,  passes  beneath  the 
superior  constrictor  of  the  pharynx,  then  below  the  mucous  membrane  of  the 
pharynx  to  reach  the  soft  palate,  where  it  expands  on  the  anterior  or  posterior 
surface  of  the  palato-pharyngeus,  beneath  the  glandular  layer,  its  fibres  becoming 
mixed,  on  the  median  line,  with  those  of  its  fellow. 

This  is  an  elevator  of  the  soft  palate. 

3.  Glandular  layer.— Thh  layer  is  comprised  between  the  fibrous  membrane 
and  the  anterior  mucous  layer,  becoming  thinner  as  it  is  prolonged  over  the 
intrinsic  muscles  ;  it  does  not  extend  to  the  free  border  of  the  organ.  It  is 
thickest  on  each  side  of  the  median  plane,  where  it  forms  two  lobes,  which  appear 
on  the  anterior  surface  of  the  soft  palate  as  an  elongated  ridge,  much  more 


THE  MOUTH.  411 

marked  in  the  Ass  than  the  Horse.  It  is  worthy  of  notice,  that  the  glands 
composing  this  layer  throw  all  their  secretion  into  the  mouth — that  is,  on  the 
anterior  face  of  the  soft  palate. 

4.  Mucous  membranes. — The  soft  palate  is  covered  on  both  its  surfaces  by  two 
mucous  layere,  one  anterior,  the  other  posterior,  united,  as  has  been  remarked,  at 
the  free  border  of  the  organ.  The  anterior  is  continuous,  above,  with  the  mucous 
membrane  of  the  hard  palate  ;  on  its  sides,  with  that  which  covers  the  base  of 
the  tongue.  In  stracture  it  is  the  same  as  the  buccal  membrane  ;  its  epithelium 
is  stratified  and  tesselated.  The  other  layer  is  nothing  more  than  the  pituitary 
membrane  extended  over  the  posterior  surface  of  the  septum,  and  thence  to 
the  lateral  surfaces  of  the  pharynx.  It  will  be  more  fully  described  with  the 
latter. 

5.  Vessels  and  nerves. — The  soft  palate  is  supplied  with  blood  by  the 
staphyline  and  pharyngeal  arteries.  The  nervous  filaments  this  partition  receives, 
emanate  from  the  fifth  pair  of  cranial  nerves  (superior  maxillary  branch),  and 
from  Meckel's  ganglion ;  they  form  the  staphyline  or  posterior  palatine  nerve 
(Fig.  215,  8). 

Ttie  superior  maxillaiy  branch  is  entirely  sensitive,  and  yet  the  staphyline 
nerve  goes  to  tegumentary,  glandular,  or  contractile  organs.  How  can  it  fulfil 
this  double  function  ?  By  receiving  filaments  from  Meckel's  ganglion,  which  has 
motor  fibres  derived  from  the  facial  nerve. 

Functions. — During  the  act  of  deglutition,  the  soft  palate  is  raised  to 
enlarge  the  isthmus,  and  allow  solids  or  liquids  to  pass  through.  The  description 
given  of  this  septum,  permits  us  to  understand  how  it  plays  the  part  of  a  valve, 
in  rising  freely  while  the  alimentaiy  bolus  or  mouthful  of  fluid  passes  from  the 
mouth  into  the  oesophagus,  across  the  pharyngeal  vestibule,  but  never  allowing  the 
matters  which  have  once  entered  the  oesophageal  canal  to  return  into  the  buccal 
cavity.  Also  why,  when  any  obstacle  is  opposed  to  the  descent  of  aliment  into 
the  oesophagus,  after  it  has  cleared  the  isthmus  of  the  fauces,  or  even  when  the 
animal  vomits,  the  matters  arrested  in  their  passage  or  expelled  from  the  stomach 
are  ejected  by  the  nasal  cavities,  after  flowing  over  the  posterior  surface  of  the 
soft  palate.  This  disposition  of  the  pendulous  curtain,  in  forming  a  complete 
partition  which  hermetically  seals  the  orifice  of  communication  between  the 
mouth  and  pharynx,  likewise  sufficiently  explains  why,  in  normal  circumstances, 
Solipeds  respire  exclusively  by  the  nostrils. 

6.  The  Teeth. 

Passive  agents  in  mastication,  the  teeth  are  hard  organs,  bony  in  appearance, 
implanted  in  the  jaws,  and  projecting  into  the  interior  of  the  mouth,  in  order  to 
bruise  or  tear  the  solid  alimentary  substances. 

Identical  in  all  our  domesticated  animals,  in  their  general  aiTangement,  their 
mode  of  development,  and  their  structure,  in  their  external  conformation  these 
organs  present  notable  differences,  the  study  of  which  offers  the  greatest  interest 
to  the  naturalist.  For  it  is  on  the  form  of  its  teeth  that  an  animal  depends  for 
its  mode  of  alimentation  ;  it  is  the  regime,  in  its  turn,  which  dominates  the 
instincts,  and  governs  the  diverse  modifications  in  the  apparatus  of  the  economy  ; 
and  there  results  from  this  law  of  harmony  a  striking  coiTelation  between  the 
arrangement  of  the  teeth  and  the  conformation  of  the  other  organs. 

Compelled  by  the  limits  of  our  task  to  confine  ourselves  to  the  purely 
descriptive  part  of  the  dental  apparatus,  we  cannot  stop  to  notice  the  interesting 


412 


TEE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


Fig.  225. 


physiological  considerations  on  which  this  principal  is  founded  ;  but  will  begin  at 
once  the  anatomical  study  of  the  teeth,  by  indicating  their  general  characters, 
before  examining  them  successively  in  all  the  domesticated  species. 

A.  General  Characters  of  the  Teeth— General  Arrangement.— 
The  teeth  are  fixed  in  the  jaws,  and  ranged  one  against  the  other  in  such  a  way 
as  to  form  two  parabolic  arches  opening  behind,  and  interrupted  on  each  side  by 
what  is  called  the  interdental  space.  Distinguished  into  superior  and  inferior, 
like  the  jaws  to  which  they  belong,  these  arches  come  in  contact  with  one  another 
in  a  more  or  less  exact  manner  when  the  mouth  is  perfectly  closed. 

Those  teeth  which  are  placed  together  in  front,  at  the 
middle  of  the  dental  arches,  are  named  incisors,  or  incisive 
teeth ;  the  others,  situated  behind  these,  and  always  number- 
ing two  for  each  jaw,  are  called  the  canine  teeth,  or  tusks ; 
while  the  designation  of  molars  is  given  to  those  which 
occupy,  in  the  more  retired  portion  of  the  buccal  cavity, 
the  lateral  parts  and  extremities  of  the  dental  arches. 

External  Conformation. — Each  tooth  represents, 
when  completely  developed,  an  elongated  polyhedron,  which 
has  sometimes  a  pyramidal  form,  and  at  others  that  of  a 
cone  or  parallelopiped. 

A  portion  of  the  tooth  is  buried  and  solidly  implanted 
in  one  of  the  alveolar  cavities  of  the  maxillary  bones  ;  this 
is  the  root,  or  embedded  jwrtion  (or  fang).  The  other  por- 
tion, circumscribed  at  its  base  by  the  gum,  leaves  the 
alveolus  to  project  into  the  mterior  of  the  mouth,  forming 
the  crown,  oy  free  portion.  The  narrow  constriction  between 
the  crown  and  root  is  named  the  neck. 

The  fang  is  perforated  at  its  inferior  extremity  by  one 
or  more  excavations  (cavitaspulpcB),  which  penetrate  deeply 
into  the  substance  of  the  tooth,  and  admit  into  their 
interior  the  vasculo-nervous  papilla,  simple  or  ramified, 
known  by  the  name  of  the  bulb,  or  dental  pulp. 

The  crown,  the  portion  submitted  to  friction  during 
mastication,  and,  consequently,  to  wear,  offers  the  most 
varied  forms  :  sometimes  it  is  shaped  like  a  very  acute  cone  ; 
at  others,  it  is  divided  into  several  tubercles  more  or  less 
salient ;  and  sometimes,  again,  it  bears  at  the  extremity  of 
the  tooth  a  wearing  surface  more  or  less  plane  and  regular. 
Structure. — Three  essentially  different  substances  enter 
into  the  structure  of  all  the  teeth — the  ivory,  enamel,  and 
cement;  to  which  ought  to  be  added  the  soft  parts — ^the 
pulp,  gum,  and  alveolo-dental  periosteum. 

Ivory. — The  ivory,  or  dentine,  has  the  hardness  of  bone, 
is  of  a  whitish-yellow  colour,  and  is  rendered  brilliant  in  places  by  its  nacrous 
reflection.  It  forms  the  principal  mass  of  the  tooth,  enveloping  everywhere  the 
pulp  cavity. 

Examined  by  aid  of  the  microscope,  this  substance  is  found  to  be  channeled 
by  a  multitude  of  minute,  undulating,  and  branching  canals  {dental  canaliculi  or 
tubuli)  embedded  in  amorphous  matter  (the  fundamental  substance). 

The  tubuli,  or  canaliculi,  extend  from  the  dental  cavitv  to  the  inner  face  of 


MAGNIFIED  SECTION  OF 
A  CANINE  TOOTH, 
SHOWING  ITS  INTI- 
MATE  STRUCTURE. 

1,  Crown  ;  2,  2,  neck  ; 
3,  fang,  or  root;  4, 
cavitas  pulpac  ;  5, 
opening  by  which  the 
vessels  and  nerves 
communicate  with 
the  pulp;  6,  6,  den- 
tine, showing  fibrous 
structure ;  7,  7, 
enamel ;  8,  8,  cement. 


THE  MOUTH. 


413 


the  enamel ;  single  at  their  origin,  they  soon  bifurcate,  and  again  anastomose 
several  times  during  their  slightly  undulating  course.  They  terminate  in  a 
cul-de-sac,  or  in  irregular  cavities  situated  beneath  the  enamel,  and  named  the 
interglobular  spaces  of  Gzermak  (forming  the  interglobular  or  nodular  layer). 
These  canals  have  a  thin  proper  wall,  and  contain  a  dental  fibre,  which  very 
probably  is  a  continuation  of  the  pulp-cells.  The  fundamental  substance  (or 
matrix)  is  amorphous,  and  not  very  abundant ;  in  its  mass  are  deposited  the 
saline  molecules  which  give  the  dentine  its  bony  consistency.  (These  molecules 
are  deposited  in  lamellas,  concentric  with  the  pulp  cavity.  Nasmyth  considers 
the  fibres  to  be  rows  of  minute  opaque  points,  arranged  in  a  linear  series 
— baccated  fibres — and  to  be  merely  the  nuclei  of  the  ivory  cells,  the  interfibrous 
substance  being  the  remainder  of  the  cell  filled  with  calcareous  matter.) 

Its  chemical  composition  much  resembles  that  of  bones.     After  remaining 


Fig.  226. 


SECTION   THROUGH    THE   FANG  OF   A    MOLAR   TOOTH. 

A,  a,  Dentine  traversed  by  its  tubuli ;  6,  6,  interglobular,  or  nodular  layer ;  c,  c,  cementum. 

in  dilute  hydrochloric  acid  for  several  weeks,  it  comports  itself  like  them,  by 
giving  up  the  calcareous  salts  with  which  it  is  impregnated  to  the  acid  solution, 
and  becoming  soft  like  cartilage  ;  submitted  to  the  action  of  boiling  water,  it 
yields  gelatine.  The  mineral  matters  of  dentine  differ  from  those  of  bone  in 
having  a  smaller  proportion  of  carbonate  of  lime. 

Enamel. — The  enamel  extends  in  a  layer  over  the  ivory  of  the  free  portion 
of  the  tooth,  the  exterior  of  which  it  entirely  envelops  ;  it  is  prolonged  over 
the  fang  in  some  animals,  and  in  several  kinds  of  teeth  it  dips,  by  the  crown, 
into  the  interior  of  the  organ  to  a  very  great  depth.  It  is  brilliantly  white,  and 
so  hard  that  it  strikes  fire  like  steel. 

Its  microscopic  structure  is  very  interesting,  the  enamel  being  composed  of 
small  prismatic  hexagonal  rods,  s-^oo  of  an  inch  in  diameter,  and  notched 
on  their  faces.  Owing  to  this  notching,  the  prisms  are  intimately  united  to 
each  other.  They  form  several  layers  which  cross  each  other  at  an  acute  angle, 
though  in  each  layer  they  are  exactly  parallel  to  one  another.  By  immersing 
the  enamel  in  dilute  hydrochloric  acid,  there  is  detached  from  its  surface  a  fine 
amorphous  membrane  {cuticle  of  the  enamel). 

(The  chemical  composition  of  enamel  appears  to  be  9 6 '5  per  cent,  of  earthy 
matter,  and  3"5  of  animal  substance.  The  first  consists  of  phosphate  of  lime, 
with  traces — 3  per  cent. — of  fluoride  of  calcium,  carbonate  of  lime,  phosphate 
29 


414  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

of  magnesia,  and  other  salts.     The  rods  are  directed  vertically  on  the  summit 
of  the  crown  of  the  tooth,  and  horizontally  at  the  sides.) 

Cemext  {cementum,  substantia  ostoidea,  cortical  substance,  or  criista 
petrosa). — The  cement  is  spread  in  a  non-continuous  layer  over  the  external 
surface  of  the  enamel  and  dentine.  It  is  accumulated  in  large  quantity  in  the 
substance  of  some  teeth,  as  will  be  noticed  when  speaking  of  the  incisors  in 
the  Horse  and  the  molars  of  the  Herbivora. 

The  structure  and  properties  of  this  substance  differ  in  nothing  from  the 
structure  and  properties  of  the  spongy  tissue  of  bone.  In  a  physiological  con- 
dition, the  cement  does  not  contain  any  Haversian  canals.  (It  contains, 
sparingly,  the  lacunae  and  canaliculi  which  characterize  true  bone  :  those  placed 
near  the  surface  have  the  canaliculi  radiating  from  the  side  of  the  lacunae 
towards  the  periodontal  membrane  ;  and  those  more  deeply  placed  join  with  the 
adjacent  dental  tubuli.  In  the  thicker  portions  of  the  crusta  petrosa,  the  lamellae 
and  Haversian  canals  peculiar  to  bone  are  also  found.  As  age  advances,  the 
cementum   increases   in   thickness,  and   gives  rise   to  those  bony  growths,  or 

exostoses,  so  common  in  the  teeth  of 

^  ig.  227.  ^  ^YiQ  aged  ;    the  pulp   cavity  also  be- 

jj  comes  partially  filled  up  by  a  hard  sub- 

J^^L      1;$4^  n    B    H        stance,  intermediate  between  dentine 

^^^^£/^^^  fjt^^^BH         ^^^  ^^^^ — osfeo-dentine,  or  secondary 

^^W^^Jf^  i^^&r^nd         <?(?»/w?e.     It  appears  to  be  formed  by 

^7^>  ■''V?'^^"         ^^^ffrPf'Q  ^  ^^^^^  conversion  of  the  dental  pulp, 

^l^fr^^r^  Js^^S^^i  which  shrinks  or  even  disappears.) 

jj|^  -Mj/^  pg^^^^0  Dented  pidp. — The  jndp,  or  papilla, 

C^^^  is  formed  by  a  fibrillar  and  nuclear 

mass   that   fills    the    internal   dental 

A,    TRANSVEKSE    SECTION     OF     ENAMEL,    SHOWING  .  t.  •  i  i         i  i  J 

ITS  HEXAGONAL  PRISMS ;  B,  SEPARATED  PRISMS,     cavity.     Itreccivcs  blood-vcssels  aud 

nerves,  and  is  enveloped  in  a  very 
thin  membrane  which  is  entirely  composed  of  several  layers  of  beautiful  cyhn- 
drical  or  prismatic  cells,  the  most  superficial  of  which  send  fibrillar  prolonga- 
tions into  the  dental  tubuli.  Towards  the  base  of  the  papilla,  this  membrane 
assumes  the  texture  of  connective  tissue,  and  is  reflected  upwards  on  the  fang  of 
the  tooth  to  line  the  alveolus,  and  join  the  gum  at  the  origin  of  the  crown. 

Gum. — The  gum  is  a  portion  of  the  buccal  mucous  membrane  surrounding 
the  neck  of  the  tooth  ;  it  concurs  in  consolidating  it  in  the  alveolar  cavity. 
Its  structure  is  that  of  the  membrane  to  which  it  belongs,  being  a  thick  dermis 
furnished  with  papillae  and  tesselated  epithehum.     It   does   not   contain  any 


Alveolo-dental  periosteum. — This  scarcely  differs  from  ordinary  periosteum, 
except  in  being  a  little  softer.  It  lines  the  alveolus  and  covers  the  cementum  of 
the  fang. 

Development. — Each  tooth  is  developed  in  the  interior  of  a  closed  sac  named 
the  dented  follicle  or  sac,^  and  lodged  in  an  excavation  in  the  maxillary  bones. 
The  sac  presents,  according  to  the  species  of  animal  and  kind  of  teeth,  numerous 
variations,  which  we  cannot  stay  to  consider  here  :  but  must  confine  ourselves 
merely  to  a  brief  sketch  of  the  general  and  constant  characteristics  of   its 

'  Two  adjoining  follicles  and  the  papillae  they  contain,  sometimes  join  each  other,  for  we 
have  seen  a  two-years-old  Ass  in  which  the  central  and  lateral  incisors  in  the  inferior  maxilla 
were  united,  so  as  to  form  only  two  teeth,  instead  of  four. 


THE  MOUTE. 


415 


Fig.  228. 


organization.  (For  details,  see  'Embrjologj— Development  of  the  Digestive 
Apparatus.) 

The  dental  follicle  is  constituted  by  an  external  enveloping  membrane  of  a 
cellulo-vascular  nature  (Fig.  228,  a).  It  shows  at  its  bottom  the  simple  or 
compound  papilla,  which  at  a  later  period  is  termed  the  dental  pulp  (b)  ;  this 
organ,  destined  for  the  secretion  of  the  dentine,  then  fills  nearly  the  whole  of 
the  follicle.  In  its  upper  part  is  observed  the  enamel  organ,  or  germ  {enamel 
membrane),  formed  by  a  prolongation  of  the  gingival  epithelium,  and  connected 
with  the  latter  by  a  small  mass  of  cells  named  the  gubernaculum  dentis.  Most 
frequently  there  is,  opposite  the  bottom  of  the  follicle,  one  or  more  papillae 
which,  in  some  cases,  adhere  by  their  whole  length  to  one  of  the  lateral  walls 
of  the  follicular  sac,  and  the  free  extremities  of  which 
cross  those  of  the  dentine  papillse,  or  are  buried  in  a 
kind  of  cup  on  the  summit  of  the  latter  appendages  (c). 
These  are  covered  by  the  membrane  of  cyUndrical  cells 
mentioned  above  (d). 

With  regard  to  the  enamel  organ,  its  internal  face 
also  presents  a  layer  of  cyhndrical  cells. 

It  is  in  the  interval  between  these  two  papillary 
systems  that  the  dental  substance  is  deposited  as  in  a 
mould,  consequent  on  a  process  of  secretion  and  trans- 
formation, the  mechanism  and  progress  of  which  are 
somewhat  comphcated.  The  dentine  is  produced  by  the 
metamorphosis  of  the  superficial  cells  of  the  dental  germ. 
These  cells  send  out  ramifying  prolongations  which  con- 
stitute the  tubuli  of  the  dentine,  and  those  of  the 
middle  layer  secrete  an  intertubular  amorphous  substance, 
in  which  the  earthy  salts  are  deposited  from  without 
inwards.  The  enamel  is  deposited  on  the  dentine,  and 
results  from  the  transformation  of  the  cylindrical  cells 
of  the  germ  into  enamel  prisms.  The  cement  is,  in  its 
turn,  deposited  either  on  the  enamel  or  the  dentine  after 
their  formation,  and  is  produced,  like  the  bony  tissue,  by 
the  internal  face  of  this  (periodontal)  sac,  which  has  be- 
come alveolar  periosteum. 

When  formed  by  the  process  above  indicated,  the  tooth 
pierces  its  follicle  and  appears  in  the  interior  of 
the   mouth,   after    having   traversed    the   table   of   the 

maxillary  bones,  if  there  is  any,  and  the  gingival  membrane.  (When  the 
calcification  of  the  different  tissues  of  the  tooth  is  sufficiently  advanced  to  enable 
it  to  bear  the  pressure  to  which  it  will  be  afterwards  subjected,  its  eruption 
takes  place,  the  tooth  making  its  way  through  the  gum.  The  gum  is  absorbed 
by  the  pressure  of  the  crown  of  the  tooth  against  it,  which  is  itself  pressed  up 
by  the  increasing  size  of  the  fang.  Concurrent  with  this,  the  septa  between 
the  dental  sacs,  at  first  fibrous  in  structure,  soon  ossify,  and  constitute  the 
alveoli  ;  these  firmly  embrace  the  necks  of  the  teeth,  and  afford  them  a  solid 
basis  of  support.)  Though  it  has  so  far  become  estabhshed  in  its  functions, 
the  process  of  growth  in  the  tooth  has  not  yet  ceased.  The  pulp  lodged  in  the 
internal  dental  cavity,  and  charged  with  the  formation  of  the  ivory  or  dentine, 
continues  its  functions — incessantly  depositing  new  layers  on  those  which  were 


THEORETICAL  SECTION  OP 
THE  DENTAL  SAC  OF  A 
PERMANENT  INCISOR  IN 
THE    HORSE. 

A,  Proper  membrane  of  the 
sac;  B,  dental  pulp;  C, 
papilla  of  the  external 
cavity  (pit)  of  the  tooth, 
a  dependency  of  the  ena- 
mel membrane  ;  D,  epi- 
thelial layer  of  the  den- 
tme  membrane  ;  E,  cy- 
lindrical cells  of  the 
enamel  membrane ;  F, 
dentine  ;  G,  enamel. 
The  secretion  of  the  ce- 
ment is  not  supposed  to 
have  commenced. 


416  TEE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

originally  secreted.  The  dental  cavity  gradually  diminishes  in  extent ;  the 
papilla  becomes  atrophied,  and  finishes  by  disappearing  altogether  at  a  period 
of  life  more  or  less  advanced,  according  to  the  kind  of  teeth  and  species  of  the 
animal. 

.  In  considering  the  entire  dental  apparatus,  with  regard  to  its  development, 
very  interesting  differences  are  remarked  in  the  progress  and  period  of  evolution 
— differences  which  have  been  made  available  for  ascertaining  the  age  of  animals, 
but  the  details  of  which  would  be  out  of  place  here.  It  may  only  be  noted  that 
all  animals  have  two  successive  dentitions  :  the  first,  composed  of  a  certain 
number  of  teeth  designated  the  caducous  (temporary,  deciduous,  or  milk-teeth — 
caduques,  decaying  or  frail),  because  they  are  soon  shed  and  give  place  to  others 
which  are  stronger  and  more  solid  (and  also  because  they  appear  while  the 
animal  is  yet  sucking)  ;  the  second,  comprising  the  latter,  are  named  replacing 
teeth,  with  new,  non-deciduous  teeth  which  are  not  replaced,  and  are  therefore 
named  persistent  teeth.  (The  replacing  and  persistent  teeth  are  generally  included 
by  us  in  the  term  permanent.) 

The  teeth  of  Solipeds  are  gradually  pushed  from  their  alveoH  as  they  grow  ; 


^100 

THIN   SECTION   OF   THE   INNER   PORTION   OF   THE   DENTINE    AND   OF   THE   SURFACE   OF   THE    PULP 
OF   AN   INCISOR   TOOTH. 

a,  Portion  in  which  calcification  is  complete,  showing  separate  globular  masses  at  the  line  of  junction 
with  the  uncalcified  substance,  6 ;  at  c  are  seen  oval  masses  of  germinal  matter  (cells),  with 
formed  material  on  their  outer  surface  ;  d,  terminal  portions  of  nerve-fibres. 

and  from  this  circumstance  results  deformity  and  thinning  of  the  maxillae  in  the 
regions  which  lodge  the  roots  of  the  teeth. 

B.  Teeth  of  Solipeds. — The  dentition  of  adult  Solipeds  is  composed  of 
from  36  to  40  teeth,  thus  distributed  in  each  jaw  :  male,  6  incisors,  2  canines, 
12  molars  ;  female,  6  incisors,  12  molars.^  With  regard  to  the  first  dentition, 
it  comprises  the  incisors  and  three  anterior  molars  only,  the  canine  teeth  and 
three  posterior  molars  being  persistent. 

The  latter  teeth — those  of  the  second  dentition — offer  in  their  development 
a  common,  but  very  remarkable  character,  rarely  met  with  in  the  other  animals. 
They  are  pushed  up  from  the  alveoli  during  the  entire  life  of  the  animal,  to 

('  This  is  the  number  of  persistent  teeth  given  by  all  veterinary  authorities,  as  well  as 
by  Professor  Owen.  Huxley,  however,  gives  the  typical  number  in  the  adult  horse  as  forty-four. 
The  first  premolar  is  supposed  to  be  a  persisteut,  and  not  a  deciduous  tooth,  as  it  has  no 
successor.) 


TEE  MOUTH.  417 

replace  the  surfaces  worn  off  by  friction  ;  so  that  the  crown  is  formed  suc- 
cessively by  the  various  portions  of  the  fang,  each  of  which  issues  m  its  turn 
from  the  alveolar  cavity. 

Incisors. — These  are  so  named  because  they  serve,  particularly  in  the 
Herbivora,  for  the  incision  {mcido,  to  cut)  of  the  food.  They  are  arranged 
in  the  segment  of  a  circle,  at  the  extremity  of  the  jaw,  and  are  distinguished 
by  the  names  of  middle  or  central,  intermediate  or  lateral,  and  corfier  teeth.  The 
pincers  are  the  two  middle  teeth,  the  intermediates  the  next,  and  the  corners 
occupy  the  extremities  of  the  incisive  semicircle. 

The  general  form  of  these  teeth  is  that  of  a  trifacial  pyramid,  presenting 
a  curve  with  its  concavity  towards  the  mouth.  The  base  of  this  pyramid, 
formed  by  the  crown,  is  flattened  before  and  behind  ;  the  summit,  or  ex- 
tremity of  the  fang,  is,  on  the  contrary,  depressed  on  both  sides  ;  the  shaft 
of  the  pyramid  offers,  at  different  points  of  its  height,  a  series  of  intermediate 
conformations  which  are  utilized  as  characteristics  of  age,  the  continual  pushing 
outwards  of  the  teeth  bringing  each  of  them  in  succession  to  the  frictional 
surface  of  the  crown  (Fig.  232,  1). 

Examined  in  a  young  tooth  which  has  completed  its  evolution,  the  free 
portion  exhibits  :  an  anterior  face,  indented  by  a  slight  longitudinal  groove, 
which  is  prolonged  to  the  root ;  a  posterior  face,  rounded  from  side  to  side  ; 
two  borders,  of  which  the  internal  is  always  thicker  than  the  external ;  lastly, 
the  surface  of  friction  (table).  The  latter  does  not  exist  in  the  tooth  which  has 
not  been  used  ;  but  in  its  stead  are  found  two  sharp  margins  circumscribing  a 
cavity  named  the  external  dental  cavity  (or  better,  infundibidum).  This  cavity 
terminates  in  a  conical  cid-de-sac,  which  descends  more  or  less  deeply  into  the 
substance  of  the  tooth.  The  margins  are  distinguished  into  anterior  and  pos- 
terior ;  the  last,  less  elevated  than  the  first,  is  cut  by  one  or  more  notches  which 
are  always  deepest  in  the  corner  teeth.  It  is  by  the  wear  of  these  margins  that 
the  surface  of  friction  is  formed,  and  in  the  centre  of  which  the  infundibulum 
persists  during  a  certain  period  of  time  (Fig.  232,  2). 

The  fang  is  perforated  by  a  single  aperture,  through  which  the  pulp  of  the 
tooth  penetrates  into  the  internal  cavity  (Fig.  231,  3,  c). 

In  the  composition  of  the  incisor  teeth  is  found  the  three  fundamental  sub- 
stances of  the  dental  organ.  The  dentine  (Figs.  231,  i ;  232,  3)  envelops,  as  has 
been  shown,  the  pulp  cavity.  That  which  is  deposited  in  this  cavity  after  the  com- 
plete evolution  of  the  tooth,  to  replace  the  atrophied  pulp,  has  always  a  yellower 
tint  than  the  dentine  of  the  first  formation  ;  it  forms  on  the  table  of  the  tooth 
the  mark  designated  by  Girard  the  dental  star  (Fig.  232,  4,  c).  The  enamel 
covers  the  dentine,  not  only  on  its  free  portion,  but  also  on  the  roots  of  the 
incisors  ;  it  is  not  prolonged,  however,  to  their  extremities,  though  it  is  more  on 
the  anterior  than  the  posterior  face.  It  is  doubled  in  the  external  dental  cavity, 
hning  it  throughout  (Figs.  231  ;  232,  4,  a)  ;  and  when  the  surface  of  friction  is 
established,  there  can  be  perceived  a  ring  of  enamel  surrounding  that  surface, 
and  an  internal  ring  circumscribing  the  infundibulum  :  the  first  circle  forms 
what  is  called  the  encircling  enamel ;  the  second,  the  central  enamel  (Fig.  232, 
4,  a,  b). 

In  the  virgin  tooth,  the  latter  is  continuous  with  the  external  enamel,  and 
passes  over  the  border  which  circumscribes  the  entrance  to  the  infundibulum. 
The  cement  is  applied  over  the  enamel,  Hke  a  protecting  varnish  ;  but  it  does 
not   exhibit  the   same   thickness   everywhere  :    on   the   salient    portions   it   is 


418 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


extremely  thin,  and  does  not  even  exist  when  the  tooth  has  been  submitted 
for  some  time  to  the  friction  arising  from  the  contact  of  the  aliment,  the  lips, 
and  the  tongue.  It  is  more  abundant  in  depressed  situations,  as  in  the  longi- 
tudinal groove  on  the  anterior  face,  and  particularly  at  the  bottom  of  the 
infundibulum.  Nevertheless,  the  quantity  accumulated  in  this  cul-de-sac  is 
not  always   the  same  ;   we  have  seen  it  sometimes  almost  null,  and  on  the 


Fig.  230. 


Fig.  231. 


SECTION  OF  THE  INCISOR  TOOTH 
OF  A  HORSE,  SHOWING  THE 
ARRANGEMENT  OF  ITS  DIF- 
FERENT  SUBSTANCES. 

I,  Dentine  ;  E,  enamel ;  0,  ce- 
ment. 


other  hand  we  possess  incisors  unworn,  or  nearly 
so,  in  which  the  cavity  is  almost  entirely  filled 
by  the  crusta  petrosa.  We  are  not  aware  that, 
up  to  the  present  time,  any  account  has  been 
taken  of  these  differences  when  calculating  the 
progress  of  wear;  but  it  may  be  imagined  that 
they  ought  to  influence  in  a  sensible  manner  the 
period  at  which  effacement  of  the  external  dental 
cavity  takes  place. 

All  the  characteristics  just  indicated  belong  to 
the  deciduous  teeth  (Fig.  232,  5),  except  that  they 
are  smaller  than  the  permanent  ;  that  they  are  of 
a  shining  milky-white  colour,  due  to  the  thinness 
or  absence  of  the  crusta  petrosa  ;  that  they  show 
at  the  point  of  union  between  the  free  portion  and 
the  root,  a  constriction  named  the  neck ;  that  their 
crown  is  finely  striated,  and  not  cannular,  on  the 
anterior  face  ;  that  the  external  cul-de-sac  (wfun- 
dibulum)  is  shallow  ;  and  that  they  are  not  constantly  pushed  outwards  from 
their  cavities,  their  growth  ceasing  when  they  begin  to  be  used.  When  the 
replacing  teeth  appear,  they  do  so  a  little  behind  the  temporary  ones,  the  shedding 
of  which  they  cause  by  gradually  destroying  their  roots,  these  at  last  becoming 
only  a  long  and  very  thin  shell  of  dentine. 

The  follicle  in  which  the  incisor  teeth  are  developed  shows  only  two  papillae 


DENTITION  OF  THE  INFERIOR  JAW 
OF  THE  HORSE,  THE  TEETH  SEEN 
ON   THEIR   TABLES. 

Consult  Fig.  38  for  the  dentition 
of  the  upper  jaw. 


THE  MOUTH. 


41& 


one  for  the  secretion  of  the  dentine,  lodged  in  the  internal  cavity  of  the  tooth, 

and  hollowed  into  a  cup-shape  at  its  free  extremity  ;  the  other  contained  in  the 
external  cul-de-sac  (Fig,  228,  a,  b,  c). 

Tusks,  Fangs,  or  Canine  Teeth. ^ — "  The  tusks  of  Solipeds  only  exist  in 
the  male  ;  it  being  quite  exceptional  to  meet  with  them  in  the  female,  and  even 
then  they  are  rarely  so  strong  as  in  the  male. 

"  These  teeth  are  four  in  number,  and  are  placed  one  at  each  side  of  the 
jaws,  a  little  behind  the  incisors,  to  which  the  lower  canines  are  much  nearer 


Fie.  2"2. 


INCISOR   TEETH   OF   THE    HORSE  (DETAILS   OF   STRUCTURE). 

1,  A  tooth  in  which  is  indicated  the  general  shape  of  a  permanent  incisor,  and  the  particular  forms 
successively  assumed  by  the  dental  table  in  consequence  of  friction,  and  the  continued  pushing 
outwards  of  these  teeth.  2,  A  virgin  tooth,  anterior  and  posterior  faces.  3,  Longitudinal  section 
of  a  virgin  tooth,  intended  to  show  the  internal  conformation  and  structure.  Not  to  complicate 
the  figure,  the  external  cement,  and  that  accumulated  in  the  infundibulum,  has  not  been  shown. 
4,  Transverse  section  for  the  same  purpose :  a,  Encircling  enamel ;  6,  central  enamel ;  c,  dental 
star  ;  d,  dentine.     5,  Deciduous  tooth. 

than  the  upper.     Between  them  and  the  first  molar  there  is  left  a  considerable 
space,  which  constitutes  the  bar  of  the  inferior  jaw. 

"  The  free  portion  of  the  tusk,  slightly  curved  and  thrown  outwards,  par- 
ticularly in  the  lower  jaw,  offers  two  faces — an  external  and  an  internal — separated 
from  one  another  by  two  sharp  borders  inclined  to  the  inner  side,  and  meeting 
in  a  point  at  the  extremity  of  the  tooth.  The  external  face,  slightly  rounded, 
presents  a  series  of  fine  striae,  longitudinal  and  parallel. 

'  The  quotations  included  within  inverted  commas  are  from  M.  Lecoq's  Traite  de  VExt€rieur 
du  Cheval  et  des  Principaux  Animaux  Domestiques. 


420  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

"  The  internal  face  has  a  conical  eminence  in  its  middle,  whose  point  is 
directed  towards  that  of  the  tooth,  and  is  separated  from  each  border  by  a 
deep  groove. 

"  The  fang  of  the  tusk,  more  curved  than  the  free  portion,  has  internally  a 
cavity  analogous  to  that  of  the  root  of  the  incisors,  and  like  it,  this  diminishes 
and  tinally  disappears  as  it  advances  in  age  ;  but  it  is  always  relatively  larger, 
because  of  the  absence  of  the  infundibulum  in  the  canine  teeth. 

"  The  form  we  have  described  for  the  tusks,  is  that  which  they  present  while 
still  young.  As  the  Horse  grows  older  they  lose  their  whiteness,  and  become 
worn  in  an  irregular  manner,  and  this  most  frequently  by  the  action  of  the  bit 
or  snaffle  ;  for  the  difference  in  position  of  these  teeth  in  the  two  jaws  does  not 
allow  of  friction  between  them. 

"  The  canine  teeth  are  not  shed,  and  grow  but  once.  Some  veterinarians, 
and  among  them  Forthomme  and  Rigot,  have  witnessed  instances  in  which  they 
were  replaced ;  but  the  very  rare  exceptions  cannot  make  us  look  upon  these 
teeth  as  liable  to  be  renewed.  We  must  not,  however,  confound  with  these 
exceptional  cases  the  shedding  of  a  small  spicula  or  point,  which,  in  the  majority 
of  Horses,  precedes  the  eruption  of  the  real  tusks. 

"  The  structure  of  these  teeth  is  much  simpler  than  that  of  the  incisors  ; 
consisting,  as  they  do,  of  a  central  mass  of  dentine  hollowed  by  the  pulp  cavity, 
and  covered  by  an  external  layer  of  enamel,  on  which  is  deposited  a  little 
cement. 

"  The  arrangement  of  the  developing  folHcle  is  in  harmony  with  the  sim- 
plicity of  structure  of  the  tusks  ;  at  the  bottom  there  is  a  simple  and  conical 
papilla  for  the  internal  cavity  ;  on  the  inner  wall,  a  double  longitudinal  ridge, 
on  which  are  moulded  the  ridge  and  grooves  on  the  internal  face  of  the  tooth." 

Molar  Teeth. — "  The  molars  are  twenty-four  in  number — six  in  each  side 
of  each  jaw.  There  are  also  sometimes  supplementary  molars  met  with  in  front 
of  the  true  ones,  and  which  may  be  four  in  number  ;  but  these  are  small  teeth, 
having  but  little  resemblance  to  the  others,  are  most  frequently  shed  with  the 
first  deciduous  molar,  and  are  not  replaced. 

"  Generally  considered,  the  molar  arches  have  not  the  same  disposition  in 
both  jaws.  Wider  apart  in  the  superior  one,  they  form  a  slight  curve,  with  the 
convexity  outwards.  In  the  inferior  jaw,  on  the  contrary,  the  two  arches 
separate  in  the  form  of  a  V  towards  the  back  of  the  mouth.  Instead  of  coming 
in  contact  by  level  surfaces,  the  molars  meet  by  inclined  planes,  and  in  such  a 
way  that  the  internal  border  is  higher  than  the  external  in  the  inferior  molars, 
while  the  opposite  is  the  case  in  the  superior. 

"  Like  the  incisors,  each  molar  presents  for  study  a  free  and  a  fixed  portion. 
The  free  portion,  nearly  square  in  the  upper  molars,  longer  than  wide  in  the 
lower,  shows  at  the  external  surface  of  the  former  two  longitudinal  grooves,  the 
anterior  of  which  is  the  deepest,  and  which  are  continued  on  the  encased  portion. 
This  is  not  so  with  the  inferior  molars,  which  have  but  one  narrow,  and  fre- 
quently an  indistinct,  groove. 

"  The  internal  face  in  both  jaws  only  shows  one  groove,  and  that  but  little 
marked  ;  it  is  placed  backwards  in  the  upper  molars,  and  is  most  apparent 
towards  the  root. 

"  The  anterior  and  posterior  faces  are  in  contact  with  the  corresponding  faces 
of  the  adjoining  molars,  except  at  the  extremities  of  the  arches,  where  the 
isolated  face  is  converted  into  a  narrow  border. 


THE  MOUTH. 


421 


"With  regard  to  the  table  of  the  tooth,  it  inchnes,  as  we  have  already 
mentioned,  outwards  in  the  lower  jaw,  and  inwards  in  the  upper— a  circumstance 
which  prevents  the  lateral  movements  of  the  jaws  taking  place  without  separa- 
tion of  the  incisors,  which  separation  removes  them  from  friction."  In  the  virgin 
molar,  this  face  is  completely  covered  with  enamel,  and  irregularly  undulated. 
In  it  may  be  recognized  the  two  infundibular  openings,  which  are  prolonged  in 
the  interior  of  the  organ  to  the  extremity  of  the  root,  and  are  almost  entirely 
tilled  with  cement  at  the  period  when  the  tooth  has  completed  its  evolution ; 
they  are  only  void  before  the  secretion  of  this  crusta  petrosa.  In  the  tooth 
which  has  been  worn,  this  frictional  surface  assumes  a  particular  aspect,  which 
will  be  indicated  with  most  advantage  to  the  student  by  examining  the  structure 
of  the  molar. 

"  The  root,  if  examined  a  short  time  after  the  eruption  of  the  free  portion, 
looks  only  like  the  shaft  of  the  latter,  without  any  appearance  of  fangs,  and 

Fig.  233. 


PROFILE  OF  THE  UPPER  TEETH  OF  THE  HORSE,  MORE  ESPECIALLY  INTENDED  TO  SHOW  THE 
molars;  the  fangs  have  been  EXPOSED. 

a,  Molai"  teeth  ;  b,  supplementary  molar  ;  c,  tusk  ;  d,  incisors. 

has  internally  a  wide  cavity.  It  is  not  until  the  tooth  begins  to  be  pushed  from 
the  alveolus  and  its  crown  to  become  worn,  that  its  fangs  are  formed  ;  these  are 
at  first  hollow,  and  afterwards  filled,  as  well  as  the  cavity  of  the  tooth,  by  the 
formation  of  a  new  quantity  of  dentine.  From  this  time  the  fangs  cease  to 
grow  ;  but  the  tooth,  constantly  projected  beyond  the  alveolar  cavity,  allows  the 
walls  which  enclose  it  to  contract ;  so  that,  in  extreme  old  age,  it  happens  that 
the  shaft,  completely  worn  away — instead  of  the  tooth — leaves  several  stumps 
formed  by  the  fangs. 

"The  molars  of  the  two  jaws  exhibit  a  variety  of  roots.  In  the  molars 
terminating  the  arches,  either  above  or  below,  or  at  the  extremities  of  these, 
there  are  three  ;  while  the  intermediate  molars  have  four  fangs  in  the  upper  jaw, 
and  only  two  in  the  lower. 

"The  molars  are  separated  from  each  other  by  their  embedded  portion, 
particularly  at  the  two  extremities  of  the  arch ;  an  arrangement  which 
strengthens  them  by  throwing  the  strain  put  upon  the  terminal  teeth  towards 
the  middle  of  the  line." 

The  structure  of  the  molars  resembles  that  of  the  incisors,  though  it  is  much 
more  complicated.  The  internal  cavity  is  extremely  diverticulated,  and  enveloped 
by  the  dentine.  The  enamel  is  applied  in  a  layer  over  it,  and  is  doubled  in  its 
external  culs-de-sac  exactly  as  in  the  incisors.     There  is  also  on  the  table  of  the 


422  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

tooth  which  has  been  worn,  an  external  covering  of  enamel,  and  two  circles,  or 
rather  two  irregular  polygons,  of  central  enamel  circumscribing  the  two  cavities. 
In  the  superior  molars,  these  bands  of  enamel  represent  a  Gothic  B,  having  a 
small  appendage  on  the  loop  nearest  the  entrance  to  the  mouth.  This  hgure  is 
modified  in  the  teeth  of  the  lower  jaw,  the  enamel  of  the  infundibuli  being  con- 
tinuous, on  the  inner  side,  with  the  external  enamel.  The  cement  is  extremely- 
abundant,  and  in  the  upper  molars  its  total  quantity  nearly  equals  that  of  the 
dentine  ;  it  accumulates  in  the  cuh-de-sac  and  on  the  external  covering  of  enamel, 
where  it  partially  fills  up  the  flutings  on  the  faces  of  the  crown.  Prolonged 
steeping  of  a  molar  tooth  in  hydrochloric  acid,  easily  permits  the  isolation  of 
these  elements. 

Owing  to  the  arrangement  above  described,  the  section  of  an  adult  molar 
tooth,  naturally  represented  by  the  surface  of  friction  (Fig.  234),  exhibits,  out- 
wardly, a  layer  of  cement ;  next,  the  external  enamel ;  between  this  and  the 
central  enamel,  the  dentine,  always  yellower,  and  sometimes  even  black  in  the 
middle  ;  lastly,  the  enamel  bands  of  the  infundibuli, 
and  the  crusta  petrosa  filling  them.  As  these  enamel 
bands  are  much  harder  than  the  other  substances,  they 
are  worn  more  slowly,  and  stand  out  in  relief  on  them. 
The  table  of  the  tooth  has  also,  for  this  reason,  the 
appearance  of  a  veritable  mill-stone,  and  is  admirably 
disposed  for  the  trituration  of  those  fibrous  substances 
on  which  the  animal  usually  feeds. 

The  follicle  which  develops  these  three  elements  of 
_  i>  **  the  molar  tooth,  has  at  the  bottom  an  enormous  papilla 

TRANS vKRsii  SECTION  OF  A      divided  iuto  SBVcral  lobes,  which  lie  too-ether  for  their 

horse's      upper      molar  ,11  ^,  1     J        J     •        xi         •     X  1     J        X     1 

TOOTH.  whole  length  ;  lodged  m  the  mternal  dental  cavity,  it 

A,  External  cement ;  B,  ex-     gradually  decreases,  like  the  papilla  in  the  other  kinds 

ternal  enamel ;  0,  dentine;      of   teeth,  as   the   cavity   bccomcs   diminished   by  the 

SmaTrrtt\°pTt'ro.a^' '""     formation  of  new  dentine.     Opposite  to  it  are  two  long 

papillae,  which  occupy  the  enamelled  infundibuli. 

"It  Avas  beheved  for  a  long  time  that  the  molars  of   Solipeds  were  all 

persistent  teeth.     This  error,  founded  on  the  authority  of  Aristotle,  was  so 

deeply  rooted,  that  although  Euini,  towards  the  end  of  the  sixteenth  century, 

had  discovered  the  existence  of  two  temporary  molars,  Bourgelat  did  not  believe 

it  when  he  founded  the  French  Veterinary  Schools,  and  was  only  convinced 

when  Tenon  had  proved  by  specimens,  in  1770,  that  the  first  three  in  each 

arch  are  deciduous. 

"  The  replacement  of  these  twelve  molars  is  not  at  all  like  what  happens  with 
the  incisors.  The  molar  of  the  adult  grows  immediately  beneath  the  temporary 
one,  and  divides  its  two  fangs  into  four,  until  its  body  is  reduced  to  a  simple 
plate  and  falls  off,  allowing  the  contracted  summit  of  the  permanent  molar  to 
appear  ;  and  this  grows  up  until  it  is  soon  on  a  level  with  the  others  in  the  row. 
"  The  first  replacing  molar  is  always  a  little  more  elongated  than  that  which 
it  succeeds,  and  it  most  frequently  expels  at  the  same  time  the  supplementary 
molar  ;  so  that  if  forty-four  teeth  be  developed  in  the  male  Horse,  it  is  very  rare 
that  they  are  all  present  at  the  same  time." 

Ruttimeyer  has  remarked  that  the  tables  of  the  first  three  molars  are  shorter 
and  wider  in  the  Ass  than  in  the  Horse.  The  Gothic  B  the  enamel  forms  is 
consequently  compressed,  and  the  appendage  to  the  anterior  loop  is  wider  in  the 


TEE  MOUTH.  423 

first  than  the  second  of  these  animals,  and  not  so  long.  (Flower  also  observes 
that  the  loop  of  enamel  above  the  B  is  either  absent,  or  scarcely  perceptible  in 
the  Asinine  tribe.) 

7.  The  Mouth  in  Geneeal. 

We  will  now  consider,  as  a  whole,  the  cavity,  the  various  parts  of  which  have 
been  studied  in  detail ;  and  examine,  successively,  its  general  arrangement, ' 
capacity,  and  mucous  membrane. 

General  disposition  and  capacity  of  the  mouth. — The  mouth,  being  elongated 
in  the  direction  of  the  head,  offers  a  great  antero-posterior  diameter,  and  two 
small  diameters — one  vertical,  the  other  transverse.  The  first  extends  from  the 
base  of  the  epiglottis  to  the  anterior  opening  of  the  mouth  ;  the  second,  from 
the  palate  to  the  floor  of  the  mouth  ;  and  the  third,  from  one  jaw  to  the  other. 
"When  the  jaws  are  in  contact,  the  space  included  between  these  limits  is  divided 
into  two  regions  :  one  central,  the  other  peripheral.  The  first  is  circumscribed 
by  the  dental  arches  ;  the  second  is  comprised  between  these  arches  on  the  one 
side,  and  the  cheeks  and  inner  aspect  of  the  lips  on  the  other.  It  may  therefore 
be  remarked,  that  the  capacity  of  the  mouth  is  almost  null  in  these  regions.  The 
cheeks  and  lips,  in  reality,  lie  almost  exactly  against  the  alveolar  arches,  and  the 
tongue,  in  contact  with  the  palate  by  its  superior  surface,  almost  entirely  fills 
the  central  region.  If  the  jaws  separate  from  one  another,  and  the  cheeks  recede 
from  the  dental  arches,  the  cavity  of  the  mouth  becomes  enlarged  in  proportion 
as  these  movements  are  extensive.  It  must  be  remembered  that  the  separation 
of  the  jaws  is  effected  in  an  angular  manner,  and  that  the  dilatation  produced  in 
the  mouth  by  this  movement  is  greater  before  than  behind,  the  opening  of  the 
angle  comprised  between  the  two  jaws  being  directed  towards  the  entrance  to 
the  cavity. 

Mucous  memtrane. — The  walls  of  the  buccal  cavity  are  covered  by  a  tegu- 
mentary  membrane,  which  we  have  hitherto  only  examined  in  parts  in  the 
different  regions  it  covers  ;  but  which,  it  is  to  be  noted,  forms  here  a  single  and 
continuous  layer — the  mucous  membrane  of  the  mouth. 

This  membrane  is  continuous  with  the  external  skin  around  the  margin  of 
the  buccal  opening  ;  from  this  point  into  the  interior  of  the  cavity,  it  extends  at 
first  over  the  internal  surface  of  the  lips,  then  is  prolonged  backwards  on  the 
cheeks  as  far  as  the  posterior  pillars  of  the  tongue.  If  it  is  examined  above  and 
below,  to  the  bottom  of  the  groove  at  the  junction  of  the  lips  and  cheeks,  it  is 
seen  to  cover  the  maxillary  bones  and  envelop  the  base  of  the  teeth,  where  it 
constitutes  the  gums.  From  the  superior  dental  arch,  it  extends  over  the 
palatine  arch  and  the  soft  palate.  And  from  the  inferior  arch,  it  descends  to 
the  floor  of  the  mouth,  and  is  reflected  over  the  tongue  to  form  a  covering  for 
that  organ.  At  the  isthmus  of  the  fauces  it  is  continuous  with  the  pharyngeal 
mucous  membrane. 

The  organization  of  the  mucous  membrane  of  the  mouth  is  perfectly  in 
harmony  with  the  digestive  acts  performed  in  that  cavity.  It  is  there  where 
the  alimentary  substances,  which  are  sometimes  very  hard,  very  resisting,  and 
covered  with  asperities,  are  crushed  ;  and  to  escape  inevitable  injury,  this 
membrane  is  protected  by  a  very  thick  epithelium  in  those  places  which  are 
particularly  exposed  to  the  contact  of  these  substances — such  as  the  upper 
surface  of  the  tongue,  the  palate,  and  the  cheeks  ;  even  the  corium,  or  sub- 
epidermic   layer,  is   also   greatly  thickened.     But   nature  has   not   made   this 


424  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

provision  for  the  parts  which  are  removed  from  the  direct  contact  of  alimentary 
matters — as,  for  example,  on  the  lateral  aspects  of  the  tongue,  where  the  buccal 
membrane  is  delicately  organized. 

This  membrane  also  shows,  in  its  lingual  portion,  small  organs  for  the 
perception  of  savours,  which  is  one  of  the  most  important  preparatory  acts 
of  the  digestive  functions  ;  as  the  sensation  resulting  from  this  appreciation 
constitutes  an  excitant  to  the  desire  for  food,  and  also  informs  the  animal  of  the 
good  or  bad  properties  of  the  substances  introduced  into  the  mouth. 

Differential  Characters  in  the  Modth  of  the  other  Animals 
That  the  diflfL-rent  regions  of  the  mouth  in  the  domesticated  animals  should  offer  some 
diversities,  will  be  leadily  conceived,  as  all  are  not  submitted  to  the  same  regime,  nor  do  they 
all  live  in  tlie  same  manner. 

Ruminants.  1.  Lips.— The  lips  of  the  Ox  are  remarkably  thick  and  rigid,  and  possessed 
of  little  mobility,  notwithstanding  tlie  great  development  of  the  muscles  that  move  them;  so 
that  they  only  concur  indirectly  in  the  prehension  of  food,  the  tongue  being  charged  with  the 
largest  share  in  this  important  task.  The  upper  lip  offers,  in  the  middle  of  its  external  surface, 
a  large  patch  destitute  of  hair,  variously  coloured  in  different  animals,  always  humid  in  health, 
covered  by  small  depressed  eminences,  and  perforated  by  minute  apertures,  through  which 
tlie  secretion  of  numerous  thick,  yellow,  subcutaneous  glandules  passes  to  the  surface.  This 
space,  situated  between  the  two  nostrils,  constitutes  the  muffle.  (Around  the  muffle  are  some- 
times a  few  hairs  of  the  nature  of  tentaculse.) 

In  the  Camel,  Sheep,  and  Goat,  the  lips  are  thin  and  very  mobile,  and  take  an  active 
part  in  the  prehension  of  food.  The  upper  lip  does  not  show  any  muffle,  and  is  divided  into 
two  portions  by  a  median  groove.  In  the  Camel  and  Sheep,  this  groove  is  in  reality  a  fissure ; 
80  that  each  half  of  the  lip  can  be  readily  moved  independently  of  the  other.  (The  upper  lip 
Is  covered  with  hair  in  these  animals.  The  Goat  has  a  long  tuft  of  hair  appended  to  its  lower 
lip,  the  beard.) 

2.  Cheeks. — On  the  inner  surface  of  the  cheeks  in  the  Ox,  Camel,  Sheep,  and  Goat, 
from  the  commissure  of  the  lips  to  the  first  molar  tooth,  is  a  multitude  of  long,  thick,  conical 
papillsB  directed  backwards.  Beyond,  there  are  only  small  round  elevations  and  a  single  row 
of  large  papillae  similar  to  the  pn  ceding,  in  a  line  with  the  upper  molars.  In  the  Sheep  the 
mucous  membrane  is  sometimes  spotted  black ;  in  the  Camel  it  is  uniformly  black. 

3.  Palate. — In  the  Ox,  the  palate  is  most  extensive.  Its  posterior  third  is  quite  smooth, 
and  the  transverse  ridges  (bars)  only  occupy  the  anterior  two-tiiirds.  (They  are  usually 
sixteen  in  number.)  They  are  not  curved,  but  are  cut  into  notches  on  their  summit,  which 
is  inclined  backwards.  In  the  Sheep  and  Goat,  as  also  in  the  Ox,  is  remarked,  in  front 
and  in  the  middle,  near  the  pad  that  replaces  the  upper  incisor  teeth,  a  kind  of  T,  the  stem  of 
which  is  directed  forwards,  and  at  the  extremity  of  its  branches  is  a  very  narrow  aperture,  the 
buccal  opening  of  Jacobson's  canal  (see  the  Nasal  Cavities  for  a  description  of  this  canal). 

On  the  palate  of  the  Camel  is  a  small  salient  crest  that  occupies  the  anterior  two-thirds 
of  the  middle  line,  and  on  each  side  are  traces  of  transverse  furrows,  which  are  rather  large 
tubercles  a  little  elongated  from  side  to  side. 

4.  Tongue. — The  tongue  of  the  Ox  is  distinguished  hy  the  enormous  development  of  the 
muscles  composing  it.  It  is  garnished  with  conical  papillae  which  have  a  horny  sheath,  and 
their  summits,  inclining  backwards,  give  the  tongue  a  very  rough  feel.  In  this  animal  it 
serves  for  the  prehension  of  food ;  its  mobility  is  very  great,  and  it  can  be  carried  into  the 
nostrils  with  ease.  (The  body  of  the  organ  is  rounder,  and  the  point  finer,  than  in  the  Horse. 
The  calyciform  papillae  are  spread  over  the  whole  of  its  dorsal  surface ;  and  at  the  root,  on  the 
middle  line,  is  a  somewhat  deep  groove.) 

The  tongue  of  the  Sheep,  Camel,  and  Goat  is  smaller,  proportionally,  than  that  of 
Solipeds. 

That  of  the  Camel  has  an  extremely  rich  papillary  development.  On  the  borders  of  the 
upper  surface  of  the  free  portion  are  about  half  a  dozen  calyciform  papillae,  more  or  less  large, 
but  some  of  them  have  a  greater  diameter  than  Morgagni's  foramen.  On  the  posterior  half  of 
the  same  part  are  foliated  papillae,  which  are  less  numerous  and  smaller  as  they  proceed  back- 
wards. On  the  sides  are  small  perforated  prolongations  analogous  to  the  barbs  of  Wharton's 
ducts. 

5.  Soft  Palate. — It  may  be  said,  in  a  general  manner,  that  the  palatine  prolongation  is 
shorter  than  in  Solipeds.     (The  isthmus  of  the  fauces  is  wider,  however,  and  the  amygdalae, 


THE  MOUTH. 


426 


very  developed,  are  situated  in  the  two  large  depressions  formed  on  the  sides  of  the  soft  palate 
by  the  folding  of  the  mucous  membrane.) 

In  the  Camel,  however,  the  soft  palate  is  very  developed,  and  the  channel  between  the 
mouth  and  pharynx  narrow  and  long.  The  anterior  pillars  ascend  on  the  corresponding  face 
of  the  curtain,  which  has  a  pyramidal,  soft,  relaxed  appendage,  granular  on  the  surface,  very 
movable,  and  with  its  base  forwards ;  on  each  side  of  its  summit,  tliis  appendage  has  two 
prolongations  curving  outwards, aud  below  them  a  small  sinus  or  diverticulum;  on  the  borders 


Fig.  235. 


Fig.  236. 


0:^S   INCISOR   TOOTH. 

a,  Free  portion,  external  face,  outer 
border ;  a',  ibid.,  internal  face,  outer 
border ;  b,  root ;  c,  neck  ;  /,  an- 
terior border  ;  g,  g',  inner  border. 

are  racemose  glands,  which  raise  the 
mucous  membrane.  The  latter  is  of 
a  dark  colour,  like  the  cheeks  and 
palate. 

6.  Teeth.— The  teeth  of  the  Ox  are 
thirty-two  in  number,  twenty-f  ur  of 
which  are  molars,  arranged  as  in  the 
Horse,  and  eight  incisors  belonging 
to  the  lower  jaw.  The  latter  are 
replaced  in  the  upper  jaw  by  a  thick 
cartilaginous  pud,  covered  by  the 
mucous  membrane  of  the  mouth  ;  this 
pad  forms  the  gum,  and  furnishes  a 
bearing  for  the  incisors  of  the  lower 

jaw.      Sometimes,   as  in  the    Horse, 

1,  Upper  jaw,  with'aTthe  friction  surface,  and  b,  the     there  are  found  supplementary  molars 
\JL^J.Jr.f....  9    Tnwpv  i=,w.  With  a.  the  dental     which,  if  four  in  number,  will  make 

up  the  whole  to  thirty-six;    though 
they  are  never  all  present  at  one  time 
as  the  supplementary  ones  are  shed  before  the  molar  dentition  is  completed. 

The  composition  of  the  Ox's  teeth  is  the  same  as  those  of  the  Horse,  the  only  difference 
being  in  the  arrangement  of  the  several  substances.  ,.    x  i.^ 

Incisors.-The  incisors,  eight  in  number,  are  placed  en  clavier  (like  a  key-board)  at  the 
extremity  of  the  kind  of  rounded  shoulder-bone  by  which  the  maxillary  bone  terminates, 
forming  around  this  point  a  perfect  circle  when  they  have  acquired  tlieir  full  development. 

Instead  of  being  fixed  in  the  alveoli,  as  in  Solipeds,  they  possess  a  certain  degree  of  mobility, 
sometimes  mistaken  for  a  diseased  condition ;  this  is  necessary,  in  order  to  prevent  their  wounding 
the  cartilaginous  pad  of  the  upper  jaw  against  which  they  press.  They  are  divided,  accor.  ling  to 
their  position,  into  two  centrals,  tv^o  first  laterals,  two  second  laterals,  and  two  corner  mcisors. 

Each  incisor  offers  for  consideration  two  parts :  one  free,  the  other  encased— the  root,  and 
separated  by  a  very  marked  constriction-the  neck.  This  arrangement  gives  to  the  tooth  the 
form  of  a  shovel,  the  root  representing  the  handle  (Fig.  236). 


THE   TEETH    OF   THE    OX. 


external"  surface ;   2,  Lower  jaw,  with 
tables,  and  b,  the  external  face. 


426  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

The  free  portion,  flattened  above  and  below,  and  thinnest  and  widest  towards  its  anterior 
extremity,  presents  two  faces — an  inferior  or  external,  the  other  superior  or  internal ,  with 
three  borders,  an  anterior  and  two  lateral. 

The  external  face,  slightly  convex,  and  milk-white  in  colour,  is  covered  with  fine,  undulat- 
ing, longitudinal  striae,  which  disappear  with  age,  and  leave  the  surface  beautifully  polished 
(Fig.  236,  a). 

The  internal  face,  flatter  than  the  preceding,  presents  in  its  middle  a  slight  conical 
eminence,  whose  base  widens  and  is  terminated  ne.tr  the  free  extremity  of  the  tooth,  while  its 
sides  are  circumscribed  towards  each  border  by  a  well-defined  groove  (Fig.  236,  a'). 

The  two  lateral  borders  (the  internal  slightly  convex  in  its  length,  the  external  slightly 
concave  in  the  same  direction)  make  the  free  portion  appear  as  if  thrown  outwards.  The 
anterior  border  is  sharp,  and  slightly  convex  from  one  side  to  the  otlier ;  it  is  the  first  part  of 
the  tooth  destroyed  by  wear. 

The  root  is  rounded,  slightly  conical,  and  implanted  in  an  alveolus  of  the  same  form ;  in 
youth,  it  shows  at  its  extremity  an  opening  communicating  with  an  internal  cavity  analogous 
to  that  in  tlie  teeth  of  Solipeds,  and  prolonged  into  the  interior  of  the  free  portion  (Fig.  236,  b). 

In  the  virgin  tooth,  the  enamel  forms  around  the  free  portion  a  continuous  layer,  thinnest 
on  the  internal  surface,  and  extending  very  scantily  over  a  part  of  the  root. 

The  dentine  forms  the  remainder  of  the  organ,  and  the  (pulp)  cavity,  which  is  originally  a 
large  space  of  the  same  form  as  tlie  tooth,  is  filled,  as  the  animal  grows  old,  by  new  dentine, 
which,  as  in  the  Horse,  has  a  yellower  tint  than  the  primitive  ivory. 

When  the  cavity  is  completely  filled,  the  tooth  ceases  to  grow,  and  is  not  pushed  beyond 
the  alvenlu^f  during  wear,  like  the  teeth  of  the  Horse. 

The  incisor  tooth  has  scarcely  arrived  at  its  perfect  development,  before  it  begins  to  be 
worn.  Its  horizontal  position,  and  its  coming  in  contact  with  the  pad  on  the  upper  jaw, 
exposes  the  anterior  border  and  superior  face  to  friction,  and  consequent  wear  from  before  to 
behind.  The  wear,  therefore,  chiefly  aff"ects  this  upper  face,  which  really  forms  the  table  of 
the  tooth,  and  which  Girard  designates  the  avale.  When  use  has  worn  away  the  conical 
eminence  and  the  grooves  bordering  it,  the  tooth  is  levelled. 

As  wear  goes  on,  there  appears  at  first,  and  at  the  extremity  of  the  tooth,  a  yellow  band, 
which  is  the  dentine  denuded  of  its  enamel;  and  later,  in  this  dentine  a  yellower  transverse 
band  shows  itself.  With  increase  of  wear,  this  contracts,  then  widens,  and  finislies  by  forming 
a  mark  nearly  square,  and  then  round,  which  is  nothing  else  tlian  the  recently  formed  dentine 
that  fills  the  pulp  cavity  of  the  tooth.  It  is  a  veritable  dental  star,  analogous  to  that  in  the 
Horse's  tooth,  and  varying  in  form  according  to  the  incisor  in  which  it  appears. 

In  proportion  as  the  teeth  are  used,  they  seem  to  separate  from  one  another,  although  they 
still  remain  in  tlie  same  phices.  This  is  because  these  teeth,  in  youth,  only  touched  each  other 
by  their  extremities,  and  as  they  became  worn  they  decreased  in  width,  and  were  necessarily 
separated  to  an  extent  varying  with  their  degree  of  wear. 

Finally,  when  the  tooth  has  reached  its  last  stage  of  wear,  there  only  remains  the  root,  the 
upper  poi-tion  of  which,  becoming  apparent  by  the  retreat  of  the  gum,  stands  as  a  yellow 
stump— very  distant  from  those  which  form  with  it  the  remains  of  the  incisive  arch. 

The  first  incisors  (or  milk-Ueth)  of  the  Ox,  like  those  of  the  Horse,  are  all  deciduous,  and 
differ  from  those  which  replace  them  by  their  smaller  volume,  less  width,  the  transparency  of 
their  enamel,  and  their  being  mere  curved  outwanls.  Their  roots  are  much  shorter,  nnd  are 
destroyed  by  the  succeeding  teeth.  The  two  temporary  centrals  are  always  separated  l)y  a 
marked  interval,  depending  on  the  thickness  of  the  fibro-cartilage  in  the  maxillary  symphysis 
during  youth. 

Molars. — As  in  Solipeds,  the  molars  are  six  in  each  side  of  the  jaws,  but  they  are  much 
smaller,  and  form  a  much  shorter  arch.  Their  reciprocal  volume  is  far  from  being  as  uniform 
as  in  the  Horse,  but  goes  on  augmenting  from  the  first  to  the  sixth ;  find  to  such  a  degree, 
that  the  space  occupied  by  the  three  anterior  molars  is  only  about  one-half  of  that  required 
for  the  three  posterior  ones ;  the  last  molar  alone  occupies  nearly  four  times  as  much  space, 
lengthwise,  as  the  first. 

Their  wearing  surface,  constructed  on  the  same  system  as  that  of  the  Horse's  molars, 
present  eminences  a  little  more  acute. 

The  arrangement  of  their  three  constituents  is  in  principle  the  same  as  in  the  latter  animal. 

As  in  the  Horse,  the  three  front  molars  are  deciduous. 

The  teeth  of  the  Sheep  and  Goat  are,  like  those  of  the  Ox,  thirty-two  in  number,  divided 
into  eiglit  incisors  and  twenty-four  molars,  to  which  are  sometimes  added  supplementary 
molars. 

The  incisors  of  the  smaller  Ruminants  are  not  disposed  like  a  key-board,  as  in  the  Ox,  but 


THE  MOUTH.  427 

stand  up  to  form  a  grip,  resting  against  the  pad  on  the  upper  jaw  much  more  by  their  extremity 
than  by  their  inner  surface. 

They  are,  besides,  narrow,  have  scarcely  any  neck,  and  are  fixed  more  solidly  in  the  alveoli 
(Fig.  237). 

Their  external  face  is  white  and  polished,  and  is  encased  towards  the  gum  in  a  kind  of 
black  cement. 

The  internal  face  has  two  wide,  longitudinal  grooves,  separated  towards  the  middle  of  the 
table  by  a  simple  ridge,  wliich  replaces  the  conical  eminence  of  the  Ox's  incisor.  These 
grooves  are  nearly  always  lined  with  the  black  cement-like  substance. 

The  incisors  of  the  Sheep  are,  like  the  Ox's,  dititinguished  into  temporary  and  replacing 
teeth ;  the  first  are  known  from  the  others  by  their  smallness,  and  particularly  by  their 
narrowness. 

The  wear  of  the  incisors  in  the  Sheep,  from  their  position,  ought  to  take  place  nearer  the 
anterior  border  than    in  the  Ox;    the  dental   star   is   observed 
earlier,  and  always  forms  a  narrower  line  from  before  to  behind.  pjg.  237. 

The  absence  of  a  neck  in  these  teetli  is  the  reason  why  they 
never  appear  to  separate  with  wear,  as  has  been  remarked  in 
those  of  the  Ox. 

The  molars  have  tlie  greatest  resemblance,  in  their  general 
form  and  relative  proportions,  to  those  of  the  Ox. 

The  teeth  of  the  adult  Camel  are  thirty-four  in  number — 
six  incisors  in  the  lower  maxilla,  ten  molars,  and  six  teeth  re- 
sembling canines,  two  of  which  are  fixed  in  the  premaxilla.     In      incisor  teeth  of  a  sheep 
the  young  animal,  the  incisors— the  free  border  of  whicii  is  sharp  '^^^  years  old. 

as  in  the  otiier  Ruminants — are  much  inclined  on  the  maxillary  The  second  laterals  and  the 
border,  but  become  erect  as  the  creature  grows  older,  so  as  to  corner  incisors  have  not 
resemble  those  of  the  Horse.  yet  been  replaced. 

The  canines  of  the  lower  jaw  are  strong  and  pointed  ;  among 
those  of  the  upper  jaw,  the  laterals  only  are  greatly  developed,  and  some  authorities  regard 
them  as  premolars. 

Tile  proper  molar  teeth  show  the  general  arrangement  and  organization  of  the  Ox's  teeth. 
They  are  covered  by  a  dark  cementum  (Fig.  46). 

Pig  1.  Li'ps — In  this  animal  the  lips  are  widely  cleft.  The  lower  is  pointed  and  little 
developed;  tlie  upper  is  confounded  with  the  snout,  which  will  be  described  with  the  nostrils. 
(The  upper  lip  has  little  mobility.) 

2.  Cheeks. — Tliese  are  small  and  thin,  and  the  mucous  membrane  smooth. 

3.  Palate. — Narrow  and  elongated,  it  is  disposed  as  in  the  Horse.  In  front  is  seen  the 
orifices  of  Jacobson's  canals.  (The  transverse  ridges  are  twenty  to  twenty-two  in  number,  the 
anterior  being  larger  than  the  posterior,  and  their  free  borders  are  united.) 

4.  Tongue,  f^.  Soft  Palate. — These  two  organs  are  the  same  as  in  the  smaller  Ruminants, 
except  that  the  filiform  papillae  are  perhaps  less  developed.  (The  isthmus  of  the  fauces  is 
circular,  and  the  posterior  pillars  are  confounded  with  the  mucous  membrane  at  the  upper  part 
of  the  oesophagu-^.  Its  anterior  surface  has  several  conical  eminences  in  the  middle,  and  the 
amygdalae  iire  little  rounded  elevati(ms.) 

6  Teeth. — The  Pig  has  forty-four  teeth,  which  are  divided  into  twelve  incisors,  four 
canines,  and  twenty-eight  molars  (Fig.  238). 

The  incisors,  six  in  each  jaw,  exhibit  very  remarkable  differences  between  each  other. 
The  centrals  and  laterals  of  the  upper  jaw  offer,  by  their  form  and  the  cavity  they  show  on 
their  table,  some  analogy  to  those  of  the  Horse.  In  the  lower  jaw,  these  teeth  are  straight, 
directed  forwards,  and  bear  some  resemblance  to  the  incisors  of  rodent  animals.  The  corner 
incisors  of  botli  jaws  are  isolated  between  the  lateral  and  canine  teeth,  and  are  not  nearly  so 
voluminous  as  the  other  incisors. 

The  tusks  are  very  developed,  particularly  in  the  male,  and  cross  each  other  during  the 
life  of  the  animal ;  ihey  project  from  the  mouth,  and  form  a  very  dangerous  weapon  in  the 
wild  boar.     The  primary  canines  are  deciduous,  like  the  incisors. 

The  molars,  seven  in  each  row,  increase  in  volume  from  the  first  to  the  last,  which  Is  very 
strong.  Their  tables  hold  a  middle  place,  with  regard  to  arrangement,  between  that  of  the 
Carnivora  and  Herbivora. 

Carnivora.  1.  Lips.— The  Carnivora,  like  the  Pig,  do  not  use  their  lips  to  grasp  their 
food,  and  these  are  therefore  thin,  though  movable.  The  upper  lip  of  the  Dog  has  a  groove 
in  the  middle  line,  and  it  covers  the  lower  lip  more  or  less  at  the  sides  according  to  the  breed. 
The  lower  lip  is  always  scalloped  on  its  free  border  near  the  commissures,  which  are  very  high. 


428  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

In  the  Cat,  the  hairy  tentaculse  are  collected  on  the  upper  lip  into  two  long  lateral  tufts  the 
moustaches ;  they  are  very  sensitive  and  movable. 

2.  Cheeks.  3.  Palate. — The  cheeks  resemble  those  of  the  Pig;  the  palate  that  of  small 
Rumiuants.  The  mucous  membrane  is  often  stained  by  patches  of  pigment,  especially  on  the 
palate.  (The  latter  is  frequently  quite  black.  The  number  of  ridges  on  the  palate  varies  from 
seven  to  nine.     Jacobsou's  canal  opens  behind  the  incisors.) 

4.  Tongue. — This  is  thin  and  very  movable.  The  papillae  on  its  upper  face  vary  somewhat 
in  the  Cat  and  Dog.  In  the  Cat,  the  filiform  papillae  on  the  anterior  two-thirds  of  the  tongue  are 
covered  by  a  very  strong  horny  sheath,  the  point  of  which  is  directed  backwards.  In  the  Dog 
these  papillfe  are  less  developed,  and  there  are  observed,  more  particularly,  a  number  of  oomposite 
filiform  papillae,  the  divisions  of  which  are  very  flexible.  There  also  are  found  regularly  disposed 
among  these,  white  shining  epithelial  particles  which  correspond  to  small  fungiform  papdlsB. 

Fig.  238. 


THE   TEETH   OF   THE    PIG. 

1,  Upper  teeth,  table  surface ;  2,  lower  teeth,  table  surface ;  3,  lateral  view  of  the  jaws. 


At  the  base  of  the  tongue  of  Carnivora,  and  within  the  anterior  pillars  of  the  soft  palate, 
are  two  elongated  bodies  with  rounded  extremities  and  a  nodulated  slippery  surface  ;  these  are 
true  amygdalse,  formed  by  an  agglomeration  of  closed  follicles. 

5.  Soft  Palate. — In  the  Dog  and  Cat,  the  soft  palate  is  very  short,  and  the  istlimus  of  the 
fauces  wide.  Consequently,  these  creatures  breathe  easily  by  the  mouth,  and  expel  matters 
by  it  from  the  stomach  during  vomiting.  At  its  free  border,  the  soft  palate  shows  a  small  pro- 
longation, something  like  the  uvula. 

6.  Teeth. — The  teeth  of  the  Dog  are  forty-two  in  number :  twelve  incisors,  four  canines, 
and  twenty-six  molars. 

The  incisors,  six  in  each  side  of  the  jaws,  are  more  developed  in  the  superior  than  in  the 
inferior  maxilla,  and  are  divided,  as  in  the  Horse,  into  centrals,  lateials,  and  comer 
incisors ;  the  last  are  much  stronger  than  the  preceding,  and  these  again  stronger  than  the 
pincers. 


THE  MOUTH. 


429 


Their  free  part  presents,  in  the  virgin  tootb,  three  tubercles :  a  middle,  which  is  the 
Btronc-est  and  two  lateral;  these,  together,  are  not  unlike  a  trefoil  or  the  upper  part  of  a  ^ewr- 
de-iis"  especially  those  in  the  upper  jaw.  On  the  internal  face  is  remarked  a  table  or  slope, 
somewhat  resembling  that  of  the  Ox  and  Sheep,  and  separated  from  the  root  by  a  very  distinct 
border,  the  extremities  of  which  mark  the  lateral  lobes.     This  table  is  of  no  advantage  in 

*^^  The°root,  very  developed,  flattened  oa  both  sides,  and  separated  from  the  free  portion  by 


Fig.  239. 


GENERAL   AND   LATERAL   VIEW   OF   THE   DOG  S   TEETH. 


a  well-defined  neck,  is  solidly  encased  in  a  deep  alveolus.  Its  internal  cavity  is  very  promptly 
obliterated. 

When  the  tooth  is  submitted  to  wear,  the  middle  lobe  is  the  first  to  disappear ;  so  that  it  no 
longer  resembles  a  trefoil  (Fig.  240). 

The  temporary  incisors  are  much  smaller  and  more  pointed  than  the  permanent  ones ;  yet, 
like  them,  they  show  lateral  lobes.  At  the  period  of  their  eruption  these  teeth  are  somewhat 
wide  apart. 

The  fangs,  or  canine  teeth,  two  in  each  jaw,  are  very  strong,  elongated  organs,  conical  in 
form,  curved  backwards  and  outwards,  and  placed  immediately  after  the  incisors. 


Fig.  240. 


ANTERIOR   VIEW   OF   THE   INCISORS   AND   CANINE 
TEETH   OF   A   YEAR-OLD   DOG. 


LATERAL   AND    GENERAL   VIEW   OF    THI 
cat's  TEETH. 


The  upper  fangs  are  the  thickest,  and  have  a  small  space  between  them  and  the  corner 
incisors,  in  which  the  inferior  canines  are  lodged. 

These  teeth  are  deciduous,  like  the  incisors,  and  are  distinguished  from  the  replacing  ones 
by  being  thinner  and  more  elongated. 
3D 


430 


TEE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


They  are  worn  more  or  less  quickly,  according  to  tlie  kind  of  food  the  animal  obtains,  and 
are  sometimes  broken  in  fighting. 

The  molars  are  distributed  in  the  two  jaws,  twelve  being  fixed  in  the  upper  and  fourteen 
in  the  lower. '  Nearly  all  of  them  are  terminated  by  somewhat  acute  lobes,  proper  for  tearing 
animal  food.  The  strongest  in  eacii  jaw  is,  for  the  upper,  the  first  back-molar  or  fourth  in  the 
row,  and  iu  the  lower,  the  fifth.     All  in  front  of  these  are  deciduous. 

After  iheir  complete  eruption  from  the  alveolar  cavities,  the  Dog's  teeth  are  no  longer 

pushed  outwards.     They  are  remarkable 


Fig.  242. 


for  their  brilliant  whiteness,  which  they 
owe  to  the  absence  of  cement  on  their 
covering  of  enamel. 

The  Cat  has  thirty  teeth  .  twelve  in- 
cisors, four  tusks,  and  fourteen  molars, 
eight  of  which  are  in  the  upper,  and  six 
iu  the  lower  jaw. 

All  these  teeth  are  constructed  on  the 
same  type  as  those  of  the  Dog.  The 
canines  are  deeply  striated  on  their  ex- 
ternal surface,  instead  of  being  smooth. 

Rabbit. — It  may  be  noted  that  in  the 

rabbit  there  are  two  incisors  in  the  lower 

jaw,  and  four  in  the  upper,  two  of  which 

are    placed    behind    the    principal    two. 

I    I  \\:^?^s\  #  V       There  are  ten  molars  in  the  lower,  and 

\i  \    \\      jl  twelve  iu  the  upper,  which  are,  in  prin- 

'l  \  l\  ciple,  as  in  the  horse. 

H  \  W     /\  (The  importance  of  a  correct  know- 

f  \         (\  I    I     I        le<ige  of  the  period  of  eruption,  shedding, 

*        "^  '         '        replacing,  and  general  wear  of  the  teeth 

of  the  domesticated  animals,  as  a  guide 

to  their  age,  induces  me  to  give  the  table 

on  p.  431  (from  Leyh),  as  indicating  at  a 

glance  the  age  at  which  the  teeth  appear, 

are  shed,  and  replaced  in  the  diflferent 

creatures. 

Baumeister    divides    the    successive 
evolutions  in  the   wear  of  the  tables  of 
the  horse's  incisor  teeth  into  four  periods 
— from  six   years   to   extreme   old   age. 
The  first,  the   transversely  oval  period, 
extends  from   six  to  twelve   years;   the 
round,  from   twelve  to    eighteen  years ; 
the  triangular,  from  eighteen  to  twenty- 
four  years,  and  tlie  antero-postHrior  oval  or  triangular,  from  twenty-four  years  and  upwards. 
Girard  an.l  other  Frencii  authorities  shorten  these  periods  somewhat.     Tlie  triangular  period, 
for  instance,  only  lasts  from  fourteen  to  seventeen  years.) 

Comparison  of  the  Mouth  op  Man  with  that  of  Animals. 
The  shortness  of  Man's  face  influences  the  shape  of  the  mouth ;  therefore  it  is  proportionately 
shorter  and  wider  than  in  the  domesticated  Mammals. 

1.  Lips. — The  lips  have  a  thick,  free,  everted  border.  They  are  lined  by  a  rosy  mucous 
membrane,  which  is  insensibly  continued  inwanls  by  the  buccal  membrane.  The  upper  lip 
is  limited  by  the  nose  and  the  naso-labial  furrow ;  the  lower  is  limited  by  the  mentodabial 
groove.  The  first  has  in  its  middle  the  subnasal  furrow.  Their  structure  is  analogous  to  those 
of  animals. 

2.  C7/efi&«.— The  cheeks  are  limited  by  the  inferior  border  of  the  maxilla,  the  root  of  the 
ear,  the  prominence  of  the  chin,  and  the  naso-labial  furrow.  Between  the  skin  and  the  mucous 
membrane,  there  is  found — as  in  brutes— a  glandular  layer  and  muscles,  chiefly  the  buccinator. 
An  adipose  ball  is  always  found  near  the  anterior  border  of  the  masseter. 


dentition  of  the  rabbit  :  THE  TEETH  SEEN  FROM 
THEIR  TABLES. 


Upper  jaw ;  b,  lower  jaw. 


'  Toussaint  has  observed  that,  in  breeds  with  short  faces,  the  molars  decrease  in  number, 
or  are  placed  transversely,  so  as  to  find  room  in  the  maxillae. 


THE  MOUTH. 


431 


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432 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


3.  Palate.— li  does  not  possess  a  vascular  membrane,  as  in  the  Horse,  and  its  mucous 
membrane  shows  a  longitudinal  and  transverse  furrow  in  its  anterior  two-thirds.  It  is  pal© 
and  resisting. 

4.  Tonj/Me.— This  is  thick,  short,  and  broad ;  its  base  is  almost  vertical,  and  in  the  middle 
is  a  perpendicular,  fibrous,  and  semilunar  lamina — the  lingual  septum — which  gives  insertion  to 
muscular  fibres. 

Authropotoruists  distinguish  intrinsic  and  extrinsic  muscles.  The  first  are :  the  lingualis 
superior  and  inferior,  transversus,  and  longitudinalis.  The  second  are,  as  in  Solipeds,  the 
stylo-glissus,  genio-glossus,  hyo-glossus,  and  pharyngo-glossus.  There  is  also  described  a 
palato-glossus,  which  partly  belongs  to  the  soft  palate. 

The  mucous  membrane  shows  the  ditierent  characters  recognized  in  that  of  animals.     That 

Fig.  243. 


MEDIAN    ANTERO-POSTERIOR   SECTION   OF   THE    HUMAN    FACE. 

a,  Septum  of  nose,  with  section  of  hard  palate  below  it ;  6,  tongue ;  c,  section  of  soft  palate ;  d,  d, 
lips;  M,  uvula;  r,  anterior  arch,  or  pillar  of  fauces;  i,  posterior  arch;  t,  tonsil;  p,  pharynx; 
h,  hyoid  bone;  k,  thyroid  cartilage;  n,  cricoid  cartilage;  s,  epiglottis;  v,  glottis.  1,  Posterior 
opening  of  nares;  3,  isthmus  faucium ;  4,  superior  opening  of  larynx  ;  5,  passages  into  cesophagus  ; 
6,  orifice  of  right  Eustachian  tube. 


of  the  dorsal  face  is  divided  into  two  portions  by  two  A-shaped  rows  of  papillae,  the  summit  ot 
which  abuts  on  the  deep  mucous  follicle  named  the  foramen  csecum.  The  posterior  portion  presents 
depressions  which  correspond  to  the  closed  follicles,  and  the  fungiform  and  calyciform  papillae  ; 
the  anterior  portion  has  a  villous  aspect,  due  to  the  great  number  of  filiform  papillae  cowringit. 
5.  Soft  Palate. — In  Man,  the  soft  palate  is  short  and  divided  into  two  portions :  an  anterior, 
horizontal,  attached  to  the  base  of  the  tongue  by  the  anterior  pillars  of  the  curtain  ;  a  posterior, 
movable  and  oblique,  having  a  free  portion,  the  uvula,  and  fixed  to  the  lateral  walls  of  the 
pharynx  by  the  posterior  pillars.  Tlie  amygdalx,  or  mass  of  closed  follicles,  are  lodged  in  the 
triangular  space  between  the  anterior  and  posterior  pillars.  The  fibrous  structure  is  not 
present,  unless  the  small  expansion  of  the  external  tensor  of  the  palate  represents  it.  The 
muscles  are  the  same  as  in  animals,  and,  in  addition,  there  are  described  two  palato-glossal 
muscles,  included  between  the  mucous  folds  tliat  form  the  anterior  pillars.  The  palato- 
pharyngeus  extends  to  the  posterior  nasal  spine.  The  isthmus  of  the  fauces  is  wider  than  in 
the  Carnivora. 


THE  SALIVARY  GLANDS.  433 

6.  Teeth. — The  teeth  are  thirty-two  in  number,  sixteen  in  each  jaw.  They  are  distributed 
in  the  foUowiug  manner:  four  incisors,  two  canines,  two  small  molars  (bicuspidati),  and  three 
large  molars  (multi-cuspidati). 

The  incisors,  when  viewed  in  profile  or  longitudinal  section,  have  a  wedge-shape»  and  their 
free  border  is  more  or  less  sharp.  The  canines  are  irregularly  conical;  the  molars  have  a 
multiple  fang,  and  the  crown  is  studded  with  a  variable  number  of  tubercles :  two  on  each 
small  molar  and  four  on  the  large.     In  youth,  there  are  only  twenty  teeth,  ten  in  each  jaw. 

The  Salivary  Glands. 

The  salivary  glands  are  secretory  organs  annexed  to  the  buccal  cavity,  into 
which  they  pour  saliva — a  recrementitious  fluid  that  softens  the  food,  favours  its 
mastication  and  deglutition,  and  has  a  chemical  action  upon  it  after  its  arrival 
in  the  abdominal  portion  of  the  digestive  tube. 

Though  very  diversified  in  form,  yet  they  present  in  their  structure  such 
common  characters,  that,  to  obviate  recurrence  to  their  organization  when 
speaking  of  each  gland,  we  will  describe  them  here. 

These  glands  are  composed  of  a  greyish-red  or  yellow  spongy  tissue,  which  is 
divided  into  small,  rounded,  or  polyhedral  masses,  called  salivary  lobules.  These 
extend  in  a  layer  beneath  the  adherent  face  of  the  mucous  membrane,  and 
remain  isolated  from  each  other,  or  are  agglomerated  in  a  body  to  form  a  single 
gland.  In  the  latter  case,  they  are  united  by  close  connective  tissue,  which 
covers  them  as  a  very  thin  enveloping  membrane,  and  throws  into  the  lobular 
interstices  lamellar  prolongations. 

In  studying  the  organization  of  one  of  these  lobules,  it  will  be  observed  that 
it  is  made  up  of  many  very  small  secondary  lobules,  or  acini,  which  are  themselves 
due  to  the  agglomeration  of  minute  elementary  vesicles  or  follicles,  the  average 
diameter  of  which  is  from  3-5-0^  to  i^V^  of  an  inch;  these  open  into  the  little 
canal  belonging  to  each  of  the  secondary  lobules,  and  which  again  joins  those 
of  the  other  acini  of  the  primary  lobule,  to  form  a  single  duct. 

The  minute  elementary  vesicles  or  follicles — the  ghmdidar  nds-de-sac  (or 
ultimate  follicles) — are  more  or  less  completely  filled  with  delicate  cells,  transparent 
or  slightly  granular.  They  have  for  wall  a  thin  amorphous  membrane  {membrana 
propria),  against  which,  towards  the  bottom  of  the  caini,  and  beneath  the  glandular 
epithelium,  are  cells  having  half-moon-like  forms,  a  group  of  which  constitutes  a 
mass  called  the  crescent  (or  lanula)  of  Gianuzzi  (or  marginal  cells) — example,  the 
submaxillary  gland.  (They  are  closely  surrounded  by  a  plexus  of  capillary 
blood-vessels.) 

"When  the  salivary  lobules  remain  isolated,  this  canal — which  is  designated  as 
excretory,  because  it  carries  from  the  lobule  the  saUva  secreted  within  the 
elementary  follicles — opens  directly  into  the  mouth.  But  when,  on  the  contrary, 
they  all  unite  and  form  a  single  gland,  their  excretory  canals  finally  converge 
into  one  or  more  principal  ducts,  the  termination  of  which,  in  every  case,  takes 
place  in  the  same  manner — by  opening  into  the  mouth  from  the  summit  of  a 
more  or  less  salient  tubercle  ;  this  arrangement  renders  the  introduction  of 
particles  of  food  into  these  excretory  orifices  somewhat  difficult.  The  fibrous 
and  elastic  walls  of  these  ducts  are  lined  by  cylindrical  epithelium. 

To  the  fundamental  tissue  just  described  must  be  added  arteries,  veins,  and 
lymphatics,  which  convey  the  materials  of  secretion  and  nutrition  ;  as  well  as 
the  yierves  which  regulate  the  secretory  and  nutritive  acts  (excito-secretory  and 
vaso-motor  nerves).  According  to  many  histologists,  the  excito-secretory  nerves 
remain  between  the  acini,  but  others  (Pfliiger,  Gianuzzi,  Paladino)  assert  that 


434  TEE  DIGESTIVE  APPABATUS  IN  MAMMALIA. 

they  traverse  the  Avails  of  the  nds-de-sac  and  come  into  direct  relations  with  the 
gland-cells. 

The  most  voluminous  of  these  glands— or  those  which  comprise  a  very  great 
number  of  agglomerated  lobules— will  be  first  noticed.  They  are  the  parotid, 
maxillarij,  subUmjucd,  and  molar  glands,  which  are  all  pairs,  and  are  placed  in 
proximity  to  the  mouth,  when  they  do  not  lie  immediately  beneath  the  adherent 
face  of  its  mucous  membrane.  Secondly,  the  less  important  glands— those  which 
are  spread  in  layers  under  that  membrane,  and  including  the  labial,  lingual,  and 
staphyhne  glands — will  be  examined. 

1.  Parotid  Gland  (Figs.  168,  8  ;  247,  8). 

Preparation.-T\xiB  glaud,  with  its  excretory  canal,  is  seen  after  the  removal  of  the  cervico- 
facial panniculus  and  parotido-aurieularis  muscle.  By  injecting  Steno's  duct  and  the  facial 
artery  and  vein,  the  relations  of  these  three  vessels  will  be  better  seen  at  the  maxillary  fissure. 

The  parotid  gland  is  situated  in  the  space  included  between  the  posterior 
border  of  the  inferior  maxilla  and  the  transverse  process  of  the  atlas.     It  is 

Fig.  244. 


CAPILLARY  NETWORK  AROUND  THE   FOLLICLES 
OF   THE    PAROTID   GLAND. 
LOBULE    OF    PAROTID   GLAND,    INJECTED  WITH 
MERCURY,    AND   MAGNIFIED    50    DIAMETERS. 

elongated  from  above  to  below,  flattened  on  both  sides,  and  divided  into  two 
faces,  two  borders,  and  two  extremities. 

The  external  face,  nearly  plane,  is  hollowed  in  its  inferior  part  into  a 
longitudinal  channel,  which  is  sometimes  transformed  into  a  complete  canal,  and 
lodges  the  jugular  vein  after  it  has  traversed  the  glaud  from  below  to  its 
superficies.  This  external  face  responds  to  the  parotido-aurieularis  muscle,  the 
panniculus,  the  atloidean  loop,  a  cervical  ramification  of  the  facial  nerve,  and 
the  posterior  auricular  vein.  The  internal  face  is  very  uneven  and  moulded  on 
the  subjacent  parts.  It  covers  the  guttural  pouch,  the  mastoid  insertion  of  the 
obliquus  capitis  superior,  levator  humeri,  stylo-hyoideus,  the  tuberosity  on  the 
posterior  border  of  the  os  hyoideus,  the  digastricus,  the  tendon  of  the  sterno- 
maxillaris,  and  the  submaxillary  gland,  which  is  separated  from  it  by  the  thin 
cellulo-aponeurotic  layer  uniting  the  latter  muscle  to  the  levator  humeri  ;  also  to 
the  external  carotid  artery  and  its  two  terminal  branches,  the  posterior  auricularis, 
the  muscles  of  the  jaw,  and,  lastly,  the  facial  nerve,  which  often  passes 
through  the  substance  of  the  gland. 

The  anterior  border  of  the  gland  is  intimately  united  to  the  posterior  border 
of  the  maxilla  ;  it  is  related  to  the  temporo-maxillary  articulation,  the  sub- 
zygomatic  vessels  and  nerves,  and  the  maxillo-muscular  vessels.     The  posterior 


THE  SALIVARY  GLANDS. 


435 


border  is  thicker  than  the  preceding,  and  is  separated  from  the  transverse  process 
of  the  atlas  by  the  terminal  aponeurosis  of  the  levator  humeri,  to  which  it  is 
only  feebly  adherent :  it  can  also  be  easily  separated  from  it,  in  order  to  raise 
the  parotid  and  pass  through  the  stylo-hyoideus  muscle,  in  the  operation  of 
hyo-vertebrotomy. 

The  superior  extremity  is  bifurcated,  and  embraces  the  base  of  the  concha  of 
the  ear.  The  inferior  extremity  is  comprised  in  the  angle  formed  by  the  union 
of  the  jugular  and  glosso-facial  veins. 

Vessels  mid  nerves  of  the  parotid  gland. — This  gland  receives  its  blood  by  a 
multitude  of  arterial  branches  from  the  large  vessels  it  covers.  Its  nerves  are 
very  numerous,  and  are  derived  from  the  facial  and  inferior  maxillary  nerves. 
The  excito-secretory  nerve,  says  Moussu,  is  isolable  on  leaving  the  Gasserian 
ganglion  ;  it  is  composed  of  four  or  five  filaments  which  lie  alongside  the  sub- 
zygomatic  or  inferior  maxillary  nerve  for  about  a  centimetre,  then  on  the  surface 

Fig.  246. 


MODES   OF   TERMINATION   OF   THE   NERVES   IN   THE   SALIVARY   GLANDS. 

1,  2,  Branching  of  the  nerves  between  the  salivary  cells  ;  3,  termination  of  the  nerve  in  the  nucleus ; 
4,  union  of  a  ganglion  cell  with  a  salivary  cell ;  5,  varicose  nerve-fibres  entering  the  cylindrical 
cells  of  the  excretory  ducts. 


of  the  guttural  pouch  until  it  reaches  the  posterior  border  of  the  inferior  maxilla 
and  the  internal  maxillary  vein,  when  it  enters  the  gland.    It  is  diificult  to  discover. 

Small  lymphatic  glands  are  believed  to  have  been  seen  in  the  substance  of 
the  parotid. 

Excretory  canal. — The  parotid  gland  is  provided  with  a  single  excretory 
canal — the  duct  of  Steno  or  Stenon,  so  named  from  the  anatomist  who  gave  the 
first  good  description  of  it.  It  is  detached  from  the  anterior  border  of  the 
gland,  near  its  inferior  extremity,  where  the  eye  may  readily  follow  it  between 
the  lobules  to  the  three  or  four  principal  branches  from  which  it  originates  (Fig. 
247).  At  first  in  contact  with  the  terminal  tendon  of  the  sterno-maxillaris, 
it  afterwards  turns  round  the  posterior  border  of  the  digastric  muscle  (stylo- 
maxillaris  portion),  advances  into  the  submaxillary  space,  creeps  over  the 
pterygoid  muscle,  beneath  the  glosso-facial  vein,  and  arrives  at  the  maxillary 
fissure,  into  which  it  enters  with  the  aforesaid  vein  and  corresponding  artery, 
but  behind  both.     It  then  ascends  externally  along  the  anterior  border  of  the 


TEE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


masseter  muscle,  to  the  level  of  the  inferior  molars,  when  it  passes  beneath  its 
two  satellite  vessels,  obliquely  crosses  their  direction,  and  pierces  the  cheek 
towards  the  third  upper  molar  tooth,  opening  into  the  mouth  by  a  large  tubercle. 
The  parotid  duct  is  composed  of  two  membranes  :  the  internal,  mucous,  with 
cylindrical  epithelium  ;  and  the  external,  made  up  of  connective  tissue,  and 
circular  and  longitudinal  elastic  fibres. 

2,  Maxillary  or  Submaxillary  Gland  (Figs.  247,  248). 

Preparation. — To  expose  this  gland,  as  well  as  the  sublingual,  divide  the  inferior  maxilla, 
as  in  preparing  the  muscles  of  the  tongue  for  dissection  (see  p.  400). 

This  gland,  smaller  than  the  preceding,  is  situated  in  the  submaxillary  space, 

on  the  side  of  the  larynx,  and 
*'^S'  '^^'^-  within  the  parotid  gland. 

It  is  long  and  naiTow,  flattened 
on  both  sides,  and  describes  a 
slight  curve  with  the  concavity 
turned  upwards :  a  form  which 
allows  it  to  be  studied,  with  regard 
to  relations,  on  two  faces,  two 
borders,  and  two  extremities. 

By  its  external  face,  it  responds 
to  the  internal  pterygoid  and  digas- 
tricus  muscles,  the  sterno-maxil- 
laris  tendon,  and  the  cellulo-apo- 
neurotic  layer  separating  it  from 
the  parotid.  Its  internal  face,  ap- 
plied to  the  side  of  the  larynx, 
responds,  superiorly,  to  the  guttural 
pouch,  to  the  carotid  artery,  and 
to  the  nerves  which  accompany 
that  vessel  in  the  upper  part  of  the 
neck. 

The  superior  border,  thin  and 
concave,  is  margined  by  the  middle 
part  of  the  digastricus.  The  in- 
ferior, thick  and  concave,  is  in  con- 
tact with  the  glosso-facial  vein. 

The  posterior  extremity  is  main- 
tained beneath  the  transverse  pro- 
cess of  the  atlas,  by  an  extremely 
loose  and  abundant  connective 
tissue  ;  the  anterior  is  insinuated 
between  the  internal  pterygoid  and 
the  thyro-hyoideus  muscle. 

Vessels  and  n&rves. — The  blood 

is   distributed    to    the   maxillary 

gland  by  various  small  innominate 

arteries,  like  those  of  the  parotid  gland,  and  which  are  most  frequently  derived 

from  the  external  carotid  and  the  glosso-facial.     The  nerves  are  principally 

furnished  by  the  carotid  plexus. 


INFERIOR    ASPECT   OF    HEAD    AND    NECK. 

1,  Inferior  border  of  lower  jaw  ;  2,  genio-hyoideus ;  3, 
mylo-hyoideus ;  4,  submaxillary  artery ;  5,  ditto 
vein  ;  6,  parotid  duct ;  7,  sterno-maxiilaris  tendon  ; 
8,  parotid  gland ;  9,  sterno-maxiilaris  muscle ;  10, 
11,  12,  submaxillary  glands;  13,  sterno-thyro- 
hyoideus  and  subscapulo-hyoideus  muscles;  14, 
thyroid  gland;   15,  ptery_e:oideus  internus. 


THE  SALIVARY  GLANDS. 


437 


Excretory/  canal. — Wharton'' s  duct,  as  it  is  termed,  is  long  and  narrow  ;  has 
very  attenuated  walls,  and  exists  for  nearly  the  whole  length  of  the  superior 
border  of  the  gland  (sometimes  on  its  internal  face),  where  it  receives  the 
ramifications  from  various  lobules.  At  the  anterior  extremity  of  the  organ  it  is 
free,  and  passes  forward  between  the  mylo-hyoideus  and  hyo-glossus  muscles. 
After  crossing,  outwardly,  the  glosso-facial  artery  and  great  hypoglossal  nerve, 
and,  inwardly,  the  tendon  of  the  digastricus  and  the  lingual  nerve,  it  passes 
between  the  great  hyo-glossus  muscle  and  the  sublingual  gland,  lying  closely  to 
the  inner  side  of  the  latter ;  thus  it  extends  parallel  to  the  lateral  groove  (or 
channel)  of  the  lingual  canal  on  the  floor  of  the  mouth.     It  finally  arrives  near 

Fig.  248. 


MAXILLARY   AND   SUBLINGUAL  GLANDS. 

R,  Maxillary  gland ;  S,  Wharton's  duct ;  T,  sublingual  gland. 


the  frfenum  of  the  tongue,  but  underneath  the  buccal  membrane,  and  opens  into 
the  mouth  by  a  small,  but  very  salient,  floating  tubercle,  situated  a  httle  in 
advance  of  the  frsenum,  and  vulgarly  named  the  iarb  {harhillon). 

The  structure  of  Wharton's  duct  is  identical  with  that  of   Steno,  but  its 
external  tunic  is  extremely  thin,  and  has  not  any  circular  elastic  fibres. 

3.  Sublingual  Gland  (Fig.  248). 

This  is  less  in  volume  than  the  preceding,  and  is  situated  under  the  tongue, 
in  the  submaxillary  space. 

Elongated  from  before  to  behind,  and  very  flat  laterally,  it  has,  like  the 


438  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

gubmaxillary  gland,  two  faces,  two  borders,  and  two  extremities,  the  relations 
of  which  we  will  briefly  indicate. 

The  external  face  is  covered  by  the  mylo-hyoideus  muscle  :  the  internal 
responds  to  Wharton's  duct  and  the  genio-glossus  and  great  hyo-glossus  muscles. 
The  upper  border  projects  beneath  the  mucous  membrane  on  the  floor  of  the 
mouth,  where  it  forms  the  sublingual  ridge;  the  inferior,  thin  and  sharp,  is 
comprised  between  the  mylo-hyoideus  and  the  genio-glossus  muscles.  The  tivo 
extremities  are  thin  and  tapering  ;  the  posterior  contains  a  branch  of  the  lingual 
nerve  ;  the  anterior  extends  to  the  bottom  of  the  angle  formed  by  the  union  of 
the  two  branches  of  the  inferior  maxilla. 

Vessels  and  nerves. — This  gland  possesses  a  special,  but  small  artery — the 
suUiyigual.  Its  nerves  come  from  the  lingual  nerve,  and  even  from  the  carotid 
plexus. 

Excretory  canals. — These  number  fifteen  or  twenty,  and  are  named  the  ducts 
of  Rivinius.  Flexuous  and  very  slender,  they  are  detached  from  the  superior 
border  or  internal  face  of  the  gland,  ascend  perpendicularly,  and  open  into  the 
mouth  on  the  sublingual  crest  or  ridge,  by  a  linear  series  of  small  orifices  pierced, 
as  usual,  in  the  centre  of  a  tubercle. 

4.  Molar  Glands. 

These  are  so  named,  because  they  are  disposed  parallel  to  the  molar  arches. 
There  are  two  on  each  side. 

The  superior  molar  gland — the  most  considerable — appears  as  a  narrow  line  of 
salivary  lobules  placed  outside,  and  along  the  upper  border  of,  the  buccinator 
muscle.  In  its  posterior  part,  where  it  is  concealed  beneath  the  masseter  muscle, 
this  gland  is  thicker  and  more  compact  than  in  front,  where  the  few  lobules 
which  compose  it  scarcely  come  in  contact  with  each  other. 

The  inferior  molar  gland— less,  lobulated  and  voluminous,  and  not  so  wide  as 
the  preceding — is  placed  at  the  inferior  border  of  the  buccinator,  immediately 
beneath  the  mucous  membrane  of  the  mouth,  and  near  the  point  where  it  is 
reflected  from  the  side  of  the  cheek  on  to  the  inferior  maxilla.  It  is  bordered, 
for  the  whole  of  its  extent,  by  the  buccal  nerve. 

Both  glands  pour  their  secretion  into  the  mouth  by  numerous  salient  orifices, 
which  can  be  seen  arranged  in  line  on  the  buccal  membrane,  parallel  to  each 
molar  arch. 

It  may  be  remarked  that  these  glands  establish  a  transition  between  the 
preceding  and  those  yet  to  be  mentioned.  Their  lobules  are  far  from  being  so 
compact  as  the  parotid  or  sublingual  lobules  ;  and  they  tend  to  separate  from 
each  other,  to  become  more  independent.  Therefore  it  is  that  many  writers 
regard  them  as  distinct,  and  describe  them  as  superior  and  inferior  molar  glands. 

5.  Labial,  Lingual,  and  Staphyline  Glands. 

Tte  lobules  composing  these  glands  are  spread  in  layers,  more  or  less  thick, 
on  the  inner  face  of  the  mucous  membrane,  instead  of  being  agglomerated  in 
masses,  as  in  the  previous  glands.  Sometimes  they  are  scattered,  in  consequence 
of  their  small  number.  In  general,  the  excretory  duct  of  each  glandule  opens 
independently  into  the  mouth,  without  communicating  with  those  of  the  neigh- 
bouring lobules. 

Labial  Glandules. — These  are  more  abundant  in  the  upper  than  in  the  lower 


THE  SALIVARY  GLANDS.  439 

lip,  and  pass  beyond  the  commissures,  to  be  spread  for  a  short  distance  over  the 
inner  aspect  of  the  cheeks.  It  is  easy,  in  the  Hving  Horse,  after  turning  up  the 
lip  and  carefully  wiping  it,  to  see  the  salivary  fluid  secreted  by  these  small  organs 
escape  from  their  excretory  ducts. 

Lingual  Glandulce. — They  form  a  layer  under  the  mucous  membrane  at  the 
base  of  the  tongue,  and  adhere  very  closely  to  the  fibres  of  the  small  hyo-glossus 
muscle,  and,  laterally,  are  continuous  with  the  layer  which  covers  the  external 
face  of  the  amygdaloid  mucous  membrane.  They  are  also  found  on  the  side  of 
the  tongue,  above  the  superior  border  of  the  great  hyo-glossus  muscle  ;  though 
these  are  few  and  scattered,  and  look  as  if  embedded  in  the  substance  of  that 
muscle. 

Staphyline  Glandulce. — The  thick  layer  these  form  under  the  anterior  mucous 
covering  of  the  soft  palate,  has  been  described  with  that  organ.  We  have  only 
to  observe  here,  that  it  is  continuous,  laterally,  with  the  glands  at  the  base  of  the 
tongue,  through  the  medium  of  the  glandulce  of  the  amygdaloid  cavity  ;  and  in 
such  a  manner,  that  the  part  of  the  mouth  inmiediately  in  front  of  the  isthmus 
of  the  fauces,  and  which  might  be  justly  considered  as  the  isthmus  itself,  is 
enveloped  in  a  complete  glandular  zone.  In  the  dead  body,  we  always  find  in 
this  compartment  a  variable  quantity  of  viscid  fluid,  which  is  certainly  secreted 
in  this  zone.  It  is  here,  then,  that  the  alimentary  bolus  is  enveloped  in  the 
glutinous  matter  intended  to  favour  its  passage  in  the  pharynx  and  oesophagus  ; 
and  it  is  worthy  of  notice  that  the  constricted  canal  in  which  this  secretion  is 
poured  out  in  the  living  animal,  immediately  precedes  the  canal  traversed  by 
the  bolus  of  food  in  the  act  of  deglutition. 

Differential  Characters  in  the  Salivary  Glands  of  the  other  Animals. 

The  salivary  system  of  the  Herbivora  is  more  extensive  than  that  of  the  Omnivora,  and 
especially  the  Carnivora. 

Ruminants.  1.  Parotid  gland. — The  parotid  glands  of  the  Ox  are  distinguished  by  their 
meagre  development  and  red  colour,  whicli  contrasts  markedly  with  the  pale  yellow  hue  of  the 
maxillary  glands.  Tliose  of  the  Camel  have  the  same  characters,  and  they  are  broader  than 
they  are  long.  In  tlisit  animal,  as  well  as  in  the  Sheep  and  Goat,  Steno's  duct  passes 
through  the  mair^seter  muscle.  Moussu  has  seen  the  excito-motory  nerve  of  the  parotid,  in  the 
Ox,  become  detached  from  the  buccal  nerve  beneath  the  masseter  muscle,  become  inflected  on 
the  anterior  border  of  that  muscle,  and  pass  backward  and  downward  in  the  gland,  following 
Steno's  duct.  In  the  Sheep,  the  same  origin  and  course  ;  consequently,  the  nerve  passes  on  the 
surface  of  the  masseter,  along  with  Steno's  duct.  It  is  often  formed  by  two  parallel  filaments, 
and  is  easily  found  and  stimulated  in  order  to  produce  the  parotideal  secretion.  (In  the  Ox, 
this  gland  offers,  at  the  upper  part  of  its  anterior  border,  a  round  lobe  lying  on  the  masseter. 
Steno's  duct  opens  into  the  mouth  at  the  fifth  molar.  It  terminates  in  the  Sheep  and  Goat 
at  the  fourth  molar.) 

2.  Maxillary  gland. — In  the  Ox,  this  gland  is  much  thicker  than  in  Solipeds,  its  volume 
being  in  inverse  relation  to  that  of  the  parotid.  In  its  posterior  moiety  it  enlarges  into  an  oval 
lobe  which,  below  the  larynx,  lies  against  that  of  the  opposite  side.  Wharton's  duct  follows  the 
same  course  as  in  the  Horse;  the  papilla  through  which  it  opens  is  hard,  resisting,  and 
notched,  and  is  lodged  in  an  elliptical  fossette  near  the  incisors. 

The  maxillnry  gland  of  the  Camel  is  slightly  lobulated,  and  Wharton's  duct  docs  not  open 
at  the  summit  of  the  "  barb,"  but  at  the  base  of  the  fraenum  linguae  by  a  kind  of  punched-out 
opening. 

3.  Sublingual  gland. — In  the  Ox,  Sheep,  and  Goat,  this  gland  comprises  two  portions:  a 
posterior,  somewhat  voluminous  and  lobulated,  provided  with  a  .special  excretory  duct,  which 
follows  and  opens  near  Wharton's  duct  (by  the  ductus  Bartholinianus) ;  and  an  anterior, 
pouring  out  its  secretion  by  many  canals,  and  representing  the  gland  proper.  This  arrange- 
ment allows  the  saliva  to  be  collected  separately  from  this  gland.  In  the  Camel,  this  gland 
is  very  small,  its  lobules  being  also  loosely  agglomerated ;  it  has  only  multiple  ducts,  as  in  the 
Horse. 


440  THE  DIGESTIVE  APPABATUS  IN  MAMMALIA. 

4.  Molar  glands.— These  are  more  developed  in  Kuminants  than  in  Solipeds.  The  uppei 
one  is  enlarged  at  its  posterior  extremity.     Their  nerves  come  from  the  buccal  nerve. 

Pig.— The  parotid  gland  of  this  animal  is  little  developed,  as  in  Ruminants,  and  Steiio's 
duct  fullows  the  posterior  border  of  tlie  lower  jaw.  (Leyh  says  that  it  is,  proportionately, 
largely  developed ;  that  its  upper  end  does  not  reach  the  concha  of  the  ear,  and  that  Steno's 
duct  opens  at  the  sixth  molar.) 

The  sublingual  gland  is  analogous  in  its  disposition  to  that  of  the  Ox.  Cuvier,  in  his 
Lecons  d'A7iatomie  Compar^e,  indicates  this :— "  The  Pig  has  two  sublingual  glands.  One, 
very  long  and  narrow,  accompanies,  outwardly,  the  excretory  canal  of  the  submaxillary  gland, 
from  the  angle  of  the  jaw  to  tiie  second  sublingual.  It  is  composed  of  small  lobules  of  a  pale 
red  colour.  Its  excretory  duct  arises  near  the  posterior  third,  and  passes  along  with,  but  to 
the  outside  of,  the  submaxillary  duct.  It  terminates  near  the  orifice  of  the  latter  by  a  small 
opening;  its  diameter  is  equally  small.  The  second  sublingual  gland  is  placid  before  the 
first ;  its'  form  is  square  and  flattened,  and  the  lobes  of  which  it  is  composed  are  larger  and 
redder.  It  has  from  eight  to  ten  excretory  ducts."  (In  this  animal  the  duct  of  Wharton  does 
not  open  into  the  mouth  by  a  papilla ;  consequently,  there  is  no  barb.) 

Camivora.— The  parotid  of  the  Dog  and  Cat  is  small,  and  Steno's  duct  always  passes 
through  the  masseter.     (It  opens  at  the  fourth  molar  in  the  Dog,  and  the  third  in  the  Cat.) 

In  the  Dog,  the  mhmaxillary  glands  are  larger  than  the  parotids.  "  They  even  have  in 
front,  along  Wharton's  duct,  a  small  accessory  gland,  with  a  distinct  excretory  caiial  opening 
into  the  tame  papilla  as  Wharton's."  (Leyh  states  that  the  submaxillary  duct  does  not  project 
into  the  mouth.)     The  supplementary  gland  is  absent  in  the  Cat. 

The  sublingual  gland  is  not  present  in  the  Dog ;  it  is  very  .'<mall  in  the  Cat,  and  carried 
further  back  than  in  the  other  animals.  (Leyh  describes  a  sublingual  gland  as  jiresent  in  tht 
Camivora,  which  is  divided  into  two  portions,  as  in  the  Pig :  the  anterior  being  formed  of 
detached  lobules  that  open  into  the  mouth  by  several  ducts ;  and  the  posterior,  larger  above 
than  below,  with  two  ducts,  the  s;i;aller  opening  into  Wharton's  duct,  and  the  larger  a  little  in 
front  of  it.) 

The  upper  molar  gland  of  the  Dog,  scarcely  noticeable  for  the  greater  part  of  its  extent, 
forms  posteriorly,  under  the  zygomatic  arch,  near  the  eye,  an  independent  lobe,  remarkable  for 
its  large  size  and  its  single  excretory  duct.  Duvernoy,  who  first  described  it,  proposed  to  name 
it  the  suhzygomatic  gland.  It  is  not  present  in  the  Cat.  (This  is  doubtless  the  organ 
described  by  Leyh  as  the  orbital  gland,  which,  he  says,  is  only  found  in  the  Dog ;  the  superior 
molar  gland,  according  to  him,  not  existing  in  that  animal.  This  orbital  gland  is  external  to 
the  ocular  muscles,  has  three  or  four  excretory  canals— the  ductus  Nuckiani — which  converge 
into  one  duct  that  opens  into  the  month  above  the  last  molar.) 

The  labial,  lingual,  and  staplnjUne  glandulx  are  much  less  developed  in  the  Camivora  than 
the  Herbivora.  This  predominance  of  the  salivary  system  in  the  latter  is  sufficiently 
accounted  for,  when  we  consider  the  hard,  fibrous,  and  coriaceous  food  these  animals  live  upon, 
and  which  must  be  ingested  in  large  quantity,  because  of  the  small  amount  of  nutrition 
it  contains.  For  its  mastication  and  deglutition,  a  great  amount  of  saliva  is  absolutely 
necessary. 

Bodents. — In  the  Rabbit,  the  inferior  molar  gland  is  very  large.  In  addition  to  the 
salivary  glands  already  described,  this  animal  has  a  small  gland  outside  the  buccinator  muscle, 
along  the  interior  maxilla,  at  the  mental  foramen. 

Comparison  of  the  Salivary  Glands  of  Man  with  those  op  Animals. 

As  in  animals,  the  parotid  is  the  most  voluminous  of  the  salivary  glands.  Its  tissue  is 
reddish-grey  and  lobulated,  the  lobules  adhering  closely  to  each  other.  Its  shape  is  irregular, 
and  it  is  moulded  to  the  excavation  behind  the  angle  of  the  jaw.  Steno's  duct  passes  across 
the  masseter,  and  shows  on  its  eourse  some  salivary  lobules,  forming  what  is  named  the 
accessory  parotid  (or  socia  parotidis) ;  it  opens  opposite  the  third  upper  molar. 

The  submaxillary  gland  weighs  about  half  an  ounce.  It  is  partly  situated  beneath  the 
deep  cervical  fascia,  and  partly  within  the  body  of  the  lower  jaw,  between  the  mylo-hyoideus 
and  hyo-glossus  muscles.  Its  lobules  are  more  loosely  united  than  those  of  the  parotid. 
Wharton's  duct  opens  on  the  sides  of  the  frjenum  linguae  by  a  small  opening  at  the  apex  of  a 
round  papilla  (caruncida  sublingualis). 

The  sublingual  gland  is  analogous  to  that  of  the  Ox  and  Pig.  There  are,  in  fact,  two 
sublinguals :  an  anterior  about  the  size  of  an  almond,  and  furnished  with  a  single  excretory 
canal— the  ductus  Bartholini,  that  terminates  near  Wharton's  duct;  the  other,  posterior, 
formed  by  several  isolated  lobules  with  multiple  excretory  ducts — the  ductus  Riviniani. 


THE  PHARYNX. 


Fig.  249. 


There  are  also  labial,  ataphyline,  and  lingual  glands;  with,  besides,  near  the  frsenum,  a 
small  conglomerate  gland — the  gland  of  Nnhn — which  has  a  special  duct. 

The  Pharynx  (Figs.  249,  250,  251). 

Preparation. — 1.  Study  the  general  disposition  and  situation  of  this  vestibule  in  the 
antero-posterior  vertical  section  of  the  head  (Fig.  250).  2.  In  order  to  examine  the  interior 
conveniently,  the  head  should  be  separated  from  the  neck,  leaving  attached  to  it  a  certain 
portion  of  the  trachea  and  oesophagus ;  then  by  sawing  across — either  through  or  behind  the 
temporo-maxillary  articulations — all  that  portion  of  the  cranium  is  removed,  and  the  posterior 
parietes  of  the  pharynx  is  exposed,  and  may  be  dissected  to  study  the  muscles  (Fig.  251),  or 
opened  in  the  middle  line  to  reach  the  interior  of  the  cavity  (Fig.  249).  3.  The  muscles 
should  be  dissected  with  those  of  the  tongue,  and  in  the  same  manner. 

The  2jharynx  is  a  membranous  vestibule  common  to  the  digestive  and  air 
passages,  and  situated  behind  the  soft  palate, 
which  separates  it  from  the  mouth ;  above,  it  is 
attached  to  the  base  of  the  cranium,  and,  be- 
low, to  the  laryngeal  apparatus. 

Form  and  internal  disposition. — In  conse- 
quence of  the  conformation  of  the  soft  palate, 
which,  in  the  domesticated  animals,  and  par- 
ticularly in  Solipeds,  is  prolonged  to  the  base 
of  the  epiglottis,  the  pharynx  forms  a  cylindro- 
conical  cavity,  elongated  from  before  to  behind, 
enclosed  laterally  and  posteriorly  by  wide  thin 
muscles,  and  with  the  soft  palate  for  an  anterior 
wall.  Between  the  two  Eustachian  tubes,  under 
the  base  of  the  cranium,  the  pharyngeal  cavity 
presents  a  triangular  diverticulum,  the  walls  of 
which  are  only  mucous  membrane.  This  diverti- 
culum is  much  deeper  in  the  Ass  than  in  the 
Horse.^  At  the  two  extremities  of  this  cavity 
are  openings  which  allow  the  pharynx  to  com- 
municate with  the  other  passages  or  cavities, 
which  we  will  at  once  begin  to  study. 

At  the  upper  extremity  of  the  large  axis  of 
the  pharyngeal  cavity,  is  to  be  remarked  :  1.  In 
front,  the  two  posterior  openings  of  the  nasal 
cavities.  2.  Behind,  and  directly  opposite  the 
preceding,  the  two  pharyngeal  openings  of  the 
Eustachian  tubes,  which  are  closed  by  a  carti- 
laginous kind  of  clap- valve.  2 

At  the  inferior  extremity  of  this  axis  is  found  : 
1.  In  the  centre,  a  vast  gaping  orifice  project- 
ing into  the  interior  of  the  pharyngeal  cavity, 
like  a  tap  into  a  cask  :  this  is  the  entrance  to  the 
larynx,  the  salient  portions  of  which  form,  on  the  walls  of  the  pharynx,  two 


PHARYNGEAL  AND  LARYNGEAL  RE= 

gion;    the   posterior  part  of 
the  head  incised  and  thrown 

FORWARD. 

1,  Base  of  the  cranium  ;  2,  roof  of 
the  pharynx ;  3,  muscles  of  the 
cheek ;  4,  4,  walls  of  the  pharynx  ; 
6,  posterior  nares  ;  7,  soft  palate  ; 
8,  entrance  to  the  mouth ;  9,  epi- 
glottis ;  10,  posterior  pillars  of  soft 
palate;  11,  arytenoid  cartilages; 
12,  opening  of  the  oesophagus ;  13, 
oesophagus ;   14,  trachea. 


'  This  pharyngeal  cxcum  was  described  for  the  first  time  by  Verhsar  of  Utrecht. 

*  This  region  corresponds  to  the  posterior  nares  (arriere  fond)  of  Man,  a  diverticulum 
which  cannot  be  distinguished  from  the  pharynx  in  the  domesticated  animals.  Under  the 
designation  of  the  posterior  nares  of  the  nasal  fossx,  it  will  be  understood  that  we  mean  the 
posterior  extremities  of  these  cavities. 


442  TEE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

lateral  channels,  limited  superiorly  by  the  posterior  pillars  of  the  soft  palate. 
2.  In  front  of,  and  beneath  this,  is  the  isthmus  of  the  fauces ;  behind  and  above, 
the  oesophageal  opening  at  the  bottom  of  an  infundibulum,  which  may  be  con- 
sidered as  a  special  region  of  the  pharynx. 

These  seven  openings  into  the  pharyngeal  cavity  give  it  the  appearance  of 
a  cross  road,  into  which  abut  different  thoroughfares.  It  is  necessary  to  note 
that  the  air  and  digestive  passages  intersect  each  other  here  ;  and  in  such  a  way 
that,  during  deglutition,  the  bolus  of  food  passes  over  the  entrance  of  the  larynx 
to  reach  the  cesophageal  opening.  This  peculiarity  is  easily  seen  by  referring  to 
Fig.  250. 

Relations. — Viewed  externally,  for  the  study  of  its  connections,  it  will  be 
found  that  the  pharynx  is  related,  posteriorly,  to  the  guttural  pouches,  and 
guttural  or  retro-pharyngeal  lymphatic  glands  ;  laterally,  to  the  great  cornu  of  the 

Fig.  250. 


MEDIAN   LONGITUDINAL   SECTION   OF   HEAD   AND   UPPER   PART   OF   NECK. 

1,  Upper  lip;  2,  premaxilla;  3,  hard  palate;  4,  tongue;  5,  septum  nasi;  6,  nasal  bone;  7,  palatine 
bone;  8,  soft  palate;  9,  pterygoid  bone;  10,  epiglottis;  11,  entrance  to  Eustachian  tube:  12, 
arytenoid  cartilage;  13,  cricoid  cartilage;  14,  oesophagus;  15,  frontal  bone  ami  sinus;  16,  cere- 
brum; 17,  corpus  callosum ;  18,  cerebellum;  19,  sphenoid  bone;  20,  medulla  oblongata,  21, 
cervical  ligament;  22,  spinal  cord;  23,  occipital  bone;  24,  24,  atlas;  25,  25,  dentata;  26?  trachea. 

OS  hyoides,  the  internal  pterygoid  and  stylo-hyoid  muscles,  the  glosso-pharyngeal, 
great  hypoglossal,  and  superior  laryngeal  nerves,  and  the  glosso-facial  artery. 

Steucture. — The  walls  of  the  pharynx  are  composed  of  a  mucous  membrane^ 
external  to  which  is  a.  fibrous  and  a  muscular  lager. 

1.  Murnvs  membrane. — This  membrane  is  covered,  externally,  by  a  thin 
layer  of  yellow  elastic  fibres,  and  is  much  more  delicate  and  less  protected  by 
its  epithelium  than  the  buccal  mucous  membrane,  of  which  it  is  a  continuation  ; 
it  is  continuous  with  that  of  the  oesophagus,  the  larynx,  the  nasal  fossa?,  and 
the  Eustachian  tubes. 

Its  epithelium  is  stratified  throughout ;  but  it  is  thin  and  ciliated  in  the  upper 
part,  thicker  and  tes^elated  on  the  inferior  moiety,  which  more  particularly 
belongs  to  the  digestive  apparatus. 

Everywhere  there  are  rfwemose  glands,  though  they  are  most  numerous 
towards  the  roof  of  the  pharynx.     There  are  also  some  follicular  glands  beneath 


THE  PHARYNX. 


413 


the  mucous  membrane,  in  the  neighbourhood  of  the  guttural  opening,  the  nasal 
cavities,  and  the  Eustachian  tubes.  Lorge  has  described  a  lymphoid  gland, 
analogous  to  the  pharyngeal  amygdalae  described  by  Kolliker,  at  the  bottom  of 
the  diverticulum  between  the  Eustachian  tubes. 

2.  Fibrous  layer. — This  is  also  named  the  pharyngeal  aponeurosis.  It  com- 
mences at  the  base  of  the  cranium,  is  first  seen  on  the  posterior  face  of  the 
pharynx,  then  it  passes  beneath  the  muscular  layer,  where  it  gradually  becomes 
thinner.  It  is  attached  inferiorly  to  the  cartilages  of  the  larynx,  and  to  a 
fibrous  cord  that  separates  the  pharynx  from  the  oesophagus. 

3.  Muscular  layer. — This  is  composed  of  six  pairs  of  muscles,  indicated  in 

Fig.  251. 


PHARYNX   OF   THE   HORSE   (POSTERIOR   VIEW). 

T,  Trachea;  t,  thyroid  gland  ;  O,  cesophagus  ;  e,  e.  Eustachian  tubes,  divided  near  their  termination  in 
the  pharynx.  1,  Pterygo-pharyngeus,  or  superior  constrictor ;  2,  2,  stylo-pharyngeal  muscles ; 
3,  3,  great  cornua  of  the  os  hyoideus ;  4,  hyo-pharyngeus,  or  middle  constrictor;  5,  5,  thyro- 
pharyngeus,  or  thyroid  fasciculus  of  the  inferior  constrictor;  6,  crico-oesophageus ;  7,  superior 
longitudinal  oesophageal  muscle  ;  8,  origin  of  the  oesophagus ;  9,  posterior  crico-arytaenoid  muscle. 


the   following  enumeration  :    the  palato-pharyngeus,  pterygo-pharyngeus,    hyo- 
pharyngeus,  thyro-pharijngeus,  crico-pharyngeus,  stylo-phnryngeus. 

Palato-pharyngeus  {Pharyngo-staphyUnus). — This  muscle,  which  has 
already  been  described  as  belonging  to  the  soft  palate,  is  prolonged  backwards 
on  the  lateral  wall  of  the  pharynx,  where  its  fibres  are  mixed  with  those  of  the 
pterygo-pharyngeus,  and  go  to  be  attached  to  the  superior  border  of  the  thyroid 
cartilage,  by  passing  beneath  the  hyo-pharyngeus  and  thyro-pharyngeus  muscles. 


444  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

It  therefore  also  belongs  to  the  pharynx,  and  in  contracting  diminishes  that 
cavity. 

Pterygo-pharyngeus,  or  Superior  Constrictor  (the  palato-pharyngeus 
of  Percivall). — This  muscle  is  thin,  wide,  flat,  and  triangular.  It  arises  from 
the  pterygoid  process,  whence  its  fibres  diverge,  some  posteriorly,  others  in- 
wardly. The  former  mis  with  those  of  the  palato-pharyngeus,  and  comport 
themselves  like  that  muscle  ;  and  the  latter  are  united,  on  the  median  line,  with 
the  analogous  fibres  of  the  opposite  muscle,  forming  a  kind  of  zone  around  the 
origin  of  the  Eustachian  tube.  This  muscle  is  covered,  externally,  by  a  layer  of 
yellow  elastic  tissue,  which  is  attached  with  it  to  the  pterygoid  bone  :  afterwards 
it  is  fixed  to  the  superior  border  of  the  great  cornu  of  the  os  hyoides,  and  is 
even  prolonged  on  the  external  surface  of  the  muscle  it  covers  to  the  thyroid 
cartilage. 

The  elasticity  of  this  fibrous  layer  plays  a  certain  part  in  the  movements  of 
the  hyo-laryngeal  apparatus,  in  acting  as  a  passive  antagonist  of  its  depressors. 

This  muscle  is,  and  can  only  be,  a  perfect  constrictor  o''  the  pharynx,  as  it 
diminishes  the  diameter  of  that  cavity  in  every  directiuu — the  longitudinal 
diameter,  by  means  of  its  posterior  fibres,  which  draw  the  thyroid  cartilage 
forward  ;  and  its  transverse  diameter,  by  the  band  thrown  around  the  orifice  of 
the  Eustachian  tubes  (Figs.  220,  6  ;  251,  1  ;  252,  8). 

Hyo-pharyngeus,  or  Middle  Constrictor  ;  Thyro-pharyngeus,  or 
First  Middle  Constrictor  ;  and  Crico-pharyngeus,  or  Inferior  Con- 
strictor.— The  two  last  of  these  muscles  only  form  one  in  Man — the  inferior 
ronstrirtor  of  the  pharynx.  They  are  three  muscular  bands  which  terminate 
above  the  pharynx,  on  a  median  fibrous  fold,  sometimes  wide  enough  to  look 
like  a  triangular  aponeurosis.  The  first  band  arises  from  the  cornu  of  the  os 
hyoides  ;  the  second,  from-  the  external  surface  of  the  thyroid  cartilage  ;  the 
third,  from  the  superficial  face  of  the  cricoid  cartilage. 

These  are  universally  regarded  as  constrictors  (Figs.  220,  7,  8,  9  ;  251,  4, 
5,  5). 

In  attentively  examining  the  crico-pharyngeus  muscle  of  different  authorities, 
two  fasciculi  are  recognized,  which  can  be  distinguished  by  the  direction  of  their 
fibres.  The  deep  band  passes  to  the  origin  of  the  oesophagus  ;  it  will  be  described, 
as  well  as  the  muscle  hitherto  npmed  the  arytaeno-pharyngeus,  when  the  oesophagus 
is  referred  to. 

Stylo-pharyngeus. — A  narrow  band  which  descends  from  the  inner  surface 
of  the  styloid  bone  on  the  side  of  the  pharynx,  where  it  is  confounded  with  the 
pterygo-pharvngens.  It  passes  beneath  the  hyo-thyroid  and  crico-pharyngeal 
muscles,  and,  spreading  out  like  a  fan,  becomes  attached  to  the  upper  border  of 
the  thyroid  cartilage  and  mucous  membrane  of  the  pharynx,  above  the  posterior 
pillar  of  the  soft  palate. 

It  narrows  the  longitudinal  diameter,  and  it  has  been  also  regarded  as  a 
dilator  ;  though  the  disposition  of  the  parietes  of  the  pharynx  and  the  feeble 
volume  of  this  muscle,  scarcely  allow  it  to  play  any  efficacious  part  in  the 
dilatation  of  that  cavity.  At  most,  it  can  only  produce  a  very  slight  infundi- 
bulum  where  it  is  inserted.  The  real  dilating  agent  of  the  pharyngeal  cavity  is 
the  alimentary  bolus,  which  is  pushed  into  it  by  the  action  of  the  tongue  and 
soft  palate  (Fig.  251,  2,  2). 

It  is  not  rare  to  find  a  second  stylo-pharyngeus  muscle,  terminating  at  the 
same  point  as  the  first,  but  proceeding  from  the  inferior  extremity  of  the  large 


TEE  PHARYNX. 


445 


cornu  of  the  os  hyoides,  or  styloid  bone,  instead  of  its  upper  part ;  its  fibres  pass 
beneath  the  hyo-  and  thyro-hyoideus  muscles,  and  proceed  upwards  in  crossing 
the  direction  of  the  preceding  muscle,  terminating  on  the  middle  raphe  on  the 
superior  face.    It  pulls  the  upper  wall  of  the  pharynx  backwards  and  downwards. 

Certain  anatomists  designate  it  the  inferior  stylo-pharyngeus,  and  consider  it 
as  a  constrictor  of  the  pharynx.     It  sometimes  exist  only  on  one  side. 

3.  Vessels  and  nerves. — The  blood  sent  to  the  pharynx  comes  from  the 
pharyngeal  and  thyroideal  arteries.  The  nerves  are  supplied  by  the  glosso- 
pharyngens,  pneumogastric,  and  great  sympathetic. 

Functions. — The  pharynx  plays  a  passive  part  in  respiration,  by  servmg  as 
an  intermediate  canal  between  the  nasal  passages  and  the  larynx. 

Its  principal  function,  however,  is  connected  with  the  digestive  phenomena, 
by  its  being  an  active  agent  in  the  first  stage  of  deglutition — a  complex  and 
rapid  movement,  which  is  executed  in  the  following  manner  :  The  bolus  of  food, 
propelled  by  the  tongue  into  the  pharynx,  is  seized  by  the  constrictor  muscles, 

Fig.  252. 


MUSCLES   OF    THE    PHARYNGEAL    AND    HYOIDEAL    REGIONS. 

1,  Glenoid  cavity  of  temporal  bone ;  2,  superior  extremity  of  styloid  bone ;  3,  tensor  palati  with 
its  pulley,  5;  4,  stylo-pharyngeus;  6,  palato-pharyngeus ;  7,  circumflexus  palati;  8,  pterygo- 
pharyngeus;  9,  sublingual  gland;  10,  portion  of  hyoid  bone;  11,  hyo-pharyngeus ;  12,  thyro- 
pharyngeus;  13,  crico-pharyngeus ;  14,  portion  of  stylo-pharyngeus;  15,  hyo-thyroideus ;  16, 
styloid  bone;  17,  crioo-arytenoideus  lateralis;  18,  oesophagus;  19,  sterno-maxillaris  and  hyoideus, 
and  subscapulo-hyoideus ;  20,  trachea;  21,  hard  palate;  22,  tongue. 


which  come  into  action  successively  from  before  to  behind,  in  a  peristaltic  and 
involuntary  manner,  to  carry  the  mass  to  the  entrance  of  the  cesophagus.  The 
food  thus  passes  over  the  opening  of  the  larynx  during  pharyngeal  deglutition, 
but  it  cannot  enter  it,  becauses  the  bolus  forces  back  the  epiglottis  on  this 
aperture,  which  it  almost  exactly  closes  ;  because,  also,  the  passage  of  the  food 
prevents  pulmonary  inspiration,  which  might,  if  allowed  to  take  place,  divert  it 
from  its  natural  course,  and  throw  it  into  the  nasal  air-passages.  The  applica- 
tion of  the  walls  of  the  pharynx  to  the  pellet  of  food  during  its  momentary 
passage  over  the  larynx,  prevents  all  communication  between  the  external  air 
and  the  lungs,  and  only  permits  the  elevation  of  the  ribs  with  the  utmost 
difficulty.  The  extreme  rapidity  of  the  act  of  deglutition  is  another  reason  for 
the  food  escaping  the  larynx. 
31 


446  TEE  DIGESTIVE  APPARATUS  IN   MAMMALIA. 

(Gray  concisely  remarks  :  "When  deii-lutition  is  about  to  be  performed,  the 
pharynx  is  drawn  upwards  and  dilated  in  different  directions,  to  receive  the 
morsel  propelled  into  it  from  the  mouth.  The  stylo-pharyngei,  which  are  much 
further  removed  from  one  another  at  their  origin  than  at  their  insertion,  draw 
upwards  and  outwards  the  sides  of  this  cavity — the  breadth  of  the  pharynx,  in 
the  autero-posterior  direction,  being  increased  by  the  larynx  and  tono'ue  being 
carried  forwards  in  their  ascent.  As  soon  as  the  morsel  is  received  in  the 
pharynx,  the  elevator  muscles  relax,  the  bag  descends,  and  the  constrictors  con- 
tract upon  the  morsel  and  convey  it  gradually  downwards  into  the  a-sophagus.) 

The  deglutition  of  liquids  is  carried  on  in  a  similar  manner. 

It  is  curious  to  remark  that,  in  Solipeds,  the  food  does  not  come  into  direct 
contact  with  the  greater  portion  of  the  superior  wall  of  the  pharynx  during  its 
passage  through  that  cavity.  When  the  alimentary  mass  is  carried  back  by  the 
tongue,  it  raises  the  soft  palate  and  bears  the  posterior  border  of  this  backwards 
to  the  entrance  of  the  oesophagus.  The  extreme  development  of  this  palatine 
curtain,  therefore,  quite  prevents  this  surface  of  the  pharynx  from  being  directly 
applied  to  the  food,  and  it  is  through  the  medium  of  this  partition  that  the 
constrictors  exercise  their  peristaltic  action  on  the  morsel  of  aliment,  until  it 
reaches  the  oesophageal  orifice. 

Differential  Characters  op  the  Pharynx  in  the  other  Animals. 

The  iiharynx  nf  Ruminants  is  elongated  and  very  spacious.  The  hj-o-,  thyro-,  and  crico- 
pharyngeal  muscles— the  middle  constrictor  aud  inferior  constrictors— are  less  distinct  from 
each  otiier  tlian  in  the  Horse:  the  inferior  constrictor  is  very  small,  and  the  fibrous  raphe  on 
which  the  constrictors  unite  is  little  developed.  In  the  pharynx  of  the  Ox  and  Sheep  is 
noticed  a  mucous  fold  that  descends  to  the  middle  of  the  posterior  wall,  and  appears  to  be  a 
continuation,  posteriorly  and  inferiorly,  of  the  nasal  septum;  whence  results  the  formation  of 
two  glanduhir  pharyngeal  caeca  at  their  bottom. 

In  t  ie  Camel,  this  organ  is  remarkable  for  the  large  dimensions  of  its  longitudinal  direc- 
tion and  its  relative  narrowness.  The  posterior  pillars  of  the  soft  i)aLite  unite  at  a  great 
distance  above  the  entrance  to  the  cesophafrus,  and  the  pharynx  appears  to  be  divided  into  two 
compartments  by  a  transverse  mucous  fold,  which  is  detached  from  the  posterior  wall.  The 
superior  compartment  thus  formed,  shows,  above,  the  guttural  openings  of  the  nasal  cavities — 
openings  which  are  narrow  and  vertically  elongated — and  the  orifices  of  the  Eustachian  tubes ; 
while  iit  the  bottom  of  the  inferior  compartment  is  the  oesophageal  infnndibulum  and  the 
entrance  to  the  larynx.     The  pharyngeal  mucous  membrane  in  this  animal  is  black  in  colour. 

In  the  Pig,  the  f)haryngeal  caecum  is  sacculated,  and  its  mucous  membrane  is  very  vascular, 
and  rich  in  closed  follicles. 

In  the  Dog,  the  infundibulum  is  very  spacious.  The  posterior  pillars  of  the  soft  palate 
subside  on  the  walls  of  the  pharynx  befce  reaching  the  entrance  to  the  oesophagus.  The 
pharyngeal  mucous  membrane,  much  finer  than  that  of  the  oesophagus,  is  distinguished  from 
it  by  a  sharp  line  of  de:tnircation,  and  here  it  is  very  rich  in  glands.  The  crico-ph.tryngeal  is 
not  very  distinct  from  the  tljyro-pharyngeal  muscle;  so  that,  in  reality,  only  three  constrictors 
can  be  distinguished. 

Comparison  of  the  Pharynx  of  Man  with  that  of  Animals  (Fig.  253). 

In  consequence  of  tlie  smallness  of  the  soft  palate,  the  pharynx  of  Man  is  only  a  kind  of 
channel  between  the  mouth  and  the  larynx  and  oesophagus.  It  is  usually  divided  into  three 
portions  :  a  superior,  the  posterior  nares,  covered  by  ciliated  epithelium  ;  a  middle,  or  guttural, 
and  an  inferior,  or  oesophageal.     The  two  latter  are  covered  with  tesselated  epithelium. 

The  muscles  are  almost  the  same  as  in  the  Dog,  being  a  portion  of  the  jialato-pharyngeus, 
the  superior,  middle,  and  inferior  constrictors,  and  a  stylo-pharyngeal  muscle. 

Below  the  sides  of  the  pharynx,  and  between  the  pillars  of  the  soft  palate,  are  the 
amygdalae — almond-shaped  organs,  the  surface  of  which  shows  the  openings  of  the  follicles 
that,  with  the  vessels  and  a  little  connective  tissue,  compose  their  substance. 


TEE  (ESOPHAGUS. 


447 


Fig.  253. 


The  (Esophagus  (Figs.  254,  255). 

PreparaUon. — Place  the  subject  in  the  second  or  third  position  ;  remove  the  cervical 
panniculus  from  the  left  side ;  take  away  the  corresponding  anterior  limb,  and  proceed  to  the 
excision  of  the  ribs  of  this  side,  with  the  exception  of  the  first.  Afterwards  dissect  the  vessels 
and  nerves  in  the  neighbourhood  of  the  oesophagus,  taking  care  to  preserve  their  relations  with 
each  other. 

Form. — The  oesophagus  is  a  long,  cyhndrical,  narrow,  membranous  canal,  a 
little  wider  below  its  commencement,  easily  dilated  for  the  greater  part  of  its 
extent,  destined  to  convey  the  food  from  the  pharynx  to  the  stomach,  and 
so  to  complete  the  act  of  deglutition. 

Course. — It  begins  at  the  pharynx,  and  communicates  with  it  by  means  of 
the  posterior  opening  situated  above  the  glottis.  It 
is  so  narrow  when  not  in  use,  that  it  admits  with 
diflficulty  the  tip  of  the  finger.  Behind,  it  is  circum- 
scribed by  a  fibro-mucous  cord  that  is  related  to  the 
junction  of  the  posterior  pilhrs  of  the  soft  palate ; 
in  front,  by  the  external  surface  of  the  arytsenoid 
cartilages.  It  afterwards  descends  behind  the  trachea 
to  the  middle  of  the  neck,  where  it  commences  to 
deviate  towards  the  left  side  of  that  tube,  and  enters 
the  thoracic  cavity  by  inclining  towards  the  inner 
aspect  of  the  first  left  rib.  It  soon  after  regains  its 
situation  above  the  trachea,  passes  over  the  base  of 
the  heart,  and  reaches  the  opening  in  the  right  pillar 
of  the  diaphragm,  in  passing  between  the  two  layers 
of  the  posterior  mediastinum.  Traversing  this  open- 
ing, it  enters  the  abdominal  cavity,  and  immediately 
afterwards  is  inserted  into  the  smaller  curvature  of 
the  stomach  by  an  orifice  designated  the  cardiac,  which 
will  be  studied  at  the  same  time  as  that  viscus. 

Relations. — The  oesophagus  in  its  course  has  the 
following  numerous  relations  : — 

At  its  origin,  it  is  comprised  between  the  guttural 
pouch  and  the  posterior  crico-arytenoid  muscles. 

In  the  cervical  region,  it  is  enveloped  in  a  thick 
layer  of  connective  tissue,  which  unites  it  in  a  loose 
manner  to  the  surrounding  organs,  its  relations  with 
these  varying  as  we  consider  them  superiorly  or  in- 
feriorly.  Superiorly,  and  in  the  median  plane,  it 
occupies  the  space  included  between  the  trachea  and 
the  longus-colli,  being  bordered  on  each  side  by  the 
common  carotid  artery,  with  its  satellite  nerves — the 

trunk  common  to  the  great  sympathetic  and  pneumogastric,  and  the  inferior 
laryngeal.  Inferiorhj,  it  is  related  to  the  trachea  on  the  inner  side  ;  and,  exter- 
nally, to  the  inferior  scalenus  muscle,  and  the  vessels  and  nerves  in  the  left 
cervical  channel,  which  also  includes  the  jugular  vein.^ 

'  It  is  not  absolutely  rare  to  find  the  oesophagus  deviate  to  the  right  in  the  lower  part  of 
the  neck ;  in  this  case  its  relations  will  be  reversed.  We  have  never  seen  this  canal  enter  the 
thorax  in  the  median  plane  of  the  body. 

In  Horses  with  a  flat  trachea,  the  oesophagus  is  sometimes  in  the  middle  of  the  upper 


HUMAN   PHARYNX  LAID   OPEN 
FROM    BEHIND. 

1,  Section  through  base  of 
skull;  2,  2,  walls  of  pha- 
rynx drawn  aside  ;  3,  3, 
posterior  nares,  separated 
by  the  vomer ;  4,  extremity 
of  one  Eustachian  tube ;  5, 
soft  palate ;  6,  posterior 
pillar  of  soft  palate ;  7,  an- 
terior pillar ;  8,  root  of  the 
tongue,  partly  concealed  by 
the  uvula  ;  9,  epiglottis 
overhanging  (10)  the  cordi- 
forra  opening  of  the  larynx ; 

11,  posterior  part  of  larynx  ; 

12,  opening  of  oesophagus, 
13 ;  14,  trachea. 


448  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

At  its  entrance  into  the  thoracic  cavity,  the  oesophagus,  still  deviating  to  the 
left,  and  lying  on  the  side  of  the  trachea,  responds,  externally,  to  the  inferior 
cervical  gangUon,  the  afferent  and  emergent  nerves  of  that  ganglion,  the  ver- 
tebral arteries  and  veins,  and  the  superior  cervical  and  dorso-muscular  vessels, 
which  obliquely  cross  its  direction.  Beyond  this  it  regains  its  position  between 
the  trachea  and  the  longus  colli,  passes  above  the  left  bronchus,  to  the  right  of 
the  thoracic  aorta,  until  it  reaches  between  the  layers  of  the  posterior  mediasti- 
num, which  bring  it  into  relation  with  the  internal  face  of  the  limgs  ;  these  are 
channeled  for  its  reception,  and  here  it  is  accompanied  by  the  oesophageal  artery, 
and  the  oesophageal  branches  of  the  pneumogastric  nerve. 

The  very  short  portion  lodged  in  the  abdominal  cavity  is  related,  on  the 

Fig.  254. 


TRANVERSE   VERTICAL   SECTION   OF    HEAD    AND    NECK    IMMEDIATELY     IN     FRONT    OF    THE    STYLOID 
PROCESSES,    AND    BEHIND   THE   (ESOPHAGUS. 

I,  (Esophagus ;  2,  inner  surface  of  trachea ;  3,  common  carotid  artery ;  4,  recurrent  nerve ;  5, 
thyroid  gland;  6,  exterior  of  pharynx;  7,  crico-pharyngeus  muscle;  8,  9,  10,  11,  guttural  pouch 
and  objects  in  its  interior  ;  12,  stylo-pharyngeus  muscle  ;  13,  sphenoid  bone  ;  14,  jugular  ganglia; 
15,  internal  carotid;  16,  17,  pneumogastric  nerve;  18,  parotid  gland;  19,  great  hypoglossal 
nerve;  20,  jugular  vein;  21,  subscapulo-hyoideus ;  22,  stylo-maxillaris. 


right,  to  a  fissure  in  the  superior  border  of  the  Hver,  and  is  enveloped  by  the 
peritoneum.     It  terminates  about  the  upper  third  of  the  sixteenth  rib. 

Interior. — Internally,  the  oesophagus  presents  nothing  of  interest ;  and  it 
only  requires  to  be  remarked,  that  its  walls  are  always  shrunken  and  in  contact 
when  food  is  not  passing  between  them.  It  appears  narrower  in  consequence  of 
its  inflections  or  relations  with  other  organs  :  1.  Near  its  commencement.  2.  At 
its  entrance  to  the  thorax.     3.  At  its  passage  through  the  diaphragm. 

Structuee. — The  oesophagus  has  two  tunics — a  mucous  and  a  muscular. 

The  mucous  membrane  is  continuous  with  that  of  the  pharynx  and 
stomach ;  it  is  white,  and  shows  numerous  longitudinal  folds,  which  allow  the 

surface  of  that  tube  ;  in  other  cases  it  is  drawn  to  the  inferior  face,  below  the  sterno-maxillaris 
muscles,  along  with  the  carotid  artery  and  its  satellite  nerves,  the  jugular  vein  maintaining  its 
position. 


THE  (ESOPHAGUS. 


449 


canal  to  dilate.  It  adheres  but  loosely  to  the  muscular  coat,  on  which  it  can 
glide  with  the  greatest  facility.  It  has  a  thick,  resisting,  stratified,  tesselated 
epithelium,  an  unstriped  muscular  layer,  and  some  racemose  glands. 

(A  third  or  middle  coat  is  sometimes  mentioned  by  anatomists  ;  it  is  com- 
posed of  the  tissue  connecting  the  latter  tunic  with  the  one  to  be  next  described.) 

The  muscular  coat  commences  at  the- posterior  part  of  the  pharynx  by  the 
ari/teno-ossophageal  and  superior  longitudinal  casophageal  muscles  (Fig.  251).  The 
aryteno-msophageal  muscle  is  an  extremely  thin,  small  band  in  Solipeds,  situated 
on  the  posterior  border  of  the  arytenoid  cartilage,  at  the  commencement  of  the 
(esophagus,  where  its  fibres  disappear.  To  expose  this  muscle — which  represents 
the  inferior  longitudinal  oesophageal  of  some  authorities,  the  oesophagus  should 
be  turned  forwards  on  the  upper  surface  of  the  pharynx. 

The  superior  longitudiiial  m^ophageal  muscle  is  a  small  superficial  band,  the 


Fig    255. 


PECTORAL   CAVITY   AND   MEDIASTINUM,    SHOWING   THE   COURSE   OF   THE   TRACHEA 
AND    (ESOPHAGUS. 


A,  Anterior  mediastinum ;  B,  posterior  mediastinum ;  c,  the  heart  and  pericardium 
part  of  the  mediastinum;  d,  diaphragm;  E,  trachea;  F,  oesophagus. 


the  middle 


fibres  of  which  leave  the  base  of  the  fibrous  triangle  that  occupies  the  posterior 
face  of  the  pharynx,  to  disappear  on  the  surface  of  the  oesophagus,  where  some 
of  them  form  loops  at  different  elevations. 

To  these  muscles  at  the  commencement  of  the  oesophagus,  must  be  added 
the  crico-obsofhagecd,  which  leaves  the  deep  face  of  the  crico-pharyngeus  to  pass 
to  the  border  of  the  oesophagus,  where  its  fibres  proceed  above  and  below  that  tube, 
in  joining  those  of  the  muscle  of  the  opposite  side.  This  muscle  compresses  the 
oesophagus  at  its  commencement,  in  the  same  way  as  Wilson's  muscle  acts  upon 
the  urethra. 

The  remainder  of  this  muscular  tunic  is  formed  of  superficial  longitudinal 
fibres,  often  assembled  in  fasciculi :  and  of  a  deeper  series  of  spiral  or  circular 
fibres,  which,  towards  the  inferior  extremity  of  the  canal,  intercross  in  an  almost 
inextricable  manner.  This  muscular  layer  in  the  cervical,  and  for  a  great  part 
of  the  thoracic  portion  of  the  oesophagus,  has  aknost  the  red  colour  of  voluntary 


450  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

muscles ;  but  it  becomes  white,  like  the  involmitary  fibres,  after  the  tube 
enters  the  mediastinum,  and  acquires  cousiderable  thickness  and  marked  rigidity 
in  the  dead  animal.  It  is  to  be  noted  that  this  arrangement  of  the  muscular 
tunic  is  especially  evident  towards  the  insertion  of  the  oesophagus  into  the 
stomach,  and  that  the  muscular  tube  is  at  this  point  so  narrow,  that  it  is  almost 
exactly  occupied  by  the  folds  of  mucous  membrane  it  contains.  For  this  reason 
it  is  that,  in  this  state  of  cadaveric  rigidity,  we  may  inflate  a  stomach  by  the 
pylorus  without  applying  a  ligature  to  the  oesophagus  ;  the  aperture  of  the 
canal  being  so  perfectly  closed  that  it  does  not  allow  a  bubble  of  air  to  escape. 
In  describing  the  interior  of  the  stomach,  we  will  refer  to  the  consequences 
resulting  from  this  interesting  anatomical  fact. 

Vessels  and  nerves. — The  oesophagus  is  supplied  with  blood  by  the  divisions 
given  off  by  the  common  carotid  artery,  as  well  as  the  bronchial  and  oesophageal 
arteries.  The  nerves  are  almost  exclusively  derived  from  the  pneumogastric ; 
the  motor  nerves  are  the  superior  oesophageal  filaments — branches  of  the 
external  pharyngeal  and  laryngeal ;  the  sensitive  filaments  are  derived  from 
the  recurrent  nerve.  For  the  portion  beyond  the  heart,  the  sensitive-motor  nerves 
are  supplied  by  the  oesophageal  nerves  of  the  pneumogastric,  though  in  an 
asymmetrical  manner. 

Functions. — This  canal  conveys  nutriment  from  the  pharynx  to  the 
stomach  ;  it  has  no  other  uses. 

Differential  Characters  of  the  (Esophagus  in  the  other  Animals. 

In  all  the  other  domesticated  animals,  the  muscular  coat  is  red-coloured  throughout  its 
whole  extent,  and  everywhere  offers  the  same  degree  of  thickness  and  the  same  flaccidity.  The 
canal  is  also  as  wide  towards  the  stomach  as  at  the  pharynx.  In  Rdminants  and  the  Car- 
NivoRA,  it  enters  the  stomach  as  a  funnel-shaped  (infundibuliform)  tube. 

In  the  Camel,  the  mucous  membrane  adheres  more  closely  to  the  muscular  tissue  than  in 
Solipeds,  according  to  Colin. 

The  dilatability  of  the  oesophagus  is  very  remarkable  in  these  animals :  Dogs  swallow  large 
pieces  of  flesh ;  and  Cows  and  Oxen  are  able  to  ingest  large  turnips,  or  such  voluminous  foreign 
bodies  as  shoes. 

(In  Ruminants  and  the  Carnivora  the  oesophagus  is,  proportionally^,  wider  than  in  the 
Horse  and  Pig.) 

Comparison  of  the  (Esophagus  of  Man  with  that  of  Animals. 

The  oesophagus  of  Man  resembles  that  of  Carnivora;  its  diameter  is  almost  uniform.  It 
also  inclines  to  the  left  below  the  neck,  but  in  the  thorax  is  in  the  median  line,  though  it  again 
deviates  to  the  left  as  it  joins  the  stomach.  As  the  thyroid  in  Man  is  very  voluminous,  it  is 
related  to  the  oesophagus  in  the  upper  part  of  the  neck.  Two  small  accessory  fasciculi,  belong- 
ing to  the  muscular  tunic  of  the  oesophagus,  have  been  described :  one  is  the  broncho- oesophageal 
muscle,  which  is  detached  from  the  left  bronchus;  and  the  other  the  pleuro -oesophageal  muscle, 
detached  from  the  left  layer  of  the  posterior  mt  diastinum. 

Article  II.— The  Essential  Oegans  of  Digestion. 

These  organs  being  all  contained  in  the  abdominal  cavity,  this  common 
receptacle  will  first  be  studied  ;  afterwards  the  sfomach,  intestines,  and  their 
annexed  organs — the  liver,  pancreas,  and  spleen — will  be  described. 

The  Abdominal  Cavity. 

In  Mammalia,  the  interior  of  the  trunk  is  partitioned  by  the  diaphragm 
into  two  great  cavities,  which  lodge  the  majority  of  the  organs  so  vaguely 


TEE  ABDOMINAL   CAVITY.  451 

termed  the  "viscera."  The  anterior,  the  smallest,  is  the  pectoral  or  thoracic 
cavity ;  the  posterior  is  named  the  ahdomen,  or  abominal  cavity. 

Form  of  the  Abdominal  Cavity. — The  abdomen  is  a  vast  oval-shaped  reservoir, 
elongated  from  before  to  behind,  having  for  its  upper  wall  the  muscles  of  the 
sublumbar  region,  enclosed  below  and  laterally  by  the  muscles  of  the  inferior 
abdominal  region,  bounded  in  front  by  the  diaphragm,  and  prolonged  behind 
between  the  bones  and  membranous  hgaments  of  the  pelvis. 

The  parts  forming  the  walls  of  this  cavity  having  been  already  described,  we 
will  confine  ourselves  to  an  examination  of  its  interior,  in  order  to  determine  the 
various  regions  into  which  it  is  possible  to  divide  it — a  matter  of  some  impor- 
tance, as  it  singularly  facilitates  the  topographical  study  of  the  contained  viscera ; 
for  to  say  that  an  organ  is  situated  in  the  abdomen,  is  a  very  vague  reference  to 
its  precise  situation,  in  consequence  of  the  great  extent  of  this  cavity.  It  is 
necessary,  therefore,  to  divide  the  abdomen  into  a  certain  number  of  peripheral 
regions  which  will  correspond  to  the  different  parts  of  its  wall,  with  a  view  to 
define  the  situation  of  the  organs  lodged  therein,  yet  without  complicating 
anatomical  description.  Six  principal  regions  are  recognized  in  the  abdominal 
cavity. 

A.  The  superior,  or  sublumbar  region,  corresponds  to  the  superior  wall  of  the 
abdomen  ;  that  is,  to  the  psoas  muscles  and  the  bodies  of  the  lumbar  vertebrae. 
It  extends  from  the  opening  between  the  two  pillars  of  the  diaphragm  to  the 
entrance  to  the  pelvis. 

B.  The  inferior  region,  limited,  laterally,  by  the  hypochondriacs  and  the 
flanks,  commences,  in  front,  at  the  xiphoid  cartilage,  and  is  prolonged  to  the 
pubis  ;  it  comprises  all  that  portion  of  the  abdomen  which  corresponds  to 
the  linea  alba  and  the  two  recti  muscles.  Its  great  extent  necessitates  its  sub- 
division into  five  secondary  regions  :  The  supra-sternal  region,  named  the  epigastric 
in  Man,  placed  above  the  xiphoid  cartilage  of  the  sternum  ;  the  umbilical  region, 
situated  behind  the  preceding,  and  so  named  in  consequence  of  its  including  that 
part  of  the  wall  which  is  pierced  by  the  umbilicus  ;  the  prepubic  region — the 
hypogastric  or  pubic  of  Man — occupies  the  space  in  front  of  the  anterior  border 
of  the  pubis  ;  the  tivo  inguinal  regions,  diverticuli  of  the  abdominal  cavity,  located 
in  the  inguinal  tracts,  where  they  form  the  special  reservoirs  to  be  hereafter 
described  as  the  vaginal  sheaths  (or  inguinal  canals). 

C.  The  lateral  regions  {right  and  left  lumbar  of  Man)  are  limited  :  in  front, 
by  the  costal  attachments  of  the  diaphragm  ;  behind,  by  the  entrance  to  the 
pelvic  cavity  ;  above,  by  the  superior  border  of  the  small  oblique  muscle  ;  below, 
by  the  interval  comprised  between  the  inferior  border  of  that  muscle  and  the 
external  border  of  the  great  rectus  muscle.  The  designation  of  hypochondrific 
is  given  to  the  sub-region  which  corresponds  to  the  cartilaginous  circle  of  the 
false  ribs.  The  flank  is  that  section  covered  by  the  muscular  portion  of  the 
small  oblique  muscle. 

D.  The  anterior,  or  diaphragmatic  region,  comprises  the  cavity  formed  by  the 
posterior  face  of  the  diaphragm.  Like  that  muscle,  it  is  divided  into  two  regions, 
a  central  and  peripheral. 

E.  The  posterior,  or  pelvic  region,  is  a  special  diverticulum  of  the  abdomen 
described  as  the  pelvic  cavity.  It  is  bounded,  above,  by  the  sacrum  ;  below,  by 
the  superior  face  of  the  pubes,  the  ischia,  and  the  internal  obturator  muscle  ;  on 
the  sides,  by  the  constricted  portions  of  the  ossa  innominata  and  the  sacro-sciatic 
ligaments.     The  entrance  to  this  diverticulum  is  situated  above  the  pubes  and 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


Fig.  256. 


is  of  an  oval  form.     Posteriorly,  it  is  narrower,  and  is  traversed  by  the  rectum 
and  the  e^enito-urinary  organs,  which  open  externally. 

The  Peritoneum. — The  abdominal  cavity  is  lined,  internally,  by  a  serous 
membrane,  the  peritoneum,  which  will  now  be  briefly  described. 

Like  all  the  splanchnic  serous  membranes,  the  peritoneum  is  composed  of  a 
parietal  and  a  visceral  layer,  which  together  form  a  closed  sac  so  arranged  that  the 
organs  contained  in  the  abdomen  are  situated  external  to  this  sac.  The  adjoining 
theoretical  figure  (256),  representing  a  transverse  section  of  the  abdominal  cavity, 
will  show  at  a  glance  this  arrangement.  Let  a  represent  the  section  of  the  small 
intestines  floating  at  liberty  in  the  interior  of  the  cavity  ;  b,  that  of  the  aorta,  at 
the  level  of  the  great  mesenteric  artery  :  the 
peritoneal  membrane,  c  c,  covers  the  walls  of  the 
abdomen,  and  at  the  points  D,  D  is  folded  around 
the  great  mesenteric  artery,  in  such  a  manner 
as  to  form  two  layers,  f,  f,  which  come  in  con- 
tact by  their  adherent  faces,  reach  the  intestine, 
and  then  separate  to  envelop  it.  We  then  see 
in  this  figure  the  parietal  layer  of  the  peritoneum 
C  C,  the  visceral  layer,  G  g,  and  the  two  layers, 
F,  F,  which  establish  the  continuity  of  the 
parietal  and  visceral  portions  ;  the  complete  sac 
formed  by  these  is  apparent,  and  it  could  be 
rendered  more  so  by  the  further  separation  and 
development  of  the  layers  f,  f  ;  so  that  there  is 
no  difficulty  in  understanding  how  the  small 
intestine  may  be  at  the  same  time  in  the  inferior  of 
the  abdominal  cavity,  and  outside  the  sac  formed 
by  the  serous  membrane  which  lines  that  cavity. 
This  arrangemer.t  is  common  to  all  the  organs  freely  suspended  in  the  abdo- 
men. The  serous  folds  which  suspend  them,  in  joining  their  peritoneal  layer  to 
that  which  covers  the  parietes  of  the  cavity,  will  be  studied  under  the  names  of 
ligaments,  mesenteries,  and  omenta.  Some  organs — the  kidneys,  for  example — 
have  no  proper  visceral  layer,  being  contained  between  the  abdominal  wall  and 
the  external  face  of  the  parietal  peritoneum,  and  are  invested  with  none  of  the 
duplicatures  just  mentioned. 

We  will  briefly  study  the  duplicatures,  ligaments,  mesenteries,  and  omenta  that 
the  peritoneum  forms,  starting  from  the  umbilicus  and  passing  forwards  and 
backwards  (Fig.  2,')7). 

On  reaching  t!ie  supra-sternal  region,  the  peritoneum  forms  a  falciform  dupli- 
cature,  extending  from  the  umbilicus  to  the  middle  lobe  of  the  liver,  and  which 
is  even  prolonged  between  that  lobe  and  the  posterior  face  of  the  diaphragm  ;  at 
the  free  border  of  this  fold  is  a  thickening,  which  is  regarded  as  the  remains  of 
the  obliterated  umbilical  vein.  In  becoming  doubled  over  the  neighbouring 
organs,  the  diaphragmatic  portion  constitutes  :  1.  The  ligaments  of  the  right  and 
left  lobes  of  the  liver.  2.  The  common  ligament  of  that  gland,  which  surrounds 
the  posterior  vena  cava.  3.  The  cardiac  ligament  that  envelops  the  termination 
of  the  oesophagus.  Behind  the  liver  is  found  the  hepato-gastric  ligament,  which 
fixes  the  stomach  in  the  posterior  fissure  of  the  liver,  and  is,  to  the  right  and 
backwards,  attached  to  the  duodenum  at  the  lower  face  of  the  right  kidney  ;  it 
is  then  directed  from  right  to  left,  and  becomes  continuous  with  the  parietal 
peritoneum  of  the  sublumbar  region  and  the  mesentery  proper. 


THEORETICAL  TRANSVERSE  SECTION 
OF  THE  ABDOMINAL  CAVITY,  TO 
SHOW  THE  DISPOSITION  OF  THE 
PERITONEUM. 


THE  ABDOMINAL  CAVITY.  453 

The  two  layers  of  the  hepato-gastric  ligament  separate  at  the  lesser  curvature 
of  the  stomach,  to  cover  that  viscus  ;  then  join  at  its  greater  curvature,  and  pass 
to  the  interior  of  the  abdominal  cavity.  This  fold  receives  the  name  of  the  great 
or  gastro-coUc  omentum  ,-  it  leaves  the  left  tuberosity  of  the  ventriculus,  which  it 
suspends  to  the  sublumbar  region  from  the  whole  extent  of  the  great  curvature  ; 
to  the  right  it  goes  beyond  the  pylorus,  to  be  continued  on  the  concave  curvature 
of  the  duodenum,  as  far  as  the  cascum.  By  its  posterior  border,  the  great  omen- 
tum is  extended  around  the  termination  of  the  large  colon  and  the  origin  of  the 
floating  colon,  where  it  is  confounded  with  the  visceral  peritoneum  of  these  organs, 
as  well  as  with  the  parietal  peritoneum.  It  results  from  this  arrangement,  that 
the  great  omentum  forms  behind  the  stomach,  and  in  front  of  the  adherent  portion 
of  the  large  colon,  a  space  that  communicates  with  the  great  peritoneal  cavity 
by  a  veiy  naiTow  opening — the  foramen  of  WinslouK  This  aperture  is  included 
between  the  vena  portas,  posterior  vena  cava,  anterior  extremity  of  the  pancreas, 
and  the  lesser  cm-vature  of  the  stomach.     To  the  left  of  the  latter  viscus,  on  the 


THEORETICAL    LONGITUDINAL   AND    MEDIAN    SECTION    OF    THE    ABDOMINAL    CAVITY,    TO    SHOW   THE 
REFLECTIONS   OF    THE    PERITONEUM. 

1,  Liver ;  2,  stomach ;  3,  small  intestine ;  4,  origin  of  the  floating  colon ;  5,  rectum  ;  6,  vagina  and 
uterus;  7,  bladder;  9,  posterior  aorta ;  10,  diaphragm;  11,  posterior  vena  cava;  12,  inferior 
abdominal  wall.  Pp,  Pp,  parital  peritoneum ;  Pv,  Pv,  visceral  peritoneum ,  L,  gastro-hepatic 
ligament ;  M,  mesentery ;  Ge,  great  omentum. 


external  face  of  the  great  omentum,  the  spleen  is  suspended  ;  consequently,  that 
portion  extending  from  the  spleen  to  the  ventriculus,  is  named  the  gastro-splenic 
omentum. 

The  two  layers  composing  the  great  omentum  are  very  thin  for  the  greater 
part  of  theii'  extent,  and  enclose  the  blood-vessels  between  them.  In  emaciated 
animals,  these  vessels  are  distinctly  seen,  owing  to  the  transparency  of  the  mem- 
branes, and  they  give  the  omentum  a  lacework  appearance  ;  but  in  fat  subjects 
they  are  concealed  by  the  adipose  tissue  deposited  along  their  course,  and  which 
may  accumulate  in  considerable  quantity. 

In  the  sublumbar  region,  the  parietal  peritoneum  forms  several  folds  ;  these 
are  :  the  hepatico-renal  ligament.,  extending  from  the  right  lobe  of  the  liver  to  the 
anterior  border  of  the  right  kidney  ;  the  ligament  of  tJie  lobus  Spigelii,  the  mesen- 
tery proper,  the  colic  mesentery  ;  lastly,  the  greatly  developed  layers  suiTOunding 


454  THE  DIGESTIVE  AFPARATUS  IN  MAMMALIA. 

the  cfecum  and  the  second  flexure  of  the  colon,  which  constitute  the  meso-coecum 
and  meso-colon. 

The  great  mesentery  is  detached  from  around  the  large  mesenteric  artery,  and 
projects  into  the  abdominal  cavity  to  reach  the  small  intestine  at  the  lesser 
curvature,  and  to  envelop  that  viscus. 

Its  shape  is  that  of  an  irregular  triangle,  the  summit  of  which  corresponds  to 
the  mesenteric  artery,  the  very  short  anterior  border  being  continuous  with  the 
duodenal  frjenum,  and  the  posterior  border,  the  longest,  with  the  meso-colon,  its 
convex  festooned  base  being  as  long  as  the  intestine  itself.  Between  the  two 
layers  that  compose  it,  are  the  blood-vessels  and  lymphatics,  as  well  as  the  nerves, 
of  the  small  intestine. 

The  colic  mesentery  is  formed  like  the  great  mesentery.  Its  inferior  border, 
plane  or  plicated,  is  fixed  to  the  small  curvature  of  the  floating  colon  and  the 
commencement  of  the  rectum  ;  its  upper  border  extends  from  the  great  mesenteric 
artery,  as  far  as  the  entrance  to  the  pelvic  cavity. 

Around  the  cross  of  the  ctecum,  from  the  origin  to  the  termination  of  the 
great  colon,  the  peritoneum  is  reflected  to  cover  these  viscera  ;  a  layer  passes 
from  the  anterior  border  of  the  caecum  on  to  the  ileum  and  the  second  flexure  of 
the  colon — this  is  the  meso-ccmum  ;  another  layer,  comprised  between  the  second 
and  third  portion  of  the  colon — the  shape  of  which  is  that  of  a  battledore,  is 
named  the  meso-colon. 

If,  again,  the  peritoneum  is  taken  at  the  umbilical  region  and  followed  back- 
wards, it  will  be  found  to  insinuate  itself  into  the  inguinal  canals,  cover  the 
organs  contained  in  the  pelvis,  and  become  reflected  at  the  bottom  of  that  cavity, 
to  be  continued  either  with  the  peritoneum  of  the  sublumbar  region,  or  with  that 
on  the  lateral  walls  of  the  abdomen. 

TMs  serous  membrane  covers  the  fundus  of  the  bladder,  and  at  this  point  it 
has  three  ligaments.  The  middle  ligament,  falciform  in  shape,  leaves  the  large 
extremity  of  the  bladder,  is  attached  to  the  anterior  border  of  the  pubis,  and 
insensibly  disappears  on  the  inferior  abdominal  wall ;  on  its  free  border  is  a  small 
fibrous  cord,  which  is  supposed  to  be  the  remains  of  the  urachus.  The  two  lateral 
ligaments  are  more  developed,  and  extend  from  the  entrance  to  the  pelvic  cavity 
to  the  vesical  fundus  ;  they  have  on  their  free  border  the  obliterated  umbilical 
arteries.  In  the  male,  the  peritoneum  is  prolonged  from  the  upper  face  of  the 
bladder  to  the  enlargement  of  the  deferent  ducts,  between  which  it  sends  a  trans- 
verse fold  to  the  anterior  extremity  of  the  vesiculse  seminales,  and  is  then 
reflected  around  the  rectum. 

In  the  female,  it  is  carried  from  the  bladder  to  the  terminal  portion  of  the 
vagina,  to  the  uterus,  and  to  the  cornua  of  that  organ,  where  it  forms  three  folds 
named  the  broad  ligaments,  ligamefits  of  the  ovary,  and  the  round  ligament ;  then 
it  re-descends  on  the  upper  face  of  the  vagina,  and  thence  envelops  the  rectum, 
around  which  it  is  reflected  from  behind  forwards. 

According  to  this  arrangement,  we  see  that  the  termination  of  the  digestive 
canal,  and  the  parts  of  the  genito-urinary  organs  situated  altogether  at  the 
posterior  portion  of  the  pelvic  cavity,  are  placed  outside  the  peritoneal  serous 
membrane. 

Structuee. — Like  all  the  serous  membranes,  the  peritoneum  is  formed  by  a 
membrane  of  connective  tissue,  rich  in  elastic  fibres,  and  covered  on  its  free  face 
by  an  endothelial  layer  (the  cells  of  Avhich  are  flat  and  polygonal,  and  about  ^-^ 
of  an  inch  in  diameter).     Many  blood-vessels  are  found  on  the  adherent  surface  ; 


THE  STOMACH  465 

while  lymphatics  are  abundant  in  the  visceral  layer  ;  they  are  independent,  or 
form  a  sheath  around  the  blood-vessels  of  the  mesentery.  Its  nerves  come  from 
the  diaphragmatic,  lumbar,  and  intercostal  branches,  and  the  great  sympathetic. 

Differential  Characters  in  the  Abdominal  Cavity  of  the  other  Animals, 

In  the  Carnivora.  the  abdominal  cavity  is  very  narrow;  while  in  Ruminants  it  is  very 
vast,  its  capacity  being  in  direct  relation  to  the  volume  of  the  viscera  it  contains. 

The  general  arrangement  of  the  peritoneum  varies  but  little  in  the  different  species,  the 
only  notable  diversities  being  remarixed  in  the  great  omentum.  In  the  Ox,  Sheep,  and 
Goat,  this  is  detached  from  the  middle  of  the  lower  face  of  the  rumen,  and  envelops  the  right 
sac  of  that  organ,  fixing  the  fourth  compartment  to  its  great  curvature,  and  then  passing  upwards, 
to  become  continuous  with  tiie  mesentery.  In  the  Dog  and  Pig,  this  fold  descends  in  front 
of  the  intestinal  mass,  until  near  the  pelvis ;  then  it  ascends  in  gathering  on  itself,  and 
ultimately  spreads  over  the  colon ;  in  the  middle  portion  of  the  great  omentum  there  are, 
consequently,  four  layers  laid  against  each  other. 

Comparison  of  the  Abdominal  Cavity  of  Man  with  that  of  Animals. 

The  abdominal  cavity  of  Man  is  elongated  vertically,  and  has  an  inferior  cavity  occupying 
the  entrance  to  the  pelvis.  There  is  nothing  particular  to  note  in  its  disposition,  the  differences 
observed  in  it  being  allied  to  tlie  external  shape  of  the  body.  The  peritoneum  is  spread  over 
its  parietes  nearly  in  the  same  manner  as  in  the  Carnivora ;  the  great  omentum  is  formed  by 
four  layers,  and  covers  the  intestines  like  an  apron ;  between  its  two  layers  is  the  lesser  cavity 
of  the  omentum,  virtually  in  the  adult. 

The  Stomach. 

The  stomach  is  a  membranous  sac  placed  between  the  oesophagus  and 
intestinea,  and  in  which  is  completed  the  division  of  the  alimentary  matters. 


The  Stomach  in  Solipeds  (Figs.  258,  259,  260,  261) 


Preparation. — In  order  to  study  the  relations  of  this  organ,  it  suflBces  to  open  the  abdomen 
and  remove  the  intestinal  mass  in  the  following  manner:  Place  the  animal  in  the  first 
position,  and  very  slightly  inclined  to  the  left  side;  make  an  incision  througli  the  inferior 
abdominal  wall,  or,  still  better,  carry  it  away  entirely  by  a  circular  incision,  taking  care  not 
to  wound  any  part  of  the  intestine.  The  entire  viscera  should  then  be  withdrawn  from  the 
abdominal  cavity,  and  laid  on  the  table  which  supports  the  subject ;  for  this  mass  cannot  be 
allowed  to  fall  on  the  ground  without  risk  of  being  pulled  and  torn,  either  in  the  intestine 
itself,  or  those  parts  which  it  is  desired  to  preserve  intact  in  the  abdomen.  Incise  the  floating 
colon  where  it  joins  the  rectum,  and  the  duodenum  where  it  passes  behind  the  great  mesenteric 
artery;  the  base  of  the  caecum  should  now  be  detached  from  the  sublumbar  surface  by  the 
rupture  of  the  connective  tissue  which  connects  it  to  the  right  kidney  and  the  pancreas;  the 
cellular  connection  between  the  latter  gland  and  the  terminal  extremity  of  the  fourth  portion 
of  the  large  colon  should  also  be  broken ;  after  this,  it  is  only  necessary  to  divide  the  attach- 
ment of  the  mesenteric  bands  to  the  sublumbar  region,  with  the  vessels  contained  between 
them.  The  intestinal  mass  is  then  definitely  expelled  from  tlie  abdominal  cavity.  In  this 
way  it  is  possible  to  expose,  and  conveniently  prepare,  not  only  the  stomach,  but  also  tlie 
spleen,  liver,  pancreas,  kidneys,  ureters,  etc.  Nothing  more  remains  than  to  make  known  the 
procedure  to  be  adopted  in  everting  the  stomach,  in  order  to  study  its  internal  surface,  or 
dissect  its  deep  muscular  layer.  It  is  recommended,  first,  to  excise  tiie  stomach  with  at  least 
three  inches  of  the  oesophagus,  and  eight  inches  of  the  duodenum,  and  cleanse  the  interior  of 
the  organ.  This  may  be  done  in  several  way^,  but  the  following  is  the  simplest:  a  certain 
quantity  of  water  is  introduced  into  the  stomach  by  fixing  the  duodenum  to  a  water-tap,  the 
right  hand  manipulating  the  organ  while  the  left  closes  the  duodenum  to  prevent  the  escape 
of  the  liquid.  The  alimentary  substances  contained  in  it  are  in  this  way  mixed  with  the 
water,  and  may  be  expelled  from  the  duodenum  by  pressing  the  stomach  ;  this  operation,  being 
repeated  four  or  five  times,  thoroughly  cleanses  the  cavity  of  the  organ.  To  evert  the  inner 
surface,  it  is  only  necessary  to  introduce  by  the  duodenum  a  loop  of  wire,  and  make  it  pass 
through  the  cesophagus ;  a  strong  waxed  thread  is  fastened  in  the  loop  and  firmly  fixed  around 


456 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


the  oesophagus,  when,  in  pulling  back  the  wire,  this  extremity  is  drawn  towards  tlie  pylorus, 
and  by  careful  traction  the  latter  is  so  dilated  as  to  allow  the  passage  of  the  cardiac  end,  and 
complete  eversion  of  the  stomach.  Inflation  will  then  give  it  its  normal  form  and  disposition? 
with  this  difference,  that  the  mucous  membrane  is  external,  and  the  serous  tunic  internal. 

Lastly,  to  render  the  muscular  layers  of  the  stomach  more  evident,  it  is  advisable  to  plunge 
the  organ  into  boiling  water  for  some  minutes,  after  which  it  should  be  put  into  cold  water. 
If  it  is  desired  to  study  the  external  and  middle  layers,  the  stomach  should  be  inflated,  and  its 
serous  covering  removed  by  strips  with  foiceps  and  the  fingers;  if  the  deep  layer  is  to  be 


examined,  the  mucous  membrane  must  be  removed  oy  means  of  the  forceps  and  scalpel  from 
a  stomach  previously  everted. 

Situation. — The  stomach,  also  designated  the  ventriculus,  is  situated  in  the 
diaphragmatic  region  of  the  abdomen,  where  it  has  a  direction  transverse  to 
the  median  plane  of  the  body. 

Dimensions. — Its  average  capacity,  in  an  ordinary-sized  Horse,  is  from  3  to  3^ 
gallons  ;  but  it  varies  greatly  according  to  the  bulk  of  the  animal,  its  breed,  and 


TEE  STOMACH. 


457 


the  nature  of  its  food.  Relatively,  it  is  more  considerable  in  common-bred 
Horses,  and  in  the  Ass  and  Mule.  When  empty,  its  average  weight  is  between 
3  and  4  pounds. 

Ji'orm. — Elongated  laterally,  curved  on  itself,  often  constricted  in  its  middle, 
and  slightly  depressed  from  before  to  behind,  this  reservoir  presents,  externally  : 
1.  Ttvo  faces — an  anterior  and  posterior,  smooth  and  rounded.  2.  A  great  or 
convex  curvature,  forming  the  inferior  border  of  the  organ,  and  giving  attach- 
ment, throughout  its  extent,  to  the  great  omentum — a  membranous  fold  which 
has  been  described  as  a  dependency  of  the  serous  membrane.  8.  A  lesser  or 
concave  curvature,  into  which  the  oesophagus  is  inserted,  and  which  is  united,  to 
the  right  of  that  canal,  to  the  liver,  by  means  of  a  fraenum  known  as  the  hepato- 


Fig.  259. 


STOMACH   OF   THE   HORSE. 

A,  Cardiac  end  of  the  oesophagus ;  b,  pyloric  end  and  ring. 


gastric  ligament.  4.  A  left  extremity  (the  cardiac),  dilated  in  the  form  of  a  large 
conical  tuberosity,  and  constituting  the  left  cul-de-sac  {or  fundus)  of  the  stomach. 
5.  A  right  extremity  (the  pyloric),  narrower,  curved  upwards,  and  continued  by 
the  duodenum,  from  which  it  is  separated  by  a  marked  constriction — this  is  the 
right  cul-de-sac  of  the  stomach. 

Relations. — Studied  in  its  connections  with  the  neighbouring  organs,  the 
stomach  is  related  :  by  its  anterior  face,  with  the  diaphragm  and  liver ;  by  its 
posterior  face,  with  the  diaphragmatic  curvature  of  the  colon.  Its  inferior 
border,  margined  to  the  left  by  the  spleen,  which  is  suspended  from  it  by  means 
of  the  great  omentum,  is  separated  from  the  inferior  abdominal  wall  by  the 
large  anterior  flexures  of  the  colon ;  its  distance  from  this  wall  depends  upon 


458  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

the  fulness  of  the  organ.  The  left  extremity,  suspended  to  the  subliunbar  region 
by  the  aid  of  a  very  short  serous  ligament — a  portion  of  the  great  omentum — is 
related  to  the  base  of  the  spleen,  the  left  extremity  of  the  pancreas,  and,  less 
directly,  to  the  anterior  border  of  the  left  kidney.  The  right  extremity,  lower 
than  the  left,  touches  the  right  lobe  of  the  liver  and  the  above-mentioned 
intestinal  curvatures. 

Interior. — When  a  stomach  is  opened  to  study  its  interior,  one  is  at  first 
struck  by  the  different  aspect  its  internal  membrane  presents,  according  as  it  is 
examined  to  the  right  or  the  left.  To  the  left,  it  has  all  the  characters  of  the 
oesophageal  mucous  membrane,  in  being  white,  harsh,  and  even  resisting  ;  it  is 
covered  by  a  thick  layer  of  epithelium.  To  the  right,  it  is  thick,  wrinkled, 
spongy,  very  vascular  and  follicular,  has  a  reddish-brown  tint  that  is  speckled 
by  darker  patches,  loses  its  consistency,  and  is  only  covered  by  a  very  thin 
epithelial  pellicle.     It  is  not  by  an  insensible,  but  a  sudden  transition  that  the 

mucous    membrane   of  the   stomach   is   thus 
Fig.  260.  divided  into  two  portions  ;  and  their  separation 

is  indicated  by  a  salient,  more  or  less  sinuous, 
but  sharply  marked  ridge.     This  ridge,  then, 
divides  the  stomach  into  two  compartments — 
a  division  already  indicated  externally,  by  the 
circular  depression  observed  in  the  majority 
of   subjects.      The  left  sac  or  compartment  is 
considered  as  a  dilatation  of  the  oesophagus. 
The  right  sac  constitutes  the  true  stomach  of 
Solipeds  ;  as  on  it  alone  devolves  the  secretory 
function  which  elaborates  the  gastric  juice,  the 
essential  agent  of  digestion  in  this  organ. 
The   interior   of  the  stomach  (Fig.  260) 
iNTLRioR  OF  THE  HORSLS  STOMACH,      o^^rs  for  study  two  apcrturcs  :  the  cardiac  and 
A,  Left  sac ;  b,  right  sac ;  c,  duodenal    Py^oric.    The  cardiac,  OT  Oesophageal  orifice,  is  in 
dilatation.  the  Icsser  curvature   of  the  left  sac   of  the 

stomach.  Its  arrangement  have  given  rise  to 
numerous  discussions,  as  in  it  has  generally  been  sought  the  reason  why  Sohpeds 
vomit  with  such  extreme  difficulty.  At  one  time  there  was  described  a  semilunar 
or  spiroidal  valve,  which  is  opposed  to  the  retrograde  movement  of  the  food  ;  and 
at  another  time  it  was  the  oblique  insertion  of  the  oesophagus,  resembling  that 
of  the  ureters  into  the  bladder,  and  which,  by  a  mechanism  analogous  to  these, 
proved  an  obstacle  to  the  return  of  aliment  into  that  oesophagus.  Both  suppo- 
sitions are  wrong.  When  we  attentively  observe  the  manner  in  which  the 
oesophagus  comports  itself  at  its  termination,  it  will  be  noticed  that  it  is  inflected 
downwards,  after  traversing  the  right  pillar  of  the  diaphragm,  and  is  inserted 
almost  perpendicularly  into  the  lesser  curvature  of  the  stomach.  In  opening 
into  this  viscus,  the  oesophagus  does  not  widen  into  an  infundibulum,  as  in  other 
animals  ;  on  the  contrary,  its  calibre  is  here  narrower  than  elsewhere,  and  its 
cardiac  or  stomachal  orifice,  completely  obstructed  by  the  folds  of  mucous 
membrane,  only  occupies  an  infinitely  small  portion  of  the  internal  surface  of 
the  stomach. 

With  regard  to  the  pylorus,  it  represents  a  large  aperture  formed  at  the 
bottom  of  the  right  sac,  and  furnished  with  a  thick  circular  ring  ;  this  opening 
can  be  completely  closed  through  the  action  of  the  powerful  sphincter  surrounding 


THE  STOMACH.  459 

it.  It  is  furnished  with  a  valve  (the  pyloric  valve),  formed  by  the  union  of  the 
cellular  and  mucous  tunics,  and  the  sudden  disappearance  of  the  circular  muscular 
fibres. 

Structuee. — The  parietes  of  the  stomach  are  formed  by  three  membranes  : 
an  external,  or  serous  ;  a  middle,  or  muscular ;  and  an  internal,  or  mucom. 

1.  Serous  membrane. — This  membrane,  derived  from  the  peritoneum,  adheres 
closely  to  the  muscular  layer,  except  towards  the  curvatures.  At  the  lesser 
curvature,  it  is  constantly  covered  by  an  expansion  of  yellow  elastic  tissue,  the 
use  of  which  appears  to  be  to  maintain  the  two  extremities  of  the  stomach  near 
each  other  ;  for  when  this  is  destroyed,  the  lesser  curvature  becomes  considerably 
elongated.  Along  the  whole  of  the  greater  curvature  is  a  triangular  space 
occupied  by  connective  tissue  ;  this  space  disappears  more  or  less  completely  as 
the  organ  becomes  distended. 

It  has  three  folds,  which  are  detached  from  the  stomach  and  carried  on  to 
the  adjacent  parts,  and  are  formed  in  the  manner  indicated  in  the  general 
description  of  the  peritoneum.  These  folds  constitute  the  cardiac  ligament,  the 
gastro-hepatic  ligament  or  omentum,  and  the  great  omentum. 

The  cardiac  ligament  is  a  short,  serous  band  developed  around  the  terminal 
extremity  of  the  cesophagus,  and  strengthened  by  fibres  of  yellow  fibrous  tissue. 
It  attaches  the  stomach  to  the  posterior  face  of  the  diaphragm,  and  is  continuous, 
on  each  side,  with  the  two  folds  about  to  be  described. 

The  gastro-hqmtic  (or  lesser)  ligament  is  a  band  composed  of  two  layers, 
which  leave  the  lesser  curvature  of  the  stomach,  and  are  inserted  into  the 
posterior  fissure  of  the  liver.  It  is  prolonged  posteriorly,  and  to  the  right,  along 
the  duodenum,  where  it  constitutes  a  peculiar  serous  frsenum,  which  will  be 
studied  with  the  small  intestine. 

The  great  or  gastro-colic  omentum,  is  detached  from  the  whole  extent  of 
the  great  curvature,  from  the  cardia  to  the  pylorus,  beyond  which  it  extends 
to  the  duodenum.  The  portion  surrounding  the  left  cul-de-sac  is  excessively 
short,  and  is  carried  to  the  sublumbar  wall  of  the  abdomen,  to  which  it  fixes  the 
stomach.  For  the  remainder  of  its  extent,  this  omentum  is  greatly  developed, 
and  hangs  freely  in  the  abdominal  cavity,  among  the  intestinal  convolutions. 
The  border  opposed  to  the  stomach  is  attached  to  the  terminal  portion  of  the 
large  colon,  and  to  the  origin  of  the  floating  colon.  (For  further  details,  see 
the  description  of  the  peritoneum.) 

These  three  ligaments  fix  the  stomach  in  the  abdominal  cavity,  m  addition 
to  the  oesophagus  and  duodenum,  which  are  continuous  with  it. 

2.  Muscular  memhrane. — This  tunic,  comprised  between  the  serous  and 
mucous  layers,  is  lined  internally  by  a  coveiing  of  condensed  connective  tissue 
which  adheres  intimately  to  it,  and  may  be  regarded  as  the  fibrous  membrane  of 
the  stomach.  Dissection  shows  this  muscular  tunic  to  be  composed  of  three 
superposed  planes. 

The  superficial  plane  envelops  all  the  right  sac,  and  the  majority  of  its  fibres 
are  spread  in  loops  around  the  left  ctd-cle-sac,  their  extremities  being  lost  on 
the  surfaces  of  the  organ.  Some  of  them  even  extend  over  the  great  curvatm'e, 
to  the  surface  of  the  right  sac  ;  while  others  are  evidently  continuous  with  the 
superficial  fibres  of  the  oesophagus  (Fig.  261,  a). 

The  middle  plane  (Fig.  261,  b)  is  formed  of  circular  fibres  spread  over  the 
whole  of  the  organ.  In  the  right  sac,  they  are  placed  immediately  beneath  the 
serous  membrane  ;  in  the  left  sac,  they  pass  beneath  the  fibres  of  the  superficial 


460  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

plane,  and  finish  by  becoming  mixed  so  intimately  with  these,  that  towards  the 
tuberosity  formed  by  the  left  extremity  it  is  impossible  to  distinguish  them.  By 
their  aggregation  around  the  pylorus,  they  constitute  the  sphincter  {ov  pyloric 
valve)  which  envelops  that  orifice. 

The  deep  plane  (Fig.  261,  a),  like  the  first,  is  specially  destined  for  the  left 
sac,  and  cannot  be  properly  studied  except  in  an  averted  stomach  deprived  of  its 
mucous  membrane.  Much  thicker  than  the  superficial  plane,  it  yet,  in  its 
general  arrangement,  much  resembles  it.  Thus,  its  fasciculi  present  loops  which 
embrace  the  left  cul-de-sac,  and  the  extremities  of  which  are  lost  on  the  faces  of 
the  organ,  where  some  of  them  become  continuous  with  the  circular  fibres.  The 
loops  nearest  the  oesophagus  embrace  the  stomachal  opening  of  that  canal  like  a 
cravat.     It  is  to  be  remarked  that  the  fibres  of  this  deep  layer  intersect  those  of 


Fig.  261. 


Fig.  262. 


MUSCULAR   FIBRES   OF   THE   STOMACH 
(external    and    middle    LAYERS). 

A,  Fibres  of  the  external  layer  enveloping 
the  left  sac;  B,  fibres  of  the  middle 
plane  in  the  right  sac ;  C,  fibres  of  the 
pylorus. 


deep  and  middle  muscular  layer  ex- 
posed BY  removing  the  MUCOUS  MEM- 
BRANE  FROM   AN   EVERTED   STOMACH. 

A,  Deep  layer  of  fibres  enveloping  the  left 
sac  ;  B,  fibres  of  the  middle  plane  which 
alone  form  the  muscular  layer  of  the 
right  sac ;  C,  fibres  of  the  pylorus. 


the  superficial  plane  —the  former  passing  from  the  left  to  the  right  sac,  in 
inclining  downwards  towards  the  great  curvature,  while  the  latter  are  directed 
to  the  right  and  slightly  upwards. 

From  this  arrangement  it  results,  as  a  glance  at  Figs.  261  and  262  will  show  : 
1.  That  the  right  sac  has  only  a  singular  muscular  plane.  2.  That,  on  the  con- 
trary, the  left  sac  has  three,  all  of  which  concur  in  propelling  the  ahment  that 
has  accumulated  in  the  left,  or  oesophageal  reservoir,  into  the  right,  or  true 
stomach. 

3.  Mucous  membrane. — Independently  of  the  general  characters  noted  in  the 
interior  of  the  stomach,  it  has  to  be  remarked  that  the  gastric  mucous  membrane 
is  united  to  the  preceding  tunic  by  an  expansion  of  connective  tissue  ;  though  it 
adheres  but  feebly  throughout  the  right  sac,  especially  towards  the  greater 
curvature,  where  it  is  thickest  ;  and  that  it  has  no  ridges  in  the  left  sac,  though 
in  the  right  they  are  always  present,  even  when  the  organ  is  inflated. 

On  the  surface  of  this  membrane  are  seen  microscopical  apertures  {alveoli) — 
the  orifices  of  the  excretory  ducts  of  glands  ;  these  are  rare  in  the  left  sac, 
but  extremely  numerous  in  the  right.     In  this  region  they  are  separated  from 


THE  STOMACH. 


461 


each  other  by  minute  processes  resembling  papillae  ;  but  the  latter  are  only  met 
with  in  the  vicinity  of  the  pylorus. 

The  gastric  mucous  membrane  is  composed  of  an  epithelial  layer  and  a  corium, 
in  which  are  distinguished  a  glandular  and  a  muscular  laijer.  The  epitheUum  is 
stratified  and  tesselated  in  the  left  compartment,  simple  and  calyciform  in  the 
right  sac,  where  it  covers  the  little  mucous  processes  that  separate  the  glandulae, 
and  penetrates  more  or  less  deeply  into  the  interior  of  these,  becoming 
spheroidal. 

In  the  left  side,  in  the  vicinity  of  the  pylorus,  there  are  found  some 
racemose  glands  analogous  to  those  of  the  oesophagus ;  but  the  real  glandular 


Fig.  263. 


Fig.  264. 


PEPTIC   GASTRIC   GLAND. 

common  trunk;  6,  6,  its  chief  branches; 
c,  c,  terminal  caeca,  with  spheroidal  gland- 
cells. 


PORTIONS  OF  ONE  OF  THE  C^CA  MORE 
HIGHLY  MAGNIFIED,  AS  SEEN  LONGITUDI- 
NALLY (a),  and  in  TRANSVERSE  SECTION 
(B). 

a,  Basement  membrane ;  6,  large  grandular 
cell;  c,  small  epithelial  cells  surrounding 
the  cavity. 


layer  is  only  to  the  right  side.  There  are  foun^  multitudes  of  parallel  tubular 
glands,  united  by  a  small  quantity  of  delicate  connective  tissue  which  is  very 
rich  in  nuclei.  They  secrete  the  gastric  fluid,  or  furnish  the  mucus  that  covers 
the  surface  of  the  epithelium  ;  they  are  consequently  distinguished  as  pepsine 
{or  peptic)  and  mucous  glands,  the  former  being  much  more  numerous  than  the 
latter. 

They  are  composed  of  a  simple  straight  tube  at  their  origin  (excretory  duct), 
which  frequently  divides  into  two  or  more  flexuous  tubes  that  terminate  in 
culs-de-sac  (or  glandular  caca).  The  epithelium  is  not  the  same  in  the  two 
kinds  of   glands  :  the  mucous  glands  (Fig.  265,  a,  h)  are  lined  with  cylinder- 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


epithelium  throughout  their  extent ;  the  peptic  glands  (Figs.  263,  204)  are  lined 
with  cylinder-epithelium  at  their  origin  (Fig.  263,  a),  but  the  secretory  tubes 
contain  round  peptic  cells.  (Each  caeca,  when  highly  magnified,  is  found  to 
consist  of  a  delicate  basement  membrane  (Fig.  265,  a)  inflected  over  a  series 
of  nearly  globular  cells  (b),  which  occupy  almost  the 
whole  cavity  of  the  tube,  and  contain  a  finely  granular 
matter  ;  the  narrow  passage  left  vacant  in  the  centre 
is,  however,  still  surrounded  by  a  layer  of  epithelial  cells 
(c),  the  small  size  of  which  is  in  striking  contrast  to  the 
large  dimensions  of  the  gland-cells.) 

The  muscular  layer  (of  the  mucous  membrane)  is 
immediately  beneath  the  glandular  structure,  and  con- 
tains two  planes  of  intersecting  fibres.  Lastly,  the  con- 
nective tissue  layer  of  the  corium  is  thick  and  loose, 
sustains  the  vessels  (and  nerves),  and  unites  the  mucous 
to  the  muscular  tunic  of  the  stomach. 

4.  Vessels  and  nerves. — The  stomach  receives  its 
blood  by  the  two  branches  of  the  gastric  artery,  the 
sple7iic  and  its  terminal  branch — the  left  epiploic  artery, 
and  by  the  pyloric  and  right  epiploic  arteries.  The 
principal  arterial  ramifications  extend  between  the  mucous 
and  muscular  layers,  where  they  furnish  two  capillary 
reticulations  to  the  glandular  layer — a  deep  network  that 
sun-ounds  the  secretory  tubes,  and  a  superficial  placed 
between  the  alveoli.  The  blood  is  carried  from  the  organ 
to  the  vena  portae  by  the  satellite  venous  branches.  The 
MUCOUS  GASTRIC  GLAND  WITH    lymphatics  form  a  subserous  and  two  deep  networks  at 

CYLINDER   EPITHELIUM.  ,,        i  /■    .1  i        j     i  i  3    ■       .^        n-, 

,     ,  ,  .  the  base  of  the  glandular  layer  and  m  the  fibrous  mem- 

^'  '  *  appendage.' '  ^  ^^^^  brane.  They  enter  small  glands  situated  along  the 
curvatures,  and  from  these  to  Pecquet's  reservoir.  The 
nerves  are  derived  from  the  pneumo-gastrics  and  solar  plexus,  and  in  accompanying 
the  vessels  show  microscopic  ganglia  in  their  course  ;  their  mode  of  termination  is 
not  known. 


Fig.  266. 


APPEARANCE   OF   THE    PROPER   GASTRIC    MEMBRANE   OF   THE   STOMACH   IN   AN   INJECTED 
PREPARATION   (HUMAN). 

A,  From  the  convex  surface  of  the  folds,  or  rugcB ;  B,  from  the  neighbourhood  of  the  pylorus,  where 
the  orifices  of  the  gastric  follicles  occupy  the  interspaces  of  the  deepest  portions  of  the  vascular 
network. 


Functions. — In  the    stomach    is    begun  those  transformations  by  which 
alimentary  matters  are  rendered  capable  of  being  assimilated.     There  the  food 


THE  STOMACH. 


463 


comes  into  contact  with  the  gastric  fluid,  by  the  action  of  which  its  principal 
elements,  and  particularly  the  albuminoid  substances,  become  soluble  and 
absorbable. 


Differential  Characters  in  the  Stomach  of  the  other  Animals. 

The  stomach  is  an  organ   that  exhibits  groat  differences  in  the  various  domesticated 
animals.    In  tlie  study  of  these  differences,  we  will  proceed  from  the  simple  to  the  complex. 

1.  The  Stomach  of  the  Kabbit  (Fig.  286). 
The  stomach  of  the  Rabbit  is  described  immediately  after  that  of  Solipeds,  because  of 
the  great  resemblance  between  the  two  organs.  Like  the  latter,  the  stomach  of  the  Kabbit  is 
divided  into  two  sacs— a  right  and  left— and  the  oesophagus  enters  it  at  the  middle  of  its 
smaller  curvature ;  so  that  the  organ  shows  a  large  tuberosity  in  cul-de-sac  on  the  left  of  the 
cardia.  The  sac  is  perhaps  more  elongated,  narrower,  and  more  curved  than  in  that  of  the 
Horse.     The  total  capacity  of  the  organ  is  from  f  of  a  pint  to  1  pint. 

2.  The  Stomach  of  the  Pig  (Fig.  289). 

The  Pig's  stomach  is  simple,  like  that  of  the  Horse,  but  it  is  less  curved  on  itself,  and 
the  cardia  is  nearer  the  left  extremity ;  the  latter  has  also  a  small  conical  dilatation,  which 
has  been  compared   to  a  cowl   curved   back- 
wards.   The  cesophagua  opens  into  the  stomach  pj^  267 
by  a  wide  infundibulum,  and  the  mucous  mem- 
brane of  that  tube  is  prolonged  over  the  ga>tric 
surface  in  a  laiiius  of  from  two  to  three  inches 
around  the  cardia.    Here  again  we  find  a  "  tiace 
of  the  division   into   two   sacs,"   common   to 
Solipeds,  and  to  nearly  all  Rodents. 

The  capacity  of  the  Pig's  stomach  averages 
from  1|  to  2  gallons.  (The  muscular  tunic  is 
thicker  in  the  right  than  the  left  extremity ; 
near  the  oesophagus,  the  serous  tunic  shows 
some  transverse  folds.) 

3.  The  Stomach  of  Carnivora  (Fig.  267). 
In  the  Dog  and  Cat  the  ventriculus  is 
but  little  curved,  and  is  pear-shaped,  the  small 
extremity  corresponding  to  the  pylorus.  The 
cardia  is  dilated  like  a  funnel,  and  is  nearer 
the  left  extiemity  of  the  organ  than  in  other 
animals.  The  oesophageal  mucous  membrane 
is  not  continued  beyond  the  margin  of  fliat 
orifice.  The  simple  stomach  of  Carnivora  forms 
only  a  single  sac,  whose  internal  mucous  mem- 
brane presents,  throughout  its  whole  extent, 
the  same  organization  as  the  membrane  lining 
the  right  sac  of  Solipeds.  This  membrane  is 
remarkable  for  the  regular  and  undulated  folds 
it  forms  when  the  stomach  is  empty.  Nothing 
is  more  variable  than  tlie  capacity  of  the  Dog's 

stomach,  because  of  the  great  differences  in  the  size  of  this  animal,  according  to  breed.  Colin 
has  found  the  minimum  to  be  1^  pints,  and  the  maximum  If  gallons;  he  calculates  the 
average  to  be  about  2J  quarts.     In  the  Cat,  the  average  is  from  2  to  2i  gills. 

4-  The  Stomach  of  Ruminants  (Fig.  268). 
These  animals  are  distinguished  from  the  others  by  the  faculty  they  possess  of  swallowing 
their  food  after  imperfect  comminution,  and  causing  it  to  return  again  into  the  mouth  to 
submit  it  to  -a  second  mastication,  previous  to  final  deglutition.  The  gastric  apparatus  is 
admirably  arranged  to  effect  this  physiological  finality,  and  is  remarkable  for  its  enormous 
development,  as  well  as  its  division  into  four  separate  pouches,  which  are  regarded  as  so  many 
stomiichs. 


stomach  of  the  dog. 
A,  (Esophagus  ;  B,  pylorus. 


464 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


These  cavities  represent  a  considerable  mass  that  fills  the  greater  part  of  the  abdominal 
cavity,  and  the  medium  capacity  of  which  is  not  less  than  fifty-tive  gallons !  One  of  them, 
the  Rumen,  into  which  the  oesophagus  is  inserted,  constitutes  nine-tenths  of  the  total  mass. 
The  other  three,  the  Reticulum,  Omasum,  and  Ahoruasum,  form  a  short  chain,  continuous  with 
the  left  and  anterior  portion  of  the  rumen.  The  abomasum  alone  should  be  considered  as  a 
true  stomach,  analogous  to  that  of  the  Dog,  or  the  right  sac  of  the  ventriculus  of  Solipeds. 
The  other  three  compartments  only  represent,  like  the  left  sac  in  the  latter  animals,  oesopha- 
geal dilatations. 

The  description  about  to  be  given  of  each  of  these  divisions  more  particularly  applies  te 
the  Ox;  care  will  be  taken,  in  the  proper  place,  to  note  the  special  peculiarities  in  the  stomach 
of  the  Sheep,  Goat,  and  Camel. 

Rumen  (Figs.  2G8,  271).— This  reservoir,  vulgarly  designated  the  paunch,  alone  occupies 
three-fourths  of  the  abdominal  cavity,  in  which  it  affects  a  direction  inclined  from  above  to 
below,  and  from  left  to  right. 

External  conformation. — Elongated  from  before  to  behind,  and  depressed  from  above  to 


Fig.  268. 


OTOMACH   OF   THE   OX,    SEEN   ON    ITS   RIGHT   UPPER   FACE,   THE   ABOMASUM    BEING   DEPRESSED. 

A,  Rumen,  left  hemisphere;  B,  rumen,  right  hemisphere;  C,  termination  of  the  oesophagus; 
D,  reticulum  ;  E,  omasum :  F,  abomasum. 


below,  it  offers  for  study  :  1.  An  inferior  and  a  superior  face,  nearly  plane,  smooth,  and  divided 
into  two  lateral  regions  by  traces  of  fissures,  which  are  only  sensible  at  the  extremities  of  the 
organ.  2.  A  left  and  right  border,  smooth,  thick,  and  rounded.  3.  A  posterior  extremity, 
divided  by  a  deep  notch  into  two  lobes,  described  by  Cliabert  by  the  name  of  conical  cysts.  4. 
An  anterior  extremity,  offering  an  analogous  arrangement,  and  concealed,  at  first  sight,  by  the 
stomachs  (or  compartments)  superadded  to  the  rumen  ;  the  notch  on  the  right  of  this  extremity 
divides  it  into  two  unequal  pouches,  which  will  be  referred  to  presently. 

It  is  to  be  remarked  that  tliese  two  notches,  which  are  prolonged  on  tl)e  surface  by  furrows 
that  separate  these  into  two  lateral  regions,  divide  the  rumen  into  ttoo  sacs— a  rigid  and  left; 
this  division  we  shall  find  more  manifest  in  the  interior  of  the  viscus.  The  right  sac— the 
shortest — is  in  great  part  enveloped  by  the  serous  covering  which  constitutes  the  great  omentum. 
The  left  sac  surpasses  the  other  by  its  two  extremities,  except  in  the  Sheep  and  Goat  (Fig. 
271),  in  which  the  right  conical  cyst  is  longer  than  the  left.  The  anterior  extremity  of  this 
left  sac  is  tlirown  back  on  the  corresponding  lobe  of  the  right  sac ;  above,  it  receives  the 
insertion  of  the  oesophagu.s,  and  is  continuous,  in  front,  with  the  reticulum. 


THE  STOMACH. 


465 


Eelations.— The  external  form  of  the  rumen  being  determinerl,  the  study  of  its  relations 
becomes  easy.  By  its  superior  surface,  it  is  in  contact  with  the  intestinal  mass ;  its  opposite 
face  rests  on  the  inferior  abdominal  wall.  Its  left  border,  supporting  the  spleen,  touches  the 
most  elevated  part  of  the  flank  and  the  sublumbar  region,  to  which  it  adheres  by  cellular 
tissue,  as  well  as  the  vicinity  of  the  coeliac  trunk  and  the  great  mesenteric  artery ;  tlie  right 
border,  margined  by  the  abomasum,  responds  to  the  most  declivitous  portion  of  the  right  hypo- 
chondriac and  flank,  as  well  as  to  the  intestinal  circumvolutions.  Tlie  anterior  extremity, 
bounded  by  the  reticulum  and  omasum,  advances  close  to  the  diaphragm;  the  posterior  occupies 
the  entrance  to  the  pelvic  cavity,  where  it  is  more  or  less  in  contact  with  the  genito-urinary 
organs  lodged  there.  In  the  pregnant  female,  the  uterus  is  prblongeil  forwards  on  the  upper 
face  of  the  viscus  just  described. 

Interior  (Fig.  269). — In  the  interior  of  the  rumen  are  found  incomplete  septa,  which  repeat 
the  division  into  two  sacs  already  so  marked  externally  These  septa  are  two  in  number,  and 
represent  large  muscular  pillars,  which  correspond  inferiorly  to  the  notches  described  at  the 
extremities  of  the  organ.     The  anterior  pillar  (Fig.   269,  g)  sends  to  the  inferior  wall  of 


Fig.  269. 


IKTERIOR  OF   THE   STOMACH    IN   RUMINANTS,   SHOWING   THE   UPPER    PLANE   OF   THE   RUMEN   AND 
RETICULUM,    WITH    THE    (ESOPHAGEAL    FURROW. 

A,  Left  sac  of  the  rumen;  B,  anterior  extremity  of  that  sac  turned  back  on  the  riaiht  sac;  C,  its 
posterior  extremity,  or  left  conical  pouch ;  G,  section  of  the  anterior  pillar  of  the  rumen ;  g,  g,  its 
two  superior  branches;  H,  posterior  pillar  of  the  same;  h,  h,  h,  its  three  inferior  branches;  I, 
cells  of  the  reticulum;  J,  oesophageal  furrow;  K,  oesophagus;  L,  abomasum. 

the  rumen  a  strong  prolongation,  directed  backwards,  and  to  the  left ;  it  is  continued  on  the 
superior  wall  by  two  branches,  which  separate  at  an  acute  angle.  The  posterior  pillar  (Fig. 
269,  h),  more  voluminous  than  the  preceding,  has  three  branches  at  each  of  its  extremities— a 
middle  and  two  lateral.  The  middle  branches  are  carried  forwards  on  the  limit  of  the  two 
sacs,  which  they  separate  from  one  another  ;  that  from  above  meets  the  corresponding  branch 
from  the  anterior  pillar.  The  lateral  branches  diverge  to  the  right  and  left  in  describing  a 
curve,  and  in  circumscribing  the  entrance  to  the  conical  cysts,  which  they  transform  into  two 
compartments  distinct  from  the  middle  portion  of  the  sac  of  the  rumen;  the  inferior  go  to 
meet  the  superior  br-inches,  but  do  not  altogether  join  them. 

The  internal  surf;\ce  of  the  rumen  is  covered  by  a  multitude  of  papillary  prolongations, 
dependencies  of  the  mucous  membrane.  To  the  right,  and  in  the  culs-de-sac,  these  papillae 
are  remarkable  for  their  number,  their  enormous  development,  and  their  general  foliated  shape. 
On  the  left  side  they  are  more  rare,  particularly  on  the  superior  wall,  and  only  form  very 


466  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

small  mammiform  tubercles;  they  are  absent  on  the  muscular  columns.  Tliis  papillary 
arrangement  is  still  more  developed  in  certain  wild  Ruminants,  and  it  is  BCarcely  possible  to 
give  an  idea  of  their  rlclmess  in  the  stomach  of  Gazelles. 

The  interior  of  the  rumen  offers  for  study  two  openings,  situated  at  the  anterior  extremity 
of  the  left  sac :  one  is  the  oesophageal  orifice,  pierced  in  the  superior  wall,  dilated  into  an 
infundibulum,  and  prolonged  into  the  small  curvature  of  the  reticulum  by  a  particular  furrow 
(or  channel),  which  will  be  described  after  tlie  latter  compartment;  the  other,  placed  below, 
and  opposite  the  preceding,  traverses  tlie  bottom  of  the  cul-dv-sac  from  before  to  behind,  and 
forms  the  communication  between  the  paunch  and  reticulum :  it  is  a  very  large  opening,  cir- 
cumscribed below  and  on  the  sides  by  a  septum  or  semilunar  valve,  resulting  from  the  junction 
of  the  parietes  of  the  rumen  with  those  of  the  reticulum. 

Structure. — Like  all  the  hollow  organs  in  the  abdomen,  the  rumen  has  three  tunics:  a 
serous,  a  muscular,  and  a  mucous. 

The  iierous  envelops  the  organ  throughout,  except  above,  in  front,  and  to  the  left,  the  point 
which  touches  the  sublumbar  region,  and  the  pillars  of  the  diapiiragm,  as  well  us  the  bottom 
of  the  notches  which  separate  the  cuh-de-sac  from  the  extremities.  This  membrane  gives 
origin,  like  that  of  the  stomach  of  the  Horse,  to  a  vast  duplicature — the  great  omentum.  The 
arrangement  of  this,  which  is  somewhat  difficult  to  observe  in  the  Ox,  in  consequence  of  the 
enormous  weight  of  the  gastric  mass,  is  readily  seen  in  the  smaller  Ruminants.  It  begins  at 
the  middle  of  the  faces  of  the  paunch  and  the  fissure  intermediate  to  tlie  two  conical  cysts, 
forming  a  wide  envelope  that  contains  the  right  sac  and  the  abomasum  ;  it  becomes  attached  in 
passing  over  the  great  curvature  of  the  last-named  cavity,  and  is  confounded,  superiorly  and 
posteriorly,  with  the  great  mesentery. 

The  muscular  coat  is  very  thick,  and  forms  the  internal  columns  of  the  viscus.  Its  fibres 
are  disposed  in  several  layers,  whose  arrangement  is  simple,  and  offers  nothing  really  interest- 
ing to  study,  except  in  the  points  where  the  serous  tunic  passes  from  one  cul-de-sac  to  another, 
or  from  the  rumen  to  the  reticulum;  there  it  is  often  accompanied  by  thin  and  wide  muscular 
fasciculi  which,  like  the  latter  membrane,  stretch  over  the  intermediate  fissures,  and  thus 
become  real  unitive  or  common  fibres. 

The  muscular  fibres  of  the  rumen  present  an  unmistakable  transverse  striation — a  very 
rare  physical  characteristic  in  the  muscular  tissue  of  organic  life. 

The  mucous  membrane  offers  some  peculiarities,  which  deserve  a  few  words.  The  corium 
is  very  thick,  and  probably  contains  some  glands,  but  they  must  be  extremely  few.  The  free 
face  of  the  membrane  is  excessively  uneven,  in  consequence  of  the  papillary  apparatus  mentioned 
above. 

The  papillae  of  the  rumen  are  foliaceous,  conical,  fungiform.  Those  of  the  first  description 
are  much  more  numerous  than  the  others;  they  have  the  shapeof  an  oval,  elongated  leaf;  their 
summit  is  wide  and  rounded,  and  the  base  narrow  and  apparently  implanted  in  the  corium. 
On  one  face  is  a  little  rib  that  springs  from  the  base  and  disappears  on  the  widened  portion, 
resembling  the  principal  vein  or  nervule  of  a  leaf.  On  the  other  face,  opposite  the  vein,  is  a 
faint  longitudinal  groove. 

These  papillae  are  constituted  by  a  layer  of  nucleated  connective  tissue,  covered  by  epitlie- 
lium;  the  former,  in  the  principal  papillfe,  has  on  its  faces  and  extremities  minute  prolonga- 
tions, resembling  on  a  small  scale  the  secondary  papillae  described  as  existing  on  the  lingual 
mucous  membrane.  In  the  centre  of  the  papillae  are  one  or  two  main  arteries,  derived  from  the 
network  of  the  corium.  These  pass,  in  a  slightly  flexuous  manner,  to  the  summit,  and  break 
lip  into  several  branchlets,  succeeded  by  veins,  that  descend  along  the  surface  of  the  papilla 
into  each  of  its  secondary  prolongations. 

The  conical  and  fungiform  papillae  are  few  in  the  left  sac,  and  resemble  the  papillae  of  the 
same  name  described  on  the  tongue. 

The  epithelium  of  the  mucous  membrane  of  the  rumen  is  remarkable  for  its  strength  and 
cohesiveness.  It  belongs  to  the  category  of  stratified  tesselated  epithelium,  and  forms  a  sheath 
to  each  papilla,  covering  the  corium  in  the  interpapillary  spaces. 

There  are  frequently  found,  in  opening  the  rumen  of  animals  just  killecl,  large  exfoliated 
patches  on  the  surface  of  this  layer.  This  is  a  sufficient  indication  if  the  activity  of  the 
secretion  of  the  epithelium,  and  the  rapidity  of  its  renovation. 

Reticulum  (Honeycomb)  (Figs.  268,  269,  270).  Situation— Form— Relations.— Thia,  the 
smallest  compartment,  is  elongated  from  side  to  side,  slightly  curved  on  itself,  and  placed 
transversely  between  the  posterior  face  of  the  diaphragm,  in  one  direction,  and  the  anterior 
extremity  of  the  left  sac  of  the  rumen  in  the  other ;  the  latter  only  appearing,  externally,  to 
be  a  prolongation,  or  a  diverticulum  of  the  rumen. 

It  has  two  faces,  two  curvatures,  and  two  extremities.     The  anterior  face  adheres  to  the 


THE  STOMACH. 


467 


tendinous  centre  of  the  diaphragm  by  connective  tissue.  The  posterior  face  lies  against  the 
anterior  extremity  of  the  rumen.  The  great  inferior  or  convex  curvature  occupies  the  supra- 
sternal region.  The  lesser,  superior,  or  concave  curvature  partly  corresponds  to  the  lesser 
curvature  of  the  omasum.  The  left  extremity  is  only  separated  from  the  rumen  by  a  fissure, 
which  lodges  the  inferior  artery  of  tlie  reticulum.  The  right  extremity  formp  a  globular 
cul-de-sac,  in  relation  with  the  base  of  the  abomasum. 

Interior  (Figs.  269,  270). — The  internal  surface  of  the  reticulum  is  divided  by  ridges  of 
the  mucous  membrane  into  polyhedral  cells,  which,  in  their  regular  arrangement,  look  like  a 
honeycomb ;  tliey  are  widest  and  deepest  in  the  cul-de-sac,  and  become  gradually  smaller  in 
approaching  the  superior  curvature.  The  interior  of  these  cells  is  divided  into  smaller  spaces, 
included  one  within  the  other,  by  secondary  and  successively  decreasing  septa.  The  principal 
septa  offer  on  their  free  border  a  series  of  conical  prolongations,  with  a  rough  hard  summit ; 
while  their  faces  are  studded  with  minute,  blunt,  or  pointed  papillsB.  The  secondary  septa 
also  show  similar  prolongations ;  and  those  on  their  free  margin  are  even  more  developed  than 
on  the  chief  septa.  Lastly,  from  the 
bottom  of  the  cells  spring  up  a  crowd  of 
long,  conical,  and  very  pointed  papillae, 
resembling  stalagmites  in  their  arrange- 
ment. 

It  maybe  noted  that  the  foreign  bodies 
so  frequently  swallowed  by  Ruminants, 
are  usually  lodged  in  the  reticulum; 
therefore  it  is  that  at  the  bottom  of  the 
cells  are  found  either  small  stones,  at  1 
needles  or  pins — often  fixed  in  the  inte 
mediate  septa — or  nails,  scraps  of  iron,  et.. 
The  interior  of  the  reticulum  communi- 
cates with  the  left  sac  of  the  rumen  by 
the  orifice  already  described,  and  with 
the  omasum  by  a  particular  opening 
placed  near  the  middle  of  the  small  curva- 
ture, though  a  little  more  to  the  right 
than  the  left.  This  opening — eight  or 
ten  times  smaller  than  the  preceding — is 
connected  with  the  infundibulum  of  the 
cardia  by  a  remarkable  groove  (or  chan- 
nel)— the  oesophageal — which  will  be  de- 
scribed separately,  as  it  does  not  properly 
belong  to  the  reticulum. 

Structure. — The  serous  membrane  does  not  cover  all  the  anterior  surface  of  the  organ,  as 
the  latter  adheres  to  the  posterior  face  of  the  diaphragm.  The  muscular  tunic  is  much  thinner 
than  that  of  the  paunch,  and  more  fasciculated.  The  fibres  pass  in  the  same  direction.  The 
corium  of  the  mucous  membrane  sends  a  prolongation  into  each  of  the  septa  of  the  alveoli, 
and  into  each  of  the  conical  papillse  on  tiuse  septa,  or  to  the  bottom  of  these  alveoli.  The 
stratified  pavement  epithelium  is  very  thick,  and  its  horny  layer  is  very  developed  at  the 
summit  of  the  papillae. 

In  tl)e  Camel,  the  reticulum  does  not  form  a  compartment  distinct  from  the  rumen,  and  its 
existence  is  only  indicated  by  some  deep  cells  in  the  anterior  part  of  that  cavity.  The 
entrance  of  the  oesophagus  into  the  rumen  is  oblique  from  left  to  right.  The  oesophageal  furrow 
Ib  limited  by  two  unequal  lips,  the  posterior  being  only  slightly  prominent,  especially  in  its 
middle  portion. 

(Esophageal  Groove  (Figs.  268,  270,  271).— This  furrow  is  so  named  because  it  appears 
to  continue  the  oesophagus  to  the  interior  of  the  stomach.  It  extends  on  the  lesser  curvature  of 
tliC  reticulum  from  the  c.irdia  to  the  entrance  of  the  omasum ;  commencing  in  the  rumen,  it 
belonsrs  to  the  reticulum  for  the  remainder  of  its  extent.  Measuring  from  six  to  eight  inches 
in  length,  this  demi-canal  is  directed  fiom  above  downwards,  and  from  left  to  right,  between 
two  movable  lips,  which  are  fixed  by  their  adherent  border  to  the  superior  wall  of  the  reti- 
culum. These  two  lips  are  thickened  at  their  free  margins,  which  look  downwards  and  to 
the  left.  At  their  origin  at  the  oesophageal  infundibulum,  they  are  thin  and  but  slightly 
elevated;  but  they  become  thick  and  salient  on  arriving  near  the  orifice  of  the  oma.sum,  which 
orifice  they  surround,  though  they  neitlier  meet  nor  become  confounded  with  each  other 

The  mucous  membrane  covering  these  two  lips  is  much  corrugated  outwardly  and  on  the 


ANTERIOR  VIEW  OF  THK  OX'S  STOMACH  (THE  AN- 
TERIOR WALL  OF  THE  RETICULUM  HAS  BEEN 
REMOVED    TO   SHOW    THE    (ESOPHAGEAL   GROOVE). 

A.  (Esophagus ;  B,  left  sac  of  the  rumen ;  C,  right 
sac  ;  D,  reticulum  ;  d',  interior  of  ditto;  E,  omasum  ; 
F,  abomasum ;  x,  oesophageal  groove ;  Y,  its  pos- 
terior lip;  z,  its  anterior  lip;  v,  opening  com- 
municating with  the  reticulum  and  omasum ;  R, 
spleen ;  O,  opening  between  the  rumen  and  reti- 
culum. 


468 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


free  border ;  but  In  the  interior  of  the  groove  it  poasesses  all  the  characters  of  the  oesophageal 
mucous  membrane,  in  being  smooth,  white,  and  ridged  longitudinally ;  near  the  orifice  of  the 
omasum  it  has  some  large  conical  papillae. 

If  this  membrane  be  removed  to  study  the  subjacent  tissue,  the  following  arrangement  is 
observed :  At  the  bottom  of  the  channel,  and  in  the  space  comprised  between  its  two  lips,  are 
transverse  muscular  fibres,  which  belong  to  the  rumen  or  reticulum.  The  lips  themselves  are 
entirely  composed  of  longitudinal  muscular  fasciculi,  particularly  abundant  towards  the  free 
border ;  these  fasciculi  are  mixed  with  the  proper  fibres  of  the  stomach,  towards  the  extremities 
of  the  canal,  and  are  carried  from  one  lip  to  the  other  in  forming  loops  around  the  orifices 
which  communicate  by  this  canal. 

Omasum  (Psalterium,  Many-plies,  Many-leaves,  or  Manyplus.  Figs.  268,  270,  271).— In 
the  Ox,  this  compartment  is  larger  than  the  reticulum,  but  in  the  Sheep  and  G-oat  it  is  smaller, 

Fig.  271. 


stomach  of  the  sheep  (seen  from  the  interior  of  the  omasum). 

O,  (Esophagus;  P,  rumen;  R,  reticulum;  c,  abomasum ;  F,  omasum  opened  at  its  large  curvature, 
the  two  portions  being  reversed  forward  and  backward.  1,  Opening  between  the  rumen  and 
reticulum,  surrounded  by  the  extremity  of  the  lips  of  the  oesophageal  furrow ;  2,  opening  between 
the  omasum  and  abomasum.     i,  Commencement  of  the  small  intestine. 


Situation — Form — Relations. — Situated  above  the  cul-de-sac  of  the  reticulum  and  tha 
anterior  extremity  of  the  right  sac  of  the  rumen,  this  compartment,  when  distended,  has  an 
oval  form,  is  slightly  curved  in  an  opposite  direction  to  the  honeycomb  division,  and  depressed 
from  before  to  behind.  It  has,  therefore,  an  anterior  face,  applied  against  the  diaphragm,  to 
■which  it  is  sometimes  attached  by  connective  tissue ;  a  posterior  face  lying  towards  the  paunch  : 
a  great  curvature,  turned  upwards,  and  fixed  in  the  posterior  fissure  of  tlie  liver  by  an  omental 
frsenum  which  is  continued  on  the  lesser  curvature  of- the  abomasum  and  duodenum;  a  lesser 
curvature,  which  looks  downwards  and  responds  to  the  recticulum  ;  a  left  extremity,  exhibiting 
the  neck,  which  corresponds  to  the  orifice  of  communication  between  the  reticulum  and  omasum ; 


THE  STOMACH.  469 

a  right  extremity,  continuous  with  the  base  of  the  abomasum,  from  wliich  it  is  separated  by 
a  constriction  analogous  to  that  of  the  anterior  extremity,  but  much  less  marked. 

Interior. — This  compartment  shows,  in  its  interior,  the  two  apertures  placed  at  its  extre- 
mities. The  right  orifice,  opening  into  the  abomasum,  is  much  wider  than  the  left,  which 
communicates  with  the  reticulum.  The  cavity  which  these  orifices  bring  into  communication 
with  tlie  adjoining  compartments,  offers  one  of  the  most  curious  arrangements  met  with  in  the 
viscera ;  it  being  filled  by  unequally  developed  leaves  of  mucous  membrane,  which  follow  the 
length  of  the  cavity.  These  leaves  have  an  adherent  border  attached  either  to  the  great 
curvature  or  to  the  faces  of  the  organ,  and  a  free  concave  border  turned  towards  the  lesser 
curvature.  They  commence  at  the  side  of  the  orifice  of  the  reticulum  by  denticulated  ridges, 
between  which  are  furrows,  and  which  are  prolonged  from  the  base  of  the  leaves  to  the  entrance 
of  the  abomasum.  At  the  latter  aperture  they  disappear  altogetlier,  after  rapidly  diminishing 
in  height.  Their  faces  are  studded  by  a  multitude  of  very  hard  mamillary  papillse,  resembling 
grains  of  millet,  which  are  more  developed  and  conical  on  some  of  the  leaves  than  others. 
All  these  lamellar  prolongations  are  far  from  being  of  the  same  extent ;  twelve  to  fifteen  are 
so  wide  that  their  free  border  nearly  reaches  the  lesser  curvature  of  the  viscus,  and  between 
these  principal  leaves  are  others  which,  thoui<h  regularly  enough  arranged,  are  more  or  less 
narrower.    At  first  there  is  remarked  a  secondary  leaf,  half  the  width  of  the  chief  ones, 

Fig.  272. 


it  -     ^  ^       'll 


SECTION   OF   THE   WALL   OF   THE    OMASUM   OF   THE   SHEEP   (FROM   THE   GREAT   CURVATURE, 
SHOWING   THE   ORIGIN   OF   THE   LEAVES). 

P,  peritoneum;  m,  the  two  musular  layers;  e,  epithelium.  I,  1,  Principal  leaves  at  their  origin; 
2,  secondary  leaf;  3,  3,  leaves  of  the  third  order;  4,  denticulated  lamina;  5,  5,  two  planes  of 
muscular  fibres  ascending  into  the  principal  leaves,  some  issuing  from  the  muscular  layer  of  the 


between  which  it  is  placed  ;  then,  on  each  of  its  sides,  another,  one-half  narrower ;  and,  lastly, 
at  the  base  of  these,  two  denticulated  laminae  more  or  less  salient.  In  a  general  way,  the 
leaves  which  are  inserted  into  the  great  curvature  are  tlie  longest  and  widest ;  and  those 
attached  to  the  faces  of  the  viscus  become  shorter  and  narrower  as  they  draw  nearer  the  lesser 
curvature.  The  space  comprised  between  these  prolongations  is  always  filled  by  very 
attenuated  alimentary  matters,  which  are  usually  impregnated  by  a  very  small  quantity  of 
fluid,  but  are  also  often  dry,  and  sometimes  even  hardened  into  compact  flakes. 

Structure. — The  serous  layer  is  a  dependency  of  the  peritoneum,  and  offers  nothing  par- 
ticular; it  does  not  completely  cover  the  anterior  face. 

The  muscular  tunic  is  much  fasciculated,  and  thin.  It  is  formed  by  two  layers  of  fibres 
■which  do  not  pass  in  the  same  direction,  and  dependencies  of  this  tunic  pass  into  the  substance 
of  the  leaves  which  fill  the  cavity  of  this  compartment. 

The  mucous  membrane  is  remarkable  for  the  thickness  of  its  stratified  tesselated  epithelium; 
all  the  leaves  are  formed  by  two  layers  of  this  membrane,  laid  one  against  the  other ;  and 
as  their  structure  is  interesting,  we  will  notice  it. 

The  principal  leaves  are  composed  of  this  duplicature  of  mucous  membrane,  and  two 
layers  of  muscular  fibres  between ;  these  layers  are  opposite  each  other  at  the  commencement 
of  the  leaf,  and  separated  by  a  tr.msverse  vessel;  in  the  remainder  of  their  extent  they  are 
kept  apart  by  the  vessels  that  pass  towards  the  border  of  the  leaf.  Their  fibres  are  detached 
from  the  surface  of  the  muscular  tunic  and,  at  certain  points,  from  its  deep  layer.     In  the 


470 


THE  DIGESTIVE  APPARATUS  IN   MAMMALIA. 


smaller  leaves  there  appears  to  be  only  one  layer  of  muscular  fibres ;  on  all  the  leaves  are 
various-sized  papillae,  the  smallest  of  which  are  like  a  grain  of  millet,  and  have  for  base  a 
mass  of  condenser!  connective  tissue,  the  superficial  fibres  of  which  form  a  kind  of  shell  (Fig. 
273) ;  the  largest  are  club-shaped.  They  receive  blood-vessels,  and  we  have  found  in  the 
connective  tissue  which  constitutes  their  basis,  elements  with  a  somewhat  irregular  outline, 
provided  with  nuclei,  which  we  considered  to  be  nerve-cells  (Fie;.  274). 

The  omasum  in  the  Camel  shows  deep  areolae  instead  of  leaves,  and  the  openijjg  with 
the  abomasum  is  relatively  very  narrow. 

Abomascm  (Reed  or  Renxet.  Figs.  268,  269,  270,  271).  Situation— Form — Relations. — 
The  abomasum  stands  next  to  the  rumen  for  capacity.  It  is  a  pyriform  reservoir,  curved  on 
itself,  elongated  from  before  to  beliind,  and  situated  behind  the  omasum,  above  the  right  sac 
of  the  rumen.  On  the  right  it  touches  the  diaphragm  and  the  hypochondriac ;  on  the  left  it 
is  related  to  the  rumen.  The  greater  curvature,  turned  downwards,  receives  the  insertion  of 
the  great  omentum.  The  lesser  curvature,  inclined  upwards,  gives  attachment  to  the  serous 
band  already  noticed  when  speaking  of  the  great  curvature  of  the  omasum.  Its  base  is  in 
contact  with  the  cul-de-sac  of  the  reticulum,  and  is  separated  from  the  omasum  by  the  con- 
striction in  tlie  form  of  a  thick  neck,  which  corresponds  to  the  communicating  oritice  of  the 
two  stomachs.     Its  point,  directed  upwards  and  backwards,  is  continued  by  the  duodenum. 

Interior. — This  being  the  true  stomach  of  Ruminants,  tlie  mucous  membrane  lining  its 
interior  acquires  all  the  characters  which  distinguish  that  of  the  stomach  of  the  Carnivora, 
or  that  of  the  right  sac  of  the  Horse's  stomach.  It  is  soft,  spongy,  smooth  to  the  touch, 
vascular,  red-coloured,  covered  by  a  thin  epithelium,  and  provided  with  numerous  glands  for 


SECTION   OF   A   LEAF   OF   THE   OMASUM. 

1,  1,  Muscular  planes;  V,  vessel;  2,  epithe- 
lium; 3,  3,  small-sized  papillae,  round  and 
hard. 


LONGITUDINAL  SECTION  OF  A  LARGE  PAPILLA 
FROM  THE  OMASUM,  SHOWING  NERVE-CELM 
IN   ITS   INTERIOR. 


the  secretion  of  the  gastric  juice.  Thinner  than  in  monogastric  animals,  this  tenuity  is  com- 
pensated for  by  a  much  greater  extent  of  surface,  which  is  still  further  increased  by  numerous 
lamellar  folds.  These  latter  are  analogous  in  constitution  to  tliose  of  the  omasum,  cross  in  a 
very  oblique  manner  the  great  axis  of  the  abomasum,  and  altogether  affect  a  kind  of  spiral 
arrangement. 

The  abomasum  has  two  openings :  one,  situated  at  its  base,  opens  into  the  omasum ;  the 
other,  placed  opposite  to  the  first,  and  much  narrower,  is  the  pylorus,  which  is  circumscribed, 
as  in  the  other  animals,  by  a  muscular  ring. 

Structure. — The  serous  membrane  is  continuous  with  the  omenta  tiiat  abut  on  the  great  and 
lesser  curvatures  of  the  viscus.  The  muscular  layer  is  of  the  same  thickness  as  in  the  omasum. 
The  internal  tunic  has  already  been  noticed. 

Functions  of  the  Stomach  in  Ruminants. — We  cannot  pretend  to  give  here  a  complete 
history  of  the  phenomena  of  rumination,  but  must  confine  ourselves  to  describe  in  a  few  words 
what  are  the  principal  attributes  of  each  gastric  dilatation. 

The  rumen  is  a  sac  where  the  aliment  taken  during  feeding-time  is  kept  in  reserve,  and 
whence  it  is  again  carried  into  the  mouth  during  rumination,  after  having  been  more  or  less 
softened. 

The  reticulum  participates  in  the  functions  of  the  rumen,  to  which  it  is  only  a  kind  of 
diverticulum.  But  it  is  particularly  with  regard  to  liquids  that  it  plays  tlie  part  of  a  reservoir ; 
the  solid  sub.stauces  contained  in  it  being  always  diluted  by  a  large  quantity  of  water. 

The  oesophageal  groove  carries  into  the  omasum  the  substances  swallowed  a  second  time 
after  rumination,  or  even  those  which  the  animal  ingests  in  very  small  quantity  for  the  first 
time. 


THE  INTESTINES.  471 

The  omasum  completes  the  trituration  and  attenuation  of  the  food,  by  pressing  it  between 
its  leaves. 

The  abomasum  acts  as  a  true  stomach,  charged  with  the  secretion  of  the  gastric  juice ;  in 
this  reservoir  occur  the  essential  phenomena  of  gastric  digestion. 

Comparison  of  the  Stomach  of  Man  with  that  op  Animals. 

In  its  form,  the  stomach  of  Man  much  resembles  that  of  the  Caruivora. 

The  insertion  of  tlie  oesophagus,  however,  does  not  offer  so  large  an  infundibulum.  The 
organ  is  situated  in  the  left  hypochondriac,  and  is  nearly  horizontal. 

Everywhere  the  mucous  membrane  is  red  and  glandular;  the  muscular  fibres  are  disposed 
in  three  planes,  as  in  Solipeds,  but  the  third  is  found  only  in  the  middle  portion  of  the  stomach, 
two  alone  being  present  towards  the  cardia  and  pylorus;  where  the  stomach  is  largest  the 
contractile  tunic  is  thinnest. 

The  Intestines  (Figs.  275  to  283). 

The  alimentary  canal  is  continued  from  the  stomach,  in  the  abdominal 
cavity,  by  a  long  tube  doubled  on  itself  a  great  number  of  times,  and  which 
terminates  at  the  posterior  opening  of  the  digestive  apparatus.  This  tube  is 
the  intestine.  Narrow  and  uniform  in  diameter  in  its  anterior  portion — which 
is  named  the  small  intestine — it  is  irregularly  dilated  and  sacculated  in  its 
posterior  part — the  large  intestine.  These  two  portions  of  a  whole,  so  markedly 
defined  in  all  the  domesticated  Mammals,  are  but  imperfectly  distinguished 
from  one  another  with  regard  to  the  digestive  phenomena  occurring  in  their 
interior.  We  will  study  them  in  all  the  animals  which  interest  us,  and  conclude 
by  a  general  and  comparative  examination  of  the  entire  abdominal  portion  of 
the  digestive  canal. 

Preparation. — The  study  of  the  intestines  does  not  demand,  properly  speaking,  any  special 
preparation;  it  being  sufficient  to  incise  the  inferior  wall  of  the  abdomen  to  expose  these 
viscera.  As  their  mass,  however,  is  heavy  and  unmanageable,  it  is  advisable  to  expel  their  con- 
tents in  a  manner  similar  to  that  recommended  for  the  preparation  of  the  stomach  :  a  puncture 
at  the  point  of  the  caecum  allows  the  escape  of  the  substances  accumulated  in  that  reservoir; 
those  which  fill  the  large  colon  may  be  removed  by  an  incision  made  towards  the  pelvic  curva- 
ture, and  those  in  the  floating  colon  by  the  rectum.  The  small  intestine  mny  be  evacuated  by 
three  or  four  openings  at  about  equal  distances  in  the  length  of  the  viscus.  Having  done  this, 
inflate  the  intestines  to  somewhat  of  their  natural  volume ;  this  preparation  then  permits  the 
general  arrangement  of  the  intestinal  mass  in  the  interior  of  the  abdomen  to  be  easily  studied. 

It  would  be  well  to  remove  the  entire  mass  altogether  from  the  body,  and  lay  it  out  on  a 
table,  so  as  to  isolate  the  various  parts,  study  them  in  succession,  and  note  their  form. 

In  order  to  study  the  structure  of  a  portion  of  the  intestine,  it  si  ould  be  treated  as  was  the 
stomach — plunged  into  boiling  water  for  a  few  minutes,  then  the  serous  and  mucous  membranes 
removed. 

1.  The  Small  Intestine  (Figs.  282,  283). 

Length — Diameter. — The  small  intestine  is  a  long  tube,  which,  in  a  horse  of 
ordinary  height,  may  average  about  24  yards  in  length,  and  from  1  to  If  inches 
in  diameter.  This  diameter  is  susceptible  of  variation,  according  to  the  state  of 
contraction  of  the  muscular  tunic  of  the  viscus. 

Form. — This  tube  is  cylindrical,  doubled  on  itself,  and  presents  two  cur- 
vatures— one  convex.,  perfectly  free ;  the  other  concave,  named  the  small 
curvature,  which  serves  as  a  point  of  insertion  for  the  mesentery  that  sustains 
the  organ.  Removed  from  the  abdominal  cavity,  freed  from  the  serous  folds 
which  suspend  it,  and  distended  by  air  or  water,  this  disposition  of  the  small 
intestine  naturallv  causes  it  to  twist  in  a  spiral  manner. 


472  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

Course  and  Relations. — The  small  intestine  commences  at  the  right  cul-de-sac 
of  the  stomach,  from  which  it  is  separated  by  the  pyloric  constriction.  At  its 
origin  it  presents  a  dilatation  which,  in  form,  closely  simulates  a  small  stomach, 
the  curvatures  of  which  are  the  inverse  of  those  of  the  proper  stomach.  Placed 
at  the  posterior  face  of  the  liver,  this  expansion,  or  head,  of  the  small  intestine 
begins  the  narrower  portion,  which  at  first  is  directed  forward,  then  bends 
suddenly  backward — thus  forming  a  loop  investing  the  base  of  the  cacum  on 
the  right  side  ;  then  it  is  carried  to  the  left  in  crossing,  transversely,  the  sub- 
lumbar  region,  behind  the.  great  mesenteric  artery  ;  here  it  is  joined  to  the 
origin  of  the  floating  colon  by  a  very  short  serous  frasnum.  It  then  reaches  the 
left  flank,  where  it  is  lodged,  and  where  it  forms  numerous  folds  that  are  freely 
suspended  in  the  abdominal  cavity  among  the  convolutions  of  the  small  colon. 
The  terminal  portion  of  this  conduit,  which  is  easily  recognized  hj  the  greater 
thickness  of  its  walls  and  its  smaller  diameter,  disengages  itself  from  these 
convolutions  to  return  to  the  right,  and  opens  into  the  concavity  of  the  caecum, 
below,  and  a  little  to  the  inside  of,  the  point  where  the  large  colon  has  its 
commencement. 

In  the  language  of  the  schools,  this  terminal  portion  is  named  the  ileum 
(eiXetv,  "  to  twist ")  ;  the  part  which  is  suspended  in  the  left  flank,  and  which  forms 
the  principal  mass  of  the  intestine,  is  designated  the  jejunum  {jejunas,  "  empty  ")  ; 
and  the  curvature  formed  by  this  viscus  at  its  origin,  from  the  pylorus  to  the 
great  mesenteric  artery,  is  termed  the  duodenum  (twelve  fingers'  breadth). 

This  classical  division  is,  however,  altogether  arbitrary,  and  scarcely  deserves 
to  be  retained.  It  would  be  better  to  divide  the  intestine  into  a  Jixed  or 
duode7ial,  a,nd  a.  free  or  Jloating  portion. 

Mode  of  attachment. — The  small  intestine  is  maintained  in  its  position,  at  its 
extremities,  by  the  stomach  and  the  ctecum.  But  its  principal  means  of  fixation 
consists  in  a  vast  peritoneal  fold,  which,  from  its  use,  is  named  the  mesentery 
(jjLeaov,  evrepov,  "  mediate  "  or  "  middle  "). 

This  serous  layer  presents  a  very  narrow  anterior  part  which  sustains  the 
duodenum,  and  fixes  it  in  such  a  manner  as  to  prevent  its  experiencing  any 
considerable  displacement.  Continuous,  in  front,  with  the  gastro-hepatic 
omentum,  this  portion  of  the  mesentery  is  successively  detached  from  the  base 
of  the  liver,  the  inferior  aspect  of  the  right  kidney,  or  even  from  the  external 
contour  of  the  base  of  the  ctecum,  and,  lastly,  from  the  sublumbar  region,  to 
be  soon  confounded  with  the  principal  mesentery.  This  becomes  wider  as  it 
approaches  the  enseal  extremity,  and  arises,  as  from  a  centre,  from  the  outline 
of  the  great  mesenteric  artery,  to  spread  in  every  direction,  and  is  inserted  into 
the  small  curvature  of  the  floating  portion  of  the  viscus.  The  great  length  of 
this  insertion  causes  it  to  become  extended  in  a  spiral  or  screw-like  manner, 
around  its  point  of  origin.  It  may  be  remarked  that  the  terminal  extremity  of 
the  intestine  is  retained  between  the  two  serous  layers  of  the  mesentery,  to  a 
certain  distance  from  its  free  border.  This  peritoneal  fold  consequently  forms 
at  this  point— at  the  side  opposite  to  its  insertion  into  the  intestinal  tube — a 
particular  fr^enum,  which  is  observed  to  be  carried  to  the  anterior  face  of  the 
caecum. 

Interior.— The  interior  of  the  small  intestine  shows  longitudinal  folds,  which 
are  effaced  by  distension,  except  towards  the  origin  of  the  duodenal  portion^ 
Those  met  with  in  this  situation  possess  all  the  characters  of  the  ralvulce 
connivenfes  {valves  of  Kerkring)  in  Man  ;  they  resist  traction  on  the  intestinal 


THE  INTESTINES.  473 

membranes,  and  are  formed  by  two  mucous  layers  laid  together,  with  a  plentiful 
supply  of  connective  tissue  between  them. 

The  internal  surface  of  the  small  intestine  also  oflfers  for  study  a  multitude  of 
villosities  and  glandular  orifices,  or  follicles,  which  will  be  noticed  hereafter.  It 
communicates  with  the  inner  surface  of  the  stomach  by  the  pyloric  orifice,  and 
with  that  of  the  caecum  by  means  of  an  opening  which  projects  into  the  interior 
of  that  reservoir,  like  a  tap  into  a  barrel.  This  projection,  which  is  not  very 
marked,  is  formed  by  a  circular  mucous  fold,  strengthened  externally  by  muscular 
fibres,  and  is  named  the  ilio-cmal  valve  or  valvula  Bauhini.  Two  additional 
orifices  open  on  the  surface  of  the  small  intestine  in  its  duodenal  portion,  from  5 
to  8  inches  from  the  pylorus  :  one  is  the  orifice  common  to  the  biliary  and 
principal  pancreatic  duct,  the  other  that  of  the  accessory  pancreatic  duct. 

Stkucture. — The  wall  of  the  small  intestine,  like  that  of  the  other  hollow 
viscera  in  the  abdominal  cavity,  is  composed  of  three  tunics  : — 

1.  Scrolls  membrane. — This  envelops  the  organ  everywhere,  except  at  its 
small  curvature,  which  receives  the  insertion  of  the  mesentery ;  it  adheres 
closely  to  its  surfaces  and  the  great  curvature. 

2.  JIuscular  membrane. — Covered  internally  by  a  layer  of  condensed  connec- 
tive tissue  (which  is  sometimes  considered  a  fourth  tunic),  this  middle  membrane 
has  two  planes  of  fibres — one,  superficial,  is  formed  of  longitudinal  fibres 
uniformly  spread  over  the  whole  sui-face  of  the  viscus  ;  the  other,  deep,  is 
composed  of  circular  fibres,  which  are  a  continuation  of  those  of  the  pyloric 
ring. 

3.  3Iucous  membrane. — This  tunic,  extremely  interesting  to  study,  is  soft, 
spongy,  highly  vascular,  very  dehcate,  and  of  a  reddish-yellow  colour.  Its 
external  face  is  loosely  adherent  to  the  muscular  membrane,  and  its  free  face 
exhibits  the  villi,  and  the  glandular  or  follicular  orifices  already  noticed. 

It  comprises,  in  its  structure,  an  epithelial  lining,  and  a  mucous  dermis  or 
corium. 

The  epithelial  layer  is  formed  of  a  single  row  of  spheroidal  cells,  implanted, 
by  their  summit,  which  is  often  ramifying,  in  the  surface  of  the  dermis,  and 
lining  the  interior  of  the  orifices  which  open  on  the  inner  face  of  the  membrane. 
The  base  of  these  cells  has  an  amorphous  cushion,  which,  when  they  are  all 
united,  appears  like  a  thin  layer  spread  on  the  inner  surface  of  the  intestine. 
Their  protoplasm  is  frequently  fenestrated  or  reticulated  (Renaut)  ;  and  among 
the  ordinary  spheroidal  cells,  some  calyciform  cells  are  met  with  here  and  there. 

The  mucous  dermis  is  thick  and  loose  in  its  deeper  portion,  and  is  constituted 
by  fasciculi  of  connective  tissue,  mixed  with  elastic  fibres,  and  lymphoid  elements. 
On  its  free  surface  it  exhibits  projections  [villosities)  and  depressions  (follicles), 
which  correspond  to  the  glands.  It  has  a  muscular  layer,  the  unstriped  fibres  of 
which  are  arranged  in  a  similar  manner  to  those  of  the  muscular  coat  of  the 
intestine.  Lastly,  it  contains  follicles,  and  vascular  and  nervous  networks.  "We 
will  study  each  of  these. 

The  villi  are  the  foliated  or  conical  appendages,  which  are  found  to  be 
most  developed  in  the  shortest  portion  of  the  intestine.  In  Birds  and  the 
Carnivora  they  attain  their  maximum  length  ;  while  in  Ruminants  they  are  in  a 
rudimentary  state,  though,  whatever  may  be  their  dimensions,  they  are  always 
visible  to  the  naked  eye.  Their  number  is  considerable,  and  they  have  been 
justly  compared  to  the  pile  of  velvet.  In  structure,  they  are  each  formed  by  a  small 
mass  of  connective  tissue,  in  the  centre  of  which  is  a  chyliferous  vessel  or  several 


^4 


TEE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


vessels,  with  a  magnificent  network  of   peripheral  capillary  blood-vessels ;   the 
whole  being  enclosed  in  a  complete  epithelial  sheath. 

Fig.  275. 


A.   VILLI   OF   MAN,    SHOWING   THE   BLOOD-VESSELS    AND   LACTEALS.      B.    VILLUS   OF   A    SHEEP. 


Fig.  276. 


The  orifices  opening  on  the  intestinal  mucous  membrane  belong  either  to 
Brunner's  (duodenal)  glands,  or  to  those  of  Leiberkiihn  (simple  foil  ides). 

Brunner's  glands  form  a  continuous  layer 
beneath  the  duodenal  mucous  membrane. 
They  are  tubular  glands,  ramifying  and 
fiexuous,  which  open  on  the  surface  of  the 
mucous  membrane,  either  by  a  special  ex- 
cretory canal,  or  through  the  medium  of  a 
Lieberkiihn's  gland.  (These  glands  secrete 
a  clear  alkaline  mucus,  which  contains  no 
formed  elements,  such  as  cells  or  nuclei.) 

The  glands  {cryptce  mucosa')  of  Lieher- 
kiihn  or  Galeati  are  placed  in  the  substance 
of  the  mucous  membrane,  and  are  distin- 
guished by  their  microscopical  dimensions, 
their  considerable  number,  and  their  tubular 
form,  which  has  caused  each  of  them  to  be 
compared  to  the  finger  of  a  glove ;  they 
are  implanted  perpendicularly  in  the  mem- 
brane, and  open  on  its  free  surface.  They  are  found  throughout  the  whole  extent 
of  the  intestine,  and  are  lined  with  spheroidal  epitheUum. 

The  solitary  glands  or  follicles  (glandulm  solitarice,  or  lenticular  glands)  are 


PORTION  OF  ONE  OF  BRUNNER  S  GLANDS. 


THE  INTESTINES. 


475 


round,  salient  bodies,  visible  to  the  naked  eye.  They  are  somewhat  rare  in  the 
small  intestine,  but  are  more  abundant  at  the  posterior  portion  of  the  large 
intestine.  They  are  formed  by  a  mass  of  lymphoid  elements,  enveloped  in  some 
condensed  fasciculi  of  connective  tissue.  Around  them  the  mucous  membrane  is 
slightly  umbilicated,  and  is  destitute  of  villa  and  tubular  glands,  though  these 
are  arranged  in  a  circle  around  the  follicles,  to  form  the  coronce  tubulorum.  (The 
solitary  glands  usually  contain  a  cream-Uke  secretion,  which  covers  the  villi  on 
their  free  surface.) 

The  aggregated  follicles  (glandulce  agminatce)  are  nothing  more  than  solitary 
glands  collected  together  in  a  limited  space,  where  they  constitute  what  are 

Fig.  277. 


PERPENDICULAR   SECTION   THROUGH   ONE   OF    PEYER'S   PATCHES   IN   THE   LOWER   PART   OF   THE 
ILEUM   OF    THE    SHEEP. 

a,  a,  Lacteal  vessels  in  the  villi ;  h,  b,  superficial  layer  of  the  lacteal  vessels  (rete  angustum) ;  c,  e, 
deep  layer  of  the  lacteals  {rete  amplum);  d,  d,  efferent  vessels  provided  with  valves;  e,  Lieber- 
kiihn's  glands ;  /,  Peyer's  glands ;  g,  circular  muscular  layer  of  the  wall  of  intestine ;  h,  longi- 
tudinal layer ;  i,  peritoneal  layer. 

known  as  the  glands  of  Pei/er  or  of  PecMin,  Peyer's  patches,  or  the  honeycomb 
glands.  Absent  in  the  duodenum,  and  even  at  the  commencement  of  the  jejunum, 
these  glands  are  about  a  hundred  in  number,  and  are  very  irregularly  placed  on 
the  internal  surface  of  the  intestine  at  its  great  curvature,  on  the  side  opposite  to 
the  mesentery.  Their  form  is  oval  or  circular,  and  the  smallest  scarcely  measure 
more  than  some  few  hundredths  of  an  inch  square,  while  the  diameter  of  the 
largest  increases  to  1|  inch. 

(Each  of  these  patches  is  composed  of  a  group  of  small,  round,  whitish 
vesicles,  covered  with  mucous  membrane  ;  these  vesicles  consist  of  a  moderately 
thick  external  capsule,  having  no  excretory  canal,  and  containing  a  similar 
secretion  to  that  in  the  solitary  follicles.  They  are  surrounded  by  a  zone  or 
band  of  simple  follicles,  and  the  spaces  between  them  are  covered  with  villi. 


476 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


The  vesicles  are  usually  closed  ;  though  it  is  supposed  they  open  at  intervals  to 
discharge  their  secretion.  The  mucous  and  submucous  coats  of  the  intestine 
are  intimately  adherent  and  highly  vascular,  opposite  the  Peyerian  glands.) 


Fig.  278. 


Fig.  279. 


PERPENDICULAR   SECTION   THROUGH   THE   INTESTINAL    WALL   TO   SHOW   A   SOLITARY    FOLLICLE. 

a,  Lieberkiihnian  glands;  6,  solitary  follicle;  c,  lacteal  vessels  surroundiag,  but  not  penetrating, 
the  follicles ;  d,  large  efferent  vessels,  provided  with  valves. 

4.  Vessels  and  nerves. — The  small  intestine  receives  its  arteries  almost  ex- 
clusively from  the  great  mesenteric  artery.  One,  which  goes  to  the  duodenum, 
comes  from  the  coehac  trunk.  These  arteries  form  a  submucous  network,  from 
which  branches  pass  inwards  and  outwards,  the  first  to 
the  muscular  and  serous  tunics,  the  second  to  the  glands 
and  the  villi.  A  tubular  network  surrounds  each 
Lieberkiihnian  gland,  and  is  observed  in  each  villus  ; 
while  a  spherical  reticulation  surrounds  each  solitary 
follicle,  loops  being  given  off  which  penetrate  nearly  to 
the  centre  of  the  follicle. 

The  veins  have  the  same  arrangement,  and  finally 
enter  the  vena  portse. 

The  lymphatics  constitute  three  superposed  networks 
in  the  mucous  membrane.  The  first  is  situated  around 
the  glandular  orifices  ;  it  receives  the  central  lacteal  from 
each  villus  ;  the  second  is  placed  between  the  glandular 
and  the  muscular  layer  of  the  mucous  membrane  ;  the 
third  lies  in  the  deep  portion  of  the  membrane,  and 
communicates  with  the  meshes  encircling  the  solitary 
glands.  The  largest  emergent  vessels  from  these  three 
networks  pass  through  the  wall  of  the  intestine,  accom- 
panying the  blood-vessels  between  the  layers  of  the  mesentery,  enter  the  mesenteric 
glands,  and  terminate  in  the  reservoir  of  Pecquet  {receptaculum  chyli).  There 
is  another  lymphatic  network  in  the  muscular  tunic  of  the  intestine. 


'"^miiim 


VILLI  OF  INTESTINE,  WITH 
THEIR  CAPILLARY  PLEXUS 
INJECTED. 


THE  INTESTINES. 


477 


The  nerves  are  from  the  solar  plexus ;  they  form  a  submucous  plexus 
(Meissner's  plexus)  and  a  mtjenteric  plexus  {Auerbach's  plexus),  comi^vmed  between 
the  two  planes  of  jhe  muscular  tunic. 

Numerous  microscopic  ganglia  are  found  on  the  course  of  these  plexuses. 

Development. — The  small  intestine  appears  at  an  early  period  in  the  foetus, 
and  during  the  foetal  existence  of  Ruminants  preserves  a  very  remarkable 
predominance  over  the  large  intestine — a  predominance  equally  marked  in  the 
vessels  it  receives  ;  for  in  a  foetus  of  five  months,  we  have  found  the  collective 
arteries  of  the  small  intestine  equivalent  to  about  ten  times  the  volume  of  those 
of  the  caecum  and  colon. 

Functions. — It  is  in  the  small  intestine — under  the  influence  of  the  hepatic, 
pancreatic,  and  intestinal  secretions — that  are  carried  on  those  transformations 


Fig.  280. 


Fig.  281. 


HORIZONTAL  SECTION  THROUGH  THE  MIDDr.E  PLANE  OP 
THREE  PEYERIAN  GLANDS,  SHOV?ING  THE  DISTRIBU- 
TION   OF    THE    BLOOD-VESSELS    IN   THEIR    INTERIOR. 


DIAGRAMMATIC  REPRESENTA- 
TION OF  THE  ORIGIN  OF  THE 
LACTEALS   IN    A   VILLUS. 

e,  Ceutral  lacteal ;  d,  connec- 
tive-tissue corpuscles  with 
communicating  branches; 
c,  ciliated  columnar  epithe- 
lial cells,  the  attached  ex- 
tremitins  of  which  are  di- 
rectly contiguous  with  the 
connective  tissue  corpuscles. 


that  constitute  the  digestive  function.  It  is  also  in  this  intestine  that  the 
absorption  of  the  nutritive  prmciples  and  fluids  commences,  and  in  which  the 
villi  are  the  essential  organs. 

2.  The  Laege  Intestine. 

The  large  intestine  commences  by  a  vast  reservoir  in  the  form  of  a  cul-de-sac^ 
named  the  cmcum.  It  is  continued  by  the  colon,  the  posterior  extremity  of  which 
is  succeeded  by  the  rectum.  It  is  separated  from  the  small  intestine  by  the  ileo- 
cecal valve. 

A.  C^cuM  (C^cuM  Caput  Coli)  (Figs.  282,  283). 

Situation — Direction. — This  is  a  very  wide  and  elongated  sac,  occupying  the 
right  hypochondriac,  where  it  affects  an  oblique  direction  downwards  and  back- 
wards. 

33 


478  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

Dimensions — Capacity. — Its  length  is  ordinarily  a  little  over  three  feet,  and  it 
will  contain,  on  an  average,  about  7^  gallons  of  fluid. 

For)72 — External  surface. — The  elongated  sac  formed  by  the  cfecum  is  conical 
in  shape,  terminating  in  a  point  inferiorly,  and  bulging  and  curved  like  a  crook 
superiorly.  Externally,  it  exhibits  a  great  number  of  cii'cular  furrows,  interrupted 
by  longitudinal  muscular  bands,  four  of  which  are  observed  in  the  middle  portion 
of  the  organ  ;  they  disappear  towards  its  extremities.  The  bottom  of  these 
furrows  necessarily  corresponds  to  the  internal  ridges,  and  these  can  be  made  to 
disappear  by  destroying  the  longitudinal  bands,  which  considerably  lengthens  the 
caecum  ;  thus  showing  that  these  transverse  puckerings  are  due  to  the  presence  of 
the  riband-like  cords,  and  have  for  their  object  the  shortening  of  the  intestine 
without  diminishing  the  extent  of  its  surface. 

Relations. — To  study  its  relations,  the  caecum  is  divided  into  three  regions  : — 

1.  The  superior  extremity.,  base,  arch,  or  still  better,  the  crook,  shows  in  the 
concavity  of  its  curvature,  wliich  is  turned  forwards,  the  insertion  of  the  small 
intestine  and  origin  of  the  colon.  Placed  in  the  sublumbar  region,  it  is  related, 
superiorly,  to  the  right  kidney  and  the  pancreas,  through  the  medium  of  an. 
abundant  supply  of  connective  tissue.  Outwardly,  it  touches  the  parietes  of  the 
right  flank,  and  is  encircled  by  the  duodenum.  On  the  inner  side,  it  adheres  by 
connective  tissue  to  the  termination  of  the  large  colon,  and  is  in  contact  with  the 
convolutions  of  the  small  intestine. 

2.  The  middle  portion  is  in  contact,  inwardly,  with  the  same  convolutions  and 
the  large  colon  ;  outwardly,  with  the  cartilages  of  the  false  ribs,  in  following  their 
curvature. 

3.  The  inferior  extremity,  ox  point,  usually  rests  on  the  abdominal  prolongation 
of  the  sternum  ;  but  as  it  is  free  and  can  move  about  in  every  direction,  it  often 
happens  that  it  is  displaced  from  this  situation. 

Mode  of  attachment. — The  cfecum  is  fixed  to  the  sublumbar  region  and  the 
terminal  extremity  .of  the  large  colon,  by  a  wide  adherent  surface.  All  around 
this  surface,  the  peritoneum^which  constitutes  the  serous  covering  of  the  caecum — 
is  gathered  into  folds,  and  in  passing  from  the  caecum  to  the  origin  of  the  colon, 
this  membrane  forms  a  particular  short  and  narrow  frsnum,  designated  the 
meso-ccecum. 

Interior. — Viewed  internally,  the  caecum  offers  for  study  the  mhndce,  or 
transverse  ridges  corresponding  to  the  external  furrows.  "We  have  already  seen 
that  these  are  due  to  simple  circular  folds,  comprising  in  their  thickness  the 
three  tunics  of  the  organ,  and  that  they  can  be  effaced  by  distension,  to  reappear 
afterwards  in  varying  number  and  position— differing  widely,  in  this  respect, 
from  the  valvules  conniventes  of  the  small  intestine. 

Two  orifices,  placed  one  above  the  other,  open  on  the  internal  surface  of  the 
caecum,  at  the  point  corresponding  to  the  concavity  of  the  crook.  The  most 
inferior  represents  the  terminal  opening  of  the  small  intestine  at  the  centre  of 
the  ilio-ccBcal  valve,  the  presence  of  which  in  the  domesticated  animals  has,  in 
consequence  of  a  wrong  appreciation  of  analogies,  been  denied  ;  it  is  nothing 
more  than  the  projection  described  as  being  made  by  the  terminal  portion  of  the 
small  intestine.  The  second  opening,  placed  about  1|  or  2  inches  above  the 
preceding,  and  puckered  around  its  margin,  establishes  a  communication  between 
this  viscns  and  the  colon.  If  this  opening  be  compared  with  the  capacity  of  the 
canal  that  begins  from  it,  it  will  be  remarked  that  it  could  scarcely  be  narrower. 

Structure. — The  serous  tunic  does  not  call  for  any  notice,  beyond  that 


THE  INTESTINES. 


479 


already  given  when  speaking  of  the  attachments  proper  to  the  cgecum.  The 
muscular  tunic  is  formed  of  circular  fibres,  crossed  externally  by  longitudinal 
bands,  which  maintain  the  organ  in  transverse  folds.  The  mucous  membrane  is 
thicker  than  that  of  the  small  intestine,  and  is  also  distinguished  from  it  by  the 
absence  of  the  Brumierian  and  agminated  glands.  It  has,  however,  the  solitary 
follicles  and  crypts  of  Lieherkiikn,  as  well  as  some  few  intestinal  villi.  The  blood- 
vessels are  the  ccecal  arteries  and  veins.  The  lymphatics  pass  to  the  sublumbar 
receptacle  ;  the  nerves  are  derived  from  the  great  mesenteric  plexus. 

Functions. — The  csecum  serves  as  a  reservoir  for  the  enormous  quantities  of 
fluid  ingested  by  herbivorous  animals.    The  greater  part  of  this  fluid  in  its  rapid 

Fig.  282. 


GENERAL  V/EW  OF  THE  INTESTINES  OF  THE  HORSE  (SEEN  FROM  THE  RIGHT  SIDE,  WITH  THE 
PELVIC  FLEXURE  AND  A  PORTION  OF  THE  SMALL  INTESTINE  CARRIED  BEYOND  THE 
ABDOMINAL   CAVITY). 

a,  CEsophagu'j;  6,  right  sac  of  the  stomach;  c,  small  intestine,  showing  its  origin  or  duodenal  por- 
tion, encircling  the  base  of  the  caecum  ;  d,  caecum ;  e,  origin  of  the  large  colon ;  /,  first  portion 
of  the  large  colon ;  g.  supra-sternal  flexure  ;  h,  second  portion  of  the  large  colon  ;  i,  pelvic  flexure; 
j,  third  portion  of  the  large  colon;  k,  diaphragmatic  flexure;  I,  fourth  portion  of  the  large  colon; 
m,  termination  of  the  free  colon;  n,  rectum;  o,  mesentery  proper;  p,  colic  mesentery  (meso- 
colon) ;  q,  anus ;  r,  internal  inguinal  ring ;  s,  spermatic  vessels ;  t,  deferent  canal ;  u,  bladder ;  v, 
vesiculse  seminales;  x,  pelvic  enlargement  of  the  vas  deferens;  y,  prostate;  z,  suspensory 
ligament  of  the  penis. 


pastage  through  the  stomach  and  small  intestine,  escapes  the  absorbent  action 
of  the  villi  and  accumulates  in  the  Cfecum,  into  which  it  may  be  said  to  wash 
the  alimentary  mass  it  comes  in  contact  with  ;  it  thus  dissolves  the  soluble 
and  assimilable  matters  this  mass  may  yet  contain,  and  so  favours  their  entrance 
into  the  circulation,  through  the  immense  absorbing  surface  formed  by  the 
mucous  membrane  of  the  large  intestine. 

The  aliment  undergoes  still  further  change,  and  digestion  is  completed  in 
this  viscus,  principally  in  the  Herbivora. 

B.  Colon. 
The  colon  is  divided  into  two  portions,  which  differ  from  each  other  in 


480 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


volume,  and  in  the  disposition  they  affect  in  the  abdominal  cavity.     The  first 
is  the  lame  or  double  colon;  the  second,  the  small,  single,  ov floating  colon. 


A,  The  duodenum  as  it  passes 
behind  the  great  mesen- 
teric artery ;  B,  free  por- 
ti'in  of  the  small  intes- 
tine; C,  ileo-cascal  portion ; 
D,  caecum ;  E,  F,  G,  loop 
formed  by  the  large  colon; 
G,  pelvic  flexure ;  f,  f, 
point  where  the  colic  loop 
is  doubled  to  constitute 
the  supra-sternal  and  dia- 
phragmatic flexures;  1, 
posterior  aorta;  2,  2, 
arteries  to  the  small  in- 
testines ,  3,  ileo-cascal 
artery;  4,  superior  csecal 
artery;  5,  inferior  csecal 
artery ;  6,  artery  of  the 
arch  of  the  csecum ;  7, 
right  colic  artery ,  8,  left 
or  retrograde  colic  artery  ; 
9,  first  artery  of  the  single 
colon. 


GEKERAL    VIEW   OF   THE    HORSE's    INTESTINES    (THE    ANIMAL   IS   PLACED   ON    ITS   BACK,   AND  THE 
INTESTINAL   MASS  SPREAD   OUT). 


THB  INTESTINES.  48i 

The  Laege  or  Double  Colon  (Figs.  282,  283,  284). — This  intestine  begins 
at  the  caecum,  and  terminates  by  suddenly  contracting  at  the  origin  of  the  small 
colon. 

Length — Capacity. — It  is  from  about  10  to  13  feet  in  length,  and  has  a 
medium  capacity  equal  to  18  gallons. 

Form — General  arrangement. — Removed  from  the  abdominal  cavity,  and 
extended  on  a  table  or  on  the  ground,  this  portion  of  the  intestine  appears  as 
a  voluminous  canal,  offering  a  succession  of  dilatations  and  contractions  ;  its 
surface  being  traversed  by  longitudinal  bands,  and  sacculated  and  furrowed 
transversely  for  a  great  part  of  its  extent,  exactly  like  the  caecum.  It  is  also 
doubled  in  such  a  manner  as  to  form  a  loop,  the  two  branches  of  which  are  of 
equal  length,  and  are  held  together  by  the  peritoneum,  which  is  carried  from 

Fig.  284. 


THE   COLON  OF   THE   HORSE. 

1,  First  portion  ascending  to  form  the  supra-sternal  flexure ;  2,  second  portion  descending  to  form 
the  pelvic  flexure,  7  ;  3,  6,  longitudinal  muscular  bands;  4,  point  of  the  caecum,  5;  8,  duodenum; 
9,  small  intestine. 

one  to  the  other ;  so  that  the  terminal  extremity  of  the  large  colon  returns 
towards  the  point  of  its  origin. 

But  this  colic  flexure,  owing  to  its  length,  could  not  be  contained  m  the 
abdomen  ;  and  it  is  therefore  doubled  in  its  turn  from  above  to  below,  and  from 
right  to  left  (at  the  points  f,  f,  in  Fig.  283),  forming  curvatures  which  will  be 
noticed  presently.  From  this  circumstance,  it  results  that  the  large  colon, 
studied  in  the  abdominal  cavity,  is  divided  into  four  portions  lying  beside  each 
other  in  pairs  ;  so  that  a  transverse  section  of  that  cavity,  made  in  front  of  the 
base  of  the  csecum,  would  give  for  this  intestine  the  results  indicated  in  Fig.  285. 

Course  and  Relations. — In  following  the  course  of  the  large  colon  from  its 
origin  to  its  termination,  in  order  to  study  its  four  portions  in  their  normal 
relations,  the  following  is  observed  : — 

Commencing  from  the  arch  or  crook  of  the  caecum,  the  colon  is  directed 
forwards,  above  the  middle  portion  of  that  reservoir,  which  it  follows  to  its  point. 
Arrived  at  the  posterior  face  of  the  diaphragm  at  its  most  declivitous  part,  it  bends 
downwards  and  to  the  left,  forming  its  first  sternal  ox  supra-sternal  flexure,  because 


482  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA 

it  rests  on  the  xiphoid  cartilage  of  the  sternum  (Fig.  282,  g).  Here  begins  the 
second  portion  of  the  viscus,  which  is  in  immediate  contact  with  the  inferior 
abdominal  wall,  and  extends  backwards  into  the  pelvic  cavity,  where  it  is 
inflected  to  the  left  to  constitute  the  sigmoid  or  pelvic  flexure.  This  curvature — 
the  centre  of  the  colic  loop — is  in  relation  with  the  rectum  and  bladder,  as  well 
as  with  the  deferent  canals,  or  the  uterus  and  ovaries,  according  to  the  sex.  It  is 
succeeded  bj  the  third  portion  of  the  colon,  which  is  carried  forward,  above,  and 
to  the  left  of  the  preceding.  Bound  to  the  second  division  by  peritoneum  and  con- 
nective tissue,  this  new  section  reaches  the  tendinous  centre  of  the  diaphragm,  and 
is  then  doubled  upwards  and  to  the  right.  The  flexure  arising  from  this  third 
duplicature  is  called  the  diaphragmatic,  because  of  its  relations  with  the  musculo- 
aponeurotic  membrane  that  partitions  the  great  cavity  of  the  trunk,  or  the  gastro- 
kepatic  curvature,  in  consequence  of  its  lying  equally 
Fig.  285.  against  the  liver  and  stomach  (it  is  also  designated  the 

sigmoid  flexure)  (Fig.  282,  k).  To  this  flexure  succeeds 
the  fourth  and  last  portion  of  the  large  colon,  bound  to 
the  first  portion,  as  the  second  is  to  the  third.  This 
extends,  posteriorly,  to  the  base  of  the  caecum,  where  it 
terminates  in  a  sudden  contraction,  and  is  continued  by 
the  small  colon  ;  it  occupies  the  sublumbar  region,  and, 
through  the  medium  of  connective  tissue,  is  applied 
against  the  inferior  face  of  the  pancreas  and  the  inner 
PLAN  OF  THE  COLON.         sidc  01  thc  c^cal  arcn. 

Mode  of  attachment. — The  large  colon  can  be  easily 
displaced  in  the  abdominal  cavity.  It  is  nevertheless  fixed  :  1 .  By  its  origin,  to 
the  cfficum  and  to  the  serous  frsenum  which  attaches  it  to  that  receptacle.  2. 
By  the  adherence  of  its  terminal  portion  to  the  pancreas  and  arch  of  the  caecum. 
8.  By  the  meso-colon.  The  latter  ligament  forms,  in  the  concavity  of  the  pelvic 
flexure,  a  kind  of  racket,  the  handle  of  which  is  prolonged  to  a  short  distance 
between  the  two  branches  of  the  colic  flexure.  Beyond  this,  these  two  branches 
are  directly  placed  side  by  side. 

External  surface. — "We  have  seen  that  the  large  colon  does  not  offer  the  same 
diameter  everywhere,  and  that  it  is  sacculated,  plicated,  and  traversed  by  longi- 
tudinal bands  ;  it  is,  however,  important  to  study  in  detail  this  disposition  of  its 
external  surface  in  each  of  the  regions  already  named. 

At  its  origin,  the  large  colon  is  extremely  narrow,  and  scarcely  equal  to  the 
small  intestine.  But  it  soon  dilates  and  assumes  a  considerable  volume,  which 
it  preserves  beyond  the  pelvic  flexure.  It  then  becomes  progressively  constricted 
to  the  middle  of  its  third  portion,  where  the  diameter,  reduced  to  its  minimum, 
is  yet  much  greater  than  at  the  origin  of  the  first  portion.  Near  the  diaphragmatic 
flexure,  it  is  again  gradually  dilated,  and  finishes  by  acquiring,  near  its 
termination,  the  greatest  volume  it  has  yet  exhibited.  The  muscular  bands 
which  maintain  its  transverse  folds  throughout  the  whole  extent  of  its  first 
dilated  portion,  are  four  in  number.  Three  disappear  in  arriving  towards  the 
pelvic  curvature,  and  the  only  one  remaining  is  that  which  is  placed  in  the 
concavity  of  that  curvature.     At  the  second  dilatation  there  are  three  bands, 

'  "We  have,  in  some  instances,  found  the  large  colon  doubled  on  itself  in  an  inverse  sense— 
the  second  and  third  portions  being  placed  above  and  in  front  of  the  first  and  fourth,  with  the 
pelvic  flexure  touching  the  sublumbar  region,  in  front  of  the  caecum,  and  the  point  of  the  latter 
directed  back  towards  the  pelvis. 


THE  INTESTINES.  483 

two  of  which  are  prolonged  to  the  floating  colon.  The  transverse  folds  formed 
by  these  flat  bands  are  but  faintly  marked  towards  the  pelvic  curvature,  and  are 
altogether  absent  in  the  narrow  portion  succeeding  it ;  it  is  only  in  the  whole 
extent  of  the  first  dilatation  that  they  are  deepest  and  most  numerous. 

Liternal  surface. — This  is  exactly  like  that  of  the  caecum. 

Structure. — The  serous  membrane  envelops  the  whole  of  the  colon,  except  in 
those  places  where  it  comes  in  contact  with  itself  or  with  other  viscera.  So  it 
iiappens  that  the  peritoneum,  in  passing  from  the  sublumbar  region  to  the  last 
portion  of  the  colon,  does  not  cover  the  surface,  which  adheres  by  connective 
tissue  to  the  inferior  aspect  of  the  pancreas  and  csecum  ;  neither,  in  being  carried 
from  one  branch  of  the  colic  flexure  to  the  other,  does  it  envelop  their  opposed 
sides,  except  at  the  pelvic  flexure,  where  it  forms  the  meso-colon. 

The  muscular  tunic  does  not  differ  in  its  arrangement  from  that  of  the 
caecum  ;  neither  does  the  mucous  membrane.  The  arteries  emanate  from  the 
great  mesenteric  ;  they  are  the  two  colic  arteries.  The  two  satellite  veins  soon 
form  a  single  trunk,  which  enters  the  vena  portae.  The  lymphatics  empty  them- 
selves into  Pecquet's  reservoir.  The  nerves  emerge  from  the  great  mesenteric 
plexus. 

The  Small,  Single,  or  Floating  Colon  (Fig.  282). — This  is  a  sacculated 
tube,  which  succeeds  the  large  colon,  and  is  terminated  in  the  pelvic  cavity 
by  the  rectum. 

Length — Form — Course — Relations. — It  is  about  10  feet  in  length,  and  is 
arranged  in  a  similar  manner  to  the  small  intestine,  except  that  it  is  double  the 
size  of  that  viscus,  is  regularly  sacculated  on  its  surface,  and  is  provided  with 
two  wide  and  thick  longitudinal  bands,  one  on  the  side  of  its  great,  the  other  on 
its  small,  flexure.  Arising  from  the  terminal  extremity  of  the  large  colon,  to  the 
left  of  the  cfficum,  where  it  is  related  to  the  termination  of  the  duodenum,  and 
where  it  receives  the  insertion  of  the  great  omentum,  this  intestine  is  lodged  in 
the  left  flank,  forming  folds  which  are  mixed  with  the  convolutions  of  the  small 
intestine.  It  afterwards  passes  into  the  pelvic  cavity,  to  be  directly  continued  by 
the  rectum. 

Mode  of  attachment. — Floating  like  the  small  intestine,  the  small  colon  is 
suspended  by  a  serous  layer,  exactly  similar  to  the  mesentery  proper,  though 
wider,  and  named  the  colic  mesentery.  This  mesentery  is  detached  from  the 
sublumbar  region,  not  from  around  a  central  point,  but  from  a  line  extending 
from  the  great  mesenteric  artery  to  the  interior  of  the  pelvic  cavity.  It  is 
narrower  at  its  extremities  than  in  its  central  portion. 

Interior. — The  interior  of  the  floating  colon  shows  valvular  folds,  analogous 
to  those  of  the  csecum  and  large  colon.  It  is  in  the  intervals  between  these  that 
the  fgecal  matters  are  moulded  into  balls. 

Structure. — The  serous  membrane  is  without  special  interest,  and  the 
muscular  tunic  is  similar  to  that  of  the  large  colon.  The  mucous  membrane  is 
also  the  same.  These  membranes  receive  their  blood  by  the  small — and  a 
branch  of  the  gi'eat — ynesenteric  artery.  A  venous  trunk,  passing  between  the 
layers  of  peritoneum  forming  the  mesentery,  carries  back  the  blood  to  the  vena 
portae.  The  lymphatics  are  nearly  as  fine  and  numerous  as  those  of  the  small 
intestine  ;  they  enter  the  same  confluent — the  reservoir  of  Pecquet. 

Functions  of  the  Colon. — In  this  intestine  is  accomplished  the  absorption 
of  fluids,  and  of  soluble  alible  matters.  When  the  alimentary  mass  arrives  in 
the  small  colon,  deprived  of  its  assimilable  principles  and  charged  with  excretory 


484  TEE  DIGESTIVE  APPARATUS  IN   MAMMALIA. 

substances  thrown  out  on  the  surface  of  the  intestinal  tube,  it  loses  its  name  and 
receives  that  of  excremejtt  or  J(eces.  This  excrement,  compressed  by  the  peri- 
staltic contractions  of  the  muscular  tunic,  is  divided  into  httle  rounded  or  oval 
masses,  which  find  their  way  to  the  rectum,  where  they  accumulate,  and  whence, 
in  due  course,  they  are  expelled. 

C.  Rectum  (Fig.  282). 

The  rectum  extends,  in  a  straight  line,  from  the  entrance  to  the  pelvic 
cavity  to  the  posterior  opening  of  the  digestive  canal,  or  amis.  It  is  nothing 
more,  properly  speaking,  than  the  extremity  of  the  small  colon,  the  limit  which 
separates  them  being  somewhat  arbitrary  ;  it  differs  from  that  viscus,  however, 
in  having  no  bulgings,  and  in  its  walls  being  thicker  and  more  dilatable  ;  so  that 
it  can  be  distended  into  an  elongated  pouch,  and  form  a  reservoir  or  receptacle 
for  the  excrementitious  matters  until  they  are  expelled. 

Relations. — It  is  related,  superiorly,  to  the  roof  formed  by  the  os  sacrum ; 
inferiorly,  to  the  bladder,  the  deferent  canals,  vesiculse  seminales,  prostate  gland» 
Cowper's  glands,  or  to  the  vagina  and  uterus ;  laterally,  to  the  sides  of  the 
pelvis. 

Mode  of  attachment. — There  ought  to  be  considered  as  such  :  1.  The  posterior 
extremity  of  the  colic  mesentery,  representing  the  meso-redum.  2.  An  orbicular 
fold,  constituted  by  the  peritoneum  in  its  circular  reflection  around  this  viscus 
at  the  extremity  of  the  pelvic  cavity.  3.  The  suspensory  ligaments  of  the  penis, 
which,  joining  under  the  rectum,  form  a  ring  encircling  the  posterior  extremity 
of  the  intestine  (see  Fig.  282  and  the  description  of  the  penis).  4.  A  thick, 
triangular  band,  comprising  two  lateral  parts,  and  composed  of  white  muscular 
fibres  ;  this  band,  which  is  really  a  prolongation  of  the  muscular  tunic  of  the 
viscus,  is  detached  from  the  rectum  above  the  anus,  and  is  attached  to  the 
inferior  aspect  of  the  coccygeal  bones,  between  the  inferior  sacro-coccygeal 
muscles,  where  its  outline  can  be  seen  beneath  the  skin  when  the  tail  is  elevated. 

Stkuctuee. — The  serous  membrane  does  not  envelop  the  whole  of  the 
rectimi,  that  portion  which  traverses  the  bottom  of  the  pelvic  cavity  being  left 
uncovered  by  it.  The  muscular  layer  is  very  thick,  and  composed  of  large, 
longitudinal,  and  slightly  spiral  fasciculi,  beneath  which  are  annular  fibres.  The 
mucous  membrane,  loosely  attached  to  the  muscular  tunic,  shows  longitudinal  and 
transverse  rugfe.  The  siuall  mesenteric  and  the  internal  pvdic  artery  {artery  of 
the  bidb)  supply  these  membranes  with  blood.  The  nerves  are  derived  from  the 
•pelvic  or  hypoyastric  plexus. 

Anus. — The  anus,  or  posterior  opening  of  the  digestive  tube,  is  situated 
at  the  posterior  extremity  of  the  rectum,  under  the  base  of  the  tail,  where,  in 
Solipeds,  it  can  be  seen  forming  a  rounded  prominence,  which  diminishes  with 
age.  It  is  at  the  border  or  margin  of  this  orifice,  which  is  corrugated  like  the 
mouth  of  a  draw-purse  where  the  intestinal  mucous  membrane  meets  with,  and 
is  continued  by,  the  external  skin. 

In  proceeding  from  within  outwards,  there  are  found  the  following  elements 
entering  into  the  structure  of  the  anus  :  1.  The  mucous  membrane  of  the 
rectum.  2.  The  prolongation  of  the  circular  and  longitudinal  fibres  of  the 
muscular  layer,  forming  what  is  named  the  internal  sphinctei'.  3.  A  sphincter 
muscle,  composed  of  red  fibres,  which  receives  the  insertion  of  a  retractor.  4.  The 
fine,  hairless,  and  closely  attached  skin,  which   covers  the  sphincter  ;  though 


THE  INTESTINES.  4S5 

destitute  of  hair,  it  is  rich  in  sebaceous   follicles.     "We  will  only  notice  the 


The  Sphincter  of  the  Anus  (sphincter  ani)  is  formed  of  circular  fibres, 
some  of  which  are  fixed  above,  under  the  base  of  the  tail,  and  are  mixed,  below, 
with  the  muscles  of  the  perineal  region,  especially  the  posterior  constrictor  of  the 
vulva  in  the  female  ;  in  the  male,  these  fibres  are  lost  on  the  surface  of  the 
perineal  aponeurosis.  Comprised  between  the  skin  and  the  prolongation  of 
the  muscular  layer  of  the  rectum,  this  muscle  is  (during  life),  owing  to  its 
tonicity  and  natural  shape,  in  a  state  of  almost  permanent  contraction,  in  order 
to  keep  the  anal  aperture  closed  ;  it  is  only  relaxed  during  the  expulsion  of 
faecal  matters  or  intestinal  gases. 

The  Retractor  of  the  Anus,  or  Ischio-anal  muscle  {retractor  ani),  is  a 
wide  band,  attached  to  the  internal  surface  of  the  sacro-sciatic  ligament,  and  even 
to  the  supra-cotyloid  crest,  by  aponeurotic  fibres.  The  fasciculi  composing  this 
band  are  all  parallel  to  each  other,  while  their  posterior  extremities  are  insinnated 
beneath  the  sphincter,  and  are  mixed  wdth  its  fibres.  This  arrangement  of  the 
retractor  ani  clearly  indicates  that  it  pulls  the  anus  forwards,  re-establishing  it  in 
its  normal  position  after  expulsion  of  the  f feces — an  act  that  always  results  in 
canying  the  posterior  extremity  of  the  rectum  backwards. 

These  two  muscles  are  of  a  red  colour,  and  belong  to  those  of  animal  life. 
Their  vessels  are  derived  from  the  same  sources  as  those  of  the  rectum.  The 
Jmmorrhoidal  nerve  supplies  them  both  with  filaments. 

Differential  Characters  of  the  Intestines  in  the  other  Animals. 

In  the  domesticated  auimals,  the  intestines  vary  as  much  in  their  dimensions,  length,  and 
diametei-,  as  in  their  general  arrangement. 

1.  The  Intestines  of  the  Rabbit  (Fig.  286). 

As  for  the  stomach,  so  for  the  intestine  we  place  the  Ritbhit  immediately  after  Solipeds, 
'because  the  analogies  are  more  marked  in  them  than  in  the  other  animals. 

The  small  intestine  does  not  show  any  dilatation  at  its  commencement,  but  it  has  an 
enormous  one  at  its  termination  in  the  caecum,  and  which  has  in  its  interior  a  fine  Fever's  patch  ; 
for  this  reason  it  is  named  the  glandular  pouch.  The  other  agminated  glands  are  equally 
very  developed,  and  are  remarkable  for  their  thickness,  thougli  they  are  not  numerous — being 
•only  seven  or  eight.  They  are  easily  seen  through  the  thin  wall  of  the  intestine,  when  this 
has  been  washed  and  inflated.  This  intestine  reaches  the  caecum  in  passing  before  the  first 
portion  of  the  colon. 

The  cseciim  is  also  proportionately  more  voluminous  than  in  Solipeds.  As  in  them,  it  has 
the  sliape  of  a  cone  suddenly  attenuated  towards  its  summit,  and  forming  an  arch  or  crook  at 
its  upper  part;  but  this  crook  is  not  very  distinctly  separated  from  the  colon,  and  is  continuous 
witli  it,  without  showing  any  constriction.  Its  internal  surface  is  very  curious,  as  it  is 
traversed  by  a  spiral  ridge  of  mucous  membrane,  which  describes  about  twenty  turns  on  the 
wall  of  the  intestine,  and  ceases  about  4  inches  from  the  point.  This  layer — the  presence  of 
whicli  is  marked  by  a  depression  externally,  that  corresponds  to  its  fixed  border — may  be  about 
\  of  an  inch  or  more  in  depth.  The  inferior  cul-de-sac  of  tlie  viscus,  into  which  this  fold  does 
not  enter,  forms,  like  the  termination  of  the  small  intestine,  a  veritable  glandular  pouch.  The 
orifice  of  this  latter  intestine  does  not  project  into  the  interior  of  the  caecum ;  Bauhin's  valve  is 
a  disc,  pierced  like  the  iris,  and  fixed  by  its  larger  circumference  around  the  margin  of  that 
opening. 

The  colon  also  shows  the  division  into  two  portions — the  first,  dilated  and  sacculated,  and 
even  provided  with  rudimentary  longitudinal  bands  on  its  external  surface — is  covered  inter- 
nally by  round  and  regularly  arranged  prominences  which  resemble  tliick  villi,  or  traces  of 
tlie  valvulae  conniventes;  the  second,  narrower  and  uniformly  cylindrical,  lies  alongside  tlie 
duodenum,  ascends  into  the  diaphragmatic  region  in  company  with  that  intestine,  and  termi- 
nates in  the  rectum,  after  describing  several  floating  convolutions.  On  the  sides  of  the  rectum 
nre  two  elongated  glands  which  open  into  the  perineal  region. 


486 


THE  DIGESTIVE  APPABATUS  IN  MAMMALIA. 


The  total  length  of  the  Rabbit's  intestines  is  nearly  twenty  feet,  of  which  tl>e  small  intestine 
takes  about  ten  feet. 

2    The  Intestines  of  Ruminants  (Figs.  287,  288). 

The  small  intestine  of  the  Ox  floats  at  the  extremity  of  a  broad  mesenteric  layer,  which  is 
narrower  in  front  than  behind,  plane  throughout,  except  at  its  intestinal  border,  which  is  of 
considerable  length,  and  is  folded  into  a  multitude  of  festoons.  Twice  the  length  of  the  small 
intestine  of  the  Horse — averaging  about  49  yards — it  is  about  one-half  its  diameter.     The 

Fig.  286. 


INTESTINES  OF   THE    RABBIT   (GENERAL   VIEW). 

r,  Liver;  E,  stomach.     1,  Duodenum ;  2,  2',  jejunum;  3,  ilium  ;  4,  4',  4",  caecum;  5,  point  of  tha 
caecum  (pushed  to  the  right);  6,  first  portion  of  the  colon;  6',  second  portion  of  the  colon. 


duodenum,  at  first  sustained  by  the  omentum,  which  attaches  the  small  curvature  of  the  fourth 
compartment  of  the  stomach  to  the  posterior  fissure  of  the  liver,  form-  a  particular  loop,  which 
is  in  contact  with  the  sublumbar  region  before  it  goes  to  be  suspended  by  the  large  mesentery, 
and  to  be  continued  by  the  convolutions  of  the  floating  portion.  The  ileum  terminates  as  in 
the  Horse.  The  Peyerian  glands  are  less  numerous  on  the  internal  surface  of  the  small 
intestine  than  in  Solipeds,  though  they  are  larger  in  size.  In  the  Sheep  and  Goat,  they 
»re  often  more  than  eight  inches  in  length,  and  extend  to  Bauhin's  (ileo-csecal)  valve. 

The  csecum  is  nearly  cylindrical  in  form,  without  bulgings  or  longitudinal  bauds.    The 


THE  INTESTINES. 


487 


extremity  of  the  cul-de-sac,  rounded  and  globular,  floats  freely  in  the  abdominal  cavity,  and  is 
directed  backwards.     At  its  opposite  extremity,  the  caecum  is  continued  directly  with  the 


Fig.  287. 


STOMACH    AND   INTESTINES   OF    THE   SHEEP  (GENERAL   VIEW). 

Ru,  Rumen;  Re,  reticulum;  F,  omasum;  C,  abomasum ;  E,  great  omentum;  Fo,  liver;  R,  right 
kidney ;  P,  right  e.xtremity  of  the  pancreas ;  M,  mesentery.  1,  Duodenum  ;  2,  floating  portion  of 
the  small  intestine ;  3,  terminal  portion  of  the  small  intestine ;  4,  extremity  of  the  cul-de-sac  of 
the  caecum  ;  5,  ellipsoid  convolutions  of  the  colon,  seen  through  the  right  layer  of  the  mesentery  ; 
6,  last  turn  of  the  double  colon  ;  7,  mesenteric  glands. 


488  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

colon,  without  forming  an  arch,  after  having  received  the  insertion  of  the  small  intestine.  In 
the  Ox,  in  the  vicinity  of  this  insertion,  there  are  traces  of  one  of  Peyer's  patches.  In  the 
Sheep  and  Goat,  these  patches  are  very  numerous. 

The  colon,  sustained  between  the  layers  of  tlje  great  mesentery,  on  the  margin  of  which  is 
suspended  the  small  intestine,  is  coiled  upon  itself  in  such  a  way  as  to  form  u  certain  number 
of  elliptical  convolutions,  by  at  first  maiiinj;  several  concentric  spiral  turns,  which  leave  a 
certain  interval  between  them  for  the  reception  of  the  eccentric  convolutions.  The  last  spiral 
turn  is  a  little  distant  from  the  others ;  in  the  smaller  Ruminants,  it  is  close  to  the  insertion  of 
the  mesentery  in  the  small  intestine,  which  it  follows  to  near  the  duodenum,  in  describing 
regular  festoons.  On  arriving  near  the  trunk  of  the  great  mesenteric  artery,  this  convolution 
passes  to  the  right  of  that  vessel,  and  is  directed  backwards,  then  forwards,  thus  forming  a 
flexure,  and  turns  back  in  company  with  the  duodenal  flexure.  The  colon  then  continues  in  a 
direct  line  to  the  rectum,  attached  to  a  short  mesenteric  layer,  which,  by  its  position,  resembles 
the  large  suspensory  baml  of  the  floating  colon  in  Solipeds. 

The  calibre  of  this  intestine  is  at  first  equal  to  that  of  the  caecum ;  but  it  soon  becomes 
constricted,  and  maintains  a  uniform  diameter,   which  scarcely  exceeds  that  of  the  small 

Fig.  288. 


OENERAL    VIEW    OF    THE    INTESTINES    OF    THE    OX    (RIGHT    FACE). 

A,  Origin  of  the  duodenum  ;  B,  floating  portion  of  the  small  intestine  ;  C,  termination  of  the  small 
intestine ;  D,  caecum ;  E,  its  point  directed  backwards ;  f,  flexure  of  the  large  colon  at  its  termi- 
nation ;  G,  H,  terminal  portion  ot  the  intestine.  1,  Insertion  of  the  ductus  choledochus ;  2, 
insertion  of  the  pancreatic  duct. 

intestine  of  the  Horse.  The  muscular  layer  has  the  same  arrangement  as  in  the  latter, 
although  it  is  not  covered  in  all  its  points  by  the  serous  tunic,  in  consequence  of  the  situation 
of  the  colon  between  the  two  layers  of  the  mesentery.  In  emaciated  animals,  however,  it  may 
be  remarked  that  the  serous  covering  furnished  by  these  layers  to  the  muscular  coat  of  the 
colon  is  more  extensive  than  at  first  we  might  be  led  to  believe ;  on  tlie  left  side,  the  promi- 
nences of  the  spiral  convolutions  are  found  to  s-tand  in  relief  on  the  surface  of  the  mesentery, 
and  it  is  therefore  more  completely  enveloped  in  the  corresponding  peritoneal  layer. 

From  this  description,  it  will  be  seen  that  in  the  large  intestine  of  the  Ox,  Sheep,  and 
Goat,  the  cxcal  division  is  well  defined,  but  the  division  of  the  colon  into  a  large  or  double, 
and  a  small  oi  floating  portion,  can  scarcely  be  made  out;  unless  we  regard  as  the  large  or 
flexured  colon,  the  spiral  folds  contained  between  the  layers  of  mesentery,  and  see  the  floating 
portion  in  the  posterior  extremity  of  the  tube  lying  at  first  Rgainst  the  sublumbar  wall  of  the 
abdomen,  and  afterwards  suspended  by  the  short  mesenteric  frtenum  which  resembles  tlie  great 
colic  mesentery  of  Solipeds.  It  is  worthy  of  remark  that  the  great  mesenteric  artery  goes  to 
the  first,  and  the  small  mesenteric  to  the  second  portion,  as  in  the  Horse. 

Measured  throughout  its  whole  extent,  from  the  csecal  cul-de-sac  to  the  anus,  the  large 
intestine  of  the  Ox  is  from  33  to  39 J  feet.  It  is,  therefore,  longer  than  that  of  the  Horse; 
but  its  capacity  is  much  less,  for  it  does  not  exceed  from  6J  to  7J  gallons. 

3.  The  Intestines  of  the  Pig. 
The  average  length  of  the  Pig's  intestines  is  about  72  feet,  of  whicli  56  go  to  the  small, 
and  16  to  the  large  intestine. 


THE  INTESTINES. 


489 


In  their  general  arrangement  they  bear  some  resemblance  to  those  of  the  Ox.  The  small 
intestine  is  suspended  from  the  border  of  a  mesenteric  layer,  which  contains  an  elongated  mass 
of  lymphatic  glands.     The  duodenum  forms  an  S  curve  in  the  convolutions  of  the  colon.     The 

Fig.  289. 


GENERAL   VIEW   OF   THE    INTESTINES   OF   THE    PIG. 

E,  Stomach ;  F,  f',  liver ;  p,  pancreas ;  R,  spleen ;  M,  mesentery ;  v,  bladder.  1,  Duodenum ;  2, 
jejunum ;  3,  origin  of  the  ileum ;  4,  caecum,  the  end  of  which  has  been  turned  to  the  left ;  5, 
principal  mass  of  the  colon;  5',  last  flexure  of  the  colon  emerging  from  the  principal  mass; 
6,  mesenteric  gland. 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


ileum  occupies  the  posterior  border  of  the  mesentery,  reaching  the  cjecum  by  keeping  on  the 

right  of  the  colon ;  its  insertion  is  oblique. 

Among  the  peculiarities  of  the  small  intestine,  may  be  cited  the  presence  of  an  immense 

Peyerian  gland,  which  occupies  the  latter  portion  of  the  canal,  where  it  figures  as  a  band 

measuring  from  5  to  6^  feet  in  length. 

The  cmcum  is   directed   backwards,  and   shows,  on   its  internal  surface,  some   Peyerian 

patches  ;  it  is  sacculated,  as  in  the 
Fig.  290.  Horse,  and  is  furnished  with  three 

longitudinal  bands.  The  colon  is 
not  comprised  between  the  layers 
of  the  mesentery,  except  in  its 
latter  portion  ;  for  the  remain iler  of 
its  extent  it  is  on  the  left  side  of 
the  mesenteric  layer,  where  it 
forms  a  distinct  mass.  It  describes 
three  turns  from  right  to  left,  and 
three  turns  from  left  to  right;  it 
then  passes  forward,  and,  crossing 
again  from  right  to  left,  insinuates 
itself  between  the  duodenum  and 
pancreas.  It  has  two  of  these 
muscular  bands  in  a  portion  of  its 
track,  and  even  three  towards  the 
csecum. 

The  rectum  is  situated  above 
the  convolutions:  of  the  colon,  at 
the  border  of  a  special  mesenteric 
layer. 

4.  The  Intestines  of  Carnivoea 
(Figs.  290,  291). 

The  intestines  of  the  Caruivora 
are  remarkable  for  their  shortness 
and  small  volume.  In  a  Dog  of 
ordinary  size,  they  scarcely  measure 
more  than  14  lectin  length,  of  whicli 
only  from  24  to  28  inches  are  for 
the  large  intestine.  In  the  Cat, 
the  latter  is  about  oue-half  this 
length,  and  the  entire  extent  of  the 
viscus  is  equal  to  about  6  or  7  feet. 
With  regard  to  capacity,  Colin  gives 
the  following  averages :  for  the 
Dog's  small  intestine,  1  quart;  tliat 
of  the  Cat,  ^  of  a  pint ;  for  the 
large  intestine  in  tiie  Dog,  nearly 
1  quart,  and  in  the  Cat,  a  trifle  more 
than  J  of  a  pint. 

The  small  intestine,  suspended 
at  the  extremity  of  a  mesentery 
similar  to  that  of  Solipeds,  rests 
on  the  inferior  abdominal  wall.  It 
is  distinguished  by  the  thickness 
of  its  parietes,  the  length  and 
number  of  its  \\\\i,  which  cover  its 
inner  surface,  and  which  are  even 
found     accumulated     on    Peyer's 

patches.     These  latter  number  about  20  in  the  Dog,  and  5  or  6  in  the  Cat. 

The  csecum  forms  only  a  small,  spirally  twisted  appendix,  lined  by  a  plicated  and  very 

follicular  mucous  membrane,  particularly  in  the  Cat,  and  shows  at  the  bottom  of  the  cul-de-sac 

a  true  Peyer's  gland. 


INTESTINES  OF  THE  DOG. 
a,  Stomach  ;  h,  duodenum  ;  c,  jejunum  ;  d,  ileum  ;  e,  caecum  ; 
/,  ascending  colon ;  g,  transverse  colon ;  h,  origin  of  de- 
scending colon ;  i,  great  omentum  ;  k,  spleen  ;  I,  mesentery  : 
m,  pancreas.  1,  Aorta ;  2,  great  mesenteric  artery ;  3, 
artery  of  the  duodenum  ;  4,  artery  of  the  large  intestine  ; 
5,  small  mesenteric  artery. 


THE  INTESTINES. 


491 


The  colon  is  scarcely  larger  than  the  small  intestine,  and  is  neither  sacculated  nor  furnished 
with  longitudinal  bands.  In  its  short  course,  it  is  disposed  somewhat  like  the  same  intestine 
in  Man ;  and,  as  in  him,  it  may  be  divided  into  the  ascending  (Fig.  290,  /),  transverse  (g),  ancj 
descending  colon  (ft),  which  is  continued  directly  by  the  rectum. 

Near  the  anus,  this  latter  viscus   presents  on  its  sides  two  narrow  apertures  leading  to 


DIGESTIVE    APPARATtrs  OF   THE   CAT. 

F,  Liver;  V,  gall-bladder;  E,  stomach;  R,  spleen;  R',  right  kidney;  D,  duodenum;  Pa,  pancreas; 
C,  caecum;  In,  small  intestine  (middle  portion);  I,  ilium;  M,  M,  mesentery;  G,  mesenteric 
glands;  Re,  rectum;  Ve,  bladder;  Di,  diaphragm;  PM,  sublumbar  muscles;  P,  left  lung;  P', 
right  lung. 


two  glandular  pouches,  which  are  filled  with  a  brownish  matter  that  has  a  strong  and  foetid 
odour,  and  is  secreted  by  the  glands  covering  the  internal  wall  of  these  diverticuli. 

(Measurements  of  the  intestines,  always  a  subject  of  interest  to  comparative  anatomists, 
have  been  frequently  made  by  different  authorities.  Leyh  gives  the  length  of  the  Horse's 
intestines  as  from  10  to  12  times  that  of  its  body ;  those  of  the  Ox  as  from  20  to  22  times;  the 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


Sheep  and  Goat,  from  26  to  28  times ;  the  Pig,  from  15  to  17  times ;  the  Dog,  from  4J  to  5J  times ; 
and  the  Cat,  from  4  to  5  times. 

According  to  Hering,  tlie  entire  length  of  the  intestines  of  the  Horse  averages  100  Wurtem- 
burg  feet,  70  of  which  are  for  the  small  intestine,  and  30  for  the  large.  In  the  Ox  they  are 
150  feet,  120  being  for  tiie  small  intestine,  and  30  for  the  large;  in  the  sheep  they  average  90 
feet,  from  (>5  to  70  being  allowed  for  the  small  intestine;  those  of  the  Goat  measure  95,  the 
small  intestine  being  70 ;  in  the  Pig  they  are  90  feet,  72  of  which  are  for  the  small  intestine, 
and  18  for  the  large;  large-sized  Dogs  averaged  from  23  to  27  feet,  from  20  to  22  of  which  were 
for  the  small  int.  stine ;  small  dogs  had  only  6  feet  in  many  instances.  The  Cat  has  from 
4  to  5  feet.) 

Comparison  of  the  Intestines  of  Man  with  those  of  Animals. 

Not  unfreqnently  the  small  intestine  of  Man  is  divided  into  duodenum  and  small  intestine 

proper.     The  duodenum  is  from  9  to  11 


Fig.  292. 


inches  in  length  ;  is  dilated  at  its  origin, 
and  firmly  attached  to  the  posteiior  face 
of  the  liver  by  a  peritoneal  fold,  and  to 
the  right  of  the  sublunibar  ngion  by 
connective  tissue.  It  describes  the  arc  of 
a  circle,  in  the  concavity  of  which  is 
lodged  the  right  extremity  of  tlie  pan- 
creas, and  not  the  caecum,  as  in  Solipeds. 
Tlie  small  intestine  proper  is  suspended 
by  a  mesentery  somewhat  similar  to  that 
of  the  Horse.  Its  length  varies  much — 
from  13  to  26  feet.  Its  internal  face  has 
a  large  number  of  transverse  rugse,  the 
valvulae  conniventes.  It  also  shows  from 
20  to  25  Peyer's  patches,  particularly  in 
the  ileo-csecal  portion.  Its  structure  is 
like  that  already  described. 

In  the  large  intestine  are  recognized 
the  caecum,  colon,  and  rectum. 

The  caecum  is  a  small  reservoir  placed 
in  the  right  iliac  fossa,  a  little  obliquely 
downwards  and  to  the  left.  It  commences 
at  the  ileu-csecal  valve,  has  an  average 
length  of  about  2^  inches,  and  terminates 
by  a  rounded  extremity  with  a  small 
hollow  prolongation,  averaging  3  inches 
in  length — the  ciecal  or  vermiform,  appen- 
dix. The  mucous  membrane  is  like  that 
of  animals,  and  the  muscular  tunic  is  the 
same. 

The  human  colon  is  regularly  saccu- 
lated, like  the  small  colon  of  the  Horse ; 
it  begins  in  the  right  iliac  fossa,  above 
the  valvula  Bauhini ;  it  ascends  to  the 
lower  face  of  the  liver,  passes  abruptly 
across  from  right  to  left,  and,  arriving 
at  the  spleen,  again  changes  its  direction 
downwards  to  the  iliac  fossa ;  it  then 
again  describes  the  iliac  S,  to  reach  the 
mesial  line,  where  it  is  continued  by  the 
rectum.  From  this  course,  the  colon  has  been  divided  into  three  portions :  the  ascending  colon, 
transverse  colon,  and  descending  colon.  In  the  ascending  and  transverse  colon  are  observed 
three  series  of  sacculi,  separated  by  three  muscular  longitudinal  bands;  the  descending  colon 
has  only  two. 

There  is  scarcely  anything  special  to  note  in  the  rectum  and  anus,  except  that  they — and 
especially  the  latter— are  very  rich,  in  arteries  and  varicnse  veins,  and  that  the  anus  is  separated 
from  the  rectum  by  small  cavities  open  in  front,  and  which  are  found  in  the  Dog ;  these  are  the 
sinuses  of  Morgagni. 


THE   HUMAN   INTESTINES  AND  SUPERIOR   MESENTERIC 
ARTERY. 

1,  Descending  portion  of  the  duodenum;  2,  transverse 
portion ;  3,  pancreas ;  4,  jejunum  ;  5,  ileum ;  6, 
caecum  and  appendix  vermiformis;  7,  ascending 
colon;  8,  transverse  colon;  9,  descending  colon; 
10,  superior  mesenteric  artery;  11,  colica  media; 
12,  the  branch  that  inosculates  with  the  colica 
sinistra ;  13,  pancreatico-duodenalis  inferior ;  14, 
colica  dextra;  15,  ileo-colica;  16,  16,  vasa  intes- 
tmis  tenuis. 


the  organs  annexed  to  abdominal  digestive  canal.       493 

Genekal  aot)  Comparative  Survey  of  the  Abdominal  or  Essential 
Portion  of  the  Digestive  Tube. 

We  have  terminated  the  description  of  the  anatomical  characters  which 
distinguish  the  essential  portion  of  the  alimentary  canal  in  all  the  domesticated 
animals,  and  what  gradations  has  this  study  revealed  !  Let  us  recapitulate  and 
compare  them,  before  showing  the  admirable  harmony  which  pervades  these 
diverse  arrangements,  and  adapts  them  to  the  variations  in  general  organization, 
habits,  and  instincts. 

In  the  Carnivora,  which  subsist  on  flesh  (Do(/  and  Oat),  we  have  seen  a 
very  ample  stomach,  secreting  a  gastric  fluid  throughout  the  whole  extent  of  its 
mucous  membrane,  and  intestines  (relatively)  extremely  short. 

In  the  Omnivom,  or  Mammalia  which  live  on  a  mixed  diet  (Fig),  we  have 
found  a  small  portion  of  the  internal  surface  of  the  stomach  occupied  by  a  mucous 
membrane  unfitted  to  secrete  gastric  juice,  and  the  intestines  relatively  of  much 
more  considerable  capacity  than  in  Carnivora. 

With  the  Herbivora,  which  derive  their  nourishment  exclusively  from  the 
vegetable  kingdom  (Ruminants,  Rodents,  and  Solipeds),  the  surface  for  the  pro- 
duction of  the  gastric  juice  also  singularly  diminishes  in  extent,  although  the 
stomach  in  some  of  these  animals  is  remarkable  for  its  extraordinary  development. 
But  to  compensate  for  this,  the  capacity  of  the  intestinal  canal  assumes  con- 
siderable proportions,  and,  in  the  various  species,  is  in  direct  inverse  relation 
to  the  area  of  the  gastric  surface.  This  surface  being  relatively  more  extensive 
in  Ruminants  than  in  the  Rabbit,  and  more  also  in  that  animal  than  in  Solipeds, 
all  these  animals  ought  to  be  classed  in  an  inverse  order,  with  regard  to  the 
development  of  the  intestinal  surface. 

Finally,  in  considering  as  the  internal  surface  of  the  stomach  (a  point  of  view 
quite  rational)  only  those  portions  of  the  mucous  membrane  organized  for  the 
secretion  of  the  gastric  juice,  we  are  led  to  recognize  that  this  surface  is  in 
inverse  proportion  to  that  of  the  intestine  ;  that  it  reaches  its  highest  develop- 
ment in  Carnivorous  animals  ;  and  that  it  is  reduced  to  the  smallest  dimensions 
in  Solipeds — animals  which,  on  the  contrary,  present  a  very  great  development  of 
the  intestinal  surface. 

The  nature  of  the  aliment  readily  accounts  for  these  remarkable  differences. 
The  Carnivora,  living  on  sul^stantial  food,  take  it  in  very  large  quantity, 
because  they  are  exposed  to  frequent  fastings  ;  it  is,  therefore,  necessary  that 
they  should  have  a  stomach  large  enough  to  contain  the  ingested  substances, 
and  to  secrete  the  amount  of  gastric  juice  needed  to  transform  them  into 
assimilable  materials.  If  these  animals  have  a  short  and  narrow  intestine,  it  is 
because  a  small  surface  only  is  required  to  absorb  the  products  of  digestion,  these 
being  mixed  with  but  a  minimum  quantity  of  non-nutritive  substances,  and 
readily  come  in  contact  with  the  absorbing  membrane. 

With  regard  to  the  Herbivora,  their  food  contains  a  trifling  proportion  of 
nutritive  elements  in  an  extremely  large  bulk  of  material,  and  being  compelled  to 
ingest  great  quantities  at  short  intervals,  the  stomach,  properly  called,  can  only 
be  a  temporary  receptacle  for  the  aliment,  which  passes  rapidly  through  it  after 
being  impregnated  by  the  gastric  juice.  The  surface  which  secretes  that  fluid 
is  also  singularly  reduced,  because  if  it  has  to  perform  its  functions  more  frequently 
than  in  Carnivora,  it  is  not  required  to  display  so  much  activity  in  a  given  time. 
If,  on  leaving  the  stomach,  the  alimentary  matters  encounter  a  vast  intestinal 
34 


494  THE  DIGESTIVE  APPARATUS  IN   MAMMALIA. 

surface,  it  is  in  order  that  the  reparative  materials  dispei-sed  in  the  alimentaiy 
mass  may  not  escape  the  absorbent  action  of  that  surface,  and  may  be  the  more 
effectually  broughfinto  contact  with  it.  "We  have  this  exemplified  in  Ruminants  ; 
owing  to  their  double  mastication,  and  the  triturating  action  of  the  omasum, 
their  food  arrives  in  the  true  stomach  more  comminuted  and  better  attenuated 
than  in  the  Horse  ;  the  mass,  more  finely  broken  up,  retains  less  of  the  assimilable 
and  reparative  matters,  and  these  are  more  easily  taken  up  by  the  absorbing 
surface  ;  as  a  necessary  consequence,  the  intestinal  tube,  although  longer  than 
in  Solipeds,  is  far  from  offering  the  same  capacity. 

Analogous  considerations  explain  the  reason  for  the  intermediate  conformation 
of  the  digestive  canal  in  Omnivorous  animals. 

There  is,  then,  an  admirable  correlation  between  the  conformation  of  the 
digestive  tube  and  the  nature  of  the  substances  which  form  the  basis  of  the 
alimentation  of  animals  ;  and  this  harmony  is  equally  apparent  when  the  stomach 
and  intestines  are  compared  with  the  other  apparatus  of  the  economy,  and  with 
the  natm-al  habits  and  instincts  of  creatures.  So  it  is  that  an  animal  furnished 
with  an  ample  stomach  and  narrow  intestine,  will  have  shai-p  teeth  and  claws 
to  tear  its  prey,  strength  and  agility  to  capture  it,  and  will  also  possess  sanguinary 
instincts  ;  while  another,  with  its  gastric  surface  greatly  diminished,  will  have 
intestines  as  developed  in  their  length  as  in  their  capacity,  and  be  distinguished 
by  its  peaceful  habits,  the  absence  of  aggressive  claws,  and  its  dental  apparatus 
arranged  for  crushing  and  grinding  its  food — and  so  on. 

Organs  annexed  to  the  Abdominal  Portion  of  the  Digestive 
Tube. 

These  organs  are  three  in  number  :  two  glands — the  liver  and  pancreas,  which 
pour  into  the  small  intestine  two  particular  fluids,  the  bile  and  pancreatic  juice ; 
and  a  glandiform  organ,  the  splee?i,  remarkable  for  its  numerous  vascular  con- 
nections with  different  organs  of  the  digestive  apparatus,  and  which  for  this 
reason  deserves  to  be  studied  with  it,  although  it  is  doubtful,  if  not  improbable, 
that  it  has  anything  to  do  with  digestion. 

Preparation. — These  three  organs  can  readily  be  studied  after  removing  tlie  intestinal 
mass,  as  indicated  at  page  471.  In  order  to  examine  the  details  of  their  organization  with 
more  fiicility,  it  would  be  well  to  detach  them  jtltogether,  with  the  diaphragm  and  kidneys,  and 
to  lay  out  the  whole  on  a  table.  (To  study  the  relations  of  these  three  organs  with  those  of 
the  abdominal  cavity,  it  is  advisable  to  place  the  subject  on  its  sternum,  after  removing  the 
intestines,  and  to  detach  the  posterior  part  of  the  body  at  the  loins.) 

1.  The  Liver  (Figs.  293  to  298) 

Situation — Direction. — This  organ  is  situated  in  the  abdominal  cavity,  to  the 
right  of  the  diaphragmatic  region,  and  in  an  oblique  direction  downwards  and 
to  the  left. 

Weight. — The  weight  of  the  healthy  liver  in  a  middle-sized  horse,  is  eleven 
pounds. 

Form  and  External  Surface. — Removed  from  its  connections  with  the  neigh- 
bouring organs,  and  viewed  externally,  it  is  seen  to  be  flattened  before  and 
behind,  irregularly  elongated  in  an  elliptical  manner,  thick  in  its  centre,  and  thin 
towards  its  borders,  which  are  indented  in  such  a  manner  as  to  divide  the  organ 
into  three  principal  lobes.  Tliis  configuration  permits  it  to  be  studied  in  two 
faces  and  a  circumference. 


THE  ORGANS  ANNEXED   TO  ABDOMINAL   DIGESTIVE  CANAL.         495 

The  anterior  face  is  convex,  perfectly  smooth,  and  channelled  by  a  wide  and 
deep  fissure  for  the  passage  of  the  posterior  vena  cava.  This  fissure  extends 
directly  from  behind  to  before,  and  consequently  slightly  crosses  the  general 
direction  of  the  liver  ;  near  the  point  where  the  vena  cava  leaves  the  gland 
to  pass  through  the  diaphragm,  are  seen  the  openings  of  the  principal  sublobular 
veins.  The  posterior  face  is  equally  smooth  and  convex,  and  has  also  a  fissure 
{the  portal),  by  which  the  vena  portse  and  the  hepatic  artery  and  nerves  enter,  and 
by  which  the  biliary  ducts  emerge  from  the  liver.  This  groove  is  slightly  con- 
cave towards  the  left,  and  follows  the  direction  of  the  liver  in  proceeding  obliquely 
downwards,  backwards,  and  to  the  left. 

The  circumference  may  be  divided  into  a  superior  or  left,  and  an  inferior  or 
rigid  horder,  united  at  both  extremities  by  the  ellipsis  formed  by  the  liver.  The 
superior  hord"r  presents,  in  proceeding  from  right  to  left  :  1.  The  insertion  of  the 
ligament  of  the  right  lobe.  2.  The  origin  of  the  fissure  for  the  vena  cava.  3. 
A  notch  for  the  oesophagus.  4.  The  insertion  of  the  left  ligament.  The  inferior 
horder  is  sharp,  and  offers  two  deep  notches,  which  divide  the  liver  into  three 
lobes  :  a  superior  or  right,  an  inferior  or  left,  and  an  intermediate  one.  The 
right  lobe  is  usually  of  medium  volume,  and  has  above,  on  its  posterior  face,  an 
appendix  in  the  shape  of  a  small  secondary  lobule  of  a  triangular  form,  the  base 
of  which  corresponds  to  the  commencement  of  the  portal  fissure  :  this  is  the 
ported  lobe,  or  lobus  Spigelii}  The  left  lobe  is  nearly  always  the  largest.  The 
middle  lobe  (lobus  quadratus),  the  smallest  of  the  three,  is  itself  divided  by 
secondary  notches  into  several  digitations  or  lobules. 

Relations. — ^Viewing  the  organ  in  position,  in  order  to  study  its  general 
relations,  it  is  found  that  the  anterior  face  is  applied  against  the  diaphragm — a 
disposition  which  increases  its  convexity,  while  diminishing  that  of  its  posterior 
face  ;  and  that  the  latter  is  in  contiguity  with  the  stomach,  the  duodenum,  and 
the  diaphragmatic  flexure  of  the  colon. 

The  connections  proper  to  each  lobe  are  observed  to  be  as  follows  :  1.  The 
middle  lobe  corresponds  to  the  centre  of  the  aponeurotic  portion  of  the  diaphi'agm. 

2.  The  left  lobe  touches  the  left  and  inferior  part  of  this  aponeurosis,  and  is 
prolonged  to  the  corresponding  point  of  the  fleshy  peripheral  band  of  that  muscle. 

3.  The  right  lobe  is  in  contact  with  the  right  and  superior  part  of  the  muscle ; 
its  upper  border  touches  the  right  kidney  ;  the  pancreas  rests  against  its  base,  on 
the  posterior  face. 

Mode  of  attachment. — The  liver  is  suspended  to  the  sublumbar  wall  of  the 
abdomen,  by  the  large  blood-vessels  which  enter  its  fissures  ;  and  it  is  also  fixed 
to  the  posterior  face  of  the  diaphragm  by  four  particular  bands.  One  of  these  is 
carried  from  the  anterior  face  of  the  Uver  to  the  phrenic  or  tendinous  centre, 
and  appears  intended  to  prevent  total  displacement  of  the  organ  ;  the  other  three 
belong  to  each  particular  lobe. 

A.  The  ligament  of  the  anterior  face  of  the  liver  (or  coronary  ligament)  comprises 
two  series  of  very  short  aponeurotic  fibres,  which,  arising  from  the  two  borders  of 
the  vena  cava  fissure,  go  to  be  fixed  to  the  posterior  face  of  the  phrenic  centre. 
The  peritoneum  is  folded  over  it  on  each  side,  in  passing  from  the  diaphragm  to 
the  liver.    The  adherence  of  these  fibres  to  the  walls  of  the  vena  cava  is  extremely 

('  This,  according  to  Flower,  should  be  the  caudate,  not  the  Spirjelian  lobe ;  for  he  appears 
to  have  proved  that  the  free,  ear-shaped  lobe  situated  to  the  ris^ht  of  the  vena  portse  in  the 
Horse,  Rhinoceros,  and  Tapir,  is  not  the  lohus  Spigelii,  but  the  caudate  lobe — the  former  being 
represented  by  a  long,  attaclied,  transverse  ridge  of  hepatic  tissue  situated  farther  to  the  left.) 


496  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

close ;  and  the  vena  cava  itself  being  thus  in  a  manner  united  to  the  tissue  of 
the  liver,  it  happens  that  the  union  of  the  anterior  face  of  the  viscus  with  the 
phrenic  centre  could  not  be  more  solidly  established. 

B.  The  ligament  of  the  left  lobe  is  a  wide  peritoneal  fold,  between  the  two 
layei-s  of  which  are  some  fasciculi  of  white  fibrous  tissue.  It  is  detached  from 
the  aponeurotic  centre,  to  the  left  of  the  oesophageal  orifice,  and  is  inserted  into 
the  left  part  of  the  superior  border  of  the  liver. 

C.  The  ligament  of  the  right  lobe  is  a  fold  analogous  to  the  preceding,  but 


much  shorter,  and  the  origin  of  which,  placed  very  high  and  near  to  the  sublumbar 
parietes,  is  partly  covered  by  the  right  kidney.  It  is  inserted  into  the  superior 
border  of  the  viscus,  and  sends  a  small  layer  to  the  lobus  Spigelii ;  most  frequently, 
however,  this  lobule  is  sustained  by  a  special  peritoneal  fraenum,  given  off  from 
the  anterior  border  of  the  kidney. 

D.   The  ligament  of  the  middle  lobe  (the  longitudinal^  broad^  falciform^  or 


THE  ORGANS  ANNEXED  TO  ABDOMINAL  DIGESTIVE  CANAL.         497 

suspensory  ligament)  is  a  falciform  and  vertical  serous  layer,  the  adherent  border 
of  which  is  attached,  almost  in  the  median  plane,  to  the  posterior  face  of  the 
diaphragm,  and  even  to  the  inferior  abdominal  parietes.  At  its  free  border  is  a 
fibrous  cord  (the  round  ligament),  the  remains  of  the  foetal  umbilical  vein.  Its  upper 
part  enters  a  secondary  notch  in  the  middle  lobe,  and  is  prolonged  on  the  anterior 
face  of  this  to  the  point  where  the  vena  cava  enters  the  diaphragm. 

Structure. — As  elements  in  its  structure,  the  liver  offers  for  study  :  1.  A 
serous  membrane.  2.  A  fibrous  capsule.  3.  The  proper  and  fundamental  tissue 
of  the  organ. 

1.  Serous  Membrane. — This  membrane  is  only  an  expansion  of  the 
peritoneal  bands  or  ligaments  already  described,  and  of  which  the  two,  on  arriving 
at  the  organ,  separate  to  become  developed  on  its  surfaces,  and  to  completely 
cover  it  except  in  the  anterior  and  posterior  fissures. 

2.  Fibrous  (or  Glisson's)  Capsule. — This,  the  proper  envelope  of  the 
liver,  is  formed  by  a  very  fine  fibrous  membrane,  closely  adherent  to  the  preceding 
layer  on  the  one  side,  and  to  the  tissue  of  the  liver  on  the  other.  It  penetrates 
the  substance  of  that  tissue  in  passing  around  the  vessels  lodged  in  the  posterior 
fissure,  and  from  its  inner  face  it  sends  a  multitude  of  lamellar  partitions,  which 
separate  the  hepatic  lobules,  and  form  a  veritable  framework  in  the  interior 
of  the  organ.  The  presence  of  this  capsule  has  been  denied,  but  its  existence  is 
not  to  be  doubted  in  all  the  domesticated  animals  ;  it  is  particularly  well  developed 
in  Ruminants  and  the  Pig. 

3.  Proper  Tissue  of  the  Liver.— The  proper  substance  of  the  liver  is 
distinguished  by  its  bluish-bro\\Ti  or  violet  hue,  the  shades  of  which  vary  much 
according  to  the  subjects.  It  is  heavy  and  compact,  and  so  friable  that  it  is  crushed 
by  the  most  moderate  pressure.  It  is  composed  of  polyhedric  masses  from 
■^  to  -^Q  of  an  inch  in  diameter,  which  are  readily  enough  distinguished  from  one 
another  through  the  peritoneum  on  the  surface  of  the  organ,  particularly  when 
the  septa  thrown  in  between  them  from  Glisson's  capsule  are  hypertrophied,  from 
some  slight  chronic  irritation. 

Sometimes  the  hepatic  lobule  is  uniform  in  colour  throughout ;  often  it  shows 
a  red  central  point,  with  a  yellow  circle  around  it,  and  an  interrupted  red  ring 
circumscribing  this  again,  and  which  communicates  with  a  similar  circle  belonging 
to  the  adjoining  lobules,  so  as  to  compose  a  network  on  the  surface  of  the  gland  ; 
at  other  times  the  lobules  are  yellow  in  the  centre  and  red  at  the  circumference. 
All  these  appearances,  the  study  of  which  at  one  time  was  considered  of  much 
importance,  are  uncertain,  and  may  vary  in  a  thousand  ways,  in  combining  with 
one  another  ;  so  that  they  really  demand  but  little  attention,  due  as  they  are  to 
the  greater  or  less  degree  of  plenitude  of  the  different  vessels  entering  the  lobule. 

As  the  liver  is  composed  of  lobules  placed  beside  each  other,  we  will  describe 
one  ;  as,  when  its  structure  is  well  known,  the  organization  of  the  entire  organ 
will  be  understood. 

In  a  hepatic  lobule  we  find  :  1.  Hepatic  (or  biliary)  cells.  2.  Biliary  canaliculi 
(or  ducts).  3.  Afferent  vessels.  4.  An  efferent  vessel.  5.  Lymphatics.  6.  Con- 
nective tissue. 

Hepatic  cells. — These  are  polygonal  or  round,  and  much  resemble  squamous 
epithehum  ;  their  diameter  varies  from  3^  to  2^  of  an  inch.  They  have  no 
enveloping  membrane,  but  contain  one  or  two  nuclei  with  nucleoli,  granules 
coloured  by  biliary  matter,  small  masses  of  a  substance  which  has  been  studied 
by  Bernard  and  Schiff,  and  named  "  animal  amidon,  or  glycogen  ;  "  and,  lastly. 


498 


TEE  DIGESTIVE  APPARATUS    IN  MAMMALIA. 


adipose  granules,  the  volume  and  quantity  of  which  vary  with  the  condition 
of  the  animals,  or  the  period  of  digestion  at  which  the  liver  is  examined.  The 
hepatic  cells  are  situated  in  the  network  formed  by  the  vessels  of  the  lobule,  and 
constitute  its  principal  portion. 

Hepatic  Duds.— Bt&tmed  to  carry  away  the  bile  secreted  in  the  interior 
of  the  hepatic  lobule,  the  biliary  ducts  form  around  it  a  kind  of  girdle  that 
accompanies  the  interlobular  branches  of  the  vena  portae.  Within  and  without, 
this  girdle  sends  off  small  prolongations  ;  the  first  bring  it  into  communication 
with  the  ducts  of  the  neighbouring  lobules  ;  the  second  pass  to  the  centre  of  the 
lobule,  or  they  surround  each  cell. 

The  wall  of  the  biliary  ducts  is  a  thin  amoi-phous  membrane,  lined,  near  the 
periphery  of  the  lobule,  by  polygonal  cells,  smaller  than  the  hepatic  cells,  and, 
beyond,  by  a  kind  of  endothelium  or  cuticle. 

Afferent  vessels. — These  are  the  branches  of  the  portal  vein  and  hepatic  artery. 
The  portal  vein,  after  reaching  the  interior  of  the  liver,  divides  into  gradually 
decreasing  vessels,  until  it  terminates  in  forming  the  interlobular  reins.    These 


Fig  294 


/■ 


Fig.  295. 


,  portion  of  a  hepatic  column,  showing  its  compo- 
nent secreting  cells.  B,  Secreting  cells  detached : 
a,  In  their  normal  state;  b,  a  cell  more  highly 
magnified,  showing  the  nucleus  and  distinct  oil- 
particles  ;  c,  in  various  stages  of  fatty  degenera- 
tion. 


BILIARY  CAPILLARIES  OP 
THE  rabbit's  liver. 
PART  OF  A  LOBULE, 
SHOWING  THE  ARRANGE- 
MENT OF  THE  BILIARY 
DUCTS  IN  RELATION  TO 
THE    HEPATIC   CELLS. 

a,  Capillaries  of  the  biliary 
ducts  ;  6,  hepatic  cells  ; 
c,  biliary  ducts ;  d,  ca- 
pillary blood-vessels. 


vessels  surround  the  lobule,  communicate  with  the  neighbouring  interlobular 
veins,  and  give  off  a  large  number  of  twigs  to  the  interior  of  the  lobule,  where 
they  anastomose,  and  constitute  the  hepatic  capillary  plexus.  The  hepatic  artery 
furnishes  ramuscules,  which  mix  with  the  ramifications  of  the  portal  vein  in  the 
(vaginal)  plexus.  The  principal  branches  of  the  latter  are  all  directed  from  the 
periphery  towards  the  centre  of  the  lobule,  where  they  unite  to  form  the  afferent 
vessel.  It  results  from  this  arrangement  that  the  hepatic  cells  which  fill  the 
spaces  between  the  vessels,  are  placed  in  radiating  series. 

Efferent  vessel. — Situated  in  the  centre  of  the  lobules,  this  vessel  receives  all 
the  ramifications  of  the  capillary  plexus,  and  is  named  the  intra-lohular  or  central 
suhlohular  vein.  It  is  voluminous,  and  communicates  with  the  other  intra-lobular 
veins.  (These  intra-lobular  veins  terminate  in  the  larger  trunks  that  run  along 
the  bases  of  the  lobules,  and  are  named  the  suhlohular  veins.) 

Lymphatics.  —In  a  hepatic  lobule  are  found  very  fine  lymphatic  vessels  that 


THE  ORGANS  ANNEXED    TO  ABDOMINAL  DIGESTIVE  CANAL. 


HORIZONTAL  SECTION  OF  THREE  SUPERFICIAL 
LOBULES,  SHOWING  THE  TWO  PRINCIPAL  SYS- 
TEMS  OF   BLOOD-VESSELS. 

a,  a,  Intra-lobular  veins,  terminating  in  the  hepatic 
veins;  6,  6,  interlobular  plexus,  formed  by 
branches  of  the  portal  vein. 


suiTOimd  the  branches  of  the  hepatic  plexus,  where  they  form  the  lymphatic 
vaginfe,  or  canals  which  contain  the  blood-vessels. 

Connective  tissue. — The  intra-lobular  connective  tissue  is  scanty,  the  lobule 
being  almost  entirely  composed  of  cells 

or  capillaries  ;  some  trabeculae,  never-  ^'S-  ^^^• 

theless,  exist  around  the  lymphatic 
sheaths.  There  is,  however,  a  larger 
quantity  in  the  interlobular  spaces ; 
and  in  some  animals — especially  the 
Pig — Glisson's  capsule  sends  somewhat 
thick  lamellae  of  connective  tissue  be- 
tween these  lobules.^ 

Excretory  Apparatus  (Fig. 
298). — This  is  very  simple  in  Solipeds, 
and  is  composed  of  a  vessel  named 
the  ductus  choJedochus,  resulting  from 
the  union  of  several  trunks  lodged  in 
the  posterior  fissure  of  the  liver,  and 
which  come  from  the  three  lobes. 
Traced  in  the  substance  of  the  hepatic 
tissue,  these  branches  divide  into  more 
and  more  attenuated  vessels  that  arise 
from  the  periphery  of  the  lobules,  and 
are  continuous  with  the  biliary  ducts 
which  envelop  and  penetrate  these. 

Course. — At  its  exit  from  the  liver,  the  ductus  choledochus  lies  between  the 
layers  of  the  gastro-hepatic  omentum,  and  ascends  to  the  wall  of  the  duodenum, 
which  it  passes  through  at  about  six  inches  from  the  pylorus,  along  with  the 
principal    pancreatic   duct.      The 

orifices  of  these  two  canals   are  F'g-  297. 

surrounded  by  a  circular  mucous 
fold  (ampulla  of  Vater),  which  is 
usually  very  prominent,  and  acts 
as  a  valve  in  preventing  the 
entrance  of  alimentary  substances 
into  the  apertures  it  encircles ; 
this  office  it  fills  so  well,  that  it 
will  not  even  allow  the  air  with 
which  the  duodenum  may  be  in- 
flated, to  pass  into  the  ducts. 

There  enter  into  the  structure 
of  the  ductus  choledochus  :  1.  A 
fibrous  membrane,  which  some 
anatomists  believe  contains  un- 
striped  muscular  fibres.  2.  Sphe- 
roidal  epithelium.     3.   Numerous 

*  The  description  of  the  hepatic  lobule  has  been  intentionally  simplified  to  the  utmost,  to 
treatises  on  histology  being  left  the  task  of  discussing  the  microscopical  details  wliich  sometimes 
cause  a  lobule  to  be  considered  as  a  collection  of  tubes  placed  at  the  end  of  the  branches  of  the 
biliary  ducts,  at  other  times  as  a  portion  of  a  conglomerate  gland  full  of  blood-vessels. 


SECTION  OF  A  SMALL  PORTION  OF  THE  LIVER  OF  A 
RABBIT,  WITH  THE  HEPATIC  OR  INTRA-LOBULAR 
VEINS   INJECTED 


500  TEE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

racemose  glands,  opening  on  the  surface  of  the  epithehum  by  very  small 
orifices. 

Vessels  and  Neeves  of  the  Liver. — The  blood-vessels  are  the  hepatic 
artery,  portal  vein,  and  sublobular  veins. 

The  hepatic  arter//  is  a  branch  of  the  coeliac,  and  enters  the  gland  by  the 
posterior  fissure,  in  company  with  the  portal  vein  and  ductus  choledochus.  In 
the  liver  it  divides  into  very  fine  ramifications,  which  join  the  intra-lobular 
plexus,  anastomose  on  the  surface  of  the  biliary  ducts,  or  are  expended  either  on 
the  serous  membrane,  or  in  the  walls  of  the  portal  vein. 

The  portal  vein  is  the  functional  vessel  of  the  liver.  It  reaches  that  organ  by 
the  posterior  fissure,  and  Glisson's  capsule  accompanies  its  ramifications  as  far  as 
the  hepatic  lobules,  where  they  form  the  plexus  of  subhepatic  veins. 

The  supra-hepatic  (sublobular)  veins  are  so  named  because  they  gain  the 
antero-superior  face  of  the  viscus,  to  open  into  the  posterior  vena  cava.  They 
carry  away  the  blood  that  has  been  brought  by  the  portal  vein  and  hepatic  artery. 
Their  origm  is  due  to  the  union  of  the  intra-lobular  veins,  which  make  a  passage 

Fi?.  298. 


EXCRETORY   APPARATUS  OF   THE   HORSE  S   LIVER. 

1,  left  lobe  of  the  liver;  2,  middle  lobe ;  3,  right  lobe ;  4,  lobus  Spigelii  (caudate  lobe)  ;  6,  posterior 
vena  cava  at  its  entrance  into  the  liver ;  7,  vena  portse ;  8,  ductus  choledochus ;  9,  pancreatic 
duct;  10,  common  entrance  of  these  two  ducts  into  the  small  intestine. 

through  the  hepatic  tissue  with  which  their  walls  are  immediately  in  contact, 
gradually  join  each  other,  and  enter  the  posterior  vena  cava  on  its  way  through 
the  anterior  fissure  of  the  liver.  The  number  of  trunks  (hepatic)  entering  this 
vessel  is  considerable,  but  the  majority  are  very  small ;  the  principal  confluent 
is  placed  at  the  anterior  extremity  of  the  fissure. 

The  lymphatics  form  a  fine  superficial  plexus,  easy  to  inject ;  with  deeper 
networks  placed  around  the  vessels  that  penetrate  by  the  posterior  fissure.  In 
the  lobules  they  are  disposed  as  described  above.  Joined  to  the  lymphatics 
of  the  stomach,  they  constitute  a  single  trunk  that  goes  to  the  sublumbar 
receptacle. 

The  nerves  are  more  particularly  derived  from  the  solar  plexus,  although  the 
pneumogastric  and  diaphragmatic  also  supply  filaments  to  the  liver.  They 
interlace  around  the  hepatic  artery  and  portal  vein  ;  their  mode  of  termination 
is  unknown. 

Functions. — The  most  important  considerations  are  attached  to  the  study 
of  the  functions  of  the  liver ;  but  we  cannot  enter  into  them  in  detail  without 
going  beyond  our  subject. 


THE  ORGANS  ANNEXED   TO  ABDOMINAL  DIGESTIVE  CANAL.         501 

The  liver  more  especially  elaborates  bile  and  sugar.  It  secretes  the  bile  at 
the  expense  of  the  blood  of  the  portal  vein,  which  comes  from  the  intestinal 
tunics  charged  with  assimilable  substances  absorbed  by  the  veins  of  the  villi. 

The  bile  is,  therefore,  in  this  respect  an  excrementitious  secretion  ;  though 
all  its  elements  are  not  excreted,  some  of  them  acting  on  the  alimentary 
substances,  and  others  being  absorbed.  From  the  most  recent  researches,  it 
would  appear  that  it  has  a  share  in  the  purification  of  the  blood,  in  digestion, 
and  in  calorification — in  the  latter  especially,  as  its  absorbed  elements  are  very 
rich  in  carbon  and  hydrogen,  bodies  eminently  fitted  for  the  production  of 
animal  heat. 

The  liver  is  also  a  glycogenetic  gland,  this  function  having  been  demon- 
strated to  pertain  to  it  by  Bernard.  The  sugar  formed  in  the  hver  finds  its  way 
into  the  blood,  and  leaves  the  organ  by  the  sublobular  veins.  It  is  elaborated  in 
the  hepatic  cells,  by  the  transformation  of  the  substance  known  as  "  animal 
amidon,"  which  is  brought  into  contact  with  a  kind  of  diastaste  that  exists  with 
it  in  their  interior. 

It  will  thus  be  seen  that  the  liver  furnishes  two  very  different  products — bile 
and  sugar.  The  knowledge  of  this  fact,  combined  with  the  internal  arrangement 
of  the  organ,  has  led  some  anatomists  to  consider  the  organ  as  two  glands 
reciprocally  contained  within  each  other.  According  to  them,  one  gland  is 
tubular,  and  formed  by  the  system  of  biliary  ducts — this  gland  secretes  the  bile  ; 
the  other  gland  is  constituted  by  the  hepatic  cells,  which  produce  the  sugar.  But 
this  hypothesis  should  be  rejected,  for  it  is  probable  that  the  sugar  and  bile  are 
produced  in  the  large  hepatic  cells,  and  that  the  first  passes  into  the  veins,  while 
the  second  is  poured  into  the  biliary  ducts. 

In  Solipeds,  the  secretion  of  bile,  though  most  active  during  the  digestive 
period,  yet  goes  on  in  a  continuous  manner. 

(Certain  deductions  of  a  pathological  kind  are  based  upon  the  foregoing 
anatomical  facts,  and  have  an  important  bearing  with  regard  to  comparative 
pathology.  They  have  been  pointed  out  by  Wilson,  and  are  as  follows  :  Each 
lobule  is  a  perfect  gland  ;  its  structure  and  colour  are  uniform,  and  it  has  the 
same  degree  of  vascularity  throughout.  It  is  the  seat  of  a  double  venous 
circulation  ;  the  vessels  of  the  one — hepatic — being  situated  in  the  centre  of  the 
lobule,  and  those  of  the  other — portal — at  the  circumference.  Now,  the  colour  of 
the  lobule,  as  of  the  entire  liver,  depends  chiefly  on  the  proportion  of  blood 
contained  within  these  two  sets  of  vessels  ;  and  so  long  as  the  circulation  is 
natural,  the  colour  will  be  uniform.  But  the  instant  that  any  cause  is  developed 
which  will  interfere  with  the  free  circulation  of  either,  there  will  be  an  immediate 
diversity  in  the  colour  of  the  lobule. 

Thus,  if  there  be  any  impediment  to  the  free  circulation  of  the  venous  blood 
through  the  heart  or  lungs,  the  circulation  in  the  hepatic  veins  will  be  retarded,  and 
the  sublobular — or  supra-hepatic — and  intra-lobular  veins  will  become  congested, 
giving  rise  to  a  more  or  less  extensive  redness  in  the  centre  of  each  of  the 
lobules ;  while  the  marginal  or  non-congested  portion  presents  a  distinct  border 
of  a  yellowish  white,  yellow,  or  green  colour,  according  to  the  quantity  or  quality 
of  the  bile  it  may  contain.  "  This  is  ^passive  congestion  '  of  the  liver,  the  usual 
and  natural  state  of  the  organ  after  death ; "  and  as  it  commences  with  the 
hepatic  vein,  it  may  be  called  the  first  stage  of  hepatic  venous  congestion. 

But  if  the  causes  which  produced  this  state  of  congestion  continue,  or  be  from 
the  beginning  of  a  more  active  kind,  the  congestion  will  extend  through  the 


502  TEE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

lobular  venous  plexuses  "  into  those  branches  of  the  portal  vein  situated  in  th€ 
interlohuJar  fissures,  but  not  to  those  in  the  sjmces,  which,  being  larger,  and  giving 
origin  to  those  in  the  fissures,  are  the  last  to  be  congested."  In  this  second  stage 
the  liver  has  a  mottled  appearance,  the  non-congested  substance  is  arranged  in 
isolated,  circular,  and  ramose  patches,  in  the  centres  of  which  the  spaces  and 
parts  of  the  fissure  are  seen.  This  is  an  extended  degree  of  hepatic  venous 
congestion ;  it  is  "  active  congestion  "  of  the  liver,  and  very  commonly  attends 
disease  of  the  heart  and  lungs. 

These  are  instances  of  partial  congestion  ;  but  there  is  sometimes  general 
congestiot  of  the  organ.  "  In  general  congestion,  the  whole  liver  is  of  a  red 
colour,  but  the  central  portions  of  the  lobules  are  usually  of  a  deeper  hue  than 
the  marginal  portions.") 

Development. — The  liver  of  the  foetus  is  remarkable  for  its  enormous 
development.  Its  function  commences  early,  for  at  birth  the  intestines  are  filled 
with  meconium — a  product  of  the  biliary  secretion.  A  more  detailed  description 
will  be  given  when  the  general  development  of  the  foetus  comes  to  be  studied. 

2.  The  Pancreas. 

This  organ  has  the  greatest  resemblance  to  the  salivary  glands  in  its  structure 
and  physical  properties  ;  and  for  this  reason  it  has  been  named  the  abdominal- 
salivary  gland.. 

Situation — Weight.  —It  is  situated  in  the  sublumbar  region,  across  the  aorta 
and  posterior  vena  cave,  in  front  of  the  kidneys,  and  behind  the  liver  and 
stomach.     Its  weight  is  seventeen  ounces. 

Form  and  Relations. — The  pancreas  is  rather  irregular  and  variable  in  form, 
according  to  the  kind  of  animal.  Flattened  above  and  below,  traversed  obliquely 
from  its  inferior  to  its  superior  face  by  an  opening  for  the  passage  of  the  portal 
vein,  and  which  is  named  the  pancreatic  ring,  this  gland  is  sometimes  triangular, 
sometimes  oblong,  and  curved  on  itself  ;  it  is  under  the  latter  form  that  we  will 
notice  it. 

Its  fifces  present  the  lobulated  aspect  of  salivary  glands.  The  superior 
adheres  by  connective  tissue  to  the  aorta,  posterior  vena  cava,  coeliac  trunk,  solar 
plexus,  splenic  vessels,  and  the  right  kidney  and  supra-renal  capsule  ;  it  is 
covered  by  the  peritoneum  for  a  certain  portion  of  its  extent.  The  inferior  is 
related  to  the  base  of  the  caecum  and  the  fourth  portion  of  the  colon,  through 
the  medium  of  a  thick  layer  of  connective  tissue.  The  anterior  border,  concave 
and  undulating,  is  in  contact  with  the  duodenum  and  the  left  extremity  of  the 
stomach.  The  posterior  is  very  convex,  especially  to  the  right,  and  near  its 
middle  it  presents  a  notch  for  the  reception  of  the  portal  vein  before  its  entrance 
into  the  ring.  The  right  extremity  (or  head) — the  thinnest — adheres  to  the 
duodenum,  and  shows  the  excretory  ducts  of  the  gland.  The  left  is  carried 
towards  the  base  of  the  spleen,  in  passing  between  the  left  extremity  of  the 
stomach  and  the  kidney  of  the  same  side. 

Structure. — Superficially,  it  resembles  the  salivary  glands,  but  in  reality  it  is  not 
a  racemose  gland.  It  is  an  acinous  gland  in  which  the  elongated  culs-de-sac,  filled 
with  polyhedral  cells,  have  their  axis  occupied  by  a  vessel  and  a  cord  of  connective 
tissue.  The  excretory  vessels  disappear  on  reaching  these  culs-de-sac,  so  that  the 
secreted  products  are  infiltrated  between  the  cells  to  reach  the  duct  of  Wirsung. 

The  gland  receives  its  blood  by  the  hepatic  and  great  mesenteric  arteries ; 
the  nerves  come  from  the  solar  plexus. 


THE  ORGANS  ANNEXED   TO  ABDOMINAL   DIGESTIVE  CANAL.  503 

Excretory  apparatus. —  The  pancreas  has  two  excretory  ducts — a  principal, 
described  by  "Wirsung,  whose  name  it  bears,  and  an  accessory.  The  duct  of 
Wirsimg,  lodged  in  the  substance  of  the  gland,  but  nearer  the  superior  than  the 
inferior  face,  at  first  comprises  two  or  three  thick  branches,  which  soon  unite  to 
form  a  single  trunk  that  emerges  from  the  pancreas  by  the  left  extremity  of  the 
organ.  Larger  than  the  ductus  choledochus,  it  opens,  as  already  stated,  at 
the  same  part  of  the  duodenal  surface.  The  accessory  or  azygos  duct  {ductus 
vancreaticus  minor)  is  much  smaller  ;  it  leaves  the  principal  trunk,  receives  some 
branches  in  its  passage,  and  opens  alone  into  the  small  intestine,  directly  opposite 
the  duct  of  Wirsung. 

The  ductus  choledochus  and  the  duct  of  "Wirsung  do  not  pass  directly  through 
the  wall  of  the  intestine,  but  obliquely,  like  the  entrance  of  the  ureters  into  the 
bladder.  They  open  in  the  middle  of  a  circular  valve — the  ampulla  of  Vater. 
This  ampulla  is  limited  by  a  thick  primary  mucous  fold,  and  within  this  is  a 
second — thinner — beneath  which  the  ductus  choledochus  opens  ;  at  the  bottom  of 
the  space  circumscribed  by  this  second  fold,  beneath  a  free  mucous  lip,  is  seen 
the  duct  of  Wirsung.  Such  is  the  arrangement  of  the  ampulla  of  Vater  in  the 
Horse. 

Functions. — From  the  researches  of  Bernard,  it  appears  established  that 
the  fluid  secreted  by  the  pancreas  emulsifies  fatty  matters,  and  renders  them 
absorbable. 

3.  The  Spleen  (Fig.  299). 

The  spleen  differs  from  glands,  not  only  in  the  absence  of  an  excretory  duct, 
but  also  in  the  other  details  of  its  organization.  It  has  been  considered  as  a 
vascular  gland,  the  uses  of  which  are  not  yet  determined  in  a  precise  manner. 

Situation. — It  is  situated  in  the  diaphragmatic  region,  close  to  the  left 
hypochondriac,  and  appears  as  if  suspended  in  the  sublumbar  region,  as  well  as 
at  the  great  curvature  of  the  stomach. 

Foryn — Direction — Relations. — The  spleen  is  falciform,  and  directed  obliquely 
downwards  and  backwards.     It  has  tivo  faces,  tvw  borders,  and  a  point. 

The  external  face  is  in  relation  with  the  muscular  portion  of  the  diaphragm, 
and  is  moulded  to  it.  The  internal,  slightly  concave,  touches  the  large  colon  ;  it 
has  sometimes  a  small  lobule,  or  offers  traces  of  lobulation.  The  posterior  border 
is  convex,  thin,  and  sharp.  The  anterior,  thicker,  concave,  and  bevelled  at  the 
expense  of  the  internal  face,  is  channeled  by  a  slight  longitudinal  fissure  (or 
hilus)  that  lodges  the  splenic  vessels  and  nerves  ;  it  receives  the  insertion  of  the 
great  mesentery,  by  which  it  is  attached  to  the  greater  curvature  of  the  stomach. 
The  base,  or  superior  extremity,  is  thick  and  wide,  and  is  related  to  the  left 
kidney  and  the  corresponding  extremity  of  the  pancreas  ;  it  shows  the  insertion 
of  the  suspensory  ligament.  The  point,  or  inferior  extremity,  is  smooth  and 
thin. 

Weight. — The  average  weight  is  32  ounces  ;  but  it  is  sometimes  of  enormous 
dimensions — as  much  as  three  or  four  times  its  normal  volume. 

Mode  of  attachment. — The  spleen  is  a  floating  organ,  the  displacements  of 
which  are  limited  by  a  suspensory  ligament,  and  the  great  (or  gastro-splenic) 
omentum.  The  first  is  a  peritoneal  fold  which  proceeds  from  the  anterior  border 
of  the  left  kidney  and  the  sublumbar  wall,  and  is  strengthened  by  the  elastic 
fibrous  tissue  comprised  between  its  two  layers.  It  is  fixed  to  the  base  of  the 
spleen,  and  is  confounded,  inwardly,  with  the  great  omentum.     The  latter  is 


504 


THE  DIGESTIVE  APPARATUS  J.V  MAMMALIA. 


already  known  as  proceeding 
to  the  splenic  fissure,  whence 
serous  covering. 

Steucture. — The  tissue 
approaching  to  a  red  hue  ;  it 
of  the  finger,  and  retains  its 
its  substance  includes  a  Jib: 
vessels,  and  nerves. 

Serous  membrane. — This 
in  the  fissure  of  the  anterior 


to  the  colon,  and  in  its  passage  becoming  attached 
it  extends  over  the  surface  of  the  organ  to  form  its 

of  the  spleen  has  a  violet-blue  colour,  sometimes 

is  elastic,  tenacious,  and  soft,  yields  to  the  pressure 

imprint.     Enveloped  externally  by  the  peritoneumr^ 

rous  frameivork,  splenic  pulp,  Malpighian  corpuscleSy 

is  spread  over  the  whole  surface  of  the  organ,  except 
border.     Its  internal  face  adheres  most  intimately 


STRUCTURE   OF   THE   SPLEEN   (DIAGRAMMATIC). 

A,  Artery;  V,  vein.  1,  Splenic  trabeculse;  2,  finer  trabeculse;  3,  reticulum  of  the  splenic  pulp; 
4,  lymphoid  infiltration  into  the  sheath  of  the  arteries ;  5,  its  continuation  with  a  Malpighian 
corpuscle;  6,  membrana  propria;  7,  sheath  of  the  vein;  8,  recticulum  of  the  splenic  pulp;  9, 
termination  of  the  fibrillar  sheath  of  the  capillaries;  10,  tuft  of  arteries;  11,  arterial  capillaries; 
12,  their  opening  into  the  intermediate  tracts  of  the  pulp;  13,  veins;  14,  venous  capillaries;  15, 
part  of  the  pulp  containing  the  remains  of  cells;  16,  Malpighian  corpuscle  attached  to  (17)  an 
artery,  seen  in  a  section  perpendicular  to  the  axis  of  the  vessel. 

to  the  proper  tunic  of  the  spleen.     It  is  only  an  expansion  of  the  serous  bands 
which  limit  the  movements  of  the  viscus. 

Fibrous  frameworJc. — Under  the  peritoneal  membrane  is  a  thick,  resisting, 
fibrous  tunic,  roughened  and  granular  on  its  exterior,  and  sending  from  its  deep 
face  into  the  interior  of  the  mass  a  multitude  of  prolongations  called  trabeculce, 
which  cross  in  all  directions,  forming  a  cellular  network,  in  the  numerous  naiTOW 
meshes  of  which  are  the  other  elements  of  the  organ.  In  washing  out  a  morsel 
of  spleen  in  a  jet  of  water,  the  latter  are  removed,  and  the  outlines  of  this 
fibrous  structure  are  fully  exposed.     If  a  stream  of  water  be  passed  through  the 


TEE  ORGANS  ANNEXED   TO   ABDOMINAL  DIGESTIVE  CANAL. 


505 


splenic  artery,  the  same  result  will  be  arrived  at.  KoUiker  has  found  in  the 
proper  tunic  of  the  spleen,  and  in  its  trabeculse,  a  particular  contractile  tissue — 
the  muscular  cell-fibres — mixed  with  fasciculi  of  elastic  or  inelastic  fibrous  tissue. 
(The  proper  coat,  the  sheaths  of  the  vessels,  and  the  trabeculse,  consist  of  a  dense 
mesh  of  white  and  yellow  elastic  fibrous  tissues,  the  latter  considerably  pre- 
dominating. It  is  owing  to  the  presence  of  this  tissue  that  the  spleen  possesses 
a  considerable  amount  of  elasticity,  admirably  adapted  for  the  very  great 
variations  in  size  that  it  presents  in  certain  circumstances.  In  some  of  the 
Mammalia,  in  addition  to  the  usual  constituents  of  this  tunic,  are  found  numerous 
pale,  flattened,  spindle-shaped  nucleated  fibres,  like  unstriped  muscular  fibre.  It 
is  probably  owing  to  this  structure  that  the  spleen  possesses,  when  acted  upon  by 
the  galvanic  current,  faint  traces  of  contractility.) 

Splejiic  pulp. — This  name  is  given  to  a  reddish  pultaceous  material,  which 
partly  occupies  the  alveolar  network  formed  by  the  intersections  of  the  trabeculae. 
It  is  sustained  by  a  very  delicate  reticulum  of  connective  tissue,  and  is  composed 


Fig.  300. 


Fig.  301. 


A  SINGLE  SPr/.:NIC  CORPUS- 
CLE, FROM  THE  SPLEEN  OF 
THE   OX. 

1,  External  tunic,  or  mem- 
brana  propria;  2,  granular 
contents  ;  3,  part  of  a  small 
artery ;  4,  its  sheath,  de- 
rived from  the  external 
tunic  of  the  spleen,  with 
which  the  corpuscle  is 
closely  connected. 


BRANCH   OF   SPLENIC   ARTERY   WITH    ITS  RAMIFICATIONS 
STUDDED   WITH   MALPIGHIAN   CORPUSCLES. 


of  numerous  elements,  such  as  pigment  granules,  free  nuclei,  large  cells  with 
several  nuclei,  lymphoid  elements,  and  blood-globules  in  a  state  of  decomposition 
or  transformation.  These  globules  are  free  or  enveloped  in  an  albuminoid 
membrane. 

Malpighian  corpuscles. — These  are  contained,  like  the  splenic  pulp,  in  the 
meshes  of  the  fibrous  framework  of  the  spleen,  and  are  covered  by  that  pulp. 
Distributed  on  the  course  of  the  small  arteries,  these  corpuscles,  which  are  visible 
to  the  naked  eye,  are  little  closed  sacs  of  a  wliitish  colour.  They  are  composed 
of  an  adventitious  tissue  of  arteries,  in  which  are  accumulated,  at  certain  points, 
lymphoid  elements.  They  are,  therefore,  analogous  to  closed  folHcles  in  then* 
•structure.  (The  proper  substance  of  the  spleen  consists  of  coloured  and  colourless 
elements.  The  coloured  are  composed  of  red  blood-corpuscles  and  coloured  cor- 
puscles, either  free  or  included  in  cells.     Sometimes  unchanged  blood-discs  are 


506  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

seen  included  in  a  cell  ;  but  more  frequently  the  included  blood-discs  are  altered 
both  in  form  and  colour.  Besides  these,  numerous  deep-red,  or  reddish-yellow, 
or  black  corpuscles  and  crystals,  either  single  or  aggregated  in  masses,  are  seen 
diffused  throughout  the  pulp  substance  ;  these,  in  chemical  composition,  are 
cksely  allied  to  the  haematine  of  the  blood.  The  colourless  elements  consist  of 
r'anular  matter ;  nuclei,  about  the  size  of  the  red  blood-discs,  homogeneous  or 
granular  in  structure  ;  and  nucleated  vesicles  in  small  numbers.  These  elements 
iorai  a  large  proportion  of  the  entire  bulk  of  the  spleen  in  well-nourished 
animals  ;  whilst  they  diminish  in  number,  and  occasionally  are  not  found  at  all, 
in  starved  animals.  The  application  of  chemical  tests  shows  that  they  are 
essentially  a  proteine  compound.  The  splenic  or  Malpighian  corpuscles  are  round, 
whitish,  semi-opaque  bodies,  glutinous  in  consistence,  and  disseminated  through- 
out the  substance  of  the  organ.  They  are  more  distinct  in  early  than  in  adult 
life  or  old  age,  and  vary  considerably  in  size  and  number.  From  the  manner  in 
which  they  are  appended  to  the  sheaths  of  the  smaller  arteries  and  their  branches, 
they  resemble  the  buds  of  the  moss-rose.  Each  consists  of  a  membranous 
capsule,  composed  of  fine  pale  fibres  interlacing  in  all  directions.  The  blood- 
vessels ramifying  on  the  surface  of  the  corpuscles,  are  the  larger  ramifications 
of  the  arteries  to  which  the  sacculus  is  connected,  and  also  of  a  delicate  capillary 
plexus,  similar  to  that  surrounding  the  vesicles  of  other  glands.  These  vesicles 
have  also  a  close  relation  vrith  the  veins,  and  fche  vessels  begin  on  the  surface  of 
each  vesicle  throughout  the  whole  of  its  cu'cumference,  forming  a  dense  venous 
mesh  in  which  each  of  these  bodies  is  enclosed.  It  is  probable  that,  from  the 
blood  contained  in  the  capillary  network,  the  material  is  separated  which  is 
occasionally  stored  up  in  their  cavity ;  the  veins  being  so  placed  as  to  carry  off, 
under  certain  conditions,  those  contents  that  are  again  to  be  discharged  into  the 
circulation.  Each  capsule  contains  a  soft,  white,  semi-fluid  substance,  con- 
sisting of  granular  matter,  nuclei  similar  to  those  found  in  the  pulp,  and  a  few 
nucleated  cells,  the  composition  of  which  is  apparently  albuminous.  These 
bodies  are  very  large,  after  the  early  periods  of  digestion,  in  well-fed  animals,  and 
especially  those  fed  upon  albuminous  diet.  In  starved  animals,  they  disappear 
altogether.) 

Arteries. — These  emanate  from  the  splenic  artery  at  different  elevations,  and 
plunge  into  the  tissue  of  the  spleen,  preserving  their  reciprocal  independence. 
Their  terminal  ramifications  do  not  open,  as  has  been  said,  into  venous  sinuses, 
but  into  minute  tufts  of  capillaries,  which  traverse  the  splenic  pulp,  to  be  con- 
tinued by  the  venous  network. 

Veins. — All  the  venous  branches  of  the  spleen  open  into  the  splenic  vein,  and 
are  lodged,  with  the  con-esponding  artery,  in  the  fissm-e  of  the  organ.  Traced 
from  their  commencement,  they  are  seen  to  gradually  lose  their  constituent 
membranes,  and  to  open  into  sinuses  which  are  only  lined  by  the  endothelium 
of  the  vessels.  It  is  in  these  sinuses  that  the  network  of  venous  capillaries 
which  succeed  the  arterial  capillaries,  originates. 

Lymphatic  vessels. — These  are  found  on  the  external  surface  of  the  organ, 
and  along  the  track  of  the  blood-vessels.  (There  appear  to  be  two  systems  of 
lymphatics  in  the  spleen  of  the  Horse — one  belonging  to  the  trabecule,  which 
is  in  continuity  with  the  lymphatics  of  the  capsule  ;  and  another  accompanying 
the  branches  of  the  splenic  artery  and  its  branches,  investing  these  vessels  like, 
a  sheath.  These  two  systems  may  be  named,  respectively,  the  trabecular  and 
the  perivascular  lymphatics.     Occasionally,  the  latter  can  be  injected  from  the 


THE  ORGANS  ANNEXED  TO  ABDOMINAL  DIGESTIVE  CANAL.         507 

former.  The  perivascular  lymphatics  appear  to  arise  in  a  delicate  adenoid  tissue 
enclosing  the  smaller  arteries,  partly  from  a  plexus,  and  partly  from  lymph- 
cavities,  the  walls  of  which  are  formed  by  endothelial  cells  alone.  The  trabecular 
system  arises  in  a  plexus  lying  between  the  muscle-cell  fasciculi. 

There  is,  according  to  Kyber,  a  distinct  difference  between  the  splenic  pulp 
and  the  adenoid  tissue  surrounding  the  artery,  both  histologically  and  patho- 
logically. The  latter  he  regards  as  performing  the  usual  functions  of  the 
lymphatic  system  ;  while  the  former,  he  conceives,  may  exercise  that  digestive 
action  on  the  albuminoids  of  the  spleen,  which  Schiff  has  demonstrated  takes 
place.) 

Nerves. — They  are  derived  from  the  solar  plexus,  and,  enveloping  the  splenic 
artery,  with  it  enter  the  spleen.  (They  appear  to  be  very  large,  but  this 
appearance  is  due  to  the  great  proportion  of  ordinary  fibrous  tissue  investing 
them.) 

From  what  has-  been  said  above  respecting  the  arrangement  of  the  splenic 
arteries  and  veins,  it  will  be  perceived  that  the  areolae  formed  by  the  trabeculag 
of  the  fibrous  framework  contain  the  pulp,  and  are  not  in  direct  communication 
with  the  arterial  capillaries.  Such  an  organization  belongs  to  erectile  tissues. 
The  arteries  communicate  with  the  veins  proper  by  venous  canals  channeled  in 
the  splenic  pulp,  and  are  lined  only  by  an  endothelium  of  elliptical  cells.  These 
venous  canals  are  extremely  dilatable,  especially  in  the  Horse.  When  the  splenic 
vein  is  inflated,  their  walls  separate  and  press  back  the  pulp,  they  become  con- 
siderably enlarged,  and  distend  the  cells  of  the  fibrous  structure  ;  but  the  air 
does  not  reach  the  interior  of  these  cells. 

Functions. — Nothing  precise  is  known  regarding  the  functions  of  the  spleen  ; 
though  they  must  be  of  very  secondary  importance,  because  animals  in  which  the 
organ  has  been  extirpated,  and  which  have  recovered  from  the  operation,  have 
continued  to  live  in  apparent  good  health.  Numerous  hypotheses  have  been 
formed  on  this  subject  ;  two  of  which,  founded  on  the  study  of  the  anatomical 
peculiarities  of  the  spleen-tissue,  and  on  exact  physiological  observations,  are  as 
follows:  1.  TTie  spleen  is  a  diverticulum  for  the  portal  vein.  2.  The  red  corpuscles 
of  the  blood  are  destroyed  in  the  spleen. 

With  regard  to  the  first  hypothesis,  it  is  evident  that,  owing  to  the  presence 
of  the  venous  sinuses  already  mentioned,  and  their  great  dilatability,  as  well  as 
to  the  elasticity  and  contractility  of  the  spleen-tissue,  the  organ  is  favourably 
constructed  to  act  as  a  blood-reservoir.  Goubaux,  on  the  other  hand,  has 
demonstrated  that  there  is  always  an  augmentation  in  the  spleen's  volume  when 
an  animal  has  ingested  large  quantities  of  water,  the  consecutive  absorption  of 
which  determines  a  certain  tension  in  the  portal  venous  system. 

The  second  opinion,  emitted  by  Kolliker,  is  founded  on  the  existence  in  the 
splenic  pulp  of  blood- corpuscles  in  a  state  of  decomposition,  and  in  the  analyses 
.made  by  J.  Beclard  of  the  blood  in  the  splenic  vein,  which  have  proved  that 
there  is  a  notable  diminution  in  the  proportion  of  these.  These  analyses 
have,  however,  been  much  questioned,  and,  recently,  Malassez  and  Picard  have 
shown  results  which  are  in  favour  of  the  third  hypothesis.  They  have  found 
that  the  red  corpuscles  increase  in  the  blood  of  the  splenic  vein,  while  the 
proportion  of  iron  diminishes  in  the  pulp  ;  and  from  this  fact  they  conclude 
that  in  the  spleen  there  is  a  new  formation  of  corpuscles,  in  which  the  iron 
contained  in  the  splenic  pulp  participates. 

It  is  to  be  remarked  that,  in  the  researches  undertaken  to  discover  the 


508 


THE  DIGESTIVE  APPARATUS  IN   MAMMALIA. 


functions  of  the  spleen,  account  has  not  been  taken  of  the  connections  existing 
between  this  organ  and  the  great  omentum  in  the  majority  of  Mammals,  and 
which  testify  that  the  spleen  is  only,  properly  speaking,  a  vascular  appendage 
placed  on  the  course  of  this  omentum.  But  the  uses  of  this  vast  peritoneal  fold 
are  themselves  little  understood.  Might  they  not  be  included  with  those  which 
are  presumed  to  belong  to  its  appended  organ  ? 


Differential  Characters  in  the  Organs  Annexeti  to  the  Abdominal  Portion  of 
THE  Digestive  Canal  in  the  other  Animals. 


Fig.  302. 


The  important  diiferences  these  organs  offer  in  the  domesticated  Mammals  are  more 
particularly  observed  in  the  liver. 

1.  Liver. — In  the  domesticated  Mammals  other  than  Solipeds,  the  liver  exhibits  variations 
in  form,  volume,  and  position,  which  have  no  influence  on  its  organization :  so  that  the  study 
of  these  possesses  only  a  moderate  amount  of  interest.     This  is  not  so,  however,  with  regard 
to  the  excretory  apparatus,  the  arrangement  of  which  is  complicated,  and  becomes  very  inte- 
resting.    The  biliary  duct,  in  fact,  on  leaving  the  fissure 
of  the  portal  vein,  and  before  reaching  the  intestine, 
gives  rise  to  a  particular  conduit  which  is  detached  at  an 
acute  angle,  and  which,  after  a  course  of  variable  length, 
according  to  the  size  of  the  animal,  becomes  dilated  into 
a  vast  sac,  the  so-called  gall-bladder  (Figs.  302,  303). 

In  all  treatises  on  anatomy,  the  special  conduit  is 
designated  the  cyxtic  (or  bile)  duct,  that  portion  which 
precedes  its  origin  being  named  the  hepatic  duct;  while 
the  appellation  of  ductus  communis  choledochus  is  reserved 
for  the  section  which  goes  to  the  intestine.  But  these 
distinctions  are  vicious,  and  we  limit  ourselves  to  the 
recognition  of:  (a)  A  ductus  choledochus  exactly  like 
that  of  Solipeds,  and  like  it  extending  from  the  pos- 
terior fissure,  where  it  originates  by  the  union  of  several 
branches,  to  the  duodenum  ;  and  (b)  a  cystic  duct,  which 
branches  suddenly  into  the  choledic  duct,  and  terminates 
in  the  gall-bladder. 

a.  The  gall-bladder  (Fig.  302,  1)  is  a  reservoir  with 
membranous  walls,  in  which  the  bile  accumulates  during 
the  intervals  of  digestion.  This  sac,  lodged  wholly,  or 
in  part,  in  a  fossa  on  the  posterior  face  of  the  liver,  is 
oval  or  pyriform,  and  presents  a  fundus  and  neck.  Its 
parietes  comprise  three  tunics:  an  external,  of  peri- 
toneum; a  middle,  formed  of  fibrous  tissue;  and  an 
internal,  or  mucous,  continuous  with  that  of  the  various 
biliary  ducts. 

b.  Tiie  cystic  duct  (Fig.  302,  2)  extends  in  a  straight 
line  from  the  neck  of  the  gall-bladder  to  the  choledic 
duct.     It  adheres  intimately  to  the  tissue  of  the  liver, 

and  does  not  exhibit,  internally,  tiie  spiral  valves  which  have  been  described  in  Man.  In 
opening  it  longitudinally,  tiiere  are  discovered,  at  least  in  Ruminants  and  the  Carnivora,  very 
small  orifices  which  pierce  the  wall  adherent  to  the  tissue  of  the  liver:  these  are  the  openings . 
of  several  minute,  but  special,  biliary  canals,  named  the  hepatico-ctjstic  ducts. 

c.  The  ductus  communis  choledochus  (Fig.  302, 3)  comports  itself  exactly  iis  in  Solipeds.  It  is 
much  wider  than  the  cystic  duct,  and  opens  sometimes  alone,  sometimes  with  the  pancreatic 
canal,  into  the  duodenum  in  a  manner  which,  up  to  a  certain  point,  reminds  one  of  the  moile 
of  termination  of  the  ureters.  Instead  of  passing  perpendicularly  across  the  intestinal  parietes, 
it  first  pierces  the  muscular  layer,  follows  for  a  short  distance  between  it  and  the  mucous 
membrane,  and  then  opens  on  the  internal  face  of  the  latter  by  an  orifice  which  is  encircled 
by  a  valvular  fold,  as  in  the  Horse. 

Such  is  the  excretory  apparatus  belonging  to  the  liver  in  animals  provided  with  a  gall- 
bladder.    In  these  animals  the  biliary  secretion  is  certainly  continuous,  as  in  the  Horse;  but 


LIVER   OF   THE  OX. 

,  Interior  extremity  of  the  liver; 
B,  superior  extremity  ;  C,  Spigelian 
(caudate)  lobe.  1,  Gall-bladder; 
2,  cystic  duct;  3,  ductus  chole- 
dochus ;  4,  root  of  that  duct ;  5, 
posterior  vena  cava  ;  7,  intestine ; 
8,  insertion  of  the  pancreatic  duct. 


THE  ORGANS  ANNEXED   TO  ABDOMINAL  DIGESTIVE  CANAL. 


509 


in  the  intervals  of  digestion,  the  bile,  instead  of  flowing  directly  on  to  the  intestinal  surface, 
passes  into  the  gall-bladder  by  the  cystic  duct,  and  there  accumulates.  When  digestion 
commences  again,  this  reserve  of  bile  is  thrown  into  the  ductus  choledochus  by  the  contraction 
of  the  muscular  fibres  of  tlie  cyst,  and  by  the  pressure  of  the  abdominal  viscera;  it  meets  that 
which  comes  directly  from  the  liver,  and  with  it  is  carried  to  the  duodenum. 

We  will  now  glance  at  the  particular  arrangement  of  this  viscus  in  each  species. 

In  the  Ox,  the  liver  is  entirely  confined  to  the  right  diaphragmatic  region.  It  is  thick, 
voluminous,  and  scarcely  notched  at  its  periphery ;  so  that  it  is  difficult,  if  not  impossible,  to 
distinguish  three  lobes  in  it.  In  Fig.  302,  this  excretory  apparatus  is  represented,  the  lobus 
Spigelii  alone  being  detached  from  the  mass  of  the  organ.    The  gall-bladder,  fixed  towards 


LIVER  OF   THE   DOG,    WITH   ITS   EXCRETORY   APPARATUS. 

D,  Duodenum  and  the  intestinal  mass ;  p,  pancreas ;  r,  spleen ;  e,  stomach ;  /,  rectum ;  R,  right 
kidney  5  B,  gall-bladder;  ch,  cystic  duct;  f  f,  liver;  f',  lobe  of  the  liver,  prepared  to  show  the 
distribution  of  the  vena  portse  and  hepatic  vein  ;  vp,  vena  portsB ;  vh,  hepatic  vein ;  d,  diaphragm; 
VC,  vena  cava ;  C,  heart. 


the  superior  extremity,  is  nearly  always  floating ;  near  its  neck  it  receives  the  insertion  of 
several  large  conduits,  which  come  directly  from  the  upper  part  of  the  liver.  The  ductus 
choledochus  opens  alone  at  a  great  distance  from  the  pylorus;  Colin  has  found  it  to  be  24^ 
inches  in  one  cow,  and  29|  inches  in  another.  In  the  Sheep  and  Goat,  the  form  and  position 
of  the  liver  differs  but  little  from  that  of  the  Ox.  The  ductus  choledochus,  however,  unites 
with  that  of  the  pancreas,  and  terminates  at  from  12  to  16  inches  from  the  pylorus. 

In  the  Camel,  the  liver  has  the  same  arrangement  as  in  the  other  Ruminants,  except  that 
Its  posterior  face  is  divided,  lobulated,  and  much  reticulated. 

In  the  Pig,  the  liver  has  three  well-marked  lobes ;  the  middle  carries  the  gall-bladder- 
The  ductus  choledochus  opens  alone  at  1  or  1§  inches  only  from  the  pylorus. 
35 


510 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


In  the  Dog  and  Cat,  the  liver  is  very  voluminous,  is  deeply  notched,  and  is  divided  into 
five  principal  lobes.  The  middle  lobe  has  the  gall-bladder  attached  to  it,  and  gives  it  complete 
lodgment  in  a  fossa. 

In  the  Dog,  the  ductus  choledochus,  joined  to  a  small  branch  from  the  pancreatic  duct, 
enters  the  intestine  at  a  variable  distance  from  the  pylorus,  depending  upon  the  size  of  the 
animal,  but  usually  between  IJ  and  4f  incht  s.  In  the  portion  comprised  between  the  intestine 
and  the  origin  of  the  cystic  duct,  it  receives  several  biliary  canals  of  somewhat  considerable 
diameter.  In  the  Cat,  the  ductus  choledochus  is  most  frequently  inserted  from  about  1  to  IJ 
inches  from  the  pyloric  orifice;  it  opens  immediately  alongside  the  pancreatic  duct,  when  it 
does  not  join  it.  ■         u      • 

2.  Pancreas.-  In  the  Ox,  the  pancreas  is  not  placed  across  the  sublumbar  parietes,  but  is 
comprised  between  th.-  layers  of  the  mesentery,  to  the  right  of  the  great  mesenteric  artery. 
The  excretory  duct  is  single,  and  opens  into  the  small  intestine  at  from  14  to  16  inches  beyond 
the  ductus  choledochus. 

In  the  Sheep  and  Goat,  there  is  the  same  general  arrangement,  but  the  excretory  ducts 
opens  with  that  of  the  liver. 

In  the  Pig,  a  portion  of  the  pancreas  is  situated  in  the  sublumbar  region,  between  the 
large  tuberosity  of  the  stomach  and  the  last  fiexure  of  the  colon  ;  the  other  portion  is  lodged 

in  the   duodenal  fraenum.     The   duct  of 


Fig.  304. 


UNDER   SURFACE   OF   THE   HUMAN   LIVER. 

1,  Right  lobe ;  2,  left  lobe ;  3,  lobus  quadratus ;  4, 
lobus  Spigelii;  5,  lobus  caudatus ;  6,  longitudinal 
fossa ;  7,  pons  hepatis  ;  8,  fossa  of  ductus  venosus ; 
9,  inferior  vena  cava;  10.  gall-bladder;  11,  trans- 
verse fossa;  12,  vena  cava;  13,  depression  corre- 
sponding to  the  curve  of  the  colon;  14,  double 
depression  produced  by  right  kidney  and  supra- 
renal capsule. 


Wirsung  is  inserteil  at  from  4  to  6  inches 
behind  the  ductus  choledochus. 

The  pancreas  of  the  Dog  is  extremely 
elongated,  and  included  between  the  layers 
of  the  mesentery  which  sustain  the  duo- 
denum. It  is  curved  at  its  anterior  ex- 
tremity, beliind  the  stomach,  to  one  side 
of  tlie  median  line.  Its  excretory  duct — 
usually  single — pierces  the  intestinal  mem- 
branes 2  inches  beyond  the  hepatic  duct 
(Fig.  290,  m).  Except  in  the  mode  of 
insertion  of  the  excretory  duct,  which  has 
been  described  in  noticing  the  ductus 
choledochus,  the  pancreas  of  the  Cat  com- 
ports itself  exactly  like  that  of  the  Dog. 

3.  Spleen.— In  Ruminants,  the  spleen 
is  not  supported  by  the  great  omentum,  but 
adheres  to  the  left  side  of  the  rumen  and 
diaphragm.  It  is  not  falciform,  and  its 
breadth  is  the  same  througliout  its  extent. 
In  the  Camivora,  it  is  suspended  to  the 
great  omentum  at  a  certain  distance  from 
the  left  sac  of  the  stomach.  It  is  irregu- 
larly falciform,  its  point  is  less  acute  than 
in  Solipeds,  and  is  directed  upwards. 


Comparison  between  the  Annexed  Organs  of  the  Abdominal  Portion  of  the 
Digestive  Canal  in  Man  with  those  of  Animals. 


1.  Liver.— hike  that  of  Ruminants,  the  liver  of  Man  is  situated  in  the  right  excavation 
of  the  lower  face  of  the  diaphragm.  Its  direction  is  nearly  horizontal ;  its  shape  is  oval, 
and  its  average  weight  from  49  to  53  ounces.  The  posterior  border  is  thick  and  round; 
the  anterior  border  and  extremities  thin  and  sharp.  The  upper  face,  which  in  i-xpiration 
ascends  to  the  fourth  rib,  is  divided  into  two  portions  or  lobes— right  and  left,  by  the  falciform 
ligament :  it  is  smooth  and  convex.  The  inferior  face  has  three  furrows,  or  fossae  :  two  longi- 
tudinal, united  by  a  transverse,  resembling  altogether  tlie  letter  H.  The  traiisverse  furrow 
represents  that  on  the  posterior  aspect  of  the  liver  of  animals,  and  its  destination  is  the  same. 
The  right  longitudinal  furrow  lodges  the  obliterated  umbilical  vein  ;  the  left,  well  marked 
before  and  behind,  lodges  the  gall-bladder  in  front,  and  the  inferior  vena  cava  behind.  This 
ftice  has  four  lobes,  the  right  and  left,  and  two  middle  lobes.  In  front  of  the  transverse  furrow 
is  the  lobus  quadratus,  and  behind  the  same  fissure  is  the  lobus  Spigelii. 


TEE  DIGESTIVE  APPARATUS  OF  BIRDS.  511 

Nothing  is  to  be  said  of  its  structure,  and  the  arraugeiBent  of  its  excretory  apparatus  is 
identical  with  that  of  the  Ox. 

On  the  lower  face  of  the  right  lobe  are  three  depressions:  au  anterior  or  impressw  colica;  a 
deep  middle  one,  impressio  vesicse ;  and  a  small  posterior  one,  which  receives  the  supra-renal 
capsules,  impressio  renalis. 

2.  Pancreas.— This  organ  is  very  elongated  transversely,  like  that  of  the  Dog  and  Cat.  It 
is  closely  applied  against  the  lumbar  vertebrae,  as  in  the  Horse,  bijt  its  anterior  face  is  much 
more  enveloped  by  the  peritoneum.  Its  right  extremity  rests  on  the  duodenum,  while  the  left 
corresponds  to  the  spleen  and  left  kidney.  Its  texture  is  consistent,  and  of  a  greyish-white 
colour.  The  duct  of  Wirsung  terminates,  along  with  the  ductus  choledochus,  in  the  ampulla 
of  Vater. 

3.  Spleen. — This  is  not  falciform,  but  quadrangular ;  its  inferior  extremity  is  larger  than 
the  superior.  It  is  attached  to  the  stomach  by  the  great  omentum,  and  its  inner  face  is  divided 
into  two  portions  by  a  salient  ridge ;  a  little  in  front  of  this  is  a  fissure — the  hilum  lienit — 
by  which  vessels  enter  it. 


CHAPTEK  III. 

The  Digestive  Apparatus  of  Birds. 

Constructed  on  the  same  plan  as  that  of  Mammals,  the  digestive  apparatus  of 
Birds  nevertheless  offers  in  its  arrangement  several  important  peculiarities, 
which  will  be  hurriedly  noticed  in  reviewing,  from  the  mouth  to  the  anus,  its 
different  sections. 

Mouth. — The  essentially  distinctive  character  of  the  mouth  of  Birds  consists 
in  the  absence  of  lips  and  teeth,  these  organs  being  replaced  by  a  horny  production 
fixed  to  each  jaw,  and  forming  the  salient  part  termed  the  heak.  In  the  Gallinam^ 
the  beak  is  short,  pointed,  thick,  and  strong,  the  upper  mandible  being  curved 
over  the  lower.  In  Palmipeds,  it  is  longer,  weaker,  flattened  above  and  below, 
widened  at  its  free  extremity,  and  furnished  within  the  mouth,  on  the  borders  of 
each  mandible,  with  a  series  of  thin  and  sharp  transverse  laminae  to  cut  the 
herbage. 

The  muscular  appendage,  or  tongue,  lodged  in  the  buccal  cavity,  is  suspended 
to  a  remarkably  mobile  hyoidean  apparatus.  Covered  by  a  horny  epithelium, 
and  provided  at  its  base  with  several  papillae  directed  backwards,  this  organ 
always  affects  the  form  of  the  lower  jaw  :  in  Poultry  it  is  like  the  barbed  head 
of  an  arrow,  the  point  being  directed  forwards  ;  in  Pigeons  this  saggital  form 
is  still  more  marked  :  in  Geese  and  Ducks,  on  the  contrary,  and  in  consequence 
of  the  wide  shape  of  the  beak,  it  has  not  this  disposition,  and  is  softer  and  more 
flexible  than  in  the  GalKnacse, 

With  regard  to  the  salivary  glands  annexed  to  the  mouth,  they  are  imperfectly 
developed,  the  presence  of  the  fluids  they  secrete  being  less  necessary  in  Birds 
than  in  Mammals,  as  the  food  is  nearly  always  swallowed  without  undergoing 
mastication  ;  consequently  insaUvation  is  all  but  useless. 

Gurlt  ^  speaks  of  a  parotid  gland  situated  beneath  the  zygomatic  arch,  the  duct 
of  which  opens  into  the  mouth  behind  the  commissm-e  of  the  jaws.  Meckel  names 
this  organ  the  angular  gland  of  the  mouth,  and  says  that  it  is  difficult  to  regard  it 

'  GturM,  Anatomie  der  Hausyogel.     Berlin:  1849. 


512  THE  DIGESTIVE  APPARATUS  OF  BIRDS. 

as  representing  the  parotids,  any  more  than  the  glands  of  the  cheeks  and  lips. 
Duvernoy  ^  categorically  assimilates  it  with  the  latter. 

The  sublingual  glands  lie  in  the  median  line  throughout  nearly  their  whole 
extent,  and  form  an  apparently  single  and  conical  mass,  whose  apex  occupies  the 
re-entering  angle  formed  by  the  union  of  the  two  branches  of  the  lower  maxilla. 

According  to  Duvernoy,  the  submaxillary  glands  are  represented  by  two  very 
small  organs  situated  behind  the  preceding.  Their  existence,  however,  is  far 
from  being  general ;  for  among  common  poultry,  the  Turkey  was  the  only  bird 
in  which  Duvernoy  observed  these  submaxillary  glands. 

Pharynx  (Fig.  305,  2). — This  cavity  is  not  distinct  from  the  mouth,  the 
soft  palate  being  entirely  absent  in  Birds.  On  its  superior  wall  may  be  remarked 
the  guttural  orifice  of  the  nasal  cavities  :  a  longitudinal  slit  divided  into  two 
by  the  inferior  border  of  the  vomer.  Below  is  another  less  extensive  slit,  the 
entrance  to  the  larynx,  and  which  is  remarkable  for  the  complete  absence  of  the 
epiglottidean  operculum. 

(Esophagus. — This  canal  is  distinguished  by  its  enormous  calibre  and  great 
expansibility.  Its  walls  are  very  thin,  and  contain  in  their  substance  lenticular 
glands,  easily  seen  in  an  inflated  oesophagus,  in  consequence  of  the  tenuity  and 
transparency  of  its  textures. 

At  its  origin,  the  oesophageal  canal  is  not  separated  from  the  pharynx  by  any 
constriction  ;  in  its  course  it  lies  alongside  the  long  muscle  of  the  neck,  and  the 
trachea  ;  its  terminal  extremity  is  inserted  into  the  first  compartment  of  the 
stomach,  or  succentric  ventricle,  after  entering  the  thorax  and  passing  above 
the  origin  of  the  bronchi,  between  their  two  branches. 

In  Palmipeds,  the  oesophagus  is  dilated  in  its  cervical  portion  in  such  a 
manner  as  to  form,  when  its  walls  are  distended,  a  long  fusiform  cavity. 

In  Gallinacce  (Fig.  305,  3,  4,  5),  this  dilatation  does  not  exist ;  but  the 
oesophagus  presents  in  its  course,  and  immediately  before  entering  the  chest,  an 
ovoid  membranous  pouch  named  the  crop  (or  iiigluvies).  In  the  oesophagus  of 
these  Birds,  then,  we  find  two  distinct  sections,  joined  end  to  end — one  superior 
or  cervical,  the  other  inferior  or  thoracic  on  the  limit  of  which  is  the  crop.  The 
latter  does  not  differ  in  its  structure  from  the  oesophagus,  and  is  a  temporary 
reservoir  for  the  food  swallowed  by  the  animal  during  its  meal,  and  where  it  is 
softened  by  being  impregnated  with  a  certain  quantity  of  fluid  ;  after  which  it  is 
passed  into  the  succentric  ventricle  by  the  contractions  of  the  external  membrane 
of  the  crop,  aided  by  a  wide  subcutaneous  cervicle  muscle  which  covers  that 
reservoir. 

In  Pigeons,  the  crop  is  also  present ;  but  it  is  divided  into  two  lateral 
pouches,  and  exhibits  glandular  eminences  towards  the  common  inferior  opening 
of  these  sacs  into  the  oesophagus  {aquiparous  glands).  Singular  changes  are 
observed  in  the  apparent  structure  of  its  walls  in  the  male  as  well  as  lq  the 
female,  from  the  eighth  to  the  twentieth  day  of  incubation,  or  during  the  first 
weeks  after  hatching,  which  coincide  with  the  appearance  of  a  kind  of  secretion 
which,  when  regurgitated,  serves  to  nourish  the  young  birds.  At  this  period, 
the  membranes  of  the  crop  become  thickened  ;  the  vessels,  more  numerous  and 
more  apparent,  are  redder,  and  the  glands  more  developed  ;  the  folds  or  ridges 
of  the  mucous  membrane  become  more  marked,  and  in  their  interspaces  are  deep 
depressions  where  an  apparently  milky  fluid  accumulates,  and  which  is  derived 
from  the  active  proliferation  of  the  epithelium  and  its  concomitant  fatty 
'  Cuvier,  Anatomie  Cum,par€e.     2nd  Edition.     Paris :  1836. 


THE  DIGESTIVE  APPARATUS   OF  BIRDS. 


513 


degeneration.     There  are  no  permanent  glands  for  this  secretion.^ 
exclusively  nourish  their  yoimg  with  this  fluid  during  the  first  three  days  of  "their 


existence. 


F5g.  305. 

GENERAL   VIEW   OF   THE   DIGES- 
TIVE  APPARATUS  OF   A   FOWL. 

The  abdominal  muscles  have  been 
removed,  as  well  as  the  ster- 
num, heart,  trachea,  the  greater 
portion  of  the  neck,  and  all 
the  head  except  the  lower  jaw, 
which  has  been  turned  aside  to 
show  the  tongue,  the  pharynx, 
and  the  entrance  tn  the  larynx. 
The  left  lobe  of  the  liver,  suc- 
centric  ventricle,  gizzard,  and 
intestinal  mass,  have  been 
pushed  to  the  right  to  exhibit 
the  diiferent  portions  of  the 
alimentary  canal,  and  to  ex- 
pose the  ovary  and  oviduct. 

1,  Tongue ;  2,  pharynx ;  3,  first 
portion  of  the  oesophagus ;  4, 
crop;  5,  second  portion  of  the 
(Esophagus;  6,  succentric  ven- 
tricle ;  7,  gizzard ;  8,  origin 
of  the  duodenum ;  9,  first 
branch  of  the  duodenal  flex- 
ure ;  10,  second  branch  of  the 
same;  11,  origin  of  the  float- 
ing portion  of  the  small  in- 
testine;  12,  small  intestine; 
12',  terminal  portion  of  this 
intestine,  flanked  on  each  side 
by  the  two  caeca  (regarded  as 
the  analogue  of  the  colon  of 
mammals);  13,  13,  free  ex- 
tremities of  the  caeca;  14, 
insertion  of  these  two  culs-de- 
sac  into  the  intestinal  tube; 
15,  rectum ;  16,  cloaca ;  17, 
anus;  18,  mesentery;  19,  left 
lobe  of  the  liver; '20,  right 
lobe;  21,  gall-bladder;  22, 
insertion  of  the  pancreatic  and 
biliary  ducts ;  the  two  pan- 
creatic ducts  are  the  anterior- 
most,  the  choledic  or  hepatic 
is  in  the  middle,  and  the  cystic 
duct  is  posterior;  23,  pancreas; 
24,  diaphragmatic  aspect  of 
the  lung  ;  25,  ovary  (in  a  state 
of  atrophy) ;  26,  oviduct. 


"  Hunter,  Observations  on  certain  parts  of  the  Animal  Mconomy.  London :  1792.  Duvernoy, 
inG.  Q,\xyKX,Legons  d'Anatomie  Comparee.  2nd  Edition.  Paris:  1836.  Charbonelle-Salle 
and  Phisalix,  Sur  la  Secretion  Lact€e  de  Pigeons  en  Incubation,  in  Comptes  Rendu  de  I'Academie 
des  Sciences.     1886. 


514  THE  DIGESTIVE  APPARATUS   OF  BIRDS. 

Stomach. — The  stomach  presents  numerous  variations  in  Birds.  Its  simplest 
form  is  seen  in  the  Heron,  Pelican,  Petrels,  etc.,  where  it  is  a  single  sac  provided 
with  a  thick  zone  of  glands  around  the  entrance  of  the  oesophagus,  which  secrete 
the  gastric  juice.  But  in  the  majority  of  the  other  species,  and  particularly  in 
our  domesticated  Birds,  the  disposition  of  the  stomach  is  modified  and  comphcated ; 
the  glandular  zone  destined  for  the  gastric  secretion  forms  a  special  compartment 
— the  surcentric  ventricle,  and  this  is  followed  by  a  second  reservoir — the  gizzard, 
which  is  remarkable  for  the  strong  muscular  constitution  of  its  walls.  The  first 
is  also  named  the  glandular  stomach,  and  the  second  the  muscular  stomach. 

Glandular  stomach,  or  succentric  ventricle  {proventriculus)  (Fig.  305,  6). — This 
is  an  ovoid  sac  placed  in  the  median  plane  of  the  body,  between  the  two  lobes  of 
the  liver,  and  beneath  the  aorta.  Its  anterior  extremity  receives  the  insertion 
of  the  oesophagus  ;  the  posterior  is  continued  by  the  gizzard.  The  volume  of 
this  stomach  is  inconsiderable,  and  its  cavity  is  very  narrow  ;  the  aliment  does 
not  accumulate  in  it,  but  merely  passes  through,  carrying  with  it  the  acid  juice 
which  afterwards  dissolves  its  protein  elements.  Its  walls  have  three  tunics  :  an 
external  or  peritoneal ;  a  middle,  formed  of  white  muscular  fibres,  continuous 
with  those  of  the  oesophagus  ;  and  an  internal,  of  a  mucous  nature,  perforated 
by  orifices  for  the  passage  of  the  gastric  juice.  These  are  small  cylinders  placed 
perpendicularly  to  the  surface  of  the  stomach,  closely  laid  against  one  another, 
like  the  microscopic  glands  of  Lieberkiihn,  and  contained  in  the  connective  tissue 
layer  uniting  the  inner  to  the  middle  tunic.  The  glandular  structure  of  this 
receptacle  caused  it  to  be  regarded  as  the  true  stomach  in  Birds  ;  but  Jobert  has 
shown  that  the  real  gastric  juice  is  secreted  in  the  gizzard. 

Gizzard  or  muscular  stomach  {ventricidus  bulbosus)  (Fig.  305,  7). — Much 
more  voluminous  than  the  preceding,  this  stomach  is  oval  in  form,  depressed  on 
each  side,  and  situated  behind  the  liver,  being  partly  covered  by  the  lateral  lobes 
of  that  gland.  Above,  and  to  the  right,  and  at  a  short  distance  from  each  other, 
are  seen  the  insertion  of  the  succentric  ventricle  and  the  origin  of  the  duodenum. 
The  cavity  of  the  gizzard  always  contains  food  mixed  with  a  large  quantity  of 
silicious  pebbles,  the  use  of  which  will  be  indicated  hereafter. 

This  viscus  is  composed  of  the  three  timics  which  form  the  walls  of  all  the 
abdominal  reservoirs.  The  internal,  or  mucous,  is  distinguished  by  the  thickness 
and  extraordinary  induration  of  its  epidermic  layer,  which  presents  nearly  all  the 
characters  of  horny  tissue,  and  which  results  from  the  accumulation  of  the 
products  secreted  by  the  epithelium.  The  latter  is  spheroidal,  and  is  so  easily 
detached  from  the  mucous  chorium  that  it  is  often  regarded  as  a  special 
membrane.  On  the  adherent  face  of  this  corium  are  applied  two  powerful  red 
muscles — a  superior  and  inferior,  occupying  the  borders  of  the  organ,  and  whose 
fibres,  disposed  in  flexures,  pass  from  side  to  side,  and  are  inserted  into  a  strong, 
nacrous  aponeurosis  on  the  lateral  surfaces  of  the  organ.  Outside  this  contractile 
apparatus  is  a  thin  peritoneal  envelope. 

The  gizzard  is  the  triturating  apparatus  of  Birds.  "When  the  aliment  reaches 
its  cavity  it  has  not  yet  submitted  to  any  disaggregation,  but  here  it  meets  with 
all  the  conditions  indispensable  for  the  accomplishment  of  this  act :  two  energetic 
compressor  muscles,  a  corneous  layer  spread  over  the  internal  surface  of  the 
viscera,  giving  to  it  the  rigidity  necessary  to  resist  the  enormous  pressure  exercised 
on  its  contents ;  and  silicious  pebbles — veritable  artificial  teeth — which  an 
admirable  instinct  causes  Birds  to  swallow,  and  between  which,  by  the  effort 
of  the  triturating  muscles,  the  food  is  bruised.     This  triturating  action  of  the 


THE  DIGESTIVE  APPARATUS  OF  BIRDS.  515 

gizzard  is  only  effected  in  Birds  fed  on  hard  coriaceous  aliment,  such  as  the 
various  kinds  of  grain.  It  would  be  useless  in  Birds  of  prey,  in  which  the  two 
gizzard  muscles  are  replaced  by  a  thin  fleshy  membrane  of  uniform  thickness — 
showing  that  the  presence  of  these  muscles  is  subordinate  to  the  kind  of  ahmentation. 

Intestine. — The  length  of  the  intestine  varies,  as  in  Mammals,  according  to 
the  nature  of  the  food  :  very  short  in  Birds  of  prey,  it  is  notably  elongated  in 
omnivorous  and  granivorous  Birds.  Its  diameter  is  nearly  uniform  throughout 
its  whole  extent,  and  it  is  difficult  to  establish  in  Birds  the  various  distinctions 
recognized  in  the  intestine  of  Mammalia.  It  begins  by  a  portion  curved  in  a 
loop,  which  represents  the  duodenum,  the  two  branches  of  which,  lying  side  by 
side,  are  parallel  to  each  other,  like  the  cohc  flexure  of  Solipeds.  Fixed  by  a 
short  mesenteric  frsenum  to  the  colon,  this  part  of  the  intestine  includes  the 
pancreas  between  its  two  branches.  Its  curvature  floats  freely  in  the  pelvic 
portion  of  the  abdominal  cavity  (Fig.  305,  8,  9,  10). 

To  the  duodenal  loop  succeed  convolutions  suspended  to  the  sublumbar  parietes 
by  a  long  mesentery,  and  which  are  rolled  up  into  a  single  mass,  elongated  from 
before  to  behind,  occupying  a  middle  position  between  the  air-sacs  of  the 
abdominal  cavity.  The  analogy  existing  between  this  mass  of  convolutions,  and 
ths,  floating  portion  of  the  small  intestine  of  Mammals,  does  not  require  demonstration 
(Fig.  305,  11,  12). 

The  terminal  part  of  this  floating  intestine  lies  beside  the  duodenal  loop,  and 
is  flanked  by  the  two  appendages  disposed  like  cceca.  These,  scarcely  marked  in 
the  Pigeon  by  two  small  tubercles  placed  on  the  track  of  the  intestinal  tube,  do 
not  measure  less  than  from  6  to  10  inches  in  the  other  domesticated  Birds ; 
they  are  two  narrow  culs-de-sac,  slightly  club-shaped  at  their  closed  extremities, 
which  are  free  and  directed  towards  the  origin  of  the  intestine,  while  the  other 
extremity  opens  into  the  intestinal  canal  near  the  anus.  There  are  always 
alimentary  matters  in  these  sacs,  these  becoming  introduced,  in  following  a 
retrograde  course,  by  the  same  almost  unknown  mechanism  which  presides  over 
the  accumulation  of  spermatic  fluid  in  the  vesiculae  seminales.  According  to  the 
majority  of  naturalists,  these  two  appendages,  although  described  as  cceca,  do  not 
represent  the  reservoir  bearing  that  designation  in  Mammals.  This  reservoir  is 
nothing  more  than  a  small  special  appendix  placed  on  the  track  of  the  intestine, 
in  front  of  the  free  extremity  of  the  above-mentioned  culs-de-sac,  and  is  only  to 
be  found  in  a  small  number  of  Birds,  and  among  these  sometimes,  as  Gurlt^ 
affirms,  is  the  Goose.  According  to  this  view,  which  appears  to  be  a  very 
rational  one,  the  portion  of  intestine  comprised  between  the  two  blind  tubes 
annexed  to  the  viscera  (Fig.  305,  12')  corresponds  to  the  colon,  and  these  tubes 
themselves  are  only  dependencies  of  this  intestine. 

The  rectum  (Fig.  305,  15)  terminates  the  digestive  canal ;  it  is  the  short 
portion  of  intestine  that  follows  the  opening  of  the  caeca.  Placed  in  the 
sublumbar  region,  this  viscus  is  terminated  by  a  dilatation,  the  cloaca  (Fig.  305, 
16),  a  vestibule  common  to  the  digestive  and  genito-urinary  passages,  which 
opens  externally  at  the  anus,  lodges  the  penis  when  it  exists,  and  serves  as  a 
confluent  for  the  ureters,  oviduct,  bursa  of  Fabricius,  and  the  deferent  canals. 

Abdominal  Appendages  of  the  Digestive  Canal. — Lirer  (Fig.  305,  19, 

20). — This  is  a  voluminous  gland,  divided  into  two  principal  lobes — a  right  and 

left,  the  former  always  larger  than  the  latter ;   these  incompletely  include,  on 

each  side,  the  gizzard  and  succentric  ventricle.     In  the  Pigeon,  this  gland  is 

»  Gurit,  Op.  cit 


516  TEE  DIGESTIVE  APPARATUS   VF  BIRDS. 

provided  with  a  gall-bladder  (Fig.  305,  21)  attached  to  the  internal  face  of  the 
right  lobe.  But  the  arrangement  of  the  excretory  apparatus  is  not  altogether 
identical  with  that  observed  in  Mammals  which  possess  thi^  receptacle  ;  as  two 
biliary  ducts  open  separately  into  the  intestine  towards  the  extremity  of  the 
second  branch  of  the  duodenal  loop.  One  proceeding  directly  from  the  two 
lobes  of  the  liver,  is  the  hepatic  or  choledic  dud;  the  other,  the  cystic  duct, 
remains  independent  of  the  latter,  and  opens  behind  it.  It  carries  into  the 
digestive  canal  the  bile  accumulated  in  the  gall-bladder,  and  which  arrives  there 
by  a  particular  duct  belonging  exclusively  to  the  right  lobe  ;  the  cystic  canal  is 
a  branch  of  this  duct  (Fig.  305,  22). 

Pancreas  (Fig.  305,  23). — In  the  GaUinacce,  this  gland  is  very  developed, 
long,  and  narrow,  and  is  comprised  in  the  duodenal  loop  or  flexm-e ;  at  the 
extremity  next  the  gizzard  it  has  two  principal  excretory  ducts,  which  separately 
pierce  the  intestinal  membranes,  a  little  in  front  of  the  hepatic  duct. 

Spleen. — This  is  a  small,  red-coloured,  disc-shaped  body,  placed  to  the  right 
of  the  stomachs,  on  the  limit  of  the  gizzard  and  succentric  ventricle. 


BOOK  III. 

Respiratory  Apparatus. 

The  maintenance  of  life  in  animals  not  only  requires  the  absorption  of  the 
organizable  and  nutritive  matters  conveyed  to  the  internal  surface  of  the 
digestive  canal,  but  demands  that  another  principle — the  oxygen  of  the  atmo- 
sphere— should  enter  with  these  materials  into  the  circulation.  In  animals  with 
red  blood,  this  element,  in  mixing  with  the  nutritive  fluid,  commences  by 
expelling  an  excrementitial  gas — carbonic  acid — and  communicating  a  bright  red 
colour  to  that  fluid,  with  which  it  circulates  ;  it  is  brought  into  contact,  in  the 
general  capillary  system,  with  the  minute  structures  of  the  various  apparatuses, 
exercising  on  the  organic  matter  composing  them  a  particular  stimulating 
influence,  without  which  the  tissues  could  not  manifest  their  properties,  as  well 
as  inducing  a  combustible  action  which  evolves  the  heat  proper  to  the  animal 
body. 

This  new  absorption  constitutes  the  phenomenon  of  respiration.  In  the 
Mammalia,  this  is  effected  in  the  lungs — parenchymatous  organs  chambered  into 
a  multitude  of  vesicular  spaces,  which  receive  the  air  and  expel  it,  after  depriving 
it  of  a  certain  quantity  of  oxygen,  and  giving,  in  return,  a  proportionate  quantity 
of  carbonic  acid.  These  organs  are  lodged  in  the  thoracic  cavity,  the  alternate 
movements  of  dilatation  and  contraction  of  which  they  follow.  They  com- 
municate with  the  external  air  by  two  series  of  canals  placed  end  to  end  :  1.  A 
cartilaginous  tube  originating  in  the  pharyngeal  vestibule,  and  ramifying  in  the 
lungs.  2.  The  nasal  cavities,  two  fossae  opening  into  that  vestibule,  and  com- 
mencing by  two  openings  at  the  anterior  extremity  of  the  head. 


CHAPTER  I. 

RESPIRATORY  APPARATUS  IN  MAMMALIA. 

In  this  apparatus  we  will  first  study  the  organs  external  to  the  thoracic  cavity — 
the  nasal  cavities,  and  larynx  and  trachea;  then  the  chest  and  the  organ  it 
contains — the  lung. 

To  this  study  will  be  added  that  of  the  two  glandiform  organs,  the  uses  of 
which  are  unknown,  but  by  their  anatomical  connections  they  belong  to  the 
respiratory  apparatus.     These  are  the  thyroid  bodies  and  the  thymus  gland. 


518 


RESPIRATORY  APPARATUS  IN  MAMMALIA. 


The  Nasal  Cavities. 

These  cavities  are  two  in  number — a  right  and  left — and  offer  for  study  :  their 
entrance,  or  nostrils — the  fossce,  properly  called,  which  constitute  these  cavities  ; 
and  the  diverticuli  named  sinuses. 

Preparation. — Remove  the  lower  jaw  from  three  heads.  On  the  first  of  these  make  two 
transverse  sections,  one  passing  between  the  second  and  third  molar  tooth,  the  other  behind 
the  dental  arch.  Saw  through  the  second  head  longitudinally  and  vertically,  a  little  to  one 
side  of  the  median  line.  On  the  third  make  a  horizontal  section  in  such  a  manner  as  to  obtain 
an  inferior  portion  analogous  to  that  shown  in  Fig.  41.  On  this  the  organ  of  Jacobson  may 
be  studied. 


Fig.  306. 


1.  The  Nosteils. 

The  nostrils  (or  anterior  or  inferior  nares)  are  two  oblong,  lateral  openings, 
situated  at  the  extremity  of  the  nose,  circumscribed  by  lips  or  movable  ivings 
(alee)  disposed  in  an  obhque  direction  downwards  and  inwards,  and  slightly 
curved  on  themselves,  so  as  to  present  theu'  concavity  to  the  external  side. 

The  lips  or  alee  of  the  nostril  are  enveloped,  inwardly  and  outwardly,  by  a 
thin,  delicate  skin,  covered  by  fine,  short  hairs.  The  external  is  concave  on  its 
free  margin  ;  the  internal  is  convex.  The  commissure  which  unites  these  two 
wings  superiorly,  fonns  a  slight  arch  curved  inwards.  When  the  finger  is 
introduced  into  this  commissure  it  does  not  enter  the  nasal  cavity,  but  the  false 
nostril — a  conical  pouch  formed  by  the  skin,  extending 
to  the  angle  comprised  between  the  nasal  spine  and  the 
ascending  process  of  the  premaxillary  bone. 

In  the  Ass,  according  to  Goubaux,  the  false  nostrU  is 
areolated  at  the  posterior  extremity,  which  ascends  beyond 
the  summit  of  the  re-entering  angle  formed  by  the  nasal 
and  premaxillary  prolongation. 

The  inferior  commissure  is  round  and  wide,  and,  to- 
wards the  bottom,  presents  an  opening,  sometimes  double^ 
which  looks  as  if  punched  out ;  this  is  the  inferior  orifice 
of  the  lachrymal  duct,  which,  in  the  Ass  and  Mule,  is 
carried  to  the  inner  face  of  the  external  wing,  near  the 
superior  commissure. 

Steucture. — The  nostril  is  composed  of  a  carti" 
laginous frameivorlc,  muscles  to  move  it,  and  shin,  vessels^ 
and  nerves. 

Cartilaginous  frameworlc  (Fig.  306). — This  framework 
is  formed  by  a  cartilage,  bent  like  a  comma,  and  which,  in 
its  middle  part,  lies  against  that  of  the  opposite  side,  the 
two  making  a  kind  of  figure  X.  Fixed  in  a  movable 
manner  to  the  inferior  extremity  of  the  middle  septum 
of  the  nose,  by  means  of  short  intei-posed  fibres,  this  cartilage  offers  :  a  wide  upper 
part,  situated  in  the  substance  of  the  inner  wing  of  the  nostril,  and  covered  by 
the  dilatator  naris  transversalis  of  the  nose  (Fig.  306,  1)  ;  and  an  inferior  portion, 
which,  after  passing  into  the  lower  commissure,  is  prolonged,  in  a  blunt  point,  to 
the  external  wing,  where  it  receives  the  insertion  of  several  fasciculi  belonging  to 
the  orbicularis  muscle  of  the  lips,  the  dilatator  naris  lateralis,  and  the  levator 
labii  superioris  (Fig.  306,  2).     Each  wing,  therefore,  possesses  its  cartilaginous 


CARTILAGES   OF   THE 

NOSTRILS 

1,  1,  Wide  portion,  forming 
the  base  of  the  internal 
wing  of  the  nostril ;  2, 
2,  narrow  extremity  pro- 
longed into  the  external 
wing;  3,  superior  or  an- 
terior border  of  the  nasal 
septum. 


THE  NASAL    CAVITIES.  519 

skeleton  ;  but  that  of  the  external  wing  is  very  incomplete,  in  consequence  of  its 
being  only  formed  by  the  inferior  extremity  of  the  common  cartilage. 

These  cartilages,  it  will  be  understood,  sustain  the  alte  of  the  nose,  prevent 
their  falling  inwards,  and  always  keep  open  the  external  orifices  of  the  respiratoiy 
apparatus. 

Muscles. — The  motor  muscles  of  the  alae  are  all  dilators  in  the  domesticated 
animals.  They  are  :  the  trcmversalis  dilatator  naris,  a  single  muscle  placed  on  the 
widened  portions  of  the  cartilages  ;  the  dilatator  naris  lateralis,  the  insertion  of 
which  occupies  the  whole  extent  of  the  external  wing  ;  the  dilatator  naris  superior, 
fixed,  by  its  two  portions,  to  the  skin  of  the  false  nostril ;  the  dilatator  naris 
inferior,  which  is  confounded,  superiorly,  with  the  external  fasciculus  of  the  pre- 
ceding muscle,  it  being  attached  to  the  inferior  branch  of  the  cartilaginous 
appendix  of  the  supermaxillary  turbinated  bone  ;  and,  lastly,  the  levator  labii  supe- 
rioris  alaque  nasi,  the  anterior  branch  of  which  is  inserted,  in  part,  into  the  external 
wing.  All  these  muscles,  having  been  described  in  the  Myology  (p.  278),  need 
not  be  further  alluded  to  here. 

Skin  of  the  nose. — The  skin  covering  the  alae  of  the  nose,  externally,  is 
doubled  over  their  free  margin  to  line  their  internal  surface,  being  prolonged 
over  the  entire  extent  of  the  false  nostril,  and  is  continued  in  the  nasal  fossae, 
by  the  properly  so  called  pituitary  membrane.  This  skin  is  fine,  thin,  charged  with 
colouring  pigment,  often  marked  by  leprous  spots,  and  adheres  closely  to  the 
muscles  included  between  its  duphcatures,  through  the  medium  of  a  very  dense, 
resisting,  connective  tissue. 

Vessels  and  nerves. — The  nostrils  are  supplied  with  blood  by  the  superior 
coronary,  the  external  nascd,  and  the  palato-labial  arteries ;  it  is  returned  by  the 
glosso-facial  veins,  and  partly  by  the  venous  network  of  the  nasal  mucous 
membrane.  The  lymphatics,  large  and  abundant,  receive  those  of  the  pituitary 
membrane,  and  join  the  submaxillary  glands  by  passing  over  the  cheeks.  The 
nerves  are  very  numerous,  the  sensory  being  derived  from  the  maxillary  branch 
of  the  fifth  pair,  and  the  motors  from  the  facial  nerve. 

Functions. — The  nostrils  permit  the  entrance  to  the  nasal  cavities,  of  the 
air  which  is  to  pass  to  the  lungs.  Their  dilatability  allows  the  admission  of  a 
greater  or  less  volume,  according  to  the  demands  of  respiration.  It  is  to  be 
remarked  that,  in  Solipeds,  the  nostrils  are  the  only  channel  by  which  the  air  can 
gain  access  to  the  trachea,  in  consequence  of  the  great  development  of  the  soft 
palate,  which  is  opposed  to  its  entrance  by  the  mouth  ;  these  orifices  are  therefore, 
for  this  reason,  relatively  larger  than  in  the  other  domesticated  animals,  in  which 
the  passage  of  air  by  the  buccal  cavity  is  easily  accomplished. 

2.  The  Nasal  Foss^  (Figs.  306,  307,  308). 

Channeled  in  the  substance  of  the  head,  above  and  in  front  of  the  palate,  and 
separated  from  one  another,  in  the  median  plane,  by  a  cartilaginous  septum  which 
does  not  exist  in  the  skeleton,  the  nasal  fossas  extend  from  the  nostrils  to  the 
cribriform  plate  of  the  ethmoid  bone,  in  a  direction  parallel  to  the  larger  axis  of 
the  head.  Their  length  is,  therefore,  exactly  measured  by  that  of  the  face  (see 
Fig.  308  for  the  whole  of  these  cavities). 

The  nasal  fossae  are  formed  by  two  lateral  walls,  a  roof  or  arch,  di.  floor,  and 
two  extremities. 

Walls. — The  two  walls  are  very  close  to  each  other,  and  the  more  so  as  they 
are  examined  towards  the  ethmoid  bone  and  the  roof  of  the  cavity.     The  space 


520  RESPIRATORY  APPARATUS  IN  MAMMALIA. 

separating  them  varies,  in  proportion  as  it  is  measured  at  the  turbinated  bones  or 
at  the  meatuses. 

Inner  wall. — This  is  fonned  by  the  nasal  septum,  and  is  perfectly  smooth. 

Outer  vmlL — This  is  chiefly  constituted  by  the  supermaxillary  bone ;  it  is 
very  rugged,  and  is  divided  into  three  meatuses,  or  passages,  by  the  tui'binated 
bones — the  iiTegular  columns  applied  against  the  inner  face  of  the  before-mentioned 
bone. 

The  turbinated  hones  have  already  been  described  (p.  73),  and  we  will  only 
now  refer  to  the  principal  features  in  their  arrangement.  Each  is  a  bony  plate 
rolled  upon  itself  (Fig.  307,  2,  3),  and  divided,  internally,  into  two  sections,  the 
superior  of  which  forms  part  of  the  sinus,  and  the  inferior  belongs  to  the  nasal  fossa ; 
they  are  continued,  inferiorly,  by  a  fibro-cartilaginous  framework,  which  prolongs 

Fig.  307. 


TRANSVERSE   SECTION  OF  THE   HEAD  OF   AN   OLD   HORSE,  SHOWING  THE  ARRANGEMENT  OF  THE 
NASAL  CAVITIES   AND  MOUTH. 

I,  1,  Nasal  fossae ;  2,  superior  turbinated  bone  ,  3,  inferior  ditto ;  4,  median  septum  of  the  nose ;  5, 
central  part  of  the  buccal  cavity  (drawn  more  spacious  than  it  really  is  when  the  two  jaws  are 
brought  together) ;  6,  6,  lateral  portions  of  the  same ;  7,  section  of  the  tongue,  showing  it  filling 
the  lingual  canal. 


their  nasal  section  to  the  external  orifice  of  the  nose.  The  flexible  appendage  of 
the  ethmoidal  turbinated  bone  is  usually  single,  sometimes  double,  and  disappears 
before  reaching  the  alfe  of  the  nose.  That  of  the  premaxillary  turbinated  bone  is 
always  bifurcated,  and  its  antero-superior  branch  is  directly  continued  by  the 
superior  extremity  of  the  internal  wing  of  the  nostril. 

The  meatuses  are  distinguished  into  superior,  middle,  and  inferior,  or  into 
anterior,  middle,  and  posterior,  as  the  head  is  inspected  in  a  vertical  or  horizontal 
position.  The  superior  passes  along  the  corresponding  border  of  the  ethmoidal 
turbinated  bone,  and  is  confounded  with  the  roof  of  the  nasal  cavity  ;  it  is  pro- 
longed, behind,  to  near  the    cribriform  plate  of  the  ethmoid  bone,  and  is  the 


THE  NASAL   CAVITIES.  521 

narrowest.  The  middle,  comprised  between  the  two  tui'binated  bones,  presents, 
on  arriving  near  the  ethmoidal  cells,  the  orifice  that  brings  all  the  sinuses  into 
commmiication  with  the  nasal  fossa.  This  orifice  is  ordinarily  narrow  and 
curved ;  but  we  have  seen  it  sometimes  converted  into  a  foramen  sufiiciently 
wide  to  permit  the  introduction  of  a  finger-end.  It  is  also  by  this  meatus  that 
the  inferior  compartment  of  the  turbmated  bones  opens  into  the  nasal  fossa,  these 
two  bones  being  each  rolled  in  a  contrary  direction.  The  inferior  meatus,  situated 
under  the  maxillary  turbinated  bone,  is  not  distinct  from  the  floor  of  the  nasal 
cavity  (see  Fig.  307  for  the  arrangement  of  the  turbinated  bones  and  the 
meatuses  on  the  external  wall  of  the  nose). 

Roof  or  arch. — This  is  formed  by  the  nasal  bone,  and  is  only  a  nan'ow  channel, 
confounded,  as  has  been  said,  with  the  superior  meatus. 

Floor.— Wider,  but  not  so  long  as  the  roof,  which  is  opposite  to  it,  and  from 
which  it  is  distant  by  the  height  of  the  cartilaginous  septum,  the  floor  is  concave 


Fig.  308. 


LONGITUDINAL   MEDIAN   SECTION   OF   THE   HEAD   AND   UPPER   PART   OF   THE   NECK. 

1,  1,  Atlas;  2,  2,  dentata ;  3,  trachea;  4,  right  stylo-thyroideus ;  5,  guttural  pouch ;  6,  stylo.. 
pharyngeus;  8,  palato-pharyngeus ;  9,  sphenoidal  sinus;  10,  cranial  cavity;  11,  occiput;  12, 
parietal  protuberance;  13,  frontal  sinus;  14,  ethmoidal  turbinated  bone;  15,  premaxillary  turbi- 
nated bone;  16,  entrance  to  nostril;  18,  pharyngeal  cavity;  19,  inferior  maxilla;  20,  premaxilla; 
21,  hard  palate. 

from  one  wall  to  the  other,  and  rests  on  the  palatine  arch,  which  separates  .the 
mouth  from  the  nasal  cavities. 

In  front  of  this  nasal  region  is  remarked  the  canal  or  or  gem.  of  Jacohson — a 
short  duct  terminating  in  a  cul-de-sac  in  the  middle  of  the  cartilaginous  substance 
which  closes  the  incisive  foramen.  •  At  the  bottom  of  this  ctd-de-sac  opens  a 
second  canal,  longer,  wider,  and  more  remarkable,  but  which  has  not  yet  been 
described.  (It  has  been  described  by  Steno,  and  is  named  "  Steno's  canal")  It 
has  sometimes  the  diameter  of  a  writing-quill,  commences  by  a  cul-de-sac  at  the 
level  of  the  second  molar  tooth,  and  accompanies  the  inferior  border  of  the  vomer 
from  behind  to  before,  where  it  is  enveloped  in  a  kind  of  cartilaginous  sheath — 
a  dependency  of  the  nasal  septum  ;  it  terminates,  as  we  have  said,  after  a  course 
of  about  5  inches. 

The  structure  of  Jacobson's  organ  resembles  that  of  the  excretory  duct  of 
glands  ;  its  walls  are  evidently  composed  of  two  tunics — an  internal  or  mucous,  very 


522  RESPIRATORY  APPARATUS  IN  MAMMALIA. 

rich  in  follicles,  and  having  longitudinal  folds  ;  and  an  external,  of  a  fibrous  nature. 
These  membranes  receive  numerous  vessels,  as  well  as  nerves  emanating  from  a 
long  filament  of  the  spheno-palatine  ganglion,  and  which  may  be  traced  from 
the  external  side  of  the  canal  to  near  the  incisive  foramen,  where  it  is  lost.  Such 
is  the  organ  of  Jacobson  ;  its  uses  are  quite  unknown.  (It  belongs  to  the 
olfactory  region,  for  between  the  ciliated  cells  of  its  mucous  membrane  are  found 
staff-like  cells,  which  are  connected  with  the  ends  of  the  olfactory  nerve-filaments.) 

Extremities. — The  anterior  or  inferior  extremity  of  the  nasal  fossa  {regie  vesti- 
bularis) is  formed  by  the  nostril  already  described.  The  posterior  or  superior 
extremity  presents,  above,  a  space  occupied  by  the  ethmoidal  cells.  Below  £md 
behind,  this  extremity  communicates  with  the  pharyngeal  cavity  by  a  wide  oval 
opening,  which  is  circumscribed  by  the  vomer  and  palate  bones  :  this  is  the 
guttural  opening  of  the  nasal  fossa  (or  posterior  nares). 

Structure. — The  nasal  fossae  offer  for  study  :  1.  The  bony  frameivork 
by  which  these  cavities  are  formed.  2.  The  cartilaginous  septum,  separating 
them.     ;3.  The  pitidtary  membrane — the  mucous  layer  lining  their  walls. 

1.  Bony  Framework  of  the  Nasal  Fossae. — This  comprises  :  1.  The 
nasal.,  maxillary,  frontal,  and  palate  bones,  which  together  form  a  vast  irregular 
wall  circumscribing  the  nasal  fossas.  2.  The  ethmoid  bone,  occupying  the  bottom 
of  this  tubular  cavity,  and  the  turbinated  bones  applied  against  the  lateral  walls. 
3.  The  vomer,  placed  in  the  median  plane,  and  serving  as  a  support  for  the 
cartilaginous  partition  dividing  this  single  cavity  into  two  compartments.  All 
these  bones  having  been  already  studied  in  detail,  we  confine  ourselves  to  their 
simple  enumeration. 

2.  Middle  Septum  of  the  Nose  {septum  nasi)  (Fig.  307,  4). — Formed  of 
cartilage  susceptible  of  ossification,  this  partition  is  nothing  more  than  the  per- 
pendicular lamina  of  the  ethmoid  bone  prolonged  to  the  extremity  of  the  nose. 
Its  elongated  form  permits  us  to  recognize  in  it  tivo  faces,  two  borders,  and  two 
extremities.  The  faces  are  channeled  by  a  multitude  of  furrows,  which  lodge 
the  anastomosing  vessels  of  the  magnificent  venous  plexus  of  the  pituitary 
membrane. 

The  superior  border,  united  to  the  frontal  bone  and  median  suture  of  the 
nasal  bones,  expands  to  the  right  and  left  on  the  inner  faces  of  these,  in  forming 
two  lamina,  thm  at  their  free  margin,  the  section  of  which  is  represented  in 
Fig.  307.  These  laminae  are  wide  enough  in  front  to  project  beyond  the  nasal 
spine.     The  inferior  border  is  received  into  the  mortice  of  the  vomer. 

The  posterior  extremity  is  continued  without  any  precise  limitation,  by  the 
perpendicular  lamina  of  the  ethmoid  bone. 

The  anterior  extremity,  a  little  wider,  supports  the  cartilages  of  the  nostrils. 
It  is  joined,  below,  to  the  premaxillary  bones,  and  is  spread  out  on  the  incisive 
openings  in  a  thick  layer  which  exactly  closes  them. 

This  septum  is  covered  by  a  thick  perichondrium,  which  adheres  intimately 
to  the  pituitary  membrane. 

3.  Pituitary  Membrane. — This  membrane — also  designated  the  olfactory 
mucous  membrane,  and  Schneiderian  membrane — is  continuous  with  the  skin  lining 
the  inner  face  of  the  alas  of  the  nose.  Examined  on  the  internal  wall  of  the 
nasal  fossae,  the  pituitary  membrane  is  seen  to  cover  the  cartilaginous  septum 
forming  this  wall,  then  spreads  over  the  floor  as  well  as  the  roof  of  the  cavity, 
reaching  the  outer  wall,  which  it  also  covers  in  enveloping  the  external  surface 
of  the  turbinated  bones,  and  is  insinuated,  by  the  middle  meatus,  into  the  cells 


THE  NASAL   CAVITIES. 


523 


Fig.  309. 


11/ 


of  the  inferior  or  anterior  compartment  of  these  osteo-cartilaginous  columns.  It 
also  penetrates,  by  the  semicircular  opening  of  this  meatus,  into  the  sinus,  to  give 
it  its  mucous  lining,  and  is  likewise  prolonged  into  the  canal  of  Jacobson. 
Behind,  it  is  continuous  with  the  lining  membrane  of  the  pharyngeal  cavity. 

Its  deep  face  is  separated  by  the  periosteum  or  perichondrium,  from  the  bony 
or  cartilaginous  walls  on  which  it  is  spread  ;  and  it  is  united  to  the  two  precited 
layers,  this  union  being  closest  where  it  is  thinnest,  although  it  can  always  be 
easily  distinguished  from  them  throughout  the  whole  extent  of  the  nasal  fossa. 
The  free,  or  superficial  face,  presents  numerous  glandular  orifices,  and  is  constantly 
covered  by  an  abundance  of  mucus,  that  prevents  the  desiccation  to  which  this 
surface  is  exposed  by  the  incessant  movement  of  air  over  it. 

Steuctuee. — The  organization  of  the  pituitary  membrane  resembles  that  of 
other  mucous  membranes,  but  it  also  presents  some  difi'erences  according  as 
it  is  examined  near  the  nostrils  or  deeper  in  the  cavities.  It  is  also  usual 
to  divide  it  into  two  portions — the  olfactory  mucous 
memhrane,  which  covers  the  upper  part  of  the  ethmoidal 
turbinated  bone  and  cells  ;  and  the  Schneiderian  mem- 
brane, fining  the  inferior  two-thirds  of  the  nasal  cavities. 

The  corium  {tunica  propria)  of  the  Sclmeiderian  mem- 
hrane  {regio  respiratoria)  is  thick,  soft,  spongy,  and  rose- 
coloured,  and  contains  a  large  number  of  vessels  and 
glands.  The  latter  are  mucus  or  racemose  glands,  and 
are  extremely  abundant  in  the  layer  covering  the  septum 
of  the  nose,  as  well  as  at  the  inner  face  of  the  carti- 
laginous appendages  of  the  turbinated  bones  ;  though 
they  are  rare  or  altogether  absent  on  the  external  face 
of  the  latter.  The  epithelium  is  ciliated  and  stratified, 
the  deeper  cells  being  spherical,  those  on  the  surface 
cyhndrical. 

The  olfactory  mucous  memhrane  {regio  olfactoria) 
differs  from  the  preceding  by  its  greater  thinness,  its 
delicateness,  its  slightly  yellow  tint,  and  the  character 
of  its  epithelium.  The  corium  {tunica  propria)  contains 
straight  or  slightly  convoluted  tubular  glands — the  glands 
of  Bowman.  The  epithelium  is  columnar  and  stratified, 
and  readily  alters  ;  in  animals  it  is  destitute  of  cifia. 
The  deeper  cells  contain  some  yellowish  pigment  granules. 
Schultze  describes  as  olfactory  cells,  certain  fusiform 
elements  which  he  considers  are  concerned  in  olfaction, 
prolongations — a  deep  one,  which  is  connected  with  the  fibres  of  the  olfactory 
nerve  ;  and  a  superficial,  that  enters  between  the  epithelial  cells,  and  tends  to 
approach  the  free  surface  of  the  membrane. 

(The  "  olfactory  cells  "  are  thin,  rod-like  bodies  (Fig.  309,  b),  presenting 
varicose  enlargements  which  are  connected  with  processes  of  deeper-seated  nerve- 
cells.  The  epithelial  cylinders  proper  {d,  e)  are  related  at  their  bases  with  the 
septa  of  connective  tissue  belonging  to  the  sub-epithelial  glandular  layer,  and  are 
probably  in  communication  with  the  olfactory  cell.  Schultze  describes  another 
set  of  epithelial  cells  {a)  as  terminating  externally  by  truncated  flat  surfaces,  and 
to  all  appearance  not  covered  by  any  membrane,  apart  from  the  contents  of  the 
cell,  which  are  yellow,  granular  protoplasm,  surrounding  an  oval  nucleus  lying 


CELLS   OF   THE   OLFACTORT 

MUCOUS    MEMBRANE. 

a,  b,  c,  After  Schultze; 
d,  e,  f,  after  Lockhart 
Clarke. 

These  cells  have  two 


524 


RESPIBATORY  APPARATUS  IN  MAMMALIA. 


Fig.  310. 


in  colourless  protoplasm.  The  extremity  of  these  cells  is  thin,  and  they  can  be 
traced  inwards  until  they  expand  into  a  flat  portion  that  sends  off  processes, 
which  appear  to  be  continuous  with  the  fibres  of  the  submucous  connective  tissue. 
Similar  cells  (c)  are  found  towards  the  margin  of  the  true  olfactory  region,  but 
these  have  a  band  at  their  free  extremity,  which  is  also  provided  with  a  circle 
of  cilia.) 

The  pituitary  membrane  receives  its  blood  by  the  ophthalmic  and  nasal 
arteries  ;  it  is  returned  by  the  large  anastomosing  veins  which  form — in  the  deep 
layer — a  long,  close,  and  magnificent  plexus  that  terminates  in  the  satellite  vein  of 
the  nasal  artery.  This  plexuous  arrangement  is  so  marked  at  certain  points — as 
at  the  appendages  of  the  turbinated  bones — that  it  gives  the  mucous  membrane 
somewhat  the  appearance  of  erectile  tissue.  It  will  be  understood  that  in 
favouring  the  stagnation  of  the  blood,  this  arrangement  predisposes  to  hemor- 
rhage. 

The  lymphatics  of  the  pituitary  membrane  could  not  be  injected  for  a  long 
time,  neither  in  Man  nor  animals  ;  and  this  led  several  anatomists  to  deny  their 
existence.  Nevertheless,  they  do  exist,  and  form  a  fine  super- 
ficial network  on  the  septum  of  the  nose,  the  turbinated 
bones,  and  the  meatuses.  The  trunks  passing  from  this  net- 
work go  to  the  submaxillary  glands. 

The  nerves  of  this  membrane  are  numerous,  and  are 
derived  from  the  first  and  fifth  pairs,  and  from  Meckel's 
ganglion.  The  ramifications  of  the  olfactory  nerve,  on 
emerging  from  the  apertures  of  the  cribriform  plate  of  the 
ethmoid  bone,  pass  to  the  inner  and  outer  walls  of  the  nasal 
cavities  ;  being  destined  for  the  olfactory  mucous  membrane, 
they  do  not  descend  below  the  upper  third  of  these  cavities. 
They  form  at  first  a  close  plexus,  and  afterwards  terminate 
in  a  manner  not  quite  understood.  Schultze  admits  that 
they  terminate  on  the  olfactory  cells  mentioned  above. 

The  branches  derived  from  Meckel's  ganglion  and  the 
fifth  pair,  are  specially  destined  for  the  Schneiderian  mem- 
brane, and  are  named  the  ethmoidal  branches  of  the  palpebro- 
nasal  and   spheno-palatine  nerves.      They  endow   the  nose 
with  an  acute  degree  of  sensibility,  and  it  is  believed  that  they  render  olfaction 
more  perfect. 

(It  is  to  be  remarked  that  the  filaments  composing  the  olfactory  plexus,  differ 
from  ordinary  cranial  nerves  in  containing  no  white  substance  of  Schwann,  and 
are  nucleated  and  finely  granular  in  texture,  resembling  the  gelatinous  form  of 
nerve-fibres.  The  surface  to  which  they  are  limited  is  that  covered  with  the 
yellowish-brown  epithelium.) 


FIBRES  OF  ULTIMATE 
RAMIFICATIONS  OF 
OLFACTORY  NERVE 
OF   DOG. 


3.  The  Sinuses. 

The  sinuses  are  very  winding  cavities,  excavated  in  the  substance  of  the  bones 
of  the  head,  on  the  limits  of  the  cranium  and  face,  and  around  the  ethmoidal 
masses,  which  they  envelop. 

These  cavities — diverticuli  of  the  nasal  fossae — are  pairs,  and  are  five  on 
each  side,  arranged  in  two  groups:  1.  The /rowto/,  supermaxiUarij,  sphenoidal, 
ethmoidal  sinuses.  2.  The  inferior  maxillary  sinus.  The  first  four  communicate  ; 
the  last  is  usually  perfectly  isolated. 


TEE  NASAL   CAVITIES.  525 

First  Group. 

Frontal  Sinus. — This  cavity,  situated  at  the  inner  side  of  the  orbit,  presents 
very  irregular  walls,  which  are  formed  by  the  frontal  nasal,  lachrymal,  and 
ethmoid  bones,  and  the  superior  portion  of  the  ethmoidal  turbinated  bone.  lb 
communicates  with  the  superior  maxillary  sinus  by  a  vast  opening,  made  in  a 
very  thin  bony  partition.  A  thick  vertical  plate,  often  bent  to  the  right  or  left, 
but  always  imperforate,  separates  this  sinus  from  that  of  the  opposite  side. 

Superior  Maxillary  Sinus. — Channeled  beneath  the  orbit,  between  the 
maxillary,  malar,  ethmoid,  and  lachrymal  bones,  this  diverticulum  is  the 
largest  of  all,  and  is  divided  into  two  great  compartments  by  the  maxillo-dental 
canal,  which  traverses  it.  The  internal  compartment  is  a  kind  of  shallow  cavity, 
continuous  with  the  sphenoidal  sinus,  and  presents  a  narrow  sht,  which  opens 
into  the  ethmoidal  sinus.  The  external  compartment  is  separated,  in  front, 
from  the  maxillary  sinus,  by  a  partition  which  Goubaux  has,  contrary  to  the 
generally  received  opinion,  demonstrated  to  be  imperforate  at  all  periods  of  life  ; 
though  he  has  sometimes  found  it  so  thin  as  only  to  consist  of  two  layers  of 
mucous  membrane  laid  against  each  other.  This  compartment  is  prolonged 
backwards  into  the  maxillary  protuberance,  and  the  roots  of  the  two  last  molars 
project  into  its  interior. 

Sphenoidal  Sinus. — This  is  the  smallest,  after  that  of  the  great  ethmoidal 
cell.  Formed  by  the  sphenoid  and  palatine  bones,  this  cavity  is  very  irregular, 
and  is  subdivided  by  incomplete  septa  into  several  compartments,  which  may  be 
always  reduced  to  two — an  anterior,  comprised  between  the  palatine  laminae  ;  and 
a  posterior,  in  the  body  of  the  sphenoid  bone.  In  contact,  on  the  median  line, 
with  the  sinus  of  the  opposite  side,  it  is  separated  from  it  by  a  twisted  plate, 
which  is  constantly  perforated,  even  in  young  animals. 

Ethmoidal  Sinus. — This  is  a  cavity  in  the  large  ethmoidal  cell ;  it  consti- 
tutes a  real  sinus,  and  has  a  narrow  slit  which  brings  it  into  communication  with 
the  superior  maxillary  sinus. 

Second  Group. 

Inferior  Maxillary  Sinus. — This  last  diverticulum  is  remarkable,  because 
of  its  not  communicating  with  the  others.  Excavated  in  the  super  maxillary 
bone,  and  separated  from  the  superior  sinus  by  the  imperforate  septum  previously 
mentioned,  it  is  divided,  like  the  latter  cavity,  into  two  compartments — an 
internal,  prolonged  into  the  superior  cavity  of  the  supermaxillary  turbinated 
bones  ;  and  an  external — the  smallest — showing  the  roots  of  the  fourth  molar, 
rarely  those  of  the  third.  It  does  not  descend,  as  Rigot  has  asserted,  above  the 
three  anterior  molars  ;  supposing  the  head  to  be  vertical,  it  does  not  extend,  in 
the  adult  Horse,  beyond  the  extremity  of  the  maxillary  ridge,  in  front  of  which  it 
would  be  necessary  to  trephine,  in  order  to  reach  it.  It  is  sometimes  larger  on 
one  side  than  the  other. 

The  inferior  maxillaiy  sinus,  in  the  Ass,  communicates  with  the  superior 
maxillary  sinus.  "  These  two  parts  of  the  maxillary  sinus,  or  the  two  maxillary 
sinuses,"  says  Goubaux,  "  always  communicate  largely  with  each  other  in  the 
Ass.  I  have  never  seen  an  exception  to  this  ;  and  the  peculiarity  is  due  to  the 
fact,  that  the  base  or  posterior  extremity  of  the  inferior  turbinated  bone  is  checked 
in  its  development,  and  does  not  curve  sufficiently  to  join  the  inner  surface  of 
the  supermaxilla,  and  become  attached  thereto," 
36 


526  RESPIRATORY  APPARATUS  IN  MAMMALIA. 

Communicating  Orifice  of  the  Sinuses  with  the  Nasal  Fossa. — All 
the  sinuses  of  one  side  communicate  with  the  corresponding  nasal  fossa,  by  the 
curved  slit  at  the  bottom  of  the  middle  meatus.  This  slit  penetrates  the  superior 
maxillary  sinus,  under  the  septum  that  separates  it  from  the  frontal  sinus  ;  it 
also  enters  the  inferior  maxillary  sinus,  which  thus  communicates  solely  with  the 
nasal  cavity,  while  the  other  diverticuli  open  in  common  into  this  cavity,  through 
the  medium  of  the  superior  maxillary  sinus. 

Mucous  Membrane  of  the  Sinuses. — In  entering  the  sinuses  to  cover 
their  walls,  the  pituitary  membrane  becomes  extremely  thin,  and  loses  its  great 
vascularity  ;  it  is  applied  immediately  to  the  bones,  and  serves  as  a  periosteum. 
It  has  some  nerves  which  terminate  in  small  bell-shaped  organs  (Inzani). 

Development  of  the  Sinuses. — These  cavities  begin  to  be  developed  in 
the  foetus,  and  are  gradually  formed  in  the  thickness  of  the  bones  they  occupy. 
They  increase  during  the  animal's  hfetime,  by  the  thinning  of  the  bony  plates 
enclosing  or  partitioning  them,  and  particularly  by  the  growth  of  the  superior 
molar  teeth,  the  roots  of  which  project  into  them.  The  formation  of  the  inferior 
maxillary  sinus  is  more  tardy  than  the  others  ;  though  it  is  not  so  late  as  seven 
or  eight  years,  as  the  majority  of  Veterinary  Anatomists  have  asserted.  Goubaux 
has  proved  that  the  sinus  is  already  present  in  a  six-months-old  animal ;  and  in  a 
head  which  has  been  for  several  years  in  the  museum  of  the  Lyons  School,  and 
which  belonged  to  a  foal  of  very  small  stature,  about  a  year  old,  this  sinus  is 
found,  in  its  external  part,  to  be  already  1^  inches  in  depth,  and  -^  of  an  inch 
in  width. 

Functions  of  the  Sinuses. — Have  the  sinuses  or  diverticuli  of  the  nasal 
cavities,  the  same  uses  as  these  cavities  ?  It  is  probable,  although  not  absolutely 
certain.  There  is  nothing  to  prove  that  they  have  anything  to  do  with  respira- 
tion or  olfaction ;  and  it  would  seem  that  their  exclusive  function  is  to  give 
increased  volume  to  the  head  without  increasing  its  weight,  and  in  this  way  to 
furnish  wide  surfaces  of  attachment  for  the  muscles  belonging  to  this  region — 
these  cavities  being  all  the  more  ample  as  the  muscles  are  large  and  numerous. 

DiFFEBENTIAL   ChABACTERS   IN   THE   NaSAL    CaVITIES   OF   THE   OTHER   ANIMALS. 

1.  Nostrils. — In  the  Ox,  the  nostrils,  placed  on  each  side  of  the  muffle,  are  narrower  and 
less  movable  than  in  the  Horse.  (The  superior  extremity  of  the  ala  is  not  horizontal ;  the 
inferior  is  divided  into  two  branches.) 

In  the  Pig,  the  end  of  the  nose  constitutes  the  snout  (rostrum  suis),  the  anterior  surface  of 
which,  plane  and  orbicular,  shows  the  external  orifices  of  the  nostrils.  This  snout —  a  veritable 
tactile  organ  employed  by  the  animal  to  dig  up  the  ground — is  covered  by  a  dark-coloured 
skin,  kept  damp  by  a  humid  secretion,  like  the  muffle  of  the  Ox.  It  has  for  base  tlie  scooping- 
hone—a,  particular  piece  situated  at  the  extremity  of  the  nasal  septum,  and  enveloped  by  a 
layer  of  cartilage  that  extends  around  the  nostrils.  It  is  easy  to  distinguish  two  symmetrical 
halves  in  this  bone,  which  evidently  represent  the  two  cartilages  in  the  nose  of  Solipeds. 

In  the  Dog,  the  end  of  the  nose  forms  a  salient  region,  which  is  roughened,  naked,  usually 
dark-coloured,  damp,  and  sometimes  divided  by  a  median  groove ;  in  this  region  the  nostrils 
are  placed,  their  form  resembling  two  commas  opposed  to  each  other  by  their  convexities. 
The  cartilaginous  framework  sustaining  these  orifices  is  not  composed  of  separate  pieces,  but 
is  only  a  dependency  of  the  median  septum  and  the  appendages  of  the  turbinated  bones. 

The  same  considerations  apply  to  the  nostrils  of  the  Cat,  with  the  exception  of  tlie  colour 
of  the  integument,  which  is  nearly  always  of  a  rosy  hue,  like  the  mucous  surfaces. 

2.  Nasal  Cavities.— The  nasal  fossae  of  the  Ox,  Sheep,  and  Goat,  are  distinguished  by 
the  presence  of  a  third  turbinated  bone— the  olfactory  antrum,  and  by  the  communication 
existing  between  them,  posteriorly,  above  the  inferior  border  of  the  vomer.  We  have  already 
seen  that  in  these  animals,  as  in  those  yet  to  be  mentioned,  the  canal  of  Jacobson  passes 
completely  through  the  palatine  arch. 


THE  LARYNX.  527 

In  the  Pig,  the  nasal  fossae  are  long  and  narrow.  They  are,  on  the  contrary,  very  short 
in  the  Dog  and  Cat,  and  the  internal  cells  of  the  turbinated  bones,  remarkable  for  their 
number  and  complexity,  all  communicate  with  the  proper  nasal  fossae,  without  concurring  iu 
the  formation  of  the  sinuses-  The  latter  are  divided  by  the  vomer  into  two  superposed  com- 
partments, very  distinct  from  each  other  iu  their  posterior  half;  the  superior  is  olfactory,  the 
inferior  is  respiratory. 

3.  Sinuses.— In  the  Ox,  the  frontal  amuses  are  prolonged  into  the  bony  cores  which  support 
the  horns,  and  into  the  parietal  and  occipital  bones ;  they  therefore  envelop,  in  a  most  com- 
plete manner,  the  anterior  and  superior  part  of  the  cranium,  and  form  a  double  wall  to  this 
bony  cavity.  They  are  extremely  iiverticulated,  and  do  not  communicate  with  those  of  the 
supermaxillary  bones.  They  usually  open,  on  each  side,  into  the  nasal  cavities,  by  four 
apertures  at  the  base  of  the  great  ethmoidal  cell.  According  to  Girard,  three  of  these  orifices 
lead  to  special  compartments,  isolated  from  one  another,  and  grouped  around  the  orbit,  in 
consequence  of  which  these  diverticuli  of  tlie  frontal  sinuses  are  designated  the  orbital  sinuses. 

This  author  lias  denied  the  presence  of  sphenoidal  sinuses;  but  they  exist,  although  small, 
and  are  in  communication  with  the  preceding. 

The  sinus  of  the  great  ethmoidal  cell  comports  itself  as  in  the  Horse. 

There  is  only  one  pair  of  maxillary  sinuses,  which  are  very  large,  and  partitioned  into  two 
compartments  by  a  plate  of  bone ;  this  bears  at  its  superior  border  the  supermaxillo-dental 
canal,  like  the  superior  maxillary  sinus  of  Solipeds.  The  external  or  maxillary  compartment, 
is  prolonged  into  the  lachrymal  protuberance;  the  internal  occupies  the  substance  of  the 
palatine  arch.  A  wide  orifice  at  the  base  of  the  maxillary  turbinated  bone  aflbrds  communica- 
tion between  this  sinus  and  the  nasal  fossa. 

In  the  Sheep  and  Goat,  there  exists  a  similar  arrangement  in  the  sinuses  of  the  head; 
but  these  cavities  are  much  less  spacious  than  in  the  Ox ;  the  frontal  sinus,  in  particular,  does 
not  extend  beyond  the  superior  border  of  the  frontal  bone. 

In  the  Pig,  these  latter  sinuses  are  prolonged  into  the  parietal  bones ;  though  they  are  far 
from  offering  the  same  extent  as  in  the  smaller  Ruminants.  It  is  the  same  with  the  others; 
they  present  an  arrangement  analogous  to  those  of  the  Sheep  and  Goat. 

In  the  Dog  and  Cat,  there  are  only,  on  each  side,  a  maxillary  and  a  frontal  sinus.  The 
first  scarcely  merits  notice*  and  the  second,  a  little  more  developed,  opens  into  the  nasal 
cavity  by  means  of  a  small  aperture  situated  near  the  middle  septum  of  the  two  frontal  sinuses. 

(Leyh  states  that  the  Carnivora  have  no  maxillary  sinus;  consequently,  the  sphenoidal 
sinus  communicates  below  with  the  nasal  fossae.) 

Comparison  of  the  Nasal  Cavities  in  Man  with  those  of  Animals. 

The  external  orifices  of  the  nasal  cavities  of  Man  are  called  nostrils;  these  are  flattened 
transversely,  and  prolonged  in  front  of  the  lobule  of  the  nose;  their  external  face,  or  ala, 
is  concave  and  movable.  They  are  lined  internally  by  a  membrane  that  holds  a  middle 
place  between  the  skin  and  mucous  membranes;  it  has  a  number  of  little  hairs,  eaUed 
vibrissas. 

The  cavities  or  nasal  fossas  offer  nothing  particular ;  as  in  animals,  they  show  a  superior, 
middle,  and  inferior  meatus.  On  their  floor,  in  front,  is  seen  the  superior  oriflce  of  the 
incisive  foramen,  which  corresponds  to  the  commencement  of  Jacobson's  canal.  The  pituitary 
membrane  has  a  squamous  epithelium  in  its  olfactory,  as  on  its  Schneiderian  portion.  At  the 
bottom  of  the  nasal  cavities  and  the  upper  part  of  the  pharynx,  is  a  kind  of  diverticulum 
named  the  posterior  nares;  it  has  been  already  alluded  to  when  speaking  of  the  pharynx. 

The  sinuses  are:  1.  The  sphenoidal  sinus  and  the  posterior  ethmoidal  cells,  that  open 
beneath  the  roof  of  the  nasal  fossae.  2.  The  middle  ethmoidal  cells,  opening  into  the  superior 
meatus.  3.  The  anterior  ethmoidal  cells,  and  frontal  and  maxillary  sinuses,  communicating 
with  the  middle  meatus.  All  these  sinuses  have  a  proper  communicating  orifice  with  the  nasal 
cavities. 

The  Air-tube  succeeding  the  Nasal  Cavities. 

This  single  tube  comprises  :  the  larynx,  which  commences  the  trachea ;  the 
latter  forms  the  body  or  middle  portion,  the  bronchi  terminating  it. 

1.  Laeynx  (Figs.  308,  311,  312,  313,  314). 
Preparation.— 1.  Make  a  longitudinal  section  of  the  head,  in  order  to  study  the  general 
arrangement  of  the  larynx  (Fig.  308).     2.  Isolate  the  cartilages,  to  examine  their  external 
conformation.     3.  Remove  the  muscles  from  a  third  larynx,  to  show  the  mode  of  articulation 


RESPIRATORY  APPARATUS  IN  MAMMALIA. 


Fig.  311. 


of  the  various  cartilages  (Figs.  312,  314).  4.  Prepare  the  muscles  in  conformity  with  the 
indications  furnished  by  a  glance  at  Fig.  314.  5.  Remove  a  larynx  as  carefully  as  possible, 
80  as  not  to  injure  the  walls  of  the  pharynx,  in  order  to  study  the  interior  of  the  organ,  and 
especially  its  pharyngeal  opening  (Fig.  315). 

Form — Situation. — The  larynx  forms  a  veiy  short  canal,  which  gives  admis' 

sion  to  the  air  during  respiration,  and  is  at  the  same  time  the  organ  of  the  voice. 

It  is  a  cartilaginous  box,  flattened  on  each  side,  and  open  from  one  end  to 

the  other :  the  anterior  orifice  being  situated  at  the  bottom  of  the  pharyngeal 

cavity,  and  the  posterior  continuous  with  the  trachea. 

This  apparatus,  situated  in  the  intra-maxillary  space,  is  suspended  between 

the  two  cornua  of  the  os  hyoides,  and 
fixed  to  the  extremities  of  these  append- 
ages by  one  of  its  constituent  pieces.  It 
supports  the  pharynx,  and  by  means  of 
the  walls  of  the  latter  is  attached  to  the 
circumference  of  the  posterior  openings 
of  the  nasal  cavities. 

In  order  to  facilitate  description,  this 
brief  notice  of  its  form,  situation,  general 
relations,  and  mode  of  attachment  will  be 
followed  by  a  notice  of  its  structure ; 
afterwards,  the  study  of  its  external  and 
internal  surfaces  will  receive  attention. 

Structuee  of  the  Larynx. — It 
comprises  in^its  structure  :  1.  A  cartila- 
ginous framework,  composed  of  five  pieces. 
2.  Muscles,  which  move  these  pieces.  3. 
A  mucous  membrane  spread  over  the  inner 
surface  of  the  organ.  4.  Vessels  and 
nerves. 

1.  Cartilaginous  fratneivorh  of  the 
larynx. — In  this  we  find  :  three  single 
median  cartilages — the  cricoid,  thyroid, 
and  epiglottis ;  and  two  lateral  cartilages, 
the  arytcenoid.  All  are  movable,  one  upon 
the  other. 

Cricoid  Cartilage  (Fig.  311,  c). 
— This  cartilage,  as  its  name  indicates 
(xptKos,  cTSos,  "  hke  a  ring "),  is  exactly 
like  a  ring  with  a  bezel  placed  upwards. 
Depressed  on  each  side,  but  all  the  less  as 
the  animal  has  its  respiratory  apparatus 
well  developed,  this  ring  offers  ttvo  faces,  and  ttvo  borders  or  circumferences.  The 
internal  face  is  smooth,  and  covered  by  mucous  membrane.  The  external  face  is 
provided,  in  the  middle  of  the  widened  portion  forming  the  bezel,  with  a  little 
eminence  more  or  less  prominent,  elongated  in  the  form  of  a  crest,  and  separating 
the  two  posterior  crico-arytaenoid  muscles  (to  which  it  gives  attachment)  from 
each  other.  On  the  sides  of  this  bezel  are  two  small,  articular,  concave  facets, 
which  coiTespond  to  the  branches  of  the  thyroid  cartilage.  Nothing  remarkable 
is  to  be  noted  for  the  remainder  of  the  extent  of  this  face.     The  superior  circum- 


CARTILAGES   OF   THE   LARYNX    DIS- 
ARTICULATED. 

C,  Anterior  surface  of  the  cricoid:  1,  facet 
for  the  arytaenoid ;  2,  facet  for  the  thyroid. 
A,  External  surface  of  the  arytcenoid.  a', 
ibid.,  internal  surface:  3,  facet  for  the 
cricoid.  T,  Thyroid,  seen  from  above:  4, 
4,  posterior  extremities  of  its  wings;  5, 
appendages  for  the  hyoid  cornua  ;  6,  body  of 
the  thyroid.  F,  Epiglottis,  supero-posterior 
surface:  7,  7,  prolongations  forming  the 
supposed  superior  vocal  cords. 


THE  LARYNX.  529 

fermce,  comprised  laterally  between  the  two  branches  of  the  thyroid  cartilage,  is 
concave  in  the  narrow  part  opposite  the  bezel,  where  it  shows  two  lateral  convex 
articular  facets  for  articulation  with  the  arytgenoid  cartilages.  The  inferior  cir- 
cumference is  related  to  the  first  ring  of  the  trachea  ;  it  has  a  small  notch,  often 
double,  on  the  middle  of  the  bezel. 

Thyroid  Cartilage  (^vpco's,  e'Sos,  "like  a  shield")  (Fig.  311,  t).— This  is 
composed  of  two  lateral  plates,  which  have  the  form  of  an  obliquangular  parallelo- 
gram, and  are  united  at  their  anterior  extremity  to  form  a  thick  constricted  part 
which,  in  Veterinary  Anatomy,  is  named  the  bodi/  of  the  thyroid.  This  body  is 
smooth  on  its  inferior  face,  where  it  is  covered  by  the  terminal  extremities  of  the 
subscapulo-hyoideii  muscles.  On  its  superior  face  is  an  obtuse,  rounded,  and 
irregular  protuberance,  on  which  the  epiglottis  articulates. 

The  plates,  lateral  branches,  or  alcB  of  the  thyroid,  present  two  faces,  two 
borders,  and  two  extremities.  The  external  face,  slightly  convex,  is  covered  by 
the  hyo-thyroideus  and  thyro-pharyngeus  muscles.  The  internal  face,  slightly 
concave,  is  covered,  near  the  superior  border,  by  the  pharyngeal  mucous  mem- 
brane ;  for  the  remainder  of  its  extent  it  is  in  contact  with  the  thyro-arytsenoid 
and  lateral  crico-arytaenoid  muscles. 

The  superior  border  is  divided  by  a  small  prolongation  into  two  parts — an 
anterior,  giving  attachment  to  the  thyro-hyoid  membrane  ;  the  other  posterior, 
into  which  is  inserted  the  palato-pharyngeus  muscle.  This  appendix — the  great 
thyroid  cornu  of  Man — forms  one  of  the  obtuse  angles  of  the  parallelogram  repre- 
sented by  each  lateral  plate  of  the  thyroid  cartilage  ;  it  is  united  to  the  extremity 
of  the  hyoid  cornu  ;  and  at  its  base  is  an  opening,  or  deep  notch,  through  which 
passes  the  superior  laryngeal  nerve.  The  inferior  border  is  also  divided  into  two 
parts  by  the  second  obtuse  angle  of  the  cartilage  :  the  anterior  part  forms,  with 
that  of  the  opposite  plate,  a  receding  angle  occupied  by  the  crico-thyi'oid  mem- 
brane (ligamentum  crico-thyroideum  medium)  ;  the  posterior  gives  attachment  to 
the  crico-thyroid  muscle.  The  extremities  constitute  the  acute  angles  of  the 
thyroid  plate.  The  anterior  joins  that  of  the  opposite  branch,  to  form  the  body 
of  the  cartilage.  The  posterior,  slightly  curved  downwards,  is  terminated  by  a 
small,  convex,  diarthrodial  facet,  which  articulates  with  the  concave  facets  on  the 
external  face  of  the  cricoid  cartilage. 

The  thyroid  cartilage  is  frequently  partially,  or  even  entirely,  ossified. 

Epiglottis  (Fig.  311,  e). — This  is  a  soft  and  flexible  appendage,  shaped  like 
a  sage-leaf  ;  inferiorly,  it  circumscribes  the  entrance  to  the  larynx,  and  is  bent 
over  it,  so  as  to  close  it  hermetically  when  the  aUmentary  bolus  is  traversing  the 
pharyngeal  vestibule. 

This  cartilage  has  two  faces,  two  latercd  borders,  a  base,  and  a  summit.  The 
anterior  face  is  convex  from  side  to  side,  concave  from  above  to  below,  and  covered 
by  the  mucous  membrane  of  the  pharynx  :  it  gives  attachment  to  the  hyo-epiglot- 
tidean  muscle. 

The  posterior  face  shows  an  inverse  configuration,  and  is  covered  by  the  lining 
membrane  of  the  larynx,  which  is  perforated  by  glandular  orifices.  The  borders 
offer  a  free  portion,  which  aids  in  circumscribing  the  entrance  to  the  larynx  ; 
as  well  as  an  adherent  part  fixed  to  the  arytaenoid  cartilage  by  means  of  a  mucous 
fold,  and  made  irregular  by  the  little  cartilaginous  bodies  which  are  superadded 
to  it.  (These  are  the  cuneiform  cartilages,  or  cartilages  of  Wrisberg,  placed  in  the 
arytaeno-epiglottidean  fold  of  mucous  membrane,  which  extends  from  the  apex  of 
the  arytgenoid  cartilage  to  the  side  of  the  epiglottis.)     The  base  is  thick,  and 


530  RESPIBATORT  APPABATUS  IN  MAMMALIA. 

articulates  with  the  middle  part  of  the  thyroid  ;  it  gives  origin,  posteriorly,  to 
two  lateral  prolongations,  which  pass  to  the  inferior  border  of  the  aiytasnoids, 
but  usually  without  joining  these. 

The  summit  unites  the  free  portion  of  both  borders,  and  is  thi'own  forwards 
on  the  upper  face  of  the  soft  palate. 

Arytaenoid  Cartilages  (Fig.  311,  a,  a').  These  two  pieces  have  been  so 
designated  from  their  resemblance,  when  approximated,  to  the  mouth  of  a  pitcher 
(apvratva,  £?8os,  "  like  a  pitcher ").  They  are  situated  in  front  of  the  cricoid, 
above  the  entrance  to  the  larynx  ;  each  has  an  irregular  quadrilateral  form,  and 
presents  for  study  tivo  faces  and  four  borders.  The  internal  face  is  smooth, 
almost  flat,  and  lined  by  the  laryngeal  mucous  membrane.  The  external  face  is 
divided  by  a  ridge  into  two  portions  :  a  superior,  covered  by  the  aryttenoid  muscle  ; 
and  an  inferior,  giving  attachment  to  the  thyro-arytasnoid  and  lateral  crico- 
arytsenoid  muscles.  The  snpen-ior  border  is  concave,  and  joined  to  that  of  the 
opposite  cartilage  (by  means  of  the  ligamentum  crico-ctrijtcenoideum).  The  inferior 
border  {processus  voccdis)  gives  attachment,  posteriorly,  to  the  vocal  cord.  The 
anterior  border,  thick  and  convex,  and  covered  by  the  mucous  membrane,  circum- 
scribes, superiorly  and  laterally,  the  entrance  to  the  larynx  ;  it  is  in  joining 
above,  with  the  homologous  border  of  the  other  arytaenoid  cartilage,  that  the 
pitcher-beak  already  mentioned  is  formed.  The  posterior  border  projects  into  the 
larynx  by  its  inferior  portion  ;  superiorly,  this  border  is  very  thick,  and  is 
hollowed  by  a  small  articular  facet,  which  articulates  with  the  anterior  facet  of 
the  bezel  of  the  cricoid.  Above,  and  to  the  outside  of  this  facet,  is  a  very  promi- 
nent tubercle  {processus  muscularis)  that  terminates  behind  the  crest  of  the 
external  face,  and  gives  attachment  to  the  posterior  crico-arytsenoid  muscle. 

Aeticulations  of  the  Laryngeal  Caetilages  (Figs.  312,  313).— These 
are  of  the  simplest  kind.     They  are  as  follows  : — 

A.  The  thyroid  cartilage  is  joined  to  the  os  hyoides  :  1.  At  the  extremities 
of  the  cornua,  by  means  of  a  short  ligament  interposed  between  that  extremity 
and  the  appendix  of  the  superior  border  of  the  thyroid.  2.  To  the  whole  extent 
of  the  hyoid  concavity,  by  an  elastic  membrane — the  thyro-hyoid  membrane, 
attached  to  the  body  of  the  thyroid  cartilage  and  the  superior  border  of  the  lateral 
plates  of  that  cartilage  (Fig.  313,  4). 

B.  The  thyroid  cartilage  articulates  with  the  cricoid  by  two  small  arthrodiae, 
which  unite  the  posterior  extremities  of  the  branches  of  the  first  cartilage  to  the 
facets  on  the  external  face  of  the  second.  A  thin  external  capsule  encloses  this 
articulation  (Fig.  312,  2).  These  two  cartilages  are  also  held  together  by  means 
of  a  membranous  elastic  ligament — the  crico-thyroid  membrane,  which  passes  from 
the  angle  comprised  between  the  two  branches  of  the  thyroid  to  the  anterior  notch 
of  the  cricoid  (Fig.  313,  3). 

C.  The  two  arytaenoid  cartilages  are  united,  at  their  superior  border,  by  the 
arytenoid  muscle  and  laryngeal  mucous  membrane. 

D.  The  latter  cartilages  come  in  contact  with  the  anterior  facets  of  the  cricoid 
bezel,  by  means  of  the  concave  articular  surface  of  their  posterior  border ;  the 
result  is  a  small,  but  veiy  movable,  arthrodial  joint,  enclosed  by  a  thin  external 
capsule  and  by  the  surrounding  muscles  (Fig.  312,  1). 

E.  These  cartilages  are  also  united  to  the  thyi'oid,  through  the  medium  of 
the  vocal  cords.  These  are  two  elastic  bands  which  project  within  the  larynx, 
and  between  them  include  the  triangular  space  termed  the  glottis ;  their  internal 
face  is  covered  by  the  mucous  membrane  of  the  larynx  ;  the  thyro-hyoid  muscles 


TEE  LARYNX.  531 

envelop  their  external  face  ;  their  inferior  extremity  is  fixed  into  the  crico-thyroid 
membrane,  and  the  angle  of  the  thyi'oid  cartilage  ;  the  superior  is  attached  to  the 
inferior  border  of  the  arytaenoid  cartilage,  towards  the  angle  which  separates  this 
from  the  posterior  border.  The  articulation  of  sounds  is  principally  due  to  the 
vibration  of  these  cords  (Fig.  313,  d). 

F.  The  epigloutis  is  attached  by  amphiarthrosis  to  the  body  of  the  thyroid 
cartilage,  by  means  of  elastic  fasciculi  mixed  with  fat,  which  pass  from  the  base 
of  the  first  to  the  upper  face  of  the  second.  It  is  not  rare  to  find  among  these 
fasciculi  small  synovial  bursas. 

G.  The  epiglottis  is  united,  laterally,  to  the  inferior  border  of  the  arytsenoids, 
through  the  medium  of  the  two  mucous  folds  already  noticed,  in  the  substance 
of  which  are  the  cartilaginous  prolongations  annexed  to  the  base  of  this  fibro- 
cartilage.     These  prolongations  circumscribe,  anteriorly,  the  ventricles  of  the 

Fig.  313. 


SUPERIOR   FACE.  INFERIOR   FACE. 

CARTILAGES   OF   THE    LARYNX,    HELD   IN    THEIR   NATURAL    POSITION    BY    THE    ARTICULAR 

LIGAMENTS. 

a  Cricoid  cartilage;  b,  h,  arytaenoid  cartilages;  c,  body  of  the  thyroid;  c',  c',  lateral  plates  of  the 
thyroid;  d,  epiglottis;  e,  body  of  the  hyoid  bone;  /,  trachea.  1,  Crico-arytsenoid  articulation; 
2,  capsule  of  the  crico-thyroid  articulation ;  3,  crico-thyroid  membrane ;  4,  thyro-hyoid  mem- 
brane ;  5,  crico-trachealis  ligament. 

larynx,  and  are  sometimes  designated  the  superior  vocal  cords — a  name  rarely  given 
them,  as  they  do  not  merit  it. 

H.  Finally,  the  first  ring  of  the  trachea  is  attached  to  the  cricoid  cartilage  by 
a  circular  elastic  membrane. 

All  of  these  articulations  have  neither  the  same  importance  nor  mobility. 
The  kind  of  movements  they  permit  is  easily  understood,  and  they  are  sufficiently 
indicated  in  the  description  of  the  muscles  which  execute  them. 

It  is  sufficient  here  to  state,  that  these  movements  may  either  produce  the 
shortening  or  elongation  of  the  larynx,  its  dilatation  or  contraction  in  a  transverse 
direction,  or  the  occlusion  of  its  anterior  opening. 

2.  Muscles  of  the  larynx. — The  laryngeal  apparatus  is  elevated  or  depressed 
with  the  hjoid  bone,  which  it  follows  in  all  its  movements.     It  is  also  moved 


RESPntATOBT  APPARATUS  IN  MAMMALIA. 


by  proper  muscles,  which  either  produce  its  total  displacement,  or  cause  the 
several  cartilages  to  play  upon  each  other.  Among  these  muscles  there  are  three 
extrinsic — the  sterno-thyroideus,  hyo-thyroideus,  and  the  hyo-epiglottidem.  The 
others  are  intrinsic,  or  attached  in  their  origin  and  termination  to  the  different 
pieces  of  the  larynx  ;  they  are — the  crico-thijroid,  posterior  crico-arytmioid,  lateral 
crico-arytmwid,  thyro-arytmnoid,  and  the  arytCRnoideus  muscles.  All  are  pairs, 
except  the  last  and  the  hyo-epiglottideus. 
Sterno-thyroideus.— (See  p.  255.) 

Hyo-thyroideus  (Fig.  314,  3). — This  is  a  wide,  triangular  muscle,  formed 
entirely  of  muscular  fasciculi,  wliich  arise  from  the  whole  extent  of  the  hyoid 
cornu,  and  terminate  on  the  external  face  of  the  thyroid  ala  ;  the  most  inferior 

are  longest.    This  muscle  covers  the 
Fig.  3U.  thjToid   cartilage   and   the    thyro- 

hyoid membrane.     It  is  covered  by 
the  maxillary  gland.^ 

In  contracting,  this  muscle 
brings  the  thyroid  cartilage  within 
the  branches  of  the  hyoid  bone,  and 
in  this  way  carries  the  larynx  for- 
ward and  upward. 

Hyo-epiglottideus. — This  is 
a  small  cylindrical  fasciculus,  the 
fibres  of  which  are  buried  in  the 
middle  of  a  mass  of  adipose  tissue, 
and  extend  from  the  superior  sur- 
face of  the  body  of  the  hyoid  bone 
to  the  antero-inferior  face  of  the 
epiglottis.  Partly  covered  by  the 
mucous  membrane  of  the  pharynx, 
this  muscle  concurs  in  restoring  the 
epiglottis  to  its  normal  position 
after  the  passage  of  food  or  water 
over  it.  But  it  is  also  necessary 
to  state  that  the  epiglottis  is 
carried  forward  more  particularly  by  its  o^vn  proper  elasticity,  as  well  as  that  of 
the  Ugamentous  bands  that  attach  it  to  the  thyroid  cartilage. 

Crico-thyroideus  (Figs.  314,  11  ;  315,  8). — This  small  muscle,  applied  to 
the  external  side  of  the  cricoid  cartilage,  is  elongated  from  above  to  below,  and 
composed  of  somewhat  tendinous  fibres  which  cross,  more  or  less,  the  general 
direction  of  the  muscle.  They  arise  from  the  above-named  cartilage,  and  pass 
to  the  posterior  border  of  the  thyroid  plate. 

The  crico-thyroideus  shortens  the  laiynx,  in  bringing  together  the  two 
cartilages  into  which  it  is  inserted. 

Posterior  Crico-arytenoideus  (Figs.  314,  315,  5). — This  is  the  most 
powerful  muscle  in  this  region.  Its  fibres  are  directed  forwards  and  outwards, 
and  arise  from  the  bezel  of  the  cricoid,  which  they  cover,  and  from  the  median 
crest  of  that  part.  They  all  converge,  in  becoming  more  or  less  tendinous, 
towards  the  posterior  tubercle  of  the  arytenoid  cartilage,  on  which  they  termi- 
nate. Covered  by  the  oesophagus  and  the  crico-pharyngeal  muscular  band,  this 
('  This  and  the  preceding  muscle  are  usually  described  as  one — the  stvrno-thym-hyoideus.') 


MUSCLES  OF   THE   HORSE'S   LARYNX. 

Hyoideus  transversus ;  2,  kerato-hyoideus  ;  3,  hyo- 
thyroideus  ;  4,  sterno-thyroideus ;  5,  crico-arytae- 
noideus  posticus  ;  6,  crico-arytienoideus  lateralis  ; 
7,  aryteenoideus ;  8,  posterior  fasciculus  of  the 
thyro-arytsenoideus  ;  9,  anterior  fasciculus  of  ditto; 

10,  lateral  ventricle  of  the  larynx  artificially  dis- 
tended and  projecting  between  the  two  fasciculi ; 

11,  crico-thyroideus 


TELE  LARYNX. 


533 


Fig  315. 


muscle  is  separated  from  that  of  the  opposite  side  by  the  median  crest  of 
the  cricoid  bezel. 

The  posterior  crico-arytaenoid  muscles  dilate  the  entrance  to  the  larynx,  as 
well  as  the  glottis,  in  causing  the  arytsenoid  cartilages  to  rotate  or  swing  on  the 
cricoid  cartilage,  and  in  separating  them  from  one  another  by  their  anterior  and 
inferior  borders.     They  act  as  a  lever  of  the  first  order. 

Lateral  Crico-arytsenoideus  (Figs.  314,  6  ;  315,  5).  A  triangular  muscle, 
smaller  than  the  preceding,  situated  between  the  thyroid  and  arytasnoid  cartilages, 
and  formed  of  fasciculi  longer  in  front  than  behind  ;  these  arise  on  the  side  of 
the  anterior  border  of  the  cricoid  cartilage,  and  are  directed  upwards,  to 
terminate  outside  the  posterior  crico-arytte- 
noidens,  on  the  tubercle  of  the  arytaenoid 
cartilage. 

It  is  a  direct  antagonist  of  the  last  muscle, 
and,  consequently,  a  constrictor  of  the  larynx. 

Thyro-arytsenoideus  (Figs.  314,  8,  9  ; 
315, 6). — Lodged  at  the  inner  face  of  the  thyroid 
ala,  this  muscle  comprises  two  fascicuh,  sepa- 
rated by  the  ventricle  of  the  glottis. 

The  anterior  fasciculus  is  a  long  and  pale 
band,  arising  from  the  internal  surface  of  the 
ala  of  the  thyroid  cartilage,  near  its  receding 
angle,  and  ascending  to  the  arytasnoid  cartilage, 
bending  round  its  external  face  to  join  on  the 
median  line,  the  analogous  fasciculus  from  the 
opposite  side,  mixing  its  fibres  with  those  of  the 
arytgenoideus.  By  its  inner  face,  it  covers  the 
superior  vocal  cord  and  the  laryngeal  mucous 
membrane. 

The  posterior  fasdeulus,  wider  than  the 
anterior,  comports  itself  in  a  somewhat  similar 
manner.  It  commences  from  behind  the  same 
point,  and  terminates  on  the  external  crest 
(processus  muscularis)  of  the  arytfenoid  carti- 
lage ;  but  its  most  anterior  fibres  pass  over  this 
crest,  and  join  the  arj^tenoid  muscle.  Its  in- 
ternal face  is  in  contact  with  the  vocal  cord,  and  its  posterior  border  is  con- 
founded with  the  fibres  of  the  lateral  crico-aryttenoideus. 

Sometimes  it  happens  that  these  fasciculi  are  not  distinct  from  each  other, 
and  exist  only  as  a  wide  muscular  band  applied  against  the  ventricle  of  the 
glottis. 

It  is  surmised  that  this  muscle  is  a  constrictor  of  the  larynx.  Its  function 
is  particularly  marked  in  phonation,  when  it  modifies  the  length,  separation,  and 
tension  of  the  vocal  cords. 

Arytsenoideus.—  Situated  beneath  the  pharyngeal  mucous  membrane,  above 
the  arytenoid  cartilages,  this,  the  smallest  of  the  laryngeal  muscles,  is  composed 
of  two  lateral  portions,  the  fibres  of  which  arise  from  a  median  raphe  and,  diverg- 
ing, pass  to  the  superior  part  of  the  external  face  of  these  cartilages,  where  they 
are  inserted  into  the  crest  dividing  that  face,  and  unite  with  the  thyro-arytaenoid 
muscle. 


POSTERO-LATERAL   VIEW   OF   THE 
LARYNX. 

1,  Epiglottis  ;  2,  arvtsenoid  cartilages  ; 
3,  thyroid  cartilage ;  4,  arytsenoi- 
deus muscle ;  5,  crico-arytsenoideus 
lateralis ;  6,  tliyro-arytaenoideus ; 
7,  crico-arytffinoideus  posticus ;  8, 
crico-thyroideus ;  9,  ligament  be- 
tween the  cricoid  cartilage  and  first 
ring  of  trachea,  10;  11,  infero- 
posterior  extremities  of  crico-thyroid 
cartilages. 


534  RESPIRATOBY  APPARATUS  IN  MAMMALIA. 

The  French  works  on  Veterinary  Anatomy  cite  this  muscle — we  do  not  know 
why — as  a  dilator  of  the  larynx.  Its  position  in  front  of  the  crico-arytgenoid 
cartilages  sufficiently  indicates  that  it  cannot  act  otherwise  than  in  bringing  the 
two  arytenoid  cartilages  together.  And  the  continuity  of  a  large  nimiber  of  its 
fibres  with  those  of  the  thyro-arytaenoideus,  does  not  allow  it  to  have  any  other 
action  than  that  of  this  muscle. 

3.  Mucous  membrane  of  the  larynx. — This  membrane  is  only  a  continuation 
of  that  of  the  pharynx,  which,  after  covering  the  prominence  formed  by  the 
opening  of  the  larynx,  passes  over  the  circumference  of  that  opening,  to  be  spread 
on  the  posterior  face  of  the  epiglottis  and  the  internal  face  of  the  arytaenoid 
cartilages,  to  dip  into  the  ventricles,  pass  above  the  vocal  cords,  line  the  inner 
face  of  the  cricoid  cartilage,  and,  finally,  to  be  prolonged  into  the  trachea.  Its 
deep  face  adheres  closely  to  the  parts  it  covers,  except  in  the  lateral  ventricles. 
The  free  face  is  perfectly  tense,  and  is  covered  with  stratified  tesselated  epithelium 
at  the  epiglottis  and  vocal  cords,  but  only  with  ciliated  epithelium  elsewhere. 

The  superficial  layer  of  its  dermis  is  composed  of  reticulated  tissue  except  at 
the  vocal  cords,  where  it  is  closer  and  has  some  papillae  (Coyne). 

The  glanduM  of  the  larynx  are  racemose  ;  they  are  absent  on  the  free  border 
of  the  vocal  cords,  but  are  numerous  on  the  posterior  face  of  the  epiglottis,  where 
they  are  lodged  in  the  minute  depressions  of  the  cartilage  ;  they  are  also  found 
on  the  arytfenoid  cartilages  and  the  arytteno-epiglottidean  folds.  There  are 
closed  follicles  also  in  the  vestibule  of  the  larynx,  at  the  limit  of  the  arytaeno- 
epiglottidean  folds  and  the  epiglottis,  on  the  posterior  surface  of  the  latter. 

The  mucous  membrane  of  the  larynx  possesses  an  exquisite  sensibility,  owing  to 
which  admission  to  the  air-passage  is  denied  to  the  solid  or  liquid  alimentary 
particles,  which,  dm'ing  deglutition,  might  deviate  from  their  normal  course  and 
pass  into  this  opening.  The  slightest  touch  brings  into  play  this  sensibility, 
and  determines  an  energetic  reflex  action  of  the  constrictor  muscles  of  the  larynx 
and  chest ;  from  this  results  the  almost  complete  occlusion  of  the  larynx,  and 
a  violent  cough  which  expels  the  substances  that  have  caused  the  irritation  of  the 
membrane.  Every  one  has  experienced  the  effects  of  this  reflex  action,  and  knows 
by  experience  the  great  sensibility  of  the  larynx. 

4.  Vessels  and  nerves. — Blood  is  carried  into  the  larynx  by  the  laryngeal 
arteries,  which  pass  between  the  cricoid  and  the  posterior  border  of  the  thyroid 
cartilages.  Their  branches  spread  over  the  ventricle  of  the  glottis  and  the  thyro- 
arytfenoid  muscle,  to  be  expended  in  the  substance  of  the  muscles  and  mucous 
membrane.  The  terminal  ramifications  form  red  plexuses  on  the  surface  of  cer- 
tain parts  of  the  larynx.  The  veins  are  satellites  of  the  arteries.  The  lymphatics 
foiTQ  a  superficial  and  a  submucous  network. 

The  pneumogastric  fm'nishes  the  larynx  with  its  principal  nerves — the  superior 
and  inferior  laryngeal.  The  first  is  distributed  to  the  upper  part  of  the  organ 
and  the  entrance  to  the  glottis,  endowing  the  mucous  membrane  with  that  high 
degree  of  sensibility  which  distinguishes  it.  The  second  is  more  especially  a 
motor  nerve,  and  supplies  all  the  muscles,  except  the  crico-thyroid.  A  filament 
of  the  recmTent  nerve  is  distributed  in  the  mucous  membrane  of  the  subglottal 
portion,  and  to  the  inferior  border  and  inner  surface  of  the  vocal  cords.  The 
presence  of  nerve-filaments,  analogous  to  those  of  the  trachea,  in  the  subglottal 
part  of  the  larynx  may  explain  the  difference,  well  known  to  physiologists,  that 
exists  between  the  sensibility  of  the  entrance  to  the  glottis  and  that  of  the  mf  erior 
border  of  the  vocal  cords. 


THE  LARYNX. 


535 


Fig.  316 


External  Surface  of  the  Larynx. — It  is  divided  into  four  planes  :  a 
superior,  inferior,  and  two  lateral.  The  superior  'plane,  formed  by  the  arytaenoid 
and  posterior  crico-arytasnoid  muscles,  is  covered  by  the  pharynx  and  oesophagus  ; 
in  its  anterior  moiety,  it  is  directly  covered  by  the  pharyngeal  mucous  membrane. 

The  inferior  plane  presents,  from  before  to  behiud,  the  thyro-hyoid  mem- 
brane, the  body  of  the  thyroid  cartilage,  the  crico-thyroid  membrane,  the  inferior 
part  of  the  cricoid  cartilage,  and  the  crico-trachealis  ligament.  There  is  remarked, 
laterally,  the  inferior  border  of  the  thyro-hyoid  muscle.  This  plane  corresponds 
to  the  scapulo-hyoideal  muscles,  which  entirely  cover  it. 

The  lateral  planes  exhibit  the  external  faces  of  the  thyro-hyoid  and  crico- 
thyroid muscles,  that  of  the  cricoid  cartUage,  and  the  alae  of  the  thyroid.  They 
also  show  the  opening  through  which  passes  the  superior  laryngeal  nerve ;  they  are 
related  to  the  crico-  and  thyro-pharyngeal  muscles,  as  well  as  the  maxillary  gland. 

Internal  Surface  of  the  Larynx  (Fig.  316). — This  surface  (or  cavum 
laryngis)  is  divided  into  three  perfectly  distiuct  regions  :  a  middle,  named  the 
glottis;  a  s,ni^TioT,ca\]ed  the  supra-glottic  portion ;  and 
an  inferior,  designated  the  infra-  or  sub-glottic  flortion. 

The  glottis  {rima  glottic/is)  is  a  naiTOw  space  in 
the  form  of  a  very  elongated  isoscelated  triangle,  its 
base  being  uppermost.  This  irregular  fissure  is  com- 
prised between  the  elastic  structures  known  as  the 
vocal  cords.     It  is  the  narrowest  part  of  the  larynx. 

(The  space  between  the  vocal  cords  is  designated 
the  glottis  vocalis,  pars  vocalis,  or  interligamentous 
portion  ;  that  between  the  arytgenoid  cartilages,  the 
glottis  respiratoria,  ^mrs  respiratoria,  or  intercartila- 
ginous  portion.) 

The  supra-glottic  portion  {aditus  ad  laryngem, 
introitus  laryngis),  wider  than  the  glottis,  but  always 
greatly  depressed  on  each  side,  particularly  in  the 
region  comprised  between  the  arytenoids,  presents  : 
1.  The  two  ventricles  of  the  larynx  {Morgagni's  ven- 
tricles), lateral  excavations,  dilated  at  the  bottom, 
which  penetrate  between  the  anterior  border  of  the 
vocal  cords  and  the  prolongations  of  the  base  of  the 
epiglottis,  insinuating  themselves  even  between  the 
fasciculi  of  the  thyro-aryttenoid  muscle  (in  the  Ass 
and  Mule  the  ventricles  are  proportionately  larger  than  in  the  Horse,  and  open 
close  to  the  base  of  the  epiglottis).  2.  The  subepiglottic  sinus,  a  deep  depression 
at  the  base  of  the  epiglottis,  which  is  provided,  in  the  Ass  and  Mule,  with  a  thin 
membrane,  capable  of  vibrating.  3.  The  entrance  of  the  larynx,  or  pharyngeal 
opening  of  the  cavity,  a  vast,  gaping  aperture  of  an  oval  form,  circumscribed  by 
the  anterior  border  of  the  arytaenoids  and  the  lateral  border  of  the  epiglottis,  and 
making  a  remarkable  projection  at  the  bottom  of  the  pharyngeal  space. 

The  subglottic  portion  of  the  larynx  is  the  widest  of  the  three  ;  it  is  directly 
continuous  with  the  canal  of  the  trachea.  In  front  is  seen  the  prominence 
formed  by  the  posterior  border  of  the  vocal  cords  :  above,  a  diffused  and  shallow 
excavation,  placed  at  the  point  of  junction  of  the  arytgenoid  and  cricoid  car- 
tilages, named  the  subarytcBuoid  sinus. 

Functions. — A«  a  tube  intended  for  the  passage  of  a  column  of  air  during 


ENTRANCE  TO  THE  LARYNX 
OF  THE  HORSE. 

i,  Glottis ;  B,  epiglottis ;  c, 
entrance  to  the  lateral  ven- 
tricle ;  D,  vocal  cord ;  E, 
oesophageal  infun^iibulum 
opened  ;  f,  f.  posterior  pil- 
lars of  the  soft  palate. 


536  RESPIRATORY  APPARATUS  IN  MAMMALIA 

the  act  of  respiration,  the  larynx  does  not  give  rise  to  any  very  interesting 
physiological  considerations.  It  is,  nevertheless,  worthy  of  remark  that  this 
organ,  like  the  nostrils,  dilates  or  contracts,  according  to  the  volume  of  the 
column  of  air  introduced  into,  or  expelled  from,  the  lungs,  and  that  its  paralysis, 
during  rapid  movements,  causes  an  embarrassment  in  the  respiration  which 
betrays  itself  in  "  roaring."  But  a  physiological  study  of  the  larynx  acquires  a 
real  interest  when  it  is  examined  with  regard  to  the  articulation  of  sounds,  or  as 
an  organ  of  phonation.  This  study,  however,  does  not  come  within  our  province  ; 
though  what  has  been  said  concerning  the  vocal  cords  will  give  a  summary,  but 
satisfactory,  idea  of  the  mechanism  which  presides  over  this  function,  and  the 
part  the  larynx  plays. 

It  may  also  be  added,  that  nearly  all  the  muscles  of  the  larynx  are  concerned 
in  phonation,  as  by  modifying  the  tension  and  the  separation  of  the  vocal  cords, 
they  determine  differences  in  the  sounds.  One  only  is  concerned  in  respiration  ; 
this  is  the  posterior  crico-aryta^noideus,  which  is  a  dilator  of  the  glottis.^ 

2.  The  Trachea  (Figs.  317,  318). 

Preparation.— FoWoy}  the  same  procedure  as  for  the  dissection  of  the  oesophagus. 

The  trachea  is  a  flexible  and  elastic  tube,  formed  by  a  series  of  incomplete 
cartilaginous  rings  that  succeed  the  larynx,  and  terminate  above  the  base  of  the 
heart  by  two  divisions,  which  constitute  the  bronchi. 

Form. — This  tube  is  cylindrical,  and  (slightly)  flattened  above  and  below. 
Its  inferior  face  and  two  borders  are  regularly  rounded,  and  offer  transverse 
grooves,  which  correspond  to  the  intervals  between  the  constituent  pieces  of  the 
trachea.  The  superior  face,  nearly  plane,  shows  the  thin  and  widened  extremities 
of  these  cartilages. 

Course. — Leaving  the  posterior  extremity  of  the  larynx,  the  trachea  descends 
backwards  to  the  entrance  of  the  chest,  in  following  the  inferior  border  of  the 
neck  below  the  longus  colli  muscle.  It  afterwards  becomes  inflected,  superiorly, 
to  pass  between  the  two  first  ribs,  enters  the  chest,  passes  through  the  anterior 
mediastinum,  proceeds  directly  backwards,  and  finally  arrives  above  the  left 
auricle  of  the  heart,  to  the  right  of  the  posterior  aorta,  where  it  bifurcates. 

Relations. — In  its  cervical  portion,  the  trachea,  surrounded  by  a  loose  and 
abundant  connective  tissue,  lies  in  a  kind  of  muscular  envelope  which  the 
majority  of  the  muscles  of  this  region  form  around  it,  and  which  are  :  the 
sterno-hyoid  and  sterno-thyroid,  placed  in  front ;  the  sterno-maxillaries,  situated 
at  first  in  front,  and  afterwards  on  the  sides  towards  their  termination  ;  the 
subscapulo-hyoideii,  above  and  in  the  middle  of  the  lateral  parts  ;  the  scalenii, 
altogether  below  and  at  the  sides  ;  the  longus  colli,  behind  ;  and  outside  all 
these  muscles,  the  superficial  expansion  of  the  cervical  panniculus.  This  enve- 
lope is  thinnest  in  front  of  the  middle  portion  of  the  neck  ;  and  this  is  the  part 
where  the  operation  of  tracheotomy  should  be  performed. 

The  trachea  is  also  in  relation,  in  its  cervical  portion  :  1.  "With  the  oeso- 
phagus, which  descends,  as  we  know,  at  first  in  the  middle  of  the  posterior  face, 
then  to  the  left  side  of  the  air-tube.  2.  With  the  carotid  arteries,  which  pass 
along  both  sides  of  the  tube,  accompanied  by  their  satellite  nerves — the  pneumo- 
gastric,  great  sympathetic,  and  recurrent  nerves. 

('  For  a  special  and  detailed  description  of  the  anatomy  and  physiology  of  the  Horse's 
larynx,  consult  my  work  on  Roaring  in  Horses  {Laryngissimus  paralyticus).     London  :  1889.) 


THE  TRACHEA. 


537 


After  clearing  the  two  first  ribs,  where  it  reaches  its  thoracic  portion,  the 
trachea  responds,  superiorly,  to  the  longus  colli  and  the  oesophagus  ;  below  to 
the  brachial  vessels,  the  anterior  aorta  which  furnishes  them,  the  anterior  vena 
cava,  the  cardiac  and  recurrent  nerves,  and  to  the  base  of  the  heart  ;  laterally, 
to  the  inferior  cervical  ganglia  of  the  great  sympathetic,  the  vertebral  vessels — 
cervical  and  dorso-muscular — and  to  the  two  layers  of  the  anterior  mediastinum  ; 


Fig.  317. 


THE   RESPIRATORY   ORGANS   (INFERIOR,   OR   FRONT   VIEW). 

1,  Trachea;  2,  jugular  vein;  3,  rectus  anticus  major;  4,  carotid  artery  ;  5,  longus  colli;  6,  origin 
of  the  common  carotids;  7,  vertebral  artery;  8,  section  of  first  rib;  9,  cephalic  trunk  of  right 
axillary  artery;  10,  anterior  lobe  of  right  lung;  11,  middle,  or  supplementary  lobe  of  ditto;  12, 
posterior  portion  or  lobe  of  ditto  ;  13,  heart;  14,  cardiac  artery  ;  15,  ventricular  branch  of  cardiac 
vein;  16,  oesophagus. 


to  the  right,  the  vena  azygos  ;  to  the  left,  the  arch  of  the  aorta  and  the  thoracic 
duct.     The  latter  is  sometimes  carried  to  the  opposite  side. 

Steuctuee. — The  trachea  comprises  in  its  structure  :  the  cartilaginous  rings 
which  form  its  base  ;  the  ligaments  which  unite  these  rings  ;  the  mucous  mem- 
hrane  spread  over  its  inner  face  ;  a  muscular  layer,  which  only  lines  that  mem- 
brane superiorly  ;   and  vessels  and  nerves. 

Cartilaginous  rings  of  the  trachea. — These  are  about  fifty  in  number,  and  do 


BESPIRATOEY  APPARATUS  IN  MAMMALIA. 


Fig.  31 


TRACHEA,   BRONCHI,    AND   LUNGS   OF   THE 
HORSE   (VIEWED   FROM    ABOVE). 


not  form  perfect  rings,  being  incomplete 
on  the  upper  side  of  the  trachea.  Each 
is  a  kind  of  arc,  composed  of  a  cartilaginous 
plate  flattened  and  curved  on  itself  ;  the 
extremities  are  turned  towards  each  other, 
and  joined  in  the  majority  of  the  rings  ; 
they  even  overlap  in  some.  These  ex- 
tremities are  thin  and  wide,  and  some- 
times bifurcate  and  unite  with  the  adjoin- 
ing rings. 

In  the  middle  part  of  the  trachea, 
these  rings  are  generally  larger  than  at  the 
origin  or  termination  of  the  tube.  The 
last  ring,  in  serving  as  a  transition  between 
the  trachea  and  bronchi,  presents  a  more 
complicated  arrangement,  being  frequently 
completed  by  isolated  cartilaginous  plates, 
and  always  divided  by  a  median  spur  or 
bifurcation — directed  towards  the  interior 
of  the  trachea — into  two  lateral  segments, 
each  of  which  corresponds  to  a  bronchus. 

Ligaments. — The  rings  of  the  trachea 
are  united  at  their  borders  by  intermediate 
ligaments,  which  are  composed  of  elastic 
tissue,  and  permit  the  lengthening  or 
shortening  of  the  tube  they  concur  to  form. 

Towards  the  extremities  of  the  arcs, 
they  are  confounded  with  a  thin  connec- 
tive-tissue layer  that  unites  these  ex- 
tremities. The  fii-st  cartilage  is  received 
by  its  anterior  border  into  the  cricoid  ring, 
and  joined  to  it  by  the  wide  annular 
ligament  mentioned  at  p.  531.  Owing  to 
the  elasticity  of  tliis  ligament,  the  two 
cartilages  it  binds  together  can  move  one 
within  the  other,  like  two  segments  of 
a  telescope,  and  in  this  way  vary  the  length 
of  the  tube. 

Muscular  layer. — This  layer  only 
covers  the  superior  face  of  the  trachea  ;  it 
is  formed  of  pale,  rose-coloured,  transverse 
fasciculi,  attached  by  their  extremities  to 
the  internal  face  of  the  cartilages.  Its 
action  undoubtedly  diminishes  the  diameter 

A,  Pharyngeal  cavity,  thrown  open  to  show  the  entrance 
to  the  oesophagus,  B,  and  that  of  the  larynx,  c ;  D, 
oesophagus;  E,  left  sac  of  the  stomach;  F,  its  risjht 
sac ;  G,  duodenum ;  H,  trachea ;  i,  right  bronchial 
ramifications;  K,  left  lung;  L,  anterior  aorta;  M, 
common  origin  of  the  bronchial,  oesophageal,  and 
first  intercostal  arteries. 


THE  BRONCHI.  539 

of  the  trachea,  by  contracting  the  arcs  composing  this  tube.  (Kolliker  has  found 
some  longitudinal  fibres  passing  across  the  transverse  ones  at  the  posterior 
part  of  the  trachea.  Leyh  describes  longitudinal  fibres  in  the  anterior  wall  of  the 
trachea,  between  the  mucous  membrane  and  the  cartilaginous  rings,  and  which, 
he  states,  diminish  the  length  of  the  tube.) 

Mucous  membrane. — Continuous  with  that  of  the  larynx,  this  membrane  is 
prolonged,  through  the  medium  of  the  bronchi,  and  in  becoming  modified  in 
character,  into  the  air-cells.  Its  free  or  superficial  surface  is  perforated  by 
glandular  orifices,  and  exhibits  longitudinal  ridges  which  are  ineflfacable  by  dis- 
tension ;  it  is  lined  with  ciliated  epithelium.  Its  deep  face  is  covered  with  yellow 
elastic  tissue  disposed  in  longitudinal  fasciculi,  and  ad- 
Fig.  319.  heres  intimately  either  to  the  face  of  the  cartilage  and 
"  their  intermediate  ligaments,  or  to  the  posterior  muscular 
layer. 

An  essential  characteristic  which  distinguishes  this 
membrane  from  that  lining  the  larynx,  is  its  slight 
sensibility. 

(The  tracheal  glands,  the  orifices  of  which  are  so 
numerous  in  the  mucous  membrane,  abound  towards  the 

CILIATED   EPITHELIUM  .  ^        {■   ^^         ^    ^  xi,  11  •  1    1,    J  • 

FROM  THE  TRACHEA.  postcrior  part  01  the  tube  ;  they  are  small,  ovoid  bodies, 

3,  External  layer  of  longi-  lying  between  the  muscular  and  fibrous  coats.      Other 

tudinal   elastic  fibres ;  glands,  Icss  in  size,  are  placed  between  the  layers  of  fibrous 

fayerofThr'mutus  tissuc  Uniting  the  Cartilages  at  the  sides  of  the  trachea, 

membrane ;    3,   round  Their  secretion  is  poured  out  upon  the  free  surface  of  the 

cells ;  4,  oval  and  ob-  jj^cous  membrane,  to  lubricate  and  protect  it.) 

long   cells:    5,    ciliated  ^^        ,  ,  m,  /,         ,     ■ 

cells.  Vessels   and  nerves. — The   small  arteries   emanating 

from  the  vessels  in  the  vicinity  of  the  trachea — as  the 
carotid  and  the  collateral  branches  of  the  brachial  arteries — supply  it  with  blood. 
Its  nerves  come  from  the  recurrent ;  they  show  small  ganglia  on  their  track. 

Functions. — Except  as  a  tube  for  the  passage  of  the  inspired  and  expired  air. 
the  trachea  performs  no  other  function. 

3.  The  Bronchi  (Figs.  318,  320,  327). 

Preparation. — After  removing  the  lung  from  the  thoracic  cavity,  it  ie  filled  with  water  by 
fixing  the  trachea  to  a  water-tap.  The  bronchi  may  then  be  dissected  by  tearing  and  triturating 
the  pulmonary  tissue. 

Each  of  the  two  bronchi — the  terminal  branches  of  the  trachea — resembles 
a  tree  embedded  in  the  substance  of  the  lung,  and  sending  out  a  multitude  of 
branches. 

Arrangement. — At  a  short  distance  from  their  origin,  the  bronchi  enter  the 
lobes  of  the  lung,  and  pass  backwards  and  outwards  towards  the  superior  part  of 
the  base  of  the  organ,  giving  off  in  their  course  large  collateral  branches,  until 
they  themselves  are  expended.  These  branches  originate  alternately  above, 
within,  below,  and  outwards  ;  and  thus  extend  in  every  direction.  The  first 
forms  an  obtuse  angle  with  the  principal  trunk,  and  is  directed  forwards,  to 
ramify  in  the  anterior  lobe  of  the  lung  ;  the  others  are  detached  at  an  angle 
more  or  less  acute.  All  subdivide  into  gradually  decreasing  branches,  which 
soon  become  of  a  capillary  diameter,  and  finally  open  into  the  infundibula  of 
the  pulmonary  air-cells  (see  Structure  of  the  Lungs). 


540 


RESPIRATORY  APPARATUS  IN  MAMMALIA. 


Form. — The  bronchial  tubes  are  not  flattened  like  the  trachea  ;  a  transverse 
section  shows  them  to  be  regularly  cylindrical. 

Volume. — The  left  bronchus  is  always  smaller  than  the  right,  owing  to  the 
left  lung  being  the  least ;  and  both  are  much  inferior  in  volume  to  the  aggregate 
of  their  respective  branches. 

Relations. — Each  bronchus  enters  the  pulmonary  lobe,  or  lung,  along  with 
the  blood-vessels,  with  which  it  forms  what  is  called  the  root  of  the  lung.  The 
divisions  of  this  aborescent  trunk  are  accompanied  by  the  bronchial  artery,  vein, 
and  nerves,  which  ramify  in  the  same  manner. 

Fig.  320. 


A   SMALL   BRONCHIAL  TUBE,  WITH   ITS   BRONCHULES   AND   ULTIMATE   RAMIFICATIONS. 


Near  their  origin,  the  bronchi  are  related  to  the  bronchial  glands,  above 
which,  and  to  the  left  side,  passes  the  oesophagus. 

Struct  UKE. — The  structure  of  the  bronchial  tubes  resembles  that  of  the 
trachea ;  their  walls  being  formed  by  cartilages,  a  muscular  layer,  mucous 
memhrane,  and  vessels  and  nerves. 

Cartilages  of  the  bronchi. — These  only  exist  in  tubes  of  a  certain  calibre,  the 
minute  tubes  being  deprived  of  them,  and  having  only  membranous  walls.  As 
in  the  trachea,  there  is  for  each  tube  a  series  of  transverse  rings  joined  border 
to  border  ;  though  these  are  no  longer  formed  of  a  single  ring,  but  each  results 
from  the  union  of  several  lozenge-shaped  pieces,  the  extremities  of  which  over- 
lap ;  they  are  united  to  each  other,  like  the  segments  of  the  neighbouring  rings, 
by  means  of  connective  tissue,  and  also  by  the  membranes  spread  over  their 
internal  surface. 


THE  BRONCHI.  541 

Muscular  layer. — Extended  in  a  very  thin  continuous  layer  over  the  entire 
inner  surface  of  the  rings,  this  layer  disappears  in  the  smallest  bronchial  tubes. 

3Iui'ous  membrane. — This  membrane  is  distinguished  from  that  of  the  trachea 
by  its  great  sensitiveness  ;   it  alone  constitutes  the 
walls  of  the  terminal  bronchial  divisions.    (When  the  ^'g-  321. 

cartilages  terminate,  the  tubes  are  wholly  mem- 
branous, and  the  fibrous  coat  and  longitudinal  elastic 
fibres  are  continued  into  the  ultimate  ramifications  of 
the  bronchi.  The  muscular  coat  is  disposed  in  the 
form  of  a  continuous  layer  of  annular  fibres,  and 
may  be  traced  upon  the  smallest  tubes  ;  it  is  com- 
posed of  the  unstriped  variety  of  muscular  fibre.) 

Vessels  and  nerves. — The  vessels  and  nerves  dis- 
tributed in  the  tissue  of  the  bronchial  tubes,  come 
from  the  satellite  vessels  and  nerves  of  these  tubes     „,,„„,,„ 

,  ,  ,   .    ,  .  .  ^  ^,  MUCOUS   MEMBRANE   OF   A   BRON- 

— the   bronchial  arteries,   veins,  and   nerves.     The        chial  tube,  with  the  oapil- 
lymphatics  pass  to  the  bronchial  glands.  laries  injected. 

Differential   Characters  in  the  Air-tube  succeeding  the  Nasal  Cavities  in  the 
OTHER  Animals. 

Ruminants.— In  the  Ox,  Sheep,  and  Goat,  the  interior  of  the  larynx  is  simpler  than  in 
the  Horse,  and  the  lateral  ventricles  and  vocal  cords  are  almost  effaced.  The  most  important 
differences  in  its  various  pieces  are  a.s  follows:  1.  The  thyroid  cartilage  has  no  anterior 
appendices,  but  is  provided,  posteriorly,  with  two  considerable  prolongations  that  articulate 
with  the  cricord  cartilage  (it  has  no  excavation  between  the  two  wings,  and  is  formed  by  a 
single  piece  :  its  inner  face,  in  the  middle,  near  the  lower  border,  has  a  small  fossette  to  which 
a  round  and  very  salient  tuberosity  on  the  external  face  corresponds).  2.  The  upper  border  of 
the  cricoid  is  not  notched  in  front  (neither  is  the  bezel  on  its  lower  border).  3.  The  epiglottis 
is  wider,  but  not  so  pointed,  than  in  Solipeds  (Leyh  says  it  is  less  extensive,  but  thicker). 
4  A  hypo-epiglottidean  muscle  bifid  at  its  origin.  (There  is  no  arytseuo-epiglottidean 
ligament.) 

The  trachea  of  these  animals  does  not  offer  any  important  differences.  The  last  ring  is  not 
so  developed  as  in  tlie  Horse,  and  tlie  tube  detaches  a  supplementary  bronchus  to  a  lobe  of  the 
lung  which  does  not  exist  in  Solipeds.  (The  rings  of  the  mid<lle  portion  are  proportionately 
narrow,  and  their  extremities  meet  behind  and  form  a  salient  ridge.) 

In  the  Camel,  the  larynx  is  long  and  flattened  before  and  behind,  and  the  epiglottis  is  very 
developed;  the  entrance  to  the  larynx  is  triangular  in  shape,  but  its  borders  are  convex 
inwardly.     In  Ruminants  there  are  some  closed  fuUicles  at  the  base  of  the  epiglottis. 

Pig. — The  larynx  of  the  Pig  is  remarkable  for  its  great  mobility,  suspended  as  it  is  to  the 
hyoid  cornua  by  the  base  of  a  very  developed  epiglottis,  rather  than  by  the  wings  of  the  thyroid 
cartilage.  The  epiglottis  is  in  shape  like  an  omega,  is  very  high,  and  curved  backwards  in 
such  a  fashion  as  to  envelop  the  arytsenoids.  There  are  wide,  shallow,  lateral  ventricles,  which 
have  a  small  oblong  sinus  that  ascends  between  the  thyroid  cartilage  and  the  mucous 
membrane.  These  ventricles  are  not  surrounded  by  the  thyro-arytsenoideus  muscle,  which  is 
small  and  undivided;  above  and  outwardly,  tliey  are  margined  by  a  thick  cord — a  kind  of 
superior  vocal  cord,  considered  by  Duges  as  acting  with  the  ventricles  to  modify  the  deep 
grunting  sounds.  (Instead  of  a  tuberosity  on  the  external  face  of  the  thyroid  cartilage,  there 
is  a  median  crest,  and  its  inferior  border  has  a  small  point.  The  cricoid  appears  to  be  drawn 
downwards  and  backwards,  and  its  lower  border  is  very  prominent  in  the  middle,  and  articu- 
lates with  one  or  two  small  cartilaginous  plates  which  have  been  sometimes  wrongly  described 
as  belonging  to  the  proper  cartilages  of  the  larynx.  Tlie  antero-sup(-rior  angles  of  the  arytse- 
noid  cartilages  are  united  to  a  small  cartilaginous  piece  which  prolongs  them  ;  their  external 
face  has  a  spine,  and  the  internal  angles  are  separated  by  a  small  pisiform  body  called  the 
"  interarticular  cartilage.") 

The  trachea  of  this  animal  resembles  that  of  Ruminants.  (It  has  about  thirty  rings,  and 
has  three  bronchi.) 

Cabnivora.— The  larynx  of  the  Dog  and  Cat  is  very  like  that  of  the  Horse.  In  propor- 
87 


542  BESPIEATORY  APPARATUS  IN  MAMMALIA. 

tion,  the  epiglottis  is  shorter,  wider  at  the  base,  and  more  triangular  than  in  the  other  species; 
the  lateral  ventricles  are  sliallow.  (There  is  an  interarticular  cartilage,  as  in  the  Pig  ;  there  is 
no  sub-epiglottidean  ventricle,  and  the  vocal  cords  appear  to  be  nearer  each  other.  The  trachea 
has  about  forty-two  rings,  the  extremities  of  which  do  not  meet ;  the  space  between  them  is 
less  in  the  Cat  than  the  Dog.) 

The  larynx  and  trachea  of  Man  will  be  compared  with  that  of  animals,  when  we  come  to 
describe  the  lungs. 

The  Thorax  (Figs.  255,  322,  323,  324). 

The  thorax — also  called  the  thoracic  or  pectoral  cavity — lodges  not  only  the 
lungs,  but  also  the  heart  and  the  large  vessels  that  arise  from  or  pass  to  that 
organ,  with  a  portion  of  the  oesophagus  and  trachea  ;  as  well  as  nerves,  which 
are  as  remarkable  for  their  number  as  their  physiological  importance. 

Situation. — We  have  seen  that  the  thorax  has  for  its  base  the  bony  cage 
formed  by  the  ribs,  sternum,  and  bodies  of  the  dorsal  vertebrae.  Suspended 
beneath  the  middle  portion  of  the  spine,  this  cage  is  transformed  into  a  closed 
cavity  by  the  intercostal  muscles,  which  fill  the  spaces  between  the  ribs  ;  and  by 
the  diaphragm,  that  vast  oblique  partition  which  separates  the  thora.K  from  the 
abdomen. 

Internal  conformation. — Considered  as  a  whole,  the  thoracic  cavity  represents 
a  hollow  cone  placed  horizontally,  depressed  on  each  side,  and  particularly  in 
front  towards  the  summit ;  with  its  base,  formed  by  the  diaphragm,  cut  very 
obliquely,  in  consequence  of  the  direction  taken  by  that  muscle.  This  obliquity 
of  the  diaphragm  renders  the  antero-posterior  diameter  of  the  cavity  much 
greater  above  than  below  ;  the  difference  is  more  than  double. 

The  internal  surface  of  this  conical  cavity  may  be  divided  into  six  regions  : 
a  superior,  inferior,  and  tivo  lateral  planes,  a  base,  a  posterior  plane,  and  & 
summit. 

The  superior  plane  presents,  on  the  middle  Ime,  a  large  projection  resulting 
from  the  union  of  the  vertebral  bodies  ;  and,  laterally,  two  deep  channels  or 
furrows — the  vertehro-costal  channels.  These  latter,  wider  behind  than  before, 
are  formed  by  the  upper  ends  of  the  ribs  ;  they  lodge  the  superior  border  of  the 
pulmonary  lobes.  The  middle  projection,  or  ridge,  is  comprised  between  these 
two  lobes.  Covered  in  front  by  the  posterior  extremity  of  the  longus  colli,  this 
ridge  is  in  relation  with,  for  the  remainder  of  its  extent,  the  posterior  aorta,  the 
thoracic  duct,  and  the  vena  azygos  ;  on  its  sides  are  seen  the  subdorsal  branches 
of  the  great  sympathetic  nerve. 

The  inferior  plane,  much  shorter  than  the  preceding,  is,  like  it,  narrower  in 
front  than  behind  ;  it  has  for  base  the  superior  face  of  the  sternum,  the  sternal 
cartilages,  and  the  triangularis  sterni  muscle.  Posteriorly,  it  gives  attachment  to 
the  fibrous  sac  containing  the  heart. 

The  lateral  planes,  more  extensive  than  the  other  two,  are  concave  in  both 
their  diameters.  Formed  by  the  internal  face  of  the  ribs  and  the  deep  intercostal 
muscles,  they  are  in  contact  with  the  external  face  of  the  lung, 

The  base,  or  posterior  plane,  formed  by  the  convex  face  of  the  diaphragm,  is 
circumscribed  on  its  exterior  contour  by  the  circle  of  asternal  cartilages,  and  by 
the  last  rib.     In  it  we  see  the  three  openings  in  the  diaphragm. 

The  summit,  or  entrance  of  the  thorax,  is  an  oval  opening,  elongated  vertically, 
comprised  between  the  two  first  ribs  and  the  longus  colli  muscle,  and  which  is 
partly  closed  by  an  enormous  collection  of   lymphatic  glands  ;    through   this 


TEE  THORAX.  543 

opening  passes  the  trachea,  oesophagus,  axillary  and  carotid  arteries,  anterior 
vena  cava,  and  the  pneumogastric,  great  sympathetic,  inferior  laryngeal,  and 
diaphragmatic  nerves. 

Such  is  the  thoracic  cavity.  Like  the  abdomen,  it  is  provided  with  a  serous 
lining,  which  will  now  be  examined. 

The  Pleurae. — The  serous  lining  of  the  thorax  comprises  two  distinct 
membranes,  named  the  pleune,  forming  two  sacs  placed  one  against  the  other  in 
the  median  plane,  and  thus  constituting  a  septum  named  the  mediastinum,  which 
divides  the  thoracic  cavity  into  two  lateral  compartments.  Each  pleura,  there- 
fore, covers  one  of  the  external  or  costal  walls  of  the  thorax,  and  the  correspond- 
ing moiety  of  the  diaphragm  ;  it  is  afterwards  reflected  in  the  vertical  and 
antero-posterior  plane  of  the  cavity,  to  concur  in  the  formation  of  the  media- 
stinum, whence  it  is  carried  over  the  lung.  This  arrangement  exhibits  the 
pleura  in  four  portions  —  a  costal,  diaphragmatic,  mediastinal,  together  represent- 
ing the  parietal  layer  of  the  membrane,  and  a  pulmonary  or  visceral  portion. 

The  costal  pleura  is  applied  to  the  inner  face  of  the  ribs  and  the  internal 
intercostal  muscles.  Strengthened  on  its  adherent  face,  at  each  intercostal  space, 
by  a  layer  of  yellow  elastic  tissue,  this  membrane  is  related,  by  its  free  face,  to 
the  external  surface  of  the  lung,  with  which  it  does  not,  in  a  normal  condition, 
contract  any  adhesions.  It  is  continued  posteriorly,  by  the  diaphragmatic  layer  ; 
in  front,  above,  and  below,  by  the  mediastinal  pleura. 

The  diaphragmatic  pleura  adheres  somewhat  loosely  to  the  fleshy  portion  of 
the  muscle,  but  the  union  is  more  intimate  on  the  aponeurotic  portion.  This 
layer  is  contiguous,  by  its  free  face,  with  the  base  of  the  lung  ;  it  is  confounded 
with  the  mediastinum  by  the  internal  part  of  its  periphery. 

The  mediastinal  pleura  is  placed,  by  its  adherent  face,  against  that  of  the 
opposite  side,  and  in  this  way  produce  the  middle  septum  that  divides  the  thoracic 
cavity  into  two  portions.  Several  organs  are  comprised  between  the  two  layers 
of  this  partition,  but  most  important  of  all  is  the  heart.  In  Veterinary  Anatomy, 
that  part  of  the  septum  in  front  of  this  organ  is  named  the  anterior  mediastinum 
— the  appellation  of  posterior  mediastinum  being  reserved  for  the  portion  situated 
behind  it.  These  terms  have  not  the  same  signification  as  in  human  anatomy, 
though  they  are  retained  here  to  prevent  misunderstanding. 

The  anterior  mediastinum,  thicker  than  the  posterior,  but  much  less  extensive, 
contains,  superiorly,  the  trachea,  oesophagus,  anterior  aorta  and  its  divisions, 
anterior  vena  cava,  thoracic  duct,  and  the  cardiac,  pneumogastric  recurrent,  and 
diaphragmatic  nerves  ;  it  also  includes  the  thymus  gland  in  the  foetus  and  veiy 
young  animal.  ThQ  posterior  mediastinum  is  incomparably  narrower  below  than 
above,  in  consequence  of  the  oblique  position  of  the  diaphragm.  Its  inferior 
part,  always  deviated  to  the  left,  is  extremely  thin,  and  perforated  by  small 
openings,  which  give  it  the  appearance  of  fine  lacework.  Traversed  altogether 
superiorly  by  the  posterior  aorta,  vena  azygos,  and  thoracic  duct,  this  mediastinum 
gives  passage,  a  little  lower  between  its  layers,  to  the  oesophagus,  oesophageal 
branches  of  the  pneumogastric  nerves,  and  to  the  left  diaphragmatic  nerve.  It 
is  these  layers  of  this  mediastinum  which  pass  to  the  lung  to  constitute  the 
pulmonary  pleura,  in  becoming  reflected  above  and  below,  in  a  horizontal  hne 
extending  from  the  root  of  the  pulmonary  lobe  to  the  anterior  face  of  the 
diaphragm. 

The  pulmonary  or  visceral  pleura — a  continuation,  as  has  been  said,  of  the 
mediastinal  pleura — is  in  contact,  by  its  free  face,  with  the  parietal  layer  of  the 


544 


RESPIRATORY  APPARATUS  IN  MAMMALIA. 


membrane.  Its  deep  face  adheres  intimately,  in  Solipeds,  to  the  proper  tissue  of 
the  lungs. 

Independently  of  these  four  serous  layei-s,  the  right  pleura  furnishes  a  special 
fold,  which  arises  from  the  inferior  wall  of  the  thoracic  cavity,  and  ascends  to 
envelop  the  posterior  vena  cava.  This  fold  also  sustains  the  right  diaphragmatic 
nerve. 

In  order  to  study  the  various  portions  of  the  pleurse  collectively,  with  their 
reciprocal  relations,  and  their  connections  with  the  organs  contained  in  the 
thoracic  cavity,  we  will  suppose  three  transverse  sections  of  this  cavity  :  one 
passing  behind  the  heart ;  the  other  at  the  roots  of  the  lungs,  and  dividing  the 
left  ventricle  of  the  heart  ;  the  third  traversing  the  anterior  mediastinum,  a  little 
in  front  of  the  right  ventricle. 

If,  in  the  first  section  (Fig.  322),  we  take  the  costal  pleura  at  the  point  a, 
and  follow  it  up  to  b,  we  shall  see  it  folded  downwards  to  form  the  mediastmal 
layer,  to  be  applied  to  the  aorta,  c,  and  the  oesophagus,  d ;  then  reflected  at  e  on 
the  lung,  /,  enveloping  every  part  of  the  organ  ;  returning  to  the  point  e,  it 


Fig.  322 


Fig.  323. 


THEORETICAL    SECTIONS    OF    THE    THORACIC    CAVITV,    INTENDED    TO    SHOW    THE    DISPOSITION    OF 
THE    PLEURA. 


leaves  the  lung,  is  again  reflected  to  achieve  the  formation  of  the  mediastinal 
septum,  h  g,  and  finally  regains  the  point  it  started  from.  On  the  right  side, 
with  only  a  slight  variation,  it  has  the  same  arrangement.  After  being  carried 
from  the  point  a'  to  //,  then  to  e',  and  after  enveloping  the  lung,  returning  to  e\ 
and  being  reflected  in  the  median  plane  to  the  point  g',  the  right  pleura  leaves 
the  inferior  thoracic  wall  to  pass  around  the  posterior  vena  cava,  and  come  back 
to  a',  its  point  of  departure. 

The  second  section  (represented  by  Fig.  323),  shows  the  pleura  arrived  at  the 
point  h,  descending  on  the  root  of  the  lung,  c,  covering  that  organ  and  returning 
to  c,  and  reflected  on  the  pericardium,  d,  to  gain  the  point  a. 

In  the  third  section  (Fig.  324),  we  see  the  parietal  pleura,  a  b,  without  any 
points  of  continuity  with  the  visceral  pleura,  c.  It  is  at  the  level  of  this  section 
that  the  lung  forms  two  perfectly  free  lobes,  which  are  not  attached  to  the 
anterior  mediastinum. 

Structuee. — Like  all  the  serous  membranes,  the  pleurae  have  a  free  face 
covered  by  a  perfectly  smooth  endothehum,  always  in  contact  with  itself,  and 


TEE  THORAX.  545 

constantly  lubricated  by  a  serous  fluid  which  facilitates  the  gliding  of  the  lung 
on  the  parietes  of  the  thoracic  cavity.  The  deep  face  is  united  to  the  subjacent 
parts  by  connective  tissue  destitute  of  fat  ;  the  adherence  of  the  visceral  pleurae 
is  most  intimate. 

The  pleura  has  plexuses  of  vessels— one,  the  subserous,  has  large  meshes  ;  but 
a  second,  the  endothelial,  has  a  finer  network. 

The  nerves  are  from  the  sympathetic  and  pneumogastric  for  the  pulmonary 
pleura ;  from  the  diaphragmatic  and  intercostal  nerves  for  the  parietal 
pleura. 

Functions. — The  thorax  is  not  a  mere  receptacle,  but,  on  the  contrary, 
performs  a  very  important  part  in  the  act  of  respiration.  We  know,  in  fact,  that 
it  is  dilated  and  contracted  by  the  movements  of  the  diaphragm  and  the  ribs 
(see  pp.  193,  310).  The  limgs,  being  apphed  immediately  against  the  thoracic 
walls,  and  never  at  any  time  separate  from  them,  follow  this  cavity  in  then- 
movements — dilating  in  inspiration  and  contracting  in  expiration,  after  a  certain 
quantity  of  the  oxygen  of  the  inspired  air  has  been  removed  and  replaced  by  an 
equivalent  amount  of  carbonic  acid. 

The  movements  of  the  thorax  are,  therefore,  of  capital  importance,  constitut- 
ing, as  they  do,  the  initial  phenomenon  of  respiration,  and  having  dependent  on 
them  all  the  other  acts  of  this  function. 

Differential  Characters  in  the  Thorax  of  the  other  Animals. 

In  the  Ox,  the  thorax  is  not  so  long,  particularly  in  its  superior  part,  as  in  Solipeds,  by 
reason  of  the  slight  obliquity  of  the  diaphragm,  and  of  its  mode  of  attachment  to  the  ribs. 

The  total  capacity  of  this  cavity  is  also  certainly  inferior  to  that  of  the  Horse's  chest.  It  is 
the  same,  though  relatively  more  extensive,  in  the  Sheep,  Goat,  and  Pig ;  while  the  Dog 
possesses  in  this  respect  an  incontestable  superiority  over  Solipeds.  It  is  to  be  noted  that  all 
these  animals,  without  exception,  are  distinguished  from  the  Horse,  Ass,  and  Mule  by  the  con- 
formation of  the  posterior  mediastinum.  In  them  it  is  not  open  in  its  lower  part,  but  as  solid, 
thick,  and  complete  there  as  elsewhere.  Therefore  it  is  that  the  consecutive  effusion  of 
pleuritis  is  readily  localized  in  one  of  tlie  pleural  sacs  in  tiie  first-named  animals,  while  this 
localization  is  impossible  in  the  second.  (This  is  an  important  observation,  from  a  pathological 
point  of  view ;  but  it  is  to  be  noted  that  exceptional  instances  have  been  recorded,  in  which 
the  posterior  mediaotinum  of  the  horse  has  been  found  imperforate. 

The  Lung  (or  Lungs)  (Figs.  318,  321,  325,  326). 

Preparation. — The  disposition  of  the  lung  in  the  thoracic  cavity  is  best  studied  by  placing 
the  subject  in  the  second  position,  opening  the  chest  by  excision  of  the  ribs,  as  in  Fig.  322, 
and  inflating  the  organ  by  the  trachea.  To  study  its  external  conformation,  it  should  be 
removed  from  the  cavity,  with  the  heart  and  large  vessels,  and  inflated  as  before. 

Situation — General  disposition. — This  essential  organ  of  respiration  is  a  spongy 
viscus,  lodged  in  the  thoracic  cavity,  and  divided  into  two  lateral,  but  inde- 
pendent, moieties,  each  of  which  occupies  one  of  the  two  serous  sacs  formed  by 
the  plurse.  It  is  also  described  as  fivo  jnilmonary  lobes,  or  tivo  lungs — a  right  and 
left,  the  latter  a  little  less  voluminous  than  the  former. 

Form  and  Relations. — Together,  the  lungs  affect  the  outline  of  the  thoracic 
cavity  ;  each  represents  the  moiety  of  a  cone,^  and  offers  for  study  :  an  external 
and  internal  face,  a  base  and  summit,  and  a  superior,  inferior,  and  posterior 
border. 

*  This  is  not  the  natural  shape  of  the  lungs,  and  is  only  assumed  when  the  chest  is  opened, 
and  their  elasticity  is  no  longer  counterbalanced  by  the  atmospheric  pressure,  except  at  the 
external  surface  of  the  bronchi. 


546 


RESPIRATORY  APPARATUS  IN  MAMMALIA. 


The  external  or  costal  face  is  convex  (and  smooth),  and  moulded  to  the 
external  wall  of  the  thorax. 

The  internal,  or  mediastinal  face,  forms  a  vertical  plane,  separated  from  the 
opposite  lung  by  the  mediastinum.  It  shows  :  1.  A  small  anterior  portion  in 
contact  with  the  anterior  mediastinum.  2.  At  the  heart,  an  excavation  in  which 
that  organ  is  lodged.  3.  Immediately  behind  this  excavation,  and  a  little  above 
it,  the  root  of  the  lung  {hilum-pulmonis) — a  fasciculus  formed  by  the  air-tubes  and 
pulmonary  vessels  in  entering  the  viscus.  4.  A  posterior  portion,  more  extensive 
than  the  other  two  put  together  corresponding  to  the  posterior  mediastinum, 


LUNG  OF   THE  HORSE,  SUSPENDED  BY  THE  TRACHEA    (VIEWED  BY  ITS  BASE  AND    INFERIOR  BORDER). 

T,  Trachea;  L,  L',  anterior  lobes;  E,  E',  cavity  for  the  heart ;  Ap,  Ap,  branches  of  the  pulmonary 
artery  at  their  entrance  to  the  heart;  Vp,  Vp,  pulmonary  veins  at  their  emergence  from  the 
lung  ;  F,  F,  external  face  of  the  lobes  of  the  lung  ;  D,  D,  base  of  the  lung,  or  diaphragmatic  face 
of  the  two  lobes;  H,  internal  lobule  of  the  right  lobe  ;  I,  channel  for  the  posterior  vena  cava; 
0,  oesophagus  passing  between  the  two  lobes  (a  certain  retraction  of  the  organ  appears  to  make 
it  pass  between  the  lobe  and  lobule  of  the  right  lung). 


and  attached  to  that  septum  by  means  of  a  fold  developed  around  the  organ,  to 
form  the  pulmonary  pleura  ;  this  fold  constitutes,  posteriorly,  a  small  serous 
ligament  {ligamentum  latum  pulmojiis),  attached  at  once  to  the  mediastinum  and 
the  posterior  face  of  the  diaphragm.  On  this  portion  of  the  lung  are  remarked 
two  antero-posterior  furrows  :  one,  near  the  upper  border  of  the  organ,  to 
receive  the  thoracic  aorta  ;  the  other  situated  lower,  but  not  so  deep,  more 
marked  in  the  left  than  the  right,  and  lodging  the  oesophagus.     In  the  right 


TEE  LUNGS.  547 

lung,  this  mediastinal  face  offers  a  small  particular  lobule,  which  is  absent  in 
the  left. 

The  base,  or  diaphragmatic  face  of  the  lung,  cut  obliquely  downwards  and 
backwards,  is  concave,  and  moulded  to  the  anterior  face  of  the  diaphragm.  On 
the  right  lung  is  seen  the  posterior  face  of  the  small  lobule  noticed  on  the  inner 
side,  and  a  deep  fissure  between  it  and  the  principal  lobe,  for  the  passage  of  the 
posterior  vena  cava. 

The  summit  of  the  viscus,  situated  behind  the  first  rib,  presents  a  kind  of 
detached  appendix — the  anterior  lobule  of  the  lung. 

The  superior  border,  thick,  convex,  and  rounded,  is  lodged  in  the  vertebro- 
costal channel  or  concavity.  The  inferior,  much  shorter  and  thinner,  is  deeply 
notched  at  the  level  of  the  heart,  and  more  so  on  the  left  than  the  right  side. 
The  posterior  is  elliptical,  and  everywhere  circumscribed  by  the  face  of  the 
diaphragm,  which  it  separates  from  the  costal  and  mediastinal  faces. 

Structure. — An  external  serous  envelope,  proper  fundamental  tissue,  functional 
and  nutrient  vessels,  lymphatics,  and  nerves :  such  are  the  elements  which  enter 
into  the  organization  of  the  lung. 

Serous  Envelope. — This  is  the  pleura  pulmonalis  already  described. 
Lymphatic  stomata  are  observed  on  its  surface.  (There  has  also  been  described 
a  subserous  connective  tissue,  containing  a  large  proportion  of  elastic  fibres  ;  it 
invests  the  entire  surface  of  the  lung,  and  extends  between  the  lobules.) 

Fundamental  Tissue.  Physical  characters. — The  pulmonary  tissue  in 
the  adult  is  of  a  bright  rose-colour ;  it  has  a  deeper  hue  in  the  foetus  which 
has  not  respired.  Although  soft,  it  is  yet  very  strong  and  resisting,  and  can 
with  difficulty  be  torn.  Its  elasticity  is  remarkable,  and  is  the  cause  of  the 
collapse  the  lung  experiences  when  air  is  admitted  to  the  pleural  sacs.  It  is 
very  light — plunged  in  water,  if  healthy,  it  floats  ;  this  specific  lightness  is  due 
to  the  air  imprisoned  in  the  pulmonary  infundibula.  This  may  be  proved  by 
what  takes  place  when  the  lung  of  a  foetus  is  inflated  :  heavier  than  water 
before,  it  then  becomes  lighter,  because,  notwithstanding  all  the  manipulation 
that  may  be  employed  to  expel  the  air  introduced  into  the  pulmonary  vesicles,  a 
certain  quantity  always  remains.  On  the  other  hand,  the  absolute  weight  of  the 
lung  is  relatively  more  considerable  in  the  adult  than  in  the  foetus,  the  first 
representing  ^^  of  the  total  mass  of  the  body,  while  it  is  only  ^V  i^  the  second. 

A  knowledge  of  these  facts  may  be  utilized  in  determining  whether  a  given 
lung  has  belonged  to  an  animal  which  has  respired,  or  has  died  before  birth. 
If  the  tissue  is  plunged  in  water,  this  test  is  called  hydrostatic  pulmonary 
docimacy  ;  if  its  relative  weight  is  to  be  ascertained,  it  is  designated  pulmonary 
docimacy  by  weight. 

These  are  the  physical  characters  of  the  fundamental  tissue  of  the  lung  ;  we 
will  now  study  its  anatomical  characters. 

Anatomical  characters. — The  pulmonary  tissue  is  divided  into  a  great  number 
of  small  polyhedral  lobules  by  septa  of  connective  tissue,  which  appear  to  be 
prolongations  of  the  corium  of  the  enveloping  serous  membrane.  This  segmen- 
tation into  lobules  is  a  common  feature  in  the  organization  of  the  lungs  in  the 
Mammalia,  but  it  is  more  readily  demonstrated  in  some  than  others  :  not  very 
evident  in  Solipeds,  and  less  so  in  the  Carnivora,  it  is  well  defined  in  Rumi- 
nants and  Pachyderms. 

As  the  lobule  constitutes  the  genetic  unit  of  the  lung,  we  will  study  its 
organization  in  detail,  as  has  been  already  done  with  regard  to  the  hepatic 


548 


RESPIRATORY  APPARATUS  IN  MAMMALIA. 


lobule.  It  forms  a  small  pyramid  with  a  polygonal  base,  measiirins:  about  ^  of  a 
cubic  inch,  and  is  sm-rounded  by  a  layer  of  connective  tissue  which  unites  it  to 
the  neighbouring  lobules,  and  in  which  are  some  lymphatics  and  the  network 
formed  by  the  pulmonary  vein.  It  appears  to  be  suspended  by  its  summit  to  a 
very  short  pedicle  consisting  of  :  1.  A  sublobular  bronchiole  of  about  0'039  inch 
in  diameter.  2.  A  twig  of  the  bronchial  artery.  3.  A  branch  of  the  pulmonary 
artery.  4.  A  division  of  the  pulmonary  vein.  While  the  first  three  elements  of 
the  pedicle  enter  the  lobule,  the  fom-th  deviates  suddenly  and  becomes  a  capillary 
network  on  its  outer  surface. 

In  the  lobule,  the  sublobular  bronchule  is  named  the  intra-lobular  bronchiole; 
it  gives  off  the  lateral  intra-lobular  hi^onchioles  in  passing  towards  the  base  of  the 
lobule,  where  it  throws  off  at  last  two  terminal  bronchioles.  Each  lateral  bron- 
chiole comports  itself  like  the  intra-lobular  one,  and  terminates  in  the  same 

Fig.  326. 


LUNG  OF   THE  HORSE   RESTING  ON  ITS  DIAPHRAGMATIC   SURFACE,  AND  VIEWED  BY  ITS    ANTERIOR 

EXTREMITY. 

T,  Trachea ;  D,  right  lobe ;  G,  left  lobe ;  L,  anterior  lobule  of  the  right  lobe ;  L',  anterior  lobule 
of  the  left  lobe  ;  Ap,  branches  of  the  pulmonary  artery  at  their  entrance  into  the  two  lobes  ; 
F,  F',  notch  on  the  right  and  left  of  the  inferior  border  of  the  lung,  in  face  of  the  heart;  E,  notch 
on  the  upper  border  for  the  passage  of  the  aorta  ;  V,  V,  openings  of  the  pulmonary  veins  ;  La, 
lobule  of  the  right  lung ;  S,  fissure  for  the  passage  of  the  posterior  vena  cava. 


manner — by  two  short  or  acinous  bronchioles,  about  ^^  of  a  millimetre  in 
diameter. 

At  the  extremity  of  each  of  the  terminal  bronchioles — short  or  acinous — is 
suspended  a  small  pyramidal  mass  of  2  to  3  cubic  millimetres — the  acinus.,  which 
at  first  showing  an  initial  dilatation — the  vestibule,  afterwards  gives  off  three, 
four,  or  five  divergent  tubes  of  from  ^  to  f  of  a  millimetre — the  alveolar  passages, 
or,  better,  respiratory  canaliculi.  These  are  sacculated  on  their  surface  and 
expanded  at  their  termination,  so  as  to  resemble  small  bunches  of  grapes  in 
which  the  fruit  is  not  very  distinct  from  the  stalk.  The  terminal  dilatations  are 
named  infundihnla,  and  the  boss-like  portions  alveoli,  or  pulmonary  vesicles. 

The  ramifications  of  the  bronchial  artery  are  expended  in  the  tissue  of  the 
bronchioles,  and  do  not  extend  beyond  the  commencement  of  the  alveoli  and 
infundibula  ;  while  the  branches  of  the  pulmonary  artery  accompany  the  bronchi, 
and  become  capillaries  in  the  walls  of  the  alveoli  and  infundibula.     In  this  way 


TEE  LUNGS. 


the  conductive  and  the  respiratory  parts,  properly  speaking,  of  the  lung  have 
an  organic  independence,  just  as  they  have  a  physiological  and  pathological 
individuahty. 

The  elements  of  the  pedicle,  in  ramifymg  in  the  lobule,  caiTy  with  them  a 
certain  amount  of  connective  tissue. 

To  demonstrate  the  structure  of  the  lung, 
and  sections  afterwards  made  to  show 


the  pulmonary  alveoli.  But  this 
procedure  has  the  inconvenience  of 
unduly  distending  these  small  cavities 
by  thinning,  and  even  destroying, 
their  walls.  A  better  method  is  the 
following :  leave  the  lung  in  the 
intact  thoracic  cavity  ;  by  the  jugular 
vein,  pour  into  the  right  side  of  the 
heart  an  injection  of  very  hot  tallow, 
employing  a  certain  amount  of  force 
to  propel  it  from  the  pulmonary 
artery  into  the  veins ;  when  this 
injection  has  cooled,  open  the  thoracic 
cavity,  and  take  out  the  lungs 
These,  being  impregnated  with  solidi- 
fied fat,  do  not  collapse  on  contact 
with  the  air,  and  sections  made  in 
different  directions  then  exhibit  in- 
numerable perfectly  circular  porosi- 
ties, which  are  the  open  pulmonary 
vesicles. 

In  this  way  it  is  easy  to  demon- 
strate the  presence  of  the  air-cells ; 


it  may  be  inflated  and  dried, 
Fig.  327. 


CAST   OF   A    PRETERIIIXAL   AND   TERMINAL   BRON- 
CHIOLE,   FROM   THE    LUNG   OF   THE   ASS. 

I,  Bronchiole  of  1§  millimetre  in  diameter;  2,  2, 
ramifications  ^  a  millimetre  in  diameter;  3,  3,  3,  3, 
sublobular  bronchioles ;  4,  ramifications  of  an 
intra-lobular  bronchiole;  5,  5,  infundibula  ;  6,  6,  6, 
respiratory  canaliculi ;  7,  pulmonary  alveoli  ;  8, 
debris  from  the  canaliculated  part  of  a  pulmonary 
lobule;  9,  acinus.  A  point  has  been  chosen 
where  the  moulding  of  a  great  number  of  alveoli 
and  acini  failed,  in  order  to  show  the  divisions  of 
the  bronchi  better.     Magnified  5  diameters. 


but,  in  order  to  conveniently  study 
their  arrangement,  it  is  necessary  to  take  a  cast  of  them  by  means  of  a  solidi- 
fiable  material  introduced  by  the  bronchi,  and  afterwards  destroyed  by  the 
maceration  of  the  pulmonary  tissue.  The  Darcet  alloy,  employed  in  this  manner, 
often  gives  very  good  results,  as  seen  in  figures  327,  328. 

We  will  follow  the  preceding  details  on  the  interior  of  the  lung,  with  some 
words  on  the  structure  of  its  different  parts. 

The  bronchiole,  on  entering  the  lobule,  has  all  the  elements  of  the  larger 
bronchi — cartilaginous  rings,  a  layer  of  racemose  mucous  glands,  muscular  layer, 
festooned  mucous  membrane,  and  ciliated  epithelium ;  but  as  it  divides  and 
becomes  smaller,  its  composition  is  modified.  The  intra-lobular  bronchioles  suc- 
cessively lose  their  cartilages,  the  glandular  layer,  and  the  contractile  layer,  and 
at  last  at  the  acini  the  mucous  layer  is  reduced  to  its  basement  membrane,  and 
the  epithelium  becomes  cubical.  The  walls  of  the  infundibula  are  formed  by  a 
thin  amorphous  membrane  strengthened  externally  by  some  connective  tissue  and 
an  elastic  network  ;  while  the  interior  is  lined  by  a  row  of  flat  cells,  the  outline 
and  nuclei  of  which  can  easily  be  made  out  in  the  adult  animal.  The  capillaries 
form  an  extremely  rich  network  spread  outside  the  proper  membrane — though 
sometimes  they  enter  its  substance,  and  push  the  epithelium  towards  the  centre  of 
the  alveolus. 


550 


RESPIRATORY  APPARATUS  IN  MAMMALIA. 


(The  minute  polygonal  cells  lining  the  air  or  pulmonary  vesicles  measure  from 
TffW  to  ^TD^  of  an  inch  in  diameter,  and  from  ^winj  <^o  ^^5^  of  an  inch  in  thick- 
ness. Between  the  vesicles  is  a  tra- 
p's- 328.  becular  tissue,  mainly  composed  of 
yellow  elastic  with  a  few  muscular 
fibres,  some  of  which  are  united  with 
the  lining  membrane  to  strengthen  it, 
especially  around  the  apertures  of 
communication  between  the  adjoining 
air-cells. 

The  capillaiy  plexuses  are  so  ar- 
ranged between  the  two  layers  forming 
the  walls  of  two  adjacent  cells,  as  to 
expose  one  of  their  surfaces  to  each, 
in  order  to  secure  the  influence  of  the 
air  upon  them.  These  networks  are 
so  close,  that  the  diameter  of  the 
meshes  is  scarcely  so  great  as  that  of 
the  capillaries  which  enclose  them.) 

Vessels. — The  lung  is  a  very 
vascular  organ.  The  numerous  rami- 
fications it  receives  divide  into  two 
orders — the  functional  and  the  nutri- 
tive vessels. 

Functional  vessels  of  the  lung. — 
The  blood  is  returned  from  all  parts 
of  the  body  by  the  veins,  after  losing, 
along  with  its  bright  red  colour,  the  properties  which  render  it  fit  to  maintain 
the  vitality  of  the  tissues.  It  thus  arrives  at  the  right  side  of  the  heart,  whence 
it  is  propelled  into  the  lung,  there  to  be  regenerated  by  mediate  contact  with  the 
air.  It  is  the  pulmonary  artery  which  conveys  this  fluid  into  the  parenchyma  of 
the  organ,  and  by  the  pulmonary  veins  it  is  carried  back 
to  the  heart.  The  artery  is  at  first  divided  into  two  branches, 
which  ramify,  and  finally  terminate  in  dense  capillary  plexuses 
upon  the  walls  of  the  infundibula.  The  veins — innumerable 
and  attenuated  at  their  origin,  like  the  arterial  capillaries 
— terminate  in  from  four  to  eight  principal  trunks,  which 
open  into  the  left  auricle  of  the  heart. 

The  branch  of  the  pulmonary  artery  that  enters  each 
lobule,  is  regarded  as  terminal — that  is,  it  does  not  anas- 
tomose directly  with  the  arteries  of  the  neighbouring  lobules  ; 
on  the  contrary,  the  interlobular  branches  of  the  pulmonary 
vein  are  in  relation  with  the  capillary  network  of  the  adjoin- 
ing lobules. 

These  two  orders  of  vessels,  which  necessarily  participate 
in  the  physiological  functions  of  the  lung — like  the  vena 
port*  with  the  liver — are  very  justly  distinguished  from  the 
other  arteries  or  veins,  by  the  designation  o(  functional  vessels.  But  though  they 
are  so  named,  it  must  not  be  inferred  that  they  are  excluded  from  all  partici- 
pation in  the  acts  of  nutrition. 


CAST  OF  A  PORTION  OF  THE  BRONCHIAL  DIVISIONS 
AND  SOME  LOBULES  AND  ACINI,  FROM  THE  LUNG 
OF   THE   ASS. 

1,  Bronchiole,  IJ  millimetre  in  diameter;  2,  2,  2, 
ramifications  of  1  millimetre  ;  3,  3,  3,  3,  sub- 
lobular  bronchioles ;  4,  4,  4,  intra-lobular 
bronchial  divisions  ;  5,  5,  acini ;  6,  6,  respiratory 
canaliculi ;  7,  7,  infundibula;  8.  8,  8,  mould  of 
complete  lobules.  It  was  necessary  to  break 
away  a  number  of  lobules  in  order  to  show  these. 
Magnified  5  diameters. 


Fig.  329. 


PLAN  OF  A  PULMO- 
NARY LOBULE. 

a,  Bronchiole  termi- 
nating in  a  slight 
dilatation,  b  ;  c,  air- 
sacs,  or  infundibuli; 
d,  air  or  pulmonary 
vesicles. 


TEE  LUNGS. 


55] 


Nutrient  vessels. — By  this  name  is  designated  the  divisions  of  the  bronchia] 
arteries  and  vei7is,  the  terminal  ramifications  of  which  anastomose  with  the  capil- 
laries of  the  pulmonary  vessels  at  the  ultimate  bronchules. 

It  is  generally  admitted  that  the 
two  arterial  systems — bronchial  and 
pulmonary — are  independent  of  each 
other,  and  also  of  the  general  circu- 
lation. Kiittner  believes  he  has  in 
several  ways  demonstrated  the  exist- 
ence of  communications  between 
bronchial  and  pulmonary  arterioles, 
and  between  the  latter  and  the  sub- 
pleural  arterioles. 

Lymphatics. — These  vessels  are 
divided  into  superficial  and  deep.  The 
first  form  a  network  beneath  the 
pleura ;  the  second  exist  in  large 
numbers  around  the  lobules.  They 
mix  and  terminate  in  the  bronchial 
glands  ;  but  before  doing  so,  they 
enter  the  small  lymphatic  masses  dis- 
seminated in  the  texture  of  the  lung, 
in  the  neighbourhood  of  the  bronchi. 
There  are  also  interlobular  lymphatics 
which  follow  the  ramifications  of  the 
bronchi  and  pulmonary  artery.  (Lym- 
phatics of  very  small  size  have  been 
described  as  commencing  in  the 
alveolar  spaces,  on  leaving  which  they  gain  a  proper  coat  or  internal  tunic,  and 
are  subsequently  supplied  with  valves.) 

Nerves. —The  nerves  supplied  to  the  tissue  of  the  lung  come  from  the  same 
source  as  those  of  the  bronchial  tubes — 
the  pneumogastric  and  great  sympathetic 
nerves.  Their  ramifications  accompany 
the  pulmonary  vessels  and  bronchi, 
and  they  show  small  ganglia  on  their 
course. 

Functions. — To  know  that  the  lung 
is  the  seat  of  the  absorption  of  oxygen 
and  the  expulsion  of  carbonic  acid  from 
the  nutritive  fluid — phenomena  accom- 
panied by  the  transformation  of  the  dark 
into  red-coloured  blood,  and  the  cooling 
of  the  venous  blood — is  the  only  authen- 
tic fact  necessary  to  remember  with 
regard  to  the  functions  of  this  organ. 
It  must  be  added  that  the  operations 
from  which  all  these  phenomena  result, 

take  place  in  the  lung  by  the  mediate  contact  of  the  atmosphere  introduced 
into  the  pulmonary  alveoli  during  inspiration,  with  the  blood  traversing  the  walls 


INFUNDIBULA   OF   LUNG,    WITH    INTERVENING 
TISSUES. 

a.  Epithelium;  b,  elastic  trabeculae;  c,  membranouB 
wall,  with  fine  elastic  fibres. 


Fig.  331. 


ARRANGEMENT   OP   THE   CAPILLARIES   AROUND 
THE   INFUNDIBULA. 


552  RESPIBATORY  APPARATUS  IN  MAMMALIA. 

of  these  spaces.     With  the  intimate  mechanism  of  these  actions  we  have  nothing 
to  do  here,  however. 

Development. — Although  the  lung  is  in  a  state  of  inactivity  in  the  foetus, 
yet  it  is  one  of  the  early  developed  organs.  During  the  whole  period  of  foetal 
existence,  its  lobular  texture  is  much  better  defined  than  in  the  adult,  and  it 
then  appears  to  be  formed  exactly  like  a  racemose  gland.  Sections  of  it  prepared 
for  microscopical  examination,  distinctly  show  the  vesicles  and  their  arrangement. 
We  have  already  made  known  the  differences  in  colour  and  density  which  dis- 
tinguish the  pulmonary  tissue  of  the  foetus  and  that  of  the  adult.  It  only 
remains  to  repeat  what  has  been  said  as  to  the  slight  vascularity  of  the  first, 
and  to  note  that  the  blood  of  the  pulmonary  artery  passes  almost  entirely  into 
the  posterior  aorta  by  the  arterial  canal  (or  ductus  arteriosus). 


Differential  Characteks  in  the  Lungs  of  THii  other  Animals. 

The  form  of  tlie  luugs  of  Ruminants  does  not  diftVr  from  that  of  the  Horse,  except  that 
tie  left  is  divided  into  two  lobes,  and  the  right  into  four — the  anterior  of  tiiese  being  curved 
in  front  of  tlie  heart.     This  is  shown  in  Fig.  332. 

The  lungs  of  the  Ox,  Sheep,  and  Goat  are  remarkable  for  the  distinctness  with  which 
the  lobules  are  deiined.  They  are,  in  fact,  separated  by  loose  connective  tissue,  which,  by  a 
certain  degree  of  traction,  may  extend  1  or  2  millimetres ;  it  forms  a  reticular  and  alveolar 
system  capable  of  being  developed  by  insufflati<m.  Kenant  and  Pierret  have  shown  that  the 
dilatable  tracts  are  lymph  spaces,  lined  with  a  characteristically  festooned  epithelium ;  so  that 
the  pulmonary  lobules  in  the  lung  of  the  Ox  aie  batheii  in  a  lymphatic  sac. 

As  a  consequence  of  inflammation,  tliese  spaces,  are  gorged  with  fibrine  and  leucocytes,  and 
contrnst  strikingly,  by  their  pale  tint,  with  the  lobules  ;  therefore  the  lesions  of  pneumonia  in 
the  larger  Ruminants  have  an  altogether  special  character — a  fact  to  which  Dietrichs  drew 
attention  a  long  time  ago. 

In  the  Pig,  the  lungs  comport  themselves  somewhat  like  those  of  Ruminants. 

In  the  Dog  and  Cat,  there  is  no  well-marked  fissure  in  either  lung  towards  tlie  heart, 
which  causes  that  organ  to  be  almost  completely  enveloped  by  pulmonary  tissue.  Tlie  left 
lung  has  three  lobes,  and  the  right  four,  separated  from  one  another  by  deep  furrows,  which 
are  generally  prolonged  to  the  root.  The  lobules  are  small,  very  close,  and  the  pulmonary 
tissue  is  exceedingly  compact.  (The  pulmonary  infundibula  are  proportionately  larger  than  iu 
Ruminants.) 

Comparison  of  the  Larynx,  Trachea,  and  Lungs  of  Man  with  those  of  Animals. 

1.  Larynx. — The  human  larynx  is  proportionately  shorter  and  wider  than  that  of  animals. 
The  principal  cartilages  are  those  which  have  been  already  studied ;  but  there  are,  besides, 
small  cartilaginous  bodies,  to  which  special  names  have  been  given  :  these  are  the  cartilages  of 
Santorini  and  of  Wrisberg.  The  facets  on  the  cricoid  for  articulation  with  the  thyroid  are 
placed  on  the  small  cornu  detached  from  the  external  face  of  the  cartilage.  The  thyroid  is 
wide,  and  protects  the  anterior  face  of  the  larynx  ;  the  angle  formed  by  the  alse,  which  is  more 
marked  in  the  male  than  the  female,  is  very  prominent,  and  is  named  the  pomum  Adami. 
The  epiglottis  is  short,  broad  in  its  middle,  and  rounded  at  its  summit,  something  like  that  of 
the  Carnivora.  The  muscles  are  the  same  in  number  and  disposition  as  in  these  animals;  but 
there  is  distinguished  an  oblique  arytsenoideus — a  fasciculus  of  the  arytsenoid,  wliich  crosses  its 
f«  How  to  form  an  X  in  passing  from  the  upper  border  of  one  arytsenoid  cartilage  to  the  lower 
border  of  tlie  other. 

Internally,  the  human  larynx  has  no  sub-epiglottic  or  sub-arytsenoid  sinus  like  thnt  of  Soli- 
peds,  though  it  hiis  lateral,  or  Morgagni's,  ventricles  that  ascend  a  little  to  the  outside  of  tlie 
superior  vocal  cords. 

2.  Trachea.  3.  Bronchi.— There  is  little  difference  to  be  remarked  in  these.  Tiie  trachea 
is  about  four  inches  long  and  about  one  inch  wide,  and  is  composed  of  about  twenty  C-shaped 
rings,  which  are  closely  united  as  in  animals.  It  is  situated  iu  thi^  median  plane,  in  the  upper 
part  of  the  neck,  where  it  is  embraced  by  the  lobes  of  tlie  thyroid  gland ;  at  its  entrance  into 
the  chest  it  deviates  slightly  to  the  right.     The  two  short  canals  between  its  lower  extremity 


GLANDIFORM  BODIES  CONNECTED  WITH  RESPIRATORY  APPARATUS.    553 

and  the  lungs  are  the  bronchi;  the  right  bronchus  is  the  shortest  and  wiriest,  and  has  an  almost 
horizontal  direction,  entering  the  right  lung  at  the  fourth  dorsal  vertebra ;  the  left  is  longer 
and  less  voluminous,  and  reaches  the  corresponding  lung  at  the  tifth  vertebra. 

4.  Lungs.— The  lungs  weigh  about  forty  ounces.  As  in  all  animals,  the  right  is  more 
voluminous  than  the  left,  and  is  divided  into  three  lobes ;  the  latter  has  only  two.  The 
inferior  vena  cava  is  not  surrounded  by  pulmonary  tissue  :  the  principal  lobes  are  partitioned 
into  lobules,  which  are  visible  on  the  surface,  and  on  the  limits  of  which  are  deposited,  only  in 


Fig.  333. 


LUNG    OF    THE    SHEEP    (INFERIOR    VIEW). 

1,  Right  lung;  2,  left  luDg;  3,  trachea; 
4,  heart ;  5,  carotid  arteries ;  (5,  posterior 
vena  cava. 


HUMAN  LUNGS  AND  HEART  (FRONT  VlEW). 

Right  ventricle;  2,  left  ventricle;  3,  right  auricle; 
4,  left  auricle ;  5,  pulmonary  artery ;  6,  right  pul- 
monary artery;  7,  left  pulmonary  nrtery  ;  8,  liga- 
ment of  ductus  arteriosus;  9,  arch  of  aorta;  10, 
superior  vena  cava  ;  11,  arteria  innominata ;  12,  right 
subclavian  vein,  with  the  artery  behind  it ;  13,  right 
common  carotid  artery  and  vein;  14,  left  vena  in- 
nominata; 15,  left  carotid  artery  and  vein;  16,  left 
subclavian  vein  and  artery;  17,  trachea;  18,  right 
bronchus ;  19,  left  bronchus ;  20,  20,  pulmonary 
veins;  21,  superior  lobe  of  right  lung;  22,  middle 
lobe  ;  23,  inferior  lobe  ;  24,  superior  lobe  of  left  lung ; 
25,  inferior  lobe. 


the  adult,  a  notable  quantity  of  pigmentary  matter,  that  gives  the  lungs  the  appearance  of  a 
chess-board.     There  is  nothing  to  be  said  respecting  their  intemul  conformation  and  structure. 


The  Glandiform  Bodies  connected  with  the  Respiratory 
Apparatus. 

1.  Thyroid  Body,  or  Gland  (Fig.  334). 


The  thyroid  body  consists  of  two  oval  lobes  of  a  reddish-brown  colour, 
and  is  situated  close  to,  and  behind,  the  larynx,  beside  the  two  first  rings  of  the 
trachea. 

These  two  lobes,  distinguished  as  right  and  left,  appear  at  first  sight  to  be 
perfectly  independent  ;  but  close  examination  shows  them  to  be  united  by  an 
intermediate  portion  (the  isthmus),  which  passes  across  the  anterior  face  of  the 


554 


BESPIRATORY  APPARATUS  IN  MAMMALIA. 


GROUP   OF  GLAND  VESICLES   FROM   THE  THYROID 
BODY   OF    A   YOUNG  SUBJECT. 

a,  Connective  tissue ;  6,  basement  membrane  of 
the  vesicles  ;  c,  epithelial  cells. 


trachea.     This  connecting  portion  is  far  from  being  constant  in  the  Horse, 
while  it  is  nearly  always  present  in  the  Ass. 

Each  lobe  of  the  thyroid  body  is  related,  inwardly,  to  the  trachea  ;  outwardly, 
it  is  covered  by  the  subscapulo-hyoideus  muscle. 

Structuee.— The  thyi-oid  body  is 
Fig.  334.  composed  of  a  fibrous  envelope,  and  a 

proper  tissue  or  parenchyma. 

The  fihrous  envelope  is  composed  of 
slender,  but  strong  connective  tissue  ; 
it  sends  from  its  inner  face  a  large 
number  of  thin  nucleated  layers  that 
intersect  each  other,  forming  spaces  in 
which  the  proper  tissue  is  contained. 

The  parenchyma  is  divided  into 
lobules,  the  presence  of  which  is  mani- 
fested on  the  surface  of  the  organ. 
They  are  composed  of  vesicles  communi- 
cating with  each  other,  the  shape  and 
contents  of  which  vary  considerably 
with  age  and  situation.  In  the  foetus, 
or  very  young  animal,  they  are  round 
or  elliptical,  and  constituted  by  a  thin 
amorphous  membrane,  lined  by  poly- 
gonal cells  with  a  large  nucleus,  and 
containing  a  granular  fluid.  In  the 
adult,  these  vesicles  are  misshapen,  and,  after  being  distended,  several  run  to- 
gether, while  the  epithelium  is  less  evident,  but  uniform ;  the  contents  have 
become  brown,  and  hold  granules  and  nuclei  in  suspension  ;  and,  finally,  they 
often  assume  the  character  of  colloid  matter,  in  becoming  viscid  and  of  a  yellow 
tint. 

Vessels  and  nerves. — The  thyroid  body  is  remarkable  for  the  relatively 
enormous  volume  of  its  blood-vessels  ;  the  arteries  chiefly  come  from  the  thyro- 
laryngeal  branch — a  collateral  of  the  common  carotid  (they  form  plexuses  on  the 
vesicle  walls)  -,  the  rei7is  pass  to  the  jugular.  Its  nervous  filaments  are  from  the 
first  and  second  cervical  pairs,  with  twigs  from  the  sympathetic.  It  has  an 
abundance  of  li/mphatics,  which  form  a  system  of  somewhat  large  cavities  around 
the  alveoli. 

Functions. — The  thyroid  body  is  one  of  the  organs  classed,  in  a  somewhat 
arbitrary  manner,  in  the  ill-defined  category  of  ductless  glands.  Our  knowledge 
of  its  use  is  as  uncertain  at  present  as  in  the  infancy  of  anatomical  science. 
So  that  we  can  say  nothing  more  on  this  subject,  except  that  the  successive 
or  simultaneous  excision  of  the  two  lobes  in  the  Horse  do  not  appear  to  cause 
any  derangement  in  the  animal's  health. 

In  those  animals  in  which  it  is  developed,  it  seems  to  have  much  importance, 
and  is  said  to  play  a  part  with  regard  to  the  brain,  similar  to  that  attributed  to 
the  spleen  in  the  abdominal  circulation.  Ha^mato-poietic  functions  have  also 
been  ascribed  to  it,  from  the  influence  it  exerts  by  means  of  the  follicles  placed 
between  its  vesicular  lobes  ;  these  are  supposed  to  destroy  the  mucme  formed  in 
the  body. 

The  study  of  its  development  does  not  throw  any  light  on  its  functions. 


GLANDIFORM  BODIES  CONNECTED    WITH  RESPIRATORY  APPARATUS.    555 

It  is  certainly  relatively  larger  in  the  foetus  and  young  animals  than  in  adults  ; 
but  the  difference  is  not  sufficiently  marked  to  authorize  us  in  drawing  any 
physiological  inductions  therefrom. 

2.  Thymus  Gland  (Figs.  335,  336). 

The  thymus  gland  is  a  transitory  organ,  being  only  present  in  the  foetus  and 
very  young  animals,  and  in  its  nature  closely  resembles  the  thyroid  gland.  Like  it, 
it  is  divided  into  two  lateral  lobes,  placed  close  together  in  the  middle  line,  under 


Fig.  336. 


Fig.  335. 


PORTION  OF    THYMUS    GLAND 
OF   CALF,   UNFOLDED. 

a,  Main  canal ;  h,  glandular 
lobules ;  c,  isolated  gland 
granules  seated  on  the  main 
canal. 


COURSE   AND   TERMINATION   OF   THE   ABSORBENT   DUCTS   OF 
THE   THYMUS   GLAND   OF    A   CALF. 

1,  Internal  jugular  veins ;  2,  superior  vena  cava  ;  3,  thoracic 
duct,  dividing  into  two  branches,  that  again  unite  before 
terminating  in  the  root  of  the  left  jugular  vein;  4,  the  two 
thymic  ducts  :  that  on  the  left  side  opening  into  the  thoracic 
duct,  and  the  right  into  the  root  of  the  corresponding  jugular 


the  lower  face  of  the  trachea,  partly  without  and  partly  within  the  chest,  between 
the  two  layers  of  the  anterior  mediastinum.  It  is  elongated  from  before  to 
behind,  of  a  whitish'  colour,  and  uneven  or  lobulated  on  its  surface  like  a  salivary 
gland. 

Structure. — It  owes  its  uneven  aspect  to  its  lobular  structure  ;  for  it  is 
effectively  reduced  by  dissection  into  a  multitude  of  granular  lobules,  in  the 
centre  of  which  are  found  vesicular  cavities  containing  a  lactescent  fluid.  The 
vesicles  are  larger  than  those  of  the  thyroid  gland,  and  have  for  walls  a  very 


556  MESFIRATOtiJt   APPARATUS  IN  MAMMALIA. 

thin  layer  of  delicate  connective  tissue  ;  they  are  filled  by  a  mass  of  nuclei. 
A  wide,  irregular  cavity  has  been  described  as  existing  in  the  middle  of  each  lobe 
{j-eservoir  of  the  thymus),  and  evidently  communicating  with  the  vesicles  of  the 
lobules,  as  it  contains  a  notable  quantity  of  the  same  milky  fluid.  This  cavity  is 
certainly  not  present  at  all  periods  ;  for  I  have  not  met  with  it  in  two  young 
foetuses  now  lying  before  me  as  I  write.  But  without  dwelling  on  this  particular 
point,  we  may  notice  enormous  blood-vessels,  lymphatics,  and  nerves,  as  com- 
plementary elements  in  the  organization  of  the  gland,  the  structure  of  which  is 
very  similar  to  that  of  true  glands,  though  differing  from  them  in  an  important 
feature — the  absence  of  an  excretory  duct. 

Nothing  positive  is  known  as  to  the  functions  of  the  thymus  gland  ;  it  is 
only  certain  that  they  resemble  those  of  the  lymphatic  glands,  and  that  they  are 
exclusively  related  to  the  development  of  the  young  animal ;  as  it  generally 
disappears  some  months  after  birth,  though  it  is  sometimes  found  in  the  adult, 
and  even  in  very  aged  animals. 

(Its  functions  are  supposed  to  be  the  same  as,  or  analogous  to,  those  of  the 
thyroid.  Structurally,  the  organ  may  be  said  to  consist  of  an  assemblage  of 
hollow  glandular  lobules  joined  together  by  connective  tissue,  each  having  a 
cavity  which  opens  into  a  central  canal  that  has  no  duct,  and  being  hned 
externally  by  an  almost  amorphous  membrane  which  divides  it  into  "acini," 
or  gland-granules.  Separate  acini  are  often  observed  on  the  main  canal.  Each 
lobule  is  made  up  of  its  greyish-white,  soft  parenchyma  composed  of  free  nuclei 
and  small  cells,  and  has  a  minutely  distributed  capillary  plexus.  The  lymphatics 
terminate  in  two  large  ducts  that  commence  at  the  upper  extremities  of  the  lobes 
of  the  gland — the  thymic  ducts — and  pass  downward  to  terminate  at  the  junction 
of  the  jugular  and  axillary  veins  at  each  side.) 

Differential  Characters  in  the  Glandiform  Bodies  annexed  to  the  Kespiratort 
Apparatus  in  the  other  Animals. 

The  thyroid  body,  peculiar  to  Mammals,  is  more  developed  in  Ruminants,  Pacyderms, 
and  Carnivora,  than  in  Solipeds.  The  two  lobes  are  closer  together,  and  are  often  united  by 
the  thyroid  isthmus.  In  the  Pig  this  i^  very  marked,  and  the  gland  well  merits  its  name, 
as  it  forms  a  veritable  shield  in  front  of  the  trachea,  towards  the  lower  part  of  the  neck. 

The  thymus  gland  in  young  Ruminants  is  more  voluminous  than  in  tlie  Foal,  and  is  situated 
higher  up  in  the  cervical  region.'  (In  the  Carnivora,  it  is  divided  into  two  brandies  ;  but  it  is 
small,  and  completely  lodged  between  the  layers  of  the  anterior  mediastinum.  It  persists  for 
some  time  after  birth,  and  seldom  disappears  in  less  than  a  year.) 

(Comparison   of  the  Glandiform    Bodies  annexed  to  the  Respiratory    Apparatus  in 
Man,  with  those  of  Animals. 

In  Man,  the  two  lobes  of  the  thyroid  body  are  connected  by  an  istlimus,  and  the  upper 
extremity  of  the  lobe  is  carried  up  to  the  side  of  the  thyroid  cartilage.  Tiie  istlimus  often  gives 
origin  to  a  process  of  variable  length  and  size,  called  the  pyramid,  or  third  lobe,  which  is 
generally  situated  to  the  left.  A  muscle  is  sometimes  found  connected  with  the  isthmus  or 
pyramid,  and  is  attached  above  to  tlie  body  of  theos  hyoidesor  to  the  thyroid  cartilage  ;  it  has 
been  named  the  levator  glandulas  thyroidx. 

The  thymus  gland  is  composed  of  two  lobes,  a  right  and  left,  only  joined  by  connective  tissue, 
and  having  no  structural  communication.  There  is  a  cervical  and  a  thoracic  portion,  the  whole 
extending  from  the  fourth  rib  as  higli  as  the  thyroid  gland.  After  birth  it  continues  to  enlarge 
until  the  end  of  the  second  year,  and  begins  to  diminish  between  the  eighth  and  twelfth 
years.) 


THE  RESPIRATORY  APPARATUS  IN  BIRDS.  557 

CHAPTEE  II. 

The  Respiratory  Apparatus  in  Birds. 

The  organs  composing-  the  respiratory  apparatus  of  Birds  offer  conditions  alto- 
gether special,  which  have  a  remarkable  influence  on  the  mechanism  of  respira- 
tion. The  modifications  in  the  performance  of  this  function  will  be  indicated 
after  an  examination  of  the  tubular  apparatus  which  carries  air  into  the  Iwiff, 
and  the  characters  of  that  organ,  as  well  as  the  air-reservoirs  (or  sacs)  annexed 
to  it. 

The  Tubular  Apparatus  which  carries  Air  to  the  Lungs.— When 
this  apparatus  is  compared  with  that  of  Mammals,  no  very  sensible  differences  are 
observed— at  least,  in  domesticated  Birds. 

The  nostrils,  pierced  through  the  upper  mandible  of  the  beak,  have  no  mem- 
branous and  movable  alse,  and  the  nasal  fossae  open  into  the  pharynx  by  a  long, 
narrow  slit  behind  the  bony  palate.  A  transverse  row  of  small,  horny  papillae, 
placed  at  the  anterior  extremity  of  this  aperture,  represents  the  soft  palate. 

The  larynx  has  no  epiglottis  :  a  defect  which  does  not  prevent  the  complete 
occlusion  of  the  glottis  during  the  passage  of  food,  as  the  laryngeal  orifice  is 
circumscribed  by  two  lateral  lips,  which  then  meet  in  the  most  exact  manner. 

The  trachea  is  composed  of  complete  cartilaginous  rings,  and  not  simple  arcs. 
In  Song-birds,  the  last  ring  is  a  second  larynx,  the  real  organ  which  produces  the 
modulated  voice  of  these  creatures  ;  it  only  exists  in  a  rudimentary  condition  in 
Poultry,  however,  the  last  tracheal  piece  in  them  being  slightly  dilated,  and 
showing  at  the  origin  of  the  bronchi  a  membranous  layer,  from  whose  vibration 
results  cries  or  crowing.  Other  singular  peculiarities  belonging  to  the  trachea 
deserve  to  be  described  here,  if  they  were  not  the  exclusive  appanage  of  some  wild 
fowl.  "We  are  content  to  mention  the  presence  of  the  bony  drum  found  at  the 
terminal  extremity  of  the  trachea  in  the  whistling  Duck,  and  the  remarkable  con- 
volutions that  tube  forms  in  the  breast-bone  of  Cranes  and  male  Swans. 

The  hrofichi  only  show  incomplete  rings  in  their  structure.  They  pass  into 
the  lung  by  its  inferior  face,  towards  the  union  of  its  anterior  and  two  posterior 
thirds.  When  describing  this  organ,  their  mode  of  ramification,  and  the  nature 
of  the  relations  they  bear  to  its  proper  tissue,  will  be  considered. 

The  Lungs. — Sappey,  in  the  remarkable  memoir  published  by  him  in 
1847,^  has  described  them  as  follows  :  "  The  lungs  of  Birds  are  situated  on  the 
lateral  parts  of  the  vertebrse  of  the  back — which  separate  them,  and  lying 
against  the  arch  of  the  thoracic  cavity,  to  which  they  adhere.  Their  rosy  colour 
resembles  that  presented  by  these  organs  in  Man  and  the  Mammalia  during 
uterine  life,  and  for  some  time  after  birth  ;  they  are  especially  remarkable  for 
their  restricted  volume,  which  scarcely  represents  an  eighth  part  of  the  thoracic 
capacity.  Their  configuration  is  far  removed  from  the  conical  form  of  the  lungs 
in  Mammals,  and  the  oval  form  of  the  same  organs  in  reptiles  ;  they  are  semi- 
elhptical,  and  if  the  two  lungs  of  a  Mammal  were  opposed  base  to  base,  their 
hkeness  would  be  produced  :  to  obtain  the  same  results  with  the  limgs  of  a 
reptile,  it  is  necessary  to  divide  them  in  the  direction  of  their  great  axis. 

"  This  shape  enables  us  to  distinguish  in  the  lungs  of  a  bird,  two  faces — a 
'  Sappey,  Becherches  sur  I'Appareil  Respiratoire  des  Oiseaux.     Paris  :  1857 
38 


558  THE  RESPIRATORY  APPARATUS  IN  BIRDS. 

convex  and  concave  ;  two  harder s — an  external  Hand  an  internal  ;  and  tivo 
extremities — an  anterior  and  posterior. 

"  The  convex  face,  also  named  the  dorsal,  costal,  or  superior  face,  corresponds 
inwardly  to  the  dorsal  vertebras,  and  outwardly  to  the  ribs  and  the  intercostal 
muscles  ;  it  is  exactly  moulded  on  the  walls  of  the  thorax,  and  as  the  ribs  pro- 
trude on  the  internal  face  of  these  walls,  it  results  that  this  surface  of  the  lungs 
is  marked  by  transverse  furrows  which  give  it  a  lobulated  aspect ;  but  these  lobes 
or  lobules  show  nothing  common  with  those  composing  the  same  organ  in 
Mammalia.  In  that  class,  the  existence  of  lobes  and  lobules  is  an  established 
fact,  and  is  caused  by  the  dichotomous  division  of  the  bronchi ;  in  birds,  it  is 
only  apparent,  and  depends  on  the  diminished  thickness  of  the  lung  at  each  rib. 
This  face,  quite  imperforate,  is  covered  by  a  thin  layer  of  cellular  tissue,  which 
unites  it  to  the  sides  of  the  thorax. 

"  The  plane  or  concave  face  looks  downwards  ;  it  is  in  relation  with  the 
diaphragm,  which  separates  it  from  the  viscera  of  the  thorax,  and  from  the 
abdomen  ;  from  this  arises  its  other  names  of  inferior,  diaphragmatic,  or  visceral 
face.  Like  the  preceding,  it  is  covered  by  a  very  fine  layer  of  cellular  tissue, 
which  forms  adhesions  with  the  diaphragm  ;  but  it  differs  from  it  by  the  orifices 
it  presents,  which  are  five  in  number,  and  constitute  veritable  canals,  through 
which  the  air  passes  and  repasses  incessantly  to  and  from  the  sacs,  and  from  them 
to  the  lungs. 

"  The  herders  are  parallel  to  the  axis  of  the  body  ;  the  internal  is  rectilinear, 
thick,  and  rounded  ;  the  external,  convex,  thin,  and  sharp. 

"  Of  the  two  extremities,  the  anterior,  which  is  very  acute,  occupies  the 
receding  angle  formed  by  the  spine  within  the  first  rib  without ;  the  posterior, 
more  considerable,  has  a  rounded  form." 

In  regard  to  structure,  that  which  distinguishes  the  lung  of  Birds  from  that 
of  Mammals,  is  the  mode  of  distribution  and  termination  of  the  air-passages.  In 
Mammals,  the  large  bronchial  tubes,  placed  in  the  centre  of  the  lung,  send  their 
divisions  towards  the  surface  of  the  organ,  or  in  a  centrifugal  manner  ;  in  birds 
they  are  disposed  at  the  periphery  of  the  lung,  and  direct  their  different  ramifi- 
cations towards  the  centre,  or  in  a  centripetal  fashion.  On  the  other  hand,  the 
arboreal  division  of  the  bronchi  in  Mammals  is  replaced  in  birds  by  penniform 
ramification.  liastly,  the  terminal  bronchial  tubes  instead  of  opening  into  a 
series  of  closed  vesicles,  as  in  Mammals,  anastomose  with  one  another  in  birds, 
so  as  to  form  an  inextricable  aerial  network. 

Sappey  has  further  developed  the  knowledge  acquired  on  this  interesting 
subject  in  the  following  terms  :  "  Arrived  in  the  puknonary  tissue,  it  (the 
bronchial  trunk)  dilates,  divides,  gradually  contracts  in  following  its  primary 
direction,  and  in  this  way  gains  the  posterior  extremity  of  the  organ,  where  it 
terminates  by  opening  into  the  abdominal  reservoir. 

"  This  ferifying  trunk,  therefore,  presents  two  very  distinct  portions,  the  one 
extra-pulmonary,  the  other  intra-pulmonary.  The  first  offers  the  greatest  analogy 
to  the  bronchi  of  Mammalia  ;  it  is  membranous  internally,  elastic  and  fibrous 
elsewhere,  provided  outwardly  with  cartilaginous  rings,  which  embrace  three- 
fourths  of  its  circumference,  and  is  lined  by  mucous  membrane  characterized  by 
its  pale  rose-colour,  and  its  marked  adherence. 

"  The  second  differs  from  the  preceding  in  its  dimensions,  form,  and  struc- 
ture. Owing  to  its  dilatation  at  its  entrance  to  the  lung,  its  dimensions  are  more 
considerable,  and  may  be  stated  as  three  to  two  of  the  extra-pulmonary  portion. 


THE  RESPIRATORY  APPARATUS  IN  BIRDS.  559 

Beyond  this  enlargement,  it  diminishes  in  capacity  by  the  emission  of  branches, 
losing  its  cylindrical  form  to  assume  that  of  a  cone  with  a  trmicated  summit. 
Its  walls  are  almost  entirely  destitute  of  cartilaginous  rings,  so  that  the  origin  of 
the  principal  conduits  is  constantly  membranous. 

"  The  air-passages  arising  from  this  common  trunk  to  constitute  the  frame- 
work of  the  lung,  are  remarkable  for  their  uniformity  in  number,  form,  and  the 
direction  they  olTer  in  all  classes  of  birds.  They  are  generally  twelve,  and  their 
origin  is  thus  distributed  :  four  arise  from  the  internal  wall  of  the  trunk  by  a 
series  of  orifices  placed  one  after  the  other  ;  seven  are  detached  from  its  external 
wall  by  a  second  series  of  orifices  also  disposed  in  rows  ;  the  twelfth  springs  from 
its  inferior  wall,  and  immediately  bends  downwards  and  outwards  to  open  into 
the  posterior  diaphragmatic  reservoir,  which  may  be  considered  as  a  terminal 
branch  of  the  principal  trunk. 

"  All  the  canals  which  have  their  origin  from  these  linear  series  of  openings 
on  the  internal  and  external  walls  of  the  generating  trunk,  show  this  common 
disposition  :  that  from  their  commencement  they  pass  towards  the  periphery  of 
the  lung,  that  they  divide  and  subdivide  at  this  periphery,  that  they  cover  it 
with  their  ramifications,  and  do  not  leave  it  to  enter  the  pulmonary  parenchyma 
until  their  volume  has  been  considerably  reduced. 

"  The  conduits  leaving  the  orifices  situated  on  the  inner  wall  of  the  a3rial 
trunk  ramify  on  the  inferior  face  of  the  lung  ;  those  proceeding  from  the  eche- 
loned orifices  on  the  outer  wall  are  distributed  on  the  opposite  face.  The  first 
constitute  the  diaphragmatic,  and  the  second  the  costal  bronchial  tubes. 

"  The  diaphragmatic  hroiichial  tubes,  four  in  number,  like  the  orifices  from 
which  they  originate,  may  be  distinguished  by  the  numerical  names  of  first, 
second,  third,  and  fourth,  in  proceeding  from  before  to  behind  ;  the  first  bronchus 
is  carried  forward  horizontally,  the  second  transversely  inwards,  the  third 
obliquely  inwards  and  backwards,  and  the  fourth  directly  backwards.  In  view 
of  their  divergent  direction,  which  resembles  a  fan,  they  might  be  designated  as 
the  anterior,  internal,  and  posterior  diaphragmatic  bronchial  tubes  ;  and  to  dis- 
tinguish the  last  two,  the  more  voluminous  one — which  is  directed  backwards  and 
inwards — might  be  named  the  great  posterior  diaphragmatic  bronchus,  and  the 
one  passing  directly  backwards,  the  small  posterior  diaphragmatic  bronchus. 

"  The  costal  bronchial  tubes,  seven  in  number,  may  be  also  designated  as  first, 
second,  third,  etc.,  in  proceeding  from  before  to  behind.  Parallel  at  their  origin, 
and  in  juxtaposition,  like  the  pipes  of  an  organ,  they  separate  after  following  a 
certain  course,  and  affect,  by  their  divergence,  the  fan-shape  already  observed  in 
the  disposition  of  the  diaphragmatic  bronchi.  Like  the  latter,  they  become 
peripheral  from  their  origin,  and  spread  out  from  centre  to  circmnference.  The 
first  is  carried  very  obliquely  upwards  and  inwards,  to  attain  the  anterior 
extremity  of  the  lung  ;  all  the  branches  it  furnishes  arise  from  its  anterior  wall, 
and  those  which  are  nearest  its  origin  are  inflected  to  gain  the  external  border 
of  the  organ.  The  succeeding  tubes  are  directed  forwards,  the  others  forwards 
and  inwards  ;  while  all  proceed  to  meet  those  coming  from  the  anterior  dia- 
phragmatic bronchus,  though  they  do  not  anastomose  with  them.  Coming  in 
contact,  they  plunge  into  the  pulmonary  tissue  in  such  a  way,  that,  when  a  lung  is 
inflated,  we  observe  between  these  two  orders  of  ramifications  a  very  manifest 
groove,  which  is  perfectly  distinct  from  those  due  to  the  protrusion  of  the  ribs  ; 
this  groove  evidently  represents,  though  in  a  rudimentary  state,  the  inter- 
lobular fissures  in  the  lungs  of  quadrupeds. 


560  THE  RESPIRATORY  APPARATUS  IN  BIRDS. 

"  The  second,  third,  and  fourth  costal  bronchi  follow  a  transverse  course, 
and  ramify  on  the  inner  border  of  the  lung  ;  the  fifth  and  sixth  incline  towards 
the  posterior  extremity  of  the  organ  ;  the  seventh,  very  small,  reaches  this 
extremity  and  disappears. 

"  The  first  costal  bronchus  is  the  most  voluminous  ;  those  succeeding  it 
gradually  diminish  in  calibre.  At  their  point  of  emergence  they  adhere  closely 
to  the  ribs  ;  all  are  imperforate,  and  this  feature  essentially  distinguishes  them 
from  those  occupying  the  opposite  face. 

"  The  canalicuU  furnished  by  these  principal  tubes  do  not  sensibly  differ  in 
calibre  in  the  various  bronchi  ;  all  offer  an  equal  diameter,  and  their  dimensions 
are  only  in  relation  to  the  total  volume  of  the  lung.  All  are  detached  at  a  right 
angle  from  the  pulmonary  wall  of  each  bronchus,  and  descend  perpendicularly  into 
the  lung  ;  and  all,  from  their  origin  to  their  termination,  preserve  the  same 
diameter,  and  consequently  the  same  cylindrical  form.  If  this  mode  of  ramifica- 
tion be  compared  with  that  observed  in  Mammals,  it  will  be  seen  to  differ  con- 
siderably. In  the  latter  class,  the  air-passages  affect  the  dichotomous  division 
proper  to  the  arteries  and  veins,  the  result  of  which  is  a  series  of  arborescent  canals 
decreasing  in  capacity.  In  birds  only  two  kinds  of  conduits  are  observed,  the 
primitive  and  peripheral,  disposed  around  a  generating  axis  like  the  barbs  of  a 
feather  on  their  stalk  ;  and  the  secondary  and  parenchymatous,  implanted  on  the 
pulmonary  walls  of  the  first,  like  the  hairs  of  a  brush  on  their  common  base. 
These  two  arrangements  are  evidently  similar,  except  that  the  peripheral  canals, 
which  are  few,  only  form  a  single  row  on  each  side  ;  while  the  canaliculi,  very 
numerous,  form  several.  Consequently,  it  may  be  said  that  the  mode  of  ramifica- 
tion proper  to  Mammaha  is  essentially  dichotomous,  and  that  observed  in  birds 
essentially  penniform. 

"  Independently  of  the  canaliculi  arising  from  the  pulmonary  walls  of  the 
diaphragmatic  and  costal  bronchi,  there  are  others  which  spring  directly  from  the 
generative  trunk  ;  but  in  their  dimensions,  direction,  form,  and  general  disposi- 
tion, they  do  not  differ  from  the  preceding. 

"  How  do  these  canals  terminate  ?  Notwithstanding  the  importance  of  this 
question,  it  has  been  generally  neglected  ;  though  its  solution  alone  may  furnish 
the  analogies  and  differences  necessary  for  the  parallel  which  has  always  been 
attempted  to  be  established  between  the  lungs  of  birds  and  those  of  other  verte- 
brates. Our  special  researches  on  this  point  have  led  us  to  the  conclusion  that 
all  the  canaliculi  open  into  one  another,  and  by  this  anastomosis  constitute  an 
extricable  plexus  the  various  parts  of  which  communicate  with  each  other." 

Finally,  it  may  be  mentioned  that  "  the  walls  of  the  pulmonary  canaliculi 
examined  microscopically,  appear  to  be  covered  internally  with  irregular  septa 
which  circumscribe  the  areolae,  and  give  them  a  cellular  aspect." 

The  Aie-sacs.^ — "  In  birds,  the  pulmonary  mucous  membrane  is  continued, 
at  the  level  of  the  orifices  in  the  lung,  into  the  utriculiform  cavities  which  are 
developed  between  the  walls  of  the  thorax  and  the  abdomen  on  the  one  side,  and 
the  thoracic  and  abdominal  viscera  on  the  other.  These  air-reservoirs  exist  in 
all  the  vertebrata  of  the  second  class.  In  all,  they  are  situated  at  the  periphery 
of  the  viscera  in  the  trunk,  in  such  a  manner  that  Cams  has  justly  observed  that 
the  lungs  of  Birds  enclose  all  the  other  viscera  ;  so  that  when  they  are  distended 
by  the  entrance  of  air,  they  generally  depress  these  viscera  by  pushing  them 

'  What  is  said  relating  to  these  air-sacs  is  taken  from  the  Memoir  of  M.  Sappey,  Recherchet 
sur  I'Appareil  Respiratoire  des  Oiseaux.     Paris :  1847. 


THE  RESPIRATORY  APPARATUS   IN  BIRDS.  561 

towards  the  median  plane.  In  all,  they  are  independent  of  each  other,  and 
freely  communicate  either  with  the  Imig  by  a  single  aperture,  or  with  the  bones 
by  one  or  more  openings.     Lastly,  in  all  they  are  nine  in  number. 

"  These  reservoirs  are  :  the  thoracic  sac,  situated  at  the  anterior  part  of  the 
thorax  ;  two  cervical  reservoirs,  situated  at  the  base  of  the  neck  ;  two  anterior 
diaphragmatic  reservoirs,  placed  between  the  two  diaphragms ;  two  posterior 
diaphragmatic  reservoirs,  also  between  these  two  diaphragms,  but  behind  the 
preceding  ;  and,  lastly,  ttvo  abdominal  reservoirs,  placed  against  the  superior  wall 
of  the  abdomen.  Of  these  nine  reservoii-s,  the  first  only  is  single  and  symmetrical ; 
the  others  are  pairs,  and  similarly  arranged  on  each  side  of  the  median  plane. 

"  The  thoracic  and  cervical  reservoirs  are  situated  beneath,  and  in  front  of, 
the  lungs ;  the  abdominal  reservoirs  lie  behind  these  organs,  and  the  four 
diaphragmatic  sacs  at  their  inferior  part  and  between  the  preceding  ;  hence  the 
denomination  of  middle  reservoirs  sometimes  applied  to  the  latter,  in  opposition 
to  the  first,  which  are  named  the  anterior  reservoirs,  and  to  the  second,  called  the 
posterior  reservoirs." 

External  Conformation  of  the  Reservoirs. — 1.  Thoracic  reservoir 
(Fig.  337,  2). — "  It  is  situated  above  the  clavicles  and  the  inter-clavicular  space, 
in  the  cavity  of  the  thorax,  which  it  extends  beyond  on  each  side  to  the  roots  of 
the  wings,  around  the  articulation  of  the  shoulder.  It  is  related  with  :  above, 
the  trachea  and  oesophagus  on  the  middle  plane,  the  lungs  and  the  origin  of  the 
cervical  reservoirs  on  the  lateral  parts  ;  below,  with  the  sternum,  the  clavicles, 
and  the  interclavicular  aponeurosis ;  behind,  with  the  heart  and  anterior 
diaphragmatic  reservoirs,  beneath  which  it  is  prolonged  by  forming  on  each  a 
long  point ;  in  front,  with  the  integuments  of  the  neck,  which  it  raises  into 
a  hemisphere  in  Palmipeds,  but  which  is  angularly  depressed  in  other  classes  ;  on 
the  sides,  with  the  sternal  ribs,  the  two  clavicles,  and  the  membrane  uniting  them. 

"  The  prolongations  which  arise  from  the  lateral  parts  of  these  reservoirs,  and 
cross  the  walls  of  the  thorax  to  pass  around  the  articulation  of  the  shoulder,  are 
three  in  number,  and  may  be  distinguished  into  inferior  or  subpectoral,  superior 
or  subscapular,  and  middle  or  humeral. 

"  The  subpectoral  prolongation  (Fig.  337,  d)  issues  from  the  thoracic  reservoir 
by  an  orifice  situated  behind  the  posterior  clavicle,  and  passes  beneath  the  tendon 
of  the  great  pectoral  muscle,  where  it  spreads  out  as  a  lenticular  cavity.  The 
relations  it  contracts  with  that  muscle  are  remarkable  :  in  Birds,  still  more  than 
in  Man  and  a  great  number  of  quadrupeds,  the  tendon  of  the  great  pectoral  is 
formed  of  two  parts,  one  direct,  the  other  reflected  ;  it  is  between  these  two 
portions  that  this  small  air-sac  is  insinuated,  and  where  it  forms  a  very  firm 
connection  with  them  ;  the  effect  of  which  is,  that  at  the  moment  the  great 
pectoral  muscle  contracts,  it  dilates  the  subjacent  cell  and  draws  into  it  a  greater 
quantity  of  air. 

"  The  subscapular  and  humeral  prolongation  communicate  with  the  principal 
reservoir  by  a  common  opening  placed  behind  the  small  adductor  muscle  of  the 
humerus.  After  leaving  this  orifice,  the  subscapular  sac  spreads  under  the 
scapular  and  subscapular  muscle,  which  it  separates  from  the  ribs  and  corresponding 
intercostal  muscles  ;  it  is  developed  more  particularly  in  a  longitudinal  direction. 

"  The  humeral  prolongation  occupies  the  axilla ;  it  is  smaller  than  the 
preceding,  of  a  pyramidal  form,  and  opens  by  its  summit  into  an  infundibular 
fossa,  which  leads  to  the  canal  of  the  humerus. 

"  The  thoracic  reservoir  differs  from  aU  the  others  by  the  extremely  numerous 


562  RESPIRATORY  APPARATUS  IN  BIRDS. 

membranous  folds  which  partition  its  cavity.  The  membrane  forming  it  being 
continued  on  itself,  every  organ  traversing  the  thorax  becomes  the  cause  of  a  fold 
in  which  it  is  imprisoned  ;  and  as  the  thoracic  cavity  is  traversed  by  the  trachea 
and  the  oesophagus,  the  muscles  which  move  the  inferior  larynx,  and  the  arteries 
and  veins,  it  will  be  understood  how  this  reservoir  should  become  irregular  in 
consequence  of  these  various  partitions,  and  also  why  the  other  serial  sacs  situated 
between  the  viscera  and  the  walls  of  the  thorax,  or  the  simple  contiguous  surfaces, 
should  preserve  their  regular  and  proper  form. 

"The  thoracic  reservoir  communicates  with  the  lungs  by  an  infundibular 
orifice,  situated  on  the  external  side  of  the  embouchure  of  each  bronchus.  This 
orifice  is  dilated  during  inspiration,  by  the  contraction  of  the  two  first  fasciculi  of 
the  pulmonary  diaphragm." 

2.  Cervical  reservoirs  (Fig.  337,  1,  1). — "They  are  situated  above  the 
preceding,  and  the  inferior  part  of  the  neck  and  anterior  part  of  the  lung  ; 
inflated  after  removal  from  the  neighbouring  parts,  they  resemble  two  cones, 
whose  rounded  base  looks  forwards,  and  whose  pediculated  summit  is  directed 
backwards. 

"  Superiorly,  these  reservoirs  lie  against  the  cervical  muscles  ;  inferiorly,  they 
correspond  to  the  air-sac  of  the  thorax,  from  which  they  are  separated  by  the 
trachea,  the  oesophagus,  the  pneumogastric  nerves,  and  the  jugular  veins. 
Inwardly,  they  are  in  juxtaposition,  and  consequently  form  a  median  septum 
which  includes  in  its  substance  the  two  common  carotid  arteries.  Outwardly, 
they  are  related  to  the  origin  of  the  cervical  nerves,  to  each  of  which  they  furnish 
a  small  sheath,  and  with  the  vertebral  artery  which  they  surround,  but  do  not 
contain  in  their  cavity,  as  well  as  with  a  subcutaneous  muscle  and  the  skin.  By 
their  summits,  they  communicate  with  the  anterior  diaphragmatic  bronchus  ;  and 
by  their  base  they  send  out  a  prolongation  which  conducts  the  aii*  into  all  the 
vertebrse  of  the  neck  and  back,  into  all  the  vertebral  ribs,  and,  finally,  into  the 
spinal  canal, 

"  In  their  cervical  portion,  these  prolongations  present  themselves  in  the  f onn 
of  two  canals  extending  from  the  base  of  the  cervical  reservoirs  to  the  base  of  the 
cranium,  where  they  terminate  ;  parallel  and  contiguous  to  the  vertebral  arteries, 
like  them  they  are  lodged  in  the  canals  excavated  in  the  substance  of  the  transverse 
processes. 

"  From  their  external  part  arises,  at  the  six  last  cervical  vertebrae,  as  many 
diverticuli,  which,  lying  against  each  other,  pass  from  each  side  in  the  muscles  of 
the  neck,  surrounded  by  a  common  fibrous  envelope,  and  apparently  form  a  kind 
of  canal  at  the  inferior  part  of  this  region  ;  when,  however,  this  fibrous  membrane 
is  removed,  it  becomes  easy  to  isolate  them,  and  it  is  then  seen  that  they  are 
completely  independent,  and  resemble  small  cornua.  Highly  developed  in 
Palmipeds,  they  are  only  present  in  a  rudimentary  state  in  the  other  classes. 

"  On  the  internal  side  of  these  conduits,  we  see,  at  the  level  of  each  vertebra, 
one  or  more  orifices  by  which  the  air  enters  their  interior ;  and  at  the  niter- 
vertebral  foramina  another  orifice,  which  allows  it  to  pass  into  the  spinal  canal. 
From  the  communication  established  by  these  orifices  between  the  respiratory 
apparatus  and  the  spinal  canal,  it  follows  that  in  Birds  the  cervical  region  is 
traversed  by  three  atmospherical  currents— two  lateral  or  intertransverse,  parallel 
to  the  vertebral  arteries  ;  the  third  median  of  interspinal,  parallel  to  the  spinal  cord. 
"Just  as  the  medullary  tissue  is  replaced  by  air  in  the  bones  of  Birds,  so 
might  it  be  imagined  that  the  sub-arachnoidean  fluid  was  also  replaced  by  air 


THE  RESPIRATORY  APPARATUS  IN  BIRDS.  563 

around  their  spinal  cord ;  and  observation  justifies  the  correctness  of  this 
prevision.  The  dura  mater,  whose  capacity  is  so  superior  to  the  volume  of  the 
marrow  in  Mammals,  exactly  measures  the  volume  of  that  organ  in  Birds  ;  so 
that  there  does  not  exist  between  the  fibrous  and  nervous  surfaces  any  space  for 
an  accumulation  of  liquid  :  this  anatomical  fact  is  sufficient  to  demonstrate  the 
absence  of  sub-arachnoidean  fluid  in  Birds.  In  denying  the  existence  of  this 
fluid,  it  ought  to  be  added  that  in  this  class  of  vertebrata,  as  in  the  preceding, 
the  spinal  prolongation  is  covered  by  a  triple  envelope  ;  that  in  each,  between  the 
pia  mater  and  dura  mater,  is  found  a  thin  transparent  membrane,  which  is 
lubricated  by  a  serous  fluid  ;  but  here  this  fluid  does  not  collect,  it  only  moistens 
the  arachnoid  membrane. 

"Considered  in  their  dorsal  portion,  the  prolongations  springing  from  the 
cervical  reservoirs  offer  an  entirely  different  arrangement  to  that  already  noticed. 
The  interspinal  current,  having  entered  the  thorax,  terminates  by  passing  into 
the  first  dorsal  vertebra  ;  after  coursing  through  every  part  of  this  vertebra,  it 
escapes  by  a  lateral  orifice  into  a  small  sac  situated  between  the  two  first  ribs,  at 
the  origin  of  the  first  dorsal  nerve  ;  from  this  sac,  it  passes  into  the  second 
vertebra  by  an  opening  placed  on  its  antero-lateral  part,  then  it  flows  back  from 
this  into  a  new  air-sac  developed  between  the  second  and  third  ribs  ;  and  passing 
in  the  same  manner  into  the  third  vertebra  to  sweep  through  a  third  intercostal 
sac,  it  arrives  nearer  and  nearer  the  last  dorsal  vertebra.  In  their  dorsal  portion, 
the  prolongations  emanating  from  the  cervical  reservoirs  thus  form  two  currents, 
though  these  are  constituted  alternately  by  the  vertebrse  and  the  small  air-sacs 
placed  on  their  lateral  aspect.  At  the  same  time  that  these  sacs  receive  the  air 
from  the  vertebras  preceding  them,  and  transmit  it  to  those  which  follow,  they 
communicate  it  to  all  the  vertebral  ribs. 

"  In  no  order  of  Birds  do  the  terial  currents  leaving  the  cervical  reservoirs 
communicate  with  those  which  circulate  in  the  cranium.  Liquids  injected  either 
by  the  serial  portion  of  the  vertebral  canal  or  the  lateral  prolongations  of  the 
neck,  never  enter  the  bones  of  that  cavity.  Thinking  that  the  injection  might 
perhaps  penetrate  if  passed  in  the  opposite  direction,  we  have  perforated  the 
bones  of  the  cranium,  and  to  the  aperture  have  adapted  the  extremity  of  a  steel 
syringe  filled  with  mercury  ;  but  the  metal  did  not  reach  the  aerial  prolongations 
of  the  neck.  From  this  double  experiment,  we  concluded  that  the  cranial  bones 
have  no  communication  with  the  respiratory  apparatus." 

3.  Anterior  diapkragmatic  rese^-voirs  (Fig.  337,  3). — "  Placed  between  the 
two  diaphragms,  they  correspond  :  in  front,  to  the  thoracic  reservoirs,  against 
which  they  stand  ;  behind,  to  the  posterior  diaphragmatic  reservoirs  ;  outwardly, 
to  the  ribs  and  intercostal  muscles  ;  inwardly,  to  the  thoraco-abdominal  diaphragm 
and  oesophagus  ;  below,  to  the  most  distant  part  of  the  thoracic  reservoir  ;  above, 
to  the  pulmonary  diaphragm,  which  separates  them  from  the  corresponding 
lung.  These  air-sacs  communicate  with  the  lungs  by  a  circular  opening, 
which  originates  from  the  great  posterior  diaphragmatic  bronchus ;  there  is 
often  a  second  opening  of  communication  beyond  the  embouchure  of  the  trunk  ; 
this  reservoir  is  the  only  one  which  receives  air  from  the  lung  by  a  double 
orifice." 

4.  Posterior  diaphragmatic  reservoirs  (Fig.  337,  4). — "  Oval-shaped  like  the 
preceding,  and  situated  like  them  in  the  interval  which  separates  the  two 
diaphragms,  these  air-sacs  are  in  contact,  by  their  anterior  part,  with  the 
anterior  diaphragmatic  reservoirs,  with  which  they  form  a  vertical  and  trans- 


564 


BESPIBATOEY  APPARATUS  IN  BIRDS. 


Fig.  337. 


verse  septum.      Sometimes  this  septum  is  carried  a  little  more  forward,  and 

then  the  anterior  reservoir  is   smaller ;   this  is  most  frequent   in   Palmipeds. 

At   other  times   it    inclines   backwards,  and  the  anterior  reservoir   is  larger; 

this  arrangement  is  peculiar  to  the 
Gallinacae.  And,  lastly,  tliis  partition 
divides  the  intercepted  space  between 
the  diaphragms  into  two  equal 
cavities :  rapacious  Birds  offer 
numerous  examples  of  this. 

"  Behind,  these  reservoirs  stand 
against  the  abdominal  sacs,  from 
which  they  are  separated  by  the 
thoraco-abdominal  diaphragm  ;  be- 
low, they  respond  to  the  sternal  ribs 
and  the  lateral  parts  of  the  sternum  ; 
above,  to  the  pulmonary  diaphragm  ; 
inwards,  to  the  thoraco-abdominal 
diaphragm  ;  outwards,  to  the  verte- 
bral ribs  and  intercostal  muscles. 

"  A  parabolic  opening,  situated  in 
the  middle  part  of  the  external  border 
of  the  lung,  or  a  little  more  behind, 
establishes  their  communication  with 
that  organ.  This  orifice,  which  is 
remarkable  for  its  great  dimensions, 
occupies  the  extremity  of  a  volumi- 
nous bronchial  tube  which  follows 
the  direction  of  the  generating  trunk, 
and  in  such  a  manner  that  this 
trunk  appears  to  pass  directly  to- 
wards the  posterior  diaphragmatic 
reservoir,  and  to  open  as  a  canal." 

6.  Abdomimd  reservoirs  {Yig.  337, 
5). — "The  two  air-sacs  situated  in 
the  abdomen  present  themselves, 
when  inflated,  as  two  enormous 
bladders,  the  capacity  of  each  differ- 
ing but  little  from  the  volume  of 
the  trunk.  Situated  between  the 
superior  and  lateral  parietes  of  the 
abdomen  on  one  side,  and  the  abdo- 
minal viscera  on  the  other,  they 
cannot  be  dilated  without  driving 
the  intestinal  mass  downwards  and 
inwards. 

"  Their  anterior  extremity,  con- 
tinuous with  the  lung,  is  somewhat 

inflected  to  pass  under  the  fibrous  arch  extending  from  the  spine  to  the  pelvis. 
"  Their  posterior  extremity,  dilated  and  voluminous,  responds  to  the  cloaca. 

Outwardly,  they  adhere  by  cellular  tissue  to  the  thoraco-abdominal  diaphragm, 


6ENERAL  VIEW  OF  THE  AIR-RESERVOIRS  OF  THE 
DUCK,  OPENED  INFERIORLY  ;  ALSO  THEIR  RELA- 
TIONS WITH  THE  PRINCIPAL  VISCERA  OF  THE 
TRUNK. 

1,  1,  Anterior  extremity  of  the  cervical  reservoirs  ; 
2,  thoracic  reservoir ;  3,  anterior  diaphragmatic 
reservoir;  4,  posterior  ditto;  5,  abdominal  reser- 
voir, a.  Membrane  forming  the  anterior  dia- 
phragmatic reservoir  ;  h,  membrane  forming  the 
posterior  ditto.  6,  Section  of  the  thoraco-abdomi- 
nal diaphragm,  d,  Subpectoral  prolongation  of 
the  thoracic  reservoir  ;  e,  pericardium  ;  /,/,  liver; 
g,  gizzard;  h,  intestines;  m,  heart;  n,  n,  section 
of  the  great  pectoral  muscle  above  its  insertion 
into  the  humerus ;  o,  anterior  clavicle  ;  p,  pos- 
terior clavicle  of  the  right  side  cut  and  turned 
outwards. 


TEE  RESPIRATOBY  APPARATUS  IN   BIRDS.  565 

the  parietes  of  the  abdomen,  and  those  of  the  pelvis.  Inwardly,  they  are  in 
contact  with  the  intestinal  mass  and  the  testicles  or  ovaries.  Below  and  in  front, 
they  rest  on  a  fibrous  septum,  which  in  all  birds  divides  the  abdominal  cavity 
into  two  smaller  cavities  :  one  anterior,  which  represents  the  abdomen  and 
lodges  the  liver,  the  other  posterior,  which  represents  the  pelvis  and  contains 
the  stomach  and  intestines.  This  fibrous  septum  is  extremely  remarkable  in 
large  birds,  particularly  the  Ostrich,  in  which  it  has  been  described  by  Perrault 
as  a  transverse  diaphragm  ;  it  is  inserted  into  the  entire  circumference  of  the 
pelvic  bones,  and  sustains  the  stomach  as  well  as  the  intestinal  tube.  Below  and 
behind,  the  abdominal  reservoirs  lie  on  the  intestines.  Above,  these  sacs  cover 
the  inferior  face  of  the  kidneys,  and  there  furnish  three  prolongations  :  1.  A 
supra-renal  prolongation.     2.  Two  femoral  prolongations. 

"  The  supra-renal  prolongation  leaves  the  principal  reservoir  at  the  postero- 
external part  of  the  kidneys  ;  from  thence  it  passes  obliquely  upwards  and 
forwards,  to  spread  over  the  superior  surface  of  the  kidney,  which  it  depresses 
when  the  abdominal  sac  is  inflated.  Arrived  at  the  internal  border  of  the 
kidneys,  these  prolongations  are  introduced  between  the  transverse  processes  of 
the  sacral  vertebrae,  and  ascend  from  behind  forwards  to  the  height  of  the  two 
first  dorsal  vertebra,  forming  two  triangular  canals  situated  above  the  sacrum, 
in  the  sacral  channels,  and  separated  from  one  another  by  a  series  of  correspond- 
ing spinous  processes.  The  supra-renal  prolongations  are  not  present  in  all 
birds  ;  they  are  particularly  observed  in  the  Gallinacas  and  diurnal  rapacious 
birds.  In  some  Palmipeds— the  Swan,  for  example — they  are  equally  developed  ; 
in  the  Ostrich,  they  are  replaced  by  the  supra-spinal  canals. 

"  The  femoral  prolongations'  are  two  in  number — an  anterior  small  and  a 
posterior  large  ;  they  arise  from  the  abdominal  reservoir  at  the  cotyloid  cavities, 
and  leave  the  pelvis  in  traversing  the  bony  opening  through  which  the  crural 
vessels  pass  ;  after  clearing  the  limits  of  these  cavities,  they  spread  around  the 
coxo-femoral  articulation,  and  terminate  in  a  caecum  in  the  majority  of  birds. 
In  diurnal  birds  of  prey,  they  communicate  with  the  femoral  canal  by  an  orifice 
situated  at  the  anterior  part  of  the  great  trochanter.-  These  prolongations,  very 
developed  in  the  Ostrich,  also  open  in  it  into  the  femoral  cavity  ;  it  is  not 
without  surprise  that  we  see  this  arrangement,  which  is  peculiar  to  birds  remark- 
able for  their  rapidity  and  power  of  flight,  also  present  in  those  to  which  asrial 
locomotion  has  been  entirely  denied.  The  abdominal  reservoirs  communicate 
with  the  lung  by  an  orifice  situated  beneath  the  fibrous  arch  of  the  diaphragm, 
and  disposed  like  the  rose  of  a  watering-can." 

Communication  of  the  Reservoirs  with  the  Bones. — "  The  communi- 
cations of  the  respiratory  apparatus  with  the  skeleton  in  birds  are  extremely 
numerous.     We  will  successively  examine  those  belonging  to  each  reservoir. 

"  The  bones  which  receive  air  from  the  thoracic  reservoir  are  :  1.  The 
anterior  clavicle,  which  is  perforated  at  its  two  extremities.  2.  The  posterior 
clavicles,  which  are  also  perforated  a  little  below  their  scapular  extremity.  3. 
The  sternum  which  presents  two  series  of  openings — the  middle  ones  that  con- 
duct the  air  into  the  sternal  ridge,  and  the  lateral  ones,  very  small,  six  to  eight 
in  number,  corresponding  to  the  intercostal  spaces.  4.  The  scapulEe,  which  offer 
one  or  more  apertures  at  their  anterior  extremity,  and  receive  the  air  for  the 
subscapular  prolongation.  5.  The  humerus,  which  obtains  the  air  for  the 
humeral  prolongation  by  a  fossa  situated  at  the  inferior  and  internal  part  of  its 
articular  head.     6.  The  sternal  ribs,  which  allow  the  atmosphere  to  penetrate 


566  RESPIRATORY  APPARATUS  IN  BIRDS 

by  small  openings  at  their  inferior  extremities.  To  smn  up,  eight  bones,  without 
reckoning  the  sternal  ribs,  whose  number  varies,  receive  the  air  which  tills  them 
from  the  thoracic  reservoir. 

"The  cervical  reservoirs  conduct  the  air.  1.  To  all  the  cervical  vertebrae. 
2.  To  all  the  dorsal  vertebras.  3.  To  all  the  vertebral  ribs.  The  vertebrae  of 
the  neck  are  crated  in  their  anterior  part  by  the  currents  which  accompany  the 
vertebral  artery,  and  in  their  posterior  part  by  the  interspinal  current.  The 
first  obtain  entrance  to  the  anterior  segment  by  one  or  more  orifices  made  in 
the  inner  wall  of  the  intertransverse  canals  ;  the  median  current  penetrates  the 
posterior  segment  by  two  orifices,  a  right  and  left,  situated  on  the  inner  and 
medullary  wall  of  that  segment.  The  first  vertebra  of  the  back  is  provided 
with  air  in  the  same  manner,  by  the  middle  and  lateral  currents  of  the  neck. 
This  air,  after  passing  through  the  first  vertebra,  leaves  by  its  lateral  parts  to 
enter  a  small  sac  ;  from  this  it  goes  into  the  superior  part  of  the  second 
vertebra,  escapes  from  this  by  its  lower  portion,  to  be  received  into  a  lateral  sac, 
and  so  on  to  the  last  dorsal  vertebra.  These  sacs  also  supply  the  vertebral  ribs 
with  air,  which  enters  them  by  very  small  apertures  situated  at  their  spinal 
extremity. 

"  The  diaphragmatic  reservoirs  have  no  bony  communications.  The  abdo- 
minal reservoirs  supply  :  1.  The  sacrum.  2.  The  coccygeal  vertebrae.  3.  The 
iliac  bones.  4.  The  femurs.  The  air  traversing  the  sacrum,  coccyx,  and  ileum, 
comes  directly  from  the  supra-renal  prolongations,  and  that  filling  the  femoral 
cavity  from  the  femoral  prolongations.  In  this  enumeration  of  the  communi- 
cations between  the  skeleton  and  the  respiratory  apparatus,  we  have  taken  as 
a  type  the  most  aerated  skeleton  :  that  of  diurnal  birds  of  prey,  like  the  eagle, 
kite,  hawk,  etc. ;  the  bones  which  communicate  with  the  air-sacs  are  not  so 
numerous  in  the  other  classes.  In  this  respect,  they  may  be  ranged  in  three 
categories  :  1.  Those  which  are  serif erous  in  all  classes.  2.  Those  in  certain 
classes  only.  3.  And  those  which  are  not  so  in  any  class.  The  bones  always 
aerated  are  the  cervical  and  dorsal  vertebrae,  the  sternum,  and  we  may  add  the 
humerus,  though  it  is  not  s6  in  the  Ostrich.  Those  crated  in  some  classes  only 
are  :  the  furculum,  clavicles,  scapulae,  vertebral  and  sternal  ribs,  the  sacrum, 
coccyx,  and  femurs.  And  the  bones  which  are  never  aerated  are  those  of  the 
forearm  and  hand,  the  leg  and  foot." 

Structure  of  the  Reservoirs. — The  walls  of  these  cavities  are  essen- 
tially formed  by  a  thin  cellulo-serous  membrane,  strengthened  in  some  places 
by  an  external  envelope  of  elastic  fibrous  tissue.  Long,  thin  blood-vessels  are 
distributed  to  the  substance  of  these  walls  ;  they  do  not  belong  to  the  pul- 
monary, but  to  the  general  circulation,  the  arteries  being  derived  from  the 
aorta,  and  the  veins  opening  directly  or  indirectly  into  the  venae  cava.  No 
lymphatics  have  been  found  in  the  air-sacs. 

Mechanism  of  Respiration  in  Birds. — The  anatomical  arrangement 
described  above  differs  in  so  many  respects  from  that  existing  in  Mammals,  that 
it  ought  to  bring  about  important  modifications  in  the  mechanism  of  respiration. 
It  does  not  come  within  our  scope  to  write  the  history  of  these  modifications  ; 
but  we  cannot  dispense  with  indicating,  in  a  summary  way,  their  principal 
characters,  in  order  to  make  known  in  a  general  manner  the  signification  of  the 
special  organization  this  apparatus  oifers  in  birds. 

We  remark,  in  the  first  place,  that  the  slight  mobility  of  the  vertebral  ribs, 
and  the  adhesion  of  the  lung  to  their  inner  face,  only  allows  of  a  very  slight 


THE  RESPIRATORY  APPARATUS  IN  BIRDS.  567 

dilatation  of  that  viscus  during  inspiration.  And  the  entrance  of  air  into  the 
pulmonary  tissue  is  not  due  to  this  dilatation  ;  it  is  due  to  the  dilatation  of  the 
diaphragmatic  reservoirs  ;  the  position  of  these  effectively  admits  of  their  expan- 
sion, by  the  play  of  the  inferior  on  the  superior  ribs.  The  air  is  then  drawn 
into  their  cavity  after  traversing  the  larger  bronchial  tubes  which  open  into 
them,  and  also  after  passing  across  a  certain  region  of  the  capillary  network 
formed  by  the  canaliculi,  where  it  comes  into  mediate  contact  with  the  blood, 
and  is  submitted  to  the  necessary  transformations.  The  atmosphere,  therefore, 
arrives  in  the  diaphragmatic  sacs  partly  pure  and  partly  altered  by  its  contact 
with  the  blood.  During  expiration,  it  again  resumes  the  course  it  followed  on 
its  introduction,  traverses  a  second  time  the  lung,  and  is  thus  respired  once 
more  before  being  expelled  from  the  body.  It  is,  therefore,  obvious  that  the 
hasmatosic  transformations  accomplished  in  the  lung  take  place  during  the  two 
acts  of  respiration — inspiration  and  expiration. 

In  studying  the  part  that  the  other  reservoirs  play  m  this  function, 
Sappey  has  been  able  to  prove  that  they  act  as  antagonists  to  the  first,  by 
contracting  during  inspiration  and  expanding  in  expiration.  No  doubt,  at  the 
time  of  the  contraction  of  the  middle  reservoirs,  a  small  quantity  of  the  air  they 
contain  is  driven  back  into  the  anterior  and  posterior  sacs  in  passing  across  the 
lung  ;  and  without  doubt,  also,  these  latter  give  a  part  of  their  contents  to  the 
diaphragmatic  sacs  at  the  moment  of  the  expansion  which  draws  the  air  into 
these  reservoirs.  Sappey  has  also  noted  that  these  contents  are  always 
formed  of  entirely  vitiated  air,  while  the  air  of  the  middle  reservoirs  has  only 
been  partially  respired. 

It  is  necessary  to  add  that  the  functions  of  the  air-sacs  do  not  cease  here  ; 
for  it  has  been  demonstrated  that  they  exercise  a  very  marked  influence  :  1.  On 
locomotion,  by  diminishing  the  weight  of  the  body,  and,  by  their  position, 
rendering  equiUbrium  more  stable.  2.  On  the  voice,  thfi  range  and  power  of 
which  they  augment. 


BOOK  IV. 

THE  URINARY  APPARATUS. 

This  apparatus,  though  simple,  yet  plays  a  very  important  part  in  the  animal 
economy,  as  it  is  charged  with  the  duty  of  eliminating  from  the  blood — along 
with  the  superfluous  water  and  other  accessory  substances — the  excrementitial 
nitrogenous  products  resulting  from  the  exercise  of  the  vital  functions.  These 
products  we  find  in  the  urine  —the  liquid  secreted  by  the  kidneys,  and  which 
is  carried  by  the  iireters  into  a  special  reservoir— the  bladder — where  it  accumulates, 
and  whence  it  is  expelled  from  the  body  by  the  urethral  canal,  at  periods  more  or 
less  distant,  according  to  the  requirements  of  the  animal. 

The  kidneys,  the  essential  organs  of  urinary  depuration,  will  be  first  studied  ; 
then  the  excretory  apparatus ;  and,  finally,  a  brief  notice  will  be  given  of  the 
supra-renal  c«jt?sM/es— small  bodies  annexed  to  the  kidneys,  the  function  of  which 
is  not  yet  determined. 

Preparation. — Place  the  animal  in  the  first  position,  and  remove  one  of  the  posterior  limbs. 
Take  out  the  intestines,  adopting  the  precautions  indicated  at  page  455.  Saw  througli  the 
pelvic  symphysis,  as  well  as  the  neck  of  the  ilium  on  the  side  opposite  the  remaining  abdominal 
limb,  removing  the  coxal  portion  between  these  sections.  The  pelvic  cavity  being  now 
opened,  the  urinary  apparatus  is  exposed,  and  to  complete  the  preparation  it  is  necessary  to : 
1.  Remove  the  peritoneum,  to  show  that  the  urinary  apparatus  is  situated  external  to  that 
membrane.  2.  Free  the  ureters  and  kidneys  from  the  cellulo-adipose  tissue  surrounding  them, 
but  retaining  the  vessels  of  the  latter,  and  leaving  undisturbed  their  relations  with  the  pan- 
creas and  supra- renal  capsules.  3.  Inflate  the  bladder,  and  dissect  its  neck,  taking  care  to 
preserve  the  orbicular  peritoneal  fold  which  envelops  its  anterior  cul-de-sac  (or  fundus). 

In  the  male,  the  inflation  of  the  bladder  is  very  simple,  and  requires  no  directions.  In  the 
female,  however,  it  is  requisite  first  to  close  the  meatus  urinarius,  which  is  accomplished  by 
drawing  its  two  lips  towards  the  entrance  to  the  vulva,  by  means  of  two  chain-hooks,  passing 
two  pins  through  their  mucous  membrane,  and  tying  a  ligature  behind  these ;  the  bladder  is 
then  inflated  by  the  ureter. 

Independently  of  this  dissection  in  situ,  it  is  advisable  to  examine  the  urinary  apparatus 
when  isolated,  and  laid  arranged  upon  a  table,  as  in  Fig.  338.  We  can  then  study :  1.  By 
dissection,  the  structure  of  the  kidneys  and  arrangement  of  the  pelvis  reualis.  2.  The  mode  of 
termination  of  th«  ureters.     3.  The  interior  of  the  bladder. 

1.  The  Kidneys  (Figs.  258,  338). 

Situation. — These  are  two  glandular  organs  situated  in  the  abdominal  cavity, 
to  the  right  and  left  of  the  sublumbar  region,  lying  against  the  great  psoas 
muscles,  and  maintained  in  that  position  :  1.  By  an  envelope  of  cellulo-adipose 
tissue.  2.  By  the  peritoneum,  which  passes  beneath  them.  3.  By  the  pressure 
of  the  digestive  organs  contained  in  the  abdominal  cavity. 

Their  situation  is  not  absolutely  alike,  for  the  right  comes  forward  to  beneath 
the  two  last  ribs,  while  the  left  scarcely  reaches  beyond  the  eighteenth  rib.  The 
latter  is,  therefore,  more  posterior  than  the  former. 

External  conformation. — Studied  externally,  the   kidneys  present  a   special 


THE  URINARY  APPARATUS. 


569 


form,  which  often  serves  as  a  term  of  comparison,  and  resembles  more  or  less 
that  of  a  haricot  bean,  or  the  heart  on  a  playing-card.     The  latter  configuration 

Fig.  338. 


STTPERIOR   AND   GENERAL   VIEW   OF    THK   (il:;MTO-URIXARY   APPARATUS   IN  THE    MALE,    WITH   THE 

ARTERIES. 

A,  Left  kidney  ;  B,  right  kidney ;  a,  b,  ureters  ;  C,  C,  supra-renal  capsules  ;  D,  bladder ;  e,  e,  tes- 
ticles; e,  head  of  the  epididymus  ;  e',  tail  of  the  epididymus ;  F,  deferent  canal  ;  G,  pelvic  dilata- 
tion of  the  deferent  canal ;  H,  left  vesicula  seminales  (the  right  has  been  removed,  along  with  the 
deferent  canal  of  the  same  side,  to  show  the  insertion  of  the  ureters  into  the  bladder) ;  i,  prostate  ; 
J,  Cowper's  glands;  K,  membranous,  or  intra-pelvic  portion  of  the  urethral  canal;  L,  its  bulbous 
portion  ;  M,  cavernous  body  of  the  penis  ;  m,  m,  its  roots  ;  N,  head  of  the  penis.  1,  Abdominal 
aorta;  2,  2,  arteries  (renal)  giving  off  the  principal  capsular  artery;  3,  spermatic  artery;  4, 
common  origin  of  the  umbilical  and  arteries  of  the  bulb  ;  5,  umbilical  artery  ;  6,  its  vesical  branch ; 
7,  internal  artery  of  the  bulb;  8,  its  vesico-prostatic  branch. 


570  UBINABY  APPARATUS. 

is  most  frequently  noticed  in  the  right  kidney,  the  left  being  generally  like  the 
first. 

Flattened  on  both  sides,  the  kidneys  show  two  perfectly  smooth  faces,  the 
inferior  of  which  always  exhibits  a  variable  nmnber  of  fm-rows  that  lodge  the 
arteries  ;  the  right  kidney  has  always  a  special  furrow  for  the  ureter.  Each 
kidney  has  a  circumference  divisible  into  three  borders,  only  the  internal  of 
which  offers  a  certain  interest.  This  is  deeply  notched,  to  form  the  Jissure  or 
hilus  of  the  kidney,  which  lodges  the  vessels  and  nerves  of  the  organ,  as  well  as 
the  origin  of  the  ureter. 

Weight. — The  kidneys  vary  much  in  weight  in  individuals.  The  right  is 
always  more  voluminous  and  heavy  than  the  left,  its  average  weight  being 
27  ounces,  while  that  of  the  last  is  25  ounces. 

Relations. — The  relations  of  these  two  glands  with  the  neighbouring  parts 
ought  to  be  particularly  examined.  The  right  kidney  is  related,  by  its  upper 
face,  to  the  great  psoas  muscle,  the  muscular  portion  of  the  diaphragm,  and  to 
the  last,  or  even  the  second-last  rib.  Its  inferior  face,  incompletely  covered  by 
peritoneum,  adheres,  for  the  greater  part  of  its  extent,  either  to  the  pancreas  and 
supra-renal  capsule,  or  to  the  base  of  the  caecum,  by  means  of  a  loose  and 
abundant  connective  tissue.  The  internal  border  is  in  contact  with  the  posterior 
vena  cava  and  the  small  psoas  muscle  ;  the  anterior,  with  the  base  of  the  right 
lobe  of  the  liver  and  the  lobule  of  Spigel  {lohus  caudatus),  through  the  medium 
of  the  peritoneum  ;  the  posterior  border  is  enveloped  in  peritoneum.  The  left 
kidney  has,  by  its  superior  face,  the  same  connections  as  the  right,  except  in  its 
relation  with  the  second  last  rib.  Its  inferior  face  is  almost  entirely  covered  by 
peritoneum,  and  is  related,  in  front  and  inwardly,  to  the  supra-renal  capsule. 
The  internal  border  is  margined  by  the  aorta  ;  the  anterior  touches  the  base  of 
the  spleen  and  the  left  extremity  of  the  pancreas  ;  the  posterior  is,  like  the 
inferior  face,  in  contact  with  the  serous  membrane  of  the  abdominal  cavity. 

Internal  conformation. — If  a  horizontal  section  is  made  of  the  kidney,  it  will  be 
found  to  possess  a  cavity  called  the  rejial  basin  (or  pelvis),  into  which  the  urine 
secreted  by  the  gland  flows,  and  at  which  the  ureter  commences.  Placed  in  the 
middle  of  the  kidney,  near  the  hilus,  the  pelvis  is  elongated  before  and  behind, 
and  depressed  from  above  to  below.  Within  it  is  remarked  a  wide  infundibulum — 
the  origin  of  the  ureter  (the  sinus  renalis).  Opposite  to  this  funnel-shaped  space 
is  a  very  prominent  crest  (;renal  crest)  that  runs  along  the  whole  length  of  the 
external  side  of  the  pelvis,  and  on  which  are  noticed  the  orifices  of  the  urinif  erous 
tubes  ;  these,  by  pressing  the  tissue  of  the  kidney  with  the  fingers,  can  be  made 
to  pour  out  the  urine  accumulated  in  them.  The  renal  cavity  forms  some  very 
small  diverticuli  opposite  the  infundibulum,  the  largest  of  which — situated  before 
and  behind  the  latter — are  named  the  arms  of  the  pelvis. 

This  cavity  is  lined  by  a  transversely  plicated  mucous  membrane,  continuous 
with  that  of  the  ureter,  and  is  covered  with  the  epithelium  of  the  uriniferous 
tubes  which  open  on  the  border  of  the  crest.  At  these  folds,  the  mucous  mem- 
brane contains  small  racemose  glands  lined  by  two  layers  of  cells  (Paladiuo  and 
Egli). 

Structure. — The  kidneys  present  for  study  in  their  structure  :  1.  An 
enveloping  tunic.    2.  Than  2Jroper  tissue.    3.  Vessels  and  nerves. 

1.  Enveloping  Tunic. — This  is  a  fibrous  membrane,  intimately  united  to 
the  proper  substance  of  the  kidney,  into  which  it  sends  a  multitude  of  prolonga- 
tions, and  is  folded  around  the  blood-vessels  in  such  a  manner  as  to  form  sheaths, 


THE   VBINARY  APPARATUS. 


571 


which  enter  with  them  into  the  organ.  (Some  authors— among  them  Leyh— 
describe,  in  addition  to  this  capsula  propria,  a  thin  layer  formed  by  the  condensed 
areolar  matrix  of  the  kidney,  from  which  it  can  be  easily  torn.) 

Proper  Tissue. — The  glandular  tissue  of  the  kidneys  {areola  parmchijma,  or 
matrix)  has,  "externally,  a  reddish-brown  colour,  more  or  less  deep  in  different 
individuals.  It  is  dense  and  friable,  and  easily  torn  when  deprived  of  its  fibrous 
capsule.  Its  substance  is  not  everywhere  homogeneous  :  very  dark-coloured 
externally,  where  it  forms  the  cortical  layer,  it  becomes  whiter  around  the  pelvis, 
where  it  constitutes  the  medullary  layer  ;  where  the  latter  comes  in  contact  with 
the  former,  and  sometimes  even  near  the  pelvis,  it  assumes  a  tint  like  that  of 
wine. 

These  two  portions  are  not  well  defined,  but  penetrate  each  other  reciprocally, 
so  as  to  compose,  at  their  point  of  junction,  irregular  festoons,  very  readily  per- 
ceived in  a  horizontal  section  of  the  kidney  (Fig.  339). 

The  cortical  is  also  distinguished  from  the  medullary  substance  by  its  granular 

Fig.  339. 


HORIZONTAL   LOXGITUDINAL   SECTIOX  OF  THE   HORSE'S   KIDNEY. 

a.  Cortical  (or  vascular)  portion  ;  b,  medullary  (or  tubular)  portion  ;  c,  peripheral  portion  of  the 
latter ;  d,  interior  of  the  pelvis ;  d',  d',  arms  of  the  pelvis ;  e,  border  of  the  crest ;  /,  infundi- 
bulum :  a,  ureter. 


aspect,  and  the  presence  of  minute,  reddish  spheres,  readily  visible  to  the  naked 
eye,  and  named  Malpighian  corpuscles  ;  while  the  medullary  substance  appears  to 
be  composed  of  radiating  fibres. 

In  the  Horse,  the  tissue  of  the  kidney  cannot  be  divided  into  lobules  or 
pyramids  ;  to  the  naked  eye  it  appears  to  be  composed  of  fibres  that  start  from 
every  part  of  its  exterior,  and  converge  towards  the  crest  of  the  pelvis.  A  micro- 
scopical examination  demonstrates  these  fibres  to  be  canals  or  tubes  ;  hence  they 
are  designated  tuhuU  uriniferi,  or  Bellini's  tubes.  A  delicate  connective  tissue — a 
kind  of  stroma,  which  is  very  rare  in  the  cortical,  but  more  abundant  in  the 
medullary  substance,  especially  in  the  vicinity  of  the  pelvis — sustains  the  vessels 
and  nerves,  and  unites  the  tubuh  uriniferi  to  each  other. 

The  tuhuli  uriniferi  are  constituted  by  a  proper  amorphous  membrane,  very 


572 


URIXARY  APPARATUS. 


thin  and  elastic,  the  internal  face  of  which  is  lined  by  simple  epithelium  that 
readily  alters  -,  the  cells  are  polygonal  in  certain  points,  polyhedral  in  others,  and 
transparent  or  granular. 

The  uriniferous  tube  has  not  everywhere  the  same  direction  or  diameter. 
Taking  it  at  its  termination  on  the  crest  of  the  pelvis,  and  following  it  to  its 
origin  in  the  Malpighian  body,  it  is  found  that  the  tubule  is  at  firet  single, 
straight,  and  voluminous,  but  that  during  its  com'se  across  the  medullary  sub- 
stance it  divides  into  three  or  four  tubes,  which,  in  their  turn,  subdivide  in  a 
dichotomous  manner.  These  divisions  are  less  voluminous  and  straight  (col- 
lected in  bimdles,  they  are  the  pi/ramids  of  Ferrein),  but  their  diameter  is 
uniform  until  they  reach  the  cortical  substance  ;  here  they  bifurcate,  each  branch 
becomes  flexuous,  and  is  designated  the  uniting  or  junctional  tube,  and  is  con- 
tinued in  a  kind  of  elongated  U  shape — the  looped  or  ansiform  tube  of  HenU — 
which  descends  towards  the  centre  of  the  kidney.  The  ascending  branch  of  this 
ansiform  tube — the  diameter  of  which  is  very  small — suddenly  dilates  on  entering 
the  cortical  substance,  describes  several  bends,  contracts  into  a  narrow  neck,  and 


SECTION   OF   THE   CORTICAL   SL'lSSTASCt;   OF   THE   KIDNEY. 

,  A,  Tubuli  uriniferi  divided  transversely,  showing  the  spheroidal  epithelium  in  their  interior} 
B,  Malpighian  capsule  ;  a,  its  afferent  branch  of  the  renal  artery  ;  5,  its  glomerulus  of  capillaries  , 
c,  c,  secreting  plexus  formed  by  its  efferent  vessels ,  d,  d,  fibrous  stroma. 


then  opens  into  a  Malpighian  body,  after  having  taken  the  name  of  convoluted 
tube. 

The  corpora  Mcdpighicma  (or  capsides)  are  minute  vesicles,  the  walls  of  which 
possess  the  same  structure  as  the  uriniferous  tubes  ;  each  lodges  a  cluster  of 
arterial  capillaries  or  renal  glomerulus,  and  has  two  opposite  openings  :  one  com- 
municating between  the  corpora  and  convoluted  tubes,  the  other  affording  a 
passage  to  the  afferent  and  efferent  vessels,  which  serve  to  irrigate  a  tuft  of 
capillaries  forming  the  glomerulus  of  Malpighi.  Between  the  membrane  proper 
and  the  glomerulus  are  two  layers  of  epithelium — an  external  continuous  with 
that  of  the  uriniferous  tube,  and  an  internal  applied  directly  to  the  glomerulus 
and  forming  a  kind  of  hood  over  it  (lining  Bowman's  capsuJe). 

3.  Vessels  and  Nerves. — a.  The  kidney  possesses  a  special  artery  and  vein, 
remarkable  for  their  enormous  volume. 

a.  The  artery  (the  renal)  forms  several  branches  that  reach  the  kidney  by  its 
inner  border  and  inferior  face,  and  divide  into  a  certain  number  of  principal 
vessels,  which  are  disposed  in  a  wavy  manner  on  the  limits  of  the  cortical  and 
medullary  substances.      From  them  are  given  off  branches  to  each  of  these 


THE  URINARY  APPARATUS. 


573 


snbstances,  and  among  those  distributed  to  the  cortical  are  some  regularly 
disposed,  which  furnish,  on  each  side,  the  glomerule  ramifications  ;  these  are  the 
afferent  vessels,  or  Mcdpighian  glonwi/les  (or  ti^fts) ;  the  others  form  a  polyhedral 
plexus  around  the  convoluted  tubes  and  corpora  Malpighiana.  The  afferent  vessels 
of  the  renal  glomerules  enter  this  plexus. 

The  arterial  branches  of  the  medullary  substance  descend  between  and 
parallel  with  the  straight  tubes  (to  form  the  arteriolar  rectce),  and  anastomose  by 
transverse  branches,  so  as  to  form  a  network  with  elongated  meshes  (around  and 
between  the  tubuli). 

The  (renal  vein)  issues  from  the  kidney  by  the  hilus,  and  succeeds  the  arterial 


Fig.  341. 


Fig.  342. 


DISTRIBUTION   OF   THE   RENAL   VESSELS    IN   THE 
horse's   KIDNEY. 

a,  Branch  of  reaal  artery;  a/,  afferent  vessel; 
m,    m,    malpighian  tufts;     ef,    cf,     efferent 


vessels 
tubes  ; 


vascular  plexus  surrounding  the 
st,  straight  tube  ;  ct,  convoluted  tube. 


DIAGRAM   OF   THE   COURSE   OF   THE   URINI- 
FEROUS   TUBULE. 

a,  Orifice  of  tubule  at  pelvic  crest ;  5,  re- 
current bj'anches  which  form  loops,  c,  in 
the  medullary  portion  of  the  kidney,  and 
terminate  in  the  Malpighian  capsules  in 
the  cortical  portion. 


capillaries.  In  the  medullary  substance, 
there  are  straight  veins  as  there  are  straight 
arteries.  On  the  surface  of  the  organ, 
beneath  the  fibrous  envelope,  are  the  stellate 
veins  of  Verheyen — the  junction  of  five  or 
six  venules  which  converge  towards  a 
central  vein.  The  venules  of  the  two 
portions  collect  into  more  voluminous 
vessels,  which  form  complete  arches  at 
their    limits ;    it   is    to   the    presence   of 

these  vascular  canals  that  the  dark  colour  observed  at  this  point  of  the  renal 

tissue  must  be  attributed. 

h.  The  lymphatics  are  abundant  in  tlie  mass,  but  rare  at  the  superficies  of 

the  organ  ;    they  form  plexuses,  the  ultimate  branches  of  which  pass  to  the 

sublumbar  glands. 

c.  The  nerves  emanate  from  the  solar  plexus,  and  form  a  particular  network 

around  the  arteries,  exhibiting,  on  their  course,  some  microscopic  ganglia.     It  is 

not  known  how  they  terminate. 

DevelopmenTo — The  kidneys  appear  very  early  in  the  foetus,  above  and  a 


URINARY  APPARATUS. 


little  behind  the  Wolffian  bodies.  They  are  then  very  distinctly  lobiilated,  but 
the  lobes  gradually  become  fused,  and  have  entirely  disappeared  at  birth  ;  the 
small  irregularities  on  the  surface  are  the  only  indications  of  their  ever  having 
existed  in  Solipeds. 

Functions. — The  kidneys  are  the  organs  which  secrete  the  urine  ;  but  this 
secretion  does  not  take  place  to  the  same  extent  in  all  parts  of  their  tissue.     The 

abundance  of  vessels  in  the  cortical 


Fig.  343. 


TRANSVERSE   SECTION   OF   THE   KIDNEY. 

1,  Inferior  border  ;  2,  cortical  tissue  ;  3,  section  of 
blood-vessels;  4,  pelvis;  5,  ureter;  6,  superior 
border ;  7,  renal  artery ;   8,  proper  capsule. 


of 


substance,  the  presence  of  the  Mal- 
pighian  corpuscles,  and  the  flexuosi- 
ties  described  by  the  uriniferous 
tubes,  sufficiently  indicate  that  this 
substance  should  be  the  principal,  if 
not  the  exclusive,  seat  of  the  secre- 
tory function.  But  in  what  manner 
does  this  secretion  take  place  ?  At 
present  it  is  generally  agreed  that 
the  urinary  secretion  is  simply  an 
infiltration  of  the  elements  of  the 
urine  contained  in  the  blood,  through 
the  walls  of  the  vessels  of  the  glome- 
rulus. The  difference  existing  be- 
tween the  diameter  of  the  afferent 
and  efferent  vessels  of  the  Malpighian 
glomerules — a  fact  the  importance 
of  which  was  pointed  out  by  Ludwig 
the  urine  through  the  tissue  of  the 


— sufficiently  explains  this  filtration 
kidneys. 

The  nutritive  principles  of  the  serum  which  leave  the  blood  at  the  same  time 
as  those  of  the  urine,  are  taken  up  by  the  epithelium  of  the  uriniferous  tubes. 

2.  The  Ueeteks  (Fig.  338). 

Form. — The  ureter  is  a  membranous  canal,  the  diameter  of  a  thick  goose- 
quill,  which  conveys  the  urine  from  the  pelvis  of  the  kidney  into  the  bladder. 
Its  origin,  course,  termination,  and  structure,  will  be  successively  considered. 

Orif/in. — It  has  been  already  shown  that  the  origin  of  the  ureter  is  at  tKe 
infundibulum  of  the  pelvis  of  the  kidney  ;  it  leaves  that  organ  by  the  internal 
fissure  or  hilus,  curves  outwards,  passes  along  its  lower  face,  and  is  inflected 
backwards  in  quitting  the  organ. 

Direction. — The  course  it  follows  is  almost  in  a  straight  line  towards  the  pelvic 
cavity,  along  with  the  posterior  aorta  or  posterior  vena  cava,  according  to  the  side 
to  which  it  belongs  ;  it  is  in  contact  with  the  psoas  parvus,  and  proceeds  above  the 
peritoneum.  After  passing  beyond  the  terminal  branches  of  the  posterior  aorta, 
which  it  crosses  very  obliquely,  it  becomes  enveloped  in  a  short  peritoneal  fold  that 
maintains  it  against  the  lateral  wall  of  the  pelvis  ;  it  afterwards  emerges  from 
this  fold,  and  reaches  the  posterior  and  superior  part  of  the  bladder. 

Termination. — Having  reached  that  viscus,  its  termination  takes  place  as 
follows  :  instead  of  opening  directly  into  the  bladder  by  traversing  at  once,  and 
perpendicularly,  the  two  membranes  composing  the  organ,  the  ureter  at  first 
pierces  the  muscular  coat,  between  which  and  the  mucous  membrane  it  passes  for 
about  an  inch,  and  then  opens  on  the  surface  of  the  latter.     This  arrangement 


TEE  URINARY  APPARATUS.  575 

prevents  the  "flowing  back  of  the  urine  into  the  nreter  during  its  expulsion,  the 
intermembranous  portion  of  that  canal  being  strongly  compressed  by  the  external 
pressure  then  exerted  by  the  muscular  coat,  and  by  the  internal  resistance  which 
the  accumulation  of  urine  in  the  bladder  opposes  to  this  pressure.  So  well  are 
Nature's  intentions  fuhilled  in  this  respect,  that  we  may  inflate  the  bladder  by 
the  ureter,  after  tying  the  canal  of  the  urethra,  and  press  vigorously  on  the  dis- 
tended organ,  without  being  able  to  make  a  single  bubble  of  air  pass  through  the 
perfectly  pervious  canal. 

Steuctuee. — The  excretory  canal  of  the  kidney  is  composed  of  three  tunics  : 

1.  An  internal  mucous  tunic,  continuous,  in  front,  with  that  lining  the  pelvis 
of  the  kidney,  and  behind,  with  that  of  the  bladder.  It  is  very  tliin,  pale, 
plicated  longitudinally,  and  has  a  stratified  tesselated  epithelium.  (It  has  some 
mucous  follicles,  but  no  villi.) 

2.  A  middle  inuscular  layer  arranged  in  two  orders — a  superficial,  the  fibres 
of  which  are  circular,  and  a  deep  set,  passing  in  a  longitudinal  direction.  (Leyh 
and  other  authorities  describe  the  arrangement  of  the  muscular  planes — which  are 
composed  of  smooth  fibres — to  be  the  reverse  of  this,  the  longitudinal  being  super- 
ficial, and  the  deep  circular.) 

3.  An  external  tunic,  composed  of  connective  tissue  and  elastic  fibres. 

The  muscular  tissue  of  the  ureter,  by  contracting,  accelerates  the  flow  of  the 
urine. 

3.  The  Bladdee  (Fig.  338). 

Position. — This  is  a  membranous  reservoir,  lodged  in  the  pelvic  cavity,  where 
it  occupies  more  or  less  space,  according  to  the  quantity  of  urine  it  contains  ;  it 
may  extend  beyond  the  pubis,  into  the  abdominal  cavity. 

Form. — Considered  in  a  moderate  state  of  plentitude,  the  bladder  is  ovoid  in 
figure  ;  its  large  extremity,  being  turned  forward,  forms  a  rounded  cul-de-sac 
{fundus),  at  the  bottom  of  which  is  remarked  a  kind  of  cicatrice,  caused  by  the 
obliteration  of  the  urachus.  The  other  extremity  terminates,  posteriorly,  by  a 
well-marked  constriction — the  neck  (or  cervix)  of  the  bladder — which  gives  rise 
to  the  urethral  canal. 

Weight. — The  average  weight  of  the  empty  bladder  is  about  sixteen  ounces. 

Relations  and  mode  of  attachment. — The  bladder  is  related  :  above,  to  the 
vesiculae  seminales,  to  the  pelvic  dilatations  of  the  vasa  deferentia,  as  well  as  to 
the  rectum  ;  below,  to  the  inferior  wall  of  the  pelvis,  on  which  it  rests  (by  its 
base)  ;  on  the  sides,  to  the  lateral  walls  of  that  cavity.  In  the  female,  the  upper 
face  of  the  bladder  is  in  relation  with  the  uterus  and  vagina,  which  entirely 
separate  it  from  the  rectum.  The  posterior  extremity  or  neck  (cervix),  flanked  on 
each  side  by  the  lobes  of  the  prostate,  is  fixed  below  to  the  ischio-pubic  symphysis, 
by  means  of  a  particular  ligament  or  fasciculus  of  elastic  and  contractile  fibres, 
which  are  detached  from  the  muscular  layer,  and  expanded  over  the  lower  face  of 
Wilson's  muscle,  to  be  carried  backwards  and  downwards,  and  terminate  on  the 
surface  of  the  internal  obturator  muscle.  The  anterior  extremity — or  fundus — 
is  usually  related  to  the  pelvic  flexure  of  the  large  colon. 

This  extremity  is  covered  by  a  serous  cap,  which  is  prolonged  backwards  on 
its  body,  further  above  than  below.  This  covering  is  continuous  with  the 
parietal  layer  of  peritoneum,  and  adheres  closely  to  the  muscular  tunic  -of  the 
bladder,  so  that  it  constitutes  its  chief  attachment  ;  its  arrangement  is  precisely 
similar,  in  principle,  to  that  of  the  other  serous  visceral  membranes. 


576  V BINARY  APPARATUS. 

Thus  the  peritoneum,  after  covering  the  walls  of  the  pelvis,  is  re/lected  on  the 
organs  contained  in  that  cavity,  and  in  particular  on  the  bladder,  around  which 
it  forms  an  orbicular  fold.  This  again  gives  rise  to  three  secondary  folds — a  kind 
of  serous  layers — which  are  usually  termed  the  ligaments  of  the  bladder.  One  of 
these  layers  is  single  and  vertical  {broad  ligament),  and  is  fixed  to  the  inferior 
part  of  tlie  fundus  ;  it  is  not  rare  to  see  it  prolonged  forward  on  the  lower  wall  of 
the  abdomen,  as  far  as  the  umbilicus  ;  on  its  free  border  it  is  said  to  have  a  thin 
hem  or  cord — the  last  vestige  of  the  urachus.  If  this  cord  exists — which  appears 
doubtful  to  us — it  cannot  possess  the  signification  given  to  it ;  for  the  urachus  has 
not.  like  the  umbilical  arteries,  an  abdominal  portion  ;  it  only  commences  at  the 
umbilicus  to  be  prolonged  in  the  cord  to  the  allantois.  The  other  two  serous 
layers  {umbilical  ligaments) — ^pairs  and  horizontal — are  attached  to  the  sides  of  the 
fundus,  and  present,  on  their  free  border,  a  thick  cord,  the  obliterated  umbilical 
artery. 

(These  are  the  so-called /a/se  ligaments.  There  are  true  ligaments,  formed  by 
processes  of  the  pelvic  fascia,  which,  in  the  male,  are  :  the  inferior,  attaching  the 
prostate  gland  to  the  bladder ;  the  lateral,  attached  to  the  sides  ;  and  a  recto- 
vesical, between  the  bladder  and  rectum.  In  the  female,  there  are  the  vesico- 
uterine and  recto-uterine  ligaments.) 

Owing  to  this  disposition  of  the  peritoneum,  tne  bladder  is  divided  into  two 
perfectly  distinct  regions  :  an  anterior,  enveloped  by  a  serous  layer ;  the  other, 
posterior,  is  brought  in  contact  with  the  surrounding  organs  through  the  medium 
of  the  loose  and  abundant  connective  tissue  of  the  pelvic  region.  This  tissue — 
constantly  mixed  with  adipose  masses  around  the  neck  of  the  bladder — submits, 
with  the  serous  membrane  of  the  anterior  region,  to  the  changes  in  form  and 
continual  displacements  of  the  urinary  sac. 

Interior. — This  pouch,  studied  internally,  exhibits  folds  and  ridges  more  or 
less  marked,  according  to  its  state  of  plenitude.  It  also  shows,  posteriorly,  the 
opening  of  the  neck,  which  communicates  with  the  urethral  canal,  and  a  little 
higher,  the  orifices  of  the  ureters.  These  three  apertures  circumscribe  a  smooth 
triangular  space — the  trigone  {trigonum  vesicce). 

Structuee. — The  structure  of  the  bladder  is  very  simple.  Two  membranes 
compose  its  walls,  the  internal  of  which  is  mucous,  and  the  external  muscular. 
Anteriorly,  the  latter  is  covered  by  the  peritoneum  described  above. 

The  mucous  membrane  is  pale  and  thin,  and  is  continuous  with  that  lining 
the  ureters  and  the  urethra.  It  shows  some  papilli«  and  some  simple  tubular 
glands  towards  the  neck.  Its  epithelium  is  stratified  and  tesselated,  the  super- 
ficial cells  being  very  irregular. 

The  musndar  layer  is  composed  of  white  fibres,  the  arrangement  of  which  is 
very  complicated.  Certain  authorities  describe  three  superposed  planes,  the  fibres 
of  which  pass  in  different  directions.  In  the  Horse,  in  which  the  walls  of  the 
bladder  are  very  thin,  these  planes  are  difficult  to  demonstrate.  The  fibres  are 
longitudinal,  circular,  oblique,  spiral,  and  even  twisted  towards  the  fundus  of  the 
bladder ;  the  deep  fibres  are  reticulated.  In  the  posterior  region  they  do  not 
form  a  sphincter  around  the  neck  of  the  organ,  as  is  generally  beHeved  :  the  real 
sphincter  is  Wilson's  muscle,  which  encircles  the  membranous  portion  of  the 
urethral  canal. 

{k' submucous  layer,  composed  of  vascularized  connective  tissue,  has  been 
described  ;  it  loosely  connects  the  mucous  and  muscular  layers.) 

Vessels  and  nerves. — The  parietes  of  the  bladder  receive  their  blood  from 


TEE  URINARY  APPARATUS. 


577 


several  sources.  The  principal  arteries  come  from  the  vesico-prostatic  branch  of 
the  internal  pudic  ;  the  umbilical  artery  also  furnishes  ramifications  that  reach 
the  fundus  of  the  organ.  The  lymphatics  pass  to  the  sublumbar  glands.  The 
nerves  are  furnished  by  the  pelvic  or  hypogastric  plexus,  and  the  inferior  branches 
of  the  two  last  sacral  pairs  ;  their  twigs  are  spread  more  especially  between  the 
muscular  and  mucous  layers. 

Development. — The  study  of  the  development  of  the  bladder  is  very  interest- 


THE    KIDNEYS    AND    BLADDER    IN    THE    FCETUS   OF   SOLIPEDS. 

A,  Supra-renal  capsules  ;  B,  kidney  ;  b,  ureter ;  <;,  bladder ;  D,  urachus.     1,   abdominal  aorta ;  2, 
external  iliac  artery ;  3,  umbilical  artery ;  4,  umbilical  vein. 


ing.  It  is  narrower  and  more  elongated  in  the  foetus  than  the  adult,  and  is 
relatively  more  capacious  during  the  whole  period  of  intra-uterine  life.  It  then 
occupies  the  abdominal  cavity  as  far  as  the  umbilical  opening,  and  is  flanked  by 
the  two  umbilical  arteries.  Its  posterior  extremity  alone  enters  the  pelvis  ;  the 
anterior  extremity,  forming  a  real  neck,  is  continuous  with  the  urachus,  just  as 


578  URINARY  APPARATUS. 

the  neck,  properly  so  called,  is  continuous  with  the  urethra  (Fig.  344).  At  birth, 
this  anterior  neck  separates  from  the  urachus,  and  is  transformed  into  a  free  cul- 
de-sac  ;  while  the  bladder  is  gradually  withdrawn  into  the  pelvic  cavity,  carrying 
with  it  the  umbilical  arteries,  and  finishes  by  acquiring  the  position  it  definitively 
occupies  in  the  adult. 

Functions. — The  part  played  by  the  bladder  is  of  incontestible  utility.  In 
permitting  the  accumulation  of  the  urine  and  the  intermittent  expulsion  of  that 
excrementitial  fluid,  it  spares  animals  the  disagreeable  condition  in  wliich  they 
would  be  placed  if  the  hquid  secreted  by  the  kidneys  was  continually  being  dis- 
charged as  produced. 

4.  Urethra. 

The  description  of  this  organ  will  be  given  with  that  of  the  genital  organs, 
as  in  the  male  it  is  common  to  the  urinary  and  generative  apparatus  ;  even  in  the 
female  it  is  intimately  connected  with  the  latter. 

5.  The  Supra-renal  Capsules  (Fig.  338,  344). 

Situation — Form. — The  supra-renal  capsules  (or  adrenals)  are  two  small  bodies 
applied  to  the  lower  face  of  the  kidneys,  in  front  of  the  hilus,  and  close  to  their 
inner  border. 

They  are  elongated  from  before  to  behind,  flattened  above  and  below,  and 
irregularly  lobulated  on  their  surface.  Their  length  is  from  2  to  23  inches,  and 
width  from  li  to  H  inches.  They  have  not  the  same  volume,  the  right  being 
larger  than  the  left. 

delations. — A  large  amount  of  connective  tissue,  vessels,  and  nerve-filaments 
attach  these  bodies  to  the  neighbouring  organs.  The  right  is  related,  in  front, 
to  the  liver  ;  above,  to  the  right  kidney  ;  and  inwardly,  to  the  posterior  vena  cava 
and  the  ramifications  of  the  solar  plexus.  The  left  does  not  touch  the  liver  or 
spleen,  but,  by  its  inner  border,  is  applied  against  the  posterior  aorta  and  great 
mesenteric  artery. 

Structure. — At  present,  anatomists  are  not  agreed  as  to  the  structure  of  the 
supra-renal  capsules.  The  following  is  what  is  probably  most  reliable  in  this 
difficult  point  in  normal  histology. 

These  organs  offer  an  enveloping  membrane  and  parenchyma. 

The  enveloping  membrane  is  fibrous,  and  sends  off,  from  its  inner  face,  prolon-« 
gations  which  pass  into  the  parenchyma  and  form  cylindrical  spaces,  subdivided 
by  transverse  bands.  These  spaces  are  named  glandular  cavities  ;  but  the  septa 
soon  become  thin,  and  disappear  almost  completely,  leaving  nothing  but  some 
very  few  trabeculse  of  connective  tissue. 

The  parenchyma  is  divisible  into  two  layers — the  cortical  and  the  medullary 
substance.  The  first  is  of  a  dark-brown  colour  ;  the  second  is  yellow  and  soft, 
and  does  not  show  any  cavity  in  its  centre  ;  that  which  has  been  described  is  the 
result  of  the  destruction  of  its  proper  elements,  which  soon  change  after  death. 

The  glandular  cavities  of  the  cortical  substance  are  filled  with  nucleated, 
granular,  and  often  fat  cells,  in  the  adult  animal  ;  near  the  central  substance 
these  cavities  only  contain  a  single  cell. 

The  medullary  substance  has,  for  its  basis,  a  very  dehcate  reticulum,  support- 
ing stellate  cells  analogous  to  those  of  nerve-tissue. 

and  nerves. — Like  the  kidneys,  which  are  contiguous,  the  supra-renal 


THE   URINARY  APPARATUS.  579 

capsules  receive  a  large  quantity  of  blood,  compared  with  their  small  volume. 
The  arteries  are  branches  of  the  neighbouring  vessels — the  mesenteric  and  renal. 
They  form  a  very  delicate  plexus  in  the  parenchyma.  (They  keep  to  the  stroma 
of  the  trabeculae  ;  consequently,  their  finest  ramifications  are  found  in  the  secou- 
daiy  septa  of  the  cortical  substance,  where  they  form  elongated  plexuses,  which  are 
rounder  in  the  medullary  portion.  In  the  middle  of  the  latter,  the  venous 
ramuscules  unite,  and  give  rise  to  a  considerable  trunk — the  vena  supra-renalis — on 
which  the  organ  is  placed  as  on  a  pedicle.  It  is  this  vein  wliich  constitutes  the 
debated  cavity.) 

The  veins  are  satellites  of  the  arteries  in  the  tissue  of  the  organ,  and  pass  into 
the  renal  vein  or  posterior  vena  cava.     The  lymphatics  are  scarce. 

The  supra-renal  bodies  receive  many  ganglionic  nerves  derived  from  the  solar 
plexus,  but  their  mode  of  termination  is  unknown.  (As  mentioned  by  Chauveau, 
the  nerves  of  these  organs  are  extremely  numerous,  they  being  more  abundantly 
supplied  than  any  other  structure  of  the  kind  in  the  body  ;  a  large  number  of 
small  branches  enter  the  cortical  portion,  to  become  developed  in  the  medullary 
tissue.  As  these  nerves  do  not  leave  the  medullary  substance,  and  as,  besides,  its 
cellular  elements  appear  to  be  of  the  same  nature  as  the  multipolar  ganghonic 
cells,  it  is  presumed  that  the  nerve-fibres  emerge  from  these  globules,  and  that 
the  medulla  acts  as  a  ganglionic  nerve  centre.  Though  Leydig  fully  believed 
the  internal  portion  to  be  of  a  nei-vous  character,  he  thought  another  function 
might  be  attributed  to  the  cortical,  in  consequence  of  its  being  most  frequently 
of  a  fatty  nature.  Bergmann  was  the  first,  in  1839,  to  class  these  organs  with 
the  nervous  system,  and  Remak,  in  1847,  by  his  researches  in  embryology,  was  led 
to  group  them  with  the  sympathetic  ganglia,  and  named  them  nerve-glands. 
Injm-y  to  the  dorsal  portion  of  the  spinal  cord,  causes  congestion  and  hypertrophy 
of  the  supra-renal  capsules.  In  a  watery  solution  of  the  cortical  portion,  a  rose- 
tinted  substance  has  been  discovered,  which  changes  to  green  with  persalts 
of  iron.) 

Development. — These  bodies  are  relatively  larger  in  the  foetus  than  the  adult, 
though  this  difference  does  not  influence  their  structure. 

(Functions. — Their  uses  are  still  unknown  ;  they  are  ranked  in  the  category 
of  blood-vascular  glands,  along  with  the  spleen  and  thyroid  body,  the  functions 
of  which  are  also  not  yet  ascertained.  Leydig  is  of  opinion  that  these  bodies 
should  be  regarded  as  belonging  to  the  nervous  system  ;  but  it  is  probable  that 
they  are  concerned  in  the  processes  connected  with  pigmentation.) 

Differential  Characters  in  the  Urinary  Apparatus  of  the  other  Animals. 

1.  Kidneys. — In  the  other  domesticated  Mammals,  the  renal  glands  are  simple  or  multiple, 
or,  in  other  words,  simple  or  lobulated.  In  the  Ox,  the  kidneys  liave  an  elongated  shape 
from  before  to  beliind,  which  is  altogether  characteristic;  and,  in  addition,  they  preserve 
during  life  the  lobulated  form  only  seen  in  the  other  animals  during  intia-uterine  existence. 
Each  agglomeration  is  composed  of  from  fifteen  to  twenty  secondary  kidneys ;  but  the  pelvis 
is  not  formed  in  the  centre  of  this  agglomeration,  being  carried  altogether  outwards,  and 
occupying  an  excavation  in  the  interior  face  of  the  organ,  which  represents  the  hilus.  This 
cavity  is  divided  into  as  many  short,  wide  prolongations — the  calices — as  there  are  principal 
lobules ;  the  uriniferous  tubes  from  each  lobule  open  on  a  small  papilla,  which  projects  into 
the  bottom  of  the  calyx.  This  papilla  is,  therefore,  nothing  more  than  the  crest  of  the  simple 
pelvis  in  tlie  kidney  of  Solipeds  (Fig.  347). 

In  the  Sheep  and  Camel,  the  kidneys  are  not  lobulated,  and  the  pelvis  is  carried  to  the 
inner  border,  as  in  the  Horse.  In  these  animals,  as  well  as  in  the  Dog  and  Cat,  there  is  an 
arrangement  which  establishes  a  kind  of  transition  between  the  pelvis  of  the  Ox  and  that  of 


580 


URINARY  APPARATUS. 


Solipeds.  In  them,  this  cavity  is  very  large,  and  at  the  base  of  the  crest  shows  deep  diverticuli 
that  iMmity  in  the  substance  of  the  kidnev. 

The  kidneys  of  the  Pig  are  simple  externally,  and  voluminous;  the  hilus  gives  access  to 
a  cavity  in  which  are  a  number  of  papillae  collected  in  twos  or  threes,  and  covered  by  calices. 
The  calices  and  the  ureter  have  tiie  same  arrangement  as  in  the  Ox.  (There  are  10  or  12 
papillse,  and  as  many  calices.) 

2.  Bladder.— The  most  important  difference  in  the  bladder  of  the  domesticated  animals, 
consists  in  the  extent  of  development  of  its  peritoneal  envelope.  In  nonsoliped  animals  this 
covers  all  the  organ  to  the  neck ;  the  ligaments  are  also  very  short,  and  the  viscus  may  be 
easily  projected  into  the  abdominal  cavity.  The  bladder  is  thin,  and  of  considerable  capacity 
in  Ruminants  and  the  Pig ;  in  tJie  Dog,  on  the  contrary,  it  has  a  very  thick  muscular 
layer,  its  fibres  forming  distinct  fasciculi,  especially  when  in  a  state  of  retraction.  (In 
Ruminants,  the  orifices  of  the  ureters  are  near  each  other;  at  the  fundus  the  mucous 
membrane  shows  a  small  fossa,  which  is  continued  by  a  narrow  canal  that  terminates  in  a 


Fig.  345. 


Fig.  346. 


Fig.  347. 


KIDNEYS   OF  THE   OX. 


Fig.  345. — Right  kidney,  viewed  on  its  upper  and  external  face.  Fig.  346. — Left  kidney,  from  its 
internal  and  inferior  face:  a,  Pelvis;  b,  b,  b,  branches  of  the  pelvis  terminating  in  calices;  c, 
ureter;  (i,  renal  artery.  Fig.  347. — The  calices  in  the  left  kidney.  The  contents  of  the  hilus, 
including  the  branches  of  the  pelvis,  have  been  removed  to  show  the  tubercles  at  the  bottom  of 
these  calices.     Only  seven  are  visible,  the  others  being  beneath  the  borders  of  the  renal  fissure. 


cnl-de-sac,  and  constitutes  a  free  appendix  about  half  an  inch  long,  and  of  the  thickness  of  a 
goose-quill). 

3.  Supra-renal  capsules. — These  small  organs  are  discoid  in  the  Sheep  and  Pig,  reniform 
in  the  Dog.  In  the  Ox,  they  are  situated  at  a  certain  distance  in  front  of  the  kidneys,  and 
their  shape  is  like  that  of  these  bodies  in  the  Horse ;  though  they  are  a  little  constricte  i  in 
the  middle,  and  slightly  curved. 

In  Birds,  the  kidneys  "  are  lodged  at  the  same  height,  behind  the  peritoneum,  imme- 
diately pdsterior  to  the  lungs,  and  in  the  lumbar  and  pelvic  regions,  where  they  occupy  several 
fossae  excavated  in  the  upper  face  of  the  pelvis.  Their  form  is  irregular  and  more  or  less 
elongated,  depending  upon  the  hemes  and  other  parts  to  which  they  are  applied,  and  on  which 
they  are  moulded.     In  many  Birds,  nevertheless,  three  portions,  more  or  less  separated  by 


THE  URINARY  APPARATUS.  581 

fissures,  may  be  recognized.  The  ileo-lumbar  portion— so  named  because  of  its  constant 
position  in  this  region— is  the  most  advanced;  it  is  often  the  largest.  Tlie  middle  is  the 
narrowest ;  it  is  turned  towards  the  ileo-sacral  region,  to  enter  the  pelvis.  The  posterior  is 
contained  in  that  cavity,  and  is  again  larger.  These  two  latter  portions  are  designated  as  the 
anterior  or  superior  pelvic,  and  the  inferior  or  deep  pelvic  portions.  Their  internal  and 
superior  border  is  often  notched  by  a  series  of  transverse  fissures,  produced  by  the  protrusion 
of  the  transverse  processes  of  the  sacral  vert-^bras,  as  the  lungs  are  furrowed  by  the  projection 
of  the  ribs." ' 

The  excretory  apparatus  is  incomplete,  and  is  only  formed  by  the  ureters,  which  open  into 
the  cloaca,  where  tlie  urine  is  mixed  with  the  fseces.  Only  one  bird— the  Ostrich— possesses 
a  bladder,  which  is  disposed  in  a  particular  manner. 

Comparison  of  the  Urinary  Apparatus  of  Man  with  that  op  Animals. 

1.  Kidneys. — The  two  kidneys  of  Man  have,  like  those  of  tiie  smaller  domesticated  animals, 
the  same  shape — that  of  a  haricot  bean.  The  average  weight  is  about  from  three  to  five  ounces. 
Contrary  to  what  is  observed  in  the  Horse,  the  left  kidney  is  more  voluminous  tiian  the  right, 
and  is  higher. 

The  kidneys  are  simple  externally,  thougli  their  tissue  is  disposed  in  distinct  lobes,  which 
number  from  eight  to  fifteen,  and  each  is  composed  of  a  Malpighian  pyramid  and  a  superposed 
pyramid  of  Ferrein ;  they  terminate,  towards  the  hilus,  by  a  cone  or  renal  papilla,  each 
surrounded  by  a  calyx,  and  are  separated  by  small  prolongations  of  the  cortical  substance — 
the  columnx  Bertini. 

2.  Ureters. — These  canals  are  disposed  at  their  origin  as  in  the  Ox :  they  terminate  as  in  the 
other  animals.  In  the  hilus  of  the  kidney  are  from  eight  to  fifteen  prolongations  or  calices, 
■which  unite  into  a  larger  cavity  or  great  calyx,  tliat  finally  opens  into  the  renal  pelvis ;  this  is 
immediately  followed  by  the  ureter. 

3.  Bladder. — The  large  extremity  of  this  organ  is  directed  downwards  in  the  bottom  of  the 
pelvis,  where  it  is  continuous  with  the  urethral  can  il ;  its  summit  is  directed  upwards,  and  is 
frequently  pointed.  Its  mode  of  attachment  and  internal  conformation  are  the  same  as  in 
animals ;  and,  as  in  the  Horse,  the  peritoneum  envelops  it  very  incompletely.  The  muscular 
fibres  are  arranged  in  three  planes — -a  superficial,  which  forms  a  band  that  is  carried  from 
the  anterior  to  the  posterior  face  in  passing  over  the  summit ;  a  middle  plane,  the  fibres  of 
which  are  circular;  and  a  deep  plane  witii  reticulated  fibres. 

Supra-renal  capsules. — This  name  is  quite  appropriate  to  these  bodies,  as  in  Man — or  at 
least  in  the  foetus — they  form  a  kind  of  helmet  that  covers  the  upper  part  of  the  kidney. 
There  is  nothing  to  add  respecting  their  structure. 


'  Cuvier,  Anatomie  Compar^e,  2ud  Edition.     Paris  :  1836-46. 


BOOK  V. 


CIRCULATORY  APPARATUS. 


The  animal  economy  is  incessantly  traversed  by  two  fluids — hlood  and  lymph. 

The  hlood  is  a  fluid,  coloured  bright  red  or  brown  by  particular  globules, 
and  from  which  the  tissues  derive  not  only  the  materials  for  nutrition  and 
secretion,  but  also  the  exciting  principle  which  vivifies  the  organic  matter.  It 
is  named  red  or  arterial,  and  dark-coloured  or  venous  blood,  according  to  its  tint. 

The  lymph,  or  -white  hlood,  is  a  transparent,  citrine-coloured  fluid,  which  can 
be  obtained  from  most  of  the  organs.  That  which  comes  from  the  abdominal 
portion  of  the  alimentary  canal  is  charged,  during  digestion,  with  a  portion  of 
the  reparative  materials  elaborated  in  that  apparatus,  and  is  distinguished  by  its 
lactescent  aspect ;  it  is  designated  the  chyle. 

These  fluids  are  carried  by  vessels — tubes  continuous  with  one  another. 
When  joined  together,  end  to  end,  these  tubes  give  rise  to  three  principal  canals  : 


Fig.  348. 


THEORETICAL   PLAN   OF   THE   CIRCULATORY   SYSTEM. 

(H  D  0  E,  The  canal  for  red  blood ;  E  B  A  G,  canal  for  dark  blood.  The  arrows  indicate  the 
course  of  the  blood.  Tlie  two  canals  are  represented  in  their  middle  portion,  A  B,  CD,  as  isolated; 
but  in  nature  they  are  enveloped  at  this  poiut  in  a  common  sac  that  concurs  to  form  the  heart.) 


"  One  of  these  canals  extend  from  the  lungs  to  all  parts  of  the  body,  and  is 
traversed  by  red  blood. 

"  Tiie  second  extends  from  all  parts  of  the  body  to  the  lungs,  and  carries 
dark  blood. 

"  The  third  passes  from  the  majority  of  the  organs  towards  the  canal  carrying 
dark  blood,  in  which  it  terminates  ;  it  conveys  the  white  blood,  or  lymph. 

"  The  red-hlood  and  dark-hlood  canals  bear  the  greatest  analogy  to  each  other. 


THE  HEART.  583 

Both  are  simple  in  their  middle  portion,  which  alternately  dilates  and  contracts 
to  impress  upon  the  blood  the  movement  necessary  to  life.  Both  present  at  their 
extremities  innumerable  ramifications,  which  ultimately  join  each  other  ;  so  that 
the  fluid  they  carry  passes  from  one  to  the  other  in  a  constant  and  circular 
direction.  Both  are  composed,  at  their  origin,  of  vessels  in  which  the  blood 
moves  in  confluent  columns — these  are  the  veins ;  and  in  their  terminal  portion, 
of  vessels  in  which  the  same  fluid  is  spread  in  divergent  columns — these  are  the 
arteries  (Fig.  3*49). 

"  The  canal  for  ivhite  blood  is  composed  of  a  single  order  of  vessels — the 
lymphatics — converging  tubes,  the  common  trunk  of  which  opens  into  the  circu- 
latory canal  resulting  from  the  junction  of  the  red  and  dark  blood  vessels  ;  the 
relation  it  affects  with  these  latter,  is  that  of  a  tangent  with  its  circumference." 
(Sappey.) 

These  three  canals  constitute  the  circulatory  apparatus. 

This  apparatus  therefore  comprises:  1.  The  heart,  a  central  organ,  which 
propels  the  blood.  2.  A  system  of  centrifugal  vessels — the  arteries — which  carry 
the  blood  from  the  heart  into  the  different  organs.  3.  A  system  of  centripetal 
vessels — the  veins — which  bring  the  nutritive  fluid  to  the  heart.  4.  The 
lymphatics,  an  accessory  centripetal  system,  for  conveyance  of  lymph  into  the 
blood-vascular  circle. 

In  many  anatomical  works,  the  study  of  this  apparatus — the  heart,  arteries, 
veins,  and  lymphatics — is  designated  Angiology. 


FIRST  SECTION. 
THE   HEART. 


The  history  of  the  heart  comprises  :  1.  A  general  view  of  the  organ.  2.  The 
study  of  its  external  conformation.  3.  Its  interior.  4.  Its  structure.  5.  A 
description  of  the  pericardium,  the  serous  cavity  containing  it.  6.  A  glance  at 
its  physiology. 

1.  The  Heart  as  a  Whole  (Figs.  255,  349,  350). 

General  sketch. — The  heart — the  central  portion  of  the  circulatory  apparatus — 
is  a  hollow  muscle,  the  cavity  of  which  is  divided  by  a  thick  vertical  septum, 
into  two  perfectly  independent  chambers.  Of  these  two  contractile  cavities,  one — 
placed  on  the  track  of  the  dark  blood — propels  it  into  the  lungs  ;  the  other — 
situated  on  the  course  of  the  red  blood — distributes  it  to  all  parts  of  the  body. 

Each  of  these  is  subdivided  into  two  superposed  compartments  by  a  circular 
constriction,  at  which  is  a  membranous  valve  that,  at  certain  fixed  periods,  is 
elevated,  and  then  forms  a  comple  horizontal  partition  extended  between  the 
two  compartments. 

The  superior  compartment  receives  the  convergent  or  centripetal  portion  of 
the  blood-canal — that  is  the  veins  :  it  is  named  the  auricle.  The  inferior  gives 
origin  to  the  divergent  or  centrifugal  part  of  the  same  canal,  and  is  designated 
the  ventricle. 


584  CIRCULATORY  APPARATUS. 

The  cavities  of  the  heart  are  distinguished  into  right  or  anterior,  and  left  or 
posterior,  because  of  their  relative  positions.  There  are,  then  :  a  right  auricle 
and  ventricle — the  two  dark-blood  cavities  ;  and  a  left  auricle  and  ventricle, 
situated  on  the  track  of  the  red-blood  canal. 

Situation. — The  heart  is  enclosed  in  a  tibro-serous  sac,  named  the  jiei-icardium, 
and  is  placed  in  the  chest  between  the  two  layers  of  the  mediastinum,  opposite 
the  third,  fourth,  fifth,  and  sixth  ribs  ;  in  front  of  the  diaphragm,  which 
separates  it  from  the  abdominal  viscera  ;  above  the  sternum,  which  appears  to 
support  it ;  and  beneath  the  vertebral  column,  to  which  it  is  suspended  by  means 
of  the  large  vessels.  (Between  the  middle  of  the  anterior  border  of  the  heart, 
in  front,  and  the  entrance  to  the  chest,  is  an  interval  of  about  four  inches  ;  and 
behind,  at  the  same  level,  this  organ  is  at  a  similar  distance  from  the  diaphragm. 
It  is  distant  from  the  fifth  and  sixth  dorsal  vertebrte — from  which  it  is  suspended 
— about  4|  or  5  inches  in  an  average-sized  Horse.) 

Form  and  direction. — The  heart  presents  the  form  of  an  inverted  cone,  slightly 
depressed  on  each  side,  the  axis  of  which,  directed  obliquely  downwards  and 
backwards,  deviates  a  little  to  the  right  at  its  superior  extremity. 

Volume. — In  a  medium-sized  Horse,  the  greater  axis  of  the  heart  is  about  lO^- 
inches  in  length ;  its  antero-posterior  diameter,  measured  near  the  base,  is 
equivalent  to  about  7^  inches.  Its  lateral  diameter  does  not  exceed  from  5  to 
5^  inches. 

Ckimcitij. — It  is  very  difficult,  if  not  impossible,  to  obtain  the  exact  capacity 
of  the  heart's  cavities.  From  reasoning,  it  might  be  supposed  that  the  two  hearts 
have  exactly  the  same  capacity,  and  that  this  is  equivalent  to  an  average  of  from  1 
to  1;^  pints.  The  amount  obtained  by  measurement  is  much  more  considerable  ; 
but  then  the  heart  is  distended  to  a  greater  extent  than  in  its  physiological  state. 

Weight. — The  weight  of  the  heart  varies  with  the  size  of  the  animals,  and 
that  to  a  considerable  degree.  Its  average  is  about  6f  pounds.  (The  volume 
and  weight  of  the  heart  are  very  much  greater  in  well-bred  than  in  common-bred 
Horses.  Its  dimensions  and  capacity  are  greater  in  the  living  than  the  dead 
animal ;  as  after  death  its  cavities  contract,  particularly  the  aortic  ventricle, 
which  has  the  thickest  walls.  This  ventricle  will  then  scarcely  contain  more 
than  from  f  to  1^  giUs  ;  the  pulmonary  ventricle,  which  is  not  so  thick,  and  con- 
sequently less  contracted,  may  usually  receive  double  that  quantity  ;  while  in 
animals  experimented  on  when  expiring,  it  has  been  observed  that  these  two 
ventricles  were  much  more  capacious,  and  that  each  contained  at  least  from 
l^^  to  1|  pints.) 

2.  External  Conformation  of  the  Heart  (Figs.  349,  350). 

Preparation. — Eemovethe  heart,  and  with  it  a  certain  length  of  the  vessels  belonging  to  it; 
fill  its  cavitied  with  tow,  and  free  the  furrows  from  tiie  adipose  deposited  in  them. 

The  cone  represented  by  the  heart  is  divided  by  a  horizontal  groove  into  two 
unequal  portions  :  the  one  superior,  comprising  the  auricles  or  auricular  mass  ; 
the  other  inferior  or  principal,  formed  by  the  ventricles  or  ventricular  mass. 

A.  Ventricular  Mass. — It  is  this  which  determines  the  conical  shape  of 
the  heart,  and  constitutes  its  largest  portion.  Owing  to  a  slight  flattening  of  the 
organ  in  a  lateral  sense,  it  may  be  considered  as  having  a  right  and  left  face,  an 
anterior  and  posterior  border,  an  apex,  and  a  base. 

The  right  face,  smooth  and  rounded,  is  traversed  by  a  vascular  furrow  {right 


TEE  HEART. 


585 


ventricular  groove)  parallel  to  the  axis  of  the  heart,  and  which  divides  this  face 
into  two  sections — an  anterior,  belonging  to  the  right  ventricle  ;  and  a  posterior, 
less  extensive,  forming  part  of  the  left  ventricle  (Fig.  350). 

The  lefi  face,  disposed  in  the  same  manner,  also  shows  a  groove  (left  ventri- 
cular groove)  on  the  limit  of  the  two  ventricles,  which  slightly  crosses  the  large 
diameter  of  the  heart  from  behind  to  before,  and  above  to  below,  and  is  much 
nearer  the  anterior  than  the  posterior  border  (Fig.  349). 

Fig.  349. 


THE   HEART   AND    PRINCIPAL   VESSELS   (LEFT   FACE). 

a,  Right  ventricle ;  6,  left  ventricle ;  c,  right  auricle  ;  c?,  left  auricle ;  e,  pulmonary  artery ;  «*, 
obliterated  ductus  arteriosus;  /,  pulmonary  veins;  g,  anterior  aorta;  h,  left  axillary  artery; 
»,  right  axillary  artery,  or  brachio-cephalic  trunk;  j,  origin  of  the  dorsal  artery  ;  k,  origin  of  the 
superior  cervical  artery  ;  I,  origin  of  the  vertebral  artery  ;  m,  origin  of  the  inferior  cervical 
artery;  w,  origin  of  the  internal  thoracic  artery;  o,  origin  of  the  external  ditto;  p,  carotid 
arteries  ;  q,  posterior  aorta  ;  r,  anterior  vena  cava  ;  s,  trunk  of  the  axijlary  vein  ;  t,  trunk  of  the 
internal  thoracic  vein  ;  u.  trunk  of  the  dorsocervical  vein;  v,  posterior  vena  cava;  exjunction 
of  the  hepatic  and  diaphragmatic  veins;  x,  vena  azygos  ;  y,  thoracic  duct;  z,  embouchure  of 
that  vessel,  placed  near  the  origin  of  the  anterior  vena  cava.  1,  Right  cardiac  artery ;  2,  left 
cardiac  artery  ;  3,  auriculo-ventricular  branch  of  the  latter ;  4,  its  ventricular  branch  ;  5,  cardiac 
vein. 


These  two  faces  are  related,  through  the  medium  of  the  pericardium,  to  the 
plurfe  and  pulmonary  lobes  ;  the  latter  separate  them  from  the  thorax,  except 
towards  the  middle  and  apex  of  the  organ,  where  these  faces  come  directly  in 
contact  with  the  thoracic  parietes  through  the  notch  at  the  inferior  border  of  the 
lung,  and  which  is  more  marked  in  the  left  than  in  the  right. 

The  borders  are  thick,  smooth,  and  rounded.     The  anterior,  formed  by  the 


586 


CIRCULATORY  APPARATUS. 


right  ventricle,  is  very  oblique  downwards  and  backwards ;   it  niclines  on  the 

sternum  more  or  less,  according  to  su])jects. 

The  posterior   border,  much   shorter  than  the  anterior,  is  nearly  vertical. 

Superiorly,  it  is  separated  from  the  diaphragm  by  the  lung  ;  but,  below,  it  is  quite 

close  to  that  muscular  septum. 

The  apex,  or  point  of  the  ventricular  cone,  is  blunt,  slightly  rounded,  turned 

to  the  left,  and  formed  entirely  by  the  left  ventricle. 

The    base    is    related  on   the 
Fig-  350.  right,  in  front,  and  behind,  to  the 

auricles  ;  it  gives  off  on  the  left, 
and  a  little  in  front,  the  two 
arterial  aortic  and  pulmonary 
vessels. 

B.  Auricular  Mass. — Elon- 
gated from  before  to  behind,  dis- 
posed like  a  crescent  above  the 
right  side  of  the  base  of  the 
ventricles,  constricted  in  its  middle 
part,  on  the  limit  of  the  two 
auricles,  the  auricular  mass  pre- 
sents for  study  three  faces,  two  ex- 
tremities, and  a  base. 

The  superior  face  is  divided  by 
a  middle  constriction  into  two 
convex  sections,  each  of  which 
corresponds  to  an  auricle.  The 
anterior — or  right  section— shows 
the  entrance  of  the  anterior  vena 
cava  and  vena  azygos  ;  the  pos- 
terior— or  left  section — that  of  the 
pulmonary  veins.  The  trachea, 
bronchi,  and  pulmonary  artery  pass 
above  this  face  (Figs.  349,  350). 

The  right  face,  the  most  ex- 
tensive in  the  anteo-posterior 
direction,  is  divided  like  the  pre- 
ceding, and  disposed  in  a  similar 
manner.  The  right,  or  anterior 
part,  receives — behind  and  below — 
the  insertion  of  the  posterior  vena 
cava,  and  the  coronary  and 
bronchial  veins  (Fig.  350). 

The  left  face,    concave   from 

before  to  behind,  includes  the  arterial  trunks  which  leave  the  base  of  the  heart. 
Each  of  the  extremities — anterior  andposterior — constitutes  a  detached  portion, 

named  the  appendix  auricularis ;  these  appendages  are  curved  towards  each  other 

in  being   flattened   above  and   below.     Their  convex  border   is   more   or   less 

crenelated,  like  the  margin  of  a  cock's  comb,  and  their  culminating   portion 

advances  nearly  to  the    pulmonary  artery,  above  the  trunk  of    the  cardiac 

vessels  (Fig.  349). 


THE    HEART   AND   PRINCIPAL   VESSELS   (RIGHT   FACE). 

o,  Right  ventricle  ;  6,  left  ventricle ;  c,  right  auricle  ; 
d,  anterior  vena  cava ;  e,  vena  azygos ;  /,  posterior 
vena  cava ;  g,  g,  pulmonary  veins ;  h,  h,  divisions 
of  the  pulmonary  artery  ;  i,  posterior  aorta ;  j,  an- 
terior aorta;  k,  thoracic  duct;  /,  right  cardiac 
artery  ;  m,  its  vertical  o*-  ventricular  branch  ;  n,  its 
horizontal  or  auriculo-ventricular  branch  ;  o,  ven- 
tricular branch  of  the  cardiac  vein;  p,  auriculo- 
ventricular  branch  of  the  same. 


THE  HEART. 


587 


The  hase  of  the  auricular  mass,  opposed  to  the  base  of  the  ventricles,  is 
separated  from  it  at  its  periphery  by  the  horizontal  groove  {aimculo-vmtricular 
groove)  of  the  heart. 


3.  Inteknal  Conformation  of  the  Heart  (Figs.  351,  352,  358). 

Preparation.— It  sufBces  to  make  a  longitudinal  incision  before  and  behind  the  organ,  in 
order  to  expose  its  cavities.  (I  have  followed  Wilson's  directions  for  many  years  when 
examining  the  interior  of  the  heart,  and  as  a  careful  inspection  of  this  organ  is  often  necessary  in 
the  course  of  an  autopsy,  I  think  the  student  should  practise  the  best  method  of  laying  open 
these  cavities.  The  riglit  auricle  is  prepared  by  making  a  transverse  incision  along  its  ventri- 
cular margin,  from  the  appendix  tu  its  right  border,  and  crossed  by  a  perpendicular  incision, 
carried  from  the  si<]e  of  the  anterior  to  the  pos- 
terior cava.  The  right  ventricle  is  laid  open  by  Fig.  351 
making  an  incision  parallel  with,  and  u  little 
to  the  right  of,  the  middle  line,  from  the 
pulmonary  artery  in  front,  to  the  apex  of  the 
heart,  and  thence  by  the  side  of  the  midille  line 
behind  to  the  auric ulo- ventricular  opening. 
The  interior  of  the  left  auricle  is  expn^ed  by 
a  J_ -shaped  incision,  the  horizontal  section 
being  made  along  the  border  which  is  attached 
to  the  base  of  the  ventricle.  The  latter  is 
opened  by  making  an  incision  a  little  to  the  left 
of  the  septum  ventriculorum,  and  coutiuuing  it 
around  the  apex  of  the  heart  to  the  auriculo- 
ventricular  opening  behind.) 

If  the  heart,  when  viewed  externally, 
appears  to  be  a  simple  organ,  it  is  not 
so  when  examined  internally.  The 
vertical  septum  which  divides  it  into 
two  bil  ocular  cavities,  in  reality  makes 
two  hearts  of  it — one  for  the  dark,  the 
other  for  the  red  blood.  We  will  suc- 
cessively study  these  two  cavities,  by  com- 
mencing with  the  partition  that  separates 
them. 

A.  Cardiac  Septum. — The  superior 
part  of  this  septum,  between  the  two 
auricles,  is  named  the  inter-auricular 
partiUon  {septum  anricularum).  The 
inferior  portion  constitutes  the  inter- 
ventricular partition  {septum  ventricu- 
lorum). The  first— thin  and  not  exten- 
sive— is  perforated  in  the  foetus  by  the 
foramen  of  Botal  {foramen  ovale).  The  second,  thick  in  its  centre,  thins  a  little 
towards  its  borders. 

B.  Dark-blood  (or  Pulmonary)  Heart. — The  two  superposed  cavities 
forming  tliis  portion  are  situated  in  front  and  to  the  right.  They  are  indifferently 
named  the  anterior  or  right  cavities  of  the  heart — the  latter  term  being  in  general 
use,  though  the  first  is  much  more  convenient  in  Veterinary  Anatomy. 

Right  Ventricle. — The  right  ventricle  represents  a  hollow  cone,  a 
horizontal  section  of  which  resembles  a  crescent,  its  posterior  plane  being  pushed 
into  the  cavity  by  the  left  ventricle. 


RIGHT   SIDE   OF   THE    HEART   LAID   OPEN, 


1,  Cavity  of  right  auricle ;  2,  appendix  auri- 
culae, with  musculi  pectinati ;  3,  anterior 
vena  cava  opening  into  the  upper  part  of 
the  right  auricle  ;  4,  posterior  vena  cava  ; 
5,  fossa  ovalis,  surrounded  by  the  annulus 
oralis  ;  6,  Eustachian  valve  ;  7,  opening  of 
the  coronary  sinus ;  8,  coronary  valve  ;  9, 
entrance  of  auricular-ventricular  opening. 
a,  Right  ventricle  ;  6,  its  cavity  ;  c,  conus 
arteriosus,  or  infundibulum  ;  d,  pulmonary 
artery  ;  e,  f,  tricuspid  valve  ;  g,  one  of  the 
musculi  papillares  to  which  the  curtains  of 
the  tricuspid  valve  are  attached  by  chordae 
tending  ;  h,  columnse  carneue  ;  i,  two  mus- 
culi papillares  of  valvular  curtain ;  /,  I, 
chord*  tendinese;  m,  .semilunar  valves  of 
pulmonary  artery  ;  n,  apex  of  left  appendix 
auriculae  ;  o,  left  ventricle. 


588  CIRCULATORY  APPARATUS. 

It  offers  hvo  ivalls,  an  apex,  and  a  base. 

Walls. — The  anterior  waU  is  concave  ;  its  thickness  is  more  considerable 
above  than  below,  and  averages  ^^  of  an  inch.  The  posterior  ivall  is  convex,  and 
formed  by  the  septum  ventriculorum. 

Both  walls  are  uneven,  from  the  presence  of  fleshy  columns  (columnce  carnece), 
which  we  will  commence  examining  in  a  general  manner,  as  they  are  found  in 
the  four  compartments  of  the  heart.  They  are  of  three  kinds  :  one  kind,  named 
the  pillars  of  the  heart  {musculi  papiJlares) — thick  and  short,  and  fixed  by  their 
base  to  the  walls  of  the  ventricles — have  a  free  summit,  into  which  are  implanted 
the  tendinous  cords  {chordce  tendincB)  proceeding  from  the  auriculo-ventricular 
valve  ;  those  of  the  second  order  (trabeculce  carnce)  are  free  in  their  middle  part, 
and  attached  by  their  extremities  to  the  walls  of  the  heart  ;  while  the  third 
description  {columned)  adhere  throughout  their  length  to  the  cardiac  tissue,  on 
which  they  stand  as  if  sculptured  in  relief. 

In  the  right  ventricle,  two  columns  of  the  first  order,  rarely  three,  are  met 
with — one  on  the  anterior,  the  other  on  the  posterior  wall.  The  columns  of  the 
second  order  number  two  or  three  principal  ones,  extending  from  one  wall  to  the 
other,  or  attached  to  two  different  points  of  the  same  wall.  There  also  exist  a 
considerable  number  of  small  ones  intermixed  with  those  of  the  third  order. 
The  latter  are  particularly  abundant  in  the  angles  formed  by  the  union  of 
the  two  faces,  where  they  interlace  and  give  rise  to  more  or  less  complicated 
areolae. 

Apex. — The  cipex  of  the  right  ventricle  does  not  descend  to  the  point  of  the 
heart,  being  distant  from  it  about  H  inches. 

Base. — This  has  two  large  orifices — the  auriculo-ventricular  and  the  pidmonary 
openings. 

Auriculo-ventricular  optening. — Placed  on  a  level  with  the  constriction  that 
divides  the  right  heart  into  two  superposed  compartments,  this  orifice — widely 
open  and  almost  a  regular  circle  in  outline — forms  the  communication  between 
the  auricle  and  ventricle.  It  is  provided  with  a  valvular  fold  that  exactly  closes 
the  orifice  when  the  ventricle  contracts  to  propel  the  blood  into  the  lungs,  and 
which  is  termed  the  tricuspid  (having  three  points)  valve,  in  consequence  of 
its  form.  This  valve  offers  :  1.  A  superior  border,  attached  to  the  entire  margin 
of  the  auriculo-ventricular  opening.  2.  An  inferior  opening,  free,  cut  into  three 
festoons  by  three  deep  notches,  and  fi-xed  to  the  ventricular  walls,  principally 
on  the  summits  of  the  fleshy  columns,  by  means  of  the  tendinous  cords  which 
ramify  on  reaching  the  valve.  One  of  these  festoons— more  developed  than  the 
others — is  placed  on  the  limit  of  the  auriculo-ventricular  and  pulmonary 
openings  ;  thereby  constituting  a  kind  of  vertical  partition  that  divides  the 
ventricular  cavity  at  its  base  into  two  compartments — a  right  or  auricular,  and 
a  left  or  arterial.  The  other  festoons  are  apphed  to  the  anterior  and  posterior 
walls  of  the  ventricle.  3.  An  external  face,  which  receives  the  insertion  of  a 
great  number  of  tendinous  cords,  4.  An  internal  face,  which  becomes  superior 
when  the  valve  is  raised  to  close  the  opening,  when  it  constitutes  the  floor  of  the 
auricular  cavity. 

Pulmonary  opening. — This  orifice  represents  the  entrance  of  the  pulmonary 
artery.  Situated  in  front  and  to  the  left  of  the  preceding,  but  a  little  higher,  it 
occupies  the  summit  of  a  kind  of  infundibulum  (the  conus  arteriosus)  formed  by 
the  left  compartment  of  the  ventricle  being  prolonged  upwards.  It  is  perfectly 
circular,  smaller  than  the  artery  to  which  it  gives  origin,  as  well  as  the  auriculo- 


TEE  HEART. 


ventricular  opening,  from  which  it  is  separated  by  a  kind  of  muscular  spur,  to 
which  is  attached  the  principal  festoon  of  the  tricuspid  valve. 

The  pulmonary  opening  is  furnished  with  three  valve^— the  sigmoid  (or  semi- 
lunar), suspended  over  the  entrance  to  the  pulmonary  artery,  and,  as  has  been 
ingeniously  remarked  (by  Winslow),  like  three  pigeons'  nests  joined  in  a  triangle. 
These  valves  are  remarkable  for  their  thinness— a  circumstance  which  does  not 
interfere  with  their  solidity.  They  present  :  an  external,  convex  border,  attached 
to  the  margin  of  the  orifice  and  to  the  walls  of  the  puhnonary  artery  ;  a  free 
border,  straight  when  pulled  tense,  concave  when  left  to  itself,  and  sometimes 
provided  in  its  middle  with  a  small,  very  hard  tubercle,  the  nodule  of  Arantius 
{nodulus,  or  corpus  Arantii)  ;  a  superior,  concave  face  ;  and  an  inferior,  convex 
one.     The  sigmoid  valves  are  raised 

and  applied  to  the  walls  of  the  vessel  ^S'  ^'"'^* 

at  its  entrance,  when  the  ventricle 
contracts  and  sends  the  venous  blood 
into  the  lung.  "When  this  contraction 
ceases,  they  fall  back  one  against  the 
other  by  that  part  of  their  inferior 
face  next  to  their  free  border,  so  as 
to  oppose  the  reflux  of  the  blood  into 
the  ventricular  cavity.^ 

Right  Auricle. — The  cavity  of 
the  right  auricle  represents  a  very 
concave  lid  or  cover  surmounting  the 
auriculo-ventricular  opening,  and  is 
prolonged,  anteriorly,  by  a  cm-ved 
cul-de-sac.  It  offers  for  study  this 
anterior  cul-de-sac,  a, posterior,  external, 
and  internal  wall,  as  well  as  a  superior 
wall  or  roof,  and  the  auricido-ventri- 
cidar  opening,  which  occupies  the 
whole  floor  of  the  cavity.  This  ori- 
fice has  been  already  described. 

The  anterior  cul-de-sac  is  in  the  appendix  auricularis  ;  it  is  divided  by  a  great 
number  of  muscular  columns  of  the  second  and  third  orders  {musculi  pectinati), 
into  deep  and  complex  areolae. 

The  posterior  ivall  responds  to  the  interauricular  septum  ;  it  is  smooth,  and 
usually  marked  by  an  oblique  and  more  or  less  deep  cvl-de-sar  (or  depression), 
the  remains  of  Botal's  foramen.  This  depression  is  surrounded  by  the  ring  (or 
isthmus)  of  Vieussens  (anmdus  oralis),  and  is  named  the  fossa  ovalis ;  it  is  only 
separated  from  the  left  auricular  cavity  by  a  thin  membrane,  a  vestige  of  the 

'  It  has  been  repeated,  ad  nauseam,  that  the  occlusion  of  the  arterial  openings  results  from 
the  juxtaposition  of  the  free  harder  of  the  sigmoid  valves ;  even  the  small  tubercle  in  the 
middle  of  this  border,  has  been  considered  to  play  its  part  in  closing  the  triangular  central 
space  left  when  tliese  valves  meet.  In  passing  the  finger  into  the  pulmonary  artery  of  a  living 
animal,  to  explore  the  function  of  these  membranous  folds,  it  is  readily  perceived  that  they 
come  in  contact  by  a  large  portion  of  their  convex  face,  and  not  alone  by  their  free  border. 
This  arrangement  is  such,  that  we  have  with  much  diflSculty  tried  to  produce  an  insufficiency 
of  contact  by  keeping  one  of  the  valves  up  ngainst  the  walls  of  the  vessel  with  the  finger;  but 
the  others  came  down  against  the  finger  and  applied  themselves  around  it  so  as  to  exactly  close 
the  orifice.  ^ 

40  ..  /-i 


SECTION   OF   THE   HEART   AT   THE   LEVEL  OF   THE 
VALVES. 

p,  Pulmonary    artery;  A,  aorta;  M,  mitral  valve; 
T,  tricuspid  valve. 


590  CIRCULATORY   APPARATUS. 

valve  (Eustachian  valve)  circumscribing  the  interam-icular  opening  in  the 
foetus.^ 

In  the  wall  are  small  orifices  {foramina  Thehesii)  which  lead  to  anastomosing 
vessels  {verice  cordis  minimce)  in  its  substance. 

The  external  ivall  is  areolated,  and  perforated  behind  and  below  by  two 
orifices,  the  largest  of  which  is  the  opening  of  the  posterior  vena  cava,  the  other 
the  opening  of  the  large  coronary  vein.  Both  are  destitute  of  valves,  though 
these  are  found  at  a  short  distance  in  the  coronary  vein.  The  bronchial  vein 
sometimes  opens  separately  beside  the  latter. 

The  internal  wall  is  smooth. 

The  superior  wall,  or  roof  of  the  auricle,  shows  the  openings  of  the  anterior 
vena  cava  and  vena  azygos  ;  the  latter  only  is  provided  with  valves,  which  are, 
however,  not  always  present.  On  this  wall  are  also  remarked,  in  front,  areolae 
separated  by  muscular  columns. 

The  thickness  of  the  right  auricular  walls  is  very  irregular,  in  consequence  of 
the  reliefs  sculptured  on  the  inner  face  of  that  cavity.  In  some  points  it  is 
about  ^  of  an  inch,  and  in  others,  particularly  in  the  small  culs-de-sac  formed 
by  the  reticulations,  it  is  sometimes  so  thin  as  to  appear  exclusively  formed 
by  the  union  of  the  external  and  internal  serous  membrane. 

(When  the  vena  azygos  opens  behind,  there  is  between  it  and  the  orifice  of 
the  anterior  vena  cava,  a  muscular  layer  with  a  free  concave  border,  which  forms 
a  kind  of  valve  of  very  variable  extent.  Behind  this  vena  cava  is  a  thick 
eminence — the  tuberculum  Loweri ;  this  has  the  form  of  a  crescent,  open  in  front, 
and  elongated  from  right  to  left  at  the  superior  border  of  the  septum.  The 
anterior,  or  left  border  of  the  fossa  ovalis,  is  thin  and  prominent,  and  constitutes 
the  Eustachian  valve  ^ — ^a  musculo-membranous  fold  of  a  semilunar  shape,  with  a 
concave  free  border  directed  to  the  right  and  behind.  It  is  of  little  use  in 
animals,  because  of  their  horizontal  position.  Immediately  beneath  the  posterior 
vena  cava,  and  between  it  and  the  coronary  vein,  is  a  small  membranous 
crescent — the  vcdve  of  Thehesius.) 

C.  Red-blood  (or  Aortic)  Heart. — This  is  also  called  the  posterior  heart, 
and  more  frequently  the  left  heart,  because  it  is  situated  behind  and  to  the  left  of 
the  dark-blood  heart.  Its  general  disposition  otherwise  exactly  resembles  that 
of  the  latter  receptacle. 

Left  Ventricle. — This  is  a  cylindro-conical  cavity,  the  transverse  section  of 
which  is  irregularly  circular.  Its  walls  attain  a  thickness  of  from  1-^  to  1|  inches, 
except  towards  the  apex  of  the  heart,  where  they  are  extremely  thin.  They  are 
less  reticulated  than  those  of  the  right  ventricle,  and  exhibit  several  columns  of 
the  second  order,  as  well  as  two  enormous  muscular  pillars — an  external  and 
internal,  for  the  attachment  of  the  tendons  of  the  auriculo-ventricular  valve. 
The  apex  of  the  cavity  forms  a  reticulated  cid-de-sac,  which  occupies  the  point 
of  the  heart.  The  base  is  perforated  by  the  auriculo-ventricular  and  the  aortic 
openings.  The  auricido-ventricidar  opening— i^reckelj  similar  to  that  of  the  right 
ventricle— is  provided  with  a  circular  membrane,  the  mitral  (or  bicuspid)  valve, 
because  it  is  cut  into  several  festoons,  of  which  two  are  the  principal— the  one 

•  Zangger  and  Zundel  have  observed  instances  of  persistent  foramen  ovale  in  Foals,  and 
even  in  Horses.  Goubaux  has  collected  fifteen  cases  of  this  kind,  thirteen  of  which  occurred 
in  Bovines  -aged  from  four  mouths  to  twenty  years— one  in  the  Sheep,  and  another  in  the  Dog. 
This  anatomist  also  met.with  an  abnormal  communication  between  the  two  ventricles  in  an 
adult  Horse.    Chatin  has  studied  a  similar  anomaly  in  a  young  Hemionus. 

'  2  The  presence  of  a  Eustachian  valve  in  the  Horse  has  been  denied.) 


THE  HEART. 


591 


anterior,  the  other  posterior,  simulating  in  their  outline  the  two  faces  of  a 
bishop's  mitre.  The  anterior  festoon  is  the  largest,  and  is  attached  to  the  limit 
of  the  two  orifices,  isolating  from  the  ventricular  cavity  a  diverticulum  which 
corresponds,  in  every  respect,  to  the  pulmonary  infundibulum.  The  posterior 
festoon  is  applied  to  the  walls  of  the  ventricle.  Between  these  two  there  are 
usually  two  secondary  festoons,  making  up  the  total  number  to  four  ;  frequently 
there  is  an  accessory  fold,  situated  on  the  right  side,  and  fairly  developed  ;  the 
valve  is  then  tricuspid,  like  that  of  the  right  ventricle.  Sometimes  two  of  these 
rudimentary  folds  are  found  on  the  left  side — making  five  festoons  in  all.  The 
aortic  opening — so  named  because  it  constitutes  the  origin  of  the  aorta — is  placed 
in  front  and  to  the  left  of  the  auriculo-ventricular  opening,  from  which  it  is  only 
separated  by  a  thin  muscular  spur, 

to  which  is   attached  the  adherent  ^"g-  ^^'^■ 

border  of  the  great  festoon  or  curtain 
of  the  mitral  valve.  It  does  not 
differ  in  anything  from  the  pulmonary 
opening,  and,  like  it,  is  provided  with 
three  sigmoid  (or  semilunar)  valves. 

Left  Auricle. — As  in  the  right 
auricle,  this  forms  a  kind  of  lid  above 
the  auriculo-ventricular  opening. 
Smooth  behind,  in  front,  inwards  and 
outwards,  its  cavity  presents  a  reticu- 
lated cul-de-sac,  which  occupies  the 
auricula  ;  and  a  superior  wall,  also 
reticular,  having  from  four  to  eight 
orifices — the  openings  of  the  pul- 
monary veins.  These  orifices  have 
no  valves.  (Carnece  columnce  of  the 
third  kind  are  also  present,  but  chiefly 
between  the  two  posterior  pillars  ; 
small  ones  are  very  numerous  on  the 
borders  and  summit  of  the  ventricle. 
The  columns  of  the  second  order  are 
simple  or  ramous,  and  pass  from  the 
angles  of  union  of  the  walls  and  the 
point  of  the  cavity ;  others  on  the  posterior  wall  go  to  the  borders  and  the 
interval  between  the  two  pillars.  The  most  remarkable  are  bands  extending  from 
one  wall  to  the  other,  the  two  principal  of  which  are  long,  strong,  and  ramous ; 
they  are  fixed,  on  the  one  side,  to  the  centre  of  the  great  posterior  reliefs,  and 
ascend  to  be  implanted,  on  the  other  side,  into  the  middle  of  the  anterior  wall.) 


LEFT    CAVITIES    OF    HEART    LAID    OPE 

1,  Cavity  of  left  auricle;  2,  cavity  of  appendix 
auriculae ;  3,  opening  of  two  right  pulmonary 
veins  ;  4,  sinus  into  which  left  pulmonary  veins 
open;  5,  left  pulmonary  veins;  6,  auriculo-ven- 
tricular opening ;  7,  coronary  vein  lying  in 
auriculo-ventricular  groove ;  8,  left  ventricle ; 
9,  9,  cavity  of  left  ventricle,  a,  Mitral  valve, 
its  curtains  connected  by  chordae  tending  to  b,  b, 
columnce  carnea; ;  c,  c,  fixed  columneae  carnae  on 
inner  surface  of  ventricle  ;  i,  point  of  appendix  of 
right  auricle. 


4.  Steucture  of  the  Heart. 

Preparation.— Bekre  proceeding  to  dissect  the  muscular  fibres  of  the  heart,  it  is  indis- 
pensable to  keep  that  viscus  in  boiling  water  for  half  or  three  quarters  of  an  hour.  It  should 
then  be  immediately  immersed  in  cold  water,  to  prevent  the  desiccation  of  the  serous  membrane 
covering  it,  and  which  must  be  at  once  removed.  The  furrows  should  then  be  cleared  of  their 
Vessels  and  fat ;  this  renders  the  superficial  muscular  fibres  very  apparent.  The  same  result 
may  be  attained  by  immersing  the  heart  in  vinegar  or  dilute  hydrochloric  acid.  To  isolate  the 
ventricles  and  unitive  fibres  from  each  other,  the  following  procedure  may  be  adopted :  After 
removing  the  auricular  mass  and  dissecting  the  fibrous  rings,  the  unitive  fibres  around  these 


S92  CIRCULATORY  APPARATUS. 

are  divided  with  the  point  of  the  scalpel,  care  being  taken  not  to  injure  the  proper  fibres.  Then, 
with  the  aid  of  the  finger-nail  or  handle  of  the  scalpel,  follow  the  more  or  less  artificial  limit  of 
these  two  series  of  muscular  planes  in  a  spiral  manner ;  the  vessels  passing  thiough  the  walls 
of  the  heart  must  be  cut  through-  The  same  course  is  fullowed  in  the  substance  of  the  inter- 
ventricular septum,  in  order  to  separate  tlie  two  sacs  fiurmed  by  the  proper  fibres. 

(It  will  be  found  that  the  simplest  and  best  way  to  prepare  the  lieart  for  an  examination 
of  its  fibres,  is  to  steep  it  in  a  very  weak  dilution  of  hydrochloric  acid.  Remove  the  serous 
membrane,  and  tlie  fibres  can  then  be  traced,  layer  by  layer,  from  their  origin  to  their 
termination.) 

The  muscular  tissue  composing  the  heart  rests  on  a  fibrous  framework,  dis- 
posed in  rings  around  the  auriculo-ventricular  and  arterial  openings  ;  it  receives 

Fig.  354. 


ArRICULO-VENTRICCLAR   FIBRO-CARTILAGINOUS   RINGS. 

1,  Pulnionary  artery ;  2,  superior  border  of  the  infundibulum ;  3,  aorta ;  4,  sigmoid  or  semilunar 
valves;  5,  bulgings  of  the  aorta  corresponding  to  the  semilunar  valves;  ii,  left  auriclo-ventricular 
opening;  7,  right  ditto  ;  8,  left  fibro-cartilaginous  ring  ;  9,  right  ditto ;  10,  the  two  rings  meeting 
together  in  the  middle  line. 

vessels  and  nerves,  and  while  covered  in  the  internal  cavities  by  two  independent 
serous  membranes,  it  is  enveloped,  externally,  by  another  membrane  of  the  same 
kind.  An  annvlar  frameivork,  muscular  tissue  proper,  vessels  and  nerves,  and 
serous  tunics — such  are  the  elements  entering  into  the  structure  of  the  heart. 

A.  Fibrous  Rings,  or  Tendinous  Rings  of  Lower. — These  are  also 
named  the  fibrous  zones  of  the  heart,  and  are  four  in  number  :  one  for  each  of 
the  openings  at  the  base  of  the  ventricles. 

The  two  arterial  zones  (the  pulmonary  and  aortic)  constitute  two  complete 
rings,  which  are  not  disposed  in  a  circular  manner  around  the  pulmonary  aortic 
openings,  but  are  divided  into  three  regular  festoons  with  their  concavities 


THE  HEART.  593 

superior  and  internal,  and  corresponds  to  the  insertions  of  the  three  sigmoid 
valves.  These  zones  are  continuous,  by  their  superior  and  external  contour,  with 
the  walls  of  the  arteries,  from  which  they  are  only  distinguished  by  their  whitish- 
grey  colour  and  slight  elasticity,  the  arterial  tissue  being  yellow  and  very  elastic. 
Their  internal  and  inferior  outline  sends  three  thin  prolongations  into  the  serous 
duplicatures  of  the  sigmoid  valves. 

The  auriculo-ventrkular  zones  do  not  completely  suiTound  the  openings  they 
circumscribe.  They  are  flat,  brilliantly  white  tendons,  laid  one  against  the  other 
at  the  ventricular  septum,  and  against  the  aortic  ring  ;  they  turn  to  the  right 
and  left  around  the  auriculo-ventricular  openings,  but  without  joining  at  their 
extremities,  which  are  dispersed  as  fibrillse  in  the  muscular  tissue  of  the  ventricles. 
Above,  these  zones  give  attachment  to  the  muscular  fibres  of  the  auricles  ;  below, 
to  the  ventricular  fasciculi.  Their  internal  and  inferior  border  is  prolonged  into 
the  mitral  and  tricuspid  valves,  and  is  continuous,  through  these  valves,  with  the 
chordae  tendinete  of  the  ventricles.  Some  of  these  cords,  generally  the  strongest, 
are  even  directly  inserted  into  the  auriculo-ventricular  zones. 

It  must  be  noted  that,  in  Solipeds,  there  is  constantly  found,  at  the  point 
where  the  aortic  and  auriculo-ventricular  zones  lie  against  each  other,  a  more  or 
less  developed  cartilaginous  body,  which,  in  the  larger  Ruminants,  is  transformed 
into  true  bone.  (Lavocat  speaks  of  two  cartilaginous  points,  one  to  the  right,  at 
the  junction  of  the  aortic  with  the  left  auriculo-ventricular  ring  and  the  cardiac 
septum  ;  the  other,  less  developed,  on  the  left,  at  the  origin  of  the  left  ventricular 
groove.) 

B.  Muscular  Tissue  (Fig,  355). — The  muscular  tissue  of  the  heart  is  that  of 
organic  life,  as  it  contracts  independently  of  the  will.  Nevertheless,  it  is  formed  of 
red  striped  fibres,  which  differ  from  the  striped  muscles  of  the  locomotory  apparatus. 
They  are  granular  and  dark  under  the  microscope,  and  ramify  and  anastomose  in 
such  a  manner  as  to  form  an  extremely  fine  network  in  the  myocardium.  From 
the  joining  end  to  end  of  the  segments  of  Weissmann,  there  result  simple  or 
ramified  prisms,  the  bases  of  which  are  notched  like  stairs.  Each  Weissmann 
segment  comprises  :  1.  In  the  centre,  one  or  two  nuclei  with  a  nucleolus.  2.  Con- 
tractile cylinders  of  unequal  length,  around  the  nuclei.  3.  A  mass  of  protoplasm 
enveloping  the  nucleus,  extending  'between  the  contractile  cyHnders,  and  forming 
a  kind  of  sarcolemma.  Between  the  fibres  of  the  myocardium  there  is  very  little 
connective  tissue,  but  there  is  a  great  number  of  blood-vessels  and  lymphatics. 

The  arrangement  of  the  muscular  fasciculi  of  the  heart  has  been  the  object 
of  numerous  investigations,  which  have  only  complicated  what  was  already 
known  on  the  subject.  We  will  endeavour  to  sum  up,  as  simply  as  possible,  this 
arrangement,  in  examining  it  successively  in  the  ventricles  and  auricles. 

1.  Fibres  of  the  Ventricles. — According  to  the  remark  of  Winslow,  we 
may  compare  the  ventricles,  in  regard  to  the  arrangement  of  the  fibres  composing 
them,  to  "  two  muscular  sacs  included  in  a  third  ;  "  that  is  to  say,  each  ventricle 
is  formed  oi  proper  muscular  fibres,  covered  externally  by  a  layer  of  unitive  fibres, 
which  envelop  the  two  ventricles  in  common. 

a.  Proper  fibres  of  the  ventricles. — Taken  altogether,  these  fibres  represent, 
for  each  cavity,  a  hollow  cone,  open  at  both  its  extremities — at  the  superior 
extremity,  by  the  auriculo-ventricular  and  arterial  openings  ;  and  at  the  inferior 
extremity,  by  an  aperture  which  admits  the  reflected  fibres  of  the  common  layer. 
All  form  loops,  attached  by  their  extremities  to  the  outline  of  the  superior 
orifices,  on  the  fibrous  zones,  and  are  rolled,  more  or  less  obliquely,  around  the 


591  CIRCULATORY  APPARATUS. 

axis  of  the  ventricles.     It  is  from  the  apposition  of  the  right  and  left  systems 
that  the  ventricular  septum  is  formed. 

b.  Unitive  fibres  of  the  ventricles. — These  are  disposed  as  an  external  shell 
enveloping  the  proper  fibres.  They  leave  the  fibrous  zones  at  the  base  of  the 
heart,  and  descend  towards  its  apex  :  those  of  the  right  side,  by  inclining 
forward ;  the  anterior,  in  following  the  direction  of  the  great  axis  of  the 
ventricles ;  those  of  the  left  face,  by  directing  their  course  downwards  and 
backwards ;  and  the  posterior,  in  roUing  themselves  from  left  to  right  around 
the  left  ventricle.  On  arriving  near  the  point  of  the  heart,  they  turn  from  left 
to  right,  and  before  to  behind,  in  forming  a  spiral  twist ;  then  they  are  reflected 
from  below  upwards,  to  enter  the  inferior  extremity  of  the  ventricles,  on  the 
internal  face  of  the  proper  fibres  of  which  they  spread  and  ascend  to  the  fibrous 
zones  at  the  base  of  the  heart,  where  they  terminate.  Some  of  these  reflected 
fibres  are  disposed  in  relief,  to  constitute  the  columnse  carnese,  and  reach  the 

Fig.  356. 
Fig.  355. 


ANASTOMOSING     MUS- 
CULAR    FIBRES    OP  MUSCULAR   WHORL   AT   THE    POINT    OF   THE 
HEART.  HEART. 

1,  Vortex  or  whorl  with  small  opening  in  the 
middle;  2,  auricle;  3,  intercrossing  of  the 
anterior  and  posterior  unitive  or  uniting 
fibres. 

auriculo-ventricular  zones  through  the  medium  of  the  chordfe  tending  that 
directly  connect  these  fibrous  rings  with  the  summits  of  the  muscular  pillars. 

All  the  fibres  do  not  reach  the  point  of  the  heart  to  ascend  to  the  fibrous 
zones  ;  a  certain  number  are  reflected  at  different  heights  in  the  layer  they  form, 
and  Gerdy  has  compared  them  to  a  number  of  horns  placed  one  within  the 
other,  and  flattened  as  are  the  walls  of  the  ventricles. 

Such  is  the  general  disposition  of  the  unitive  fibres  of  the  ventricles  :  and  it 
will  be  seen  that  they  form  a  superficial  and  a  deep  or  reflected  plane,  between 
which  are  comprised  the  fasciculi  proper  to  each  ventricular  cavity. 

The  unitive  fibres  of  the  ventricles,  therefore,  form  collectively  a  kind  of 
figure  8,  the  smallest  loop  of  which  is  at  the  point  of  the  heart ;  there  the  fibres 
are  heaped  together,  leaving  in  the  centre  of  the  loop  a  very  small  space,  through 
which  it  is  possible  to  pass  a  probe  into  the  ventricle,  without  piercing  anything 
but  the  external  and  internal  serous  membranes  of  the  organ. 

2.  Fibres  of  the  Auricles. — The  fibres  of  the  auricles  are  either  common 
to  the  two  cavities,  or  proper  to  each. 


THE  HEART. 


595 


The  unitive  fibres  constitute  two  thin  bands — a  right  and  left,  caiTied  from 
one  auricle  to  the  other. 

The  proper  fibres  are  divided  into  several  fasciculi,  some  of  which  are  arranged 
in  rings  around  the  auriculo- ventricular  opening  ;  others  in  interwoven  loops ; 
and  others,  again,  in  sphincters,  which  suiTound  the  entrance  of  the  veins. 

These  fibres  are  arranged  in  such  a  manner  that,  in  contracting,  they  diminish 
the  auricles  by  their  superior  and  lateral  planes  and  extremities,  and  propel  the 
blood  towards  the  auriculo-ventricular  openings. 

(The  arrangement  of  the  muscular  fibres  constitutes  the  most  remarkable 

Fig.  357. 


POSTERIOR   UNITIVE   FIBRES,   AND   FIBRES   OF   THE   POSTERIOR   FACE   OF   THE   AURICLES, 

1,  Posterior  unitive  fibres;  2,  fibres  of  the  right  auricle;  3,  fibres  of  the  posterior  vena  cava. 


feature  in  the  anatomy  of  the  heart.  We  have  seen  that  the  auricles,  as  well  as 
the  ventricles,  possess  not  only  fibres  proper  to  each  compartment,  but  also 
unitive  or  common  fibres,  which  assure  the  simultaneousness  in  action  of  the 
similar  or  homologous  cavities.  Besides,  the  fibres  of  the  auricles  and  those  of 
the  ventricles  are  distinct,  and  not  continuous  ;  so  that,  from  their  independence 
of  each  other,  it  results  that  these  two  sections  of  the  heart  may  act  separately, 
and  contract,  not  simultaneously,  but  alternately — a  condition  indispensable  to 


596  CIRCULATORY  APPARATUS. 

the  free  course  .of  the  blood.  The  extremely  fine  and  close  connective  tissue 
uniting  the  muscular  fibres,  and  the  anastomosing  of  these,  is  another  pecuharity 
of  structure  that  must  be  favourable  to  the  solidarity  of  their  action,  which 
ought  to  be  simultaneous.  In  the  healthy  organ,  adipose  tissue  is  only  found  ir. 
tlie  grooves  on  its  surface,  around  the  vessels  lodged  in  them,  and  particularly  at 
its  base,  between  the  large  arterial  trunks.) 

C.  Vessels  and  Nerves  of  the  Heart. — Blood  is  carried  to  the  muscular 
tissue  of  the  heart  by  two  large  vessels — the  coronary  arteries.  They  emanate 
from  the  trunk  of  the  aorta,  at  the  sigmoid  valves,  and  each  divides  into  two 
principal  branches — one  passing  along  the  horizontal,  the  other  in  the  vertical 
furrow  of  the  heart.  Collectively,  these  arteries  form  two  circles,  which  surround 
the  heart  in  intersecting  it  at  a  right  angle  in  the  auriculo-ventricular  groove. 

The  blood  is  carried  from  the  walls  of  the  heart  by  a  single  but  important 
vein.,  which  empties  itself  into  the  right  auricle. 

The  li/mjjhatics  follow  the  arteries,  passing  along  the  visceral  layer  of  the 
pericardium,  and  entering  the  cluster  of  glands  situated  near  the  base  of  the 
heart.  (The  epicardium,  as  well  as  the  endocardium — especially  in  the  ventricles — 
has  a  large  network  of  fine  lymphatics,  the  walls  of  which  consist  of  only  a 
single  layer  of  intimately  adhering  cells.  Lymphatics  are  also  numerous  in  the 
myocardium,  and  amongst  the  muscular  fibres  there  are  lacunae  or  spaces  lined 
by  endothelial  cells — the  origins  of  the  lymphatics.  The  lymph  passes  into 
lymphatic  glands  lying  between  the  aorta  and  trachea,  flowing  thence  into  the 
thoracic  duct.  No  lymphatic  vessels  have  been  traced  upon  the  chordge  tendineaj, 
and  very  few  upon  the  auriculo-ventricular  and  semilunar  valves.) 

The  nerves  of  the  heart,  furnished  by  the  cardiac  plexus,  come  from  the 
pneumogastric  and  sympathetic.  The  tubes  are  small,  and  show  some  cells  in 
their  course.  In  addition  to  these,  the  heart  is  provided  with  a  particular 
ganglionic  system,  to  which  Remak,  Bidder,  and  Ludwig  have  called  attention. 
It  is  believed  that  there  exist  three  ganglia  in  different  points  of  the  cardiac 
parietes,  and  that  on  these  depend  the  movements  of  the  organ.  (Nerve-cells  are 
most  numerous  in  the  basal  and  middle  parts  of  the  ventricles  of  the  heart  of  the 
Dog,  Sheep,  Calf,  and  Pig,  chiefly  in  the  anterior  and  posterior  inter-ventricular 
grooves  and  on  the  left  ventricle.  According  to  Carpenter,  the  nerves  of  the 
heart  are  :  1.  Minute  ganglia  and  fibres  of  the  sympathetic,  situated  in  the  walls 
of  the  cavities,  and  especially  in  the  auriculo-ventricular  furrow.  2.  Fibres  derived 
from  the  cervical  portion  of  the  sympathetic,  and  passing  to  the  cardiac  plexus, 
between  the  aorta  and  pulmonary  artery.  3.  Cerebro-spinal  fibres  entering  the 
inferior  cervical  or  stellate  ganglion,  and  proceeding  to  the  same  plexus,  and 
probably  derived  from  a  centre  situated  in  the  brain  and  spinal  cord.  4.  Fibres 
coursing  in  the  vagus — nervi  cardiaci — and  originating  in  a  centre  situated  in 
the  medulla  oblongata.  The  first  three  of  these  ganglia  and  fibres  probably 
collectively  constitute  the  excito-motor  system  of  the  heart ;  the  fourth  is  an 
inhibitory,  restraining,  or  regulo-motor  centre.) 

D.  Serous  Membranes  of  the  Heart. — These  are  three  in  number — two 
internal,  or  endocardial,  one  of  which  occupies  the  right,  the  other  the  left  cavity  ; 
and  an  external — epicardial — a  dependency  of  the  fibro-serous  sac  which  contains 
the  heart. 

1.  Internal  serous  membranes^  or  endocardia. — These  two  membranes,  indepen- 
dent, like  the  cavities  they  line,  are  spread  over  the  auricular  and  ventricular 
walls,  covering  the  tendinous  or  muscular  columns  attached  to  these  walls,  and 


THE  HEART. 


597 


Fig.  358. 


are  prolonged  into  the  veins  and  arteries,  to  form  the  internal  tunic  of  these 
vessels.  At  the  auriculo-ventricular  and  arterial  openings,  they  constitute  a 
duplicature  for  the  valves  situated  there.  These  valves  'are,  therefore,  due  to  the 
projection  of  a  circular  fold  of  the  endocardium,  between  the  two  layers  of  which  is 
connective  tissue  mixed  with  elastic  fibres  in  the  auriculo-ventricular  valves,  and 
a  layer  of  connective  tissue  on  each  surface  of  the  elastic  fibres  in  the  semilunar 
valves.  It  is  worthy  of  remark  that  the  elastic  fibres  of  the  valves  are  more 
abundant  in  the  left  than  the  right  side  of  the  heart. 

The  endocardium  of  the  right  heart  has  a  red  tint,  which  is  deepest  in  the 
ventricle.  In  the  left  heart,  this  tint  is  slightly  yellow,  especially  in  the  walls  of 
the  auricle,  which  may  be  attributed  to  the  presence  of  a 
thin  layer  of  yellow  elastic  tissue  that  covers  the  adherent 
face  of  the  membrane. 

The  endocardium  consists  of  two  layers  :  1.  A  thin  bed 
of  connective  tissue,  connecting  it  to  the  muscular  structure, 
in  which  elastic  fibres  are  pretty  uniformly  distributed,  as 
well  as  smooth  muscular  fibres,  especially  in  the  left  heart. 
2.  An  endothehum,  consisting  of  a  single  or  double  layer 
of  somewhat  elongated,  polygonal,  tesselated  nucleated  cells. 

2.  External  serous  membrane  (epicardium). — This  is  the 
visceral  lining  membrane  of  the  pericardium,  the  description 
of  which  follows 

5.  The  Peeicardium  (Fig.  255,  c). 

Preparation. — Place  the  auiinal  in  the  second  position,  and  remove 
the  sternal  ribs  by  separating  the  cartilages  and  luxating  their  costo- 
vertebral articulations.  This  procedure  permits  the  study  of  the 
situation  and  general  disposition  of  the  heart  and  pericardium.  But 
in  order  more  easily  to  examine  therecijirocal  arrangement  of  these  two 
parts,  it  is  necessary  to  extract  them  from  the  thoracic  cavity  by  tearing 
through  the  sternal  insertion  of  the  pericardium. 

The  pericardium,  or  proper  serous  covering  of  the  heart,  is  a  membranous  sac 
enclosing  that  organ,  fixing  it  in  ihe  thoracic  cavity,  and  favouring  its  movements 
by  its  pohshed  surface. 

This  sac  is  formed  by  a  fibrous  layer,  within  which  is  spread  a  serous 
membrane,  divided  into  two  parts — one  parietal,  the  other  visceral. 

The  fibrous  layer  of  the  pericardium  presents  somewhat  the  general  form  of 
the  heart.  Its  internal  surface  is  covered  by  the  parietal  portion  of  the  serous 
membrane.  The  external  surface  corresponds  to  the  two  layers  of  the  mediastinum. 
Its  summit  (or  apex),  depressed  on  each  side,  and  elongated  from  before  to  behind, 
is  firmly  attached  to  the  superior  face  of  the  sternum,  from  the  fourth  rib  to  the 
origin  of  the  xiphoid  cartilage.  By  its  base,  it  is  fixed  to  the  large  vessels  going 
to  and  leaving  the  heart,  where  it  is  continuous  with  their  connective-tissue 
sheath,  and  where  it  sends  some  fibres  to  the  longus  colli. 

The  serous  membraiie  of  the  'pericardium  has  been  well  compared  by  Bichat  to 
a  cotton  nightcap,  the  external  part  of  which  would  represent  the  parietal  layer, 
and  the  inverted  part  the  visceral  portion  of  the  membrane.  The  parietcd  layer 
adheres  in  the  most  intimate  manner  to  the  internal  face  of  the  fibrous  tunic, 
and  is  reflected  to  form  the  visceral  portion,  around  the  pulmonary  arteries  and 
the  aorta  for  a  certain  distance  from  their  origin,  and  on  the  pulmonaiy  veins. 
The  viscercd  layer  envelops  in  common  the  two  arterial  trunks,  covers  a  small 


EPITHELIUM     OF    THE 
ENDOCARDIUM. 

1,  Nucleated  cells  hs- 
suming  the  fusiform 
figure;  2,  polygonal 
nucleated  cells. 


598  CIRCULATORY  APPARATUS. 

part  of  the  venae  cavas — particularly  the  anterior — spreads  over  the  insertion  of  the 
pulmonary  veins,  and  then  descends  on  the  auricles  and  ventricles.  The  free  face 
of  this  layer  is  in  contact  with  that  of  the  parietal  layer  ;  the  adherent  face  is 
applied  to  the  tissue  of  the  heart  or  that  of  the  large  vascular  trunks,  except  at 
the  horizontal  and  vertical  grooves,  where  it  rests  on  the  coronary  vessels,  and  on 
the  mass  of  adipose  tissue  constantly  accumulated  on  their  track. 

In  the  living  animal,  the  cavity  of  the  pericardium  is  never  entirely  filled  by 
the  heart,  so  that  the  movements  of  that  organ  are  allowed  much  more  liberty. 
Othenvise,  as  it  does  not  contain  any  gas,  nor  a  sensible  proportion  of  fluid,^ 
its  walls  are  immediately  applied  to  the  surface  of  the  heart. 

The  two  layers  of  the  pericardium  are  covered  by  a  layer  of  endothelial 
polygonal  cells. 

Blood  reaches  the  pericardium  by  the  mediastinal  arteries.  Its  walls  receive 
some  sympathetic  nerve-fibres. 

(The  epicardium  is  composed  of  a  fine  network  of  connective  tissue  and  elastic 
fibres,  as  well  as  bundles  of  non-striped  muscular  fibres  ;  these  resist  the  distension 
that  occurs  when  the  heart  contracts  and  a  great  strain  is  thrown  upon  the 
endocardium.  Gurlt,  in  1867,  described  a  thin  muscle,  niue  inches  long,  situated 
between  the  pericardium  and  the  diaphragm  of  the  Horse.) 

6.  Action  of  the  Heart. 

The  function  of  the  heart  is  to  maintain  the  circulation  of  the  blood,  by  the 
rhythmical  contractions  of  its  two  cavities.  The  right  side  propels  that  fluid 
to  the  lungs,  whence  it  returns  to  the  left  side,  and  from  this  it  is  thrown  into 
all  parts  of  the  body,  after  which  it  is  brought  back  again  to  the  right  heart. 
These  contractions  take  place  simultaneously  in  the  two  cardiac  compartments. 

In  taking  the  heart  at  the  moment  when  it  is  in  a  state  of  repose — that 
is,  in  the  intervals  between  the  two  contractions — we  find  that  its  two  pouches 
are  being  rapidly  filled  with  the  blood  brought  to  it  by  the  veins.  When  suffi- 
ciently replete,  the  auricles  slightly  contract  and  push  a  portion  of  the  fluid  they 
contain  into  the  ventricles — these  contracting  irumediately  after,  to  propel  the 
blood  into  the  arteries.  This  passage  of  the  blood  into  the  arteries  is  a  necessary 
consequence  of  the  contraction  of  the  ventricles,  as  at  the  moment  when  this 
occurs  the  auriculo-ventricular  valves  are  raised,  and  so  prevent  the  reflux  of 
the  blood  into  the  auricles.  This  fluid  is  then  forced  to  enter  the  arterial  orifices, 
the  valves  of  which  are  separated  under  the  impulsive  effort  communicated  to 
the  column  of  blood.  When  the  heart  returns  to  a  state  of  repose,  these  valves 
fall  down,  preventing  the  return  of  the  blood  into  the  ventricles  ;  while  the 
mitral  and  tricuspid  valves  subside  against  the  walls  of  these  cavities,  and  thus 
again  allow  the  passage  of  blood  through  the  auriculo-ventricular  openings. 

By  the  term  systole  is  designated  the  contraction  of  the  heart's  cavities,  and 
by  diastole,  the  repose  or  relaxation  of  its  tissue.  For  each  revolution  of  the 
heart  there  is,  therefore  :  1.  The  gmieral  diastole  of  the  organ,  during  which  the 
two  cardiac  cavities  are  filled  by  the  afflux  of  venous  blood.     2.  The  systole  of 

'  With  Horses  in  health,  the  fluid  exhaled  into  the  pericardium  is  barely  sufficient  to 
moisten  and  lubrify  the  free  surface  of  its  serous  membrane.  But  in  those  worn  out  and 
enfeebled  by  age,  privations,  or  disease,  it  is  not  rare  to  see  it  accumulated  in  greater  or  less 
quantity.  To  verify  this,  however,  an  examination  ought  to  take  place  immediately  after 
death,  as  tlie  accumulation  of  fluid  in  the  serous  cavities  by  cadaveric  exhalation  is  common  in 
all  animals. 


THE  HEART. 


599 


the  auricles,  the  effect  of  which  is  the  repletion  of  the  ventricles.  3.  The  systole 
of  the  ventricles,  propelling  the  blood  into  the  arterial  systems  ;  after  which 
comes  another  period  of  general  diastole. 


Differential  Characteks  in  the  Heart  of  the  other  Animals. 

In  the  Ox,  Sheep,  and  Goat,  the  ventricular  mass  of  the  heart  is  more  regularly  conical 
than  in  Solipeds;  it  has  three  longitudinal  grooves,  one  of  which  is  accessory  and  passes 
behind  the  (left)  ventricle. 

In  the  Ox  two  small  bones,  named  cardiac  bones,  are  found  in  the  substance  of  the  aortic 
zone.  The  largest  is  in  the  right  side,  at  the  point  where  the  arterial  ring  is  approximated  to 
the  auriculo- ventricular  zones;  the  other,  situated  in  the  left,  is  perhaps  not  constantly 
present.  The  first  is  triangular  in  shape,  curved  to  the  right,  and  its  base  is  directed 
upwards.  The  right  face  lies  against  the  auriculo-ventricular  opening;  the  left  is  covered  by 
the  walls  of  the  aorta  at  its  commencement.  It  is  about  an  inch  in  length.  (The  Ox's  heart 
averages  from  about  3^  to  4^  lbs. ;  that  of  the  Sheep,  from  5J  to  7  oz.  It  is  more  elongated  and 
pointed  in  Ruminants  than  in  the  Horse  or  Pig.  The  large  bone  in  the  Ox's  heart  is  elongated 
from  before  to  behind,  flattened  laterally  and  curved  to  the  left;  its  surface  is  roughened,  and 
its  lengtii  is  sometimes  about  2  inches. 


The  left,  or  small  bone,  is  usually  flat- 
tened on  each  side  and  triangular,  one 
of  its  points  is  directed  forwards,  another 
backward,  and  a  third  inferioriy;  its 
length  is  about  three-quarters  of  an 
inch  when  fully  developed.  Besides  the 
Ox,  a  small  cross-shapeil  bone  is  found 
in  the  heart  of  the  Sheep,  Pig,  Camel, 
Deer,  Giraffe,  and  sometimes  in  the 
Horse.  Remak  found  in  the  pericar- 
dium of  the  Ox,  at  the  border  of  the 
left  auricle,  a  row  of  villi  similar  to  those 
discovered  in  the  border  of  the  chicken's 
heart.) 

The  heart  of  the  Pig  resembles  that 
of  the  Horse;  its  direction  is  a  little 
more  oblique,  and  the  pericardium  is 
fixed  to  the  sternum  from  the  third  rib 
to  the  xiphoid  appendix,  as  well  as  to 
the  diaphragm.  (The  cartilage  is  not 
ossified  until  a  late  period.) 

In  the  Dog  and  Cat,  the  heart  is 
ovoid  or  nearly  globular.  It  rests  al- 
most entirely  on  the  upper  face  of  the 
sternum  ;  its  anterior  face  has  become 
the  inferior,  and  its  point,  directed 
backwards,  touches  the  anterior  surface 
of  the  diaphragm.  The  pericardium  is 
attached  to  the  aponeurotic  centre  of  the 
diaphragm. 

Comparison  of  the  Heart  of  Man 
with  that  of  Animals. 


Fig  35<^ 


HUMAN   LUNGS   AND   HEART   (FRONT   VIEW). 

1,  Right  ventricle;  2,  left  ventricle;  3,  right  auricle; 
4,  left  auricle ;  5,  pulmonary  artery ;  6,  right 
pulmonary  artery ;  7,  left  pulmonary  arteiy ;  8, 
ligament  of  ductus  arteriosus;  9,  arch  of  aorta; 
10,  superior  vena  cava;  11,  arteria  innominata;  12, 
right  subclavian  vein,  with  the  artery  behind  it ; 
13,  right  common  carotid  artery  and  vein;  14,  left 
vena  innominata;  15,  left  carotid  artery  and  vein; 
16,  left  subclavian  vein  and  artery ;  17,  trachea ; 
18,  right  bronchus ;  19,  left  bronchus ;  20,  20, 
pulmonary  veins;  21,  superior  lobe  of  right  lung; 
22,  middle  lobe ;  2.S,  inferior  lobe ,  24,  superior  lobe 
of  left  lung  ;  25,  inferior  lobe. 


Tho  human  heart  is  ovoid,  and 
similar  to  that  of  Carnivora ;  the  ventri- 
cular mass  is  not  acute  at  its  apex,  as  in  Solipeds  and  Ruminants.  Its  direction  is  modified 
in  consequence  of  the  antero-posterior  flattening  of  tlie  chest.  It  is  situated  across  the  median 
plane  of  the  thorax ;  its  right  face  in  animals  has  become  the  anterior  face  in  Man,  and  is 
applied  to  the  sternum ;  the  anterior  border  is  in  him  the  right  border,  and  the  posterior  the 
left  border. 

The  organ  is  suspended  obliquely  downwards,  forwards,  and  to  the  left ;  consequently,  the 
right  auricle  is  to  the  right  of  the  sternum,  between  the  third  and  fourth  ribs,  and  the  point 


600  TEE  ARTERIES. 

on  a  level  with  the  sixth  left  intercostal  space.  The  auricular  appendages,  particularly  the 
right,  are  more  rounded  and  bulging  than  in  animals.  The  pulmonary  veins,  four  in  number, 
open  on  the  upper  face  of  the  left  auricle. 

There  are  no  essential  differences  to  be  noted  in  its  internal  conformation.  We  may  indi- 
cate the  presence  of  a  fold  that  passes  from  the  ring  of  Vieussens  to  the  opening  of  the  inferior 
vena  cava ;  this  is  tlie  Eustachian  valve.  We  may  also  mention  the  Thebesian  valve  at  the 
entrance  of  tlie  coronary  vein. 

The  fibrous  rings  and  muscular  fasciculi  are  disposed  as  in  the  Horse. 

The  pericardium  is  a  conical  sac ;  but  instead  of  its  base  being  presented  upwards,  it  rests 
against  the  tendinous  centre  of  the  diapliragm;  its  summit  is  lost  among  the  large  vessels; 
and  it  adheres  to  the  posterior  face  of  the  sternum. 


SECOND  SECTION. 
The  Arteries. 

CHAPTER  I. 
GENERAL    CONSIDERATIONS. 


Definition. — The  centrifugal  vessels  which  carry  the  blood  from  the  heart  to 
the  various  organs,  are  named  arteries. 

Division. — These  vessels  proceed  from  the  heart  by  two  trunks,  wluch  are 
perfectly  independent  in  the  adult  animal ;  they  originate,  one  in  the  right 
ventricle,  the  other  in  the  left. 

The  first  of  these  trunks — which  carries  the  dark  blood — is  the  pulmonary 
artery.  The  second  conveys  the  red  blood,  and  is  named  the  aorta.  There 
exist,  therefore,  two  groups  of  arteries — the  pulmonary  system,  and  the  aortic 
system. 

General  Form. — Single  at  their  origin,  the  two  arterial  systems  soon 
divide  into  less  voluminous  trunks,  which  again  subdivide  into  successively 
decreasing  canals,  until  at  last  their  diameter  becomes  reduced  to  an  extreme 
degree  of  tenuity.  In  a  word,  the  arterial  trunks  present  the  ramous  disposition 
of  dicotyledonous  plants.  The  total  volume  of  the  secondary  trunks  exceeds 
that  of  the  primary  trunk,  and  the  same  relation  exists  between  the  respective 
dimensions  of  the  branches  and  their  ramifications,  to  the  ultimate  divisions  of 
the  artery.  In  tracing  all  the  ramifications  of  one  of  these  systems  to  a  single 
canal,  it  will  be  found  that  this  canal  is  incessantly  increasing,  from  its  origin 
to  its  termination,  and  that  it  represents  a  hollow  cone  with  its  apex  at  the 
heart.  ^ 

Particular  Form. — Each  artery  is  cylindrical  in  form,  whatever  its  volume 
may  be.     When  the  diameter  of  these  vessels  is  measured  at  their  origin  and 

'  Berryer-Fontaine  agaiij  discusses  this  arrangement,  and  asserts  that  it  is  imaginary. 
According  to  his  calculations,  the  arterial  blood  in  Man  circulates  in  a  cylinder,  and  not  in  a 
cone.  The  measurements  and  the  calculations  we  have  made  with  ngard  to  the  arteries  of 
Solipeds,  have  demonstrated  once  more  that  the  volume  of  the  terminal  branches  of  an  artery 
Is  greater  than  that  of  the  latter.     Consequently,  we  adhere  to  the  old  belief. 


GENERAL   CONSIDERATIONS.  601 

their  termination,  between  two  collateral  branches,  no  sensible  difference  is 
perceived. 

Mode  of  Origin. — The  arteries  are  detached  in  &n  angular  manner  from 
the  parent  branches.  Sometimes  the  angle  of  separation  is  more  or  less  acute — 
this  is  most  frequently  the  case  ;  sometimes  it  is  at  a  right  angle,  and  at  other 
times  it  is  obtuse.  It  will  be  readily  understood  that  the  degree  of  this  angle 
exercises  a  somewhat  marked  influence  on  the  course  of  the  blood.  For  example, 
the  blood  from  a  principal  vessel,  in  passing  into  the  canal  of  a  secondary  one 
which  springs  from  it  at  an  obtuse  angle,  must  experience  a  notable  check  in  its 
impetus,  because  of  the  change  in  direction  it  has  to  encounter  ;  on  the  contrary, 
the  rapidity  of  the  current  is  not  modified  to  any  appreciable  degree  in  those 
vessels  which  separate  from  them  at  a  very  acute  angle.  Towards  the  point  of 
separation,  there  is  always  remarked,  in  the  interior  of  the  vessel,  a  kind  of  spur, 
the  sharp  border  of  which  is  towards  the  heart — thus  dividing  the  current  of 
blood  and  diminishing  the  resistance.  This  spur  resembles  in  its  arrangement 
the  pier  of  a  bridge,  against  which  the  waters  are  divided  to  pass  on  each  side. 
(When  a  short  trunk  divides  abruptly  into  several  branches,  proceeding  in 
different  directions,  it  is  termed  an  axis.  A  very  peculiar  feature  in  the  division 
of  arteries,  however,  and  one  which  will  be  made  amply  conspicuous  in  the 
following  description,  is  their  bifurcation  or  dichotoraous  arrangement,  which 
prevails  so  largely.) 

Course. — In  the  course  pursued  by  an  artery,  it  is  necessary  to  consider  the 
situation  occupied  by  the  vessel,  its  direction,  relations,  and  the  anastomoses  which 
establish  communication  between  it  and  the  neighbouring  vessels. 

Situation. — The  arteries  tend  constantly  to  recede  from  the  superficial  parts, 
and  to  become  lodged  in  the  deeper  regions  ;  in  this  way  they  are  I'emoved  from  the 
hurtful  action  of  external  causes — a  tendency  all  the  more  marked  as  the  arteries 
are  more  considerable  in  volume,  but  which  ceases  to  be  manifested  in  the  less 
important  ramuscules.  These  vessels,  therefore,  occupy  either  the  great  cavities 
of  the  trunk,  or  the  deep  interstices  on  the  internal  face  of  the  limbs  ;  when  they 
pass  over  an  articulation,  it  is  always  on  the  side  at  which  flexion  occurs.  But 
in  the  limbs,  for  instance,  the  joints  are  flexed  alternately  in  opposite  directions, 
and  it  then  happens  that  the  arteries  in  these  regions  have  a  slightly  helicoid  (or 
spiral)  arrangement.  This  is  evident  in  the  case  of  the  femoral  artery,  which 
passes  round  the  inner  face  of  the  femur  to  become  the  popliteal  artery  ;  and 
also  in  the  humeral  artery,  which  is  at  first  situated  on  the  inner  side  of  the 
scapulo-humeral  articulation,  then  winds  around  the  humerus  to  be  placed  in 
front  of  the  elbow-joint. 

Direction. — The  arteries  are  sometimes  rectilinear,  and  at  other  times  more 
or  less  flexuous.  The  latter  disposition  is  evidently  intended  to  prevent  lacera- 
tion of  the  vessels  in  organs  capable  of  elongation  and  contraction,  as  may  be 
remarked  in  the  tongue  ;  or  to  moderate  the  impetus  of  the  blood,  as  in  the 
internal  carotid  arteries. 

Relations. — In  their  course,  the  arteries  may  be  in  contact  with  the  viscera, 
nerves,  muscles,  bones,  skin,  and  connective  tissue. 

a.  In  nearly  every  part  of  the  body,  the  arteries  maintain  the  most  intimate 
relations  with  the  veins — sometimes  with  two  of  these  vessels,  when  the  artery  is 
placed  between  them  ;  sometimes  with  only  one,  which  is  always  more  superficial. 

h.  The  arteries  are  usually  accompanied  by  nerves  belonging  to  the  cerebro- 
spinal or  sympathetic  systems.     Those  of  the  latter  category  are  distinguished  by 


602  THE  ARTERIES. 

the  reticular  interlacing  they  form  around  the  visceral  arteries ;  their  structure 
will  be  alluded  to  presently. 

c.  Lodged,  for  the  most  part,  in  the  interstices  of  the  muscles,  the  arteries 
contract  relations  with  these  organs  which  it  is  very  important  to  know,  from 
a  surgical  point  of  view.  Some  of  these  muscles  lie  parallel  with  important 
arteries,  and  for  this  reason  have  been  designated  satellite  muscles  ;  they  serve  to 
guide  the  surgeon  in  searching  for  the  arteries,  by  the  more  or  less  salient  relief 
their  presence  affords  beneath  the  skin. 

It  is  worthy  of  remark  that  the  arteries  are  not  included  in  the  fibrous 
sheaths  enveloping  the  muscles  ;  these  vessels  nearly  always  occupy,  with  the 
nerves  wiiich  accompany  them,  special  lodgments  from  the  approximation  of 
several  aponeurotic  sheatlis.  When  they  pass  through  the  substance  of  a  muscle 
— which  sometimes  happens — they  are  covered  by  a  fibrous  arch  or  ring,  which 
protects  them  from  compression  during  muscular  contraction — the  arch  or  ring 
receiving  on  its  convexity  the  insertion  of  fibres  from  the  muscle. 

d.  Nothing  is  more  common  than  to  see  the  arteries  in  direct  relation  with 
the  bones — as,  for  instance,  the  aorta,  intercostals,  etc.  Neither  is  it  very  rare 
to  find  a  more  or  less  thick  layer  of  muscle  between  the  arteries  and  portions  of 
the  skeleton.  In  every  case,  a  knowledge  of  the  relations  between  the  arteries  and 
bones  is  important  to  the  surgeon  ;  as  it  enables  him  to  interrupt  the  circu- 
lation temporarily  in  these  vessels,  by  exercising  external  pressure  on  the  points 
of  their  course  which  correspond  to  the  several  bones,  and  thus  diminish  their 
calibre  by  flattening  them. 

e.  In  consequence  of  their  deep  situation,  the  arteries  are,  in  general,  distant 
from  the  skin  ;  there  are,  nevertheless,  some  which  course  immediately  beneath| 
that  membrane ;  but  these  are  only  found  about  the  head  and  in  the  extremities. 

/.  Lastly,  all  the  arteries  are  enveloped  by  a  layer  of  connective  tissue,  which 
forms  around  them  a  kind  of  sheath,  generally  difficult  to  tear  with  the  fingers, 
and  which  isolates  from  the  neighbouring  parts,  but  chiefly  the  veins.  This 
connective  tissue — more  or  less  abundant  according  to  the  regions — is  always  loose 
enough  to  allow  the  arteries  to  roll  and  be  displaced  with  the  greatest  facility, 
and  thus  to  glide  away  from  sharp  bodies  accidentally  introduced  into  the  tissues. 

Anastomoses. — Very  often  the  arteries  are  united  to  each  other  by  communi- 
cations, which  have  received  the  name  of  anastomoses,  and  which  assure  the 
equable  distribution  of  the  blood  in  regulating  its  flow.    There  are  distinguished : 

1.  Anastomoses  hy  convergence — formed  by  two  vessels  joining  at  their 
terminal  extremity  in  an  angular  manner,  to  form  a  third  and  more  voluminous 
trunk. 

2.  Anastomoses  hy  arches  or  hy  inosculation — due  to  the  junction  of  two 
principal  branches,  which  are  inflected  towards  each  other,  meet,  and  unite  to 
form  a  single  and  curvilinear  canal. 

3.  Anastomoses  hy  transverse  communication — represented  by  ramifications 
thrown  transversely  between  two  parallel  arteries. 

4.  Mixed  or  composite  anastomoses — in  which  are  found  a  combination  of  the 
different  types  enumerated  above. 

A  knowledge  of  the  anastomoses  of  vessels  is  of  the  highest  practical  interest ; 
as  these  communications  permit  the  surgeon,  in  extreme  cases,  to  tie  the  principal 
artery  of  a  region  without  the  latter  experiencing  any  considerable  nutritive 
disturbance  ;  the  blood  continuing  to  amve  by  the  collateral  vessels  which,  at 
first  very  small,  gradually  dilate  from  the  eccentric  pressure  to  which  their  walls 


GENERAL   CONSIDERATIONS. 


are  submitted.  But  these  anastomoses,  if  they  offer  this  immense  advantage, 
have  also  their  inconveniences :  we  refer  to  the  difficulties  experienced  in  arresting 
hfemorrhage  in  wounds  of  certain  organs,  owing  to  the  relations  of  the  principal 
vessel  with  its  communicating  collaterals. 

Mode  of  Distribution. — The  branches  an  artery  distributes  in  the  neigh- 
bouring organs  are  distinguished  as  terminal  and  collateral.  The  arteries,  after 
pursuing  a  certain  course,  divide  into  several  branches — nearly  always  two,  which, 
as  new  arteries,  continue  the  original  vessel  and  take  the  name  of  terminal 
Irojuches,  because  they  really  begin  at  the  terminal  extremity  of  that  vessel. 

The  collateral  vessels  arise  at  various  distances  along  the  course  of  the  arteries, 


Fig.  360. 


WEB  OF  frog's  foot  STRETCHING  BETWEEN  TWO  TOES,  SHOWING  THE   BL00D-VESSEI5 
AND   THEIR   ANASTOMOSES. 

a,  a,  Veins ;  b,  b,  b,  arteries,  the  capillaries  being  between. 


and  proceed  in  a  lateral  direction  ;  they  increase  in  number  as  the  arteries  become 
more  supei-ficial. 

The  distinction  between  the  terminal  and  collateral  branches  of  arteries  is  not 
always  easy  to  establish,  and  is  far  from  having  an  absolute  value  ;  it  possesses, 
nevertheless,  some  importance,  as  it  greatly  facilitates  description. 

Termination. — Arteries  terminate  in  the  substance  of  the  tissues  by  ex- 
tremely fine  and  numerous  ramuscules,  which  so  frequently  anastomose  with  each 
other  as  to  form  a  plexus  or  microscopical  network,  the  meshes  of  which  are  very 
close.  These  constitute  the  capillary  sijstem,  which  again  gives  rise  to  ramifica- 
tions of  gradually  increasing  size — the  veins.  The  capillary  system  is,  therefore, 
nothing  more  than  a  network  of  microscopical  canals  intermediate  to  the  arteries 
and  veins. 

In  the  erectile  tissues,  the  mode  of  termination  is  different ;  the  small  arteries 
sometimes  opening  directly  into  the  cells  placed  at  the  origin  of  the  veins,  without 
passing  through  a  capillary  plexus.  In  describing  the  genital  organs,  we  shall 
notice,  in  detail,  the  termination  of  the  arteries  in  the  cavernous  tissues. 

Structure. — The  walls  of  arteries  offer  a  certain  rigidity,  which  permits 


601 


THE  ARTERIES. 


these  vessels  to  remain  open  when  they  are  emptied  of  blood.  The  ancients 
believed  this  was  their  normal  condition,  and  that  they  were  filled  with  air  during 
life.  This  was  a  grave  error,  as  they  contain  nothing  but  blood.  The  gaping  of 
the  arteries  must  be  attributed  solely  to  the  physical  properties  of  the  tissues 
composing  their  walls. 

These  walls  comprise  three  tunics — an  internal,  middle,  and  external. 

The  internal  tunic  {tunica  intima)  is  continuous  with  the  endocardium  of  the 
left  heart  on  the  one  part,  and  on  the  other  with  the  capillaries  and  veins.  For 
a  long  time  it  has  been  regarded  as  a  serous  membrane,  but  it  has  not  absolutely 
the  same  texture.  It  is  composed  of  a  simple  endothelial  layer  which  is  in  contact 
with  the  blood,  and  is  formed  by  fusiform  cells  that  slightly  bulge  where  their 
nucleus  is.  The  endothelium  lies  upon  a  layer  of  veiy  fine  elastic  tissue  (the 
fenestrated  membrane  of  Henle),  perforated  by  openings  which  are  occupied  by 


Fier.  3(33. 


Fig.  361. 


Fig.  362. 


EPITHELIAL  CELLS  OP 
BLOOD-VESSELS. 

a,  6,  From  a  vein ;  c, 
from  an  artery. 
Magnified  350  dia- 
meters. 


FENESTRATED  MEMBRANE 
FROM  THE  CAROTID 
ARTERY  OF  THE  HORSE. 

Magnified    350    diame- 
ters. 


NETWORK  OF  COARSE 
ELASTIC  TISSUE  FROM 
MIDDLE  COAT  OF  PUL- 
MONARY ARTERY  OF 
THE  HORSE,  THE  FIBRES 
BEING  PIERCED  WITH 
CIRCULAR       OPENINGS. 

Magnified   350  diame- 
ters. 


a  slightly  fibrillated  connective  substance,  and  by  ramifying  and  anastomosing 
cells.  Beneath  this  layer  there  is  another,  also  composed  of  fine  elastic  and 
connective  fibres  lying  in  a  transverse  direction,  and  which  is  attached  to  an 
elastic  layer  (internal  elastic  layer)  that  determines  the  external  limit  of  the  deep 
tunic  of  arteries  in  the  aorta  ;  this  layer  is  separated  from  the  preceding  by  the 
network  of  Langhans. 

The  middle  tunic  {tunica  media)  is  remarkable  for  its  thickness,  its  elasticity, 
and  its  yellow  colour  in  the  principal  vessels.  It  has  for  base  several  elastic  parallel 
layers,  united  by  means  of  networks  of  fibres  of  the  same  kind,  and  having  spaces 
between  them  which  are  occupied  by  connective  tissue  and  non-striped  muscular 
fibres ;  these  are  arranged  in  a  circular  manner  around  the  vessels.  In  the  umbilical 
and  splenic  (and  also  in  the  aorta,  iliac,  anterior  mesenteric,  and  renal)  arteries, 
there  are  longitudinal  muscular  fibres.  The  proportion  of  these  two  elements 
varies  with  the  size  and  situation  of  the  artery.  In  the  large  trunks— such  as 
the  aorta,  the  elastic  is  more  abundant  than  the  contractile  tissue  ;  in  the 
medium-sized  vessels  they  are  about  equal :  but  in  the  small  arteries,  in  which 
the  contractile  force  of  the  heart  is  lost  because  of  their  distance  from  it,  the 
muscular  fibres  almost  exclusively  compose  the  middle  tunic. 


GENERAL   CONSIDERATIONS. 


605 


Fig.  364. 


The  external  tunic  (tunica  adventitia)  is  only  a  layer  of  connective  tissue,  with 
some  longitudinal  recticulated  elastic  fibres  in  its  deeper  part.  Though  this 
tunic  is  very  thin,  yet  it  is  strong ;  as  a  ligature  tied  tightly  around  an  artery 
will  rupture  the  other  tunics,  but  not  this. 

The  structure  of  the  capillaries  is  not  the  same  as  that  just  described,  but  is 
modified  in  proportion  as  they  are  fine.  In  the  smallest  capillaries,  the  walls  are 
formed  by  a  thin  amorphous  membrane,  in  which  (oblong)  nuclei  are  somewhat 
regularly  disseminated  ;  in  the  finer  arterioles,  another  layer  external  to  this  (the 
contractile  layer)^  and  containing  transverse  nuclei,  is 
observed  ;  and  in  the  larger  arterioles — those  imme- 
diately succeeding  the  small  arteries,  these  two  nucleated 
layers  are  enveloped  by  a  thin  tunic  of  connective  tissue 
{tunica  adventitia). 

(The  most  minute  capillaries  are  merely  tubes  formed 
by  a  single  layer  of  transparent,  thin,  nucleated,  endo- 
thelial cells,  joined  by  their  margins.  When  perfectly 
fresh,  the  capillary  does  not  show  the  edge  of  the  cells, 
owing  to  the  uniform  refractive  property  of  the  wall  of 
the  tube.  The  nuclei  show  an  internuclear  plexus  of 
fibrils.  The  cells  are  united  by  cement  substance,  and 
here  and  there  minute  dots  or  slits  may  be  seen,  which 
have  been  supposed  by  some  authorities  to  be  openings 
— stomata,  or  stigmata.  The  narrojvest  meshes  of  capil- 
laries occur  in  the  lungs  and  liver,  and  the  wider  in 
muscle,  beneath  serous  membranes,  and  in  the  organs  of 
sense.  The  widest  capillaries  are  found  in  the  liver,  and 
the  narrowest  in  the  retina  and  muscle.) 

Vessels  and  nerves. — The  arteries  are  provided  with 
vessels  termed  vasa  vasorum,  which  are  furnished  either 
by  the  arteries  themselves,  or  by  neighbouring  vessels. 
These  vasa  vasorum  form  a  superficial  network  with 
quadrilateral  meshes,  and  a  deep  plexus,  the  principal 
branches  of  which  are  helicoidal.  The  majority  of 
anatomists  believe  that  this  plexus  does  not  extend  be- 
yond the  external  tunic. 

The  lymphatic  vessels  maintain  intimate  relations, 
in  certain  regions,  with  the  capillaries.  In  the  brain 
and  spleen  there  has  been  discovered,  Around  the  arterial 
capillaries,  a  vessel  that  completely  envelops  them,  and 
which  has  been  named  the  lymphatic  sheath. 

The  nerves,  designated  vasa  motors,  accompany  the 
vessels  and  penetrate  the  muscular  tunic,  in  which  they 

are  distributed.  These  vasomotor  filaments  join  the  branches  of  the  capillaiy 
plexuses,  and  form,  at  the  points  where  they  meet  each  other,  ganglionic  enlarge- 
ments ;  from  these  arise  the  fibres  of  Remak,  the  termination  of  which  is 
unknown. 

Anomalies  in  the  Arteries. — In  their  arrangement,  the  arteries  very  often 

present  anomalies  which  the  surgeon  should  be  guarded  against.     These  usually 

are  related  to  their  number,  their  point  of  origin,  and  their  volume.     In  a  purely 

anatomical  and  physiological  point  of  view,  however,  these  anomalies  are  of  no 

41 


TRANSITION  OF  A  MINUTE 
ARTERY  OF  THE  BRAIN 
INTO  CAPILLARY  VES- 
SELS. 

1,  Minute  artery  ;  2,  tran- 
sitional capillary;  3, 
coarse  capillary  with 
thick  coat,  represented 
by  a  double  contour  line ; 
4,  fine  capillary  with 
single  contour.  The 
nuclei  are  seen  widely 
scattered  in  4  and  3 ; 
more  closely  congregated 
in  2  ;  and  still  more  so 
in  1,  where  they  form  an 
epithelium.  a,  Trans- 
verse elongated  nuclei 
of  muscular  cells,  the 
incipient  muscular  coat 
of  the  artery. 


606  THE  ARTERIES. 

moment ;  as  it  matters  little  whether  the  blood  comes  from  one  source  rather 
than  another,  or  that  a  collateral  vessel  becomes  the  principal  at  the  expense  of 
the  parent  trunk,  provided  its  relations  are  not  altered,  and  the  principle  of 
immutability  of  connections  is  maintained. 

Preparation  of  the  Arteries. — This  requires  two  successive  operations :  1.  lujection. 
2    Dissection. 

Injection  of  the  arteries. — The  object  to  be  attained  in  injecting  these  vessels,  is  to  intro- 
duce into  their  interior  a  solidifiable  substance  which  will  cause  them  to  assume  the  volume 
and  f'onformation  they  presented  during  life,  when  they  are  filled  with  blood. 

Tallow,  coloured  by  lamp-black,  is  the  most  convenient  and  general  injecting  material. 
Sometimes  a  solution  of  gelatine,  with  the  addition  of  a  certain  quantity  of  plaster  of  Paris,  is 
used ;  but  this  is  seldom  employed  in  the  French  scliools.  A  copper  or  brass  syringe,  and 
a  cannula  witli  a  stop-cock  to  fit  ou  its  extremity,  are  the  only  instruments  necessary  to  propel 
these  matters  into  the  arteries. 

The  following  are  the  details  of  the  operation,  when  it  is  desired  to  make  a  general  injec- 
tion : — The  animal  being  placed  ou  a  table,  the  carotid  artery  is  exposed  by  an  incision  in  the 
jugular  channel,  and  opened  longitudiually.  A  ligature  is  applied  above  the  opening,  and  the 
tube,  with  the  stop-cock,  is  firmly  fixed  in  the  cavity  of  the  artery  towards  the  heart  by 
a  second  ligature.  The  injection,  previously  prepared,  is  taken  up  by  the  syringe,  which  ia 
fitted  into  the  tube,  and  the  piston  pushed,  in  order  to  drive  the  contents  of  the  instrument 
into  the  arterial  canals. 

To  perform  the  operation  successfully,  the  following  precautions  are  to  be  attended  to: 
1.  Inject  tlie  vessels  of  an  animal  killed  by  effusion  of  blood,  and  yet  warm.  2.  If  suet  is 
employed,  and  wiiich  is  always  to  be  recommended,  make  it  so  hot  that  tlie  finger  can  scarcely 
endure  it.  When  it  is  colder  than  this  it  solidifies  too  quickly,  and  when  hotter  it  shrivels  up 
the  sigmoid  valves,  passes  into  the  left  ventricle,  and  from  thence  into  the  auricle  and  pul- 
monary veins — an  acciilent  generally  attributed  to  the  too-powerful  force  applied  to  the  piston 
of  the  syringe.  3.  Do  not  make  any  undue  pressure  on  the  piston,  though  this  does  not  strain 
the  sigmoid  valves  so  frequently  as  is  believed.  4.  Cease  injecting  when  the  arteries  react,  by 
their  elasticity,  on  the  piston,  so  as  to  drive  it  back  in  the  syringe. 

In  order  to  ensure  the  retention  of  the  injected  matter  in  the  arteries,  and  prevent  the 
sigmoid  valves  being  forced,  a  cork  may  be  introduced  into  the  aorta  through  the  left  ventricle, 
and  firmly  tied  there  by  a  strong  ligature  ;  the  cork  should  have  a  transverse  notch  for  the 
reception  of  the  li<:ature. 

Instead  of  injecting  by  the  carotid,  a  long  curved  cannula  may  be  fixed  to  the  aorta  itself, 
after  making  an  opening  in  the  left  side  of  the  chest,  on  a  level  with  the  heart,  by  the  ablation 
of  two  segments  of  the  ribs,  and  incising  the  pericardium  and  left  auricle  to  introduce  it.  This 
mode  allows  the  tallow  to  be  injected  at  a  very  liigh  temperature,  and  gives  the  best  results, 
for  it  can  then  penetrate  to  the  capillaries,  if  we  only  know  how  to  manage  it ;  in  certain  organs 
the  injected  matter  may  even  be  made  to  return  by  the  veins. 

But  no  matter  what  procedure  may  be  adopted,  there  are  several  parts  into  which  the 
tallow  can  never  be  made  to  enter  by  a  general  injection  ;  these  are  the  four  extremities.  So 
that  a  special  operation  must  be  resorted  to,  in  order  to  fill  their  vessels.  After  separating 
them  from  the  trunk,  by  sawing  them  through  above  the  knees  and  hocks,  tliey  should  be 
allowed  to  steep  for  two  hours  in  water,  constantly  kept  up  to  a  temperature  of  from  140°  to 
160°  Fahr.  at  most;  it  is  then  easy  to  inject  them,  either  by  the  posterior  radial  artery,  or  the 
anterior  tibial,  after  tying  those  branches  which  may  be  open  at  the  cut  extremity  of  the  limbs. 

If  it  is  desired  to  make  partial  injections  in  other  parts  of  tlie  body,  it  will  be  better  not  to 
sepaiate  them  from  the  trunk;  but  only  to  tie  those  vessels  which  anastomose  between  the 
arteries  to  be  filled  and  those  which  are  not.  For  example,  to  inject  the  arteries  of  the  head, 
it  suffices  to  push  the  mixture  into  one  of  the  common  carotids,  after  ligaturing  the  other  in 
the  middle  of  the  neck,  and  both  vertebrals  in  the  space  between  the  two  portions  of  the 
scalenus  muscle. 

We  may  give  the  tallow  more  fluidity,  and  a  higher  degree  of  penetration,  by  mixing  with 
it  a  little  spirits  of  turpentine ;  or  more  consistence,  in  adding  to  it  a  small  proportion  of 
beeswax. 

The  two  following  mixtures  are  borrowed  from  Oruveilhier's  Anatomy : — 

Tallow 9  parts. 

Turpentine 1  part. 

Ivory  Black,  mixed  witli  spirits  of  turpentine  .     .     2  parts. 


PULMONARY  ARTERY.  607 

For  preservative  injections  : — 

Beeswax 1  part. 

Tallow 3  parts, 

Vermilion,  indigo,  or  Prussian  blue,  previously 
mixed  in  oil  of  turpentine A  sufficient  quantity. 

Of  course,  it  is  well  understood  tliat  these  instructions  are  only  intended  for  the  dissecting- 
room  injections  necessary  for  the  study  of  descriptive  anatomy.  To  inject  the  capillaries,  it  is 
requisite  to  have  recourse  to  other  substances  and  other  procedures.  Suffice  it  to  say  that 
these  injections  are  made  with  cold  fluids,  such  as  varnish,  alcohol,  or  spirits  of  turpentine, 
holding  ill  suspension  extremely  fine  colouring  matter,  gum  arable  dissolved  and  coloured  by 
a  substance  also  in  solution,  etc.,  or,  better  still,  colours  rubbed  up  in  oil,  and  mixed  with  oil 
of  turpentine. 

Dissection  of  the  arteries. — There  are  no  general  rules  to  be  given  for  the  dissection  of 
arteries. 


CHAPTER  II. 
Pulmonary  Artery  (Fig,  349,  e). 


Preparation. — The  pulmonary  artery  is  not  filled  by  tlie  general  injection  mentioned  above. 
It  is  directly  injected  by  propelling  the  tallow  into  the  right  heart  by  the  anterior  vena  cava, 
after  tying  the  posterior  vena  cava. 

The  pulmonary  artery  arises  from  the  infundibulum  {conus  arteriosus)  in  the 
right  ventricle,  is  directed  upwards  and  then  backwards,  describing  a  curve  the 
concavity  of  which  is  infero-posterior ;  on  reaching  the  left  auricle,  it  divides 
into  two  secondary  arteries — one  for  each  lung.  These  arteries  enter  the  pulmonary 
tissue  with  the  bronchi,  and  exclusively  ramify  in  it. 

The  pulmonary  artery  accompanies  the  trunk  of  the  aorta  on  the  right  side, 
and  is  enveloped  with  it  in  a  serous  sheath,  a  dependency  of  the  visceral  layer  of 
the  pericardium.  At  its  origin,  it  is  flanked  before  and  behind  by  the  auric ules 
and  the  cardiac  vessels.  About  the  middle  of  its  course,  it  is  united  to  the 
posterior  aorta  by  means  of  a  yellow  elastic  fibrous  cord  (the  ligamentum  arte- 
riosum),  the  remains  of  the  ductus  arteriosus  which,  in  the  foetus,  establishes  a 
large  communication  between  these  two  vessels  (*Fig,  349,  e). 

The  w^alls  of  the  pulmonary  artery  are  much  thinner  than  those  of  the  aorta, 
and  are  yellow  and  elastic,  as  in  the  other  canals  of  the  same  order.  We,  how- 
ever, have  seen  them  in  an  Ass,  formed  almost  entirely  of  red  muscular  fibres, 
analogous  to  the  fasciculi  of  the  heart. 

It  may  be  repeated  that  the  pulmonary  artery  conveys  to  the  lungs  the  dark 
blood  carried  to  the  right  heart  by  the  veins  of  the  general  circulation. 


THE  ARTERIES. 


CHAPTER   III. 
THE    AORTA. 


If  we  take  a  general  survey  of  the  aorta,  we  shall  find  that  it  arises  from  the 
base  of  the  left  ventricle,  ascends  to  beneath  the  dorso-lumbar  column,  curving 
backwards  and  downwards,  and  reaches  the  entrance  to  the  pelvis,  where  it 
terminates  by  four  branches.  It  furnishes,  besides,  about  from  2  to  2^  inches 
from  its  origin,  a  secondary  trunk,  which  soon  divides  into  two  new  arteries,  the 
right  and  largest  of  which  gives  off  a  particular  trunk — the  common  origin  of 
the  two  long  vessels  destined  for  the  head. 

This  disposition  permits  us  to  recognize  in  the  aorta  seven  principal  sections  : 

1.  The  aortic  trunk,  or  common  aorta — the  source  of  all  the  arteries,  and 
giving  origin  to  the  anterior  and  posterior  aorta.  It  only  furnishes  blood 
directly  to  the  heart  itself. 

2.  The  ijosterior  aorta — the  real  continuation  of  the  common  aorta — is  distri- 
buted to  the  posterior  moiety  of  the  trunk  and  to  the  abdominal  limbs  ;  it 
terminates  by  a  double  bifurcation. 

3.  The  internal  and,  4,  external  iliac  arteries — branches  of  this  bifurcation 
which  are  almost  entirely  expended  in  the  posterior  limbs. 

5.  The  anterior  aorta — the  smallest  of  the  two  trunks  furnished  by  the 
common  aorta — is  chiefly  destined  for  the  anterior  moiety  of  the  trunk  and  the 
thoracic  limbs. 

6.  The  axillary  arteries,  or  brachial  trunks ;  these  arise  from  the  bifurcation 
of  the  preceding  artery,  and  are  continued  by  their  terminal  extremity  into  the 
fore  limbs. 

7.  The  carotid  arteries,  or  arteries  of  the  head  ;  these  emanate  by  a  common 
trunk  from  the  right  brachial  bifurcation. 

Article  I. — Aortic  Trunk,  or  Common  Aorta. 

The  point  of  departure  for  all  the  arteries  carrying  red  blood,  the  common 
aorta,  proceeds  from  the  left  ventricle  by  becoming  continuous  with  the  festooned 
fibrous  zone  which  circumscribes  the  arterial  orifice  of  that  cavity.  It  passes 
upwards  and  a  little  forwards,  bifurcating,  after  a  course  of  2  or  2^  inches,  into 
the  anterior  and  posterior  aortoe. 

Its  volume,  inferior  to  that  of  its  two  terminal  branches,  is  not  uniform  ;  at 
its  origin,  and  opposite  the  sigmoid  valves,  it  presents  (an  enlargement — the 
buJbus  a  or  fee— caused  by)  three  dilatations,  each  corresponding  to  what  is  de- 
scribed as  the  si7ius  of  the  aorta  (sinus  aortici,  sinus  Valsah'ce). 

Included,  on  the  right  side,  in  the  crescent  formed  by  the  auricular  mass  ; 
in  relation,  on  the  left  side,  with  the  pulmonary  artery — which  is  joined  to  it  by 
means  of  cellulo-adipose  tissue  traversed  by  the  cardiac  nerves — the  common 
aorta  forms,  with  the  latter  artery,  a  fasciculus  enveloped  by  the  visceral  layer 
of  the  pericardium,  which  is  reflected  as  a  sheath  around  these  two  vessels. 

Two  collateral  arteries  are  given  off  directly  from  the  aorta — the  cardiac  or 
coronary  arteries. 


THE  FOSTERIOR  AORTA.  609 

Cardiac  or  Coronary  Arteries  (Figs.  349,  350). 

There  are  two  cardiac  arteries — a  right  and  left — exclusively  destined  for  the 
tissue  of  the  heart. 

Right  Coronary  Artery  (Figs.  349,  1  ;  350,  V). — This  originates  from 
the  front  and  to  the  right  of  the  aorta,  at  the  free  margin  of  the  semilunar 
valves,  and  proceeds  perpendicularly,  or  at  a  right  angle,  from  the  trunk,  passing 
forwards  to  the  right  of  the  pulmonary  artery,  beneath  the  anterior  auricle  ; 
then  to  the  right  and  backwards,  to  reach  the  auriculo-ventricular  groove,  which 
it  follows  till  near  the  origin  of  the  right  ventricular  groove.  Here  it  divides 
into  two  branches — one  vertical,  descending  in  this  groove  to  the  apex  of  the 
heart,  which  it  bends  round  to  the  front,  and  anastomoses  with  an  analogous 
branch  of  the  left  coronary  artery  ;  the  other  is  horizontal,  smaller  than  the 
first,  and  follows  the  original  course  of  the  artery  in  the  auriculo-ventricular 
groove,  also  inosculating  with  the  artery  of  the  left  side. 

Left  Coronary  Artery  (Fig.  349,  2). — This  arises  opposite  the  preceding, 
at  the  same  angle  of  incidence,  passes  behind  the  pulmonary  artery,  and  divides — 
under  the  left  or  posterior  auricle — into  two  branches  similar  in  every  respect  to 
those  of  the  right  artery.  The  vertical  branch  descends  in  the  left  perpendicular 
groove  ;  the  horizontal  is  lodged  in  the  coronary  groove  ;  and  both  anastomose 
with  the  analogous  branches  of  the  opposite  vessels. 

From  this  arrangement,  it  results  that  the  heart  is  surrounded  by  two  arterial 
circles — a  vertical,  or  ventricular,  which  has  been  compared  to  a  meridian  ;  and 
a  horizontal,  or  auriculo-ventricular,  analogous  to  an  equatorial  circle. 

In  their  course — which  is  more  or  less  tortuous — the  coronary  arteries  throw 
out  a  considerable  number  of  ramuscules,  which  enter  the  muscular  tissue  of  the 
heart.  The  vertical  circle  gives  off  branches  that  are  entirely  ventricular  ;  while 
from  the  horizontal  circle  come  the  superior  or  auricular,  and  inferior  or  ventri- 
cular branches.  Among  the  latter  there  is  one  which,  rising  from  the  right 
artery — where  it  bends  at  an  angle  beneath  the  auricle — enters  the  substance  of 
the  right  ventricle  by  passing  round  the  puhnonary  infundibulum  ;  its  ramifica- 
tions anastomose  with  those  of  a  similar  branch  from  the  left  artery,  and  in  this 
way  establishes  another  communication  between  the  two  vessels. 

Article  II. — Posterior  Aorta. 

Course. — This  artery  (Fig.  349,  9)  is  a  continuation  of  the  aorta,  which  it 
nearly  equals  in  volume,  and  from  which  it  passes  upwards  and  backwards,  de- 
scribing a  curve  the  convexity  of  which  is  antero-superior,  and  which  is  known 
as  the  arch  of  the  aorta.  It  thus  reaches  the  left  side  of  the  inferior  face  of  the 
spine,  about  the  seventh  dorsal  vertebra,  behind  the  posterior  extremity  of  the 
longus  cohi  muscle,  and  is  then  carried  directly  backwards,  following  the  bodies 
of  the  vertebrte,  though  a  little  to  the  left  at  first ;  it  gradually  inclines  to  the 
right,  however,  and  reaches  the  median  plane  at  the  pillars  of  the  diaphragm. 
Here  it  passes  through  the  opening  circumscribed  by  these  two  pillars  {hiatus 
aorticus),  enters  the  abdominal  cavity,  and  extends  to  the  entrance  of  the  pelvis, 
under  the  spine,  still  preserving  its  median  position.  On  reaching  the  last 
intervertebral  articulation,  the  posterior  aorta  terminates  by  a  double  bifurcation, 
from  which  arise  the  external  and  internal  iliac  arteries. 


610  THE  ARTERIES. 

Relations. — To  facilitate  the  study  of  its  connections,  the  posterior  aorta  may 
be  divided  into  two  sections — one  thoracic,  the  other  abdominal. 

a.  At  its  origin  or  arch,  the  thoracic  aoria  is  crossed  to  the  right  by  the 
trachea  and  oesophagus  ;  on  the  opposite  side,  it  is  related  to  the  puhnonary 
artery  and  the  left  lung.  For  the  remainder  of  its  extent,  it  is  comprised 
between  the  two  layers  of  the  posterior  mediastinum,  and  through  these  is  in 
relation  with  the  pulmonary  lobes,  which  are  fissured  for  its  reception  ;  this 
fissure  is  much  deeper  in  the  left  than  the  right  lung.  Above,  it  is  in  contact 
with  the  bodies  of  the  last  twelve  dorsal  vertebrae,  and  is  accompanied  on  the 
right  by  the  large  vena  azygos  and  the  thoracic  duct ;  the  latter  is  often  carried 
to  the  left  for  the  whole  or  a  portion  of  its  extent. 

(Remak  observed  muscular  fibres  on  the  external  face  of  the  aortic  arch  and 
thoracic  aorta  in  the  Horse,  Sheep,  and  Pig  ;  the  fasciculi  they  form  are  so  large 
as  to  be  visible  to  the  naked  eye.) 

h.  The  posterior  or  abdominal  aorta,  enlaced  by  the  abdominal  nerves  of  the 
great  sympathetic,  is  in  relation,  above,  with  the  bodies  of  the  luml)ar  vertebrae, 
the  originating  tendon  of  the  diaphragmatic  pillars,  Pecquet's  reservoir  {recepta- 
culum  chyli),  and  the  common  inferior  vertebral  ligament ;  it  passes  above  the 
pancreas  and  the  peritoneum,  the  latter  by  its  sublumbar  layer  covering  the 
posterior  two-thirds  of  the  vessel.  On  the  right,  it  is  accompanied  by  the  posterior 
vena  cava,  which  perhaps  it  slightly  pushes  to  the  left  of  the  median  plane. 

Collateral  bra?iches. — The  arteries  emanating  from  the  posterior  aorta  during 
its  long  course,  very  naturally  form  two  classes  ;  some  are  designated  parietal, 
because  they  are  distributed  to  the  parietes  of  the  great  splanchnic  cavities  ;  the 
others  are  the  visceral  branches,  destined  for  the  organs  lodged  in  these  cavities. 

Among  the  parietal  branches,  may  be  noticed  : — 

1.  The  intercostal  arteries,  furnished  by  the  thoracic  aorta. 

2.  The  diaphragmatic  (or  phrenic)  arteries,  the  origin  of  which  is  placed  on 
the  limits  of  the  two  portions  of  the  vessel. 

3.  The  lumbar  arteries,  and  the  middle  sacral  artery,  arising  from  the  abdo- 
minal aorta. 

The  visceral  branches  are  : — 

1.  The  broncho-CBSophageal  trunk,  emitted  by  the  thoracic  portion  of  the 
aorta, 

2.  The  coeliac  axis,  great  (or  anterior)  mesenteric  artery,  small  (or  posterior) 
mesenteric  artery,  renal  arteries,  spermatic  arteries,  and  small  testicular  (or  artery 
of  the  cord)  or  uterine  arteries,  which  emerge  from  the  abdominal  portion. 

Preparation  of  the  posterior  aorta  and  its  collateral  branches. — Immediately  after  injecting 
according  to  one  of  the  modes  recommended  at  p.  606,  place  the  subject  in  the  first  position, 
the  two  posterior  limbs  being  well  extended  backwards.  Open  the  abdominal  cavity,  and 
remove  from  it  the  intestines  in  the  manner  already  indicated.  Tlie  tallow  having  become 
perfectly  solidified  during  these  necessary  manipulations,  dissection  may  be  proceeded  with 
at  once.  It  is  requisite,  however,  to  remove  the  right  and  left  walls  of  the  thoracic  cavity 
beforehand,  by  suwing  through  the  last  fourteen  or  fifteen  ribs  at  six  or  seven  inches  from  their 
superior  extremity,  and  then  separating  them  from  the  sternum  by  the  saw,  taking  the  pre- 
caution of  detaching  the  peripheral  insertion  of  the  diaphragm.  It  is  recommended  to  prepare, 
from  before  to  behind,  the  various  visceral  branches  of  the  vessel ;  first,  the  hroiiclio-cesophageal 
artery;  then  the  coeliac  axis;  next,  the  anterior  mesenteric  artery  and  the  renal  arteries,  after 
spreading  out  the  intestinal  mass  as  in  Fi?.  283 ;  and,  lastly,  the  small  mesenteric  and  testicular 
arteries,  aftei-  arranging  the  intestines  as  in  Fig.  366. 


THE  POSTERIOR   AORTA.  611 

Parietal  Branches  of  the  Posterior  Aorta. 
1.  Intercostal  Arteries  (Fig.  375). 

The  intercostal  arteries,  placed — as  their  name  indicates — in  the  intervals  of 
the  ribs,  number  seventeen  pairs. 

Origin,  Course,  and  Distribution. — The  last  thirteen  arise  from  the  thoracic 
aorta  only  ;  the  first  comes  from  the  cervical  artery  ;  and  the  next  three  are 
furnished  by  a  special  branch  of  the  dorsal  artery. 

The  aortic  intercostals  emerge  at  a  right  angle  from  the  superior  plane  of 
the  trunk,  on  a  level  with  the  bodies  of  the  dorsal  vertebra,  and  at  regular 
intervals.  Their  origin  is  nearer  that  of  the  arteries  on  the  opposite  side  as 
they  are  more  anterior,  the  first  two  or  three  arising  in  pairs  from  a  common 
trunk. 

These  aortic  intercostals  ascend  to  the  vertebral  bodies,  beneath  the  pleura, 
in  crossing  the  direction  of  the  sympathetic  nerve-trunk  and — the  arteries  of  the 
right  side  only — in  addition,  that  of  the  vena  azygos  and  the  thoracic  duct,  to 
the  superior  extremity  of  the  intercostal  spaces,  where  those  of  both  sides  divide 
into  two  branches — the  one  inferior,  or  j^roper  intercostal ;  the  other  superior,  or 
dorso-spinal. 

The  inferior  and  superior  branches  of  the  first  four  intercostal  arteries 
emanate  solely  from  the  trunk  that  furnishes  them,  and  which  is  the  superior 
cervical  artery  for  the  first  intercostal,  and  the  subcostal  branch  of  the  dorsal 
artery  for  the  succeeding  three. 

Inferior  or  intercostal  branch. — This  branch,  the  most  considerable  of  the 
two,  placed  at  first  beneath  the  pleura,  then  between  the  two  intercostal  muscles, 
is  lodged,  along  with  a  satellite  vein  and  nerve,  in  the  furrow  on  the  posterior 
face  of  the  rib,  and  descends  to  the  inferior  extremity  of  the  intercostal  space, 
where  it  terminates  in  the  following  manner  :  the  first  twelve  or  thirteen 
branches  anastomose  with  the  intercostal  ramifications  of  the  internal  thoracic 
artery  and  its  asternal  branch  ;  the  others  are  prolonged  into  the  abdominal 
muscles,  where  their  divisions  communicate  with  those  of  the  anterior  and 
posterior  abdominal  arteries,  as  well  as  with  the  circumflex  iliac. 

In  their  course,  these  intercostal  branches  give  arterioles  to  the  pleurae,  the 
ribs,  and  the  thoracic  muscles,  with  the  perforating  ramuscules  which  cross  these 
muscles  to  ramify  in  the  skin  and  the  panniculus  carnosus,  but  which,  of  course, 
are  absent  where  the  pectoral  wall  is  covered  by  the  thoracic  limb. 

Superior  or  dorso-spinal  branch. — This  passes  directly  upwards  to  be  dis- 
tributed to  the  spinal  muscles  of  the  dorsal  region  and  the  integument  covering 
them,  after  giving  off,  when  passing  the  intervertebral  foramen,  a  branch  which 
enters  the  spinal  canal  by  that  opening,  and  is  destined  for  the  spinal  cord  and 
its  envelopes.  An  auxiliary  of  the  middle  spinal  artery,  this  branch  will  be 
studied  at  greater  length  when  the  cerebro-spinal  artery  is  described. 

Variations  in  origin. — Not  unfrequently  the  first  two  pairs  of  aortic  inter- 
costal arteries  proceed  from  a  single  trunk,  thus  giving  rise  to  four  branches ; 
and  this  trunk  is  also  often  the  source  of  these  four  intercostals  and  the  bronchial 
and  oesophageal  arteries,  when  its  volume  is  very  considerable.  It  is  much 
smaller  when  it  only  gives  off  the  second  pair  of  intercostals,  which  is  sometimes 
the  case. 


612  TEE  ARTERIES. 


2.  Lumbar  Arteries. 


These  are  five  or  sLx  in  number,  and  do  not  differ  in  their  general  arrange- 
ment from  the  intercostal  arteries  ;  they  having  the  same  mode  of  origin,  the 
same  division  into  two  branches,  and  the  same  distribution.  The  superior,  or 
lumbo-spinal  branch,  is  much  larger  than  the  inferior,  and  goes  to  the  muscles 
and  integuments  of  the  lumbar  region ;  it  also  furnishes  a  branch  to  the  spinal 
cord.  The  inferior  branch  passes  above  the  large  and  small  psoas  muscles,  giving 
them  numerous  twigs,  and  extending  to  the  muscular  portions  of  the  transverse 
and  small  oblique  abdominal  muscles,  where  their  ramifications  anastomose  with 
those  of  the  circumflex  iliac  artery. 

The  last,  and  sometimes  also  the  second-last,  lumbar  artery  arises  from  the 
internal  ihac  trunk  ;  the  others  emerge  directly  from  the  iUac  aorta. 

3.  Diaphragmatic  (or  Phrenic)  Arteries. 

These  are  two  or  three  small  vessels  which  spring  from  the  aorta  as  it  passes 
between  the  two  pillars  of  the  diaphragm,  and  are  destined  for  that  muscle. 
The  left  pillar  receives  a  very  insignificant  branch,  but  the  right  has  two,  the 
most  considerable  of  which  is  alone  constant ;  it  sometimes  sends  subpleural 
ramuscules  to  the  right  lung. 

4.  Middle  Sacral  (Sacra  Media)  Artery. 

This  vessel  is  often  absent,  and  when  it  exists  is  very  variable  in  size,  though 
always  extremely  slender.  It  arises  from  the  terminal  extremity  of  the  aorta, 
in  the  angle  comprised  between  the  two  internal  iliac  arteries,  and  is  carried  to 
the  inferior  face  of  the  sacrum,  where  it  is  expended  in  lateral  ramifications 
which  go  to  the  periosteum.  It  has  been  thought  necessary  to  notice  this  artery, 
as  it  attains  a  considerable  volume  in  Man  and  some  animals,  and  continues  the 
aortic  ramifications  beneath  the  sacral  portion  of  the  vertebral  column. 

Visceral  Branches  of  the  Posterior  Aorta. 

1.   Broncho-cesophageal  Artery  (Fig.  318,  m). 

Destined  for  the  lung,  the  visceral  pleura,  the  mediastinum,  and  the  oeso- 
phagus, this  artery  arises,  not,  as  is  generally  said,  in  the  concavity  of  the  arch 
of  the  aorta,  but  opposite  to  it,  and  very  near,  but  to  the  right  of,  the  first  pair 
of  intercostals  ;  often  even  in  common  with  these  arteries  and  with  the  second 
pair.^  After  leaving  the  aorta,  it  insinuates  itself  between  that  trunk  and  the 
oesophagus,  and  above  the  bifurcation  of  the  trachea  divides  into  branches,  the 
bronchial  arteries.  In  its  short  course,  it  gives  off  the  two  ascqyhageal  arteries 
and  a  certain  number  of  innominate  ramiiscuhs. 

Bronchial  Arteries. — The  disposition  of  these  two  vessels  is  extremely 
simple  ;  they  enter  the  lung  with  the  bronchi — one  to  the  right,  the  other  to 
the  left — and  there  break  up  into  arborescent  ramifications  that  follow  the  air- 
tubes  to  the  pulmonary  lobules. 

(Esophageal  Arteries. — These  two  arteries  are  placed  in  the  posterior 
mediastinum,  one  above,  the  other  below  the  oesophagus,  which  they  accompany 
for  a  short  distance  backwards,  to  the  extremity  of  that  canal. 
'  See  Intercostals. 


THE  POSTERIOR  AORTA.  613 

The  superior  esophageal  arter//,  much  more  voluminous  than  the  inferior, 
inosculates  with  a  branch  of  the  gastric  artery.  In  its  course  it  gives  descending 
branches  to  the  oesophagus,  and  ascending  ones  to  the  mediastinum. 

The  inferior  oesophageal  artery  also  anastomoses  with  a  branch  of  the  gastric  ; 
most  frequently  with  that  noticed  above.  Ifc  likewises  furnishes  ascending  and 
descending  divisions  ;  the  latter,  however,  going  to  the  mediastinum,  and  the 
former  to  the  oesophagus. 

Innominate  Ramuscules. — The  innominate  ramuscules  of  the  broncho- 
oesophageal  trunk  do  not  all  proceed  directly  from  it,  there  being  always  a 
certain  number  which  emerge  from  the  bronchial  or  oesophageal  arteries.  They 
are  more  particularly  distributed  to  the  trachea,  to  that  portion  of  the  oesophagus 
which  is  in  contact  with  the  posterior  extremity  of  that  tube,  to  the  bronchial 
glands,  the  mediastinum,  and  the  pulmonary  pleura.  Those  destined  for  the 
latter  form  on  the  surface  of  the  lung — along  with  the  divisions  of  the  pleural 
branch  furnished  by  the  gastric  artery — a  beautiful  plexus. 

2.  CcELiAC  Artery  (or  Axis)  (Fig.  365,  2). 
This  artery  arises  at  a  right  angle  from  the  inferior  face  of  the  aorta, 
immediately  on  the  entrance  of  that  vessel  into  the  abdominal  cavity.  After 
a  course  from  half  to  three-fourths  of  an  inch  at  most,  in  the  middle  of  the  solar 
plexus,  and  beneath  the  superior  face  of  the  pancreas,  this  trunk  separates  into 
three  branches — a  middle,  the  gastric  artery ,-  a  right,  the  hepatic  artery ;  and  a 
left,  the  splenic  artery. 

1.  Gastric  Artery  (the  coronaria  ventriculi  of  Man)  (Fig.  365,  3). — This 
artery  descends  on  the  large  tuberosity  of  the  stomach,  extends  to  near  the 
insertion  of  the  oesophagus,  and  then  divides  into  two  branches — the  anterior 
and  posterior  gastric.  The  first  passes  behind  and  to  the  right  of  the  oesophagus, 
and  crossing  the  small  curvature  of  the  stomach,  gains  the  anterior  face  of  that 
viscus,  where  it  separates  into  flexuous  and  divergent  branches  that  run  beneath 
the  serous  membrane,  and  are  carried  more  particularly  towards  the  left  cul-de-sac 
and  around  the  cardia.  The  second  vessel  is  distributed  in  the  same  manner  to 
the  posterior  wall  of  the  organ,  but  chiefly  to  the  right  sac. 

Independently  of  these  two  arteries,  the  gastric  trunk  gives  off  a  third  and 
constant  branch,  which  often  comes  from  one  of  its  two  branches,  and  sometimes 
also  from  the  coeliac  axis  itself,  or  from  the  splenic.  This  branch  accompanies 
the  oesophagus,  along  with  the  right  pneumogastric,  crosses  the  opening  of  the 
right  pillar  of  the  diaphragm  to  enter  the  pectoral  cavity,  and  then  divides  into 
two  branches,  each  of  which  anastomoses  with  one  of  the  oesophageal  arteries, 
and  is  then  thrown  over  the  posterior  extremity  of  a  pulmonary  lobe,  which  it 
covers  with  a  magnificent  subpleural  reticular  arborization.  This  gastro-pulmo- 
nary  artery  often  anastomoses  with  the  superior  oesophageal  branch  only,  and 
goes  exclusively  to  the  right  lung  ;  for  the  left  lung  and  the  inferior  oesophageal 
artery,  in  this  case  there  is  a  special  branch  that  emanates  from  the  anterior 
gastric.  It  is  not  rare  to  meet  with  varieties  of  another  kind,  but  of  which 
it  is  not  necessary  to  speak ;  inasmuch  as  in  these  pleural  ramifications  we  find 
a  disposition  common  to  the  whole  arterial  system — distribution  almost  invari- 
able, origin  very  inconstant. 

2.  Splenic  Artery  (Fig.  365,  7). — The  largest  of  the  three  branches  of 
the  coeliac  axis,  this  artery  is  directed  downwards  and  to  the  left,  lying  beside 
its  satellite  vein  and  the  superior  face  of  the  left  extremity  of  the  pancreas.     It 


614 


TEE  ARTERIES. 


reaches  the  anterior  fissure  of  the  spleen,  in  turning  round  the  cardiac  extremity 
of  the  stomach,  passes  along  the  entire  length  of  that  fissure,  and  leaves  it  only 
near  the  point  of  the  organ  to  throw  itself  into  the  great  omentum,  where  it  is 
named  the  left  gastro-omeatal  artery  (or  gastro-epiploica  sinistra). 

The  splenic  artery  gives  off,  during  its  course,  very  numerous  collateral 
oranches.     These  are  : 

(1)  External  or  splenic  ramifications,  which  immediately  enter  the  substance 
of  the  spleen  (Fig.  365). 

Fig.  365. 


ABDOMINAL   OE  POSTERIOR   AORTA    AND   CCELIAC   AXIS,    IN   THE    HORSE. 

1,  Aorta;  2,  cceliac  axis;  3,  gastric  artery,  4,  posterior  gastric  artery;  5,  anterior  gastric  artery, 
6,  pleural  brancii  of  the  gastric  artery;  7,  splenic  artery;  8,  gastric  ramuscules;  9,  omental 
rainuscules  of  the  splenic  artery  ;  10,  left  gastro-splenic  artery ;  10',  one  of  the  gastric  branches 
of  that  vessel;  11,  hepatic  artery;  12,  pyloric  artery;  13,  right  gastro-oniental  artery;  14, 
duodenal  artery  ;  15,  trunk  of  the  great  mesenteric  ;  16,  first  branch  of  the  left  fasciculus  of  that 
artery,  communicating  with  the  duodenal  ;  17,  right  renal  artery.  C,  Oesophagus  ;  E,  stomach, 
lifted  against  the  liver  and  diaphragm  ;  D,  duodenum  ;  F,  f',  f",  lobes  of  the  liver;  /,  Spigelian 
lobe  (caudate  lobe),  S,  spleen;  R,  r,  kidneys  and  supra-renal  capsules,  s,  s ;  u,  u,  ureters;  G, 
posterior  vena  cava  ;  P,  vena  porta; ;  p,  p,  crura  or  pillars  of  the  diaphragm. 

(2)  Internal  or  gastric  ramifications,  also  called  the  short  vessels  (vasa  hrevia) 
m  Man,  which  are  comprised  between  the  two  layers  of  the  gastro-splenic 
omentum,  and  go  to  the  great  curvature  of  the  stomach,  where  they  nearly 
always  divide  into  two  branches — one  which  ramifies  on  the  anterior  wall  of  the 


TBE  POSTERIOR  AORTA.  615 

viscus,  the  other  on  its  posterior  wall.  These  vessels  inosculate  with  those  sent 
to  the  membranes  of  the  stomach  by  the  proper  gastric  artery  (Fig.  365,  8). 

(3)  Posterior  or  omental  twigs  of  little  importance,  destined  for  the  great 
omentum  (Fig.  365,  9). 

Left  gmtro-omental  artery  (Fig.  365,  10). — This  artery  follows  the  great 
curvature  of  the  stomach  to  a  distance  varying  with  the  state  of  repletion  of 
that  viscus,  passing  between  the  two  layers  of  the  omentum,  and  inosculating 
with  the  right  gastro-omental  artery.  The  branches  it  sends  off  on  its  track  are 
descending  or  omenta}.,  and  ascending  or  gastric;  the  latter  being  disposed 
exactly  like  the  analogous  branches  emanating  directly  from  the  splenic 
artery. 

3.  Hepatic  Artery  (Fig.  365,  11). — Applied  to  the  superior  face  of  the 
pancreas,  and  encrusted,  as  it  were,  in  the  tissue  of  that  gland — the  anterior 
border  of  which  it  follows — the  hepatic  artery  is  directed  from  left  to  right, 
passes  under  the  posterior  vena  cava,  which  it  crosses  obliquely,  reaches  the 
posterior  fissure  of  the  liver  {foramen  of  Winsloiv),  and  enters  it  with  the  vena 
portae  to  break  up  into  several  branches,  the  ultimate  divisions  carrying  nutrient 
blood  to  the  lobules  of  the  liver. 

Before  reaching  that  organ,  however,  the  hepatic  artery  furnishes  the 
'pancreatic  branches,  the  pyloric  artery,  and  the  right  gastro-omental  artery. 

Pancreatic  arteries. — Irregular  and  very  numerous,  these  branches  are 
detached  from  the  hepatic  artery  on  its  passage  over  the  superior  face  of  the 
pancreas,  and  plunge  into  the  tissue  of  that  gland,  the  arterial  blood  of  which 
is  chiefly  derived  from  this  source. 

Pyloric  artery. — This  vessel  arises  at  the  dilatation  towards  the  origin  of  the 
duodenum,  before  the  hepatic  artery  enters  the  posterior  fissure  of  the  liver,  and 
most  frequently  by  a  trunk  common  to  it  and  the  right  gastro-omental  artery. 
It  passes  towards  the  small  curvature  of  the  stomach,  and  sends  off  branches 
around  the  pylorus,  which  anastomose  with  the  posterior  gastric  arteries  and  the 
right  gastro-omental  artery. 

Right  gastro-omental  artery  {gastro-epiploica  dextra)  (Fig.  365,  13). — This 
artery  crosses  the  duodenal  dilatation  inferiorly  and  posteriorly,  to  place  itself 
in  the  substance  of  the  great  omentum  ;  in  doing  which  it  passes  along  the 
large  curvature  of  the  stomach,  and  anastomoses  by  inosculation  with  the  left 
gastro-omental  artery.  In  its  course,  it  throws  off  omental  and  gastric  branches, 
which  are  analogous  to  those  emanating  from  the  latter  vessel.  Before  crossing 
the  duodenum,  it  also  emits  a  particular  branch,  designated  in  treatises  on 
Veterinary  Anatomy  the  duodenal  artery;  this  is  a  somewhat  considerable 
division,  which  follows  the  small  curvature  of  the  duodenum  in  the  substance  of 
the  mesentery,  and  joins  the  first  artery  belonging  to  the  left  fasciculus  of  the 
great  mesenteric,  after  furnishing  some  twigs  to  the  pancreas,  and  numerous 
branches  to  the  duodenum  (Fig.  365,  14). 

In  terminating  the  description  of  the  right  gastro-omental  artery,  it  may  be 
remarked  that  the  stomach— owing  to  the  anastomoses  uniting  that  vessel  with 
the  artery  of  the  left  side — is  suspended,  as  it  were,  in  a  vertical  arterial  circle, 
formed  by  the  splenic  and  left  gastro-omental  arteries  on  the  one  part,  and  the 
hepatic  and  right  gastro-omental  arteries  on  the  other — a  circle  the  concavity  of 
which  sends  out  on  the  stomach  a  great  number  of  divisions  that  communicate 
with  the  arterial  ramuscules  proper  to  that  viscus. 


616  THE  ARTERIES. 

3.  Antekioe  or  Great  Mesenteric  Artery  (Figs.  365,  306). 

The  anterior  mesenteric  arteri/,  which  ahnost  entirely  supplies  the  mass  of 
intestines  with  blood,  is  as  remarkable  for  its  volume  as  for  its  complicated  dis- 
tribution. This  complexity,  together  with  that  of  the  intestine  itself,  gives  rise 
to  some  difficulty  in  the  study  of  this  vessel ;  but  this  may  be  averted  by  adopting 
the  mode  of  description — as  simple  as  it  is  methodical — resorted  to  in  his  lectures 
by  Lecoq. 

The  anterior  mesenteric  arises  at  a  right  angle  from  the  posterior  aorta,  at 
the  renal  arteries,  and  at  2  or  2^  inches  behind  the  coeUac  axis,  from'  which  it  is 
separated  by  the  pancreas  ;  it  is  directed  immediately  downwards,  enlaced  by  the 
anastomosing  nerves  of  the  solar  plexus,  and  divides,  after  a  course  of  from  1  to 
1^  ^  inches,  into  three  fasciculi  of  branches,  which  are  distinguished  as  left,  right, 
and  anterior.  The  left  fasciculus  goes  to  the  small  intestine  ;  the  right  is  dis- 
tributed to  the  terminal  portion  of  that  intestine,  the  cascum,  and  the  first  portion 
of  the  flexure  formed  by  the  large  colon  ;  the  anterior  is  carried  to  the  second 
portion  of  that  flexure,  and  to  the  origin  of  the  small  colon.  The  order  in  which 
these  three  fasciculi  have  been  indicated  will  also  be  that  followed  in  their  descrip- 
tion ;  this  has,  as  will  be  observed,  the  advantage  of  recalling  to  the  memory  the 
regular  succession  of  the  various  parts  of  the  intestine,  and  consequently  the 
passage  of  the  food  in  this  important  portion  of  the  digestive  canal. 

A.  Arteries  of  the  Left  Fasciculus  (Fig.  366,  2). — These  arteries 
number  from  fifteen  to  twenty,  and  are  named  the  arteries  of  the  small 
intestine  {vasa  intestini  tenuis),  because  of  their  destination.  All  spring  at 
once  from  the  anterior  mesenteric  artery,  either  separately,  or  several  in  common, 
and  pass  between  the  two  layers  of  the  mesentery  to  gain  the  intestine.  Before 
reaching  the  small  curvature  of  that  viscus,  each  divides  into  two  branches,  which 
go  to  meet  corresponding  branches  from  the  neighbouring  arteries,  and  to  anasto- 
mose with  them  by  inosculation  ;  from  this  arrangement-  results  a  series  of 
uninterrupted  arterial  arches,  the  convexity  of  which  is  downwards,  and  which 
exist  for  the  whole  length  of  the  intestine,  opposite,  and  in  proximity  to,  its 
concavity.  From  the  convexity  of  these  arches  emanate  a  multitude  of  branches 
that  arrive  at  the  inner  curvature  of  the  intestine,  and  the  divisions  of  which  pass 
to  each  of  the  faces  of  that  viscus,  to  rejoin  and  anastomose  on  its  great  curvature. 
These  divisions  are  situated  beneath  the  peritoneum  or  in  the  muscular  tunic, 
and  send  the  majority  of  their  ramuscules  to  the  mucous  tunic,  which  is  there- 
fore distinguished  by  its  great  vascularity — a  feature  common  to  all  the  hollow 
organs  in  the  abdominal  cavity. 

Such  is  the  general  arrangement  of  the  arteries  of  the  small  intestine  ;  and  it 
remains  to  indicate  some  of  their  special  characters.  These  are  as  follows  :  1. 
The  longest  arteries  of  the  small  intestine  are  the  most  posterior,  as  they  follow 
the  development  of  the  mesentery,  by  which  they  are  sustained.  2.  The  anterior 
arteries  generally  form  two  series  of  superposed  arches,  before  sending  their 
divisions  to  the  intestine.  3.  The  first  reaches  the  duodenum  and  anastomoses 
with  the  duodenal  artery — a  branch  given  off  by  the  coeliac  axis.  4.  The  last 
communicates  with  the  ileo-caecal  artery — one  of  the  branches  of  the  right 
fasciculus. 

'  This  trunk  of  the  anterior  mesenteric  is  usually,  in  old  horses  killed  for  dissection,  the 
seat  of  a  more  or  less  voluminous  aneurism,  whicii  sometimes  extends  to  the  artery  placed  at 
the  origin  of  the  branches  of  the  right  fasciculus,  and  it  is  not  unfrequeutly  met  with  in  one 
or  the  other  section  of  the  anterior  mesenteric  artery. 


TEE  POSTERIOR  AORTA.  617 

B.  Arteeies  of  the  Right  Fasciculus. — The  right  fascicuhis  of  the  great 
mesenteric  artery  constitutes,  at  first,  a  single  trunk  some  inches  in  length,  which 
soon  divides  into  four  branches.  These  are  as  follows  :  the  ileo-ccecal  artery,  the 
two  ccecal  arteries,  and  the  right  or  direct  colic  artery. 

Ileo-Caecal  Artery  (Fig.  283,  3). — This  vessel  often  has  its  origin  from 
the  internal  csecal  artery.  It  is  placed  between  the  two  layers  of  the  mesentery, 
follows  for  a  short  distance,  and  in  a  retrograde  manner,  the  ileo-csecal  portion 
of  the  small  intestine,  and  wholly  anastomoses  with  the  last  artery  of  the  left 
fasciculus,  after  emitting  a  series  of  branches,  which  are  distributed  to  the 
intestinal  membranes. 

Caecal  Arteries. — Distinguished  into  internal  or  superior,  and  external  or 
inferior,  these  two  arteries  pass  downward  and  a  httle  to  the  right,  towards  the 
concavity  of  the  caecal  flexure,  embracing  between  them  the  terminal  extremity 
of  the  small  intestine,  and  lying  at  the  middle  part  of  the  csecal  sac,  following 
its  direction. 

The  superior,  or  internal  ccecal  artery,  is  lodged  in  the  most  anterior  of  the 
fissm-es  formed  by  the  longitudinal  bands  of  the  cscum,  and  extends  beneath 
the  serous  tunic  to  nearly  the  point  of  the  viscus,  where  it  terminates  by 
anastomosing  with  the  external  caBcal  artery.  The  branches  furnished  by  this 
artery  during  its  course  escape  in  a  perpendicular  direction,  and  distribute  their 
ramifications  on  the  walls  of  the  caecum  (Fig,  283,  4), 

The  external,  or  inferior  ccecal  artery,  passes  between  the  csecum  and  the  origin 
of  the  colon,  to  descend  along  the  first-named  organ  by  placing  itself  in  one  of 
the  external  fissures,  which  is  situated  outwardly  and  posteriorly.  Arriving  at 
the  point  of  the  organ,  this  artery  bends  over  it  to  anastomose  with  the  vessel 
just  described  (Fig.  283,  7).  It  gives  off  on  its  track  a  series  of  transverse 
ramifications,  similar  to  those  of  the  latter  artery  ;  and  besides  these,  a  remarkable 
branch  which  may  be  named  the  artery  of  the  ccecal  arch.  This  branch  is  detached 
from  the  principal  vessel  near  the  origin  of  the  colon,  and  ascends  to  the  caecal 
arch,  following  its  concavity  outwardly  to  pass  forwards  and  downwards  to  the 
first  portion  of  the  large  colon,  where  it  disappears  after  following  a  certain 
com'se.  The  nimierous  collateral  branches  detached  by  this  artery  are  sent  to 
the  walls  of  the  latter  portion  of  intestine,  and  the  arch  of  the  caecum 
(Fig.  283,  6). 

Right  or  Direct  Colic  Artery  (Fig.  283,  7). — This  is  the  largest  of  the 
branches  composing  the  right  fasciculus  of  the  anterior  mesenteric  artery. 
Destined  for  the  right  portion  of  the  flexure  fonned  by  the  large  colon,  it  lies 
immediately  beside  that  viscus,  beneath  the  peritoneal  membrane,  following  it 
from  its  origin  to  its  pelvic  flexure,  where  the  artery  anastomoses  by  inosculation 
with  the  left  colic  or  retrograde  artery. 

C.  Arteries  of  the  Ajstterior  Fasciculus. — These  are  only  two  in 
number  :  the  left  colic  or  retrograde,  and  the  ^rs^  artery  of  the  small  colon,  joined 
at  their  origin  to  an  extremely  short  trunk. 

Left  Colic  or  Retrograde  Artery  (Fig.  283,  8). — This  is  carried  to  the 
left  portion  of  the  colic  flexure,  which  it  passes  over,  beneath  the  peritoneum, 
from  the  terminal  extremity  of  the  viscus  to  the  pelvic  flexure,  where  it  meets 
the  right  artery  ;  in  this  manner  it  follows  a  course  the  inverse  of  that  pursued 
by  the  food,  whence  its  name  of  retrograde  colic  artery. 

Considered  collectively,  the  two  colic  arteries  represent  a  loop  or  flexure  exactly 
like  that  formed  by  the  large  colon  itself.     They  proceed  parallel  to  each  other 


618  THE  ARTERIES. 

and  finish,  after  being  slightly  separated,  by  uniting  to  form  a  parabolic  curve. 
This  arterial  loop  occupies  a  deep  position  on  the  intestinal  loop,  being  found  on 
the  inferior  face  of  the  first  and  fourth  sections  of  the  large  colon,  in  the  con- 
cavity of  the  flexure  which  gives  rise  to  the  supra-sternal  and  diaphragmatic 
curvatures,  and  on  the  superior  plane  of  the  second  and  third  portions  of  the 
vise  us. 

A  considerable  number  of  collateral  branches  escape  perpendicularly  from 
this  arterial  loop,  and  pass  into  the  membranes  of  the  intestine  ;  some  of  them 
establish  a  transverse  communication  between  the  two  vessels.  * 

First  Artery  of  the  Small  or  Floating  Colon  (Figs.  283,  9  ;  366,  4).— 
This  branch,  the  calibre  of  which  is  often  considerable,  is  inflected  to  the  left, 
downwards  and  backwards,  to  be  placed  in  the  colic  mesentery,  very  near  the 
lesser  curvature  of  the  floating  or  small  colon.  It  soon  meets  a  branch  of  the 
posterior  mesenteric  artery,  with  w^hich  it  anastomoses  by  inosculation. 

D.  Innominate  Branches  of  the  Great  Mesentery. — These  are  the 
twigs  sent  to  the  lymphatic  glands,  supra-renal  capsules,  mesentery,  and  pancreas, 
the  existence  of  which  it  is  sufiicient  merely  to  mention.  Among  those  supplied 
to  the  pancreas,  there  is  one  of  somewhat  considerable  volume. 

E.  The  Anastomoses  of  the  Great  Mesenteric  Artery. — The  multi- 
plicity and  calibre  of  these  anastomoses  assure,  in  the  most  favourable  manner, 
the  circulation  of  the  blood  in  the  intestinal  mass,  which,  by  reason  of  its  great 
mobility,  is  exposed  to  displacements  capable  of  inducing  more  or  less  extensive 
compression.  Not  only  do  these  anastomoses  unite  the  diff"erent  branches 
destined  to  the  same  portion  of  the  viscera — be  it  the  small  intestine,  the  csecum, 
or  the  large  colon  ;  but  they  also  establish  communications  between  the  anterior 
mesenteric  artery  and  the  neighbouring  trunks,  which  in  case  of  need  can  main- 
tain the  circulation — as,  for  example,  when  the  two  intestinal  arteries  are  com- 
pletely obstructed.  The  blood  from  the  cceliac  axis  can  really  pass  from  the 
duodenal  artery  into  the  branches  of  the  left  fasciculus  of  the  anterior  mesenteric  ; 
then  by  the  ileo-ctecal  artery  into  the  branches  of  the  right  fasciculus,  and 
thence  into  the  left  colic  artery,  which,  finally,  transmits  it  to  the  first  artery  of 
the  small  colon,  as  well  as  to  the  arches  of  the  mesenteric  artery.  The  communi- 
cation existing  between  the  broncho-oesophageal  and  the  coeliac  trunks,  through 
the  medium  of  the  oesophageal  and  gastric  arteries,  even  allows  a  collateral 
circulation  to  be  formed,  which  would  be  capable  of  supplementing  the  posterior 
aorta,  supposing  that  vessel  tied  behind  the  trunk  that  distributes  blood  to  the 
bronchi  and  oesophagus. 

4.  Posterior  or  Small  Mesenteric  Artery  (Fig.  366). 

This  artery  carries  blood  to  the  small  colon  and  rectum,  and  arises  at  a  right 
angle  from  the  inferior  face  of  the  posterior  aorta,  from  A^  to  6  inches  behind 
the  anterior  mesenteric.  It  descends  between  the  two  layers  of  the  colic 
mesentery,  and  is  soon  inflected  back  in  describing  a  curve  upwards,  to  pass 
above  the  rectum  ;  when  near  the  anus,  its  terminal  divisions  enter  the  walls 
of  that  intestine. 

In  its  course  this  artery  gives  off,  at  pretty  regular  intervals,  thirteen  or 
fourteen  branches,  the  foremost  of  which  are  the  largest  and  longest ;  they 
originate  from  the  convexity  of  the  artery — that  is  from  below,  and  either  singly 
or  in  clusters  ;  the  latter  disposition  is  the  most  common  for  the  first  four  or 
five.     They  descend  into  the  mesentery,  and  arrive  near  the  superior  curvature 


THE  POSTERIOR  AORTA. 


619 


of  the  intestine,  where  they  are  disposed  in  the  following  manner :  The  first 
seven  or  eight  bifurcate,  and  form  arches  like  those  of  the  arteries  supplying  the 
small  intestine,  differing  from  them  only  in  being  nearer  the  small  curvature  of 
the  colon  ;  the  other  branches,  which  are  destined  for  the  terminal  part  of  that 

Fig.  366. 


DISTRIBUTION  OF  THE  POSTERIOR  OR  SMALL  MESENTERIC  ARTERY.  THE  SMALL  COLON  WITH  ITS 
MESENTERY  IS  SPREAD  OUT  AND  THE  SMALL  INTESTINE  THROWN  BACK  TO  THE  RIGHT,  UNDER 
THE   DOUBLE   COLON. 

1,  Trunk  of  the  posterior  mesenteric  artery ;  2,  anterior  mesenteric  artery ;  3,  its  anterior 
fasciculus ;  4,  first  artery  of  the  small  colon,  forming  part  of  that  fasciculus ;  5,  retrograde  colic 
artery  ;  6,  right  fasciculus  of  the  anterior  mesenteric;  7,  branches  of  the  left  fasciculus;  8,  renal 
artery.  9,  terminal  extremity  of  the  aorta;  10,  external  iliac  artery;  11,  circumflex  iliac  ai'tery; 
12,  internal  iliac  artery. 

viscus  and  the  rectum,  ramify  in  the  intestinal  membranes  without  having 
previously  formed  any  arches. 

The  anterior  ramuscule  of  the  first  branch  anastomoses  directly  with  the 
artery  sent  to  the  small  colon  by  the  anterior  mesenteric,  and  from  this  anasto- 
mosis results  the  first  colic  arterial  arch. 

5.  Eenal  or  Emulgent  Arteries  (Figs.  338,  2  ;  365,  17). 

These  are  two  arteries — one  for  each  kidney — detached  laterally,  and  at  a  right 
angle,  from  the  abdominal  aorta,  near  the  anterior  mesenteric  arteiy ;  passing 


620  THE  ARTERIES. 

outwards  to  the  internal  border  of  these  organs,  each  divides  into  several 
branches,  which  enter  the  gland  either  by  its  hilus  or  by  its  inferior  face. 
Reaching  the  interior  of  the  kidney,  these  branches  subdivide,  and  form  a  net- 
work of  large  vessels  placed  on  the  limit  between  the  cortical  and  medullary 
portions,  from  which  a  multitude  of  ramuscules  are  given  off,  and  pass  almost 
exclusively  into  the  tissue  of  the  cortical  portion  (see  the  description  of  the 
Kidneys). 

The  right  renal  artery,  longer  than  the  left,  passes  between  the  small  psoas 
muscle  and  the  posterior  vena  cava,  to  reach  the  right  kidney.  Both  arteries 
are  in  relation  with  the  posterior  extremity  of  the  supra-renal  capsules. 

Remarkable  for  their  relatively  enormous  volume,  when  compared  with  that 
of  the  glands  receiving  them,  these  arteries,  before  penetrating  the  proper  tissue 
of  the  kidneys,  give  off  only  a  few  unimportant  ramuscules,  the  principal  of 
which  proceed  to  the  supra-renal  capsules  (Fig.  365).  Other  twigs  from  the 
anterior  mesenteric  artery,  or  even  from  the  aorta  itself,  also  supply  these  small 
bodies.  It  is  not  unusual  to  find  the  kidneys  receiving  vessels  from  the  arteries 
in  their  vicinity.  Thus,  we  have  seen  an  artery  from  the  external  iliac  pass  into 
a  kidney  by  its  lower  face  ;  and  we  have  also  observed  an  artery,  detached  from  the 
aorta  along  with  the  anterior  mesenteric,  enter  the  kidney  bv  its  anterior  border. 

6.  Spebmatic  Arteries. 

These  arteries  differ  in  the  male  and  female  ;  in  the  male  they  are  also 
named  the  great  testicular  arteries ;  in  the  female  they  are  exclusively  designated 
as  the  idero-ovarian  arteries. 

Spermatic  or  Great  Testicular  Artery  (Fig.  338,  3). — This  arises  close 
to  the  posterior  mesenteric  artery,  either  before,  behind,  or  to  one  side  of  it,  but 
rarely  on  the  same  level  as  the  artery  of  the  opposite  side ;  it  is  then  directed 
backwards  and  downwards,  sustained,  with  its  satelHte  vein,  in  a  particular  fold 
of  peritoneum,  and  reaches  the  entrance  to  the  internal  abdominal  ring,  into 
which  it  is  seen  to  pass  with  the  other  portions  of  the  spermatic  cord,  and  to 
descend  on  the  testicle  by  forming  remarkable  fiexuosities,  which  are  united  into 
an  elongated  mass.  Arrived  within  the  head  of  the  epididymis,  this  artery 
insinuates  itself  beneath  the  tunica  albuginea — becomes  encrusted,  as  it  were, 
in  its  substance — and  successively  passes  round  the  superior  border,  posterior 
extremity,  and  the  inferior  border  and  anterior  extremity  of  the  testicle.  In 
this  course  it  is  very  sinuous,  and  detaches  at  a  right  angle  a  large  number  of 
equally  flexuous  branches,  which  creep  over  the  faces  of  the  organ  while  sending 
numerous  ramuscules  into  its  structure.  The  epididymis  also  receives  its  blood 
by  this  artery. 

Utero-ovarian  Artery. — The  origin  of  this  vessel  is  the  same  as  that  of 
the  preceding  artery.  It  is  placed  between  the  two  layers  of  the  broad  ligament, 
and  soon  bifurcates  into  the  ovarian  and  uterine  arteries.  The  ovarian  branch 
describes  numerous  fiexuosities,  like  the  corresponding  artery  in  the  male,  and 
comports  itself  on  the  ovary  in  the  same  manner  as  the  latter  vessel  does  on  the 
testicle.  The  uterine  branch  passes  to  the  comu  of  the  uterus,  where  its  divisions 
anastomose  with  the  proper  uterine  artery. 

7.  Small  Testicular  Arteries  (Male).    Uterine  Arteries  (Fejiale). 
Small  Testicular  Artery  (Cremasteric  Artery,  Artery  of  the  Cord). — 

A  pair,  like  the  spermatic  artery,  this  vessel  is  very  slender,  and  originates 


TEE  POSTERIOR  AORTA.  621 

either  from  the  aorta  between  the  internal  and  external  iUacs,  or  from  the  latter, 
near  its  commencement.  The  last  being  the  most  common,  it  is  usual  to  describe 
it  as  a  collateral  branch  of  the  external  iUac  trunk.  We  have  regarded  it  as  an 
artery  emanating  directly  from  the  posterior  aorta,  in  order  to  include  its  descrip- 
tion with  that  of  the  spermatic  and  the  utero-ovarian  arteries. 

"Whatever  may  be  its  mode  of  origin,  it  gains  entrance  to  the  inguinal  canal 
with  the  spermatic  vessels,  to  be  distributed  to  the  various  parts  constituting  the 
spermatic  cord.  Before  penetrating  the  substance  of  this  cord,  it  gives  off  several 
ramuscules  to  the  peritoneum,  iliac  glands,  ureter,  and  vas  deferens. 

Uterine  Artery. — This  has  the  same  point  of  origin  as  the  preceding — its 
analogue — but  differs  from  it  in  its  larger  volume.  It  is  placed  between  the  two 
layers  of  the  broad  ligament,  and  soon  divides  into  two  branches — ovarian  and 
uterine.  The  ovarian  branch  is  flexuous,  like  the  corresponding  artery  in  the 
male,  and  comports  itself  on  the  ovary  as  that  vessel  does  on  the  testicle.  The 
uterine  branch  passes  to  the  corini  of  the  uterus,  where  its  divisions  anastomose 
with  the  uterine  artery  proper. 

Differential  Chabacters  in  the  Posterior  Aorta  and  its  Collateral  Branches  in 
THE  other  Animals. 

Posterior  Aorta  in  Ruminants. 

The  artery  pursues  the  same  course  as  in  Solipeds,  and  also  terminates  by  four  branches, 
towards  the  entrance  to  the  pelvic  cavity. 

Parietal  Branches. — The  intercostal  arteries  only  differ  from  those  of  the  Horse  in  their 
number;  as  but  twelve  are  met  with,  of  which  eight  or  nine  are  furnished  by  the  posterior 
aorta  alone. 

The  lumbar  and  diaphragmatic  branches  are  absolutely  identical,  in  their  disposition,  with 
the  analogous  arteries  in  Solipeds. 

The  middle  sacral  artery  is  more  considerable  in  volume,  particularly  in  the  Sheep  and 
Goat.     This  will  be  referred  to  hereafter  (see  Internal  iliac  artery  of  Ruminants). 

Visceral  Branches.     Broncho-cesophageal  trunk. — This  offers  nothing  particular. 

Coeliac  axis  (Fig.  367,  1). — This  artery  descends  on  the  rumen,  a  little  behind  the  insertion 
of  the  oesophagus,  is  directed  to  the  right,  and  divides  near  the  omasum  into  two  terminal 
branches — the  stiperior  and  inferior  arteries  of  the  omasum  and  dbomasum. 

The  collateral  branches  given  off  from  this  trunk  are  : — 

1.  Several  diaphragmatic  arteries. 

2.  The  splenic  artery,  almost  exclusively  destined  for  the  spleen  (Fig.  367,  8). 

3.  The  superior  artery  of  the  rumen,  always  arising  from  a  very  short  trunk  common  to  it 
and  the  preceding  vessel,  is  carried  backward  to  the  superior  face  of  the  rumen,  and  from  this 
descends  between  the  two  conical  vesicae,  to  anastomose  with  the  artery  of  the  inferior  face  of 
the  viscus  (Fig.  3(;7,  2). 

4.  The  inferior  artery  of  the  rumen,  which  is  insinuated  between  the  two  anterior  culs-de-sac, 
and  afterwards  runs  along  tlie  inferior  face  of  the  organ,  passing  towards  the  notch  separating 
the  two  conical  vesicae,  to  meet  the  superior  vessels  (Fig.  367,  3). 

5.  The  artery  of  the  reticulum,  has  usually  a  common  origin  with  the  inferior  artery  of  the 
rumen,  and  passes  forward  on  tlie  left  of  the  oesophagus,  to  be  divided,  near  the  insertion  of 
that  conduit,  into  two  branches — one,  the  superior,  inclines  to  the  right  on  the  small  curvature 
of  tiie  viscus  (Fig.  367,  5);  the  other,  the  inferior,  occupying  the  fissure  separating  the  great 
curvature  of  the  reticulum  from  the  right  sac  of  the  rumen,  and  giving  to  the  latter  organ  a 
great  number  of  branches  (Fig.  367,  4). 

6.  The  hepatic  artery,  whicli  is  not  only  distributed  to  the  liver,  but  also  furnishes  a  branch 
for  the  gall-bladder,  and  a  duodenal  artery  breaking  up  into  two  branches — the  posterior 
branch  forming  with  the  first  artery  of  the  small  intestine  an  arching  anastomosis;  the  anterior 
communicating  with  the  superior  artery  of  the  omasum  and  abomasum.  Tliis  hepatic  artery 
always  originates  between  the  trunk  common  to  the  splenic  artery  and  the  superior  branch  of 
the  rumen,  and  that  which  gives  off  the  superior  branch  of  the  same  viscus  and  the  artery  of 
the  reticulum. 

42 


THE  ARTERIES. 


The  terminal  branches  of  the  coeliac  artery  comport  fliemselves  as  follows  :— 

1.  The  superior  artery  of  the  omasum  and  abomasum  passes  successively  to  the  great 
curvature  of  the  first  of  these  reservoirs,  and  to  the  concave  curvature  of  the  second  ;  then  it 
goes  beyond  the  pylorus  to  unite  with  the  duodenal  branch  of  the  hepatic  artery  by  inoscula- 
tion (Fig.  367,  6).  • 

2.  The  inferior  artery  of  the  omasuin  and  abomasum,  on  the  contrary,  passes  at  first  over 
the  small  curvature  of  the  omasum,  afterwards  the  great  curvature  of  the  abomasum,  and 
disappears  in  the  omentum,  to  which  on  its  course  it  furnishes  a  great  number  of  branches 
(Fig.  367,  7). 

In  small  Ruminants,  the  distribution  of  the  arteries  of  the  coeliac  axis  presents  some 
modifications.  We  will  cite  the  principal,  which  belong  to  the  mode  of  origin  of  the  two 
branches  destined  for  the  reticulum — these  branches  form  two  particular  vessels  which  arise 

singly   from   the   coeliiic   axis :    the 
Fig.  367.  inferior  artery  at  the  same  point  as 

.  ;  _  the  superior  artery  of  the  rumen,  the 

'*^°^^  superior  towards  the  terminal  bifur- 

cation of  the  axis. 

Anterior  mesenteric  artery. — Its 
origin  approaches  very  closely  that 
of  the  coeliac  axis.  After  a  course 
of  from  6  to  8  inches,  it  divides  into 
two  branches — an  anterior  and  a 
posterior.  The  first,  for  the  small 
intestine,  creeps  above  it,  between 
the  two  layers  of  the  mesentery,  and 
passes  backward  by  describing  a 
curve  which  gives  off  from  its  con- 
vexity— that  is,  below — a  great  num- 
ber of  branches,  analogous  in  their 
mode  of  termination  to  the  arteries 
of  the  small  intestine  in  the  Horse. 
The  posterior  branch  goes  to  the 
large  intestine,  where  it  separates 
into  two  principal  branches:  one 
wliich  passes  to  the  colon,  its  di- 
visions crossing  to  the  right,  to  be- 
hind and  below,  the  convolutions 
described  by  that  viscus;  another 
which  reaches  the  concave  curvature 
of  the  caecum,  and  anastomoses  by 
an  arch  with  the  terminal  extremity 
of  the  parent-branch  of  the  arteries 
supplying  tlie  small  intestine. 

Posterior  mesenteric  artery. — Very 
short  and  narrow. 
Renal,  spermatic,  and  small  spermatic  arteries. — These  do  not  differ  in  their  essential 
disposition  from  the  analogous  vessels  in  Solipeds. 

2.  Posterior  Aorta  in  the  Pig. 
With  the  exception  of  the  mesenteric  vessels,  the  distribution  of  which  resembles  that 
already  indicated  for  Ruminants,  and  with  the  exception,  also,  of  the  middle  sacral  artery, 
which  will  be  alluded  to  when  describing  the  internal  iliac  arteries,  all  the  branches  given  off 
by  the  posterior  aorta  comport  themselves  almost  as  in  the  Horse. 

3.  Posterior  Aorta  in  Carnivora. 

In  these  animals,  as  well  as  in  the  Pig,  the  denomination  of  posterior  aorta  is  not  justifiable, 
because  the  arteries  of  the  head  and  thoracic  limbs  spring  directly  from  the  aortic  arch. 

The  branches  of  the  aorta  are  distinguished  as  parietal  and  visceral. 

A.  Parietal  Branches. — Beyond  the  fourth  space,  the  intercostal  arteries  are  furnished 
by  the  aorta ;  the  first  is  voluminous,  and  throws  off  some  considerable  filaments  to  the  musclee 
of  the  withers.  The  first  two  lumbar  arteries  arise  from  the  thoracic  portion  of  the  aorta, 
because  of  the  very  backward  insertion  of  the  diaphragm ;  the  third  is  detached  between  the 


arteries  of  the  stomach  in  ruminants. 
1,  Coeliac  axis ;  2,  superior  artery  of  the  rumen ;  3, 
inferior  artery  of  the  rumen ;  4,  inferior  artery  of  the 
reticulum ;  5,  superior  artery  of  the  reticulum ;  6, 
superior  artery  of  the  omasum  and  abomasum ;  7, 
inferior  artery  of  ditto ;  8,  splenic  artery.  A, 
(Esophagus;  b,  left  sac  of  the  rumen;  b',  left  conical 
vesica;  c,  right  sac  of  the  rumen;  c',  right  conical 
vesica ;  D,  reticulum  ;  e,  omasum  ;  F,  abomasum ;  G, 
duodenum  ;  R,  spleen. 


THE  INTEhNAL   ILIAC  ARTERIES.  623 

two  pillars  of  that  rtrascle.  In  the  abdominal  cavity,  close  to  the  anterior  mesenteric,  the  aorta 
gives  ciff  a  branch  that  soon  divides  into  two:  one  is  diaphragmatic,  and  descends  on  the 
])Oaterior  face  ot  that  muscle;  the  other  reaches  the  sublumbar  region,  passes  over  the  psoas 
muscle,  and  traverses  the  abdominal  wall  in  the  vicinity  of  the  transverse  processes  of  the 
lumbar  vertebrje.     We  will  speak  presently  of  the  middle  sacral. 

B.  Visceral  Branches. — I  have  not  found  in  the  Dog  any  special  bronchial  arteries ;  but 
there  are  four  or  five  oisophageal  arteries  that  arise  from  different  points  of  the  tlioracic  aorta  ; 
they  descend  into  the  mediastinum,  to  the  right  and  left  of  the  oesophagus,  to  which  they  are 
distributed.     They  furnish  branches  that  accompany  the  bronchi  and  enter  the  lungs. 

The  coeliac  axis  is  again  divided  into  three  branches,  as  follows  :  The  gastric,  or  stomachic 
coronary  artery,  does  not  divide  into  two  branches  (anterior  and  posterior  gastric)  as  in  Solipeds. 
Near  its  origin  it  furnishes  a  pancreatic  branch  ;  then  it  expends  itself  in  a  great  number  of 
filaments  that  are  spreail  over  the  posterior  face  and  great  tuberosity  of  the  stomach,  or  over 
its  anterior  face  after  crossing  the  small  curvature. 

The  splenic  artery  reaches  the  spleen  at  the  middle  of  its  upper  border.  It  gives  on  its 
course :  1.  A  splenic  branch  that  enters  the  upper  extremity  of  that  organ.  2.  The  left  gastro- 
omental.  The  hepatic  artery  provides  the  principal  hepatic  vessel  at  the  posterior  fissure  of 
the  liver ;  it  is  then  continued  by  the  right  gastro-oraental  artery.  On  the  duodenum,  the 
latter  gives  origin  to  the  pyloric  and  the  pancreatico- duodenal  branches ;  the  latter  is  volu- 
minous, is  lodged  in  the  substance  of  the  pancreas,  and  anastomoses  by  its  last  filaments  with 
the  anterior  mesenteric. 

The  anterior  mesenteric  artery  arises  in  the  vicinity  of  the  coeliac  axis ;  it  forms  a  curve 
with  the  convexity  backward,  and  anastomoses  by  its  extremity  with  the  pancreatico-duodenal 
branch  of  the  hepatic.  From  its  convexity  are  detached  several  filaments  (filaments  to  the 
small  intestine),  that  form  arches  towards  the  smaller  curvature  of  that  viscus.  Behind,  and 
at  a  short  distance  from  its  origin,  it  gives  a  branch  to  the  caecum  and  branches  to  the  colon ; 
the  latter  are  sometimes  large. 

The  posterior  mesenteric  commences  near  the  termination  of  the  aorta,  and  divides  into  two 
branches— one  passing  forward,  the  other  backward;  they  form  the  hsemorrboidal  vessels 
(see  Fig.  290). 

There  is  nothing  special  to  note  with  regard  to  the  renal  ami  spermatic  arteries. 

Comparison  of  the  Aoeta  of  Man  with  that  of  Animals. 

The  aorta  in  Man  offers  the  same  general  arrangement  as  in  the  Carnivora,  the  trunk 
being  inflected  across,  to  be  placed  along  the  body  of  the  dorsal  and  first  lumbar  vertebrai, 
where  it  terminates  in  the  iliac  vessels. 

It  furnishes  the  coronary  arteries,  the  arteries  of  the  head  and  thoracic  limbs — which  will 
be  noticed  hereafter ;  ami  the  parietal  and  visceral  branches  to  the  chest  and  abdomen.  At 
first  these  are  the  intercostals,  beyond  the  third  space ;  the  diaphragmatic  arteries,  superior 
and  inferior  according  as  they  occupy  one  or  other  face  of  the  diaphragm ;  and,  lastly,  the 
lumbar  arteries. 

Among  the  visceral  branches  are  distinguished  :  1.  The  bronchial  arteries,  two  in  number; 
the  left  arises  from  the  concavity  of  the  aortic  arch,  and  enters  the  lungs  with  the  left  bronchus ; 
the  right  originates  alone  or  in  common  with  the  preceding,  and  enters  on  the  right  bronchus. 
2.  The  oesophageal  arteries,  disposed  somewhat  as  in  the  Dog.  3.  The  coeliac  trunk,  tlie 
distribution  of  which  is  nearly  identical  with  tlmt  of  the  Carnivora.  4.  The  superior  or  great 
mesenteric,  disposed  in  arches  as  in  the  Dog  (see  Fig.  292,  9).  Its  last  branches  pass  to  the  caecum, 
and  the  ascending  and  origin  of  the  transverse  portion  of  the  colon.  5.  The  inferior  or  small 
mesenteric,  which  arises  from  1|  to  2  inches  from  the  bifurcation  of  the  aorta ;  this  artery  descends 
into  the  meso-colon,  and  terminates  on  the  sides  of  the  rectum  by  the  haemorrhoidal  vessels ; 
to  the  left,  they  emit  branches  to  the  large  intestine ;  the  first  ascend  along  the  descending 
colon,  and  anastomose  on  the  transverse  colon  with  the  right  colic  brancli  of  the  superior 
mesenteric.  6.  The  renal  and  capsular  arteries,  which  do  not  offer  important  differences.  7. 
Lastly,  the  spermatic  arteries,  which  are  remarkable  for  the  length  of  their  course,  commencing, 
as  they  do,  at  the  aorta,  a  short  distance  below  the  renal  vessels. 

Article  IIL^-Internal  Iliac  Arteries,  or  Pelvic  Trunks 
(Figs.  338,  368,  370). 

The  two  internal  iliac  arteries  represent  the  middle  or  internal  branches  of 
the  quadrifurcatiou  formed  by  the  posterior  aorta  at  its  terminal  extremity. 


624  THE  ARTERIES. 

Extending  from  the  body  of  the  last  lumbar  vertebra,  to  near  the  terminal 
insertion  of  the  small  psoas  muscle,  in  an  oblique  direction  downwards,  outwards, 
and  backwards,  the  arteries  are  related  -.  in  front,  with  the  trunks  of  the  common 
iliac  veins,  which  separate  them  from  the  external  iliacs  ;  inwards,  to  the  peri- 
toneum ;  above  and  outwards,  to  the  sacro-iliac  articulation  and  to  the  ilium. 

In  its  course,  the  internal  iliac  artery  emits  the  following  branches  :  the 
nmbilical  artery,  artery  of  the  ImJh,  ileo-lumbar  yluteal,  and  subsacral  arteries.  At 
its  terminal  extremity,  it  is  divided  into  two  branches  which  ride  on  the  superior 
border  of  the  tendon  belonging  to  the  small  psoas  muscle — the  one  within,  the 
other  without  that  tendon.  The  first  is  the  ohturator  artery,  the  second  the 
ileo-femoral  artery.  All  these  branches  will  be  studied  in  the  order  of  their 
enumeration. 

Preparation  of  the  internal  iliac  artery. — Place  the  subject  in  the  first  position  ;  remove  one 
of  the  posterior  limbs,  leaving  the  rectum  and  bladder  in  the  pelvis,  and  slightly  inflating  the 
latter  organ.  Dissect,  on  the  side  from  wliich  the  limb  has  been  removed,  the  origin  and 
visceral  ramifications  of  the  branches  furnished  by  the  trunk  of  the  artery.  Follow,  on  the 
opposite  side,  the  ramifications  given  off  by  these  branches  to  the  muscles.  To  conveniently 
prepare  the  coccygeal  arteries,  it  is  necessary,  after  removing  the  great  sciatic  ligament  and 
dissecting  the  internal  artery  of  tlie  bulb  along  with  the  subsacral  trunk,  to  raise  up  the 
rectum  and  bladder  by  means  of  the  chain-hooks. 

1.  Umbilical  Artery  (Figs.  368,  5  ;  370,  3). 

This  artery  forms  a  considerable  vessel  during  foetal  life,  and  carries  the  blood 
of  the  foetus  to  the  placenta  ;  it  will  be  described  in  detail  in  the  anatomy  of  the 
foetus. 

In  the  adult  it  is  almost  entirely  obliterated,  appearing  only  as  a  fibrous  cord 
extending  from  the  internal  iliac  artery  co  the  fundus  of  the  bladder,  and  placed 
at  the  free  margin  of  the  lateral  serous  fold  detached  from  the  fundus  of  that 
organ.  This  cord  throws  off  on  its  track  one  or  more  vesical  branches,  beyond 
which  its  canal  altogether  disappears.  These  vesical  branches  also — though  very 
rarely — come  from  the  internal  pudic  artery  ;  in  which  case  the  obliteration  of  the 
umbilical  artery  is  complete. 

2.  Internal  Pudic  Artery,  or  Artery  of  the  Bulb  (Figs.  368,  16  ;  370,  4) 

This  vessel  differs  in  its  distribution  in  the  male  and  female. 

Internal  Pudic  Artery  in  the  Male. — It  proceeds  from  the  internal  iliac, 
near  the  origin  of  that  vessel,  by  a  trunk  common  to  it  and  the  umbilical  artery  ; 
it  is  then  directed  backwards,  following  the  superior  border  of  the  pyriformis 
muscle,  and  placed  either  without  or  within  the  texture  of  the  sacro-sciatic  liga- 
ment. Arrived  at  the  neck  of  the  bladder,  it  enters  the  pelvic  cavity,  lying  beside 
the  prostate  and  Cowper's  glands,  and  is  finally  inflected  downwards,  passing 
round  the  ischial  arch  to  reach  the  bulb  of  the  urethra. 

In  its  progress  it  furnishes  : 

1.  Insignificant  ramuscules  to  the  muscle  adjoining  the  sacro-sciatic  ligament. 

2.  The  vesico-prostatic  artery  (Figs.  338,  8  ;  368,  17).  This  is  a  branch  con- 
stant in  its  distribution,  but  variable  in  its  origin.  Destined  to  supply  the  pros- 
tate gland,  vesiculffi  seminales,  the  pelvic  dilatation  of  the  vas  deferens  and  the 
canal  itself,  as  well  as  the  bladder,  it  usually  commences  near  the  prostate  gland, 
and  passes  backwards,  in  a  flexuous  manner,  on  the  vesiculse  seminales  and  the 
vas  deferens. 


TEE  INTERNAL  ILIAC  ARTERIES.  625 

3.  Slender  ramifications  for  the  pelvic  portion  of  the  urethral  canal,  Cowper's 
glands,  the  anus,  and  the  erector  penis  muscle. 

The  terminal  extremity  of  the  vessel  is  insinuated  beneath  the  accelerator 
urinaB  muscle,  and  immediately  divides  into  a  multitude  of  ramuscules  which 
enter  the  erectile  tissue  of  the  urethral  bulb,  where  they  comport  themselves  as  in 
all  tissues  of  this  kind. 

Varieties. — It  is  not  rare  to  see  this  artery  detach — before  reaching  Cowper's 
gland — the  cavernous  artery.,  which  then  passes  round  the  ischial  arch  along  with 
the  nerve  of  the  penis.  Sometimes  it  only  gives  off  the  posterior  dorsal  artery  of 
the  penis — a  branch  of  the  cavernous. 

Internal  Pudic  Artery  in  the  Female.  (Fig.  370,  4.) — This  artery  ter- 
minates, towards  the  vagina,  by  rectal,  vulvar,  vaginal,  and  bulbar  branches  ; 
the  latter  are  for  the  bulb  of  the  vagina.  As  in  the  male,  it  does  not 
give  off  more  than  one  important  branch  on  its  course  ;  this — the  vaginal  artery 
(Fig.  370,  .5) — is  analogous  in  every  respect  to  the  vesico-prostatic  artery ;  its 
terminal  divisions  go  not  only  to  the  middle  portion  of  the  vagina,  but  also  to 
the  body  of  the  uterus,  where  they  anastomose  largely  with  the  branches  of  the 
uterine  artery,  and  even  pass  to  the  bladder  and  rectum. 

The  internal  pudic  artery  of  the  female,  as  in  the  male,  is  liable  to  numerous 
variations.  It  may  furnish  the  cavernous  artery,  or  only  the  dorsal  artery  of  the 
clitoris.     We  have  seen  the  vaginal  artery  come  from  the  umbilical. 

3.  Lateral  Sacral  or  Subsacral  Artery  (Figs.  368,  12  ;  370,  6). 

Rising  from  the  inner  side  of  the  internal  iliac  artery,  at,  or  a  little  behind 
the  lumbo-sacral  articulation,  lying  above  the  peritoneum,  and  beneath  the 
sacral  foramina  and  the  large  nerves  passing  through  them,  this  vessel  is  directed 
backwards,  and  arrives  near  the  posterior  extremity  of  the  sacrum,  where  it  ends 
in  two  branches  :  the  ischiatic  and  lateral  coccygeal  arteries^  to  which  must  be 
added  the  middle  coccygeal  artery,  usually  given  off  by  the  vessel  of  the  right 
side. 

Collateral  Branches. — The  lateral  sacral  artery  sends  off  on  its  course 
several  insignificant  ramuscules  destined  for  the  neighbouring  parts,  and  four 
spinal  branches  which  enter  the  spinal  canal  by  the  inferior  sacral  foramina,  and 
leave  it  again  by  the  superior,  after  throwing  off  some  divisions  to  the  posterior 
extremity  of  the  spinal  cord  and  the  cauda  equina  nerves  ;  these  branches  ramify 
in  the  muscles  lying  along  the  sacral  spine. 

Terminal  Branches. — 1.  Ischiatic  Artery.— It  crosses  the  sacro-sciatic 
ligament,  to  place  itself  under  the  superior  extremity  of  the  posterior  portion 
of  the  superficial  gluteus,  passes  backwards  and  downwards,  and  divides  into 
several  branches  which  descend  into  the  substance  of  the  semimembranosus  and 
semitendinosis  muscles,  to  beneath  the  ischial  tuberosity.  These  branches 
anastomose,  by  their  extremities,  with  the  ascending  branches  from  the  femoro- 
popliteal,  as  well  as  with  the  divisions  of  the  obturator  and  deep  femoral 
arteries. 

2.  Lateral  Coccygeal  Artery.— This  vessel  represents  the  continuation 
of  the  lateral  sacral  artery,  though  not  by  its  volume — which  is  much  less  than 
that  of  the  ischiatic  artery — but  in  its  direction.  It  proceeds  from  before  to 
behind,  for  the  whole  length  of  the  coccyx,  between  the  rudimentary  vertebra  of 
that  region  and  the  compressor  coccygis,  gradually  diminishing  in  volume,  and 


626  THE  ARTERIES. 

detaching  on  its  course  a  series  of  collateral  ramuscules,  which  are  expended  in  th( 
muscles  and  integuments  of  the  tail. 

There  has  been  described  a  superior  lateral  artery,  a  branch  of  the  preceding, 
and  which  passes  between  the  erector  coccygis  and  the  superior  face  of  the 
coccygeal  vertebrfe  ;  but  this  artery  never  exists  :  the  superior  coccygeal  muscle 
receives  its  blood  by  branches  analogous  to  the  spinal  branches  of  the  intercostal, 
lumbar,  and  sacral  arteries,  and  which  emanate  from  the  lateral  coccygeal  artery 
at  each  of  the  vertebral  bodies. 

3.  Middle  Coccygeal  Artery. — The  origin  of  this  vessel  is  liable  to 
numerous  variations.  Ordinarily,  it  is  detached  from  the  right  lateral  sacral 
artery,  in  common  with  the  lateral  coccygeal  of  the  same  side.  At  other  times, 
it  escapes  from  the  lateral  at  5  or  6  inches  from  its  origin.  In  a  specimen  now 
before  us,  it  arises  nearly  from  the  middle  of  the  lateral  sacral  artery.  And  it 
may  also  proceed  from  either  the  left  sacral  or  the  corresponding  lateral  coccygeal 
artery. 

Whatever  may  be  its  point  of  emergence,  this  vessel  is  placed  beneath  the 
inferior  face  of  the  coccygeal  vertebrae,  betvveen  the  two  compressores  coccygis, 
crosses  the  suspensory  ligament  of  the  rectum,  and  extends  to  the  extremity  of 
the  coccyx,  distributing  ramuscules  to  right  and  left,  and  even  downwards. 

4.  Ilio-lumbae  or  Ilio-muscular  Artery  (Figs.  368, 14  ;  370,  8). 

Immediately  after  clearing  the  inferior  face  of  the  lateral  angle  of  the  sacrum — 
and  even  often  before — the  internal  iliac  artery  gives  off  from  its  external  side, 
and  at  a  right  angle,  the  ilio-lumbar  artery,  which  passes  directly  outwards, 
behind  the  sacro-iliac  articulation,  between  the  iliacus  muscle  and  the  bony 
surface  covered  by  it,  and  emits  divisions  that  proceed  to  the  above-named 
articulation,  as  well  as  to  the  muscles  of  the  sublumbar  region.  Near  the  angle 
of  the  haunch,  it  terminates  in  several  branches,  which  bend  upwards  on  the 
external  border  of  the  ilium,  to  penetrate  the  principal  gluteal  muscle,  or  the 
tensor  vaginte  femoris. 

5.  Gluteal  Artery  (Figs.  368,  13  ;  370,  7). 

This,  the  most  voluminous  of  the  branches  emanating  from  the  internal  iliac, 
arises  opposite  the  preceding,  and  from  -j^  of  an  inch  to  1;^  inches  behind  the 
lateral  sacral.  It  is  immediately  reflected  on  the  internal  border  of  the  ilium, 
and  emerges  from  the  pelvis  by  the  great  sacro-sciatic  foramen,  along  with  the 
anterior  gluteal  nerves,  dividing  into  several  branches  which  ramify  in  the  texture 
of  the  great  and  small  gluteal  muscles. 

6.  Obturator  Artery  (Figs.  368,  19  ;  370,  10). 

This  vessel,  the  origin  of  which  has  been  already  indicated,  directs  its  coui-se 
backward  and  downward,  accompanied  by  a  satellite  vein  and  nerve,  passes 
between  the  peritoneum  and  ilium  in  following  the  inferior  border  of  the  pyri- 
formis  muscle,  and  finally  insinuates  itself  beneath  that  muscle  to  make  its  exit 
from  the  pelvis  by  creeping  through  the  obturator  foramen,  after  furnishing  a 
constant  vesical  twig.  Placed  between  the  external  obturator  muscle  and  the 
inferior  face  of  the  ischium,  it  separates  into  several  branches,  the  majority  of 
which  descend  into  the  internal  crural  and  ischio-tibial  muscles,  anastomosing 
with  the  ultimate  divisions  of  the  ischiatic  and  deep  femoral  arteries.  Among 
these  branches  there  are  two  or  three  which  go  to  the  roots  of  the  penis,  and 


TEE  INTERNAL  ILIAC  ARTERIES.  627 

enter  the  erectile  tissue  of  the  corpus  cavernosum  ;  one  of  them,  more  important 
than  the  others  by  its  vohime,  is  designated  the  artert/  of  the  corpus  cavernosum. 

The  obturator  artery  sometimes  arises  from  the  external  iliac. 

Artery  of  the  Corpus  Cavernosum  (Fig.  368,  20). — This  vessel  passes 
on  the  inferior  face  of  the  ischium,  backwards  and  inwards,  reaches  the  crus  penis, 


LATERAL   VIEW   OF   THE   GENlTO-URINARr   ORGANS   IN   THE   MALE. 

1,  Abdominal  aorta  ;  2,  external  iliac  artery ;  3,  common  origin  of  the  prepubic  and  deep  femoral 
arteries ;  4,  prepubic  artery ;  5,  posterior  abdominal  artery ;  6,  external  pudic  artery ;  7, 
subcutaneous  abdominal  artery  ;  8,  anterior  dorsal  artery  of  the  penis  ;  9,  9,  anterior  and  posterior 
branches  of  that  artery ;  10,  internal  iliac  artery  ;  11,  last  lumbar  artery  ;  12,  subsacral  artery  ; 
13,  gluteal  artery;  14,  iliaco-muscular  artery;  15,  umbilical  artery;  16,  internal  pudic  artery; 
17,  its  vesico-prostatic  branch;  18,  iliaco-femoral  artery;  19,  obturator  artery  ;  20,  artery  of  the 
corpus  cavernosum;  21,  posterior  dorsal  artery  of  the  penis — a  branch  of  the  preceding;  22, 
spermatic  artery  ;  23,  posterior  mesenteric  artery,  c,  Termination  of  the  small  colon  ;  R,  rectum; 
S,  sphincter  of  the  anus  ;  I,  suspensory  ligament  of  the  penis ;  I',  suspensory  ligament  of  the 
rectum ;  V,  bladder  ;  m,  ureter  ;  T,  testicle  ,  E,  epididymis ;  D,  deferent  canal ,  v,  vesiculae 
seminales;  p,  prostate  ;  p,  Cowper's  gland;  r,  crus  penis  ;  s,  ligament  of  the  corpus  cavernosum. 

and  pierces  it  by  several  branches,  after  supplying  some  muscular  divisions  and 
the  posterior  dorsal  artery  of  the  penis. 

The  latter  is  situated  on  the  dorsal  margin  of  the  penis,  passes  forward 
between  the  two  ligaments  attaching  that  organ  to  the  symphysis  pubis,  and 
proceeds  to  anastomose  with  the  posterior  branch  of  the  anterior  dorsal  artery 
(Fig.  368,  21). 

7.  Iliaco-femoeal  Aetery  (Figs.  368,  18  ;  370,  9). 
Noticed  as  one  of  the  terminal  branches  of  the  pelvic  trunk,  the  iliaco-femoral 
artery  only  exists  as  a  vessel  of  a  certain  volume  in  SoUpeds.     In  other  animals, 


628  TEE  ARTERIES. 

as  in  Man,  it  is  merely  an  insignificant  and  innominate  branch  of  the  obturator 
artery.  It  proceeds  outside  the  tendon  of  the  small  psoas  muscle,  between  the 
ihacus  and  the  neck  of  the  ilium,  which  it  passes  round  obliquely,  above  the  origin 
of  the  rectus  femoris  muscle,  to  descend  on  the  external  side  of  the  latter,  and 
plunge  into  the  mass  of  the  patellar  muscles,  entering  them  between  the  rectus 
femoris  and  vastus  externus,  after  sending  some  branches  to  the  psoas  and  gluteal 
muscles,  and  tensor  vaginse  femoris. 

Differential  Characters  in  the  Internal  Iliac  Arteries  of  the  other  Animals. 
1.  Internal  Iliac  Arteries  of  Ruminants. 

The  terminal  extremity  of  the  aorta,  after  giving  ofif  the  external  iliac  arteries,  bifurcates 
to  constitute  the  internal  iliacs,  and  in  the  angle  of  bifurcation  throws  out  a  very  large  branch 
— the  sacra  media — from  which  emanate  the  arteries  of  the  tail.  This,  however,  is  not  the 
only  important  peculiarity  to  be  noted  in  the  disposition  of  the  pelvic  arteries.  The  internal 
iliac  artery  emits  at  its  origin  a  very  short,  but  very  large  branch,  which  divides  to  form  the 
umbilical  artery,  and  an  enormous  uterine  artery,  that  supplants,  to  a  great  extent,  the  utero- 
ovarian  artery  ;  it  is  then  directed  backwards,  on  the  internal  face  of  the  great  sacro-sciatic 
ligament,  crossing  the  direction  of  the  lumbo-sacral  plexus.  In  its  course  it  furnishes  branches 
resembling  the  iliaco-muscular,  the  gluteal,  and  the  ischiatic,  and  is  continued  about  the  middle 
of  the  pelvis  by  the  internal  pudic  artery,  which  terminates  by  forming  the  dorsal  artery  of  the 
clitoris,  after  distributing  branchi  s  to  the  rectum  and  the  genito-urinary  organs  lodged  in  the 
pelvic  cavity. 

It  will  be  seen  from  this  description — which  refers  only  to  female  animals,  but  is  easily  appli- 
cable to  males — that  no  mention  is  made  (if  an  iliaco-femoral  or  obturator  artery.  This  is 
because  these  two  vessels  are  entirely  absent  in  the  Sheep,  and  the  last,  though  present  in  the 
larger  Ruminants,  is  yet  in  a  very  rudimentary  state,  butli  lieing  supplemented  by  the  deep 
femoral,  the  dimensions  of  which  are  considerable.  Neitlier  is  the  lateral  sacral  artery  described, 
as  it  is  also  absent,  its  ischiatic  branch  coming  directly  from  the  pelvic  trunk,  and  its  coccygeal 
divisions  being  supplied  by  the  middle  sacral  artery. 

2.  Internal  Iliac  Arteries  of  the  Pig. 

Two  single  branches,  originating  one  above  the  other,  arise  from  the  extremity  of  the  aorta, 
between  the  two  internal  iliac  arteries  ;  one  divides  almost  at  once  into  two  lateral  branches, 
which  go  to  right  and  left  beneath  the  iliacus,  and  are  the  representatives  of  the  iliaco-muscular 
arteries  of  the  Horse  ;  the  other,  or  sacra  media,  placed  in  the  midd'le  line,  proceeds  backwards 
on  the  inferior  face  of  the  os  sacrum,  and  constitutes  the  coccygeal  arteries  after  giving  off,  at 
about  1^  inches  from  its  origin,  two  lateral  branches,  traces  of  the  lateral  sacred  arteries,  which 
furnish  the  spinal  ramuscules  of  the  sacral  region. 

The  internal  iliac  artery,  near  its  origin,  sends  off  the  umbilical  artery,  is  directed  back 
towards  the  sacro-sciatic  furamen,  there  detaches  gluteal  brandies,  and  is  prolonged  beyond 
the  foramen  to  the  external  surface  of  the  sacro-sciatic  ligament,  in  forming  the  internal  pudic 
artery. 

The  latter  emits,  before  leaving  the  pelvic  cavity,  a  long  hemorrhoidal  artery,  that  creeps 
back  by  the  side  of  the  rectum,  to  be  distributed  to  the  posterior  extremity  of  tliat  intestine 
and  the  adjoining  genito-urinary  organs.  Outside  the  pelvis,  it  gives  off  some  gluteal  branches, 
the  most  considerable  and  posterior  of  which  represent  the  ischiatic  artery  of  Solipeds.  It  then 
re-enters  the  cavity  of  the  pelvis,  and  terminates  at  the  base  of  the  penis  by  forming  the 
cavernous  and  dorsal  arteries  of  that  organ. 

3.  Internal  Iliac  Arteries  of  Carnivora. 

The  internal  iliac  a^-teries  in  the  Carnivora  result  from  tlie  bifurcation  of  an  arterial  trunk 
that  prolongs  the  aorta  beyond  the  origin  of  the  external  iliacs,  as  far  as  the  first  intersacral 
articulation. 

This  pelvic  trunk  at  first  gives  off  the  umbilical  artery,  wliich  is  remarkable  for  its  small 
calibre,  and  the  flexuosities  it  describes  before  reaching  the  bladder. 

Then  the  internal  iliac  artery  courses  for  1  or  1.^  inches  behind,  and  to  the  inside  of,  the 
pelvi-crural  venous  trunk,  dividing  into  two  branches  at  the  entrance  to  the  pelvis. 

One  of  these  branches  goes  towards  the  viscera  contained  in  the  pelvic  cavity;  this  is  the 
inttrnal  pudic  artery.     It  passes  backwards,  turns  round  the  ischial  arch,  and  terminates  in  the 


THE  EXTERNAL   ILIAC  ARTERIES. 


cavernous  and  dorsal  arteries  of  the  penis,  after  furnishing  vesical,  hsemorrhoidal,  and  urethral 

branches,  as  well  as  the  uterine  artery  (iu  the  female).     The  latter  is  very  voluminous,  and  is 

placed  in  the  substance  of  the  broad  ligament,  above  the  small  curvature  of  the  uterine  cornu, 

■whence  it  is  directed  forward  to  the  ovary,  where 

it  meets  the  utero-ovarian  artery,  after  emitting  Fig.  369. 

numerous  collateral    branches,   remarkable   for 

the  ricliness  of  the  vascular  network  they  form 

in  the  walls  of  the  uterus. 

The  second  branch  of  the  internal  iliac 
artery  resembles  the  lateral  sacral  artery  and 
its  ischiatic  branch  in  Solipeds  ;  it  escapes  from 
the  pelvic  cavity  with  the  great  sciatic  nerve, 
which  it  accompanies  to  behind  the  thigh,  where 
it  is  expended,  after  giving  off  on  its  course 
spinal  and  gluteal  twigs.  It  is  not  this  branch 
which  supplies  the  coccygeal  arteries;  these 
come,  as  in  the  Pig  and  Ruminants,  from  the 
middle  sacral  artery. 

Comparison  op  the  Internal  Iliac  Arteries 
IN  Man  with  those  op  Animals. 

The  aorta  in  Man  bifurcates  at  the  fourth 
lumbar  vertebra  to  form  the  common  iliac  arteries, 
which  descend  to  each  side  of  the  margin  of  the 
pelvis,  where  they  divide  into  two  branches — 
the  internal  and  external  iliacs. 

The  internal  iliac,  or  hypogastric  artery, 
passes  beneath  the  sacro-iliac  articulation,  and 
breaks  up  into  nine  or  eleven  branches  that  go 
to  the  walls  of  the  pelvic  cavity,  or  to  the  organs 
contained  in  it.  Their  disposition  somewhat 
resembles  that  of  Carnivora ;  in  their  distribution 
they  represent  the  various  branches  of  the  in- 
ternal iliac  of  Solipeds.  Thus  we  find:  1.  An 
umbilical  artery.  2.  The  vesico-prostafic  artery, 
resembling  the  branch  of  the  same  name  given 
off  in  tiie  Horse  by  the  internal  pudic.  3.  The 
middle  hcemorrhoidal  artery,  that  passes  to  the 
rectum  like  the  branch  of  the  internal  pudic. 
4.  The  ileo-lumhar  artery,  the  iliaco-rnuscular 
of  Solipf'ds.  5.  The  lateral  sacral  artery,  which, 
behind,  joins  the  middle  sacral  instead  of  divid- 
ing, as  in  the  Horse,  into  ischiatic  and  lateral 
coccygeal.  6.  The  obturator  artery.  7.  Gluteal 
artery.  8.  Ischiatic.  9.  Internal  pudic,  that 
terminates,  as  in  animals,  by  the  cavernous, 
dorsalis  penis,  and  the  transversa  perinei  arte- 
ries. The  arterial  branches  of  the  rectum,  or 
inferior  hamorrhoidal,  are  furnished  by  the  in- 
ternal pudic  artery. 

Article  IV. — External  Iliac  Arteries,  or  Crural  Trunks  (Fig.  370,  11). 
These  external  branches  of  the  terminal  quadrifurcations  of  the  posterior 
aorta  descend  on  the  sides  of  the  entrance  to  the  pelvic  cavity,  in  describing  a 
curve  downwards  and  forwards,  and  an  oblique  direction  downwards,  backwards, 
and  outwards.  Maintained  within  the  psoas  parvus  and  iliacus  muscles  by  the 
peritoneum  covering  them,  they  are  bordered  posteriorly  and  inwardly  by  the 
iliac  vein,  which  isolates  them  from  the  pelvic  trunk.  When  they  arrive  at 
the  anterior  border  of  the  pubis,  in  the  interstice  separating  the  pectineus  from 


ABDOMINAL    AORTA,    WITH    ITS    BRANCHES,    IN 
MAN. 

1,  Phrenic  arteries  ;  2,  coeliac  axis  ;  3,  gastric 
artery;  4,  hepatic  artery,  dividing  into  right 
and  left  hepatic  branches;  5,  splenic  artery, 
passing  outwards  to  the  spleen  ;  6,  supra- 
renal artery  of  right  side  ;  7,  right  renal 
artery  longer  than  the  left,  passing  outward 
to  right  kidney ;  8,  lumbar  arteries ;  9, 
superior  mesenteric  artery  ;  10,  the  two 
spermatic  arteries;  11,  inferior  mesenteric 
artery;  12,  sacra  media  ;  13,  common  iliacs  ; 
14,  right  internal  iliac;  15,  e.xternal  iliac; 
16,  epigastric  artery ;  17,  circumflexa  ilii ; 
18,  common  femoral  artery,  dividing  into 
superficial  and  deep  femoral. 


630 


DISTRIBUTION   OF   THE   EXTERNAL    AND    INTERNAL   ILIAC   ARTERIES   IN   THE   MARE. 

1,  Posterior  aorta ;  2,  internal  iliac  artery ;  3,  common  origin  of  the  internal  pudic  and  tha 
umbilical  arteries  (the  latter  is  cut)  ;  4,  internal  pudic  artery  ;  5,  vaginal  artery ;  6,  lateral 
I  sacral  artery ;  7,  origin  of  the  gluteal  artery,  which  arises  in  this  instance  from  the  lateral 
sacral — a  circumstance  most  frequently  observed  in  the  Ass;  8,  origin  of  the  ilio-lumbar  artery; 
9,  origin  of  the  iliaco-femoral  artery;  10,  obturator  artery;  11,  external  iliac  artery;  12, 
circumflex  iliac  artery  (cut);  13,  femoral  artery;  14,  common  origin  of  the  deep  femoral  and 
prepubic  arteries;  15,  origm  of  the  anterior  great  muscular  artery;  16,  origin  of  the  saphena 
artery  (cut)  ;  17,  innominate  branch  ;  18,  popliteal  artery ;  19,  femoro-popliteal ;  20,  satellite 
artery  of  the  great  femoro-popliteal  nerve  ;  21,  posterior  tibial  artery  ;  22,  its  communicating 
branch  with  the  saphena;  23,  external  plantar  artery;  24,  satellite  artery  of  the  internal  plantar 
nerve  ;  25,  digital  artery. 


THE  EXTERNAL   ILIAC  ARTERIES.  631 

the  sartorius  muscles,  each  is  prolonged  to  the  thigh,  and  takes  the  name  of 
femoral  artery;  and  thence  into  the  angle  of  the  femoro-tibial  articulation, 
where  it  receives  the  designation  of  popliteal  artery. 

Before  passing  to  the  description  of  these  two  vessels — continuations  of  the 
external  iliac  artery — we  will  indicate  the  collateral  branches  which  emanate 
from  this  artery  itself.  These  are  two  principal — the  small  testicular,  or 
artery  of  the  cord,  or  uterine,  and  the  circumfiex  iliac .  The  first  having  been 
already  described  (p.  620),  we  have  only  to  notice  the  second. 

Circumflex  Iliac  Artery  (Fig.  366,  11). — This  artery  commences  at  an 
acute  angle  near  the  origin,  and  in  front  of,  the  external  iliac  ;  it  sometimes 
emerges  directly  from  the  posterior  aorta.  It  is  directed  outwards,  passes 
between  the  peritoneum  and  the  lumbo-iliac  aponeurosis,  and  arriving  at  the 
external  border  of  the  psoas  magnus  muscle,  or  even  beyond  that,  it  bifurcates. 
The  anterior  branch  sends  its  ramifications  into  the  transverse  and  small  oblique 
muscles  of  the  abdomen,  where  they  anastomose  with  the  abdominal  ramuscules 
of  the  lumbar  and  intercostal  branches  ;  the  posterior  Ufurcation,  after  giving 
some  vessels  to  the  same  muscles,  traverses  the  abdominal  wall  a  little  below  the 
external  angle  of  the  ilium,  in  passing  between  the  small  oblique  and  iliacus 
muscles,  to  descend  within  the  anterior  border  of  the  tensor  fascia  lata  muscle, 
and  expend  itself  in  front  of  the  thigh  by  subcutaneous  divisions. 

Femoral  Artery  (Fig.  370,  13). 

The  femoral  artery,  a  prolongation  of  the  external  iliac,  which  changes  its 
name  on  leaving  the  anterior  border  of  the  pubis,  at  first  lies  beneath  the  crural 
arch,  beside  a  cluster  of  lymphatic  glands,  in  the  space  comprised  between  the 
pectineus,  sartorius,  and  iliacus  muscles.  From  this  interstice  it  descends, 
accompanied  by  its  satellite  vein,  which  lies  behind  it,  and  the  internal  saphena 
nerve,  along  the  pectineus  and  vastus  internus,  at  the  posterior  border  of  the 
sartorius.  It  soon  leaves  that  muscle,  however,  to  traverse  the  ring  formed  by 
the  two  branches  of  the  adductor  magnus  and  the  oblique  concavity  on  the 
posterior  face  of  the  femur,  and  reaches  the  superior  extremity  of  the  gastroc- 
nemius, between  which  it  is  continued,  and  where  it  assumes  the  name  of 
popliteal  artery. 

On  its  course  the  femoral  artery  distributes  a  certain  number  of  collateral 
branches  to  the  adjacent  parts.  These  are  :  the  prepuhic,  deep  muscular,  super- 
ficial muscular,  the  small  muscular,  and  saphena  arteries. 

Preparation. — The  animal  being  placed  in  the  first  position,  and  the  limb  raised,  the  skin 
is  carefully  removed  from  the  inner  face  of  the  thigh,  the  external  generative  organs  in  the 
Inguinal  region,  and  tlie  inferior  abdominal  wall.  The  sapliena  vein  is  first  to  be  exposed,  and 
the  branches  of  the  artery  of  that  name  dissected ;  next,  the  prepubic  artery,  which  is  to  be 
sought  for  in  the  inguinal  canal,  atid  its  branches  prepared  by  dissecting  from  tlieir  origin  to 
their  termination.  The  excision  of  a  portion  of  the  adductors  of  the  leg  and  the  great 
adductor  of  the  thigh  will  sufficiently  expose  the  femoral  artery  and  its  other  collateral 
branches. 

1.  Prepubic  Artery  (Fig.  368,  4). 

This  artery  originates  at  the  artificial  line  of  demarcation  separating  the 
external  iliac  from  the  femoral  artery,  at  the  superior  extremity  of  the  latter. 
It  therefore  emerges  from  that  vessel  at  the  anterior  border  of  the  pubis,  and 
never  alone,  but  always  with  the  deep  muscular  branch,  by  means  of  a  common 


632  TEE  ARTEBIES. 

and  generally  very  short  trunk,  which  springs  at  an  acute  angle  from  uhe  inner 
side  of  the  femoral  artery. 

The  prepubic  artery  traverses  the  crural  ring,  opposite  which  it  arises  ;  it  lies 
on  the  anterior  face  of  Poupart's  hgament,  behind  the  neck  of  the  inguinal  canal, 
and  after  a  very  short  course  separates  into  two  branches — the  posterior  abdominal 
and  the  external  pudic  arteries. 

Posterior  Abdominal  Artery  {Epigastric  of  Man)  (Fig.  368,  5). — This 
leaves  the  external  pudic  artery  at  an  acute  angle,  enters  the  femoral  ring  by 
crossing  the  direction  of  the  spermatic  cord,  places  itself  between  the  small 
oblique  and  transverse  muscles  of  the  abdomen,  passes  forward  along  the  external 
border  of  the  rectus  abdominis,  and  finally  enters  the  substance  of  that  muscle, 
where  its  terminal  divisions  anastomose  with  those  of  the  anterior  abdominal 
artery.  The  numerous  collateral  branches  this  artery  throws  off  on  its  track 
principally  go  to  the  rectus  muscle,  or  the  other  parts  composing  the  inferior 
abdominal  wall,  the  skin  included  ;  the  superior  branches  communicate  with  the 
circumflex  iliac. 

The  position  this  artery  occupies  at  its  origin,  with  reference  to  the  abdominal 
ring,  is  worthy  of  remark  ;  indicating,  as  it  does,  that  in  strangulated  inguinal 
hernia,  division  of  the  ring  should  be  made  outwards,  to  avoid  wounding  the 
vessel. 

External  Pudic  Artery  (Fig.  368,  6). — This  artery  descends  at  first  on 
the  posterior  wall  of  the  inguinal  canal,  behind,  and  a  little  to  the  inside  of,  the 
spermatic  cord  ;  then,  having  passed  the  external  ring  of  the  canal,  it  bifurcates 
into  the  subcutaneous  abdomincd  artery,  and  the  anterior  dorsal  artery  of  the  penis. 

The  subcidaneons  abdomincd  artery  is  directed  forward  on  the  superficial 
face  of  the  abdominal  fascia,  bordering  in  its  course  the  insertion  of  the  sus- 
pensory Hgament  of  the  sheath.  Arriving  at  the  anterior  extremity  of  that 
ligament,  it  terminates  in  several  subcutaneous  divisions,  one  of  which  is 
inflected  beyond  the  umbilicus  to  anastomose  in  a  circle  with  a  similar  branch 
from  the  opposite  artery.  It  gives  off  twigs  to  the  scrotum,  sheath,  superficial 
inguinal  glands,  skin,  etc.  (Fig.  368,  7). 

The  anterior  dorsal  artery  of  the  penis  gains  the  superior  border  of  that 
organ,  after  supplying  one  or  two  scrotal  branches,  and  separates  into  two 
portions ;  one,  posterior,  meets  the  dorsal  cavernous  artery  of  the  penis  and 
anastomoses  with  it ;  the  other,  anterior,  longer,  more  voluminous,  and  very 
flexuous  during  retraction  of  the  penis,  follows  the  dorsal  border  of  the  organ 
to  its  anterior  extremity,  where  it  enters  the  erectile  tissue  of  this  part.  From 
the  two  branches  of  this  anterior  dorsal  artery,  there  are  given  off,  as  in  the 
posterior  one,  ramuscules  which  penetrate  the  corpus  cavernosum  and  the  walls 
of  the  urethra  ;  they  give,  besides,  some  preputial  twigs  (Fig.  368,  8). 

In  the  female,  the  external  pudic  artery  offers  a  disposition  which,  if  not 
similar,  is  yet  analogous  to  that  just  indicated.  As  in  the  male,  this  vessel 
traverses  the  inguinal  canal,  and  after  leaving  it  divides  into  two  branches  : 
one,  the  anterior,  or  suhcidaneous  abdomincd  artery ;  the  other,  the  posterior,  or 
mammary  artery.  The  last — the  most  voluminous — represents  -the  dorsal  artery 
of  the  penis.  It  distributes  several  branches  to  the  mammary  tissue,  and  is 
prolonged  between  the  thighs  by  a  perineal  branch,  which  terminates  in  the 
inferior  commissure  of  the  vulva,  after  giving  off  glandular  and  cutaneous 
branches. 


the  external  iliac  arteries.  633 

2.  Profunda  Femoris,  Great  Posterior  Muscular  Artery  of  thb  Thigh, 
OR  Deep  Muscular  Artery  (Fig,  370,  14) 

Arising  in  common  with  the  prepubic  artery,  the  profunda  femoris  passes 
backward,  penetrates  between  the  ihacus  and  the  pectineus  muscles,  afterwards 
between  the  latter  and  the  external  obturator  muscle.  In  this  way  it  arrives 
beneath  the  deep  face  of  the  adductors  of  the  thigh,  when  it  becomes  inflected 
behind  the  femur,  and  disappears  in  the  substance  of  the  internal  and  posterior 
crural  muscles  by  ascending  branches,  which  anastomose  with  the  ischiatic  artery, 
and  descending  and  internal  branches,  the  terminal  ramifications  of  which  open 
mto  those  of  the  obturator  artery. 

The  principal  twigs  of  the  coxo-femoral  articulation  are  derived  from  this 
vessel. 

3.  SupERFicuLis  Femoris,  Superficial  Muscular  or  Great  Anterior 
Muscular  Artery  (Fig.  370,  15). 

Smaller  than  the  preceding,  and  commencing  opposite  to  it,  but  a  little 
lower,  this  artery  passes  downwards,  outwards,  and  forwards,  runs  between  the 
sartorius  and  the  musculo-tendinous  cone  which  terminates  in  common  the  psoas 
magnus  and  iliacus,  furnishes  some  ramuscules  to  these  muscles,  dips  into  the 
interstice  separating  the  vastus  internus  from  the  rectus  femoris,  and  is  lost  in 
the  mass  of  the  triceps  cruris. 

This  vessel,  therefore,  resembles  the  iliaco-femoral  artery,  which  enters  this 
triceps  by  penetrating  between  the  rectus  femoris  and  the  vastus  externus. 

4.  Innominate  or  Small  Muscular  Arteries. 

The  femoral  artery  gives  off  on  its  course  numerous  small  branches  to  the 
neighbouring  muscles,  though  too  diminutive  to  merit  particular  description. 
One  of  these  furnishes  the  nutrieyit  artery  of  the  femur — the  largest,  perhaps, 
of  all  the  arteries  supplying  bones.  Another  (Fig.  368,  17)  sends  to  the  stifle 
a  long  articular  branch,  analogous  to  the  great  anastomoticus  of  Man,  which 
descends  along  the  vastus  internus,  beneath  the  adductors  of  the  leg,  at  the 
interstice  separating  these  two  muscles. 

5.  Saphena  Artery  (Fig.  370,  16). 

This  artery,  remarkable  for  its  small  volume,  the  length  of  its  course,  and 
its  connections  with  the  vein  of  the  same  name,  supplies  the  skin  on  the  inner 
side  of  the  thigh  and  leg. 

It  takes  its  origin,  at  an  acute  angle,  from  nearly  the  middle  of  the  femoral 
artery,  either  alone  or  in  common  with  one  of  the  principal  innominate  muscular 
branches,  and  becomes  superficial  in  passing  into  the  interstice  of  the  two 
adductors  of  the  leg,  or  in  traversing  one  of  these,  usually  the  gracilis.  It  lies 
on  the  surface  of  this  muscle,  beside  the  saphena  vein,  and  bifurcates  at  the 
angle  of  union  of  the  two  roots  which  constitute  that  vessel.  One  of  the 
branches  accompanies  the  anterior  vein  to  nearly  the  lower  third  of  the  leg  ; 
the  other  follows  the  posterior  vein,  and  usually  anastomoses  in  the  hollow  of  the 
hock,  above  the  calcis,  with  a  branch  from  the  posterior  tibial  artery,  and  which 
also  communicates  with  one  of  uhe  branches  of  the  femoro-popliteal  artery. 


THE  ARTERIES. 


Popliteal  Artery  (Fig.  370,  18). 


Preparation. — The  preparation  which  has  served  for  the  study  of  the  femoral  artery  being 
nearly  arranged  as  in  Fig.  370,  remove  from  it  the  internal  head  of  the  gastrocnemius  and 
the  popliteus  muscles. 

The  above  name  is  given  to  the  continuation  of  the  femoral  artery.  This 
vessel  follows  a  descending  direction  behind  the  femoro-tibial  articulation, 
between  the  heads  of  the  gastrocnemius  muscle,  insinuates  itself  l)eneath  the 
popliteus,  and  bifurcates  at  the  tibio-fibular  arch  after  a  course  of  from  6  to  8 
inches,  to  form  the  posterior  and  anterior  tibial  arteries. 

The  popliteal  artery  emits  on  its  track  :  1.  The  femoro-popJiteal  artery. 
2.  Articular  branches.  3.  Muscular  branches  chiefly  destined  to  the  gastroc- 
nemius muscle,  of  which  it  is  necessary  to  particularize  one  long  division  that 
descends  within  the  peiioratus,  in  company  with  the  great  femoro-popliteal 
nerve,  to  terminate  superficially  near  the  tendo-Achillis,  where  it  anastomoses 
with  a  recurrent  branch  of  the  posterior  tibial  artery  (Fig.  370,  20). 

The  femoro-popliteal  artery  is  the  only  one  of  these  collateral  branches 
deserving  particular  mention.  Its  origin  indicates  the  limit  of  the  femoral 
and  popliteal  arteries,  as  it  is  detached  at  a  right  angle  below  the  ring  of  the 
adductor  magnus,  at  the  intermediate  point  of  these  two  vessels.  Placed  between 
the  semimembranosus  and  semitendinosus  muscles  on  the  one  part,  and  the 
biceps  femoris  on  the  other,  this  vessel  is  directed  from  before  to  behind,  and 
arrives  at  nearly  the  posterior  border  of  the  buttock,  where  it  terminates  in 
subcutaneous  branches,  after  emitting  descending  and  ascending  branches. 
Among  the  first  of  these,  which  are  principally  destined  to  the  gastrocnemius 
muscle,  sometimes  exists  the  satellite  branch  of  the  sciatic  nerve,  and  a  thin 
twig  which  descends  with  the  external  saphena  nerve  into  the  hollow  of  the 
hock,  where  it  meets,  like  the  preceding,  a  branch  of  the  posterior  tibial  artery. 
Several  of  the  ascending  branches  pass  along  the  great  femoro-popliteal  nerve, 
and  all  anastomose  either  with  the  deep  femoral,  or  with  the  ischiatic  arteries  in 
the  substance  or  interstices  of  the  ischio-tibial  muscles  (Fig.  370,  19). 

Terminal  Branches  of  the  Popliteal  Artery. 

1.  Posterior  Tibial  Artery  (Fig.  370,  21). 

Preparation. — Follow  the  indications  furnished  by  Fig.  370. 

At  first  situated  deeply  behind  the  tibia,  beneath  the  popliteus,  and  the 
oblique  and  deep  flexors  of  the  phalanges,  tliis  artery  descends  towards  the  hollow 
of  the  hock,  becoming  gradually  more  and  more  superficial,  and  lying  below  the 
tibial  fascia,  behind  the  tendon  of  the  oblique  flexor  muscle,  along  with  its 
satellite  vein.  Arriving  at  the  apex  of  the  os  calcis,  it  crosses  the  tibial  fascia, 
describes  an  S  curve,  and — along  with  the  sciatic  nerve — passes  beneath  the  tarsal 
arch  ;  at  the  astragalus  it  separates  into  two  terminal  branches — the  plantar 
arteries. 

GoUatoral  branches. — We  cite  :  1.  Numerous  branches  destined  to  the  posterior 
deep  tibial  muscles.  2.  The  nutrient  artery  of  the  tibia.  3.  The  tarsal  articular 
arteries,  a  principal  of  which,  along  with  a  large  venous  arch,  passes  under  the 
perforans,  near  the  inferior  extremity  of  the  tibia,  to  be  distributed  outside  the 
tarsus  in  descending  ramuscules  and  ascending  twigs,  which  extend  as  far  as  the 
gastrocnemius  and  perforatus  tendons.    4.  A  superficial  ascending  branch,  arising 


THE  EXTERNAL  ILIAC  ARTERIES.  635 

ordinarily  from  the  second  inflection  of  the  S  curvature  formed  by  the  artery 
at  its  lower  extremity,  situated  in  the  hollow  of  the  hock,  anastomosing  with  the 
saphena  artery,  as  well  as  with  the  satellite  popliteal  branch  of  the  sciatic  nerve, 
the  ramifications  of  which,  nearly  all  subcutaneous,  are  scattered  within  and 
without  on  the  sides  of  the  hock,  and  the  inferior  extremity  of  the  thigh. 

Terminal  branches. — Tlie  two  terminal  branches  of  the  posterior  tibial  artery 
are  slender  vessels— vestiges  of  the  plantar  arteries  in  Man.  Lying  on  the  outer 
side  of  the  synovial  tendinous  sheath  lining  the  tarsal  groove,  they  are  placed — 
one  within,  the  other  without,  the  perforans  tendon,  and  descend  along  with  the 
plantar  nerves  to  the  upper  extremity  of  the  metatarsus,  where  they  leave  the 
nerves,  each  to  anastomose  with  the  perforating  pedal  artery,  forming  a  kind  of 
deep  arch  across  the  upper  extremity  of  the  suspensory  hgament  of  the  fetlock 
— that  is,  from  the  post-metatarsal  fibrous  band  that  represents  the  interosseous 
plantar  muscles  of  tetradactylous  or  pentadactylous  animals. 

In  their  course,  these  plantar  arteries  only  distribute  some  insignificant 
ramuscules  to  the  tarsal  articulations. 

From  the  convexity  of  the  arch  they  form  in  uniting  with  the  perforating 
pedal  artery,  arise  four  long  descending  branches :  1.  Two  superficial,,  innominate, 
and  veiy  fine  arterioles  accompanying  the  plantar  nerves,  and  passing  by  the  side 
of  the  flexor  tendons  to  the  sesamoid  groove,  where  they  inosculate  with  the 
collaterals  of  the  digit  (Figs.  370,  23  ;  371,  8).  2.  Two  deep  branches  con- 
stituting the  plantar  interosseous  arteries,  distinguished  into  external  and  internal. 
The  first  is  only  an  extremely  fine  vascular  twig,  very  uncertain  in  its  disposition, 
and  possesses  no  other  importance  in  Solipeds  than  representing,  in  a  rudimentary 
state,  an  artery  wliich  is  of  considerable  size  in  other  animals.  Placed  within 
the  external  metatarsal  bone,  it  anastomoses,  by  its  inferior  extremity,  with  a 
branch  of  the  metatarso-pedal  artery.  The  internal  interosseous  plantar  artery 
may  be  considered,  if  we  disregard  the  study  of  analogies,  as  the  continuation  of 
the  perforating  pedal  artery,  which  it  rivals  in  volume.  It  descends  to  the 
external  side  of  the  internal  metatarsal  bone,  beneath  the  margin  of  the  suspen- 
soiy  ligament  of  the  fetlock,  and  terminates  a  little  above  the  tubercle  of  the 
external  metatarsal  bone,  in  uniting  at  a  very  acute  angle  with  the  metatarso- 
pedal  artery.  It  gives  off  on  its  track  :  the  nutrient  of  the  large  metatarsal  bone  ; 
a  small  branch  to  the  external  interosseous  artery  ;  several  ramuscules  which 
cross  the  posterior  border  of  the  internal  metatarsal  bone  to  supply  the  connective 
tissue,  the  skin,  and  the  tendons  on  the  large  metatarsal  bone. 

2.  Anterioe  Tibial  Artery  (Fig.  371,  1). 

Preparation. — Expose  the  artery  by  removing  the  anterior  muscles  of  the  leg. 

The  anterior  tibial  artery  is  the  largest  of  the  two  branches  terminating  the 
popliteal  trunk.  It  traverses  the  tibio-fibular  arch,  and,  with  its  satellite  veins, 
places  itself  on  the  anterior  aspect  of  the  tibia,  down  which  it  passes  by  following 
the  deep  face  of  the  flexor  metatarsi.  On  reaching  the  front  of  the  tibio-tarsal 
articulation,  it  loses  its  name  and  takes  that  of  the  pedal  (or  great  metatarsal) 
artery. 

The  anterior  tibial  artery  gives  off  a  great  number  of  collateral  branches, 
which  are  principally  distributed  to  the  tibial  muscles.  One  of  them,  descending 
along  the  fibula,  beneath  the  lateral  extensor  muscle  of  the  phalanges,  clearly 
represents  a  trace  of  the  peroneal  artery  of  Man. 


636  TEE  ARTERIES. 

3.  Pedal  (or  Great  Metatarsal)  Artery  (Fig.  371,  2). 

A  continuation  of  the  anterior  tibial  artery,  the  name  of  which  changes  on 
reaching  the  region  of  the  foot,  the  pedal  artery  courses  downward  over  the 
anterior  face  of  the  tibio-tarsal  articulation,  by  bending  shghtly  outwards,  and 
passing  beneath  the  cuboid  branch  of  the  flexor  metatarsi.  At  the  second  row 
of  tarsal  bones  it  divides  into  two  branches,  which  we  will  designate  the  im-foraU 
ing  pedal  (or  perforating  metatarsal),  and  the  metatar so-pedal  arteries,^  the  latter 
continued  inf  eriorly  by  the  digital  arteries,  or  collaterals  of  the  digit. 

The  collateral  branches  emanating  from  this  vessel  are  all  articular  or 
cutaneous,  and  of  no  importance.^ 

Perforating  Pedal  (Arteria  Pedis  Perforans,  Perforating  Meta- 
tarsal) Artery. — It  crosses  the  tarsus  from  before  to  behind,  by  passing — with 
a  venous  branch — into  the  canal  between  the  cuboid,  scaphoid,  and  great  cunei- 
form bones  ;  it  then  joins  the  arch  formed  by  the  anastomoses  of  the  two  plantar 
arteries — terminal  divisions  of  the  posterior  tibial  (Fig.  371,  14). 

Metatarso-pedal  or  Collateral  Artery  of  the  Cannon.^ — i\Iuch  larger 
than  the  preceding,  this  vessel  (Fig.  371,  3)  may  be  considered  as  a  continuation 
of  the  pedal  (or  great  metatarsal)  artery.  It  is  lodged  at  first  in  the  fissure 
situated  outside  the  large  metatarsal  bone,  in  front  of  the  external  metatarsal 
bone,  and  afterwards  passes  between  these  two  bones,  above  the  tubercle  termi- 
nating the  latter,  reaching  the  posterior  face  of  the  first,  between  the  two  inferior 
branches  of  the  suspensory  ligament,  above  the  sesamoid  groove,  where  the 
vessel  bifurcates  to  form  the  collateral  arteries  of  the  digit. 

The  collateral  artery  of  the  cannon  receives,  a  short  distance  above  this 
terminal  bifurcation,  the  internal  plantar  interosseous  artery. 

On  its  course  it  gives  off  :  1.  Numerous  anterior  ramuscules  for  the  connec- 
tive tissue,  tendons,  Ugaments,  and  the  skin  on  the  anterior  face  of  the  meta- 
tarsus and  fetlock.  2.  Some  slender  posterior  divisions,  one  of  which  ascends 
within  the  external  plantar  interosseous  artery,  after  furnishing  several  liga- 
mentous, tendinous,  and  cutaneous  ramuscules  in  the  posterior  metatarsal  region. 

Digital  Arteries,  or  Collateral  Arteries  of  the  Digit  (Figs.  370,  25  ; 
371,  5,  5  ;  377,  11). — Remarkable  for  their  volume,  these  arteries  carry  blood 
to  the  keratogenous  apparatus  enveloping  the  ungual  phalanx,  and  from  this 
distribution  derive  such  importance  that  they  deserve  a  detailed  study. 

'  The  vessel  we  have  here  named  the  perforating  pedal  artery,  is  only  the  like  termination 
of  tlie  same  artery  in  Man.  The  metatarso-pedal  artery  ought  to  be  regarded  as  the  represen- 
tative of  one  of  the  dorsal  iuterossei  arteries,  because  of  its  position  in  the  interstice  of  the 
middle  and  external  lateral  metatarsal  bones.  The  dorsal  interstice  of  the  inner  side  also 
lodges  an  interosseous  branch,  usually  supplied  by  the  external  plantar  artery ;  but  its  diameter 
is  so  diminished  tliat,  in  order  to  avoid  complexity  by  introducing  an  almost  useless  element 
into  the  didactic  description  of  the  posterior  tibial  artery,  we  have  thought  it  our  duty  to 
neglect  its  indication. 

*  One  of  these  may  be  regarded  as  the  analogue  of  the  dormlis  pedis  of  Man. 

'  Rigot  has  designated  this  artery — we  do  not  know  why— the  superficial  plantar  artery. 
It  would  have  been  better  to  have  allowed  it  to  retain  the  name  given  to  it  by  Girard— the 
lateral  artery  of  the  cannon.  This  is  not  the  only  instance  in  which  the  attempts  of  Rigot  to 
conform  the  nomenclature  of  the  arteries  to  that  of  anthropotoraists  has  proved  unfortunate,  as 
he  has  not  always  succeeded  in  finding  in  the  Horse  the  real  representatives  of  the  arteries  in 
Man.  The  aim  of  this  work  does  not  allow  us  to  discuss  the  vicious  determinations  and 
denominations  of  Rigot  every  time  we  meet  them.  We  are  content  to  change  them,  purely 
and  simply,  leaving  to  the  judgment  of  the  reader,  should  this  matter  interest  him,  the  task 
of  deciding  if  we  are  right. 


THE  EXTERNAL   ILIAC  ARTERIES. 


Origin. — The  digital  arteries  succeed  the  terminal  extremity  of  the  collateral 
of  the  cannon,  and  separate  from  one  another  in  forming  an  acute  angle  below 
the  sesamoidean  venous  arch, 
above  the  fetlock-joint,  between 
the  two  branches  of  the  sus- 
pensory ligament,  behind  the 
inferior  extremity  of  the  large 
metatarsal  bone,  and  in  front 
of  the  flexor  tendons  of  the 
phalanges. 

Course  and  Relations. — These 
vessels  descend — one  to  the 
right,  the  other  to  the  left,  from 
the  lateral  parts  of  the  metacar- 
po-phalangeal  (and  metatarso- 
phalangeal) articulation  to  the 
internal  face  of  the  basilar  pro- 
cess, where  they  bifurcate  to 
form  the  plantar  and  preplantar 
ungual  arteries. 

"In  the  whole  of  this  course, 
it  (the  digital  artery)  follows  the 
track  of  the  flexor  tendons,  rest- 
ing on  their  margins,  and  main- 
tained there  by  loose  connective 
tissue.  Behind,  it  is  flanked  by 
the  plantar  nerve,  which  covers 
a  portion  of  its  surface,  enlaces 
it  with  numerous  filaments,  and 
is  so  closely  associated  with  it 
in  all  its  flexuosities,  as  to  form 
but  a  single  cord  with  it. 

"  In  front,  it  is  margined, 
though  for  a  short  distance,  by 
its  satellite  vein,  which  for  the 
whole  of  its  track  rests  on  the 
lateral  faces  of  the  two  first 
phalanges. 

"  At  its  upper  part,  near 
its   origin,  and  on   the  lateral 


PRINCIPAL     ARTERIES     IN     THE      POS- 
TERIOR   FOOT    OF    THE    HORSE. 

1,  Anterior  tibial  artery;  2,  pedal  or 
great  metatarsal  artery;  3,  nieta- 
tarso-pedal  or  perforating  meta- 
tarsal ;    4,    arteria    pedis    perforans ; 

5,  5,  digital  arteries  ;  6,  6,  arterioles  of  the  ergot ;  7,  perpendicular  artery ;  8,  artery  of  the  plantar 
cushion  ;  9,  anterior  branch  of  the  coronary  circle  ;  10,  circumflex  artery  of  the  coronary  cushion  ; 
11,  preplanter  ungual  artery;  12,  inferior  circumflex  artery  of  the  foot;  13,  collateral  branch  of 
the  posterior  tibial  artery  distributed  to  the  external  surface  of  the  hock  ;  14,  arteriole  furnished 
by  the  arch  formed  by  the  union  of  the  two  plantar  arteries  with  the  arteria  pedis  perforans,  across 
the  superior  extremity  of  the  supensory  ligament  of  the  fetlock. 
43 


638  THE  ARTERIES. 

portions  of  the  metacarpo-phalangeal  articulation,  the  digital  artery  is  crossed 
from  behind  to  before  by  the  anterior  branch  of  the  plantar  nerve,  and  it  is 
covered  for  the  whole  of  its  extent  by  the  fascia  that  continues  the  proper  tunic 
of  the  plantar  cushion,  the  lateral  ligamentous  band  of  which  cuts  its  direction 
obliquely  downwards  and  forwards,  at  the  middle  portion  of  the  first  phalanx."  ^ 
Collateral  divisions. — These  are:  1.  At  the  fetlock,  numerous  fine  branches 
distributed  to  the  metacarpo-phalangeal  articulation,  but  particularly  to  the 
sesamoid  sheath  and  the  tendons  lodged  in  it. 

2.  To  the  environs  of  the  upper  extremity  of  the  first  phalanx,  slightly 
ascending  and  sometimes  voluminous  twigs,  for  the  tissue  of  the  ergot  (the  horny 
tubercle  behind  the  fetlock). 

3.  Towards  the  middle  of  the  same  bone,  the  vessel  named  by  Percivall  the 
perpendicular  artery,  and  correctly  so,  for  it  arises  at  a  right  angle  from  the 
digital  artery  to  divide  almost  immediately  afterwards  into  two  series  of  ramifi- 
cations— anterior  and  posterior.  The  anterior  branches  are  in  nearly  every 
instance  two  principal :  one  ascending,  passing  beneath  the  check-band  of  the 
extensor  tendon,  and  climbing  to  the  capsular  ligament  of  the  fetlock-joint  to 
meet  the  arterial  divisions  furnished  directly  to  that  ligament  by  the  collateral 
artery  of  the  cannon  ;  the  other  descending,  which  reaches  the  side  of  the 
second  phalanx,  Avhere  its  ramuscules  anastomose  with  the  coronary  circle  and 
the  circumflex  artery  of  the  coronary  cushion.  The  posterior  ramifications 
consist  most  frequently  of  two  principal  branches— one  ascending,  the  other 
descending ;  these  insinuate  themselves  between  the  flexor  tendons  and  the 
sesamoid  ligaments,  to  be  distributed  to  these  organs,  but  especially  to  the  syno- 
vial membrane  of  the  large  sesamoidean  bursa.  Sometimes  it  is  seen  to  arise 
alone  from  the  digital  artery.  It  must  here  be  noted,  that  the  divisions 
furnished  by  the  anterior  branches  of  this  perpendicular  artery  communicate 
with  those  of  the  opposite  side  in  front  of  the  first  phalanx,  either  above  or 
below  the  principal  extensor  of  the  digit ;  and  that  the  posterior  branches 
exhibit  a  series  of  analogous  anastomoses.  The  body  of  the  first  phalanx  is 
therefore  enveloped  on  every  side  by  an  arterial  plexus, 

4.  At  different  elevations  on  the  first  and  second  phalanges,  several  tendmous 
and  cutaneous  twigs,  which  are  of  no  importance. 

5.  The  artery  of  the  plantar  cushion,  which  arises  at  the  superior  border  of 
the  lateral  cartilage,  is  directed  obMquely  backward  and  downward,  and  placed 
within  the  posterior  border  of  that  cartilage,  to  be  distributed  to  the  middle 
portion  of  the  complementary  apparatus  of  the  third  phalanx,  as  well  as  to  the 
villous  tissue  and  the  coronet.  The  branch  expended  in  the  latter  sometimes 
proceeds  directly  from  the  digital  artery;  it  is  a  very  remarkable  vessel,  is 
inflected  from  before  to  behind,  crossing  the  posterior  border  of  the  pedal  carti- 
lage, creeping  on  the  internal  face  or  in  the  texture  of  the  skin,  a  little  above  the 
coronet,  parallel  with  that  portion  of  the  keratogenous  apparatus,  and  terminates 
by  anastomosing  with  a  branch  of  the  artery  now  to  be  noticed. 

6.  The  coronary  circle,'^  formed  by  two  transverse  branches — one  anterior,  the 
other  posterior,  springing  at  a  right  angle  from  the  digital  artery,  under  the 
cartilaginous  plate  of  the  os  pedis— passes  around  the  coronary  bone  to  meet 
the  analogous  branches  of  the  opposite  artery,  to  anastomose  with  them  directly 
and  by  inosculation.     The  coronary  circle  therefore  presents  two  distinct  por- 

'  H.  Bouley,  Traite  de  V Organisation  du  Pied  du  Cheval.     Paris,  1851. 
*  So  named  because  it  encircles  the  coronet. 


THE  EXTERNAL  ILIAC  ARTERIES.  639 

tions  :  one  posterior,  placed  above  the  superior  border  of  the  small  sesamoid, 
beneath  the  perforans  tendon  ;  the  other  anterior,  more  extensive  and  volmniaous, 
covered  on  the  sides  by  the  lateral  cartilages  of  the  foot,  and  in  its  front  or 
middle  part  by  the  expansion  of  the  anterior  extensor  tendon  of  the  phalanges. 

The  collateral  ramuscules  furnished  by  the  posterior  part  of  the  circle  are 
small,  few,  and  of  no  interest. 

Among  the  branches  arising  from  the  anterior  portion,  there  is  only  a  single 
pair  of  arteries  to  be  noted,  which  are  remarkable  for  their  mode  of  distribution 
and  their  volume.  They  originate  near  the  border  of  the  extensor  tendon,  and 
immediately  divide  into  two  divergent  branches  :  one  the  internal,  which  passes 
across  that  tendon  to  anastomose  with  the  homologous  branch  of  the  opposite 
side  ;  the  other,  external,  passes  backward  to  meet  the  cutigeral  branch  furnished 
by  the  artery  of  the  plantar  cushion,  and  joins  that  vessel.  From  this  disposi- 
tion results  a  very  fine  superficial  vascular  arch  around  the  coronet,  which  is  well 
named  the  circumflex  artery  of  the  coronary  cushion ;  it  is  situated  a  little  above 
the  cutidural  artery,  beneath  the  skin  of  the  coronet,  and  looks  as  if  encrusted  in 
that  membrane  ;  by  its  two  extremities  it  rests  on  the  arteries  of  the  plantal 
cushion,  and  is  fed  by  the  two  principal  vessels  of  the  coronary  circle  ;  while  it 
furnishes  ascending  anastomosing  ramuscules  to  the  inferior  divisions  of  the  per- 
pendicular artery,  as  well  as  numerous  descending  branches  passing  into  the 
coronary  cushion  and  the  laminal  tissue  of  the  foot. 

Such  is  the  ordinary  disposition  of  the  coronary  circle  and  its  superficial  arch 
— the  circumflex  artery  of  the  coronary  substance  ;  though  it  varies  much  in 
different  animals,  and  even  in  the  feet  of  the  same  animal.  To  attempt  to 
describe  here  the  variations  we  have  seen  would  be  supererogatory,  and  we  may 
hmit  ourselves  to  saying  that  these  varieties  were  almost  exclusively  confined  to 
the  origin  of  the  branches  composing  these  two  circular  vessels  and  their  manner 
of  arrangement,  without  modifying  in  any  way  the  general  disposition  of  the 
circles.' 

Terminal  divisions. — These  are,  as  has  been  ah-eady  mentioned,  the  plantar 
and  preplantar  ungual  arteries.^ 

a.  The  preplantar  ungual  artery  is  the  smallest  of  these  two  terminal  branches. 
Situated  at  first  inside  the  basilar  process  of  the  third  phalanx,  it  turns  round 
this  to  traverse  the  notch  which  separates  this  process  from  the  retrossal  eminence, 
is  lodged  with  a  satellite  nerve  in  the  preplantar  fissure,  which  it  crosses  from 
before  to  behind,  and  terminates  near  its  anterior  extremity  by  several  divisions 
that  bury  themselves  in  the  os  pedis.  In  its  course,  it  distributes  :  1.  Before 
passing  into  the  sub-basilar  notch,  a  deep  retrograde  branch  destined  to  the  bulb 
of  the  heel  and  the  villous  tissue.  2.  Immediately  after  leaving  that  notch,  a 
second  retrograde  branch,  whose  divisions  pass  backward,  behind  the  great 
circumflex  artery  of  the  pedal  bone.  3.  During  its  passage  in  the  preplantar 
fissure,  several  ascending  and  descending  branches  which  ramify  iu  the  laminal 
tissue  ;  the  firet  anastomose  with  the  descending  divisions  of  the  coronary  circle 
and  the  circumflex  artery  of  the  coronary  cushion. 

*  We  may  notice  here  one  of  these  variations,  which  is  somewhat  frequently  met  with  in 
the  anterior  limb.  This  consists  in  the  anterior  descending  branch  of  the  perpendicular  artery 
uniting  at  its  terminal  extremity  with  the  circumflex  artery  of  the  coronary  substance,  which 
it  concurs  to  form. 

*  In  all  treatises  on  anatomy,  these  vessels  are  simply  designated  the  plantar  and  preplantar 
arteries.  We  have  added  the  epithet  ungual  to  distinguish  these  arteries  from  the  properly 
so-called  plantar  bmnclies— the  terminal  divisions  of  the  posterior  tibial  artery. 


640  TEE  ARTERIES. 

b.  The  plantar  ungual  artery  ou,2:lit  to  be  regarded  as  a  continuation  of  the 
digital  arterj,  because  of  its  vokime  and  direction.  Lodged  at  first,  with  a  fine 
nervous  branch,  in  the  plantar  fissure,  it  afterwards  enters  the  canal  of  the  same 
name,  and  thus  penetrates  into  the  semilunar  sinus  of  the  os  pedis,  where  it 
anastomoses  by  inosculation  with  the  opposite  artery,  forming  a  deep  vascular 
arcade  which  we  designate  the  plantar  arcade  or  circle,  or,  after  M.  H.  Bouley, 
the  semilunar  anastomosis  (Fig.  377,  12)! 

Two  orders  of  branches  emanate  from  the  convexity  formed  by  this' anasto- 
motic loop.  The  (tscencUng  order  "  irradiate  in  the  spongy  framework  of  the 
third  phalanx,  and  like  so  many  hair-roots,  escape  by  numerous  openings  from 
its  anterior  face,  where  they  form  a  very  intricate  plexus  by  anastomosing,  in  the 
texture  of  the  laminal  tissue,  with  the  extreme  divisions  of  the  anterior  branch 
of  the  digital  artery  and  those  of  the  coronary  circle.  ...  It  is  to  these  divisions 
that  Spooner  has  given  the  name  of  anterior  laminal  arteries  "  (H.  Bouley). 

The  descending  order,  much  more  considerable,  named  by  Spooner  (W.  C,  of 
Southampton)  the  inferior  communicating  arteries,  arise  at  a  right  angle  from  the 
anterior  circumference  of  the  semilunar  anastomosis,  traverse  in  a  divergent 
manner  the  tissue  of  the  phalanx,  and  make  their  exit  by  the  large  foramina 
situated  a  little  above  the  inferior  border  of  the  bone,  where  they  furnish  a  mul- 
titude of  ascending  ramuscules  which  Concur  to  form  the  arterial  network  of  the 
laminal  tissue.  "  Then  they  anastomose  transversely*  by  a  succession  of  little 
arcades  which  are  thrown  from  one  to  the  other,  and  in  this  way  give  rise  to  a 
great  circumflex  canal  which  follows  the  contour  of  the  parabolic  curve  exhibited 
by  the  thin  border  of  the  os  pedis,  on  its  inferior  face"  (H.  Bouley).  This 
vascular  arch,  which  we  pui^pose  naming  the  inferior  circumflex  artery  of  the  foot 
(Fig.  377,  12),  to  distinguish  it  from  the  circumflex  of  the  coronary  cushion,  is 
joined  by  its  extremities  to  the  preplantar  artery,  in  the  same  manner  that  the 
latter  circumflex  is  united  to  the  artery  of  the  plantar  cushion.  From  its  con- 
cavity it  throws  off  some  fourteen  or  fifteen  convergent  branches,  which  are 
destined  to  the  villous  tissue  of  the  sole. 

Differential  Characters  of  the  External  Iliacs  in  the  other  Animals. 
1.  External  Iliac  Arteries  of  Ruminants. 

In  the  Ox,  apart  from  the  considerable  vohime  of  the  great  muscular  arteries  of  the  tliigh, 
the  external  iliac,  as  well  as  the  femoral  and  popliteal  arteries  continuin":  it,  comport  themselves 
almost  the  same  as  in  the  Horse.  It  is  only  when  we  reach  the  posterior  and  anterior  tibial 
arteries  that  we  find  some  peculiarities  worthj^  of  notice. 

Posterior  tibial  artery. — Much  more  voluminous  than  that  of  Solipeds,  this  artery  follows 
the  same  course,  and  terminates  iu  an  analogous  manner :  forming  at  its  lower  extremity  two 
plantar  branches,  which  anastomose  witli  the  perforating  pedal  artery  behind  the  superior  ex- 
tremity of  the  principal  metatarsal  bone,  and  beneath  the  suspensory  ligament.  But  these  two 
branches  are  far  from  possessing  the  same  volume ;  the  internal  is  incomparably  the  largest, 
and  appears  to  be  the  direct  continuation  of  the  posterior  tibial  artery. 

From  this  anastomosis  results,  as  in  tiie  Horse,  two  series  of  metatarsal  branches — a  deep 
and  a  superficial. 

The  deep  branches,  two  or  three  in  number,  form  on  the  posterior  face  of  the  metatarsal 
bone,  below  the  suspensory  ligament,  the  posterior  interosseae,  mixed  with  two  or  three  reticu- 
lated venous  branches  ;  they  anastomose  by  their  inferior  extremity  with  a  perforating  branch 
of  the  collateral  of  the  cannon. 

The  superficial  branches,  similar  to  those  which  accompany  the  plantar  nerves  in  the  Horse, 
are  of  very  unequal  calibre ;  the  external  is  so  rudimentary  that  it  often  escapes  dissection  ; 
the  internal  in  reality  continues  tlie  plantar  artery  of  the  same  side.  Both  are  united  to  the 
perforating  branch  already  noticed. 


TEE  EXTERNAL  ILIAC  ARTERIES  641 

Anterior  tibial  artery. — After  passing  dowu  along  the  leg  on  its  antero-external  face,  as  in 
Solipeds,  this  vessel  arrives  on  the  hock,  where  it  takes  the  nume  of  pedal  artery,  and  furnishes 
the  per/orating-pedal  artery ;  it  is  continued  by  the  metatarao-pedal  or  collateral  artery  of  fht 
cannon. 

a.  The  perforating  pedal  artery  does  not  differ  from  that  of  the  Horse. 

h.  The  metatar so- pedal,  or  collateral  of  the  cannon,  descends,  flanked  by  two  satellite  veins, 
in  the  channel  on  the  anterior  face  of  the  metatarsal  bone,  giving  off  towards  the  inferior 
extremity  of  that  channel,  the  perforating  branch  already  spoken  of,  and  is  continued  into  the 
digital  region  as  the  common  digital  artery. 

The  perforating  branch  of  the  collateral  of  the  cannon  passes  into  the  foramen  pierced  from 
before  to  behind,  across  the  inferior  extremity  of  the  metatarsal  bone,  arriving  beneath  the 
suspensory  ligament,  and  then  divides  into  several  ascending  and  descending  branches.  The 
first  join  the  deep  and  superficial  posterior  metatarsal  arteries  furnished  by  the  plantar  and 
pedal  perforating  arteries.  Among  tiip  second,  we  notice  three  digital  arteries,  facsimiles  in 
miniature  of  those  which  will  be  described  in  the  anterior  limb  :  two  lateral,  descending  on  the 
eccentric  side  of  the  phalanges  ;  a  median,  turning  within  the  flexor  tendons  to  place  itself 
behind  them  on  the  middle  line  of  the  digital  region,  and  prolonged  into  the  interdigital  space, 
where  it  anastomoses  with  a  branch  of  the  principal  artery  of  the  digits. 

The  latter  artery — the  common  digital — descends  into  tlie  space  between  the  digits,  after 
passing  beneath  the  capsular  ligament  of  the  metatarso-phalangeal  articulations,  in  the  notch 
between  the  two  articular  surfaces  of  the  metatarsal  bone,  and  terminates  above  the  inferior 
extremity  of  the  first  phalanx  by  two  ungual  arteries,  the  description  of  which  will  be  reserved 
until  describing  the  arteries  of  the  anterior  limb.  In  the  number  of  collateral  branches 
emanating  from  this  vessel,  there  may  be  particularly  remarked  a  large  offshoot  which  arises 
a  little  before  the  separation  of  the  two  ungual  arteries,  and  is  directed  from  before  to  behind, 
dividing  at  the  posterior  part  of  the  interdigital  space  into  several  divisions,  the  principal  of 
which  are  ;  1.  Two  transverse  branches  passing  between  the  flexor  tendons  and  tlie  phalanges, 
to  be  joined  to  the  lateral  digital  arteries.  2.  A  single  ascending  branch,  joining  with  the 
posterior  median  digital  artery.  3.  A  descending  branch,  also  single,  dividing  into  two  por- 
tions which  reach  the  heels,  to  be  distributed  to  the  plantar  cushion  and  tlie  villous  tissue. 
These  branches  represent  the  arteries  of  the  plantar  cushion  in  the  Horse,  and  will  be  noticed 
more  in  detail  in  the  description  of  the  arteries  of  the  anterior  limb,  where  in  principle  tliey  are 
found  to  be  exactly  like  these. 

2.  External  Iliac  Arteries  of  the  Pig. 

The  distribution  of  these  vessels  in  the  Pig  is  remarkably  like  that  we  have  described  as 
existing  in  Ruminants,  even  in  the  terminal  portions  of  the  limbs,  notwithstanding  the  com- 
plete development  of  the  two  lateral  digits.  It  may  be  noted,  however,  that  the  posterior  tibial 
artery  is  somewhat  slender,  and  that  it  is  singularly  increased  by  its  anastomosis  with  tlie 
saphena  artery,  the  dimensions  of  which  are  relatively  considerable.' 

3.  External  Iliac  Arteries  of  Carnivora. 

The  external  iliac  is  divided  in  tlie  Carnivora,  as  in  the  other  animals,  into  three  sections  : 
the  proper  iliac  artery,  the  femoral  artery,  and  the  popliteal  artery,  terminated  by  the  tibial 
branches. 

Proper  iliac  artery. — Tiiis  vessel  does  not  give  rise  to  any  branch,  as  the  circumflex  iliao 
comes  directly  from  the  posterior  af)rta. 

Femoral  artery. — As  in  the  Horse,  this  gives  off:  1.  Several  muscular  innominate  branches. 
2.  Two  great  muscular  arteries,  the  posterior  of  wliich  furnisiies  the  prepubic  artery.  3.  A 
saphenal  branch. 

In  the  Bitch,  the  external  pudic  artery,  emanating  from  the  prepubic  division,  presents 
Bome  peculiarities  in  its  distribution.  It  gives  off  a  long  branch  which  is  placed  in  the  texture 
of  the  mainmse,  and  passes  forwanl  to  meet  and  unite  with  the  mammary  branch  furnished  by 
the  internal  thoracic  artery ;  it  then  runs  between  the  two  thighs  in  a  flexuous  manner,  and 
reaches  the  lips  of  the  vulva,  where  it  ends  in  numerous  ramuscules  that  anastomose  with  the 
vulvar  divisions  of  the  internal  pudic  artery. 

The  saphena  artery  is  as  remarkable  for  its  large  volume  as  for  its  destination.     It  descends 


'  In  small  Ruminants,  the  posterior  tibial  artery,  properly  speaking,  is  equally  rudimentary; 
the  saphena  artery  constitutes  tlie  principal  vessel.  From  a  note  which  we  made  a  long  time 
ago,  it  appears  the  first  vessel  is  altogether  absent  sometimes,  and  that  the  plantar  divisions 
come  exclusively  from  the  saphena,  as  in  the  Carnivora. 


612 


THE  ARTERIES. 


on  the  internal  face  of  the  leg,  furnishing  numerous  subcutaneous  divisions,  and  terminates  at 
the  hock  by  several  slender  plantar  twigs,  which  accompany  tlie  flexor  tendons.  Among  the 
branches  given  oif  by  this  vessel  in  its  course,  it  is  necessary  to  distinguish  two — one  which 
follows  the  anterior  branch  of  the  saphena  vein  to  the  hock,  where  it  communicates  by  its 
terminal  divisions  with  the  tarsal  artery ;  the  other  arises  a  little  lower,  passes  beneath  the 


Fig.  372. 


Y\z.  373. 


ANTERIOR  ASPECT  OF  HUMAN  LEG  AND  FOOf. 

1,  Tendon  of  insertion  of  the  quadriceps  ex- 
tensor muscle  ;  2,  insertion  of  the  ligamen- 
tum  patellre  ;  3,  tibia  ;  4,  extensor  lungus 
digitorum  ;  6,  peronei ;  7,  inner  belly  of 
gastrocnemius  and  soleus;  8,  annular 
ligament;  9,  anterior  tibial  artery;  10, 
its  recurrent  branch  inosculating  with  (2) 
inferior  articular  and  (1)  superior  articular 
arteries,  branches  of  the  popliteal;  11, 
internal  malleolar  artery;  17,  external 
ditto,  inosculating  with  anterior  peroneal 
artery,  12;  13,  dorsalis  pedis  artery;  14, 
tarsea  and  metatarsea  ;  15,  dorsalis  hal- 
lucis  artery  ;  IR,  continuation  of  dorsalis 
pedis  into  sole  of  foot. 


POSTERIOR    ASPECT   OF    HUMAN   LEG. 

1,  Tendons  of  inner  hamstring;  2,  ditto  of 
biceps;  3,  popliteus  muscle  ;  4,  flexor 
longus  digitorum;  5,  libiilis  posticus; 
6,  fibula;  7,  peronei  muscles;  £>,  Jowcr 
portion  of  flexor  longus  pollicis,  v/itl".  itc 
tendon ;  9,  popliteal  artery,  sivlng  off 
articular  and  muscular  Viranchcs;  10,  an- 
terior tibial  artery;  11,  posterior  tibial 
artery;  12,  relative  position  of  tendons 
and  artery;  13,  peroneal  artery;  14,  pos- 
terior peroneal. 


phalangeal  flexor  muscles,  and  is  expended  on  the  hock  in  articular  and  malleolar  branches.  In 
the  latter  branch  we  see  a  trace  of  the  'peroneal  artery  of  Man.  The  saphena  itself,  considered 
as  a  whole,  and  particularly  towards  its  inferior  moiety,  supplements  the  posterior  tibial 
artery. 


THE  EXTERNAL   ILIAC  ARTERIES. 


643 


Popliteal  artery. — This  artery  gives  an  iimportant  femoro-poiiliteal  branch,  and  enters  the 
tibio-peroneal  arch  to  constitute  the  anterior  tibial  artery,  after  distributing  on  its  course 
muscular  ramuscules — rudiments  of  the  posterior  tibial  artery  of  other  animals. 

The  anterior  tibial  artery,  arriving  in  front  of  the  hock,  detaches  the  tarsal  artery — a 
voluminous  branch,  divided  near  its  origin  into  several  superficial  superior  and  inferior  branches. 
It  continues  to  descend,  traverses  from  before  to  behind  the  superior  part  of  the  third  inter- 
metatarsal  space,  and  terminates  by  an  arterial  arch  situated  beneath  the  flexor  tendons  ;  from 
this  arch  emanate  ascending  divisions,  that  anastomose  with  the  plantar  arteries,  and  three 
large  descending  or  digital  branches,  which  affect  the  same  disposition  as  three  analogous 
principal  arteries  emanating  from  the  superficial  palmar  arch  of 
the  anterior  limb. 

Fig.  374. 

Comparison  of  the  External  Iliacs  of  Man  witk  those  of 
Animals. 

In  Man,  the  external  iliac  forms  the  external  branch  of  the 
bifurcation  of  the  common  iliac ;  it  extends  to  the  crural  arch, 
where  it  takes  the  name  of  femoral  artery.  It  furnishes  the  cir- 
cumflexa  ilii  and  epigastric  :  the  latter  resembling,  in  its  distribu- 
tion, the  posterior  abdominal  branch  given  off  by  the  prepubic 
artery  in  the  Horse. 

Tlie  femoral  artery  has  the  same  general  disposition  as  in 
animals,  and  almost  the  same  collateral  branches.  There  is  no 
prepubic  artery  ;  the  divisions  furnished  by  this  trunk  in  Solipeds 
originate  separately  from  the  femoral  artery ;  these  are :  the 
abdominal  tegumental  artery  (superficial  epigastric),  and  the  exter- 
nal pubic  arteries — the  one  resembling  the  subcutaneous  abdominal 
artery,  and  the  others  the  branches  of  the  external  pudic  artery 
of  animals. 

The  popliteal  artery  is  a  superficial  vessel  situated  at  the 
posterior  face  of  the  knee-joint,  in  a  lozenge-shaped  space  limited 
by  the  muscles  of  tlie  region,  and  named  the  popliteal  space.  At 
the  tibio-peroneal  arch  it  bifurcates,  and  constitutes  the  anterior 
til'ial  and  the  tibio-peroneal  trunks. 

The  tibio-peroneal  artery  does  not  exist  in  animals  in  which 
tlie  peroneal  artery  is  in  a  rudimentary  state,  in  consequence  of 
the  feeble  development  of  the  peroneus.  This  trunk  is  short,  and 
furnishes  the  nutrient  artery  of  the  tibia,  then  divides  into  the  1 
peroneal  and  posterior  tibial  artfries.  The  first  descends  to  the 
external  malleolus,  along  the  inner  f  ice  of  the  tibia,  and  terminates 
in  two  branches,  one  of  which,  the  anterior  peroneal,  communicates 
with  the  dorsal  artery  of  the  tarsus — a  branch  of  the  pedal.  The 
posterior  tibial,  on  reaching  the  concavity  of  the  caleis,  constitutes 
the  internal  and  external  plantar  arteries.  The  internal  plantar 
is  directed  forwards,  beneath  the  sole  of  the  foot,  and  is  lost  in  the 
muscles  of  the  great  toe,  or  forms  the  collateral  of  the  latter  vessel. 
Beneath  the  tarsal  articulations,  the  external  plantar  describes  a 
curve,  having  its  concjtvity  backwards,  and  anastomoses,  at  the 
fourth  intermetatarsal  space,  with  the  termination  of  the  dorsalis 
pedis;  from  this  results  a  plantar  arch,  which  gives  off,  from 
without   to  within:    1.  The  external  collateral  of  the  little  toe; 

2,  3,  4,  5,  the  interosseous  plantar  (or  digital)  arteries  of  the  first,  second,  third  and  fourth 
intermetatarsal  spaces ;  these  arteries,  at  the  root  of  the  toes,  bifurcate  to  furnish  collaterals 
to  these  organs. 

The  anterior  tibial  artery,  situated  on  the  anterior  face  of  the  interosseous  ligament  that 
unites  the  tibia  to  the  peroneus,  extends  to  the  annular  ligament  of  the  tarsus,  where  it  is  con- 
tinuerl  by  the  dorsalis  pedis,  which  descends  along  the  dorsum  of  the  foot  to  gain  the  summit 
of  the  fourth  interosseous  space. 

The  dorsal  artery  of  the  metatarsus  (metatarsea)  is  almost  nil  in  Solipeds.  In  Man  it  is 
directed  transversely  to  the  tarsus,  from  within  to  without ;  its  terminal  branches  unite  on  the 
dorsum  of  the  tarsus,  and  the  arch  itWrns  gives  off  the  dorsal  interosseous  arteries  of  thetliree 
first  spaces.      These  communicate  above  and  below,  in  the  intermetatarsal  spaces,  with  the 


arteries  of  sole  of 
human  foot. 

,  Under  surface  of  os  cal- 
eis ;  2,  musculus  aoces- 
sorius ;  3,  long  flexor 
tendons ;  4,  tendon  of 
peroneus  longus ;  5,  ter- 
mination of  posterior 
tibial  artery;  6, internal 
plantar  ;  7,  external 
plantar  ;  8,  plantar  arch 
giving  oft'  four  digital 
branches,  three  of  which 
are  seen  dividing  into 
collaterals  for  adjoining 


644  THE  ARTERIES. 

plantar  interosseous  arteries  by  the  anterior  and  podfrinr  perforating  arteries ;  finally,  at  the 
base  of  the  toes  they  bifurcate  to  form  the  collateral  arteries  of  the  toes. 

The  dorsal  collateral  artery  of  the  fourth  space  represents  the  vessel  described  in  the  Horse 
by  the  name  of  metatarso-pedal  artery,  or  collateral  of  the  cannon ;  it  forms  the  internal 
coUaterrtl  dorsal  of  the  fourth  toe,  and  external  collateral  of  the  great  toe. 

The  dorsalis  pedis,  after  giving  off  tlie  last-named  vessel,  dips  into  the  fourth  space  and 
reaches  the  lower  surface  of  the  foot,  where  it  anastomoses  with  the  internal  plantar  artery. 
In  this  last  portion  of  its  course  it  resembles  the  vessel  we  have  named  the  perforating  pedal 
in  Solipeds. 

Aeticle  v.— Anterior  Aorta  (Fig.  375,  1). 

This  vessel,  the  smallest  of  the  two  trunks  succeeding  the  common  aorta,  is 
no  more  than  2  or  2^  inches  in  length  at  the  most.  It  leaves  the  pericardium 
to  pass  between  the  two  layers  of  the  mediastinum  in  an  oblique  direction  from 
below  upwards  and  behind  forwards,  above  the  right  auricle,  below  the  trachea, 
and  to  the  left  of  the  anterior  vena  cava.  After  furnishing  some  insignificant 
twigs  to  the  pericardium  and  mediastinum,  it  divides  into  two  branches  which 
constitute  the  brachial  trunks  or  axiUary  arteries. 

In  Pachyderms,  Carnivora,  and  Rodents,  the  anterior  aorta  does  not  exist, 
and  the  axillary  arteries  arise  directly  from  the  common  aorta,  towards  the  point 
from  which  the  anterior  aorta  arises  in  other  animals. 

Article  YI. — Brachial  Trunks,  or  Axillary  Arteries  (Fig.  375,  2,  3). 

The  brachial  trunks — terminal  branches  of  the  anterior  aorta — are  distinguished 
into  left  and  right.  The  latter  is  much  larger  than  the  former,  because  it  fur- 
nishes arteries  to  the  head.     It  is  also  named  the  arteria  innominata. 

Origin. — They  separate  from  one  another  at  an  acute  angle,  the  left  being 
a  little  more  elevated  than  the  right. 

Course  and  direction. — Both  branches  are  directed  forwards,  between  the  layers 
of  the  anterior  mediastinum  and  beneath  the  trachea ;  gaining  the  entrance  to 
the  chest,  and  leaving  it  by  turning  round  the  anterior  border  of  the  first  rib, 
under  ttte  insertion  of  the  scalenus,  they  become  inflected  backwards  and  down- 
wards, to  be  placed,  one  to  the  right,  the  other  to  the  left,  at  the  internal  face  of 
the  anterior  limb,  in  the  middle  of  the  nerves  of  the  brachial  plexus,  and  continue 
within  the  arm,  assuming  the  name  of  Mimeral  artery  on  leaving  the  interstice 
which  separates  the  subscapularis  muscle  from  the  adductor  of  the  arm. 

In  its  thoracic  course,  the  left  trunk  describes  a  curve — the  convexity  being 
upwards — the  right  taking  a  rectilinear  direction. 

Relations. — In  studying  the  relations  of  the  brachial  trunks,  we  recognize  two 
principal  portions — one  thoracic,  placed  in  the  chest ;  the  other  axillary,  situated 
within  the  limb.  In  their  thoracic  portion,  the  brachial  trunks,  at  first  lying 
beside  each  other,  separate  slightly  in  front  to  reach  the  internal  face  of  each  of 
the  two  first  ribs.  They  are  accompanied  by  the  cardiac,  pneumogastric,  inferior 
laryngeal,  and  diaphragmatic  nerves,  and  are  included,  as  already  noticed,  between 
the  two  layers  of  the  anterior  mediastinum.  The  right  occupies  nearly  the 
middle  line  beneath  the  inferior  face  of  the  trachea,  to  the  left  and  above  the 
anterior  vena  cava.  The  left  slightly  rises  on  the  side  of  the  trachea,  and 
generally  corresponds  inwardly  to  the  thoracic  duct. 

In  their  axillary  portion,  these  vessels  accompany  the  coiTesponding  venous 
trunks,  cross  the  terminal  tendon  of  the  subscapularis  muscle  in  passing  below 
the  humeral  insertion  of  the   deep  pectoral,  and   among  the  branches  of  the 


THE  BRACHIAL   OR  AXILLARY  ARTERIES.  645 

brachial  plexus,  but  embraced  more  particularly  bj  the  median,  anterior  humeral, 
and  uljiar  nerves. 

Distribution. — The  axillary  arteries  give  off,  on  their  course,  eight  collateral 
branches.  Four  arise  from  the  thoracic  portion  :  three  upper — the  dorsal, 
superior  cervical,  and  vertebral  arteries  ;  and  an  inferior — the  internal  thoracic. 
Two  are  detached  at  the  first  rib — one  downwards,  the  other  forwards  ;  these  are 
the  external  thoracic  and  superior  cervical  arteries.  Two  originate  from  the  axil- 
lary portion  of  the  trunk  and  pass  upwards  :  they  are  the  supra-  and  subscapular 
arteries.  After  furnishing  the  latter  vessel,  the  brachial  trunk  is  continued  by  the 
humeral  artenj. 

Independently  of  all  these  branches,  the  right  axillary  artery  gives  off,  near 
its  origin,  the  common  trunk  of  the  two  carotid  arteries,  which  will  be  studied  in 
a  separate  article. 

Preparation. — The  subject  being  placed  on  the  right  side,  remove  the  skin  and  the  left 
anterior  limb,  in  order  to  make  the  dissection  at  two  periods. 

First  period. — Dissect  all  the  intra-thoracic  portion  of  the  left  axillary  artery  and  its  col- 
lateral branches,  as  in  Fig.  375,  taking  care  to  leave  the  inferior  cervical  artery  (which  has 
been  cut  in  the  figure  to  render  the  drawing  more  distinct)  attached  by  its  superior  extremity 
to  the  middle  portion  of  the  mastoido-humeralis,  which  has  not  been  disturbed. 

Second  period. — Prepare,  on  the  separated  limb,  the  extra-thoracic  portion  of  the  vessel  and 
all  the  arteries  it  furnishes,  in  taking  as  guides  Figs.  376,  377. 


Collateral  Branches  of  the  Axillary  Arteries. 
1.  DoESAL,  DoRSO-MUSCULAE,  OE  Teansveese  Ceevical  Aetery  (Fig.  375,  4). 

Chiefly  directed  to  the  muscles  of  the  withers,  this  artery — the  first  given  off 
by  the  brachial  trunk — crosses  outwardly  the  trachea,  thoracic  duct,  oesophagus, 
great  sympathetic  nerve,  and  the  longus  colli,  in  proceeding  beneath  the  media- 
stinal layer  ;  it  reaches  and  passes  over  the  second  intercostal  space,  bends  slightly 
backwards,  and  places  itself  in  the  interstice  separating  the  angularis  scapulse 
and  serratus  magnus  from  the  inferior  branch  of  the  longissimus  dorsi,  where  it 
separates  into  several  divergent  branches.  The  majority  of  these  ascend  towards 
the  superior  border  of  the  withers,  neck,  and  shoulders,  by  gliding  between  the 
latter  muscles,  the  splenius,  and  the  serratus  anticus  on  the  one  part,  and  the 
serratus  magnus  and  rhomboideus  on  the  other,  to  be  distributed  to  those 
muscles  and  the  integuments  covering  them.  The  most  anterior  of  these 
branches  passes  between  the  splenius  and  complexus  muscles,  parallel  with 
the  superior  cervical  artery,  which  is  in  front  of  it,  and  communicates  by  its 
ramuscules  with  the  latter  vessel,  as  well  as  with  the  vertebral  and  occipito- 
muscular  arteries.  The  last-named  branch  is  sometimes  long  and  voluminous, 
and  partly  supplements  the  superior  cervical,  as  is  exemplified  in  the  specimen 
which  served  for  Fig.  375. 

Before  leaving  the  thorax,  the  dorsal  artery  gives  off  some  unimportant 
ramuscules  and  the  subcostal  artery  {superior  intei-costal  of  Man).  This  branch 
(Fig.  375,  5)  curves  backwards  and,  with  the  sympathetic  chain,  places  itself 
beneath  the  costo-vertebral  articulations,  against  the  longus  colli,  furnishing  the 
second,  third,  and  fourth  intercostal  arteries  and  the  corresponding  spinal  branches, 
and  terminating  at  the  fifth  intercostal  space  by  either  forming  the  artery  which 
descends  into  that  space,  in  anastomosing  by  inosculation  with  a  branch  emanat- 
ing from  the  first  posterior  intercostal  artery,  or  by  expending  itself  in  the  spinal 


646  THE  ARTERIES. 

muscles.     Frequently,  the  second  intercostal  and  its  spinal  branch  come  directly 
from  the  doi*sal  artery  ;  the  fifth  also  often  arises  from  the  posterior  aorta.^ 

On  the  right  side,  the  dorsal  artery  always  proceeds  from  a  trunk  common  to 
it  and  the  superior  cervical  artery — a  circumstance  sometimes  observed  in  the 
left.     This  trunk  has  no  relation  with  the  oesophagus. 

2.  Superior  Cervical,  Cervico-muscular,  or  Deep  Cervical  Artery 
(Fig.  375,  6). 

This  vessel  arises  in  front  of  the  preceding  artery,  has  the  same  relations  in 
the  thoracic  cavity,  which  it  leaves  by  passing  between  the  two  first  ribs,  behind 
the  last  costo-transverse  articulation  ;  ^  it  is  then  directed  upwards  and  forwards, 
passing  beneath  the  inferior  branch  of  the  longissimus  dorsi  and  complexus 
muscles,  courses  in  a  flexuous  manner  through  the  space  comprised  between  the 
latter  muscle  on  one  side,  and  the  superior  branch  of  the  longissimus  dorsi  and 
cervical  ligament  on  the  other,  and  aiTives  at  the  second  vertebra  of  the  neck, 
where  its  terminal  divisions  anastomose  with  the  branches  of  the  occipito- 
muscular,  vertebral,  and  even  the  dorsal  arteries. 

The  superior  cervical  artery  distributes  in  its  course  :  1.  The  first  intercostal 
arteiy  and  the  first  spinal  branch.  2.  Very  numerous  branches  which  are 
expended  in  the  muscles  and  integuments  of  the  cervical  region,  as  well  as  in  the 
large  hgament  occupying  the  middle  plane  of  that  region  ;  among  these  branches, 
one  longer  than  the  others  traverses  the  complexus  muscle  to  place  itself  between 
it  and  the  splenius,  and  is  sometimes  supplemented  in  great  part  by  the  dorsal 
artery. 

3.  Vertebral  Artery  (Fig.  375,  7). 

Arising  at  an  acute  angle  from  the  axillary  artery  at  the  first  intercostal  space, 
and  covered  at  its  origin  by  the  mediastinal  layer,  the  vertebral  artery  proceeds 
forward  and  upward,  within  the  first  rib,  outside  the  oesophagus,^  the  trachea, 
and  the  inferior  cervical  ganglion,  and  is  situated  at  the  bottom  of  the  interstice 
separating  the  two  portions  of  the  scalenus,  with  the  fasciculus  of  branches 
arising  from  the  brachial  plexus,  which  is  a  little  above  the  vessel.  It  then 
passes  beneath  the  transverse  process  of  the  seventh  cervical  vertebra,  and 
traverses  the  series  of  cervical  foramina,  hidden  beneath  the  iutertransversahs 
colli,  to  anastomose  in  full  canal  with  the  retrograde  branch  of  the  occipital 
artery,  at  the  atlo-axoid  articulation,  underneath  the  obliquus  capitis  posticus 
muscle. 

In  its  track,  it  detaches  at  each  intervertebral  space  numerous  branches, 
which  may  be  divided  into  inferior,  superior,  external,  and  internal.  The  first 
chiefly  pass  to  the  scalenus,  longus  colli,  and  rectus  capitis  anticus  major.  The 
second,  which  are  incomparably  larger  and  more  numerous  than  all  the  others, 
are  destined  to  the  complexus  and  trachelo-mastoideus,  semispiualis,  and  longis- 
simus dorsi  muscles  ;  they  anastomose  with  the  divisions  of  the  superior  cervical 
and  occipito-muscular  arteries.  The  external  branches  are  very  small,  and  pass 
to  the  intertransversalis  muscle.  The  internal  branches  enter  the  intervertebral 
foramina  to  join  the  middle  spinal  artery. 

'  For  the  description  of  these  arteries,  see  p.  611. 

»  We  liave  seen  it  escape,  along  with  the  dorsal  artery,  by  the  second  intercostal  space. 

*  On  the  right,  these  relations  with  the  oesophagus  are  not  present. 


THE  BRACHIAL   OR  AXILLARY  ARTERIES. 


647 


4.  Internal  Thoracic  (Pectoral),  or  Internal  Mammary  Artery 
(Fig.  375,  9). 

The  internal  thoracic  artery  emerges  from  the  brachial  trunk  at  the  first  rib, 


Fig.  375. 


DISTRIBUTION   OF   THE    ANTERIOR   AORTA. 

I,  Anterior  »orta ;  2,  left  axillary  artery  ;  3,  right  axillary  artery ;  4,  dorsal  artery ;  5,  subcostal 
artery ;  6,  superior  cervical  artery ;  7,  vertebral  artery ;  8,  8',  inferior  cervical  artery  ;  9,  origin 
of  the  internal  thoracic  artery ;  10,  origin  of  one  of  the  external  or  intercostal  branches  of  this 
artery;  11,  one  of  its  inferior  ramuscules;  12,  external  thoracic  artery;  13,  origin  of  the  supra- 
scapular artery;  14,  common  carotid  artery  ;  14',  accessory  thyroid  artery ;  14",  thyro-laryngeal 
artery;  15,  atloido-muscular  artery;  16,  occipito-muscular  artery;  17,  posterior  aorta.  A, 
Pulmonary  aorta  ;  B,  trachea ;  C,  oesophagus  ;  D,  cervical  ligament  ;  E,  superior  branch  of  the 
longissimus  dorsi  muscle  ;  F,  inferior  branch  of  the  same ;  G,  complexus  muscle :  H.  splenius 
muscle ;  i,  J,  originating  aponeurosis  of  the  splenius  and  the  serratus  anticus  muscles ;  K,  section 
of  the  obliquus  capitis  major ;  L,  rectus  capitis  posticus  major ;  M,  rectus  capitis  anticus  major } 
N,  sterno-maxillaris ;  O,  P,  deep  and  superficial  pectoral  muscles  turned  downwards. 


648  THE  ARTERIES. 

and  immediately  descends  along  the  inner  face  of  that  bone  to  the  sternum, 
remaining  covered  by  the  pleura.  It  then  bends  backwards,  passes  under  the 
triangularis  sterni  muscle  and  above  the  sternal  cartilages,  which  it  crosses  near 
the  chondro-sternal  articulations,  and  reaches  the  base  of  the  xiphoid  cartilage, 
where  it  ends  in  two  branches — one  abdominal,  the  other  thoracic,  and  which 
have  been  named  the  anterior  abdominal  and  asternal  arteries. 

In  its  course,  the  internal  thoracic  artery  sends  off  collateral  branches,  which 
may  be  distinguished  into  superior,  inferior,  and  external.  The  superior  are 
always  very  slender,  and  proceed  to  the  pericardium  and  mediastinum.  The 
inferior  (Fig.  375,  11)  are  very  large,  and  traverse  the  intercostal  spaces  to  enter 
the  pectoral  muscles,  where  they  meet  the  ramifications  of  the  external  thoracic 
artery.  The  external  branches  (Fig.  375,  10)  follow  the  intercostal  spaces  ; 
each  generally  divides  into  two  branches,  which  finally  anastomose  by  inoscula- 
tion with  the  terminal  divisions  of  the  first  seven  intercostal  arteries. 

Terminal  branches  of  the  interned  thoracic  artery.  1.  Anterior  abdominal 
artery. — This  vessel  separates  from  the  asternal  artery  at  an  acute  angle,  and 
passes  directly  backward  to  escape  from  the  chest  by  coureing  beneath  the  xiphoid 
cartilage  ;  it  then  places  itself  on  the  superior  face  of  the  rectus  abdominis, 
which  it  enters,  after  detaching  lateral  branches  to  the  abdominal  walls,  and 
anastomoses  by  its  terminal  ramifications  with  the  posterior  abdominal  artery. 

2.  Asternal  artery. — This  vessel  glides  within  the  cartilaginous  circle  formed 
by  the  false  ribs,  in  crossing  the  digitations  of  the  transversalis  alxlominis,  and 
terminates  at  the  thirteenth  intercostal  space,  in  which  it  ascends  to  anastomose 
with  the  corresponding  intercostal  artery.  It  supplies  in  its  track  intercostal 
branches,  which  comport  themselves  like  the  analogous  branches  of  the  internal 
thoracic  artery  ;  fine  diaphragmatic  arterioles  :  and  abdominal  divisions,  which 
particularly  ramify  in  the  transversahs  abdominis. 

5.  External,  Inferior  Thoracic,  or  External  Mammary  Artery 
(Fig.  375,  12). 

Principally  distributed  to  the  deep  pectoral  muscles,  this  artery  commences 
at  an  acute  angle  in  front  of,  but  close  to,  the  preceding,  turns  the  anterior 
border  of  the  first  rib,  and  then  passes  back  against  the  internal  face  of  the  deep 
and  superficial  pectoral  muscles,  in  which  are  extended  its  collateral  and  terminal 
divisions.  It  gives  off  a  fine  branch  which  accompanies  the  spur  vein,  and 
ramifies  in  the  panniculus  carnosus. 

This  artery  sometimes  rises  from  the  supra-sternal  vessel ;  its  volume  is 
subject  to  great  variations,  and  we  have  seen  it  entirely  absent. 

6.  Inferior  Cervical  or  Trachelo-muscular  Artery  (Fig.  375,  8,  8'). 

Arising  opposite  the  two  preceding  vessels,  sometimes  near  the  external,  and 
at  other  times  near  the  internal  mammary  arteries,  this  vessel  is  at  first  situated 
in  the  gulf  between  the  jugulars,  within  the  anterior  superficial  pectoral  muscle, 
and  above  the  glands  at  the  entrance  to  the  chest ;  it  divides  after  a  short  course 
into  two  branches,  which  separate  at  a  very  acute  angle.  One  of  these,  the 
superior  {ascending  cervical  of  Man),  rises  between  the  mastoido-humeralis  and 
subscapulo-hyoideus  muscles,  to  which  it  is  distributed,  as  well  as  to  the  glands 
at  the  point  of  the  shoulder,  and  the  anterior  superficial  pectoral  and  angularis 
scapulae  muscles. 


THE  BRACHIAL   OB  AXILLARY  ARTHBIES.       r^  649 

The  inferior  branch  (thoracica  acromialis  of  Man)  descends  in  the  interspace 
comprised  between  the  mastoido-humeralis  and  the  anterior  deep  pectoral  muscles, 
accompanying  the  cephalic  vein  ;  it  is  distributed  to  these  two  muscles,  and  super- 
ficial and  anterior  superficial  pectorals. 

7.  SuPEA-scAPULAE  OE  Peescapulae  Aeteey  (Fig.  375,  13). 

This  is  a  small  and  slightly  tortuous  vessel,  which  arises  from  the  axillary 
artery,  a  little  before  it  reaches  the  tendon  of  the  subscapularis  muscle.  It  is 
directed  upwards,  and  enters  the  space  included  between  that  muscle  and  the 
supra-spinatus,  after  sending  off  some  divisions  to  the  anterior  superficial  pectoral 
muscle.  Its  terminal  branches  are  expended  in  the  inferior  extremity  of  the 
supra-  and  infra-spinati  muscles,  the  tendon  of  the  biceps,  and  in  the  articulation 
of  the  shoulder. 

8.  Infea-scapulae  oe  Subscapulae  Aetery  (Fig.  376,  2). 

This  artery  is  remarkable  for  its  considerable  volume ;  it  arises  at  a  right 
angle  from  the  axillary  artery,  at  the  space  separating  the  subscapularis  from  the 
teres  major  muscles.  Its  origin  indicates  the  limit  artificially  fixed  between  the 
brachial  trunk  and  the  humeral  artery.  It  is  seen  to  proceed  upwards  and  back- 
wards in  this  interspace,  within  the  caput  magnima,  until  near  the  dorsal  angle 
of  the  scapula,  where  it  terminates. 

It  gives  off  on  its  track  : 

1.  An  artery  which,  following  the  inferior  border  of  the  latissimus  dorsi 
muscle,  ascends  to  its  inner  face,  throwing  off  twigs  into  the  substance  of  the 
muscle,  as  well  as  into  the  panniculus  carnosus. 

2.  The  scapulo-humeral,  or  posterior  circumflex  artery  of  the  shoulder,  which 
passes  from  within  that  articulation,  beneath  the  caput  magnum,  to  reach  its 
external  face.  After  giving  off  some  collateral  branches,  it  arrives,  with  the 
circumflex  nerves,  underneath  the  abductors  of  the  arm,  where  it  breaks  up,  like 
its  sateUite  nerve,  into  several  divergent  branches  destined  to  the  three  muscles 
above  named,  the  oblique  flexor  and  short  extensor  of  the  forearm,  and  to  the 
mastoido-humeralis  and  panniculus  carnosus. 

3.  Muscular  hranches,  which  escape  at  intervals  during  the  course  of  the 
vessel,  and  are  sent  forwards  and  backwards.  The  anterior  pass  either  to  the 
internal  or  external  side  of  the  scapula,  or  to  both  sides  of  that  bone,  the  posterior 
border  of  which  they  embrace  in  their  bifurcation.  The  internal  divisions  creep 
in  the  fissures  on  the  deep  face  of  the  bone,  throwing  their  ramuscules  into  the 
subscapularis  muscle,  and  even  reaching  the  supra-spinatus,  as  well  as  the  inser- 
tion of  the  angularis  scapulte  and  serratus  muscles.  The  external  divisions 
traverse  the  caput  magnum,  to  be  distributed  to  the  supra-  and  infra-spinati  and  the 
abductor  muscles  of  the  arm — one  furnishing  the  nutrient  arteiy  of  the  scapula. 
Y\xQ  posterior  branches  supply  the  abductor  of  the  arm,  and  the  caput  magnum. 

Humeral  Artery,  or  Terminal  Artery  of  the  Brachial  Trunk  (Fig.  376). 

Course. — This  vessel  is  a  continuation  of  the  axillary  artery,  which  changes 
its  name  after  giving  off  the  subscapular  branch.  At  first  it  describes  a  slight  curve 
forwards  to  descend  almost  vertically  to  the  inside  of  the  thoracic  Umb,  by 
crossing   obliquely  the   direction   of  the   humerus,  and   terminates   above  the 


650  p-i  THE  ARTERIES. 

inferior  extremity  of  that  bone  by  two  branches,  which  constitute  the  anterior 
and  posterior  radial  arteries. 

Relations. — In  its  course,  the  humeral  artery  is  related  :  in  front,  to  the 
median  or  ulno-plantar  nerve,  and  to  the  posterior  border  of  the  coraco-humeralis 
muscle,  which  it  closely  follows  ;  behind,  to  the  vein  of  the  arm,  and  through  it 
to  the  ulnar  nerve  ;  outwardly,  to  the  common  tendon  of  the  latissimus  dorsi  and 
the  teres  major,  to  the  caput  parvum,  and  to  the  humerus  ;  inwardly,  to  the 
sheath  of  the  biceps  muscle,  which  separates  the  posterior  deep  pectoral  from  the 
artery  of  the  arm,  and  in  which  this  vessel  is  enclosed,  in  common  with  its  satellite 
vein,  the  lymphatic  glands  and  vessels  of  the  arm,  as  well  as  with  the  nerves  of 
the  fore  limb. 

Collateral  branches. — Among  these  may  be  distinguished  four,  which  merit 
particular  mention.  They  are  the  prelmmeral,  external  and  internal  collateral 
arteries  of  the  elboiv,  and  the  principal  artery  of  the  flexor  brachii  muscle.  "We 
need  only  indicate,  besides  these,  several  irregular  ramuscules  which  go  to  the 
latter  muscle,  to  the  coraco-humeralis,  and  to  the  caput  parvum. 

1.  Prehwmral,  or  anterior  circumflex  artery  (Fig.  376,  4). — This  arises  at  a 
right  angle,  is  directed  forward,  passes  between  the  two  branches  of  the  coraco- 
humeralis,  turns  round  the  anterior  face  of  the  humerus,  beneath  the  bicipital 
groove,  and  terminates  in  the  mastoido-humeralis  muscle.  During  its  progress  it 
gives  off  branches  to  the  coraco-humeralis  and  biceps  muscles,  as  well  as  to  the 
articulation  of  the  shoulder.  Among  the  articular  ramifications,  there  is  one 
which  ascends  outwardly  on  the  tendon  of  the  infra-spinatus  ;  the  ultimate 
divisions  anastomose  with  the  ramuscules  of  the  posterior  circumflex  artery. 

2.  Deep  humeral  (humeralis  profunda),  or  ext&rnal  collateral  artery  of  the 
elbow  (Fig.  376,  5). — A  very  large  branch  which  emerges  from  the  humeral 
trunk,  by  forming  with  that  artery  an  almost  right  angle  at  the  common 
terminal  tendon  of  the  latissimus  dorsi  and  the  teres  major.  After  a  very  short 
course,  it  divides  into  two  principal  branches  ;  one  of  these  sends  its  ramuscules 
into  the  caput  magnum  and  medium  ;  the  other  passes  under  that  muscle  in 
turning  round  the  humeralis  obliquus,  along  with  the  radial  nerve,  and  reaching 
beneath  the  caput  medium,  descends — still  with  its  satelhte  nerve — in  front  of 
the  articulation  of  the  elbow,  where  this  branch  anastomoses  with  the  anterior 
radial  artery.  It  supplies  all  the  olecranian  muscles — except  the  caput  magnum — 
as  well  as  the  humeralis  obliquus  and  the  extensor  metacarpi  magnus. 

3.  Epicondyloid,  internal  collateral  of  the  elbow  {cubital),  or  ulnar  artery  (Fig. 
376, 7). — Smaller  than  the  external  collateral,  this  artery  arises  at  the  nutrient  fora- 
men of  the  humerus,  and  proceeds  backwards  on  the  internal  face  of  that  bone,  to 
pass  beneath  the  caput  magnum,  by  following  in  a  more  or  less  flexuous  manner 
the  inferior  border  of  the  caput  parvum  ;  it  then  descends,  at  first  behind  the 
epicondyle,  then  on  the  forearm,  which  it  passes  along  for  its  whole  length, 
underneath  the  aponeurotic  sheath  of  this  region,  between  the  flexor  metacarpi 
medius  and  externus,  accompanied  by  the  ulnar  vein  and  nerve  of  the  same 
name,  and  the  tendon  of  the  ulnar  portion  of  the  perforans  muscle.  Arriving 
near  the  carpus,  this  long  branch  anastomoses  by  inosculation  with  a  branch  from 
the  posterior  radial  artery. 

In  its  antibrachial  course,  this  artery  only  gives  off  very  attenuated  branches, 
the  study  of  which  is  of  little  importance.  But  before  attaining  the  forearm,  it 
furnishes  :  1.  The  nutrient  artery  of  the  humerus.  2.  Articular  ramuscules. 
3.    More   or   less   voluminous   muscular   branches,   particularly   for   the   caput 


THE  BRACHIAL   OR   AXILLARY  ARTERIES. 


651 


magnum  and  medium,  and  superficial  pectoral  muscles.     Those  which  arrive  in 
the  latter  muscle  traverse  it  only  to  become  subcutaneous  alternately ;  one  of 
them   accompanies   the   principal   superficial  vein   of   the   forearm,  and   sends 
ramuscules  into  the  bend  of  the  elbow. 
Regular  in   their  distribution,   these 
different    arteries    present    numerous 
varieties  of  origin,  among  which  it  is 
difficult  to  distinguish  the  most  con- 
stant disposition.    The  last-mentioned 
vessel  and  the  nutrient  artery  of  the 
humerus,  often  emanate  directly  from 
the  humeral  trunk. 

4.  Principal  artery  of  the  biceps,  or 
coraco-radialis  artery  (Fig.  376,  6). — 
This  arises  a  little  below  or  above  the 
preceding  ;  opposite  to,  or  in  front  of 
it,  it  usually  divides  into  two  branches 
— one  ascending,  the  other  descending, 
which  enter  the  substance  of  the 
muscle. 

1.  Anterioe  Eadial  (or  Spiral) 
Artery  (Figs.  376,  377). 

The  anterior  radial  artery,  the 
smallest  of  the  two  terminal  branches 
of  the  humeral,  separates  at  an  acute 
angle  from  the  posterior  artery,  above 
the  articular  condyle  of  the  humerus. 
It  descends  on  the  anterior  face  of  the 
ulnar  articulation,  passing  beneath  the 
inferior  extremity  of  .the  flexor  muscles 
of  the  forearm  and  the  superior  ex- 
tremity of  the  extensor  metacarpi, 
where  it  meets  the  radial  nerve  ;  in 
company  with  this  nerve,  it  extends  ■ 
on  the  anterior  face  of  the  radius, 
below  the  extensor  metacarpi  magnum, 
to  the  knee,  where  it  becomes  very 
thin  and  breaks  up  into  several 
ramuscules,  which   are  continued  on 

TERMINATIONS   OF   THE   AXILLARY   ARTERY 
IN    THE    HORSE. 

A,  Axillary  portion   of  the   brachial   trunk.     1, 
Supra-scapular  artery ;  2,  infra-scapular  artery; 

3,  branch  to  the  latissimus  dorsi  from  the  latter  ; 

4,  prehumeral   or  anterior   circumflex   artery ; 

5,  humeralis  profunda  ;  6,  principal  artery  of 

the  biceps;  7,  internal  collateral  or  cubital  artery;  7',  the  point  where  it  becomes  the  ulnar; 
8,  nutrient  artery  of  the  humerus,  c,  Posterior  radial  artery  at  its  origin.  9,  Muscular  branch 
of  the  posterior  radial  artery;  10,  10,  collateral  of  the  cannon,  one  of  the  terminal  branches  of 
the  posterior  radial ;  11,  vessel  common  to  the  interosseous  metacarpals,  another  branch  of  the 
posterior  radial  artery. 


652  THE  ARTERIES. 

the  capsular  ligament  of  the  carpal  articulations,  after  anastomosing  on  the 
inner  side  with  the  divisions  of  a  branch  furnished  by  the  posterior  radial  artery, 
and  on  the  outside  with  the  ramifications  from  the  interosseous  artery  of  the 
forearm. 

These  terminal  ramuscules  are  distributed  to  the  carpal  articulation,  or  the 
sheaths  of  the  extensor  tendons,  and  communicate  with  the  dorsal  interosseous 
metacarpal  arteries. 

The  collateral  branches  given  off  by  this  artery  are  very  numerous,  the 
majority  of  them  being  detached  from  the  superior  portion  of  the  vessel,  near 
the  elbow  ;  they  are  intended  to  supply  that  articulation,  but  more  especially  the 
muscular  masses  lying  in  its  neighbourhood,  or  covering  it. 

Such  is  the  usual  disposition  of  the  anterior  radial  artery  ;  though  it  is  liable 
to  numerous  variations — principally  in  the  manner  in  which  it  comports  itself 
with  the  interosseous  artery  of  the  forearm,  which  may  even  supplement  it  for 
the  whole  of  the  middle  and  lower  part  of  its  course.  This  will  be  noted  in 
describing  the  next  artery. 

2.  Posterior  Radial  Artery  (Fig.  377,  1). 

This  vessel,  in  its  volume  and  direction,  represents  the  continuation  of  the 
humeral  artery.  It  descends,  along  with  the  ulno-plantar  nerve,  on  the  internal 
ligament  of  the  humero-radial  articulation,  behind  the  terminal  extremity  of  the 
biceps  ;  then  under  the  internal  flexor  of  the  metacarpus,  its  satellite  muscle. 
Arriving  at  the  inferior  extremity  of  the  radius,  it  divides  into  two  terminal 
branches  -,  these  are  the  common  trunk  of  the  interosseous  metacarpal  arteries,  and 
the  collateral  (large  metacarpal)  artery  of  the  cannon. 

The  following  are  the  principal  collateral  branches  furnished  by  the  posterior 
radial  artery  : — 

1.  At  the  superior  extremity  of  the  radius,  articular  ramuscules  which  anasto- 
mose with  analogous  branches  from  the  ulnar  artery. 

2.  A  little  lower,  large  divisions  destined  for  the  muscles  of  the  posterior 
antibrachial  region,  some  of  them  arising  from  the  next  artery. 

3.  The  interosseous  artery  of  the  forearm,  a  considerable  vessel  which  arises  at 
the  same  point  as  the  preceding — the  radio-ulnar  arch,  and  crosses  this  from 
within  to  without,  after  traversing  the  posterior  face  of  the  radius,  beneath  the 
perforans  muscle,  to  descend  along  the  extensor  suffraginis,  in  the  channel 
formed  outwardly  by  the  union  of  the  two  bones  of  the  forearm.  This  inter- 
osseous artery  furnishes,  immediately  after  its  exit  from  the  radio-ulnar  arch, 
several  branches  to  the  articulation  of  the  elbow  and  the  antibrachial  muscles. 
At  its  terminal  extremity  it  usually  divides  into  a  number  of  branches,  the 
majority  of  which  join  the  branches  sent  to  the  carpus  by  the  anterior  radial 
artery.  It  is  rare  that  it  does  show  some  fine  anastomoses  with  one  of  the 
divisions  of  the  latter  artery  in  front  of,  or  outside  the  articulation  of  the 
elbow  ;  sometimes  it  directly  joins  that  vessel ;  and  we  have  seen  it,  on  the  con- 
trary, receive  the  anterior  radial  artery,  which  it  in  part  supplanted. 

4.  Several  muscular  and  musculo-cutaneous  ramuscules  without  any  fixed 
arrangement,  arising  from  different  points  of  the  course  of  the  parent  artery, 
below  the  preceding  divisions. 

5.  A  deep  branch,  also  liable  to  very  numerous  variations,  having  its  origin 
at  the  radial  insertion  of  the  perforatus  muscle,  descending  on  the  posterior  face 
of  the  radius,  chiefly  destined  to  the  carpus,  and  remarkable  for  the  anastomoses 


THE  BRACHIAL   OB  AXILLARY  ARTERIES. 


653 


that  its  internal  divisions  form  with  the  anterior  radial  artery,  and  for  those 
which  occasionally  unite  its  external  ramifications  to  the  ultimate  branches  of 
the  interosseous  artery  of  the  forearm  or  the  ulnar  artery 
(I'ig-  377,  2). 

1.  FiEST  Terminal  Branch  of  the  Posterior  Radial 
Artery  (Radio-palmar),  or  Common  Trunk  of  the 
Interosseous  Metacarpal  Arteries^  (Figs.  376,  5; 
377,  3). 

This  arterial  branch  separates  at  a  very  acute  angle  from 
the  collateral  artery  of  the  cannon.  It  descends  inside  and 
behind  the  carpus,  accompanied  by  the  principal  subcutaneous 
vein  of  the  limb,  and  with  it  is  included  underneath  a  super- 
ficial fascia,  which  maintains  them  in  a  channel  hollowed  on 
the  external  face  of  the  carpal  fibrous  sheath.  It  thus  arrives 
within  the  head  of  the  inner  metacarpal  bone,  where  it  is 
inflected  to  the  outer  side  by  crossing  the  superior  extremity 
of  the  suspensory  ligament,  and  between  it  and  th^  metacarpal 
ligament  the  latter  furnishes  to  the  perforans  tendon  ;  it 
anastomoses  by  inosculation  with  a  descending  branch  which 
emanates  from  the  superficial  arch  that,  above  the  carpus, 
unites  the  ulnar  artery  to  the  origin  of  the  collateral  artery  of 
the  cannon  (Fig.  376).  The  loop-like  anastomosis  thus  formed 
by  the  radio-palmar  artery  exactly  corresponds  to  the  deep 
palmar  arch  of  pentadactylous  animals,  particularly  to  that  of 
Man.  We  propose  to  name  it  also  the  infra-carpal  arch,  by 
reason  of  the  position  it  occupies  with  regard  to  the  carpus  ; 
reserving  the  appellation  of  supra-carpal  arch  for  the  superficial 
palmar  arch,  which  is  represented  by  the  anastomosis  established 
between  the  collateral  artery  of  the  cannon  and  the  ulnar  artery. 
Four  principal  branches  emanate  from  this  infra-carpal 
arch  :  these  are  the  metacarpal  interosseous  arteries,  distin- 
guished as  posterior  or  palmar,  and  anterior  or  dorsal. 

a.  The  posterior  interosseous  arise,  one  on  the  right,  the 
other  on  the  left,  at  the  head  of  the  lateral  metacarpal  bones, 
each  descending  on  its  own  side  and  in  a  flexuous  manner, 
along  these  rudimentary  bones,  in  the  angular  groove  formed 


7- 


ARTERIES   OF    THE    FORE    FOOT,    SEEN    FROM    BEHIND, 


The  muscles  and  tendons  have  been  removed,  only  a  small  portion  of  the 
perforans  tendons  being  left ;  the  os  pedis  has  been  chiselled  away  on  its 
plantar  face  to  expose  the  semilunar  anastomosis. 

1,  Posterior  radial  artery;  2,  innominate  carpal  branch;  3,  supra-carpal 
arch;  4,  ulnar  artery;  5,  radio-palmar  artery,  or  common  trunk  of  the 
Interosseous  metacarpal  arteries;    6,   infra-carpal  arch;    7,  7,   posterior 

interosseous  metacarpal  arteries;  7',  7',  anterior  interosseous  metacarpal  arteries;  8,  8,  their 
origin;  9,  collateral  artery  of  the  cannon;  10,  its  communicating  branch  with  the  interosseous 
arteries;  11,  U,  digital  arteries;  12,  semilunar  anastomosis  in  the  os  pedis;  13,  emergent 
branches  of  this  anastomosis;  14,  plantar  imgual  artery,  forming  the  anastomotic  arch;  15,  origin 
of  the  preplantar  ungual  artery;  16,  origin  of  the  plantar-cushion  artery;  17,  origin  of  the 
anterior  branch  of  the  coronary  circle;   18,  posterior  branch  of  the  same. 

'  This  vessel  corresponds  to  the  radio-palmar  artery  ofiMan,  by  which  uame  it  is  sometimes 
Jesignated.     Rigot  has  improperly  named  it  the  deep  plantar  artery. 


654  TBE  ARTERIES 

by  their  inner  face  and  the  posterior  face  of  the  principal  metacarpal  bone, 
terminating-  at  the  inferior  extremity  of  the  lateral  bones,  by  anastomosing  in 
full  canal  with  a  branch  of  the  collateral  of  the  cannon.  They  furnish  some 
ramifications  to  the  suspensory  ligament  which  covere  them,  and  several  tendinous 
and  cellulo-cutaneous  twigs  ;  one  supplies  the  nutrient  aitery  of  the  large  meta- 
carpal bone  (Fig.  377,  7). 

b.  The  anterior  interosseous  arteries  arise  from  nearly  the  same  point  as  the 
preceding — one  outwards,  the  other  inwards — turning  back  round  the  head  of 
the  lateral  metacaqjals  to  place  themselves  in  the  groove  which  separates  these 
from  the  large  metacarpal  bone,  on  their  external  or  dorsal  face,  after  having 
thrown  off  several  anastomosing  ramuscules  that  communicate  between  the  two 
arteries  in  front  of  the  upper  extremity  of  this  bone,  or  with  the  terminal 
branch  of  the  anterior  radial  and  the  interosseous  arteries  of  the  forearm.  By 
their  terminal  extremity,  these  two  arteries  anastomose  with  a  branch  of  the 
collateral  of  the  cannon — that  which  receives  the  posterior  interosseous  arteries 
(Figs.  376,  7;  377,  11). 

The  doi-sal  interosseous  arteries,  although  much  finer  than  the  palmar — in 
Solipeds  these  arteries  are  qiyte  rudimentary — nevertheless  furnish  collateral 
divisions  for  the  anterior  tendons  of  the  metacarpus,  the  periosteum,  the  con- 
nective tissue,  and  the  skin.  They  often  communicate  with  the  posterior  arteries 
by  deep  branches,  which  cross  the  intermetacarpal  ligaments. 

Variations. — The  existence  of  the  interosseous  metacarpal  arteries,  their 
position,  and  their  anastomoses  with  the  inferior  extremity  of  the  collateral  of 
the  cannon,  are  constant ;  though  this  is  not  the  case  with  regard  to  their  origin, 
or  the  source  whence  they  are  derived.  In  the  tyjiical  description  given,  we  have 
considered  them  all  as  being  furnished  by  the  radio-palmar  artery  ;  but  it  is 
necessary  to  add  that  one  of  the  four — the  external  dorsal — often  comes  directly 
from  the  arterial  branch  that,  from  the  siqjra-carpal  arch,  descends  along  the 
carpus  to  concur  in  forming  the  infra-carpal  arch,  by  anastomosing  with  the 
radio-palmar,  or  rather  with  a  branch  of  the  interosseous  of  the  forearm.  It  is 
also  necessary  to  add  that  these  metacarpal  arteries  sometimes  arise  together 
from  one  large  branch  furnished  by  the  collateral  of  the  cannon,  at  the  superior 
extremity  of  the  metacarpus  (Fig.  377),  and  which  receives  the  now  rudimentary 
radio-palmar  artery,  as  well  as  that  given  off  by  the  supra-carpal  arch  ;  so  that 
we  may  have  two  superposed  supra-carpal  arches.  We  have  met  other  anomalies 
which  need  not  be  noticed  here,  as  they  are  without  interest. 

2.  Second  Terminal  Branch  of  the  Posterior  Radial,  or  Collateral 
Artery  of  the  Cannon  ^  (Figs.  376,  9  ;  377,  2). 

The  collateral  artery  of  the  cannon  (or  large  metacarpal  artery)  (Fig.  376,  9) 
continues  by  its  volume  and  direction,  the  posterior  radial  artery.  It  passes, 
with  the  flexor  tendons,  under  the  carpal  arch,  and  descends  on  the  inner  side  of 
these  tendons,  accompanied  by  the  internal  plantar  nerve,  to  above  the  fetlock 
and  near  the  sesamoid  bones,  where  it  bifurcates  into  the  digital  arteries. 

Collateral  branches. — We  observe  : 

1.  Near  the  origin  of  the  artery,  and  very  often  from  the  posterior  radial 
artery  itself,  a  branch  which  anastomoses  above  the  pisiform  bone  with  the  ulnar 
artery,  forming  an  arch,  the  convexity  of  which  is  inferior  (Figs.  376,  10  ;  377, 

>  This  artery,  the  mperficial  plantar  of  Rigot,  represents  one  of  the  metacarpal  palmar 
hranches  furnished  by  the  superficial  palmar  arcli  in  Mau  and  other  pentadactylous  animals. 


THE  BRACHIAL   OR   AXILLARY  ARTERIES. 


6.55 


11),  and  which  has  been  ah-eady  noticed  as  the  supra-carpal  or  superficial  palmar 
arch,  in  contradistinction  to  the 
infra-carpal  or  deep  palmar 
arch — the  source  of  the  inter- 
osseous arteries  of  the  meta- 
carpus. This  ramification  fur- 
nishes one  or  more  muscular 
arterioles  that  usually  anas- 
tomose with  the  other  branches 
of  the  posterior  radial  artery  ; 
and  an  inferior  division/  which 
descends  in  the  carpal  arch, 
within  the  pisiform  bone,  to  the 
superior  extremity  of  the  meta- 
carpus, where  it  inosculates 
with  the  radio-palmar  artery, 
after  detaching  several  carpal 
ramuscules,  the  principal  of 
which  winds  round  the  inferior 
border  of  the  pisiform  bone. 

2.  On  its  course,  numerous 
and  fine  synovial,  tendinous, 
and  cutaneous  divisions. 

3.  A  trunk  springing  from 
the  terminal  extremity  of  the 
vessel,  between  the  two  digital 
arteries,  sometimes  even  from 
one  of  these,  which  is  placed 
at  the  posterior  face  of  the 
principal  metacarpal  bone, 
within  the  two  branches  of 
the  suspensory  ligament,  and, 
passing  upwards,  soon  divides 
into  two  branches  ;  these  anas- 
tomose  by   inosculation    with 

ARTERIES   OF   THE   ANTERIOR   FOOT 
OF   THE    HOUSE. 

1,  Posterior  radial  artery;  2,  2,  col- 
lateral of  the  canuou ;  3,  trunk 
common  to  the  interosseous  meta- 
carpals ;  4,  ulnar  artery ;  5,  supra- 
carpal  arch ;  6,  descending  branch 
from  the  arch  to  form  the  infra- 
carpal  arch ;  7,  arteriole  for  the 
ergot  from  the  trunk  common  to 
the  interosseous  metacarpals ;  8, 
infra-carpal  arch ;  9,  branch  of  the  collateral  of  the  cannon  concurring,  in  this  preparation,  in  the 
formation  of  the  interosseous  metacarpals;  10,  a  dorsal  interosseous  metacarpal  artery:  11,  com- 
municating branch  of  the  collateral  of  the  cannon  with  the  interosseous  metacarpals  ;  12,  12, 
digital  arteries  ;  13,  13,  arterioles  of  the  ergot;  14,  perpendicular  artery — one  of  its  branches  to 
the  circumflex  artery  of  the  coronet,  has  been  excised  on  removing  the  lateral  cartilage  ;  15,  15, 
arteries  of  the  plantar  cushion;  16,  anterior  part  of  the  coronary  circle;  17,  posterior  part  of 
ditto; I  18,  prej)lantar  ungual  artery  ;  19,  inferior  circumflex  arterv  of  the  foot. 

■  Analogous  to  the  radio-ulnar  artery  of  Man. 


656  THE  ARTERIES. 

the  posterior  interosseous  arteries  of  the  metacarpus,  after  giving  off  on  each  side 
two  other  ramuscules  that  wind  round  the  borders  of  the  large  met;)  carpal  bone, 
receiving  the  dorsal  interosseous  arteries,  and  ramify  in  front  of  the  fetlock,  on 
the  anterior  face  of  the  cannon  bone,  and  in  the  texture  of  the  capsular  ligament 
of  the  metacarpo-phalangeal  articulation  (Figs.  376,  10  ;  378,  11). 

Terminal  branches. — These  are,  as  we  said,  the  digital  arteries,  which  almost 
exactly  repeat  the  disposition  of  these  vessels  in  the  posterior  limb,  and  which 
have  been  described  at  p.  036. 

Differential  Characters  in  the  Axillary  Arteries  of  the  other  Animals. 

1.  Axillary  Arteries  of  Ruminants. 

Thf se  vessels  comport  themselves  in  their  origin,  course,  and  relations,  as  in  Solipeds. 
The  special  characters  they  present  in  their  distribution  are  as  follows : — 

1.  Dorsal  artery. — This  arises  from  a  trunk  common  to  it  and  the  vertebral  artery,  and 
usually  leaves  the  thorax  by  passing  above  the  first  costo-vertebral  articulation.  Its  subcostal 
branch  proceeds  directly  from  the  above-named  trunk. 

2.  Superior  cervical  artery. — This  is  absent,  and  is  replaced  by  a  branch  of  the  dorsal  artery, 
but  particularly  by  the  superior  muscular  divisions  of  the  vertebral  artery. 

3.  Vertebral  artery. — Extremely  voluminous,  and  terminates  in  the  muscles  of  the  neck, 
after  passing  through  the  foramen  of  the  axis ;  it  is  remarkable  for  the  considerable  size  of  its 
spinal  branches. 

4.  Inferior  cervical,  and  internal  and  external  thoracic  arteries. — Tiiese  do  not  present 
anything  worthy  of  special  consideration,  except  that  the  last  is  very  voluminous  in  the  Ox 
and  very  slender  in  the  Sheep,  and  supplies  the  satellite  arterial  branch  of  tlie  ceplialic  vein, 
which,  in  Solipeds,  arises  from  the  inferior  cervical  artery. 

5.  Supra-scapular  artery. — This  vessel  appears  to  us  to  be  absent  in  the  Sheep,  and  its  place 
supplied  by  the  divisions  of  the  inferior  cervical  artery. 

6.  Subscapulary  artery. — The  scapulo-humeral  branch  gives  off  the  majority  of  the  branches 
for  the  posterior  brachial  muscles. 

7.  Humeral  artery. — The  muscular  arteries  are  of  small  size,  particularly  the  deep  humeral, 
which  is  largely  replaced  by  the  scapulo-humeral  branch. 

8.  Anterior  radial  artery. — This  comports  itself  similarly  to  that  of  the  Horse,  and  is  liable 
to  as  frequent  anomalies. 

9.  Posterior  radial  artery. — This  artery  follows  the  same  course  as  in  Solipeds;  only 
instead  of  furnishing  the  radio-palmar  artery  near  the  carpus,  at  the  point  where  it  becomes 
the  collateral  artery  of  the  cannon,  it  gives  off  that  vessel  much  higher,  and  near  the  upper 
third  or  middle  of  the  forearm.  Its  interosseous  branch,  lodged  in  the  deep  channel  on  tho 
outside  of  the  bones  of  this  region,  where  the  radius  and  ulna  join,  is  separated  into  two 
branches  near  the  inferior  extremity  of  that  groove.  The  anterior  of  these  ramifies  on  the 
dorsal  face  of  the  carpus,  and  anastomoses  with  the  division  of  the  anterior  radial  artery;  the 
posterior  traverses  the  inferior  radio-ulnar  arch,  to  distribute  the  majority  of  its  branches 
behind  the  carpal  articulations. 

10.  Radio-palmar  artery.— Anaing,  as  we  have  already  seen,  from  the  posterior  radial 
artery,  towards  the  upper  third  of  the  forearm,  this  branch  descends  to  the  superior  extremity 
of  the  metacarpus  in  following,  as  in  the  Horse,  a  superficial  course,  and  ends  in  four  meta- 
carpal interosseous  arteries  :  three  posterior  or  palmar,  and  one  anterior  or  dorsal.  The  posterior 
interosseous  arteries  are  very  irregular  and  inconstant  in  their  disposition;  they  communicate 
witli  each  i)ther  by  several  branches,  and  anastomose,  inferiorly,  either  with  the  lateral  digital 
ftrteries,  the  collateral  of  the  cannon,  or,  as  is  most  commonly  the  case,  with  a  brancli  of  the 
latter  vessel.  These  interosseous  arteries  are  distinguislied  into  external,  middle,  and  internal ; 
the  first  two  are  comprised  between  the  posterior  face  of  the  metacarpus  and  the  suspensory 
ligament ;  the  third,  placed  at  the  inner  border  of  that  ligament,  is  more  considemble  than 
the  others,  and  by  its  volume  and  direction  represents  the  continuation  of  the  radio-palmar 
artery.  The  anterior  interosseous  artery  passes  through  the  foramen  at  the  superior  extremity 
of  the  metacarpus,  and,  arriving  at  the  dorsal  face  of  the  bone,  bifurcates,  its  ascending  branch 
reaching  the  capsular  ligament  of  the  carpal  articulations,  where  it  anastomoses  with  the 
divisions  of  the  anterior  radial  and  interosseous  arteries  of  the  forearm ;  the  descending  is 
lodged  in  the  anterior  groove  of  the  metacarpal  bone,  and  joins  a  perforating  branch  of  the 


THE  BRACHIAL   OR  AXILLARY  ARTERIES.  657 

collateral  artery  of  the  cannon — a  branch  that  crosses  the  foramen  towards  the  inferior  ex- 
tremity of  the  bony  diaphysis.  If  it  is  desired  to  ascertain  the  signification  of  these  interosseous 
arteries,  in  their  relation  to  the  elements  composing  the  foot  of  Ruminants,  we  readily  recognize: 
in  the  posterior  median  artery,  the  interosseous  palmar  of  the  two  great  digits ;  in  the  posterior 
lateral  arteries,  the  interosseous  palmar,  intermtdiates  to  these  middle  digits,  and  the  rudi- 
mentary lateral  digits  represented  by  the  ergots,  or  dew  claws ;  and  in  tlie  single  autfrior 
artery,  the  dorsal  interosseous  of  the  two  great  digits.  We  may  even  prove,  by  a  more  minute 
examination,  the  existence  of  dorsal  interosseous  arteries  corresponding  to  the  lateral  palmar 
interosseous  vessels. 

11.  Collateral  artery  of  the  cannon. — This  artery  follows  the  same  track  as  in  the  Horse,  as 
far  as  the  lower  third  or  fourth  of  the  metacarpus.  Arrived  at  this  point,  it  gives  off — as  in 
the  Horse — a  branch  the  divisions  of  which  communicate  with  the  interosseous  arteries,  and 
are  continued  by  the  digital  arteries,  three  in  number— a  middle  and  two  lateral. 

a.  The  communicating  branch  with  the  metacarpal  interosseous  arteries,  very  often  arises 
from  the  internal  digital  artery. 

It  is  insinuated  between  tiie  divisions  of  the  suspensory  ligament,  and  ascends  on  the 
posterior  face  of  the  metacarpus,  breaking  up  into  a  number  of  branches  which  nearly  all  join 
the  precited  arteries,  or  even  the  lateral  digital,  in  having  a  variable  and  complicated  arrange- 
ment which  it  is  neeilless  to  notice  here.  One  of  tliese  branches — a  true  perforating  artery, 
traverses  the  inferior  extremity  of  the  cannon  bone,  and  ascemls  in  its  anterior  groove  to  join 
the  anterior  interosseous  artery,  after  detaching  ramuscules  to  the  metacarpo-phalangeal 
articulation. 

h.  The  middle  digital  artery  represents,  in  its  dimensions,  the  continuation  of  the  collateral 
artery  of  the  cannon,  and  is  a  very  voluminous  vessel.  It  is  at  first  inflected  backwards  and 
outwards,  to  be  placed  on  the  posterior  face  of  the  perforatus  tendon ;  then  it  descends  into 
the  interdigital  space  by  passing  behind  the  sesamoid  bursa,  beueatli  the  ligament  uniting  the 
two  claws.  Reaching  the  inferior  extremity  of  the  first  phalanx,  it  divides  into  two  ungual 
arteries — one  for  each  digit,  which  are  inflected  forwards,  pass  beneath  the  internal  ligament 
common  to  the  two  interphalangeal  articulations,  and  enter  by  the  foramen  at  the  inner  side 
of  the  pyramidal  process,  into  the  internal  sinus  of  the  third  phalanx,  where  each  ramifies  in 
the  same  manner  as  the  plantar  ungual  arteries  of  the  Horse. 

Several  collateral  branches,  remarkable  for  the  richness  of  their  arborizations,  escape  from 
this  median  artery  of  the  digits  and  its  terminal  divisions.  The  most  important  of  these  are: 
1.  At  the  middle  of  the  first  phalanx,  two  short  transverse  branches— a  right  and  left,  passing 
beneath  the  flexor  tendons,  and  going  from  the  median  digital  artery  to  the  lateral  arteries  of 
the  digits.  2.  Nearly  at  the  same  point,  a  single  artery  which  traverses  the  interdigital  space 
from  behind  to  before,  to  pass  between  the  two  tendons  of  the  common  extensor  of  the  phalanges, 
■whence  it  ramifies  on  the  anterior  face  of  the  digits  by  ascending  alongside  the  anterior  median 
vein,  and  anastomosing  with  a  descending  branch  of  the  perforating  artery  which  crosses  the 
inferior  extremity  of  the  metacarpus.  3.  A  double  branch  analogous  to  the  artery  of  the 
plantar  cushion  of  the  Horse,  having  its  origin  at  the  terminal  extremity  of  the  digital  artery, 
often  arising  from  the  ungual  artery,  either  on  one  side  or  b"th,  ami  communicating,  by  a 
transverse  branch,  with  its  homologue ;  it  is  directed  backward  and  downward  on  the  bulb  of 
the  heel,  where  it  forms  an  anastomotic  arch  with  the  lateial  digital  aitery ;  from  the  convexity 
of  this  arch,  which  is  turned  downwards,  there  escapes  a  large  number  of  reticulating  ramus- 
cules, which  go  to  the  keratogenous  membrane  and  the  plantar  cushion. 

c.  The  lateral  digital  arteries  are  distinguished  into  internal  and  external.  The  first  has 
its  origin  at  the  bend  formed  by  the  collateral  of  the  cannon,  when  that  vessel  is  inflected  on 
the  posterior  face  of  the  perforatus  tendon  to  become  the  median  digital  artery,  most  frequently 
in  common  with  the  branch  the  divisions  of  which  join  the  metacarpal  interosseous  aiteries. 
The  second  commences  a  little  further  ofl",  after  having  received  a  branch  from  eitner  this 
communicating  artery,  or  from  the  external  interosseous  palmar ;  it  is  not  rare  to  see  it 
entirely  formed  by  one  of  these  branches,  or  by  the  two  together.  Whatever  may  be  their 
point  of  origin,  the  lateral  digital  arteries  descend  on  the  eccentric  side  of  the  digits,  outside 
the  flexor  tendons,  and  terminate  in  anastomosing  by  inosculation  with  the  artery  of  the 
plantar  cushion.  Among  the  collateral  branches  emanating  from  these  arteries,  there  ought  to 
be  distinguished  that  which  goes  to  the  ergot,  and  the  transverse  branch  thrown  across  between 
each,  as  well  as  the  median  digital  artery.' 

'  In  several  instances,  we  have  seen  the  lateral  digital  arteries  stop  at  this  transverse 
anastomosis,  which  then  received  them  entirely- 


THE  ARTERIES. 


2.  Axillary  Arteries  of  the  Pig. 


Both  spring  separately  from  the  arch  of  the  aorta  :  consequently,  there  is  no  anterior  aorta. 
The  right  uxillari/  artery,  ot  brachio  cephalic  trunk,  &Tat  arises;  the  left  comes  immediately 
after. 

0.  The  right  axillary  artery  is  directed  forwards,  under  the  inferior  fiice  of  the  trachea,  and 
leaves  the  thorax  to  reach  the  inner  face  of  the  anterior  limb,  as  in  other  animals. 

It  furnishes  successively  : — 

1.  At  tht!  first  rib,  an  1  below,  the  two  carotid  arteries,  rising  singly  from  nearly  the  same 
point. 

2.  Directly  opposite  to  these  vessels,  a  trunk  remarkable  for  the  complexity  of  its  dis- 
tribution ;  it  is  directed  upwards  and  backwards,  on  the  side  of  the  trachea  and  longus  cnUi, 
crosses  the  interval  between  the  second  and  third  ribs,  and  rises  to  the  deep  cervical  muscles 
to  terminate  in  the  vicinity  of  the  nape  of  the  neck.  It  evidently  represents  the  deep  or 
superior  cervical  artery.  Near  its  origin  it  gives  off  the  vertebral  artery,  the  termination  of 
wliich  is  exactly  the  same  as  in  the  Horse.  Beyond  this,  it  detaclies  the  dorsal  artery,  which 
ascends  into  the  muscles  of  the  withers,  after  passing  into  the  first  intercostal  space.  Lastly, 
it  supplies,  before  leaving  the  thorax,  the  subcostal  or  superior  intercostal  artery,  placed  across 
the  superior  extremities  of  the  third,  fourth,  and  fifth  ribs. 

y.  Always  within,  but  a  little  more  forward  than  the  first  rib,  a  voluminous  inferior  cervical 
orteri/,  divided  into  several  ascending  branches;  and  the  two  thoracic  arteries,  which  offer 
nothing  particular  for  description. 

4.  Outside  the  thorax,  on  the  internal  face  of  the  scapulo- humeral  articulation,  the  humeral 
or  subscapular  arteries.  The  first,  less  voluminous  than  the  other,  presents,  from  its  origin  to 
the  distribution  of  its  branches  in  the  foot,  a  disposition  essentially  resembling  that  observed 
in  this  ve.'<sel  in  Ruminants  ;  the  second  courses  upwards  in  the  space  between  the  sub- 
scapularis  and  the  teres  major,  and  soon  divides  into  two  terminal  branches,  one  of  which 
continues  the  course  of  the  vessel,  while  the  other  passes  beneath  the  subscapularis  muscle  to 
carry  its  ramifications  into  the  autero-external  muscles  of  the  shoulder,  furnishing  in  its 
course:  (1)  The  great  dorsal  artery,  throwing  a  part  of  its  ramifications  into  the  olecranian 
muscles.  (2)  A  voluminous  branch  that  provides  the  greater  number  of  the  divisions  given  off", 
in  the  Horse,  by  the  deep  humeral  and  prehumeral  arteries.  (.S)  Two  articular  branches,  one 
of  which  closely  represents  the  supra-scapular  artery. 

b.  The  left  axillary  artery  only  differs  from  the  right  in  the  disposition  of  the  superior 
cervical,  dorsal,  and  vertebral  arteries,  which  have  distinct  origins ;  the  two  last  are  very  close 
to  each  other,  and  the  first  furnishes  the  subcostal  branch. 

3.  Axillary  Arteries  of  Carnivora. 

These  arise  separately  from  the  convexity  of  the  arch  of  the  aorta,  as  in  the  Pig,  and 
furnish  successively,  besides  the  carotids,  special  branches  of  the  axillary  artery  trunk : — 

1.  A  voluminous  trunk,  the  common  origin  of  the  dorsal,  superior  cervical,  and  subcostal  or 
superior  intercostal  arteries.  The  first  passes  between  the  two  anterior  ribs ;  the  second  in 
front  of  the  first ;  the  third  across  the  internal  face  of  the  first,  second,  and  third  ribs,  near 
their  cartilages,  where  it  emits  ascending  and  descending  intercostal  branches. 

2.  The  vertebral  artery,  anastomosing,  as  in  Solipeds,  with  a  retrograde  branch  from  the 
occipital  artery ;  it  supplements,  in  very  great  part,  the  superior  cervical,  the  volume  of  which 
is  diminutive ;  it  is  only  distributed  to  the  superior  part  of  the  neck. 

3.  The  inferior  cervical  artery,  giving  off"  the  pectoral  branches. 

4.  The  internal  thiracic  artery,  remarkable  for  its  large  volume,  and  for  a  superficial 
division  cliiefly  destined  to  the  mammae,  which  joins  an  analogous  branch  from  the  external 
pudic  artery. 

5.  An  external  thoracic  branch,  the  origin  of  which  more  resembles  that  of  the  supra- 
scapular artery,  which  appears  to  be  absent. 

6.  The  subscapular  artery. — After  furnishing  this  vessel,  the  axillary  is  continued  by  the 
humeral  artery,  which  we  will  now  examine  in  detail. 

Humeral  Artery. — Placed  at  first  immediately  behind  the  biceps  muscle,  this  vessel 
descends  beneath  the  pronator  teres,  and  divides  at  the  superior  extremity  of  the  radius  into 
two  terminal  brunches— the  ulnar  and  radial  arteries. 

It  detaches  on  its  course  collateral  branches,  analogous  to  those  which  have  been  described 
for  Solipeds,  and  among  which  is  a  thin  vessel — a  vestige  of  the  anterior  radial  artery,  that 
passes  beneath  the  terminal  extremity  of  the  biceps  to  supply  the  muscles  covering,  anteriorly, 
the  articulation  of  the  elbow. 


THE  BRACHIAL   OR   AXILLARY  ARTERIES.  659 

Ulnar  artery.— 'Much  smaller  than  the  radial,  this  vessel  gives  off,  near  its  origin,  the 
interosseous  artery,  wliich  sometimes  proceeds  directly  from  the  humeral  artery,  and  the  calibre 
of  which  always  exceeds,  in  animals,  that  of  the  ulnar  artery.  The  latter  is  directed  obliquely 
outwards  and  downwards,  passing  under  the  perforans,  and  gains  the  internal  face  of  the 
anterior  ulnar  or  oblique  flexor  of  the  metacarpus,  where  it  lies  beside  the  ulnar  nerve,  to 
descend  with  it  inside  the  unciform  bone,  and  join  the  posterior  interosseous  artery,  or  one  of 
its  terminal  branches.  On  its  track  it  gives  off  a  number  of  muscular  or  cutaneous  branches, 
several  of  which  anastomose  with  the  internal  collateral  artery  of  the  elbow,  as  well  as  with 
divisions  of  the  radial  artery. 

Interosseous  artery — This  artery  is  placed  between  the  ulna  and  radius,  underneath  the 
pronator  quadratus,  and  is  prolonged  to  the  lower  third  of  the  forearm,  where  it  separates 
into  two  branches — the  anterior  and  posterior  interosseous  arteries,  after  throwing  off  on  its 
way  several  branches,  mostly  anterior,  which  enter  the  antibrachial  muscles  by  traversing  the 
space  comprised  between  the  two  bones  of  the  forearm,  the  principal  escaping  by  the  radio- 
ulnar arch. 

The  anterior  interosseous  artery,  after  passing  between  the  radius  and  ulna,  descends  on 
the  anterior  face  of  the  carpus,  where  its  divisions  meet,  inwardly,  the  collateral  rauiuscules 
of  the  radio-palmar  artery,  and  outwardly,  the  arborizations  of  a  branch  from  the  posterior 
interosseous  artery,  forming  with  these  vessels  a  wide-meshed  plexus,  from  which  definitely 
proceed  several  filaments  that  join  the  dorsal  interosseous  metacarpal  arteries. 

The  posterior  interosseous  artery  may  be  regarded,  by  its  volume  and  direction,  as  the 
continuation  of  the  interosseous  trunk.  After  emerging  from  beneath  the  pronator  quadratus, 
it  detaches  an  internal  flexuous  branch  anastomosing  with  the  radio-palmar  artery,  then 
several  external  musculo-cutaneous  branches;  after  which  it  is  placed  within  the  pisiform 
bone,  where  it  divides  into  two  branches,  after  receiving  the  ulnar  artery.  The  smallest  of 
these  branches  anastomoses  by  inosculation  with  the  superficial  palmar  arch  ;  the  other,  larger 
and  deeper  seated,  is  carried  in  front  of  the  flexor  tendons,  beneath  the  aponeurosis  covering 
the  interosseous  muscles,  across  the  superior  extremity  of  these,  and  so  forming  the  deep 
palmar  arch,  which  unites  with  a  thin  filament  from  the  radio-palmar  artery.  This  arch 
supplies,  with  some  ramuscules  destined  to  the  muscles  of  the  hand  (or  paw),  eight  inter ossf.ous 
metacarpal  arteries— four  posterior  or  palmar,  wliich  are  united  by  their  inferior  extremity 
with  the  collaterals  of  the  digits,  after  giving  several  divisions  to  the  muscles  of  the  hand ;  and 
four  anterior  or  dorsal,  traversing  the  superior  extremity  of  the  intermetacarpal  spaces,  like 
the  perforating  arteries  in  Man,  joining  the  anterior  interosseous  branches  of  the  forearm,  and 
descending  afterwards  into  the  intermetacarpal  spaces,  to  unite  with  the  collateral  arteries  of 
the  digits  at  the  metacarpo-phalangeal  articulations.  • 

Radial  artery — the  posterior  radial  of  the  other  animals.  Lying  alongside  the  long  flexor 
of  the  thumb  and  the  perforans  muscle,  this  artery  follows  the  inner  face  of  the  perforatus 
muscle,  and  curving  outwards  to  be  united  to  a  branch  from  the  posterior  antibrachial  inter- 
osseous artery,  formg  the  superficial  palmar  arch,  from  which  escape  four  branches — the 
palmars  or  collaterals  of  the  digits.  Tliese  are  at  first  situated  between  the  perforatus  and 
perforans  tendons,  and  reach  tlie  superior  extremity  of  the  interdigital  spaces,  where  they 
receive  the  metacarpal  interosseous  arteries,  and  comport  themselves  in  the  following  manner : 
the  internal  goes  to  the  thumb ;  the  second — counting  from  within  outwards— gains  the  con- 
centric side  of  the  index;  the  third,  the  largest,  divides  into  two  branches  which  lie  alongside 
the  great  digits  ;  the  last  goes  to  the  external  digit. 

Comparison  of  the  Axillary  Arteries  in  Man  with  those  of  Animals. 

The  arteries  of  the  thoracic  limbs  and  liead  arise  separately  from  the  arch  of  die  aorta ; 
consequently,  in  Man  there  is  no  anterior  aorta. 

The  vessel  of  the  liinb  that  represents  the  axillary  of  animals  is  here  resolved  into  two 
portions  :  the  subclavian  artery  and  axillary  artery. 

The  Subclavian  Artery  has  not  the  same  origin  on  both  sides;  on  the  right  it  arises 
from  the  aorta  by  a  trunk  common  to  it  and  the  carotid  of  that  side — the  arteria  innominata; 
while  the  left  is  detached  separately  from  the  most  distant  part  of  the  aoriic  aruh.  The 
subclavian  vessels  extend  to  the  inferior  border  of  the  clavicles,  and  furnish  seven  important 
collateral  branches,  wliich  are  present  in  the  domesticated  animals.     They  are — 

1.  The  vertebral  artery,  situated  in  the  vertebral  foramina  of  the  cervical  vertebrae,  as  far 
as  the  axis ;  there  it  anastomoses,  as  in  Solipeds,  with  a  branch  of  the  carotid,  enters  the 
spinal  canal  by  the  ioramen  magnum,  and  unites  with  its  fellow  at  the  lower  border  of  the 
pons  Varolii  to  form  the  basilar  artery  which,  in  the  Horse,  comes  from  the  cerebro-spinal 
artery  of  the  occipital. 


660 


THE  ARTERIES. 


Fig.  379. 


2.  The  inferior  thyroid,  the  origin  of  which,  and  some  branches,  we  find  in  the  ascending 
branch  {ascending  cervical)  of  the  inferior  cervical  artery  in  the  Horse. 

3.  The  internal  mammary  artery  divides  into  two  branches 
at  the  xiphoid  cartilage  of  tiie  aterauni. 

4.  The  superior  intercostal  artery,  the  analogue  of  which  we 
866  in  Solipeds,  in  the  subcostal  branch  of  the  dorsal. 

5.  The  supra-scapular  artery,  present  in  all  animals  and  dis- 
posed in  the  same  manner. 

6.  The  transcerse  cervical  (transversa  colli),  represented  by 
the  extra-thonicic  branches  of  the  dorsal  artery. 

The  Axillary  Artery,  or  extra-thoracic  portion  of  the 
subclavian  trunk,  extends  to  the  external  border  of  the  pectoral 
muscle,  where  it  is  continued  by  the  humeral  artery.  The 
axillary  gives  off:  the  thoracica  acromialis,  resembling  tlie  de- 
scending branch  of  the  inferior  cervical  artery  of  large  quad- 
rupeds;  the  external  mammary ;  subscapular;  and  posterior  and 
anterior  circumflex,  branches  of  the  preceding  in  Solipeds. 

Humeral  (Brachial)  Artery, — This  artery  extends  from 
the  external  border  of  tlie  pectoral  muscle  to  the  bend  of  the 
elbow :  here  it  divides  into  two  terminal  branches — the  ulnar 
and  radial. 

In  its  course  it  gives  off  several  muscular  braiches,  and  an 
external  and  internal  collateral  of  the  elbow  (coUuteralis  ulnaris 
superior  and  inferior).  In  the  lower  third  of  the  arm,  the 
brachial  artery  is  comprised  between  the  brachialis  anticus  and 
inner  border  of  the  biceps  ;  so  that,  during  flexion,  and  especially 
active  and  forced  flexion,  of  the  forearm  on  the  arm,  in  vigorous 
sulijects,  the  circulation  is  arrested  in  the  vessels  of  the  hand. 

The  radial  artery  oi  Man  is  represented  in  the  Horse  by  the 
posterior  radial  artery.  It  is  directed  downward  and  a  little 
inward,  supposing  the  hand  to  be  in  a  state  of  pronation  ;  it 
crosses  the  carpus  in  front  of  the  trapezium  and  scaplioides,  at 
the  bottom  of  the  anatomical  snuft-box,  and  beneath  tlie  flexor 
tendons  of  the  phalanges  forms  the  deep  palmar  arch,  finally 
anastomosing  with  a  branch  of  the  ulnar  at  the  hypothenar 
eminence.  Along  its  course  it  furnishes  muscular  branches : 
the  carpea  anterior ;  radio-palmar,  which  passes  outwards,  and 
unites  with  a  branch  of  the  ulnar  artery  to  form  the  superficial 
palmar  artery  ;  the  dursalis  pollicis ;  the  carpea  posterior,  which 
concurs  in  the  formation  of  the  dorsal  arch  of  the  carpus,  that 
gives  origin  to  the  dorsal  interosseous  branches. 

The  ulnar  artery,  formed,  in  Solipeds,  by  the  anterior  radial, 
passes  downward  and  outward;  it  is  at  first  covered  by  the 
great  pronator  muscles,  great  and  small  palmar,  and  superficial 
flexor ;  lower,  it  is  only  protected  by  the  antibrachial  aponeurosis 
and  the  skin.  On  the  anterior  face  of  the  carpus,  it  passes 
within  the  pisiform  bone,  and  anastomoses  with  the  radio-palmar 
artery ;  whence  results  the  superficial  palmar  arch.  It  gives 
rise  to  two  recurrent  arteries  that  ascend  to  receive  the  collateral 
vessels  of  the  elbow,  then  to  a  trunk  seen  in  animals,  and  which 
divides  into  the  anterior  and  posterior  interossece. 

The  three  arches  in  the  vicinity  of  the  carpus,  the  constitu- 
tion of  which  has  been  already  given,  are  distributed  in  the 
following  manner : — 

The  superficial  palmar  arch  is  situated  at  the  surface  of  the 
flexor  tendons ;  from  its  convexity  it  emits  four  or  five  meta- 
carpal branches:  the  first  reaches  the  external  border  of  the 
little  finger  as  the  external  collateral  of  that  organ ;  the  other 
four  are  lodged  in  the  interosseous  spaces,  and  when  they  reach 
the  roots  of  the  fingers  they  bifurcate  and  form  the  external 
or  internal  collateral  arteries  of  the  five  fingers.  The  deep 
palmar  arch  furnishes:    articular  branches  to  the  wrist,  the 


AbTKRIES   OF   THE    HUMAN 
FOREARM. 

.,  Lower  part  of  biceps;  2, 
inner  condyle  of  humerus ; 
3,  deep  portion  of  pronator 
radii  teres;  4,  supinator 
longus ;  5,  flexor  longus 
pollicis ;  6,  pronator  quad- 
ratus  ;  7,  flexor  profundus 
digitorum  ;  8,  flexor  carpi 
ulnaris ;  9,  annular  liga- 
ment ;  10,  brachial  artery  ; 
11,  anastomotica  longus 
magna,  inosculating  above 
with  the  inferior  profunda, 
and  below  with  the  anterior 
ulnar  recurrent;  12,  radial 
artery;  13,  radial  recurrent, 
inosculating  with  the  supe- 
rior profunda  ;  14,  super- 
ficialis  vohx  ;  15,  ulnar  ar- 
tery ;  16,  superficial  palmar 
arch,  giving  off  digital 
branches  to  three  fingers 
and  a  half;  17,  magna 
pollicis  and  radialis  indicis  ; 
18,  posterior  ulnar  recur- 
rent; 19,  anterior  inter- 
osseous; 20,  posterior  inter- 
osseous. 


THE  COMMON  CAROTID  ARTERIES.  661 

perforating  tranches  which  cross  the  interosseous  spaces  to  unite  with  the  dorsal  interossese ; 
the  palmar  interossea;,  which  join  the  superficial  interossese  before  their  division  into  collateral 
branches.  Lastly,  the  carpal  dorsal  arch  gives  off  the  dorsal  interossea,  which  receive  per- 
forating filaments  above  and  below  tlie  metacarpus,  and  are  expended  in  the  articulations  and 
skin  of  the  fingers. 

Article  VII. — Common  Carotid  Arteries  (Figs.  375,  14 ;  381,  1). 

These  two  vessels  (named  from  Kdpa,  the  head)  ^  arise  from  the  right  axillary 
artery,  at  a  short  distance  from  its  origin,  by  a  common  trunk— the  cephalic 
artery — which  is  detached  at  a.  very  acute  angle,  and  is  directed  forward  beneath 
the  inferior  face  of  the  trachea,  and  above  the  anterior  vena  cava,  to  terminate 
near  the  entrance  to  the  chest  by  a  bifurcation  that  commences  the  two  common 
carotids — right  and  left. 

Each  of  these  arteries  afterwards  ascends  in  a  sheath  of  connective  tissue, 
along  the  trachea,  at  first  beneath  that  tube,  then  at  its  side,  and  finally  a  little 
above  its  lateral  plane.  Each  carotid  arrives  in  this  way  at  the  larynx  and 
guttural  pouch,  where  it  divides  into  three  branches. 

In  its  course,  this  vessel— independently  of  the  connection  between  it  and  the 
trachea — has  the  following  relations  : — 

Throughout  its  entire  length,  it  is  accompanied  by  the  cord  that  results  from 
the  union  of  the  pneumogastric  nerve  with  the  cervical  portion  of  the  sympa- 
thetic, and  by  the  recurrent  nerve  ;  the  latter  is  placed  below  or  in  front  of  the 
vessel,  from  which  it  is  somewhat  distant  in  the  lower  part  of  the  neck  ;  the 
first  is  situated  above  or  behind  the  artery,  and  lies  close  to  it. 

It  is  also  related  :  behind,  in  its  upper  two-thirds,  to  the  longus  colli  and  the 
rectus  capitis  anticus  major  ;  outwardly,  to  the  scalenus  towards  the  inferior 
extremity  of  the  neck,  and  to  the  subscapulo-hyoideus,  which  separates  the 
artery  and  jugular  vein  in  the  middle  and  upper  part  of  the  neck.  But  near  the 
entrance  to  the  chest  these  two  vessels  are  in  direct  relationship — the  vein  below 
and  the  artery  above. 

It  is  also  to  be  noted,  that  the  glands  at  the  entrance  of  the  chest  are  in 
contact  with  the  carotids,  and  that  the  left  artery  is  related,  besides,  to  the 
oesophagus. 

Collateral  Branches. — The  branches  furnished  by  the  common  carotid 
on  its  course  are  somewhat  numerous,  but  they  are  of  such  inconsiderable 
diameter  that  their  successive  emission  does  not  sensibly  vary  the  calibre  of  the 
vessel  from  which  they  emanate  ;  so  that  the  carotids  represent,  from  their  origin 
to  their  termination,  two  somewhat  regular  cylindrical  tubes.  These  collateral 
branches  are  destined  either  to  the  muscles  of  the  cervical  region,  or  to  the 
oesophagus  and  trachea.  Two  of  them — the  thyro-laryngeal  and  accessory  thyroid 
arteries — will  occupy  us  in  a  special  manner. 

Thyro-laryngeal  Artery  (Fig.  381, 14"). — This  vessel,  which  corresponds 
exactly  to  the  superior  thyroid  artery  of  Man,^  arises  from  the  common  carotid  at 
a  short  distance  from  its  termination,  a  little  behind  the  larynx  or  above  the 
thyroid  body  ;  it  passes  on  that  organ,  into  which  it  enters  by  two  principal 
branches  that  turn  round  its  superior  extremity  and  anterior  border,  after  sending 
two  branches  to  the  larynx — a  superior,  also  for  the   pharyngeal  walls  ;    and 

'  Baillet  has  remarked  that  the  two  common  carotid  arteries  have  not  the  same  calibre  In 
the  Horse. 

*  We  would  have  given  it  the  same  name  if  we  could  have  found  the  true  representative  of 
the  inferior  thyroid  artery. 


662  THE  AETERIES. 

an  inferior,  much  more  considerable,  exclusively  distributed  to  the  laryngeal 
apparatus.  The  latter  passes  between  the  cricoid  and  the  posterior  border  of 
the  thyroid  cartilage,  on  the  internal  surface  of  which  it  sends  off  several 
ramuscules,  some  of  which  pass  forwards,  others  backwards — the  latter  spreading 
over  the  ventricle  of  the  glottis  and  the  thyro-arytfeuoid  muscle,  to  become 
expended  in  the  arytenoid  muscle.  The  superior  branch  for  the  pharynx,  also 
supplies  the  crico-arytjenoideus. 

It  sometimes  happens  that  the  thyro-laryngeal  artery  is  found  divided  at  its 
origin  into  two  quite  distinct  branches,  each  furnishing  a  laryngeal  and  a  thyroid 
division,  as  in  Fig;.  381,  3.^ 

We  have  already  remarked  on  the  disproportion  existing  between  the  con- 
siderable calibre  of  the  branches  sent  by  this  artery  to  the  thyroid  body,  and  the 
slender  volume  of  that  organ  ;  so  that  it  will  at  present  suffice  to  remind  the 
student  of  this  peculiarity. 

Accessory  Thyroid  Artery  (Figs.  375,  14' ;  381,  2).— The  origin  of  this 
vessel  precedes  that  of  the  first  ;  it  is  much  smaller,  and  enters  the  thyroid  body 
by  the  posterior  or  inferior  extremity  of  this  glandiform  lobe. 

This  artery  often  sends  only  some  excessively  fine  ramuscules  to  the  thyroid 
body,  and  expends  itself  almost  entirely  in  the  cervical  muscles.^ 

Tebminal  Branches. — The  three  branches  which  terminate  the  common 
carotid  are  the  occipital,  and  infernal  and  extermd  carotid  arteries ;  the  latter  is 
incomparably  larger  than  the  other  two,  which  only  appear  to  be  collateral 
offshoots  from  the  principal  vessel.  It  is  these  branches  which  distribute  the 
blood  to  the  various  parts  of  the  head.  We  will  devote  three  special  paragraphs 
to  their  study  ;  but  'their  preparation  will  previously  demand  some  notice. 

Preparation  of  the  arteries  of  the  head. — After  carefully  removing  the  skin,  dissect  the 
superficial  arteries  of  one  side — that  is,  the  externul  maxillar}-,  maxillo-muscular,  the  temporal 
trunk,  and  the  posterior  auricular  arteries — excising  the  parotid  gland  to  expose  the  origin  of 
the  three  last-named  vessels.  On  the  opposite  side,  the  deep  arteries  are  prepared,  after  dis- 
posing of  the  branch  of  the  inferior  maxilla,  as  in  the  preparation  of  the  muscles  of  the 
TONGUE ;  tlie  orbital  and  zygomatic  processes  being  removed  in  three  sections  with  the  saw,  as 
in  Fig.  381,  which  will  serve  as  a  guide  in  the  dissection  of  all  these  arteries. 

It  is  possible  to  prepare  all  the  arteries  on  one  side  ;  and  in  order  to  do  this,  a  commence- 
ment should  be  made  by  dissecting  the  superficial  branches;  after  which,  these  are  cut  in  the 
middle  of  tlieir  course  and  the  first  half  thrown  back  on  the  parotid.  The  facial  is  left  intact. 
Tiie  deep  arteries  are  reached  by  dividing  and  disposing  of  the  inferior  maxilla,  as  was  directed 
in  the  second  procedure  in  preparing  the  muscles  of  the  tongue  and  pharynx. 

Occipital  Artery  (Fig.  381,  6). 

The  occipital  artery  is  a  slightly  flexuous  vessel,  lying  alongside  the  upper 
third  of  the  internal  carotid.  It  ascends  beneath  the  transverse  process  of  the 
atlas,  in  passing  behind  the  guttural  pouch,  between  the  maxillary  gland  and 
the  straight  anterior  muscles  of  the  head.  It  then  insinuates  itself  between  the 
rectus  capitis  lateralis  and  the  inferior  arch  of  the  above-named  vertebra,  to  pass 
through  its  anterior  foramen,  and  terminate  by  two  branches,  after  coursing 
along  the  short  fissure  that  unites  this  foramen  with  the  superior  foramen.     In 

'  It  was  doubtless  a  case  of  this  kind  that  Rigot  had  before  him  when  he  described  the 
above  vessel,  and  made  two  arteries  of  it — tlie  thyroid  and  laryngeal.  But,  we  repeat,  this  is 
only  an  exceptional  instance,  and  does  not  authorize  its  being  supposed  to  be  the  rule,  and 
cause  the  creation  of  a  distinct  thyroid  and  laryngeal  artery;  since  each  branch  of  the  vessel 
is  distributed  to  the  larynx  and  thyroirl  borly  at  the  same  time. 

*  We  regard  it  as  the  analogue  of  the  middle  thyroid  of  Man. 


THE  COMMON   CAROTID  ARTERIES.  663 

its  track,  this  artery  is  crossed,  outwardly,  by  the  pneumogastric  and  spinal 
nerves,  and  the  occipital  nerve  of  the  great  sympathetic,  and  is  accompanied  by 
the  divisions  of  the  inferior  branch  of  the  first  pair  of  cervical  nerves. 

The  two  terminal  branches  of  the  vessel  are  the  occipito-muscular  and  cerebro- 
spinal arteries. 

The  collateral  branches  are  three  in  number,  and  in  the  order  of  their 
emission  are  named  :  1.  The  prevertebral  artery.  2.  The  mastoid  artery.  3. 
The  atloido-muscular  {ramus  anastomotims,  or  retrograde)  artery. 

Collateral  Branches. — 1.  Prevertebral  Artery  (Fig.  381,  9). — The 
smallest  of  all  the  branches  emanating  from  the  occipital,  this  artery  is  detached 
at  a  very  acute  angle,  and  immediately  divides  into  several  filaments,  some 
muscular,  the  others  meningeal.  The  majority  of  the  first  pass  between  the 
occipito-atloid  articulation  and  the  rectus  capitis  anticus  minor  muscle  of  the 
head,  and  expend  themselves  either  in  that  muscle,  or  in  the  rectus  capitis  anticus 
major  ;  the  second,  generally  two  in  number,  are  always  very  slender,  and  reach 
the  dura  mater  by  entering,  one  through  the  foramen  lacerum  basis  cranii,  the 
other  by  the  condyloid  foramen. 

Sometimes  the  prevertebral  artery  arises  from  the  common  carotid,  near  the 
occipital  and  internal  carotid. 

2.  Mastoid  Artery  (Fig.  381,  8). — This  vessel  arises  at  an  acute  angle 
above  the  preceding,  and  goes  towards  the  mastoid  foramen  by  creeping  on  the 
external  surface  of  the  styloid  process  of  the  occipital  bone,  beneath  the  obliquus 
capitis  anticus.  It  enters  the  parieto-temporal  canal  by  this  foramen,  to  anasto- 
mose by  inosculation  with  the  spheno-spinous  branch  of  the  internal  maxillary 
artery. 

In  its  course  it  describes  a  curve  downwards,  and  throws  off  a  large  number 
of  collateral  branches.  Among  these  are  some  which  originate  before  the  artery 
enters  its  bony  canal,  and  which  are  destined  for  the  muscles  of  the  nape  of  the 
neck.  Others  arise  in  the  interior  of  this  canal,  and  escape  from  it  by  the 
orifice  in  the  temporal  fossa,  to  expend  themselves  in  the  temporal  muscle. 
Some  ramuscules  reach  the  dura  mater. 

"We  have  seen  the  mastoid  artery  arise  directly  from  the  common  carotid, 
and  furnish  a  parotideal  branch.  We  have  also  found  it  passing  over  the 
surface  of  the  obliquus  capitis  anticus,  and  curve  suddenly  to  enter  the  parieto- 
temporal canal. 

3.  Atloido-muscular  (Ramus  Anastomoticus)  or  Retrograde  Artery 
(Fig.  381,  7). — This  branch  is  not  constant,  and  when  it  does  exist  it  presents 
a  variable  volume.  It  is  detached  from  the  occipital,  underneath  the  transverse 
process  of  the  atlas,  by  forming  with  the  parent  branch  a  right,  or  even  an 
obtuse  angle  ;  it  is  directed  backwards,  traverses  the  inferior  foramen  in  the 
transverse  process  of  the  atlas,  places  itself  beneath  the  atlo-axoid  muscle,  and  in 
a  flexuous  manner  advances  to  meet  the  vertebral  artery,  which  it  directly  joins, 
after  giving  off  some  branches  to  the  great  oblique  and  neighbouring  muscle. 
This  anastomosis  is  the  means  of  establishing  a  collateral  communication  between 
the  vertebral  artery  and  the  divisions  furnished  by  the  common  carotid  ;  so  that 
these  two  arteries  can  mutually  assist  or  supplant  each  other.^ 

Terminal  Branches. — 1.  Occipito-muscular  Artery  (Fig.  381,  10). — 
Covered  at  its  origin  by  the  obUquus  capitis  inferior,  the  occipito-muscular  artery 

'  In  a  Mnle  we  have  found  a  large  anastomosis  between  the  retrograde  and  mastoid 
arteries,  beneath  the  ala  of  the  atlas. 


664  THE  ARTERIES. 

is  directed  transversely  inwards  to  the  surface  of  the  rectus  capitis  posticus  major, 
and  soon  separates  into  several  branches — ascending  and  descending  :  these  are 
mixed  with  the  divisions  of  the  first  superior  cervical  branch,  all  of  which  go  to 
the  muscles  and  integuments  of  the  occipital  region.  The  descending  branches 
anastomose  with  the  terminal  divisions  of  the  superior  cervical  artery. 

2.  Cerebro-spinal  Artery. — This  vessel  enters  the  spinal  canal  by  the 
anterior  foramen  of  the  atlas,  traverses  the  dura  mater,  and  divides  into  two 
branches  on  the  inferior  face  of  the  spinal  cord.  Of  these  two  branches,  the 
anterior  is  united,  by  convergence,  with  the  analogous  branch  of  the  opposite 
artery  on  its  arrival  at  the  middle  of  the  inferior  surface  of  the  medulla  oblongata, 
and  so  forms  the  basilar  artery ;  the  other  passes  backwards,  and  constitutes  the 
origin  of  the  middh  spinal  artery,  by  anastomosing,  after  a  short  course,  with  the 
corresponding  branch  of  the  other  cerebro-spinal  artery.  There  results  from  this 
distribution  a  kind  of  vascular  lozenge,  situated  at  the  lower  face  of  the  medulla 
oblongata,  which  receives  in  its  middle  the  two  cerebro-spinal  arteries.  This 
regular  arrangement  is  not,  however,  always  observed  ;  these  arteries  may  unite 
at  the  posterior  extremity  of  this  lozenge,  as  is  shown  in  Fig.  889. 

Basilar  Artery. — This  is  a  single  vessel  that  creeps  in  a  somewhat  flexuous 
manner  on  the  inferior  face  of  the  medulla  oblongata,  beneath  the  visceral  arach- 
noid membrane,  and,  passing  over  the  pons  Varolii,  terminates  at  the  anterior 
border  of  this  portion  of  the  isthmus,  by  anastomosing  with  the  two  posterior 
cerebral  arteries  (Fig.  380,  11,  11). 

On  its  course  it  gives  off : 

1.  A  multitude  of  plexuous  ramuscules,  which  enter  the  substance  of  the 
medulla  oblongata  and  the  pons  Varolii,  or  are  distributed  to  the  roots  of  the 
nerves  emanating  from  the  medulla  oblongata. 

2.  The  posterior  cerebeUar  arteries — vessels  liable  to  numerous  anomalies  in 
their  origin.  They  usually  arise  from  the  basilar  artery  at  a  right  angle,  behind 
the  posterior  border  of  the  pons  Varolii,  and  bend  outwards — one  to  the  right, 
the  other  to  the  left — by  passing  along  the  surface  of  the  medulla  oblongata,  the 
external  border  of  which  it  thus  reaches  ;  they  are  then  inflected  backwards 
beneath  the  cerebellar  plexus  choroides,  whence  they  spread  their  ramifications  on 
the  lateral  and  posterior  parts  of  the  cerebellum. 

3.  The  anterior  cerebeUar  arteries — two  or  three  on  each  side,  only  one  of 
which  is  constant.  These  vessels  are  very  variable  in  their  disposition,  and  arise 
from  the  terminal  extremity  of  the  basilar  artery,  in  front  of  the  pons  Varolii, 
and  sometimes  even  from  the  posterior  cerebral  arteries.  Usually  united  in 
fasciculi,  they  are  directed  outwards  and  a  little  backwards  in  turning  roimd  the 
crura  cerebri,  and  plunge  into  the  anterior  part  of  the  cerebellum. 

4.  Two  branches  anastomosing  with  the  internal  carotid  artery.  These 
branches  are  not  constant,  and  are  most  frequently  met  with  in  the  Ass.  They 
begin  at  the  basilar  artery  in  front  of  the  posterior  border  of  the  pons  Varolii, 
traverse  the  dura  mater  to  enter  the  cavernous  sinus,  and  join  the  carotid  arteries 
at  their  second  curvature. 

Middle  Spinal  Artery. — A  very  long  vessel,  lodged  in  the  inferior  fissure 
of  the  spinal  cord,  and  measuring  the  whole  extent  of  that  organ,  which  it 
follows  from  before  to  behind.  It  is  from  this  artery  that  are  given  off  the 
branches  that  cover  with  their  arborizations  the  medullary  tissue,  or  penetrate  its 
substance.  This  emission,  which  ought  soon  to  exhaust  the  artery,  does  not, 
however,  sensibly  diminish  its  diameter  :  as  it  receives  on  both  sides,  during  its 


THE  COMMON  CAROTID  ARTERIES.  665 

course,  numerous  additional  vessels.  Two  series  of  ramuscules,  in  fact,  emanate 
either  from  the  vertebral,  intercostal,  lumbar,  or  sacral  arteries,  enter  the  spinal 
canal  by  the  intervertebral  foramina,  and  join  this  artery.  Generally,  however, 
they  do  not  pass  to  the  spinal  cord  until  they  have  anastomosed  with  each  other 
outside  the  dura  mater,  so  as  to  form  on  the  floor  of  the  vertebral  canal  two 
lateral  vessels  placed  beside  the  venous  sinuses,  and  united  by  transverse  anasto- 
moses ;  this  disposition  is  most  evident  in  the  cervical  region  of  the  Ox 
(Fig.  382). 

Internal  Carotid  Artery  (Figs.  380,  7  ;  381,  5). 

One  of  the  terminal  branches  of  the  common  carotid,  the  internal  carotid 
ascends  at  first  to  beneath  the  base  of  the  cranium,  outside  the  anterior  straight 
muscles  of  the  head,  and  bends  forward  to  reach  the  foramen  lacerum  basis 
cranii.  In  this  primary  portion  of  its  course,  it  is  suspended  in  a  particular 
fold  of  the  guttural  pouch,  margined  by  the  superior  cervical  ganglion,  ac- 
companied by  the  cavernous  branch  of  the  sympathetic  nerve,  and  crossed  in 
various  directions  by  the  nerves  that  form  the  guttural  plexus.  On  arriving  at 
the  middle  of  the  occipito-spheno-temporal  hiatus,  it  enters  the  cavernous  sinus, 
and  in  the  interior  of  that  cavity,  where  it  is  bathed  in  venous  blood,  describes 
two  successive  and  opposite  curvatures — the  first,  looking  forwards,  occupies  the 
carotid  fossa  in  the  sphenoid  bone  ;  the  second,  with  its  convexity  posterior,  at 
which  the  internal  carotid  receives  an  anastomosing  branch  from  the  basilar 
artery — which  branch  is  voluminous  and  nearly  constant  in  the  Ass;  but  is 
rare  and,  when  present,  very  slender  in  the  Horse.  After  the  last  inflection,  the 
two  internal  carotids  communicate  by  a  very  large  transverse  branch,  which  is 
always  flexuous,  often  reticulated,  and  leave  the  cavernous  sinus  in  crossing  the 
dura  mater,  to  gain  the  cranial  cavity. 

These  arteries  are  then  placed  at  the  sides  of  the  pituitary  gland,  within  the 
superior  maxillary  /nerve,  proceed  from  behind  forward,  and  terminate  in  two 
branches  before  reaching  the  optic  nerve.  One  of  these  branches  constitutes 
the  posfcrior  communicating  artery  ;  the  other  soon  bifurcates  to  form  the  middle 
and  anterior  cerebral  arteries. 

Posterior  Cerebral  Artery. — This  vessel  is  inflected  from  before  to 
behind,  to  one  side  of  the  pituitary  gland  (Fig.  380,  14),  and  anastomoses  behind 
it,  forming  on  the  crura  an  arch  which  is  often  reticulated,  and  which  receives 
the  basilar  artery  in  the  middle  of  its  convexity. 

A  multitude  of  hair-like  ramuscules  escape  from  this  artery  and  enter  the 
substance  of  the  crura  ;  but  the  principal  branches  it  emits  proceed  in  a  flexuous 
manner  inwards  and  backwards,  towards  the  great  cerebral  fissure,  and  terminate 
either  on  the  posterior  extremity  of  the  cerebral  hemisphere  or  in  its  interior — 
in  the  plexus  choroides,  or  even  in  the  cerebellum.  The  disposition  and  number 
of  these  branches  are  very  variable,  but  there  is  one  which  may  be  regarded  as 
constant ;  this  is  the  largest  of  all,  and  certainly  merits  the  designation  of 
posterior  cerebral  artery  (Fig.  380,  11). 

Middle  Cerebral  Artery. — This  vessel  separates  itself  from  the  anterior 
cerebral  artery,  external  to  the  optic  commissure,  is  lodged  in  the  fissure  of 
Sylvius,  passing  through  it  in  a  flexuous  manner,  and  at  its  extremity  separates 
into  several  branches  which  ramify  on  the  lateral  and  superior  faces  of  the  brain, 
and  anastomose  by  their  terminal  divisions  with  the  posterior  and  anterior 
cerebral  arteries. 


THE  ARTERIES. 


Anterior  Cerebral  Artery. — This  enters  immediately  above  the  optic 
commissure,  and  proceeds  inwards  to  unite,  in  the  middle  line,  with  the  opposite 
artery,  forming  with  it  a  single  vessel.     This  middle  artery  (or  arteria  corporis 


ARTERIES   OF   THE   BRAIN. 

B,  Medulla  oblongata;  p,  pons  Varolii;  L,  mastoid  lobule;  o,  olfactory  lobule;  C,  chiasma  of  the 
optic  nerves;  m,  mammillary  or  pisiform  tubercle  (corpus  albicans);  h,  pituitary  gland  (three- 
fourths  have  been  excised).  1,  1,  Cerebro-spinal  arteries;  2,  middle  spinal  artery;  a,  loxenge- 
shaped  anastomosis  of  the  two  cerebro-spinal  arteries,  from  which  result,  in  front — 4,  the  basilar 
artery  (usually  the  cerebro-spinal  arteries  arrive  in  the  middle  of  the  lozenge);  5,  5,  posterior 
cerebellar  arteries  ;  6,  anterior  ditto  ;  7,  internal  carotid  artery,  with  the  sigmoid  curve  it  makes 
in  the  cavernous  sinus  ;  8,  internal  carotid  on  the  sides  of  the  pituitary  gland  ;  9,  transverse 
reticulated  anastomosis  thrown  between  the  two  internal  carotids  behind  the  pituitary  gland ; 
10,  biiurcation  of  the  internal  carotid;  11,  11,  posterior  cerebral  arteries  anastomosing  behind 
the  corpus  albicans,  receiving  in  the  middle  of  this  anastomosis  the  two  terminal  branches  of  the 
basilar  artery;  12,  middle  cerebral  artery;  13,  anterior  cerebral  artery;  14,  posterior  com- 
municating artery. 

callosi)  enters  the  longitudinal  fissure  of  the  brain  by  bending  round  the  anterior 
extremity  of  the  corpus  callosum,  and,  after  a  short  course,  divides  into  two 
branches  which  pass  from  before  to  behind,  one  to  the  right,  the  other  to  the 


THE  COMMON  CAROTID  ARTERIES.  667 

left,  on  the  internal  face  of  the  hemispheres,  a  short  distance  from  the  corpus 
callosum,  and  near  the  posterior  extremity  of  that  great  commissure.  The 
branches  emitted  by  these  arteries— either  in  their  track  or  at  their  termination — 
anastomose  with  those  of  the  posterior  and  middle  cerebral  arteries,  as  well  as 
with  the  lobular  branch  of  the  ophthalmic. 

Before  uniting  in  a  common  trunk,  the  two  anterior  cerebral  arteries  receive 
the  meningeal  branch  of  the  ophthalmic,  the  calibre  of  which  often  even  sur- 
passes that  of  these  vessels. 

From  the  anastomosis  of  the  anterior  cerebral  arteries  and  the  posterior 
cerebral  with  the  terminal  branches  of  the  basilar  artery,  there  results  on  the 
inferior  surface  of  the  pons  Varolii  an  irregular  arterial  circle— the  circle  or 
polygon  of  Willis,  which  surrounds  the  pituitary  gland.  From  this  circle  are 
detached  six  groups  of  arterioles,  which  are  destined  to  supply  the  principal  grey 
masses  in  the  brain — the  corpus  striatum  and  optic  thalami. 

External  Carotid  Artery  (Fig.  381,  12). 

This  artery  ought  to  be  considered,  because  of  its  volume  and  direction,  as 
the  continuation  of  the  common  carotid.  It  is  directed  forward,  arrives  at  the 
posterior  border  of  the  great  cornu  of  the  os  hyoides,  passes  between  it  and  the 
stylo-hyoid  muscle,  and  is  inflected  so  as  to  form  an  elbow  which  is  turned 
forward,  and  afterwards  ascends  vertically  to  near  the  neck  of  the  condyle  of 
the  inferior  maxilla,  at  the  posterior  angle  of  the  hyoid  branch.  There  it 
bifurcates  to  give  rise  to  the  superficial  temporal  and  internal  maxillary  arteries. 

In  the  first  part  of  its  course — that  is,  from  its  origin  to  the  hyoid  bone — the 
external  carotid  artery  is  related  :  inwardly,  to  the  guttural  pouch  and  the 
glosso-pharyngeal  and  superior  laryngeal  nerves  ;  outwardly,  to  the  outer  belly 
of  the  digastric  muscle,  and  the  hypoglossal  nerve. 

In  its  second  portion,  it  is  comprised  between  the  guttural  pouch,  the  parotid 
gland,  the  great  cornu  of  the  os  hyoides,  and  the  inner  side  of  the  posterior 
border  of  the  inferior  maxilla. 

The  collateral  branches  this  artery  furnishes  are  three  principal — the  glosso- 
facial,  maxillo-muscular,  and  posterior  auricular.  But  it  also  gives  off  others 
of  less  importance,  which  are  distributed  to  the  guttural  pouch,  the  guttural 
glands,  and  the  parotid  gland. 


Collateral  Branches  of  the  External  Carotid. 

1.  Submaxillary,  Facial  (or  Glosso-facial)  Artery  (Fig.  381,  13). 

This  arises  from  the  external  carotid,  at  the  point  where  that  vessel  passes 
beneath  the  stylo-hyoid  muscle,  and  is  immediately  inflected  downwards  on  the 
side  of  the  pharynx,  between  the  posterior  border  of  the  large  cornu  of  the  hyoid 
bone  and  the  above  muscle.  It  passes  in  proximity  to  the  anterior  extremity  of 
the  maxillary  gland,  crossing  Wharton's  duct  outwardly,  and  leaves  the  deep 
situation  it  at  first  occupied,  to  become  more  superficial  in  the  submaxillary 
space,  where  it  rises  on  the  surface  of  the  internal  pterygoid  muscle,  and  is 
directed  forwards  to  the  maxillary  fissure.  Turning  round  this  fissure,  it  climbs 
on  the  cheek,  in  front  of  the  masseter  muscle,  to  above  the  maxillary  spine, 
where  it  terminates  in  two  small  branches. 


THE  ARTERIES. 


In  its  long  and  complicated  course,  the  submaxillary  artery  describes  a  semi- 
circle upwards,  and  is  very  naturally  divided,  for  the  study  of  its  relations,  into 

Fig.  381. 


ARTERIES   OF   THE   HEAD. 

1,  Common  carotid  artery;  2,  accessory  thyroid  artery,  3,  4,  thyro-laryngeal  artery,  divided  into 
two  branches ;  5,  internal  carotid  artery ;  6,  occipital  artery ;  7,  atloido-muscular  artery  at  its 
exit  from  the  inferior  foramen  of  the  atlas;  8,  mastoid  artery;  9,  prevertebral  artery;  10, 
occipito-musciilar  artery;  11,  terminal  extremity  of  the  vertebral  artery  joining  the  atloido- 
muscular  branch ;  12,  external  carotid  artery ;  13,  submaxillary  artery ;  14,  pharyngeal 
artery;  15,  lingual  artery;    16,  sublingual  artery;   17,  coronary,  or  inferior  labial  artery;    18, 


THE  COMMON  CAROTID  ARTERIES.  669 

three  portions — a  deep,  an  intermaxillary,  and  a  facial.  The  first,  or  deep 
portion,  accompanied  in  its  superior  moiety  by  the  glosso-pharyngeal  nerve,  is 
related,  outwardly,  to  the  internal  pterygoid  muscle  ;  inwardly,  to  the  guttural 
pouch,  the  hyo-pharyngeus,  hypoglossal  nerve,  middle  tendon  of  the  digastricus, 
the  hyo-glossus  brevis,  Wharton's  duct,  and  the  subscapulo-hyoideus.  The  inter- 
maxillary, or  middle  portion,  is  bordered  by  the  glosso-facial  vein,  lies  against 
the  pterygoideus  internus,  and  is  in  contact  with  the  submaxillary  glands.  The 
facial,  or  terminal  part,  is  lodged  at  its  commencement  in  the  maxillary  fissure, 
in  front  of  the  glosso-facial  vein  and  the  parotid  duct ;  it  ascends  with  these 
two  vessels  along  the  anterior  border  of  the  masseter,  on  the  depressor  labii 
inferioris  and  buccinator  muscles,  beneath  the  subcutaneous  and  zygomaticus 
muscles  and  the  ramifications  of  the  facial  nerve,  which  perpendicularly  crosses 
the  direction  of  the  artery. 

Terminal  Branches. — The  external  maxillary  artery  terminates  in  two 
small  branches  which  separate  from  each  other  at  an  obtuse  angle,  one  being 
directed  upwards,  the  other  downwards.  The  ascending  branch  passes  to  the 
surface  of  the  orbicularis  palpebrarum,  below  the  lachrymalis,  and  anastomoses 
with  the  divisions  of  a  palpebral  branch  emanating  from  the  supermaxillo-dental 
artery  (Fig.  381,  19).  The  descmding  branch  goes  to  the  false  nostril  and  the 
entrance  to  the  nasal  cavities,  by  creeping  beneath  the  levator  labii  superioris 
(Fig.  381,  20). 

Collateral  Branches. — These  are  five  principal  branches  :  1.  The  pharyn- 
geal. 2.  Lingual.  3.  Sublingual ;  all  of  which  arise  from  the  first  portion  of 
the  submaxillary  artery.  4.  The  inferior  and  superior  coronary  arteries,  emanat- 
ing from  the  facial  portion.  Besides  these,  there  are  a  great  number  of  inno- 
minate branches  of  secondary  importance,  which  proceed  to  the  neighbouring 
parts,  and  principally  to  the  maxillary  gland,  submaxillary  glands,  the  masseter 
muscle,  and  the  muscles  and  integuments  of  the  face.  We  will  content  ourselves 
with  merely  noting  the  existence  of  these  latter  branches. 

1.  Pharyngeal  Artery  (Fig.  381,  14). — This  arises  from  the  submaxillary, 
at  a  variable  distance  from  its  origin,  and  sometimes  even  in  the  angle  formed 
by  that  vessel  and  the  external  carotid  artery.  Whatever  may  be  its  commence- 
ment, it  is  always  directed  forwards,  passes  between  the  hyo-pharyngeus  muscle 
and  the  great  cornu  of  the  hyoid  bone,  and,  describing  some  flexuosities,  goes 
towards  the  pterygoid  process,  beneath  the  elastic  layer  which  covers  the  pterygo- 
pharyngeus  muscle.  It  terminates  in  the  soft  palate,  after  giving  off  on  its 
course  ascending  and  descending  branches,  which  expend  themselves  in  the  walls 
of  the  pharynx. 

2.  Lingual  Artery  (Fig.  381,  15). — As  considerable  in  volume  as  the 
parent  branch,  this  artery  is  detached  at  an  acute  angle  from  it,  at  the  extremity 
of  the  hyoid  cornu.  With  the  glosso-pharyngeal  nerve,  it  passes  beneath  the 
hyo-glossal  muscle,  crossing  the  small  branch  of  the  os  hyoides,  and  extends  to 
the  extremity  of  the  tongue  by  gliding  in  the  interstice  between  the  genio-glossus 


coronary,  or  superior  labial  artery ;  19,  superior  terminal  branch  of  the  external  maxillary 
artery;  20,  inferior  terminal  branch  of  ditto ;  21,  maxillo-muscular  artery;  22,  23,  posterior 
auricular  artery;  24,  superficial  temporal  artery;  25,  subzygomatic  artery;  26,  inferior  auricular 
artery;  27,  internal  maxillary  artery;  28,  inferior  dental  artery;  29,  fasciculi  of  pterygoid 
arteries;  30,  tympanic  artery;  31,  spheno-spinous  artery;  32,  deep  posterior  temporal  artery; 
33,  deep  anterior  temporal  artery;  34,  ophthalmic  artery;  35,  supra-orbital  artery;  36,  lachrymal 
artery  ;  37,  buccal  artery ;  38,  palatine  artery ;  39,  superior  dental  arteri  40,  orbital  branch  of 
that  vessel, 

45 


670  TEE  ARTERIES. 

and  hyo-,dossns  muscle,  whera  it  meets  the  branches  of  the  lingual  and  hypo- 
glossal nerves. 

Flexuous  in  its  course,  in  order  to  adapt  itself  to  the  elongation  of  the  tongue, 
the  lingual  artery  emits  a  very  great  number  of  collateral  branches,  which  escape 
perpendicularly  from  the  entire  periphery  of  the  vessel  ;  but  chiefly  above,  below, 
and  on  the  inner  side,  to  ramify  in  the  muscles  and  integuments  of  the  tongue. 

Running  parallel  to  each  other,  the  two  lingual  arteries  communicate  by  five 
transverse  ramuscules,  and  join  at  their  terminal  extremity,  which  becomes  very 
slender. 

3.  Sublingual  Artery  (Fig.  381,  16). — This  artery  has  its  origin  at  the 
anterior  extremity  of  the  submaxillary  gland,  and  runs  forward  along  the  external 
surface  of  the  mylo-hyoideus  muscle,  which  it  afterwards  crosses  towards  the 
posterior  extremity  of  the  sublingual  gland.  It  then  follows  the  inferior  border 
of  this  gland,  sending  into  it  numerous  branches,  and  after  giving  some  filaments 
to  the  genio-glossus  and  genio-hyoideus  muscles,  is  prolonged  on  the  sides  of 
the  frtenum  linguae,  where  it  ends  by  fine  ramuscules  in  the  buccal  mucous 
membrane. 

Among  the  branches  this  artery  detaches  before  attaining  the  sublingual 
gland,  it  is  necessary  to  distinguish  those  which  are  destined  to  the  mylo-hyoideus 
muscle,  some  of  which — the  descending — are  thin  and  irregular  :  the  others — 
ascending — being  long,  thick,  and  parallel  to  each  other. 

Sometimes  this  artery  does  not  reach  the  sublingual  gland  ;  it  then  remains, 
for  the  whole  of  its  extent,  external  to  the  mylo-hyoideus  muscle,  and  sends  its 
terminal  divisions  to  the  vicinity  of  the  symphysis  of  the  inferior  maxilla.  In  this 
case,  the  gland  receives  a  special  branch  from  the  lingual  artery,  a  circumstance 
which  is  usual  in  Man,  in  whom  this  artery  is  named  the  submental. 

4.  Coronary  or  Inferior  Labial  (Fig,  381,  17). — Springing  from  the 
glosso-facial  artery  at  an  acute  angle,  shortly  before  that  vessel  arrives  at  the 
depressor  labii  inferioris,  the  inferior  coronary  artery  passes  under  that  muscle, 
and  following  its  direction,  descends  into  the  texture  of  the  lower  lip,  where  it 
is  mixed  up  with  the  ramifications  of  the  mental  nerve,  and  where  it  terminates 
by  forming  a  very  fine  anastomotic  arch  with  the  vessel  of  the  opposite  side. 

In  its  track,  it  gives  branches  to  the  buccinator  and  depressor  labii  inferioris 
muscles,  and  to  the  tissues  of  the  lower  hp,  to  which  it  is  chiefly  destined.  In 
its  passage  near  the  mental  foramen,  it  receives  the  inferior  dental  artery  as  it 
leaves  that  opening. 

5.  Coronary  or  Superior  Labial  Artery  (Fig.  381,  18). — Smaller  than 
the  preceding  vessel,  and  often  altogether  rudimentary,  this  artery  is  detached 
from  the  principal  trunk  at  nearly  a  right  angle,  above  the  origin  of  the  dilator 
naris  lateralis,  and  sometimes  below  that  muscle.  It  subsequently  gains  the  upper 
lip,  along  with  the  infra-orbital  branches  of  the  superior  maxillary  nerve,  by 
passing  between  the  levator  labii  superioris  proprius  and  the  dilator  naris 
lateralis  :  it  then  terminates  in  forming  an  arch  by  inosculation  with  the  palato- 
labialis  artery. 

The  branches  it  gives  off  pass  to  the  external  ala  of  the  nose  and  the  textures 
of  the  upper  Up.  Some  are  expended  in  the  muscles  just  named,  and  in  the 
buccinator. 

2.  Maxillo-muscular  Artery  (Fig.  381,  21). 
The  maxillo-muscular  artery  is  a  vessel  that  does  not  appear  to  have  its 


THE  COMMON   CAROTID  ARTERIES.  671 

representative  in  Man.  It  emerges  from  the  external  carotid,  above  the  point 
where  it  is  inchided  between  the  large  cornu  of  the  os  hyoides  and  the 
stylo-hyoideus  muscle.  Remarkable  for  the  very  obtuse  angle  it  forms  at  its 
origin  with  the  principal  vessel,  it  descends  behind  the  posterior  border  of  the 
inferior  maxilla,  covered  by  the  parotid  gland.  It  then  divides  into  two  branches 
— a  deep  one,  which  goes  to  the  internal  pterygoid  muscle,  after  furnishing  some 
ramuscules  to  the  neighbouring  organs  ;  and  a  superficial  one,  which  turns  round 
the  posterior  border  of  the  maxiUa,  and  emerging  from  beneath  the  parotid 
gland,  above  the  insertion  of  the  stemo-maxiUaris  muscle,  plunges  into  the 
masseter,  and  expends  itself  in  the  body  of  that  muscle  by  several  branches  which 
anastomose  with  the  divisions  of  the  subzygomatic  artery. 

3.  PosTEEiOR  AuEicuLAR  Artery  (Fig.  381,  22). 

Third  collateral  branch  of  the  external  carotid,  the  posterior  auricular  artery 
arises  at  a  very  acute  angle  above,  and  a  little  behind,  the  preceding  vessel.  It 
ascends  beneath  the  parotid  gland,  behind  the  base  of  the  concha  of  the  ear, 
crosses  the  cervico-am-icular  muscles,  and  reaches  the  extremity  of  the  cartilage 
by  passing  underneath  the  skin  which  covers  its  posterior  plane. 

In  its  course,  it  emits  several  ascending  auricular  branches,  which  arise  at 
different  elevations  and  cover  the  concha  with  their  divisions.  Among  these  we 
ought  to  distinguish  the  first  (Fig.  381,  23)  ;  this  has  its  origin  at  the  temporal 
trunk,  and  soon  divides  into  two  branches — one,  profound,  after  sending  a  very 
thin  filament  into  the  middle  ear  by  the  stylo-mastoid  foramen,  passes  between 
the  external  auditory  canal  and  the  mastoid  process  to  enter  the  subconchal 
adipose  tissue  and  the  internal  scuto-auricular  muscle  ;  the  other,  superficial, 
embedded  in  the  parotid  tissue,  proceeds  to  the  external  side  of  the  concha,  and 
buries  itself  in  the  interior  of  that  cartilage,  along  with  the  middle  auricular 
nerve,  after  abandoning  some  external  ramuscules. 

From  these  auricular  branches  there  also  escape  a  multitude  of  parotideal  twigs. 

Terminal  Branches  of  the  External  Carotid. 

1.  Superficial  Temporal  Artery  or  Teaeporal  Truxe:  (Fig.  381,  25). 

This  is  the  smallest  of  the  two  terminal  branches  of  the  external  carotid. 
After  a  short  ascending  course  between  the  parotid  gland,  the  guttural  pouch, 
and  the  neck  of  the  maxillary  condyle,  behind  which  it  is  situated,  this  arteiy  is 
divided  into  two  branches  :  the  anterior  auricular  and  the  suhzygomatic. 

Anterior  Auricular  Artery  (Fig.  381,  26). — This  vessel  appears  to  be, 
not  only  by  its  voltune,  but  also  by  its  direction,  the  continuation  of  the  temporal 
artery.  Embraced,  near  its  origin,  by  the  facial  nerve  and  subzygomatic  branch 
of  the  inferior  maxillary  nerve,  it  rises  behind  the  temporo-maxillary  articulation 
and  supra-condyloid  process,  beneath  the  parotid  gland,  to  the  temporal  muscle, 
into  which  it  passes  after  emitting  parotideal  twigs  and  auricular  branches,  one 
of  which  penetrates  to  the  interior  of  the  concha,  while  the  others  are  expended 
in  the  anterior  muscles  of  the  ear  and  the  integuments  covering  these  muscles. 

Subzygomatic  Artery  (Fig.  381,  25 ). — More  considerable  than  the  anterior 
atiricular,  this  artery  disengages  itself  from  beneath  the  parotid  gland  by  turning 
round  the  posterior  border  of  the  maxilla,  along  with  the  nervous  anastomosis 
which  gives  rise  to  the  subzygomatic  plexus,  and  is  placed  above  that  anastomosis, 


672  THE  ARTERIES. 

beneath  aud  to  the  outside  of  the  afore-mentioned  condyle.  There  it  ends  in 
two  branches  of  equal  volume — a  superior  or  superficial,  and  an  inferior  or  deep, 
both  of  which  ramify  in  the  substance  of  the  masseter  muscle,  and  anastomose 
with  the  divisions  of  the  maxillo-muscular,  or  with  the  masseter  branches  of  the 
external  maxillary  arteries. 

The  superior  branch,  or  transverse  artery  of  the  face,  goes  towards  the  anterior 
border  of  the  masseter  muscle  in  a  fiexuous  manner,  close  to  the  zygomatic  ridge. 
At  first  lying  on  the  superficies  of  the  masseter,  it  afterwards  buries  itself  in  that 
muscle. 

The  inferior  branch,  or  masseteric  artery,  dips  in  among  the  deep  fasciculi  of 
the  masseter  muscle,  to  which  it  is  distributed,  along  with  the  masseteric  nerve. 
Near  its  origin,  it  communicates  with  the  deep  posterior  temporal  artery  by  a 
fine  ramuscule,  which  passes  into  the  sigmoid  notch.  In  Man  and  some  animals, 
this  artery  comes  from  the  internal  maxillary. 

2.  Inteenal  Maxillary  or  Gutturo-maxillary  Artery  (Fig.  381,  27). 

Situated  at  first  immediately  within  the  maxillary  condyle,  below  the  articu- 
lation of  the  jaw,  this  artery  passes  to  the  inner  side,  towards  the  entrance  of  the 
subsphenoidal  canal,  by  describing  two  successive  curvatures — the  first  backwards, 
the  other  forwards.  After  being  tnus  shaped  like  an  S,  it  travels  forward  along 
the  subsphenoidal  canal  to  the  orbital  hiatus,  and  then  reaches  the  maxillary 
hiatus,  where  it  is  designated  the  palato-labial  artery. 

In  order  to  study  its  relations,  the  course  of  this  artery  may  be  divided  into 
three  portions — a  posterior  or  guttural,  a  middle  or  sphenoidal,  aud  an  anterior 
or  infra-orbital.  The  postei-ior  portion  hes  on  the  internal  face  of  the  external 
pterygoid  muscle,  covered  inwardly  by  the  guttural  pouch,  and  crossed  outwardly 
by  the  inferior  maxillary  nerve  and  some  of  its  branches.  The  middle  division 
is  enveloped  by  the  bony  walls  of  the  subsphenoidal  canal.  The  anterior  portion, 
along  with  the  superior  maxillary  nerve,  passes  across  the  space  separating  the 
orbital  from  the  maxillary  hiatus,  by  creeping  along  the  palatine  bone,  beneath  a 
considerable  mass  of  fat. 

Collateral  Branches. — The  arteries  given  oflp  by  the  internal  maxillary 
on  its  course  are  eleven  principal.  Five  arise  from  the  first  portion  of  the 
vessel :  two  below,  the  inferior  dental  and  the  group  of  the  pterygoid  arteries  ; 
three  above,  the  tympanic,  spheno-spinous  (great  meningeal),  and  posterior  deep 
temporal. 

Two  escape  from  the  superior  portion  of  the  interosseous  or  sphenoidal 
division.  These  are  the  anterior  deep  temporal  and  ophthabnic  arteries.  Four 
commence  from  the  third  section  of  the  artery  :  two  inferior,  the  buccal  and 
palatine  ■  and  two  upper,  the  superior  dental  and  the  7msal. 

1.  Inferior  Dental  Artery  (Fig.  381,  28). — This  vessel — also  named  the 
maxillo-dental  artery — is  detached  at  a  right  angle  from  about  the  middle  of 
the  first  curvature  described  by  the  internal  maxillary.  It  travels  forward  and 
downward  between  the  two  pterygoid  muscles,  afterwards  between  the  internal 
one  and  the  maxillary  bone,  entering  with  the  inferior  maxillary  nerve  into  the 
dental  foramen,  through  the  whole  extent  of  which  it  passes.  Arrived  at  the 
mental  foramen,  it  separates  into  two  branches — a  deep  one,  which  continues 
the  interosseous  course  of  the  vessel,  to  be  distributed  to  the  roots  of  the  tusk  or 
tush,  and  the  three  adjoining  incisor  teeth  ;  the  other  superficial,  generally  very 
slender  and  even  capillary,  issuing  by  the  mental  foramen  with  the  terminal 


TEi:  COMMON  CAROTID  ARTERIES.  673 

branches  of  the  maxillary  nerve,  and  anastomosing  with  the  inferior  coronary 
artery. 

Before  penetrating  the  maxilla,  this  artery  furnishes  divisions  to  the  internal 
pterygoid  and  mylo-hyoid  muscles. 

In  the  interior  of  the  maxillo-dental  canal,  it  gives  off  diploic  branches,  as 
weU  as  twigs,  to  the  roots  of  the  molar  teeth  and  the  alveolar  membrane. 

2.  Pterygoid  Arteries  (Fig.  ;381,  29).— It  maybe  said,  in  a  general  manner, 
that  the  two  pterygoid  muscles  receive  their  arteries  from  all  the  vessels  passing 
near  them  ;  though  there  are  two,  and  sometimes  three,  branches  more  especially 
intended  for  them.  These  branches — or,  properly  speaking,  pterygoid  arteries — 
arise  from  the  middle  of  the  second  curvature  of  the  internal  maxillary,  either 
at  an  acute  or  right  angle,  and  enter  the  pterygoid  muscles,  after  a  short  course 
forward  and  downward  on  the  external  tensor  palati  muscle—  this,  and  its  fellow, 
the  internal  muscle,  also  receiving  some  branches. 

3.  Tympanic  Artery  (Fig.  381,  30). — A  very  thin  and  small,  but  constant 
artery,  gliding  along  the  surface  of  the  guttural  pouch,  accompanying  the 
tympano-lingual  nerve,  and  penetrating  the  tympanic  cavity  by  a  foramen 
situated  at  the  base  of  the  styloid  process  of  the  temporal  bone  (the  fissura 
Glaseri).  It  throws  off  ramuscules  to  the  wall  of  the  guttural  pouch  and  the 
trigeminal  nerve  ;  these  often  arise  directly  from  the  trunk  of  the  internal 
maxillary  artery,  beside  the  tympanic  branch. 

4.  Spheno-spinous  or  Great  Meningeal  Artery  (Fig,  881,  31). — Com- 
mencing at  an  obtuse  angle,  opposite  the  pterygoideal  vessels,  this  artery  lies 
against  the  sphenoid  bone,  near  the  temporal  insertion  of  the  tensor  palati 
muscles,  is  directed  backwards  and  upwards,  enters  the  cranium  by  the  foramen 
lacerum  basis  cranii,  outside  the  inferior  maxillary  nerve,  passes  beneath  the  dura 
mater,  and  soon  after  engages  itself  in  a  particular  foramen  in  the  parieto- 
temporal canal,  where  it  anastomoses  by  inosculation  with  the  mastoid  artery. 

Before  penetrating  this  canal,  the  spheno-spinous  artery  gives  off  a  meningeal 
branch,  the  ramifications  of  which,  destined  to  the  dura  mater,  stand  in  relief  on 
that  membrane,  and  creep  along  in  the  small  grooves  channeled  on  the  inner 
surface  of  the  cranium. 

The  volume  of  this  vessel  is  subject  to  the  greatest  variations,  and  is  always 
in  an  inverse  proportion  to  that  of  the  mastoid  artery. 

5.  Posterior  Deep  Temporal  Artery  (Fig.  381,  32). — This  arises  at  a 
right  angle,  immediately  before  the  entrance  of  the  internal  maxillary  artery  into 
the  subsphenoidal  canal.  It  ascends  on  the  temporal  bone,  in  the  temporal 
muscle,  passing  in  front  of  the  temporo-maxillary  articulation,  which  it  turns 
round  to  be  inflected  backwards.  Tliis  vessel  communicates  with  the  masseteric 
artery  by  a  fine  division,  which  traverses  the  sigmoid  notch  in  the  maxillary 
bone. 

6.  Anterior  Deep  Temporal  Artery  (Fig.  381,  33). — Springing  at  a 
right  angle,  like  the  preceding,  in  the  interior  of  the  subsphenoidal  canal,  this 
artery  escapes  by  the  superior  branch  of  that  conduit,  ascends  against  the  bony 
wall  of  the  temporal  fossa,  along  the  anterior  border  of  the  temporal  muscle, 
in  which  it  is  almost  entirely  expended.  It  gives  some  ramuscules  to  the  adipose 
tissue  of  the  temporal  fossa.  Its  terminal  extremity  arrives  beneath  the  internal 
parieto-auricularis  muscle,  and  ramifies  in  it  and  in  the  skin  of  the  forehead. 

7.  Ophthalmic  Artery  (Fig.  381,  34). — This  vessel  has  a  somewfiat 
singular  arrangement.     After  being  detached  from  the  internal  maxillary  in  the 


674  TEE  ARTERIES. 

subsphenoidal  canal,  in  front  of  the  deep  anterior  temporal  artery,  with  which 
it  is  sometimes  united,  it  penetrates  by  the  orbital  hiatus  to  the  bottom  of  the 
ocular  sheath  ;  it  then  enters  the  cranium  by  the  orbital  foramen,  after  describing 
a  loop  opening  backwards  and  downwards,  which  passes  between  the  muscles  of 
the  eye,  beneath  the  superior  rectus,  and  abov^e  the  optic  nerve  and  the  sheath 
formed  around  it  by  the  retractor. 

Entering  the  cranium,  the  ophthalmic  artery  passes  inward  along  a  groove 
in  the  ethmoidal  fossa,  and  terminates  by  two  branches — a  meningeal  and  a 
nasal. 

Collateral  tranches. — In  its  orbital  track,  the  ophthalmic  artery  emits 
numerous  collateral  branches,  which  arise  from  the  convex  side  of  the  loop 
described  by  this  vessel.  These  are  :  the  muscular  arteries  of  the  eye,  the  ciliary, 
mitral  artery  of  the  7-etina,  supra-orbital,  and  lachrymal  arteries. 

In  its  cranial  portion,  it  furnishes  the  cerebral  branches. 

The  muscular  arteries  of  the  eye  have  a  destination  sufficiently  indicated  by 
their  name.  Their  number  and  mode  of  origin  vary.  They  are  usually  two 
principal,  which  arise  directly  from  the  ophthalmic  artery,  and  others  of  a  smaller 
size  furnished  by  the  lachrymal  and  supra-orbital  branches. 

The  ciliary  arteries — destined  to  the  constituent  parts  of  the  globe  of  the  eye, 
but  chiefly  to  the  choroid  coat,  the  ciliary  processes,  and  the  iris — are  long  thin 
branches,  emanating,  for  the  most  part,  from  the  muscular  arteries. 

"We  only  mention  the  centralis  retince  artery  here  ;  as  it  and  the  ciliary 
arteries  will  be  described  when  we  come  to  study  the  visual  apparatus. 

The  supra-orbital  artery  ascends,  with  the  nerve  of  the  same  name,  against 
the  inner  wall  of  the  ocular  sheath,  to  gain  the  supra-orbital  foramen  ;  passing 
through  that  orifice,  it  is  distributed  to  the  frontal  and  supra-orbital  muscles, 
the  orbicularis  palpebrarum,  external  temporo-auricularis  muscle,  as  well  as  to 
the  integument  of  the  frontal  region  (Fig.  381,  35). 

The  lachrymal  artery  creeps  upwards  and  forwards,  between  the  muscles  of 
the  globe  of  the  eye  and  the  superior  wall  of  the  ocular  sheath,  to  terminate 
in  the  lachrymal  gland  and  the  upper  eyelid  (Fig.  381,  36). 

The  cerebral  branches  of  the  ophthalmic  artery  vary  in  number,  and  frequently 
there  is  only  one,  of  somewhat  considerable  volume.  They  pass  to  the  anterior 
extremity  of  the  cerebral  lobe,  and  anastomose  with  the  divisions  of  the  anterior 
cerebral  artery. 

Terminal  branches. — The  meningeal  branch,  after  detaching  ramuscules  to  the 
dura  mater,  and  particularly  to  the  falx  cerebri,  anastomoses  in  the  middle  line, 
below  the  process  of  the  crista  galli,  with  that  of  the  opposite  side,  and  after- 
wards joins  the  anterior  cerebral  artery. 

The  nasal  branch  traverses  the  cribriform  plate  of  the  ethmoid  bone,  and 
divides  into  a  number  of  ramuscules,  which  descend  either  on  the  ethmoidal  cells, 
or  on  the  middle  septum  of  the  nose,  where  their  ramifications  form  arterial  tufts 
of  a  pleasing  aspect. 

8.  Buccal  Artery  (Fig.  381,  37). — The  buccal  artery  emerges  at  an  acute 
angle  from  the  internal  maxillary,  a  short  distance  in  front  of  the  orbital  hiatus, 
and  descends  obliquely  between  the  maxillary  bone  and  the  superior  insertion 
of  the  internal  pterygoid  muscle,  terminating  in  the  posterior  part  of  the  molar 
glands,  and  in  the  buccinator  and  depressor  labii  inferioris  muscles. 

In  its  course  it  gives  some  insignificant  ramuscules  to  the  pterygoid  muscles, 
as  well  as  to  the  masseter,  and  a  long  branch  to  the  adipose  cushion  in  the  temporal 


THE   COMMON  CAROTID  ARTERIES.  675 

fossa.     The  latter  branch  sometimes  comes  directly  from  the  internal  maxillary 
artery. 

9.  Staphyline  Artery  (Fig.  381,  38).— A  very  thin  filament,  which  accom- 
panies the  staphyline  nerve  in  the  groove  of  the  same  name,  and  is  distributed 
to  the  soft  palate. 

10.  Superior  Dental  Artery  (Fig.  381,  39).— This  vessel— which  is  also 
named  the  supermaxillo-dental  artery — enters  the  superior  dental  canal,  arrives 
near  its  inferior  or  infra-orbital  opening,  and  then  divides  into  two  thin  branches. 
One  of  these  continues  in  the  same  course  in  the  supermaxillary  bone,  to  supply 
arterial  blood  to  the  alveoli  of  the  foremost  molars,  the  tusk,  and  the  incisor 
teeth  ;  the  other  {infra-orbital  branch)  passes  out  of  the  canal  with  the  terminal 
divisions  of  the  superior  maxillary  nerve,  and  communicates  on  the  forehead 
with  a  ramuscule  from  the  external  maxillary  artery. 

On  its  way,  the  superior  dental  artery  emits  several  collateral  branches,  the 
majority  of  which  commence  in  the  interior  of  the  dental  canal,  and  pass  either 
to  the  alveoli  of  the  posterior  molars,  the  tissue  of  the  bone,  or  the  membrane 
lining  the  sinuses.  One  of  these  branches — the  orbital,  and  the  largest — escapes 
from  the  principal  artery  before  its  entrance  to  the  superior  dental  canal,  creeps 
along  the  floor  of  the  orbit  towards  the  nasal  angle  of  the  eye,  whence  it  descends 
on  the  forehead,  after  giving  off  some  divisions  to  the  caruncle  of  the  eye,  the 
lachrymal  sac,  and  the  lower  eyelid. 

11.  Nasal  or  Spheno-palatine  Artery.— Situated,  at  first,  at  the  bottom 
of  the  maxillary  hiatus,  this  artery,  springing  at  a  right  angle  from  the  parent 
trunk,  traverses  the  spheno-palatine  foramen,  and  divides  into  two  terminal 
branches — an  external  and  an  internal — in  ramifying  on  the  walls  of  the  nasal 
cavity. 

Terminal  Beanch  of  the  Internal  Maxillary  Artery.  Palato- 
Labial  or  Palatine  Artery  (Fig.  215,  3).— A  continuation  of  the  internal 
maxillary,  this  vessel  at  first  traverses  the  palatine  foramen,  follows  the  palatine 
groove  to  near  the  superior  incisors,  is  then  inflected  inwards  above  a  small 
cartilaginous  process  (Fig.  215,  4),  and  vmites  on  the  middle  hne  with  the  artery 
of  the  opposite  side,  forming  an  arch  with  its  convexity  forwards,  from  which 
proceeds  a  single  trunk  that  passes  into  the  incisive  foramen. 

The  palatine  arteries,  in  their  advance,  furnish  a  series  of  branches  to  the 
anterior  part  of  the  soft  palate,  the  membranes  on  the  roof  of  the  mouth,  and 
the  gums  and  upper  teeth. 

The  single  trunk  resulting  from  their  anastomoses  is  placed,  immediately 
after  its  exit  from  the  incisive  foramen,  directly  beneath  the  buccal  mucous 
membrane,  and  at  once  divides  into  two  principal  branches — a  right  and  left ; 
these  are  lodged  in  the  tissue  of  the  upper  lip,  and  pass  back  to  meet  the  coronary 
arteries,  with  which  they  anastomose  by  inosculation,  after  throwing  off  on  their 
track  a  great  number  of  branches  to  the  muscles  and  integuments  of  the  lip  and 
nostrils. 

Differential  Characters  in  the  Carotid  Arteries  of  the  other  Animals. 
1.  The  Carotid  Arteries  in  Carnivora. 

In  the  Dog,  the  carotids  arise  singly  frona  the  axillary  artery,  and  ascend  beneath  the 
transverse  process  of  the  atlas,  along  the  trachea,  following  a  course  exactly  like  that  pursued 
by  these  vessels  in  the  Horse. 

Among  the  collatt  ral  branches  furnished  by  them,  maybe  distinguished  the  thyro-laryngeal 


676  TEE  ARTERIES. 

artery,  remarkable  for  its  enormous  calibrt',  its  descending  in  front  of  the  lateral  lobe  of  the 
thyroid  gland,  and  its  termination  in  the  median  isthmus  of  that  ghmd. 

The  terminal  branches  of  the  carotid  are,  as  in  Solipeds :  1.  The  occipital.  2.  The  in- 
ternal carotid.     3.  The  external  carotid,  the  continuation  of  the  common  cardtid. 

Occipital  Artery. — Inconsiderable  in  volume,  this  vessel  arises  in  front  of  the  anterior 
border  of  the  transverse  process  of  tlie  atlas,  passes  into  the  notch  on  its  border,  and  divides  into 
two  brandies — the  occipito-muscular  and  the  cerebrospinal  arteries. 

In  its  course,  it  gives  off  braticiies  analogous  to  those  which  emanate  from  the  prevertebral 
artery  of  tlie  Horse.  It  also  gives  a  mastoid  artery,  which  only  sends  one  very  small  branch 
into  the  paricto-temporal  canal,  and  is  destined  almost  exclusively  to  the  deep  muscles  of  the 
neck.    In  aildition,  the  occipital  throws  off  a  retrograde  artery,  which  directly  joins  the  vertebral. 

The  arrangement  of  the  occipital  artery  in  Oarnivora  is,  therefore,  almost  identical  with 
what  has  been  described  in  Solipeds. 

Internal  Carotid  Artery. — This  vessel  reaches  the  posterior  opening  of  the  carotid 
canal,  along  which  it  passes  forward,  then  describes  a  very  curious  flexure  which  leaves  the 
cranium  by  the  carotid  foramen  (see  p.  59),  theu  re-enters  that  cavity  after  receiving  a 
particular  branch  from  the  external  carotid.  It  afterwards  anastomoses  on  the  side  of  the 
pituitary  fossa,  with  the  divisions  of  the  spheno-spinous  artery  and  the  returning  briinches  of 
the  ophtiialmic  artery,  forming  a  kind  of  plexus  which  appears  to  be  a  trace  of  the  rtte  mirabile 
of  Ruminants  and  Pachyderms,  and  from  which  proceed  tlie  cerebral  arteries. 

External  Carotid  Artery. — This  arterial  branch  terminates,  as  in  Solipeds,  by  the 
superficial  temporal  and  the  internal  maxillary  arteries. 

It  gives  off  on  its  course :  1.  An  artery  representing  the  meningeal  branch  of  the  pre- 
vertebral of  the  Horse,  and  which  ascends  in  a  flexuous  manner  on  the  side  of  the  pharynx  to 
join  the  carotid  flexure. 

2.  A  laryngeal  artery,  entering  the  larynx  with  the  superior  nerve  of  that  organ,  after 
giving  ramuscules  to  the  maxillary  gland. 

3.  The  lingual  artery,  a  vt  ry  large  tortuous  branch,  the  course  of  which  resembles  that  of 
the  same  vessel  in  the  Horse. 

4.  A  facial  or  external  maxillary  artery,  divided  into  two  branches  above  the  inferior  inser- 
tion of  the  digastricus.  One  of  these  branches — analogous  perhaps  to  the  submental  of  Man- 
passes  within  this  insertion,  and  is  prolonged  to  the  chin,  after  furnishing  ramuscules  to  the 
parts  lodged  in  the  intermaxillary  space.  The  other  branch  winds  round  the  inferior  border  of 
the  maxilla,  in  front  of  the  masseter  muscle,  and  is  expended  on  the  face  by  ascending  and 
descending  branches,  among  which  we  can  readily  perceive  the  two  coronary  arteries,  and  the 
two  twigs  which  we  have  noticed  in  Solipeds  as  terminal  branches  of  the  vessel. 

.5.  The  posterior  auricular  artery,  after  detaching  parotideal  and  musculo-cutaneous  vessels, 
is  situated  on  the  middle  of  the  external  face  of  tlie  concha,  and  is  directed  towards  the  terminal 
extremity  of  the  cartilage,  where  it  separates  into  two  branches,  which  are  inflected  en  arcade^ 
and  return,  in  following  the  borders  of  the  concha,  towards  the  base  of  the  latter,  where  they 
anastomose  with  other  branches,  either  from  the  posterior  or  anterior  auricular,  and  which 
come  to  meet  them. 

Superficial  temporal  artery. — After  a  brief  course  behind  the  tempore i-maxillary  articulation, 
this  vessel  bifurcates :  its  posterior  or  auricular  branch  anastomosing  with  a  division  of  the 
posterior  auricular,  but  not  before  it  has  sent  ramuscules  to  the  interior  of  the  concha,  and 
furnished  some  uiusculo-cutaueous  twigs.  The  other,  the  anterior  or  temporal  branch,  glides 
beneath  the  aponeurosis  of  the  temporal  muscle,  above  the  upper  margin  of  the  zygomatic  arch, 
and  winds  upwards  and  inwards  around  the  outline  of  the  orbit,  to  terminate  on  the  face  by 
anastomosing  ramuscules,  either  with  the  infra-orbital  branch  of  the  superior  dental  artery,  or 
with  the  facial.  In  its  sub-epoueurotic  course,  it  gives  divisions  to  the  temporal  muscle. 
Above  the  orbital  arch,  it  emits  several  superficial  ascending  and  internal  twigs,  one  of  the 
principal  of  which  communicates  by  ramuscules  with  the  posterior  auricular  artery,  the 
auricular  branch  of  the  superficial  temporal,  and  with  the  homologous  ramuscules  from  the 
opposite  side. 

Internal  maxillary  artery. — The  course  pursued  by  this  vessel  is  similar  to  that  which  it  follows 
in  the  Horse.  After  describing  an  S  curvature  between  the  condyle  of  the  maxillary  bone  and 
external  pterygoid  muscle,  it  traverses  the  subsphenoidal  canal,  and  passes  outside  the  internal 
pterygoid  towards  the  maxillary  hiatus,  where  it  is  continued  by  the  superior  dental  artery. 

a.  The  following  are  the  principal  collateral  branches  emitted  by  this  vessel : 

1.  The  inferior  dental  artery. 

2.  The  deep  posterior  temporal  artery,  which  furnishes  a  masseteric  branch  that  traverses  the 
sigmoid  notch  in  the  maxillarv  bone,  to  enter  the  masseter  muscle. 


THE  COMMON  CAROTID  ARTERIES.  677 

8.  A  fine  tympanic  arteriole. 

4.  The  spheno-spinous  artery,  almost  entirely  destined  to  the  formation  of  the  plexus  of  the 
cerebral  arteries. 

5.  Several  pteryynid  arteries. 

6.  The  ophthalmic  artery,  which,  before  entering  the  ethmoidal  fossa  by  the  orbital  foramen, 
gives,  independently  of  the  branches  noted  in  Solipeds— except  the  supra-orbital,  which  is 
absent— a  fasciculus  of  particular  branches.  These  penetrate  the  cranium  by  the  great  sphe- 
noidal fissure,  accompanying  the  motor  and  sensory  nerves  of  the  eye,  to  join  the  internal 
carotid  and  spheno-spinous  arteries. 

7.  The  anterior  deep  temporal  artery. 

8.  A  staphyline  artery,  more  voluminous  than  that  in  the  Horse. 

9.  The  palatine  artery. 

10.  A  buccal  and  an  alveolar  artery,  the  principal  divisions  of  which  enter  Duvernoy's 
gland. 

b.  The  superior  dental  artery,  which  terminates  the  internal  maxillary,  and  furnishes  an 
orbital  and  an  infra-orbital  branch,  as  in  Solipeds.  The  latter,  remarkable  for  its  volume, 
emerges  from  the  superior  dental  canal  with  the  infra-orbital  nerves,  to  join  the  divisions  of  the 
external  maxillary  artery  on  the  face,  and  in  the  tissue  of  the  upper  lip. 

2.  Carotid  Arteries  in  the  Pig. 

There  is  nothing  particular  to  notice  regarding  the  course  of  these  vessels,  which  we  know 
arise  separately  from  the  axillary  artery. 

Occipital  Artery. — In  its  (listiibution,it  greatly  resembles  the  same  vessels  in  the  Horse 
and  Dog.  Its  most  important  branches  are  the  following  :  1.  A  very  small  retrograde  artery, 
anastomosing  with  tlie  vertebral.  2.  A  branch  which  ascends  into  the  muscles  of  the  neck, 
representing  the  mastoid  artery.  3.  Several  occipital  arterioles,  which  pass,  with  the  principal 
artery,  by  the  anterior  foramen  of  the  atlas.  This  artery  is  expended  in  a  complete  manner  in 
the  muscles  of  the  neck,  and  without  sending  a  cerebro-spinal  branch  to  the  interior  of  the 
spinal  canal. 

Internal  Carotid  Artery. — After  furnishing  a  large  meningeal  artery,  this  vessel  enters 
the  cranium  by  the  foramen  lacerum  basis  cranii,  and  there  divides  to  form  a  rete  mirabile,  analo- 
gous to  that  of  Ruminants,  and  of  which  a  description  will  be  given  hereafter.  The  cerebral 
arteries  arising  from  this  r^seau  differ  but  little  from  those  of  Solipeds ;  these  are  the  posterior 
cerebral  arteries,  which  give  rise  to  the  basilar  artery  and  originate  the  middle  spinal  artery. 

External  Carotid  Artery.— This  artery  is  seen  to  pass  between  tjje  pterygoid  muscles  and 
the  branch  of  the  maxilla,  in  describing  several  inflections,  and  arrives  in  the  maxillary  hiatus, 
without  exhibiting  in  its  course  any  sensible  distinction  between  the  external  carotid,  properly 
called,  and  its  continuation,  the  internal  maxillary  artery. 

Among  the  branches  it  supplies,  we  notice : 

1.  The  lingual  artery,  more  voluminous,  perhaps,  than  in  the  other  animals. 

2.  A  branch  analogous,  in  its  origin  at  least,  to  the  glosso-facial  artery  of  the  Horse,  and 
•which  distributes  its  ramuscules  in  the  submaxillary  space,  and  particularly  to  the  salivary 
and  lymphatic  glands. 

3.  The  posterior  auricular  artery,  noticeable  for  its  great  length  and  considerable  volume. 

4.  The  transverse  artery  of  the  face  and  the  anterior  auricular  artery,  arising  separately 
beside  each  other,  and  extremely  slender. 

5.  Several  deep  temporal  and  masseteric  arteries. 

6.  Pterygoid  branches. 

7.  An  enormous  buccal  branch. 

8.  The  ophthalmic  artery,  concurring  to  form  the  rete  mirahile. 

9.  A  small  orbital  branch,  coming  from  the  superior  dental  artery  in  Solipeds  and  Carnivora. 

10.  The  nasal,  palatine,  and  superior  dental  arteries. 

3.  Carotid  Arteries  of  Ruminants. 

A.  In  the  Sheep,  which  will  serve  as  a  type  for  this  description,  the  carotid  arteries  arise 
by  a  common  trunk  from  the  right  axillary  artery,  as  in  Solipeds.  Arriving  in  the  cephalic 
region,  towards  the  upper  part  of  the  neck,  they  furnish  a  thyroid  and  a  laryngeal  branch,  then 
give  off  a  very  slender  occipital  artery,  and  are  continued  from  this  point  by  the  external 
carotid. 

The  internal  carotid,  properly  called,  is  absent,  and  we  shall  see  immediately  how  it  is  com- 
pensated for. 

Occipital  Artery.— Having  given  some  ramuscules  to  the  anterior  straight  muscles  of  the 


OT8  THE  ARTERIES. 

head,  and  a  small  meningeal  branch  whicli  enters  the  cranium  by  the  foramen  lacerum  basis 
cranii,  this  vessel  passes  into  the  condyloid  furamen,  which  also  affords  a  passage  to  the  hypo- 
glossal nerve,  places  itself  beneath  the  dura  mater,  and  is  inflected  backward  to  open  into  the 
anterior  extremity  of  the  collateral  artery  of  the  spine,  at  the  superior  foramen  of  the  atlas. 
The  branch  resulting  from  this  junction  emerges  by  that  foramen,  to  be  distributed  in  the 
muscles  of  the  neck,  where  its  divisions  resemble  those  of  the  occipito-muscular  and  atloido- 
muscular  branches  in  the  Horse. 

In  traversing  the  condyloid  foramen,  the  occipital  artery  sends  into  the  parieto-temporal 
canal,  by  a  peculiar  bony  conduit  (see  p.  50),  a  very  small  filament  which  is  distributed  to 
the  dura  mater,  in  anastomosing  with  a  branch  of  the  posterior  auricular. 

It  communicates,  after  its  entrance  into  the  cranial  cavity,  with  the  rete  mirabile. 

External  Carotid  Artery. — Terminated,  as  in  the  Horse,  by  the  superficial  temporal  and 
internal  maxillary  arteries,  this  vessel  sends  off  on  its  course  : 

1.  A  pharyngeal  artery,  the  origin  of  which  is  nearly  confounded  with  that  of  the  occipital 
artery. 

2.  The  lingual  artery,   furnishing  a  collateral  branch  which  exactly  represents  the  sub- 

Fig.  382. 


THE    RETE    MIRABILE    OF    THE    SHEEP,    SEEN    IN    PROFILE. 

1,  Carotid  artery ;  2,  occipital  artery;  3,  lingual  artery,  4,  maxillo-muscular  artery;  5,  posterior 
auricular  artery ;  6,  superficial  temporal  artery;  7,  anterior  auricular  artery  ;  8,  middle  temporal 
artery;  9,  transverse  artery  of  the  face;  10,  internal  maxillary  artery;  11,  inferior  dental 
artery;  12,  spheno-spinous  artery  ;  13,  deep  posterior  temporal  artery  ;  14,  deep  anterior  temporal 
artery;  15,  commencement  of  the  originating  arteries  of  the  rete  mirabile;  16,  encephalic  rete 
mirabile;  17,  trunk  of  the  encephalic  arteries  arising  from  the  rete  mirabile;  18,  ophthalmic 
artery ;  19,  ophthalmic  rete  mirabile ;  20,  common  origin  of  the  arteries  of  the  eye ;  21, 
supra-orbital  artery;  22,  buccal  artery;  23,  superior  dental  artery;  24,  orbital  branch  of  the 
latter  ;  25,  palatine  artery ;  26,  nasal  artery. 

mental  of  Man,  and  is  divided  into  two  branches    that  resemble  the  sublingual  and  ranine 
arteries. 

3.  A  large  division  for  the  maxillary  gland. 

4.  The  posterior  auricular  artery,  from  which  proceeds :  1.  The  stylo-mastoid  arteriole, 
which  penetrates  the  aqueduct  of  Fallopius.  2.  Concho-muscular  branches.  3.  A  large 
branch,  resembling  the  mastoid  artery  of  the  Horse.  This  enters  the  temporo-parietal  canal 
by  a  small  foramen  between  the  occipital  and  petrous  portion  of  the  temporal  bone,  and  forms 
two  branches  :  an  external,  emerging  from  this  canal  by  the  wide  orifice  in  the  temporal  fossa, 
and  expending  itself  in  the  temporal  muscle,  after  anastomosing  with  the  two  deep  temporal 
arteries;  smd  an  internal — a  considerable  meningeal  artery — destined  principally  to  the  falx 
cerebri  and  the  tentorium  cerebelli. 


THE  COMMON  CAROTID  ARTERIES.  679 

5.  A  small  maxillo-muscular  artery,  ramifying  eutirely  in  the  internal  pterygoid  and  the 
subcutaneous  muscles. 

Superficial  temporal  artery.— This  vessel  divides,  almost  at  its  origin,  into  three  branches : 

1.  A  posterior,  supplying  the  anterior  arteries  of  the  ear. 

2.  An  anterior,  forming  the  transverse  facial,  and  terminating  by  the  coronary  or  labial 
arteries,  after  giving  some  ramuscules  to  the  masseter  and  the  muscles  of  the  forehead. 

3.  A  median  artery,  representing  the  middle  temporal  of  Man.  This  vessel  detaches  some 
divisions  to  the  temporal  muscle,  gives  off  the  lachrymal  artery,  as  well  as  a  palpebral  branch 
rising  from  the  same  point,  and  terminates  near  the  base  of  tlie  cranium  by  two  particular 
arteries  that  are  developed  around  the  base  of  the  horn,  and  form  a  real  arterial  circle  from 
which  inferior  and  superior  divisions  are  given  off.  The  latter  are  tlie  most  considerable, 
and  glide  on  the  bony  core  of  the  frontal  appendage,  where  they  are  distributed  almost 
exclusively  to  the  generating  membrane  of  the  horny  tissue,  only  throwing  some  filaments  into 
the  sinuses. 

Internal  maxillary  artery.— It  does  not  traverse  the  subsphenoidal  canal,  as  that  bony 
passage  does  not  exist. 

The  following  are  its  principal  branches : — 

1.  The  inferior  dental  artery,  which  emits  some  pterygoid  ramuscules. 

2.  The  spheno-spinous  artery,  arising  from  the  same  point  as  tlie  preceding,  often  in  common 
with  it,  giving  also  bome  pterygoid  branches,  and  entering  the  cranium  by  the  oval  foramen  to 
aid  in  the  formation  of  the  rete  mirabile,  in  a  way  to  be  indicated  hereafter. 

3.  The  po»terior  deep  temporal  artery,  which  detaches  a  masseteric  artery. 

4.  The  interior  deep  temporal  artery. 

5.  The  buccal,  principally  sent  to  the  masseter  muscle. 

6.  The  ophthalmic  artery,  longer  than  in  the  other  animals,  forming  a  loop  before  traversing 
the  orbital  foramen,  and  giving  a  supra-orbital  branch  and  a  fasciculus  of  muscular  and  ciliary 
arteries.  Near  the  point  where  the  originating  trunk  of  this  fasiculus  is  detached,  the  ophthalmio 
artery  shows  on  its  course  a  very  curious  arrangement  which  lias  not  yet  been  noticed  ;  we 
believe  this  is  a  veritable  arterial  plexus,  in  a  ganglionic  form,  in  principle  exactly  disposed  as 
that  about  to  be  described  (Fig.  382,  19). 

7.  The  originating  arteries  of  the  rete  mirabile,  usually  consisting  of  two  principal  vessels, 
arising  with  the  ophthalmic,  passing  backward  through  the  supra-sphenoidal  canal,  and  rami- 
fying in  a  special  manner  to  form  a  mass  of  reticular  twigs,  designated  the  rete  mirabile 
(Fig.  382,  16). 

This  network  is  a  small  ovoid  mass,  elongated  from  before  to  behind,  placed  beneath  the 
dura  mater,  on  the  side  of  the  sella  Turcica,  within  the  superior  maxillary  nerve,  and  composed 
of  a  multitude  of  fine  arterial  divisions  which  anastomose  with  each  other  in  an  extremely 
complicated  manner.  Its  inferior  extremity,  passing  into  the  supra-sphenoidal  canal,  receives 
the  generating  arteries.  The  posterior  extremity,  covered  by  the  clinoid  process,  is  in  com- 
munication with  the  spheno-spinous  artery,  which  there  expends  itself.  Towards  its  middle 
part,  and  above,  the  twigs  forming  it  reconstitute  themselves  into  a  single  trunk  analogous 
to  the  intercranial  portion  of  the  internal  carotid  of  Solipeds  (Fig.  382, 17),  and  which  traverses 
the  dura  mater,  dividing  into  three  branches.  These  are  the  anterior,  middle,  and  posterior 
cerebral  arteries ;  the  latter  anastomoses,  by  convergence,  with  the  homologous  artery  of  the 
opposite  side,  behind  the  pituitary  gland,  to  form  the  basilar  artery  and  the  middle  spinal  artery, 
■which  continues  it. 

This  singular  disposition  of  the  arteries  of  the  encephalon  well  deserves  the  name  of  rete 
mirabile  (wonderful  network),  by  which  it  is  known.  If  we  were  desirous  of  giving  a  summary 
idea  of  this  network,  we  might  compare  it  to  a  lymphatic  gland,  the  efferent  vessels  of  which 
would  be  represented  by  the  originating  arteries  with  the  spheno-spinous,  and  the  efferents  by 
the  originating  trunk  of  the  encephalic  arteries. 

8.  Next  comes  the  superior  dental,  the  orbital  branch  of  which  presents  a  considerable 
volume,  and  terminates  on  the  anterior  surface  of  the  head  by  long  superficial  divisions. 
Some  of  these — the  ascending — anastomose  with  the  inferior  branches  of  the  arterial  circle 
situated  amund  the  base  of  the  horn ;  while  others,  the  descending,  communicate  with  the 
infra-orbital  branch  of  the  same  vessel,  and  with  the  superior  coronary  artery. 

9.  The  last  to  be  given  off  are  the  nasal  and  palatine  arteries,  which  terminate  the  internal 
maxillary:  the  nasal  artery  is  disposed  as  in  the  Horse;  the  palatine  goes  entirely  to  the 
palate. 

B.  In  the  Ox,  we  find  all  the  peculiarities  just  enumerated,  except  with  the  following 
differences : — 

1.  A  little  above  the  origin  of  the  lingual  artery,  the  external  carotid  gives  rise  to  ao 


THE  ARTERIES. 


Fig.  383. 


external  maxillary  artery,  which  turns  round  the  inferior  border  of  the  maxilla,  in  company 
with  its  satellite  vein,  and  terminates  on  the  forehead,  as  in  the  Horse,  after  supplying  the 
coronary  arteries. 

2.  The  maxillo -muscular  artery  is  distributed  to  the  two  masseters — to  the  external,  as  well 
as  the  internal. 

3.  The  transverse  artery  of  the  face  does  not  form  the  coronary  arteries,  as  these  come  from 
the  external  maxillary  ;  it  is  altogether  expended  in  the  masseter  muscle. 

4.  The  anterior  auricular  artery  sends  an  enormous  branch  into  the  temporo-parietal  canal, 
by  the  orifice  situated  behind  the  supra-condyloid  process. 

5.  The  ophthalmic  artery  and  the  generating  arteries  of  the  rete  mirabile  proceed  from  a 
common  trunk. 

6.  The  rete  itself  shows  some  diflferences.     We  do  not  find,  as  in  the  Sheep,  two  lateral 
elongated  lobes,  almost  independent  of  each  other,  but  a  circular  mass  surrounding  the  sella 

Turcica.  Besides,  the  occipital  arteries  concur  in  its 
formation,  and  pass  into  its  posterior  part  (Fig.  383). 

(This  rete  mirabile  of  Galen  would  appear  to  be 
formed  on  the  carotid  and  vertebral  arteries  of  animals, 
which,  in  a  state  of  nature,  feed  from  the  ground;  the 
object  being  to  furnish  an  equable  and  prolonged  supply 
of  blood  without  tiie  risk  of  check  or  hindrance,  and 
thus  to  obviate  the  tendency  to  congestion  of  tlie  brain 
during  the  dependent  position  of  the  head.  This 
minute  subdivision  and  subsequent  reconstitution  of 
an  artery,  with  a  like  intention,  is  also  observed  in 
other  creatures  besides  grazing  animals.  The  vessels 
in  the  arm  of  the  sloth  are  so  disposed  that  the  animal 
can  remain  suspended  by  it  for  long  periods;  and  a 
similar  arrangement  is  noted  in  the  legs  of  birds — such 
as  the  Swan,  Goose,  etc.,  which  stand  for  a  long  time. 
Around  the  Horse's  foot  the  arteries  break  up  into 
numerous  divisions,  and  we  know  that  this  animal  can 
remain  in  a  standinir  attitmle  for  months,  and  even 
years.  The  rete  ophthahnicum  of  birds  is  arranged  like 
the  rete  mirabile.  The  same  object  is  sometimes 
attained  by  great  tortuosity,  as  we  have  already  seen 
in  the  description  of  several  of  the  arteries.  Perhaps 
the  most  marked  example,  however,  is  to  be  found  in 
the  carotid  artery  of  the  Seal,  which  is  nearly  forty 
times  longer  than  the  space  it  has  to  traverse. 

But  it  may  be  remarked  that  there  is  no  rete  mira- 
bile in  the  Horse— though  it  is  also  a  grazing  animal 
— at  all  to  be  compared  with  that  of  Ruminants,  the 
circle  of  Willis  being  its  only  representative.) 


THE   RETE   MIRABILE   OF   THE   OX 
(POSTERIOR    face). 

1,  Rete  mirabile;  2,  trunk  of  the 
originating  arteries  of  the  rete  mi- 
rabile; 3,  .spheno-spinous  artery;  4, 
trunk  of  the  encephalic,  or  internal 
carotid  arteries ;  5,  branches  of  the 
occipital  passing  to  the  rete  mira- 
bile;  6,  interspinal  arterial  canal, 
formed  by  the  intervertebral  spinal 
branches. 


Comparison  of  the  Carotid  Arteries  of  Man 
with  those  of  animals. 


The  common  carotids  of  Man  have  a  different  origin, 

the  right  arising  from  the  arteria  innominata,  the  left 

from  the  arch  of  the  aorta.   At  the  inferior  border  of  the 

thyroid  cartilage,  they  terminate  by  only  two  branches — the  external  and  internal  carotids ;  the 

occipital  artery  is  but  a  division  of  the  former. 

Internal  Carotid  Artery. — Contrary  to  what  is  observed  in  animals,  the  internal 
carotid  is  a  little  larger  than  the  external,  a  difference  which  is  explained  in  Man  by  the 
predominance  of  the  cranium  over  the  face.  This  vessel  describes  a  flexuous  course  until  it 
reaches  the  carotid  foramen  in  the  petrous  bone ;  it  forms  two  curves  in  the  cavernous  sinus, 
penetrates  the  dura  mater,  and  divides  at  the  fissure  of  Sylvius  into  four  branches,  which  are, 
as  in  Solipeds:  the  posterior  communicating,  anterior  cerebral,  middle  cerebral,  and  artery  of 
the  choroid  'plexus.  The  internal  carotid  has  an  important  collateral  branch— the  ophthalmic 
artery — that  arises  from  the  convexity  of  the  curve  the  carotid  makes  inside  the  anterior  clinoid 
process,  at  the  bottom  of  the  orbit.  If  it  differs  at  its  origin,  yet  this  vessel  has  a  distribution 
analogous  to  that  already  described. 


TEE  COMMON  CAROTID  ARTERIES.  681 

External  Carotid  Artery. — In  its  origin,  course,  and  termination,  the  external  carotid 
comports  itself  as  in  animals.     It  gives  rise  to  six  branches  : 

1.  The  superior  thyroid,  resembling  in  its  distribution  the  thyro-laryngeal  of  Solipeds. 

2.  The  lingual  artery,  which  furnishes  a  sublingual,  and  takes  the  name  of  ranine  at  its 
termination. 

3.  The  facial  artery,  which  gives  off  the  palatina  ascendens,  analogous  to  our  pharyngeal, 
and  the  submental. 

The  two  last-mentioned  arteries  arise  separately ;  consequently,  there  is  not  a  glosso-facial 
in  Man  as  we  have  seen  it  in  the  Horse. 

4.  The  posterior  auricular  artery. 

5.  The  inferior  pharyngeal  artery. 

6.  The  occipital. — This  vessel  represents  the  occipital  of  the  Horse  minm  its  cerebro-spinal 


ARTERIES  OF  THE  FACE  AND  HEAD  OF  MAN. 

1,  Common  carotid;  2,  internal  carotid;  3,  external  carotid;  4,  4,  occipital  artery  5  superior 
thyroid  artery  ;  6,  trapezius  ;  7,  lingual  artery  ;  8,  sterno-mastoid ;  9,  facial  artery  ;  10,  temporal 
artery,  dividing  into  anterior  and  posterior  branches;  11,  submental  branch;  12,  transverse 
facial  artery;  13,  inferior  labial  branch  ;  15,  inferior  coronary,  and,  17, superior  coronary  branch; 
19,  lateral  nasal  branch  ;  21,  angular  branch. 


branch.  It  gives  off  a  mastoid  artery,  and  terminates  in  the  muscles  of  the  neck  and  on  the 
posterior  aspect  of  the  cranium.  The  cerebro-spinal  branch  is  replaced  by  the  termination  of 
the  vertebral  artery,  which  forms  on  the  inferior  face  of  the  medulla  oblongata  the  basilar 
artery,  the  disposition  of  which  is  identical  with  that  already  described. 

The  superficial  temporal  artery,  and  the  internal  maxillary  artery,  constitute  the  termination 
of  the  external  carotid. 

The  internal  maxillary  is  directed  towards  the  spheno-palatine  or  nasal  foramen,  into 
which  it   passes  and  terminates   by  the   spheno-spinous  artery.    It  does  not  give  off  the 


682  THE  VEINS. 

ophthalmic  artery,  that  vessel  coming  from  the  internal  carotid ;  but  it  furnishes  all  the  other 
branches  we  have  studied  in  animals.  There  are,  therefore:  a  tympanic  artery;  a  meningeal, 
middle,  or  spheno-spinous ;  an  anterior  and  posterior  deep  temporal ;  an  inferior  dental ;  a 
buccal;  a  masseteric;  pterygoideans ;  and  a  descending  palatine  or  palato-labial  artery. 


THIRD    SECTION. 
THE   VEINS. 

CHAPTER   I. 

GENERAL    CONSIDERATIONS. 

Definition. — The  veins  are  the  centripetal  vessels  of  the  circulatory  system. 
They  bring  back  to  the  heart  the  blood  which  has  been  carried  from  that  viscus 
to  the  organs. 

Division. — Some  proceed  from  the  lungs,  carrying  red  blood,  and  converge 
towards  the  left  auricle  of  the  heart  :  these  are  the  pulmonary  veins,  or  veins  of 
the  lesser  circulation.  Others  emerge  from  the  mass  of  all  the  organs,  transport 
the  dark  blood,  and  open  into  the  right  auricle  :  these  are  the  veins  of  the 
general  circulation. 

There  are,  therefore,  two  venous  systems  commencing  by  a  capillary  network, 
opposite  an  arterial  network.  Sometimes  a  third  system  of  veins  has  been 
described  for  the  intestines ;  indeed,  the  vena  portse  offers  a  certain  indepen- 
dence in  the  midst  of  the  veins  of  the  general  circulation,  as  it  terminates  in  a 
capillary  plexus  in  the  interior  of  the  liver,  and  by  this  plexus  it  communicates 
with  the  posterior  vena  cava. 

General  Disposition. — The  veins,  after  succeeding  the  capillary  networks 
which  terminate  the  arteries,  or  the  spaces  in  the  erectile  tissues,  form  a  series  of 
convergent  ramifications  which  repeat,  in  a  general  manner — but  in  an  inverse 
gense— the  arterial  ramifications,  the  course  of  which  they  for  the  most  part  follow. 
A  certain  number,  nevertheless,  are  placed  at  some  distance  from  the  arterial 
trunks,  beneath  the  external  tegumentary  membrane,  where  they  are  disposed  in 
a  vast  network  that  constitutes  the  superficictl  veins  of  the  body.  Apart  from 
this  peculiarity,  we  have  nothing  more  to  say  with  regard  to  the  situation, 
direction,  relations,  and  anastomoses  of  the  veins  than  has  been  already  made 
known  in  studying  the  arteries.  It  is  only  to  be  remarked,  that  the  anastomoses 
of  the  venous  system  are  more  numerous,  larger,  and  more  complex  than  those 
of  the  arterial  system ;  that  they  also  communicate  with  more  voluminous 
trunks  ;  and  that  they  very  often  join  the  deep  to  the  superficial  veins.  At 
certain  points— external  genital  organs,  bladder,  rectum— the  anastomoses  are  so 
numerous  as  to  constitute  veritable  venous  plexuses.  These  are  more  especially 
met  with  in  regions  where  the  circulation  is  liable  to  be  more  or  less  hindered, 
either  from  the  displacement  of  organs  or  variations  in  their  volume.  Fenwick 
has  made  known  some  important  communications  with  regard  to  the  mainte- 
nance of  the  circulation ;  for  instance,  those  between  the  subcutaneous  veins, 
the  laro-e   veins   of  the   limbs,  and  the  substance  of  the  thoraco-abdominal 


GENERAL   CONSIDERATIONS.  683 

parieties ;  and  between  the  vena  portse  and  the  deep  epigastric  and  vesical 
veins. 

Form. — "With  regard  to  form,  the  veins  represent  cyhndrical  tubes,  sHghtly 
knotted  on  those  parts  of  their  course  which  correspond  to  their  valves,  but  they 
are  rarely  distended  as  the  arteries  are  ;  the  only  exceptions  are  found  in  the 
venous  polyhedral  spaces  or  sinuses  in  the  dura  mater.  Veins  offer  the  same 
collective  form  as  the  arteries,  the  general  volume  of  the  venous  ramifications 
being  as  much  more  developed  as  they  are  distant  from  the  heart,  so  that  all  the 
branches  collected  at  last  into  an  imaginary  single  canal  would  form  a  hollow 
cone,  the  apex  of  which  would  correspond  to  the  auricles. 

Number  and  Capacity. — In  comparing  the  two  orders  of  vessels  with 
reference  to  their  number  and  capacity,  we  discover  notable  differences.  The 
veins  are  more  numerous  than  the  arteries,  as  a  great  number  of  the  latter  are 
accompanied  by  two  of  the  former,  and  the  subcutaneous  veins  have  no  repre- 
sentatives in  the  arterial  system.  All  the  veins  being,  besides,  much  more 
voluminous  than  the  corresponding  arteries,  it  follows  that  the  total  capacity 
of  the  venous  system  much  surpasses  that  of  the  arterial  system,  and  that  we  may 
consider  the  relation  of  two  to  one  as  being  the  approximate  expression  of  this 
difference. 

When  the  veins  are  compared  with  the  arteries,  it  is  remarked  that  the 
relations  between  the  length  of  the  trunks  and  branches  are  reversed.  In 
the  arteries,  the  trunks  are  large  and  the  branches  short ;  in  the  veins,  on  the 
contrary,  the  branches  are  relatively  much  longer  than  the  trunks.  This  dis- 
position favours  the  flow  of  the  blood  in  the  veins,  at  the  commencement  of 
which  we  do  not  find,  as  in  the  arteries,  a  propelling  organ. 

Another  arrangement  to  answer  the  same  end,  in  opposing  the  influence  that 
atmospheric  pressure  might  have  on  the  veins,  is  the  attachment  of  these  vessels 
to  the  walls  of  the  cavities  they  pass  through  ;  this  is  observed,  for  instance,  at 
the  entrance  to  the  thorax. 

This  disposition,  so  favourable  to  the  circulation  of  the  blood,  becomes  a 
constant  source  of  danger  to  the  surgeon,  by  its  permitting  the  introduction  of 
air  into  the  circulatory  system — especially  during  inspiration — when  a  vein  is 
opened. 

Internal  Conformation. — The  interior  of  the  veins  is  remarkable  for  the 
presence  of  valvular  folds,  the  arrangement  of  which  resembles,  in  principle,  that 
of  the  sigmoid  valves  of  the  heart.  These  valves  offer :  an  adherent  border 
attached  to  the  walls  of  the  vessel ;  a  free,  semilunar  border  ;  a  concave  surface 
towards  the  heart  when  the  valves  are  tense ;  and  a  convex  surface  which,  on 
the  contrary,  looks  towards  the  roots  of  the  veins. 

These  valves  are  most  frequently  single,  but  they  are  sometimes  joined  in 
twos  or  threes  ;  according  to  some  authorities,  there  are  even  found  four  or  five 
together,  arranged  in  a  circular  manner.  They  are  distinguished  as  parietal  and 
ostial  valves,  the  latter  being  placed  at  the  entrance  of  one  vein  into  another. 
All  the  veins  are  not  provided  with  them,  however,  and  where  they  exist  they 
may  be  more  or  less  numerous.  They  are  absent  in  the  pulmonary  system,  and 
in  the  trunks  of  the  venaB  cava  ;  absent  or  quite  rudimentary  throughout  the 
extent  of  the  vena  portae  ;  rare  and  sUghtly  developed  in  the  vena  azygos,  the 
veins  of  the  testicle,  uterus,  and  ovary ;  and  very  numerous,  very  large,  and 
very  complete  in  the  veins  of  the  limbs. 

The  function  of  these  valves  is  to  favour  the  onward  course  of  the  blood, 


681  THE   VEINS. 

and  to  oppose  its  reflux  from  the  heart  towards  the  organs.  Applied,  as  they 
are,  to  the  walls  of  the  veins  by  their  coucave  face  during  the  regular  and 
normal  circulation,  they  are  disposed  as  a  transverse  valve  to  sustain  the  column 
of  blood  when  any  strain  or  pressure  gives  that  column  a  retrograde  movement. 

Structure. — The  walls  of  the  veins  are  thin,  semi-transparent,  and  elastic, 
and  collapse  when  the  vessels  are  empty.  Compared  with  the  arteries,  they  have 
only  two  distinct  tunics. 

The  internal  tunic  is  composed  of  an  endothelial  layer  of  irregular  and  poly- 
gonal cells,  lying  on  a  layer  of  connective  tissue,  limited  by  an  elastic  layer 
— analogous  to  the  internal  elastic  layers  of  arteries. 

The  external  tunic  is  composed  of  connective  tissue,  elastic  fibres,  and 
smooth  muscular  fibres — the  first  predominating. 

The  muscular  fibres  are  transversal,  longitudinal,  or  oblique,  their  aiTange- 
ment  varying  with  the  vessels.  Lorge  states  that  the  vena  porta?  and  intra- 
lobular veins  in  the  Horse  have  only  longitudinal  muscular  fibres. 

In  some  veins  or  portions  of  a  vein  they  may  be  absent.  In  the  veins  of 
the  bones,  and  in  the  sinuses  of  the  dura  mater,  the  walls  are  reduced  to  a  layer 
of  endothelium  laid  on  a  layer  of  connective  tissue. 

The  venules  differ  from  the  arterioles  in  the  dissemination  of  their  muscular 
fibres,  which  form  a  continuous  layer  in  the  latter. 

The  veins  have  very  numerous  vasa  vasorum,  which  form  a  complete  net- 
work around  them.  The  vena  portae  alone  is  accompanied  by  nerve  filaments 
from  the  great  sympathetic. 

(As  remarked,  the  superficial  veins  are  generally  unaccompanied  by  arteries  ; 
they  usually  pass  between  layers  of  superficial  fascia,  and  at  the  most  convenient 
situations — generally  those  best  protected — pass  through  the  underlying  fascia 
to  terminate  in  the  deep  veins.  These  are  most  frequently  accompanied  by 
arteries,  being  often  enclosed  in  the  same  sheath  with  them,  particularly  in  the 
extremities.  With  a  large  number  of  arteries  there  are  two  veins,  one  on  each 
side,  the  venm  comifes,  though  the  largest  arteries  have  only  one  venous  trunk. 
The  large  and  frequently  repeated  communications  are  undoubtedly  intended  to 
compensate  for  the  thinness  of  their  parietes,  which  expose  to  obstruction  and 
dilatation  ;  this  they  cannot  overcome,  because  of  the  slowness  with  which  the 
blood  passes  through  them.  The  valves  are  accessory  to  these  inosculations  ; 
upon  the  cardiac  face  of  each  valve  the  vein  is  expanded  into  two  sinuses,  which 
correspond  to  the  extent  of  the  valve  ;  these  pouches  give  the  distended  vessel 
its  nodulated  appearance.  Remak  found  longitudinal  muscular  fibres  in  the 
adventitia  of  the  large  veins  of  the  Ox  and  Sheep,  but  chiefly  in  the  hepatic 
portion  of  the  posterior  vena  cava  and  the  veins  of  the  liver. 

It  is  also  stated  that  these  longitudinal  fibres  are  found  in  the  inner  part  of 
the  middle  coat — for  some  authorities  still  describe  three  tunics— of  some  veins 
— ihac,  femoral,  umbilical ;  and  the  veins  of  the  pia  mater,  brain,  and  spinal 
cord,  retina,  and  placenta,  as  well  as  those  of  the  bones  and  dura  mater  sinuses, 
have  no  muscular  tissue  at  all.  Valves  are  absent  in  the  veins  of  the  viscera, 
of  the  cranium  and  vertebral  canal,  and  umbilical  vein,  in  addition  to  the  precited 
vessels.  The  endothelial  cells  on  the  side  of  the  valves  over  which  the  blood 
passes,  are  more  elongated  than  on  the  cardiac  side  of  the  valves,  where  the 
long  axes  of  the  cells  are  placed  transversely — an  arrangement  which  diminishes 
friction.) 


THE  CARDIAC  OR  CORONARY   VEINS.  685 

Injection  of  the  Veins. — To  render  the  dissection  and  study  of  the  veins  more  easy,  they 
ought  to  be  filled  with  tallow  or  any  other  solidifiable  matter,  like  the  arteries.  But  to  attain 
this  result  the  same  mode  of  procedure  cannot  be  employed  as  for  them.  Instead  of  causing 
the  injecting  material  to  flow  from  the  trunk  into  the  branches,  it  is  necessary  to  propel  it 
from  the  branches  towards  the  trunk,  because  of  the  presence  of  the  valves ;  this  is  to  be  done 
by  successively  fixing  the  cannula  into  several  venous  brandies. 

Four  injections  generally  sufiice  to  fill  the  whole  venous  system  in  a  satisfactory  manner. 
The  first  is  made  from  the  alveolar  vein,  beneath  the  masseter  muscle;  the  second  from  a 
digital  vein  of  one  or  both  anterior  limbs,  or  from  tlie  side  of  the  foot,  after  having  destroyed 
by  a  stylet  the  few  valves  which  are  sometimes  found  towards  the  point  of  union  in  this  vein; 
or  from  the  side  of  the  heart.  The  third,  from  the  posterior  digital  veins,  in  the  same  way ; 
the  fourth,  by  an  intestinal  vein.  If  any  important  veins  are  empty  after  these  four  injectiona — 
a  case  of  frequent  occurrence — they  can  be  directly  injected. 


CHAPTER  II. 

Veins  of  the  Lesser  Circulation,  or  Pulmonary  Veins  (Fig.  349,/). 

The  pulmonary  veins  comport  themselves  in  a  similar  manner  to  the  correspond- 
ing arteries.  They  are  lodged  in  the  substance  of  the  lung,  and  collect  in  from 
four  to  eight  trunks,  which  open  into  the  roof  of  the  left  auricle,  after  emerging 
from  the  pulmonary  organ  immediately  above  the  origin  of  the  bronchi.  As 
they  are  destitute  of  valves,  they  readily  allow  the  blood  to  flow  towards  their 
roots.  It  is  they  which  carry  to  the  left  heart  the  blood  thrown  into  the  lungs 
by  the  right  ventricle,  to  be  submitted  to  the  revivifying  action  of  the 
atmosphere. 


CHAPTER  III. 

Veins  of  the  General  or  Systemic  Circulation. 

These  vessels  bring  to  the  right  auricle  the  blood  which  has  been  dispersed  in 
the  texture  of  organs,  by  the  ramifications  of  the  great  arterial  tree. 

They  open  into  the  auricle  by  forming  three  groups — the  coronary  or  cardiac 
veins,  the  anterior  vena  cava,  and  the  posterior  vena  cava. 

The  diaphragm  establishes  the  exact  limit  between  the  domains  of  the 
anterior  and  posterior  vena  cava. 

Aeticle  I. — Caediac  oe  Coeonaey  Veins. 

There  are  several  small,  and  one  large  or  great  coronary  vein. 

Small  Cardiac  Veins. — These  are  the  almost  insignificant  vessels,  un- 
determined in  number,  which  come  from  the  walls  of  the  right  ventricle  and 
open  directly  into  the  corresponding  auricle  at  the  coronary  groove.  (Among 
these  may  be  included  the  debatable  ve^ice  Thehesii — a  multitude  of  minute 
venules  said  to  arise  in  the  structure  of  the  heart,  and  open  directly  into  its 
cavities.) 

,    Great  Coronary  Vein  (Figs.  349,  5  ;  350,  o,  p). — This  vein  is  formed 
by  two  roots  :  one  is  lodged  in  the  right  ventricular  groove,  and  accompanies 
the  cardiac  artery  of  the  sajne  side  ;  the  other  follows,  at  first,  the  left  ventricular 
46 


686  THE   VEINS. 

groove,  ascends  nearly  to  the  pulmonary  artery^  and  is  then  inflected  backwards 
by  placing  itself  in  the  coronary  groove,  along  with  the  horizontal  branch  of  the 
left  cardiac  artery.  Turning  round  the  base  of  the  posterior  ventricle,  it  joins 
the  right  root,  near  the  upper  extremity  of  its  groove.  The  common  trunk 
resulting  from  this  junction,  after  a  short  course  opens  into  the  right  auricle, 
below  and  within  the  entrance  of  the  posterior  vena  cava. 

In  their  course,  the  two  branches  of  the  coronary  vein  receive  branches  from 
the  auricular  and  ventricular  walls. 

The  bronchial  veins,  ramifying  on  the  bronchi  Uke  the  arteries,  the  satellites 
of  which  they  are,  also  open  into  the  great  coronary  vein,  very  near  its  entrance, 
after  becoming  a  single  vessel,  which  sometimes  passes  directly  into  the  auricular 
cavity. 

Article  II.— Anterior  Yena  Cava  (Figs.  349,  r  ;  350,  d ;  389). 

This  is  a  voluminous  trunk,  which  ought  to  be  considered  as  the  correspond- 
ing vein  of  the  anterior  aorta.  It  extends  from  the  entrance  of  the  chest  to 
the  right  auricle,  into  the  roof  of  which  it  is  inserted.  It  is  comprised  between 
the  two  layers  of  the  anterior  mediastinum,  and  lies  below  the  trachea,  to  the 
right  of  the  anterior  aorta. 

Four  large  vessels — the  ftao  jugular  and  tico  axillary  veins — opening  in 
common  in  the  space  comprised  between  the  two  first  ribs,  constitute  the  roots 
of  this  vessel. 

Collateral  Affluents. — The  affluent  vessels  which  the  anterior  vena  cava 
receives  in  its  course  are  :  the  internal  thoracic,  vertebral,  superior  cervical,  and 
dorsal  veins,  and  the  great  vena  azygos. 

Internal  Thoracic  or  Internal  Mammary  Vein. — A  satellite  of  the 
artery  of  the  same  name,  this  vein  opens  into  the  anterior  vena  cava,  at  its 
origin  (Fig.  389). 

Vertebral  Vein. — It  accompanies  the  corresponding  artery  in  the  canal 
formed  by  the  foramina  in  the  transverse  processes  of  the  cervical  vertebra,  and 
joins  the  vena  cava  at  the  origin  of  that  artery  (Fig.  389). 

Superior  Cervical  Vein. — Exactly  resembles  the  artery  the  name  of  which 
it  bears. 

Dorsal  Vein. — This  vessel  follows  the  dorso-muscular  artery,  and,  like  it, 
presents  a  subcostal  branch.  On  the  left  side,  this  branch  is  designated  the 
small  vena  azygos,  and  is  often  prolonged  to  the  eleventh  or  twelfth  rib  ;  it 
receives  the  intercostal  veins  of  the  spaces  it  crosses. 

It  may  be  remarked  that  the  vertebral,  superior  cervical,  and  dorsal  veins 
of  the  right  side,  are  nearly  always  thrown  separately  into  the  vena  cava,  while 
on  the  left  side  they  constantly  unite  to  form  a  single  trunk  (Figs.  349,  w  ;  389). 

Great  Vena  Azygos  (Figs.  349,  x  ;  350,  e ;  389).— This  is  a  long  single 
vein,  which  commences  at  the  first  lumbar  vertebra,  and  extends  forward  on 
the  right  of  the  anterior  aorta,  beneath  the  bodies  of  the  dorsal  vertebrae  to 
about  the  sixth,  when  it  is  inflected  downward  to  terminate  in  the  anterior  vena 
cava,  near  the  entrance  of  that  vessel,  or  even  directly  into  the  right  auricle. 

In  its  course,  the  great  vena  azygos  is  maintained  against  the  bodies  of  the 
dorsal  vertebra  by  means  of  the  parietal  pleura  ;  it  runs  alongside  the  outer 
border  of  the  thoracic  duct,  which  separates  it  from  the  aorta. ^    The  terminal 

'  Sometimes  the  azygos  is  situated  between  the  aorta  and  the  thoracic  duct.  When  the 
latter  lies  to  the  left  side,  it  is  in  direct  contact  with  the  posterior  aorta. 


THE  ANTERIOR    VENA   CAVA.  687 

extremity  of  its  inflection  crosses  the  oesophagus  and  trachea  to  the  right,  and 
is  included  between  these  two  tubes  on  the  one  side,  and  the  right  layer  of  the 
mediastinum  on  the  other. 

Its  roots  are  some  branches  emerging  from  the  spinal  and  psoas  muscles,  and 
which  are  not  usually  in  direct  communication  with  the  posterior  vena  cava,  aa 
in  Man  and  the  other  animals. 

During  its  progress,  it  receives  the  first  lumbar  and  the  satellite  veins  of  all 
the  aortic  intercostal  arteries,  right  and  left.  But  when  the  small  vena  azygoa 
is  prolonged  backwards  beyond  the  posterior  extremity  of  the  subcostal  artery, 
that  vessel,  as  we  have  already  seen,  forms  the  confluent  of  a  certain  number  of 
left  posterior  intercostals. 

Jugular  Veins  (Figs.  386,  389). 

The  jugular  is  a  satellite  vein  of  the  carotid  artery. 

Origin. — It  commences  behind  the  inferior  maxilla,  below  the  articulation 
of  the  jaw,  by  two  large  roots — the  superficial  temporal  vein  and  the  internal 
maxillary  vein,  which  correspond  to  the  two  terminal  branches  of  the  external 
carotid  artery. 

Situation—Direction. — This  vessel  passes  downward  and  backward,  lodged 
at  first  in  the  substance  of  the  parotid  gland,  afterwards  in  the  muscular  inter- 
space designated  the  jugular  furrow,  which  is  comprised  between  the  adjacent 
borders  of  the  mastoido-humerahs  and  sterno-maxillaris  muscles.  Reaching  the 
inferior  extremity  of  the  neck,  it  terminates  in  the  following  manner  : — 

Termination. — On  arriving  near  the  entrance  to  the  chest,  the  two  jugulars 
unite  in  forming  a  vessel  named  the  confluent  of  the  jugulars.  This  confluent, 
into  which  open  the  two  axillary  veins,  is  comprised  between  the  two  first  ribs, 
and  situated  below  the  trachea,  in  the  middle  of  the  prepectoral  lymphatic  glands. 
Fixed  by  fibrous  bands  to  the  neighbouring  parts,  and  particularly  to  the  two 
first  ribs,  the  walls  of  the  jugular  confluent  do  not  collapse  when  the  venous 
system  is  in  a  state  of  vacuity — an  anatomical  peculiarity  which  it  is  necessary 
to  understand,  in  order  to  explain  the  manner  in  which  air  obtains  entrance  into 
the  circulation  when  the  jugular  or  axillary  veins  are  opened,  as  well  as  affording 
an  indication  how  to  prevent  this  serious  accident. 

Relations. — At  its  upper  extremity,  the  jugular  vein  is  surrounded  by  the 
parotideal  tissue.  For  the  remainder  of  its  extent,  it  is  covered  externally  by 
the  cervical  panniculus,  and  by  the  branches  of  the  cervical  plexus  which  creep 
on  the  external  surface  of  that  muscle.  Inwardly,  its  relations  vary  as  we 
consider  its  situations,  above  or  below  :  above,  it  is  related  to  the  subscapulo- 
hyoideus  muscle,  which  separates  it  from  the  common  carotid  and  its  satellite 
nerves  ;  in  its  inferior  moiety,  it  is  in  direct  relation  with  that  vessel,  which  is 
above  it,  as  well  as  with  the  trachea,  and  even,  though  only  on  the  left  side, 
with  the  oesophagus. 

CoLLATEEAL  AFFLUENT  VESSELS.— The  Collateral  veins  which  go  to  the 
jugular  from  its  origin  to  its  termination,  are  :  1.  MaxiUo-muscular  veins.  2. 
Posterior  auricular  vein.  3.  Occipital  vein.  4.  Suhmaxillary  or  facial  vein. 
5.  Thyroid  vein.  6.  Cephalic  vein.  7.  Parotideal  and  innominate  muscular 
branches. 

A.  MaxiUo-muscular  Veins.— Two  in  number,  corresponding  to  the 
branches  of  the  artery  of  the  same  name,  and  entering  the  jugular  close  to  its 
origin,  either  separately  or  after  forming  a  common  trunk. 


688  THE   VEINS. 

B.  Posterior  Auricular  Vein. — A  voluminous  vessel  which  commences 
on  the  concha,  and  descends  on  the  external  face  of  the  parotid  gland,  near  its 
posterior  border,  where  it  is  joined  by  numerous  divisions  from  the  parotid 
lobules.  It  opens  into  the  jugular  vein,  generally  a  little  below,  and  opposite  to, 
the  maxillo-muscular  vessels,  though  it  is  sometimes  lower — often  even  after  the 
occipital  vein  (Fig.  385,  13). 

C.  Occipital  vein. — The  occipital  vein  corresponds,  in  every  respect,  to  its 
fellow-artery.  It  has  two  roots — an  anterior,  which  originates  at  the  posterior 
extremity  of  the  subsphenoidal  confluent  ;  and  a  posterior,  commencing  beneath 
the  transverse  process  of  the  atlas,  and  formed  by  three  principal  branches. 

Among  the  branches  of  the  latter  root,  one  passes  with  the  retrograde  artery 
through  the  posterior  foramen  of  the  atlas,  and  constitutes,  as  it  were,  the  origin 
of  the  vertebral  vein  ;  the  second  communicates  with  the  occipito-atloid  sinuses, 
by  traversing  the  atlas  near  its  middle  ;  the  third — satellite  of  the  cerebro-spinal 
artery — comes  also  from  these  sinuses,  and  receives  the  venules  which  accompany 
the  ramifications  of  the  occipito-muscular  artery. 

D.  Sub-maxillary  or  Facial  Vein. — A  satellite  of  the  artery  of  the  same 
name,  this  vessel  begins  on  the  forehead  by  two  roots — a  superior  and  inferior, 
analogous  in  every  point  to  the  terminal  branches  of  the  artery.  It  descends 
along  the  anterior  border  of  the  masseter  muscle,  gains  the  maxillary  fissure, 
into  which  it  is  inflected,  placing  itseK  between  the  artery  and  Steno's  duct ;  then 
proceeds  backwards  and  downwards  on  the  internal  pterygoid  muscle,  always 
accompanied  by  the  glosso-facial  artery  until  near  the  anterior  extremity  of  the 
maxillary  gland,  when  it  leaves  it  to  follow  the  inferior  border  of  that  gland,  and 
enters  the  jugular  vein,  after  crossing  the  sterno-maxillaris  muscle  outwardly,  and 
forming  with  the  latter  vein  an  angle  which  is  occupied  by  the  inferior  extremity 
of  the  parotid  gland  (Fig.  385). 

Branches  of  origin. — Of  the  two  branches  which,  by  their  union,  constitute  the 
origin  of  the  submaxillary  vein,  the  inferior  {dorsalis  nasi) — a  satellite  of  the 
nasal  branch  of  the  corresponding  artery — possesses  no  interest.  The  superior, 
or  angular  vein  of  the  eye,  merits  particular  notice,  as  venesection  is  sometimes 
practised  on  it.  It  arises  near  the  nasal  angle  of  the  eye,  and  creeps  to  the 
external  face  of  the  elevator  muscle  of  the  upper  lip,  below  the  lachrymalis 
muscle. 

Collateral  branches. — In  its  progress,  the  submaxillary  vein  receives  a  great 
number  of  affluents,  the  principal  of  which  are  the  alveolar  vein,  the  labial  or 
coronary  veins,  the  buccal  vein,  and  the  sablinguaJ  vein. 

a.  Alveolar  vein  (vena  varicosa). — This  is  a  considerable  vessel  lodged  beneath 
the  masseter,  and  lying  against  the  supermaxillary  bone,  between  the  zygomatic 
crest  and  the  aveoli  of  the  upper  molar  teeth  (Fig.  385). 

The  arrangement  of  this  vessel  is  most  singular  ;  its  anterior  extremity  opens 
into  the  submaxillary  vein,  and  its  posterior  extremity  traverses  the  ocular 
sheath,  receives  the  ophthalmic  veins,  and  passes,  with  the  ophthalmic  nerve  of 
the  fifth  pair,  into  the  foramen  lacerum  orbitale,  to  open  into  the  cavernous  sinus 
in  the  interior  of  the  cranium.^ 

Before  traversing  the  ocular  sheath,  and  towards  the  maxillary  hiatus,  this 
vein  receives  the  superior  dental  and  the  confluent  of  the  tiasal  veins — vessels 

'  We  have  also  seen  it  send  into  the  subsphenoidal  canal,  to  the  inner  side  of  the  internal 
maxillary  artery,  a  slender  branch  that  joined  the  anterior  extremity  of  the  subsphenoidal  con- 
fluent.    But  we  cannot  say  that  this  disposition  is  constant. 


THE  ANTERIOR    VENA   CAVA.  689 

which  emerge  from  the  bony  orifices  traversed  by  the  arteries  of  the  same  name 
— that  is,  the  maxillo-dental  canal  and  the  nasal  foramen.  It  also  receives  the 
confluent  of  the  palatine  veins,  which  pass  by  the  palatine  groove,  instead  of 
coursing  along  the  palatine  canal  with  the  corresponding  artery.  In  general, 
these  three  branches  do  not  join  the  alveolar  vein  separately,  but  rather  by  a 
common  trunk. 

The  alveolar  vein  does  not  present  a  uniform  volume.  It  increases  until 
it  reaches  the  alveolar  tuberosity,  where  it  forms  a  kind  of  large  reservoir  ;  but 
in  traversing  the  ocular  sheath  it  suddenly  becomes  constricted,  and  maintains  a 
small  diameter  until  its  entrance  into  the  cavernous  sinus.  (The  reservoir  is 
supposed  to  prevent  congestion  of  the  cavernous  sinus.) 

This  vein  may  be  considered  as  an  affluent  of  the  sinuses  of  the  dura  mater, 
as  well  as  of  the  external  maxillary  vein. 

b.  Labial  or  coronanj  veins. — Satellites  of  the  labial  arteries.  The  superior 
is  often  rudimentary.  The  inferior,  always  voluminous,  is  constituted  by  the 
union  of  several  anastomotic  branches  lying  against  the  external  face  of  the 
mucous  membrane  of  the  cheek. 

c.  Buccal  vein. — Among  the  affluents  of  the  external  maxillary  vein,  we  cite 
this,  because  it  opens  into  the  latter  by  its  anterior  extremity,  opposite  the  inferior 
coronary  vein,  with  which  it  sometimes  communicates  by  a  particular  branch. 
But  the  buccal  vein,  properly  speaking,  constitutes  the  root  of  the  internal 
maxillary,  and  we  will  describe  it  as  such. 

d.  Sublingual  vein. — A  large  vessel,  formed  of  two  branches,  which  arise  in 
the  substance  of  the  tongue,  and  pass  sometimes  separately  into  the  internal 
maxillary  vein.  This  sublingual  vein  passes  through  the  mylo-hyoideus  muscle, 
from  within  to  without,  and  joins  the  principal  vessel  at  the  lymphatic  glands 
lodged  in  the  submaxillary  space. 

E.  Thyroid  Vein. — This  is  a  voluminous  trunk,  resulting  from  the  union 
of  the  venous  divisions  which  accompany  the  laryngeal  and  thyroid  branches 
of  the  thyroid  or  thyro-laryngeal  artery.  It  joins  the  jugular  beside  the  sub- 
maxillary vein,  and  most  frequently  above  it. 

F.  Cephalic  or  Plate  Vein. — A  superficial  vessel,  which  represents  one  of 
the  terminal  branches  of  the  principal  subcutaneous  vein  of  the  forearm.  It  is 
lodged  in  the  interspace  of  the  mastoido-humeralis  and  anterior  superficial 
pectoral  muscles,  and  enters  the  inferior  extremity  of  the  jugular  vein  (Fig.  389). 

G.  Innominate  Veins. — A  certain  number  come  from  the  parotid  gland, 
but  the  principal  arise  in  the  muscles  of  the  neck  and  withers.  One  of  the  latter 
accompanies  the  superior  branch  of  the  cervico  muscular-artery. 

Roots  of  the  Jugular  Vein. 

These  are  constituted  by  the  superficial  temporal  and  internal  maxillary  veins, 
which  are  chiefly  supplied  by  the  sinuses  of  the  cranial  dura  mater. 

1.  Superficial  Temporal  Vein. 

Corresponding  in  the  most  exact  manner  to  the  temporal  vein,  this  vessel  is 
lodged  behind  the  posterior  border  of  the  maxilla,  near  the  articulation  of  the 
jaw,  beneath  the  parotid  gland,  and  is  embedded  in  its  tissue. 

From  the  union  of  these  two  roots,  there  results  : 

1.  The  anterior  auricular  vein — a  very  large,  often  multiple,  and  reticulated 


690  TEE  VEINS. 

branch,  anastomosing  with  the  pterygoid  branches  of  the  internal  maxillary  artery. 
This  vein  issues  from  the  parieto-temporal  conduit,  behind  the  supra-condyloid 
eminence ;  it  receives  one  or  two  branches  which  escape  from  this  conduit  by 
the  foramina  in  the  temporal  fossa,  crosses  the  temporalis  muscle,  and  is  charged 
with  venules  which  arise  in  the  interior  of  that  muscle,  as  well  as  in  the  textures 
of  the  external  ear  (Fig.  385,  8). 

2.  The  subzygomatic  vein,  a  satellite  of  the  homonymous  artery,  and,  like  it, 
is  divided  into  two  branches— one  accompanying  the  transverse  artery  of  the 
face,  the  other  the  masseteric  artery.  The  latter  branch  communicates  by  its 
inferior  extremity  with  the  external  maxillo-muscular  vein  ;  it  joins,  by  its  other 
extremity,  an  enormous  branch  which  comes  from  the  temporal  muscle,  and 
which  passes  into  the  sigmoid  notch,  after  anastomosing  largely  with  the  deep 
temporal  branches  of  the  internal  maxillary  vein  (Fig.  385,  6). 

2.  Internal  Maxillary  Vein. 

Remarkable  for  its  enormous  volume,  this  vein  creeps  between  the  internal 
masseter  muscle  and  the  maxilla,  in  an  oblique  direction  upwards  and  backwards. 
Arriving  within  the  articulation  of  the  jaw,  a  little  below  the  maxillary  condyle 
and  the  external  pterygoid  muscle,  it  joins  the  temporal  vein  after  being  slightly 
inflected  downwards.  It  therefore  runs  its  course  at  a  certain  distance  from  the 
corresponding  artery. 

The  internal  maxillary  has  for  its  radicle  the  hmcal  vein,  which  it  succeeds 
near  the  superior  extremity  of  the  buccinator  muscle. 

Satellite  of  the  artery  and  nerve  of  the  same  name,  this  buccal  vein, 
remarkable  for  its  volume,  is  situated  beneath  the  masseter  muscle,  near  the 
inferior  border  of  the  buccinator  muscle  ;  by  its  anterior  extremity  it  com- 
municates directly  with  the  internal  maxillary  vein,  nearly  opposite  to  the 
junction  of  the  inferior  coronary  vein ;  its  posterior  extremity  is  continued 
directly  with  the  internal  maxillary  vein.  The  collateral  branches  it  receives  in  its 
course,  come  from  the  masseter  muscle  and  the  parietes  of  the  cheek. 

On  its  way  it  receives  a  great  number  of  affluents  ;  these  are  : 

1.  A  large  lingual  vein,  accompanying  the  small  hypoglossal  nerve. 

2.  The  inferior  dental  vein. 

3.  The  trunk  of  the  deep  temporal  veitis — a  large  vessel  situated  in  front  and 
to  the  inside  of  the  temporo-maxillary  articulation,  where  it  communicates  with 
the  masseteric  vein.  This  vessel  arises  in  the  texture  of  the  temporalis  muscle,  but 
particularly  in  the  parieto-temporal  confluent,  with  which  it  joins  through  the 
foramina  in  the  temporal  fossa. 

4.  The  pterygoid  veins,  numerous  branches,  only  a  portion  of  which  come 
from  the  pterygoid  muscles.  The  others,  arising  from  the  subsphenoidal  con- 
fluent of  the  sinuses  of  the  dura  mater,  form,  on  the  superficial  face  of  the 
external  pterygoid  muscle,  a  wide-meshed  network  which  communicates  pos- 
teriorly with  the  temporal  vein,  and  anteriorly  with  the  confluent  of  the  deep 
temporal  veins.  But  as  these  two  vessels  are  bound  together,  outside  the 
temporo-maxillary  articulation,  by  means  of  the  masseteric  artery,  it  results  that 
this  articulation  is  enlaced  on  every  side  by  one  of  the  richest  venous  plexuses  in 
the  whole  body  (Fig  386,  10). 

3.  Sinuses  of  the  Dura  Mater. 
We  will  here  describe  not  only  the  sinuses   of  the  cranial   dura   mater 


THE  ANTERIOR   VENA   CAVA. 


which  supply  the  radicles  of  the  jugular  vein,  but  also  those  of  the  spinal  dura 
mater,  although  these  empty  themselves  into  other  veins  ;  in  order  that  we  may 


Fig.  385. 


RADICLES   AND   COLLATERAL  BRANCHES  OF   THE  JUGULAR  VEIN   IN   THE    HORSE  (EXTERNAL   VIEW). 

M,  Inferior  maxilla ;  A,  buccinator ;  Mo,  superior  molar  gland ;  Ma,  masseter  muscle  (the  greater 
portion  has  been  removed);  R,  elevator  of  the  upper  lip;  S,  Steno's  duct;  C,  carotid  artery;  0, 
subscapulo-hyoideus  muscle ;  St,  sterno-maxillaris  muscle  ;  P,  termination  of  the  two  previous 
muscles.  1,  Radicles  of  the  facial  vein ;  2,  superior  coronary  vein ;  3,  inferior  coronary  vein ; 
4,  4,  4,  facial  vein;  5,  alveolar  vein;  6,  6,  transverse  facial  vein  communicating  in  front  with 
the  facial  vein  ;  7,  buccal  vein  ;  8,  anterior  auricular  vein  ;  9,  masseteric  vein  ;  10,  deep  network 
of  the  masseteric  veins  ;  11,  maxillo-muscular  vein  ;  12,  12,  jugular  vein  ;  13,  posterior  auricular 
vein;  14,  occipital  vein  and  its  various  branches;  15,  laryngeal  vein. 

be  able  to  consider,  in  their  entirety,  all  the  vessels  of  the  nervous  centres  which 
carry  dark  blood. 


692  THE  VEINS. 

The  Sinuses  of  the  Dtjea  Matee  m  General. — These  are  vascular  spaces 
in  the  texture  of  the  dura  mater,  or  situated  between  that  membrane  and  the 
bones  which  form  the  walls  of  the  cerebro-spinal  sheath,  or  are  even  excavated  on 
the  inner  surface  of  these  bones.  These  spaces  differ  more  particularly  from 
the  veins,  by  their  being  generally  of  a  prismatic  form,  by  being  continually  open, 
by  the  absence  of  valves  in  their  interior,  and  by  the  presence,  in  some  of  them,  of 
lamellfe  {traheculce),  or  intersecting  filaments  {chordce  WUlisii)  which  stud  their 
inner  surface,  and  make  them  look  reticulated. 

Their  walls  are  reduced  to  an  epithelial  layer  that  lies  either  on  the  dura 
mater,  or  on  the  osseous  tissue. 

It  is  into  these  sinuses  that  the  veins  of  the  brain  and  spinal  cord  disgorge 
themselves. 

The  Sinuses  of  the  Cranial  Dura  Mater  in  Particular. — Four  prin- 
cipal will  be  described  :  the  superior  longitudinal  sinus  of  the  falx  cerebri,  or 
median  sinus,  the  ttvo  cavernous  or  sphenoidal  sinuses,  and  the  group  of  occipito- 
atloid  sinuses. 

1.  Sinus  of  the  Falx  Cerebri,  Superior  Longitudinal  or  Median 
Sinus. — Channeled  in  the  substance  of  the  falx  cerebri,  and  becoming  wider 
as  it  extends  backwards,  this  sinus  commences  near  the  crista  galli  process,  and 
terminates  on  the  internal  parietal  protuberance  by  bifurcating.  The  two 
branches  resulting  from  this  division  form  the  origin  of  the  parieto-temporal 
confluent,  or  winepress  of  HerophiJus  (torcidar  Herophili,  Fig.  386,  1,  4). 

2.  Cavernous  or  Supra-sphenoidal  Sinuses. — These  are  two  in  number 
— a  right  and  a  left.  They  occupy,  on  the  internal  face  of  the  sphenoid  bone, 
at  each  side  of  the  sella  Turcica,  the  so-called  cavernous  fissures.  Bordered 
outwardly  by  the  superior  maxillary  nerve,  they  receive  at  their  anterior 
extremity  the  insertion  of  the  alveolar  vein.  Posteriorly,  they  join  each  other, 
and  in  doing  so  form  a  kind  of  arch,  open  in  front,  around  the  pituitary  gland 
(Fig.  386,  8).  Each  opens  widely  at  the  foramen  lacerum  basis  cranii,  into  the 
subsphenoidal  confluent. 

3.  Occipital  or  Occipito-atloid  Sinuses. — By  this  name  is  designated  a 
network  of  large  irregular  veins,  situated  beneath  the  external  face  of  the  dura 
mater,  on  the  sides  of  the  occipital  foramen,  and  on  the  entire  internal  surface 
of  the  atloidean  ring.  Anteriorly,  these  venous  reservoirs  communicate,  through 
the  condyloid  foramen,  with  the  posterior  extremity  of  the  subsphenoidal  con- 
fluent. Posteriorly,  they  are  continuous  with  the  spinal  sinuses,  of  which  we 
may  consider  them  to  be  the  origin  (Fig.  386,  6). 

4.  Rudimentary  Sinuses  of  the  Cranial  Dura  Mater. — Independently 
of  the  above-described  reservoirs,  there  exists,  on  the  mner  wall  of  the  cranium, 
some  rudimentary  venous  sinuses  which  should  be  indicated  ;  these  are  :  1.  One 
or  two  veins  lodged  in  the  structure  of  the  tentorimn  cerebelli,  designated  the 
petrosal  or  transverse  sinuses,  communicating,  below,  with  the  cavernous  sinuses, 
and  entering,  above,  into  the  parieto-temporal  confluent.^  2.  Some  small, 
irregular,  and  reticulated  cavities,  very  variable  in  their  disposition,  situated 
beneath  the  dura  mater,  on  the  sides  of  the  cerebellar  cavity,  and  which  generally 
empty  themselves  into  the  subsphenoidal  confluent  by  traversing  the  posterior 
part  of  the  foramen  lacerum  basis  cranii,  and  also  opening  sometimes  into  the 
petrosal    sinus  ;    these    cavities    may  be   regarded    as  the    representatives  of 

•  More  frequently,  perhaps,  these  veins  arise  directly  from  the  substance  of  the  brain,  and 
do  not  communicate,  below,  with  the  cavernous  sinuses. 


THE  ANTERIOR    VENA   CAVA. 


the  lateral  sinuses  in  Man  (Fig.  386,  5).  3.  In  some  instances,  an  inferior  median 
sinus,  channeled  near  the  free  border  of  the  face  of  the  brain,  passes  behind 
into  the  torcular  Herophili  (Fig.  386,  2). 

Fig. 


SINUSES   OF    THE   DURA   MATER   AND   RADICLES   OF   THE    JUGULAR   VEIN   OF   THE   HORSE,    SEEN   IN 
A   MEDIAN   AND   LONGITUDINAL    SECTION   OF   THE   HEAD. 

i.,  Atlas  ;  Ax,  axis  ;  V,  third  cervical  vertebra  ;  C,  nasal  septum  ;  P,  pharynx  ;  E,  Eustachian  tube ; 
M,  interior  maxillary  nerve — coinu  of  the  ns  hyoideus  ;  La,  tongue;  L,  larynx;  T,  trachea;  G, 
submaxillary  salivary  gland;  F,  falx  cerebri.  1,  Sinus  of  ditto;  2,  middle  inferior  sinus;  3, 
venae  Galeni ;  4,  torcular  Herophili;  5,  small  sinuses  of  the  cerebellar  cavity ;  6,  occipito-atloidean 
sinus  ;  7,  spinal  sinus ;  8,  communicating  branch  of  the  cavernous  sinuses ;  9,  internal  maxillary 
vein  receiving  above;  10,  10,  10,  the  pterygoid  veins;  11,  trunk  of  the  temporal  veins;  12,12, 
jugular  vein;  13,  posterior  auricular  vein;  14,  occipital  vein;  15,  radicle  of  the  occipital  vein 
arising  from  posterior   extremity  of  the  subsphenoidal  confluent;   16,  16,  facial  vein. 

The  Spinal  Sinuses  in  Particular. — We  thus  designate  in  Veterinary 
Anatomy — and  with  good  reason — two  series  of  venous  reservoirs  which  are  found 


694  THE   VEINS. 

throughout  the  whole  extent  of  the  vertebral  column,  on  the  sides  of  the  roof 
of  the  spinal  canal.  Lodged  in  the  lateral  depressions  on  the  superior  face  of 
the  vertebral  bodies,  at  the  side  of  the  common  superior  vertebral  ligament,  and 
covered  by  the  dura  mater,  these  reservoirs,  continued  from  one  vertebra  to  the 
other,  are  like  two  large,  irregular,  parallel  veins,  which  commence  at  the  atlo- 
axoid  articulation,  terminate  on  the  first  coccygeal  vertebrae,  where  their  presence 
is  yet  well  defined,  and  communicate  with  one  another  during  their  course  by 
transversal  anastomoses  (Fig.  386,  3). 

Affluent  Veins  that  open  into  the  Sinuses  of  the  Dura  Mater. — 
These  are  the  vessels  which  carry  blood  either  from  the  dura  mater  itself,  or 
from  the  substance  of  the  nerve-centres  :  those  of  the  first  category  are  rare,  but 
the  second  are  numerous.  Although  we  are  unwilling  to  make  a  detailed  study 
of  the  latter,  we  must  nevertheless  notice  what  is  most  remarkable  in  their 
disposition. 

a.  On  the  brain,  the  veins  form  a  much  richer  and  closer  network  than  that 
of  the  arterial  ramifications ;  from  this  network  proceed  a  certain  number  of 
principal  branches,  which  throw  themselves  into  the  sinuses  of  the  cranial  dura 
mater.  The  veins  of  the  cerebrum,  for  the  most  part,  gain  the  median  and 
transverse  sinuses ;  a  few  only  pass  into  the  cavernous  sinuses.  Those  of  the 
medulla  oblongata  and  cerebellum  go  to  the  petrosal  and  occipital  sinuses. 

With  regard  to  the  internal  veins  of  the  brain — those  which,  by  their  inter- 
lacing, constitute  the  choroid  plexus — they  unite  into  a  large  trunk — the  great 
vein  of  the  brain,  or  vena  Galeni,  which  bends  round  the  superior  extremity  of  the 
corpus  callosum,  reaches  the  interlobular  fissure,  and  enters  the  falciform  or 
middle  sinus,  near  its  posterior  end,  after  receiving  the  superficial  veins  from 
the  inner  face  of  the  hemispheres. 

b.  The  venules  arising  from  the  spinal  cord  are  also  very  remarkable  for  the 
fine  network  they  form  on  the  surface  of  the  organ.  They  collect  into  a  common 
trunk — the  median  spinal  vein,  which  runs  from  before  to  behind,  throughout 
the  whole  extent  of  the  superior  groove  in  the  spinal  cord ;  thus  occupying  an 
analagous,  though  opposite,  position  to  that  of  the  artery  of  the  same  name. 
From  this  vein  escape,  at  intervals,  emergent  branches  which  open  into  the  spinal 
sinuses. 

Effluent  Canals  of  the  Dura  Mater  Sinuses. — We  have  to  notice, 
under  this  designation,  the  veins  which  carry  the  blood  from  the  sinuses,  and 
will  consider  in  succession  those  which  commence  at  the  cranial  sinuses,  as 
well  as  those  that  emerge  from  the  interspinal  canals. 

a.  To  be  carried  from  the  cranial  sinuses,  the  blood  flows  into  two  kinds  of 
double  gulfs,  known  as  the  parieto-temporal  or  subsphenoidal  conff vents. 

The  parieto-temporal  confluents  are  lodged  in  the  canals  of  the  same  name, 
along  with  the  mastoid  artery.  Each  commences  at  the  base  of  the  internal 
parietal  protuberance,  and  terminates  behind  the  supra-condyloid  eminence.  The 
median  and  transverse  sinuses  are  confounded  with  the  superior  extremity  of 
these  reservoirs,  and  empty  into  them  the  blood  coming  from  the  encephalic 
mass.  This  fluid  is  subsequently  taken  away  by  the  superficial  and  deep  temporal 
veins,  which  have  their  principal  radicles  in  these  confluents. 

In  Ruminants,  the  parieto-temporal  confluent  opens  into  the  temporal  veins,  and  has  in 
front  a  branch  that  passes  to  the  foramen  lacerum  basis  crauii.  In  the  Pig  and  Cat,  it  is 
lodged  in  the  two  grooves  which  open,  one  at  the  anterior  foramen  lacerum,  the  other  at  the 
posterior. 


THE  ANTEEIOR   VENA   CAVA. 


Fig.  387. 


The  suhsphmoidal  confluents  (Fig.  387)  extend  on  the  sides  of  the  body  of 
the  sphenoid  bone  and  basilar  process,  from  the  base  of  the  subsphenoidal 
process  to  the  condyloid  fossa,  concurring  in  the  closing  of  the  occipito-spheno- 
temporal  hiatus.  They  open  at  their  middle  portion  into  the  corresponding 
cavernous  sinus,  by  an  oval  aperture  which  the 
internal  carotid  artery  traverses  in  penetrating 
into  the  cranium.  The  anterior  extremity 
terminates  in  a  cul-de-sac.  Posteriorly,  they 
communicate  through  the  condyloid  foramina 
with  the  occipital  sinuses.  The  vessels  which 
carry  off  the  blood  from  these  confluents  are 
the  pterygoid  veins,  and  the  anterior  radicle  of 
the  occipital  vein.  "We  know  that  the  posterior 
branch  of  the  latter  vessel  removes  the  blood 
directly  into  the  occipital  sinuses. 

h.  The  emergent  veins  of  the  spinal  sinuses 
present  a  more  simple  disposition.  At  each 
intervertebral  space  arise  several  branches, 
which  more  particularly  make  their  exit  by  the 
intervertebral  foramina  to  join  the  neighbour- 
ing veins  ;  in  the  cervical  region,  the  vertebral 
veins  serve  as  a  receptacle  in  this  way  for  the 
venous  branches  from  the  spinal  sinuses  ;  in 
the  dorsal  region,  it  is  the  spinal  branches  of 
the  intercostals  ;  in  the  loins,  the  analogous 
branches  of  the  lumbar  veins  ;  and  in  the  sacral 
region,  the  lateral  sacral  vein. 

As  a  whole,  the  venous  system  of  the 
cerebro-spinal  centres  presents  a  special  physi- 
ognomy. The  veins  arising  from  the  nerve 
substance  or  the  meninges,  instead  of  passing 
immediately  into  the  veins  of  the  neck  or  head, 
open  at  first  into  irregular  cavities  {sinuses) 
established  between  the  cranium  and  the  mem- 
branes enveloping  the  nervous  centres,  or  ex- 
cavated in  the  cranial  walls.  The  blood  collects 
in  certain  of  these  cavities,  named  confluents, 
whence  the  vessels  go  which  finally  open  into 
the  deep  or  superficial  veins  of  the  cervical 
region.  There  are,  therefore,  two  stages  be- 
tween the  veins  of  the  brain  or  spinal  cord 
and  the  veins  of  the  neck  and  face — the  sinuses 
and  confluents. 


SUBSPHENOIDAL   CONFLUENTS   IN 
THE   HORSE. 

1,  Middle  part  of  the  subsphenoidal 
confluent  (right  side);  2,  anterior 
extremity  of  ditto ;  3,  posterior 
extremity  in  the  subcondyloid  cavity 
of  the  occipital  bone ;  4,  one  of  the 
pterygoid  veins,  discharging  from 
the  confluent ;  5,  6,  anterior  radicles 
of  the  occipital  vein,  discharging 
from  the  confluent ;  7,  posterior 
radicle  of  the  left  occipital  vein;  8, 
occipital  vein ;  9,  9,  temporal  veins, 
discharging  from  the  parieto-tem- 
poral  confluents ;  10,  temporal 
condyle;  11,  tuberosity  of  the 
temporal  bone;  12,  styloid  process 
of  the  occipital  bone ;  13,  condyle 
of  ditto;  14,  atlas;  15,  axis;  16, 
rectus  capitis  anticus  muscle. 


Axillary  Veins. 

A  general  confluent  of  all  the  veins  of  the  thoracic  limb  and  of  some  from 
the  trunk,  the  axillary  vein  commences  beneath  the  scapulo-humeral  articulation, 
towards  the  terminal  extremity  of  the  corresponding  arterial  trunk,  accompanying 


696  THE   VEINS. 

the  latter  to  the  entrance  of  the  chest,  and  joining  the  confluent  of  the  jugulars 
to  constitute,  with  these  two  vessels,  the  inferior  vena  cava  (Fig.  389,  18). 

In  studying,  from  their  origin  to  their  termination,  the  numerous  branches 
which  concur  in  the  formation  of  this  venous  trunk,  we  recognize  : — 

1.  That  they  form  in  the  foot  a  very  rich  network,  from  which  proceed  the 
digital  reins,  satellite  vessels  of  the  homonymous  arteries. 

2.  That  to  these  digital  veins,  which  are  united  in  an  arch  above  the 
sesamoids,  succeed  three  metacarpal  branches,  or  collaterals  of  the  cannon — two 
superjjcials,  placed  on  each  side  of  the  flexor  tendons,  and  a  deep  vein,  situated 
underneath  the  suspensory  ligament,  along  with  the  interosseous  arteries. 

3.  That  the  metacarpal  veins  also  open  into  each  other,  in  the  superior  and 
posterior  region  of  the  carpus,  to  form,  on  again  separating,  two  groups  of  anti- 
hrachial  veins :  one  group  comprising  the  idnar  and  the  posterior  or  interned 
radials,  which  accompany  the  arteries  of  the  same  name  ;  the  other,  constituted 
by  a  single  subcutaneous  branch — the  median  veiii — which  receives  at  its  superior 
extremity  the  anterior  superficial  radial  vein. 

4.  That  at  the  ulnar  articulation,  these  two  groups  of  antibrachial  veins  join 
the  satellite  vessel  of  the  anterior  radial  artery,  and  communicate  by  a  very 
complicated  system  of  anastomoses,  from  which  results  a  principal  trunk — the 
humeral  rein. 

0.  That  the  humercd  vein,  after  receiving  on  its  course  several  muscular 
branches  and  the  subcutaneous  thoracic  vein,  unites  near  the  shoulder- joint  with 
the  brachial  or  subscapular  trunk,  to  form  the  axillary  vein. 

We  will  study  all  these  branches  in  the  inverse  order  of  their  enumeration. 

1.  Brachial  oe  Subscapular  Vein. 

A  very  considerable  vessel,  the  arrangement  of  which  resembles  that  of  the 
subscapular  artery,  though  presenting  some  special  peculiarities  which  do  not 
merit  much  attention  ;  for  example,  it  most  frequently  receives  the  satellite  vein 
of  the  prehumeral  artery. 

2.  Humeral  Vein. 

Placed  behind  and  to  the  inner  side  of  the  humeral  artery,  this  vessel  com- 
mences above  the  articulation  of  the  elbow,  being  formed  at  this  point  by  the 
anastomosing  system  of  veins  from  the  forearm,  and  terminates  below  the  shoulder- 
joint  in  opening  into  the  subscapular  vein. 

Independently  of  the  subcutaneous  thoracic  vein,  which  will  be  studied  in 
a  special  manner,  the  humeral  vein  receives  on  its  way  several  collateral  satellites 
of  the  branches  emanating  from  the  humeral  artery.  One  of  these,  the  epicondy- 
loid,  is  only  a  continuation  of  the  ulnar  vein. 

Very  often  we  find  a  second  humeral  vein  in  the  deep  region  of  the  arm ; 
this  is  an  accessory  vessel,  parallel  to  the  preceding,  and  situated  opposite  it,  in 
front  of  the  artery. 

3.  Subcutaneous  Thoracic  or  Spur  Vein. 

This  vein,  which  is  important  to  know,  as  bleeding  is  sometimes  practised 
from  it,  commences  on  the  flank  and  belly  by  numerous  superficial  divisions, 
which  unite  in  two  principal  radicles  and  afterwards  become  a  single  trunk, 
placed  in  the  substance,  or  on  the  external  surface  of  the  panniculus  carnosus, 


THE  ANTERIOR    VENA    CAVA.  697 

where  it  is  directed  forwards  in  following  the  superior  border  of  the  posterior 
superficial  pectoral  muscle,  accompanied  by  an  arterial  ramuscule  and  a  thick 
nerve.  It  insinuates  itself  beneath  the  olecranian  muscles,  and  finally  terminates 
in  the  humeral  vein  by  joining  the  branch  that  follows  the  deep  muscular  artery. 


4.  Deep  Veins  of  the  Forearm. 

A.  Anterior  Radial  Vein. — This  follows  the  same  track,  and  affects  the 
same  variations,  as  the  corresponding  artery. 

B.  Posterior  Radial  Veins. — The  posterior  radial  artery  is  always  accom- 
panied, and,  as  it  were,  enveloped,  by  a  fasciculus  of  three  or  four  venous 
branches,  which  frequently  anastomose  with  each  other,  and  are  reinforced  by 
collateral  branches,  among  which  the  interosseous  vein  must  be  noted. 

These  radial  branches  commence  above  the  carpus,  by  continuing  the  meta- 
carpal veins.  They  concur  to  form  the  humeral  vein,  in  joining  the  other 
antibrachial  veins  at  the  inferior  extremity  of  the  arm. 

C.  Ulnar  Vein. — This  vessel  is  lodged,  with  the  nerve  and  small  artery  of 
the  same  name,  in  the  interspace  between  the  oblique  and  internal  flexors  of  the 
metacarpus.     A  number  of  muscular  and  subcutaneous  branches  enter  this  vein. 

It  has  the  same  origin  as  the  posterior  radial  veins.  Its  superior  or  terminal 
extremity  bends  forward,  close  to  the  trunk  of  the  ulnar  artery,  and  goes  to  the 
inferior  extremity  of  the  humeral  vein.  Frequently  the  ulnar  vein  is  double  in 
the  latter  portion  of  its  track,  and  between  these  two  branches  lies  the  artery. 
It  always  communicates  at  this  point,  by  one  or  more  branches,  with  the  deep 
muscular  vein. 


5.  Superficial  Veins  of  the  Forearm. 

Placed  outside  the  fibrous  sheath  formed  by  the  antibrachial  aponeourosis, 
these  veins,  which  are  principally  two  in  numlber,  are  maintained  against  the 
external  face  of  that  membrane  by  a  thin  fascia  that  separates  them  from  the 
skin. 

A.  Median  or  Internal  Subcutaneous  Vein  (Fig.  389,  31). — This  is 
also  one  of  the  vessels  selected  for  the  operation  of  phlebotomy.  It  is  the 
continuation  of  the  internal  metacarpal  vein,  ascends  from  the  inner  face  of  the 
carpus  to  the  superior  extremity  of  the  forearm,  by  crossing  the  radius  in  a  very 
oblique  manner,  and  terminates  in  two  very  large  branches,  the  posterior  of 
which  is  the  basilic  vein,  and  the  anterior  the  cephalic  vein. 

The  basilic  vein  traverses  the  superficial  pectoral  muscle,  to  aid  in  forming 
the  humeral  trunk  (Fig.  389,  34). 

The  cephalic,  or  plate  vein,  crosses  the  superficial  band  of  the  biceps  muscle,  is 
lodged  in  the  space  comprised  between  the  mastoido-humeralis  and  anterior 
superficial  pectoral  muscles,  and  afterwards  opens  in  the  jugular  vein  (Fig. 
389,  35). 

B.  External  Subcutaneous  or  Anterior  Radial  Vein  (Fig.  389,  32). 
— Less  considerable  than  the  preceding,  this  vein  arises  at  the  carpal  region,  in 
its  course  occupies  the  anterior  face  of  the  forearm,  and  terminates  in  uniting  its 
superior  extremity  either  to  the  internal  subcutaneous,  or  the  cephalic  vein  ;  the 
last  is  most  frequently  the  case. 


TEE   VEINS. 


6.  Metacarpal  Veins. 


Three  in  number,  these  veins  are  distinguished  into  internal  and  external 
metacarpals  or  collaterals  of  the  cannon,  and  deep  or  interosseous  metacarpal  or 
collateral. 

A.  Internal  Metacarpal  Vein. — More  voluminous  than  the  others,  this  vein 
passes  from  the  vicinity  of  the  fetlock  along  the  flexor  tendons,  accompanied  by 
the  principal  artery  of  the  cannon  and  the  external  plantar  nerve,  places  itself  in 
the  special  sheath  which  envelops  the  common  trunk  of  the  interosseous  arteries 
to  the  inside  of,  and  behind  the  carpus,  to  be  continued  in  the  antibrachial 
region  by  the  internal  subcutaneous  vein,  after  communicating  with  the  other 
metacarpal  veins  (Fig.  389,  30). 

B.  External  Metacarpal  Vein. — Situated  opposite  the  preceding — to  the 
external  side  of  the  flexor  tendons,  in  company  with  the  corresponding  plantar 
nerve — this  vessel  follows  that  nerve  to  near  the  supra-carpal,  and  then  separates 
into  several  reticulate  branches  which  anastomose  with  the  internal  vein,  from 
which  proceed  the  ulnar  and  internal  or  posterior  radial  veins. 

C.  Interosseous  Vein. — A  tortuous,  irregular,  and  sometimes  multiple 
vessel,  lodged  with  the  plantar  interosseous  arteries  between  the  suspensory 
ligament  and  the  posterior  face  of  the  principal  metacarpal  bone.  Reaching  the 
superior  extremity  of  that  bone,  it  unites  largely  to  the  right  and  left  with  the 
external  and  internal  metacarpals,  sending  upwards  one  or  two  small  branches 
which  traverse  the  carpal  sheath  along  with  the  collateral  artery  of  the  cannon, 
and  enter  into  the  posterior  radial  branches  above  the  knee. 

7.  Digital  Veins. 

These  veins  occupy,  on  the  sides  of  the  digital  region,  the  samo  position  as 
the  homonymous  arteries  in  front  of  which  they  are  placed  They  arise  from 
the  network  formed  on  the  lateral  cartilages  by  the  veins  of  the  foot,  and  termi- 
nate in  uniting  above  the  fetlock,  between  the  flexor  tendons  of  the  phalanges 
and  the  suspensory  ligament,  so  as  to  form  an  arch  (the  sesamoidecai)  from  which 
proceed  the  three  metacarpal  veins  (Fig.  389,  37). 

8.  Veins  of  the  Foot  oe  Ungual  Eegion. 

The  importance  of  the  region  to  which  these  vessels  belong,  requires  that 
they  should  be  described  more  fully  than  the  other  veins,  and  as  has  been 
already  done  with  the  arteries  of  this  part  of  the  body.  We  will,  therefore, 
borrow  the  exact  and  minute  description  given  by  M.  H.  Bouley.^ 

This  venous  apparatus  may  be  divided  into  external  and  internal  or  intra- 
osseous. 

a.  External  Venous  Apparatus. 

"  The  external  venous  apparatus  of  the  digital  region  is  very  remarkable  for 
the  nmnber,  development,  superficial  distribution,  and  reticulated  disposition  of 
the  canals  composing  it.  To  give  an  idea  of  this,  we  cannot  do  better  than 
compare  its  general  form  to  a  net  whose  irregular  meshes  are  extended  over,  and 
moulded  on,  the  two  last  phalanges  which  are  contained  in  it. 

"  This  intricate  reticulation  of  the  venous  apparatus  of  the  foot  is  marvel- 
lously displayed  in  specimens  injected  after  maceration,  and  then  dried. 
'  TraiU  de  V  Organization  du  Pied  du  Cheval,  p.  65. 


TEE  ANTERIOR    VENA   CAVA.  699 

"  To  facilitate  its  description,  we  recognize  in  it  three  parts  distinct  by  their 
situation,  though  they  only  form  a  continuous  one.     They  are  : 

"  1 .  The  solar  plexus. 

"2.  ThB  podophyllous  plexus. 

"  3.  The  coronary  plexus. 

"  A  Solar  Plexus. — The  veins  of  the  solar  plexus  are  remarkable  for  the 
equaUty  of  their  calibre  throughout  the  whole  extent  of  the  plantar  surface,  and 
by  the  almost  absolute  absence  of  anastomotic  communications  with  the  deep 
parts. 

"  Sustained  in  a  special  fibrous  web  {plantar  reticulum),  which  replaces  the 
periosteum  at  the  lower  surface  of  the  phalanx,  and  is  a  continuation  of  the 
corium  of  the  villous  tissue,  these  veins  appear  indeed  to  have  so  little  commu- 
nication, except  with  each  other,  that  it  is  possible  to  detach  the  plantar  reticu- 
lum from  the  superior  face  of  the  third  phalanx  without  disturbing  them. 

"  The  general  disposition  of  the  veins  in  the  texture  of  the  reticulum 
supporting  them,  closely  resembles  that  of  the  secondary  ribs  of  the  limb  (or 
laminar  meritliaX)  of  certain  asymmetrical  leaves.  In  their  course  they  follow  an 
irregularly  broken  Hne,  intercepting  each  other  by  joining  at  short  intervals,  so 
as  to  form  unequal-sized,  unsymmetric,  polygonal  spaces. 

"  These  veins  discharge  themselves  by  a  double  canal — a  central,  the  least 
considerable  and  least  constant ;  the  other,  peripheral  or  circumflex,  correspond- 
ing to  the  artery  of  the  same  name,^  and  of  which  it  is  the  satellite  vein. 

"  Central  canal. — The  central  canal  is  formed  by  the  simultaneous  anasto- 
moses of  a  crowd  of  venous  ramifications  converging  towards  the  centre  of  the 
digit.  It  is  of  a  parabolic  shape,  and  embraces  in  the  concavity  of  its  curvature 
the  point  of  the  pyramidal  body,  whence  it  throws  its  two  branches  in  a  parallel 
manner  on  the  sides  of  that  body,  into  the  bottom  of  the  lateral  lacunas  as  far  as 
the  cartilaginous  bulbs,  where  it  proceeds  to  the  external  coronary  plexus.  This 
disposition  is  not  constant,  however,  as  specimens  are  frequently  met  with  in 
which  this  central  canal  is  replaced  by  multiple  veins,  which  are  more  consider- 
able than  those  forming  the  whole  of  the  plexus,  and  which  serve  them  as  over- 
falls towards  the  superficial  coronary  plexus. 

"  Circumflex  or  peripheral  vein. — This  vein  is  of  large  calibre,  and  formed  by 
divergent  ramifications  from  the  solar  plexus,  as  well  as  the  descending  veins 
of  the  podophyllous  plexus  ;  it  margins  the  external  border  of  the  villous  tissue, 
in  following  a  slightly  undulous  hne  within  the  circumflex  artery,  of  which  it  is 
the  satellite.  It  is  sometimes  broken  up,  at  certain  points  of  its  course,  into 
several  smaller  canals  which  are  continuous  with  its  trunks. 

"  In  its  circular  route,  all  the  divergent  solar  and  descending  podophyllous 
veins  are  discharged  into  it,  and  it  terminates,  at  the  extremities  of  the  crescent 
formed  by  the  third  phalanx,  in  several  large  branches  which  pass  beneath  the 
podophyllous  tissue  to  the  lateral  cartilage,  where  they  concur  to  form  the 
superficial  coronary  plexus. 

"B.  Podophyllous  Venous  Plexus  or  Network. — The  veins  of  the 
podophyllous  plexus  exhibits  a  disposition  analogous  to  those  of  the  solar  plexus  ; 
like  them,  they  are  sustained  in  the  meshes  of  a  fibrous  texture  (the  reticulum 
processigerum  of  Bracy  Clark,  the  suhpodophtjlJous  reticulum  of  French  Veteri- 
narians) spread  on  the  anterior  surface  of  the  bone,  in  the  same  way  as  the 
periosteum  is  on  other  bones,  and  continuous  with  the  corium  of  the  laminal 
'  The  inferior  circumflex  artery  of  the  foot. 


700 


THE   VEINS. 


tissue.  Communicating  largely  between  each  other  by  multiple  anastomoses,  like 
the  solar  plexus,  they  appear  to  be  completely  isolated  from  the  deeper  parts, 
from  which  it  is  commonly  believed  they  emanate. 

"  Tortuous  and  split  up  into  branches  in  their  course,  the  podophyllous  veins 
wind  in  a  serpentine  manner  along  the  length  of  the  laminfe  they  cover,  very 
close  to  each  other,  and  forming  narrow  elongated  meshes.  Their  confluence  is 
such,  that  at  certain  points  they  appear  bound  together  by  their  external  walls. 

"  The  calibre  of  these  vessels  is  tolerably  uniform  throughout  the  extent  of 
the  podophyllous  plexus,  except  towards  the  posterior  parts,  where  their  principal 
canals  empty  themselves  into  the  coronary  plexus, 

"  The  podophyllous  veins  are  in  anastomotic  communication,  below,  with  the 

circumflex  vein  of  the  solar  plexus, 
Fig.  388.  which  they  concur    to    form,  and 

above,  with  the  coronary  plexus, 
which  is  only  a  continuation  of  them. 
"  C.  Coronary  Venous  Plexus. 
— The  coronary  venous  plexus  (Fig. 
388,  2,  4)  is  arranged  like  a  ramose 
garland  around  the  second  phalanx 
to  the  origin  of  the  third,  and  on  the 
surface  of  the  cartilaginous  apparatus 
which  completes  the  latter. 

"It  is  supported,  Uke  the  other 
venous  networks  of  the  digit,  by  a 
fibrous  texture  immediately  subjacent 
to,  and  continuous  with,  the  corium 
of  the  coronary  substance,  and  is 
juxtaposed,  as  well  as  adherent,  to 
the  expansion  of  the  extensor  tendon, 
the  lateral  cartilages,  and  to  the 
bulbous  enlargements  of  the  plantar 
cushion. 

"  This  plexus  proceeds  from  the 
intra-osseous,  podophyllous,  and  solar 
networks.     To  facilitate  its  descrip- 
tion, we  recognize  it  in  three  parts  : 
one  central  and  anterior,  situated  between  the  two  cartilaginous  plates,  and  two 
lateral,  corresponding  to  these  cartilages. 

"Central  Part  of  the  Coronary  Plexus. — The  central  part  of  the 
coronary  plexus  (Fig.  388,  2),  immediately  subjacent  to  the  substance  or  cushion 
of  that  name,  constitutes  a  very  close  network  formed  by  innumerable  venous 
radicles,  which  rise  in  a  tortuous  manner  from,  and  are  continuations  of,  the 
podophyllous  plexus,  until  they  reach  a  large  anastomotic  vein  thrown  across 
from  one  cartilaginous  plexus  to  the  other,  and  into  which  they  open  by  from 
ten  to  twelve  principal  mouths  (Fig.  388,  3'). 

"  These  veins  of  the  central  part  of  the  coronary  plexus  gradually  increase  in 
calibre,  and  diminish  in  number,  from  the  podophyllus  plexus,  where  they  take 
their  origin,  to  their  superior  and  terminating  canal,  which  itself  only  apjDears  to 
be  the  result  of  their  successive  anastomoses. 

"  Cartilaginous  Plexus,  or  Lateral  Parts  of  the  Coronary  Plexus. 


THE   VEINS  OF    THE   FOOT. 


THE  ANTERIOR    VENA    CAVA.  701 

— The  cartilaginous  plates  serve  to  support,  by  their  two  faces  and  the  canali- 
culi  by  which  they  are  traversed,  a  mass  of  very  close,  anastomosing,  and  con- 
verging veins,  which,  from  its  situation,  may  be  designated  the  cartilaginous 
plexus. 

"  This  cartilaginous  plexus  is  formed  by  two  layers  of  vessels — a  siqjerficial 
and  deep. 

"  Superficial  cartilaginous  layer  or  plexus. — The  superficial  layer  (Fig.  388, 
3,  4),  extended  over  the  external  surface  of  the  cartilaginous  plates  and  bulbs, 
has  its  origin  by  innumerable  radicles  from  the  veins  of  that  part  of  the  podo- 
phyllous  plexus  corresponding  to  the  superficies  it  occupies.  These  roots,  massed 
in  a  very  dense  network,  converge  towards  the  superior  portions  by  diminishing 
in  number  and  augmenting  in  volume,  and  terminate  in  forming  themselves,  by 
the  aid  of  successive  anastomoses,  into  ten  or  twelve  principal  branches  which 
again  unite  into  two  considerable  vessels  (Fig.  388,  6),  situated  at  the  superior 
limit  of  the  plexus.  These  vessels,  finally,  by  their  last  fusion  at  the  inferior 
extremity  of  the  first  phalanx,  constitute  the  digital  vein,  the  satellite  of  the 
artery  of  the  same  name  (Fig.  388,  5). 

"  Considered  from  below  upwards,  in  a  foot  previously  prepared  by  injection, 
the  digital  vein,  divided  into  two  branches,  subdivides  itself  into  secondary 
branches  and  ramuscules  which  diverge  and  spread  over  the  convex  surface  of 
the  cartilage  and  coronary  cushion,  resembling  somewhat  the  disposition  of  trees 
trained  as  espaliers,  whose  spreading  branches  are  fixed  to  the  walls  on  which 
they  ramify. 

"  The  two  peripheral  branches  of  the  superficial  cartilaginous  plexus  establish 
communications  with  the  opposite  cartilaginous  plexus,  in  contracting  direct 
anastomoses  with  the  branches  of  the  plexus  which  are  symmetrical  to  them. 

"  The  anterior  anastomosing  canals  are  double  and  superposed. 

"  The  most  inferior  and  superficial  is  constituted  by  the  large  vein  (Fig  388, 
3')  thrown  slantingly  across  from  one  plexus  to  the  other  in  the  median  plane, 
and  on  the  external  surface  of  the  extensor  tendon  ;  this  receives  a  considerable 
multitude  of  venous  ramuscles,  which  emerge  from  the  anterior  part  of  the  podo- 
phyllous  plexus. 

"  This  first  communicating  vein  joins  the  anterior  branches  of  the  carti- 
laginous plexus. 

"  The  second  communicating  vein,  situated  three-quarters  of  an  inch  above 
the  first,  and  beneath  the  tendon,  is  thrown  transversely  from  one  anterior 
branch  of  the  plexus  to  the  other.  They  open  into  each  other  on  each  side,  at 
the  same  point  where  the  first  communicating  vein  enters. 

"  Sinuous  in  the  whole  of  its  track,  sometimes  double,  and  sometimes  formed 
of  several  confluent  veins — as  in  Fig.  388 — this  anastomosing  canal  serves  as  an 
outlet  for  several  deep  veins. 

"  The  anastomosis  between  the  posterior  peripheral  branches  of  the  cartila- 
ginous plexus  is  formed  by  an  irregularly  curved  and  long  vein  of  large  calibre, 
sinuous  or  broken  in  its  course,  but  always  considerably  longer  than  the  distance 
from  the  two  cartilaginous  plates  between  which  it  is  extended. 

"  This  posterior  communicating  vein  acts  as  a  confluent  to  the  canals  emerging 
from  the  cartilaginous  bulbs,  and  to  the  posterior  part  of  the  solar  plexus,  which 
throws  into  it  five  or  six  well-developed  afferent  veins. 

"  Deep  cartilaginous  layer  or  plexus. — The  deep  layer  of  the  cartilaginous 
plexus  is  formed  : 
47 


702  TEE   VEINS. 

"1,  By  somewhat  large  ascending  branches  from  the  posterior  part  of  the 
podophyllous  and  solar  plexuses. 

"2.  By  the  deep  internal  venous  apparatus  of  the  third  phalanx. 

"  3.  By  the  deep  veins  arising  from  the  coronary  bone  and  the  ligaments 
and  tendons  surrounding  it. 

"  The  ascending  branches  of  the  podophyllous  tissue  are  introduced  by  the 
numerous  foramina  which  traverse  the  base  of  the  cartilaginous  plate  and  the 
inferior  fibrous  covering  of  the  plantar  cushion  ;  they  follow  the  canals  which 
continue  those  foramina  in  the  substance  of  the  cartilage,  and  reach  its  internal 
face,  along  with  the  branches  proceeding  from  the  intra-osseous  venous  system 
and  those  coming  from  the  tendons  and  ligaments,  forming  a  fasciculus  of  five 
or  six  thick  converging  veins  which  unite  in  two  large  ascending  branches. 
These  anastomose  with  each  other  before  their  definitive  junction  with  the  two 
peripheral  branches  resulting  from  the  superficial  cartilaginous  plexus,  with. 
which  they  concur  in  constituting  the  digital  vein." 

b.  Internal  or  Intra-osseous  Venous  Apparatus. 

"  Girard,  junior,  and  Rigot  have  denied  that  the  plantar  artery  had,  in  the 
interior  of  the  phalanx,  a  satellite  venous  system.  These  two  able  anatomists 
committed  an  error. 

"  The  disposition  of  the  venous  apparatus  in  the  interior  of  the  phalanx  is 
absolutely  identical  with  that  of  the  arterial. 

"  The  satellite  radicular  venules  of  the  terminal  arteries  converge,  by  forming 
successive  anastomoses,  towards  the  semilunar  sinus,  into  which  they  enter  by 
the  anterior  interosseous  canals,  ascending  and  descending,  and  by  which  the 
emergent  arteries  from  the  semilunar  anastomosis  pass  outwards.  There  they 
join  into  a  semicircular  canal,  the  satellite  of  that  anastomosis,  which  is  con- 
tinued backwards  by  two  efferent  veins  that  follow  the  posterior  canals  of  the 
semilunar  sinus,  emerge  by  the  plantar  foramina,  pass  into  the  fissure  of  the 
same  name,  ascend  within  the  basilar  process,  He  at  the  internal  face  of 
the  cartilaginous  plate,  in  one  of  the  infractuosities  with  which  it  is  sculptured, 
and  concur  in  the  formation  of  the  deep  layer  of  the  cartilaginous  plexus. 

"Beside  these  veins  converging  towards  the  cartilaginous  plexus,  there  is 
a  small  number  of  divergent  ones  which  follow  the  track  of  the  arteries,  and 
pass  into  the  podophyllous  plexus  through  the  anterior  porosities  of  the  phalanx. 

"  The  dissection  of  specimens  injected  by  the  veins  puts  this  arrangement  of 
the  venous  apparatus  in  the  interior  of  the  os  pedis  beyond  a  doubt. 

"  But  is  this  internal  venous  system  limited  to  the  group  of  vessels  which 
are  satellites  of  the  arteries,  or  is  it  not  rather  extended  over  a  vaster  surface, 
and  may  not  all  the  areolae  of  the  spongy  tissue  of  the  bone  be  considered  as  a 
dependency  of  it  ? 

"  This  way  of  viewing  it  would  seem  to  be  supported  by  the  result  of  certain 
injections,  in  which  the  material  introduced  by  the  neighbouring  veins  has  filled 
all  the  internal  spongiolae  of  the  bony  tissue  ;  though  this  was  probably  due  to 
an  accident  in  the  operation,  and  it  is  presiunable  that  the  direct  passage  of  the 
venous  injection  into  the  areolae  of  the  spongy  tissue  arose  from  a  rupture  in  the 
vascular  walls.  If  the  tissue  of  the  phalanx  formed  a  kind  of  diverticuliun  for 
the  venous  system,  as  the  opinion  just  given  would  admit,  operations  performed 
on  this  part  during  life,  when  the  texture  of  the  bone  is  deeply  involved,  ought 


THE  POSTEBIOR    VENA    CAVA.  703 

to  be  followed  by  haemorrhage  from  the  open  orifices  of  these  areolae — a  circum- 
stance which  does  not  take  place. 

"  It  does  not  appear,  therefore,  that  there  is,  in  the  structure  of  the  third 
phalanx,  any  departure  from  the  general  plan  on  which  bones  are  constructed, 
and  we  think  that  its  internal  venous  system  is  hmited  to  the  vessels — very 
numerous  as  they  are — which  accompany  the  arterial  divisions." 

Akticle  III.— Posteeior  Vena  Cava  (Figs.  349,  v ;  350,/;  389). 

This  vein,  the  volume  of  which  is  not  equalled  by  that  of  any  other  vessel 
in  the  body,  commences  at  the  entrance  to  the  pelvis  by  two  large  roots,  the 
common  iliac  veins. 

From  this  point  it  is  directed  forward,  beneath  the  bodies  of  the  lumbar 
vertebrae,  soon  reaches  the  superior  border  of  the  liver,  where  it  leaves  the 
lumbar  region  to  lodge  itself  in  the  fissure  on  the  anterior  face  of  that  gland ; 
passing  through  this,  it  traverses  the  foramen  dextrum  of  the  diaphragm,  and 
opens  into  the  postero-external  part  of  the  right  am'icle  of  the  heart. 

In  this  course,  the  posterior  vena  cava  is  naturally  divided  into  three 
portions — a  sublumbar,  hepatic,  and  thoracic. 

The  sublumbar  portion,  placed  to  the  right  of  the  posterior  aorta  and  to  the 
left  of  the  right  kidney  and  supra-renal  capsule,  is  maintained  against  the 
common  inferior  vertebral  hgament  and  the  left  psoas  parvus  muscle  by 
the  peritoneum  and  the  pancreas.  It  is  related,  besides,  to  the  right  renal 
artery,  which  crosses  its  face  perpendicularly,  as  well  as  the  corresponding  great 
splanchnic  nerve  and  the  nerve  divisions  of  the  right  renal  and  lumbo-aortic 
plexuses. 

In  its  hepatic  portion,  the  posterior  vena  cava  is  only  related  to  the  liver  and 
diaphragm,  which  form  a  complete  canal  around  it. 

The  thoracic  portion  is  lodged  between  the  right  lung  and  its  internal  acces- 
sory lobule,  and  is  enveloped  by  a  particular  serous  fold — a  dependency  from  the 
right  pleura,  and  which  has  been  already  described  (p.  543). 

Collateral  afferents. — Those  vessels  which,  as  considerable  as  they  are  nume- 
rous, open  into  the  posterior  vena  cava,  are,  enumerating  them  from  before  to 
behind  : 

1.  ThQ  phrenic  or  diaphragmatic  veins. 

2.  The  vena  ported,  a  trunk  into  which  are  collected  the  majority  of  the 
abdominal  visceral  veins  ;  instead  of  opening  directly  into  the  vena  cava,  it  is 
divided  in  the  liver  like  an  artery,  reconstituting  itself  into  a  certain  nmnber  of 
thick  branches — the  hepatic  veins,  which  enter  the  vena  cava  on  its  way  through 
the  anterior  fissure  of  the  liver. 

3.  Renal  veins. 

4.  Spermatic  veins. 

5.  Lumbar  veins. 

All  these  vessels  will  be  studied,  in  the  order  above  indicated,  before  the 
radicles  or  common  iliac  veins  of  the  vena  cava. 

Phrenic  or  Diaphragmatic  Veins. 

These  are  two,  sometimes  three,  enormous  vessels  lodged  in  the  texture  of 
the  tendinous  centre,  commencing  by  several  branches  in  the  fleshy  portion  of 
the  muscle,  and  entering  the  vena  cava  as  it  passes  through  the  diaphragm. 


GENERAL  VIEW  OF  THE  VEINS  IN  THE  HORSE. 
1,  Anterior  vena  cava;  2,  2,  posterior  vena  cava;  3.  right  common  iliac  vein,  divided  at  the  ilio- 
sacral  articulation ;  4,  left  common  iliac  vein ;  5,  femoral  vein ;  6,  obturator  vein ;  7,  subsacral 
vein;  8,  left  spermatic  vein;  9,  posterior  abdominal  vein;  10,  renal  vem :  11,  11,  ascending 
branches  of  the  asternal  vein;  12,  vena  azvgos,  with  itsjntercostal  tranche^,  and  in  hjnt  the 
subdorsal   venous    branch,    13;    14,   oesophageal   vein:    "     '        '    '      "■ 


15,  dorsal   or    dorso-muscular  vein;    16, 


TEE  POSTEBIOR    VENA    CAVA.  705 

Vena  Portse  (Figs.  389,  390). 

The  manner  in  which  this  vessel  comports  itself  gives  it  an  altogether 
peculiar  physiognomy,  and  has  caused  it  to  be  considered  as  a  separate  vascular 
system.^  After  what  has  been  already  said  concerning  the  structure  of  the 
liver,  it  must  be  admitted  that  the  vena  port^e  is  distributed  in  that  gland 
exactly  like  an  artery. 

It  begins  in  the  sublumbar  region,  at  the  anterior  mesenteric  artery,  by  the 
union  of  three  large  radicles  ;  it  is  then  directed  forwards  and  a  little  to  the 
right,  traversing  the  pancreatic  ring,  below  the  vena  cava,  and  is  afterwards 
lodged  in  the  great  posterior  fissure  of  the  liver,  where  it  ramifies  by  forming 
the  interlobular  veins,  the  capillary  divisions  of  which  give  rise  to  the  sublobular 
vessels. 

Interlobular  and  sublobular  veins  (Fig.  303,  YP,  \h).  These  vessels  having 
been  already  studied  in  the  description  of  the  liver,  we  need  not  again  occupy 
ourselves  with  them,  but  refer  only  to  a  peculiarity  incompletely  noticed  in  that 
description,  with  reference  to  the  sublobular  veins. 

We  know  that  these  vessels  are  divided  into  two  categories,  according  to 
the  arrangement  of  their  openings.  The  majority  enter  the  vena  cava  in 
forming  a  single  confluent  placed  at  the  anterior  extremity  of  the  fissure  in 
the  liver,  at  the  phrenic  veins  ;  the  others  open  separately  over  the  whole 
extent  of  the  hepatic  portion  of  the  venous  trunk.  In  carefully  examining 
the  confluent  towards  which  all  the  veins  of  the  first  group  converge,  we 
recognize  the  junction  of  three  principal  veins,  one  coming  from  each  of  the 
hepatic  lobes,  and  furnished  with  three  very  isolated,  incomplete  valves.  With 
regard  to  the  vessels  of  the  second  group,  Claude  Bernard^  considers  them 
to  come,  for  the  most  part,  directly  from  the  sublobular  veins,  and  not  from 
the  capillary  network  formed  by  these  veins  in  the  lobules  of  the  liver.  It  is 
true  that  injections  readily  penetrate  from  the  vena  portse  into  the  vena  cava, 
but  they  do  this  quite  as  much  by  passing  along  the  large  sublobular  vessels 
as  the  canals  of  which  we  now  speak  ;  and,  besides,  if  the  material  forced  into 
the  vena  ports  is  mixed  with  some  imperfectly  powdered  colouring  matter, 
the  injection  will  arrive  colourless,  or  but  shghtly  tinged,  in  the  sublobular 
vessels  and  the  vena  cava.     These  facts,  we  see,  do  not  miUtate  in  favour  of 

'  Nevertheless,  there  are  communications  between  the  portal  system  and  the  general 
circulation,  through  the  medium  of  the  oesophageal  and  haemorrlioidal  veins.  These  com- 
munications become  very  evident  when  the  circulation  in  the  liver  is  obstructed. 

*  Legons  de  Physiologie  Expcrimentale.     Paris :  1856. 

cervical  or  cervico-muscular  vein ;  17,  vertebral  vein  ;  18,  right  axillary  vein,  cut  at  the 
anterior  border  of  the  first  rib;  19,  supra-sternal  or  internal  mammary  vein;  20,  left  axillary 
artery;  21,  termination  of  the  left  cephalic  vein;  22,  left  jugular;  23,  right  jugular;  24, 
external  maxillary  or  glosso-facial  vein;  25,  coronary  vein;  26,  angular  vein  of  the  eye;  27, 
subzygomatic  vein  ;  28,  posterior  auricular  vein  ;  29,  maxillo-muscular  vein ;  30,  internal  meta- 
carpal vein;  31,  internal  subcutaneous  vein;  32,  radial  subcutaneous  vein;  33,  posterior  radial 
vein;  34,  basilic  vein;  35,  plate  or  cephalic  vein;  36,  coronary  venus  plexus;  37,  digital  vein; 
38,  internal  metatarsal  vein  ;  39,  anterior  root  of  the  internal  saphena  vein ;  40,  posterior  root  of 
ditto;  41,  internal  saphena;  42,  great  coronary  vein;  43.  small  mesaraic  vein;  44,  different 
branches  of  the  great  mesaraic  vein  ;  45,  trunk  of  the  vena  porta  in  its  sublumbar  portion, 
lodged  in  the  pancreas;  46,  the  same  in  the  posterior  fissure  of  the  liver— below  it  is  seen  entering 
the  substance  of  the  gland,  il,  Subscapulo-hyoideus  muscle  cut  obliquely  in  the  direction  of  the 
trachea  ;  p,  cervical  panniculus  turned  down  to  expose  the  jugular  furrow  ;  o,  right  auricle  of  the 
heart ;  A,  posterior  aorta  ;  G,  section  of  the  right  lung  ;  f,  left  lobe  of  the  liver  behind  the  section 
of  the  diaphragm;  R,  right  Ijidney  carried  up  and  forward;  l,  oesophagus;  v,  bladder;  s,  rectum; 
T,  thoracic  duct ;  t'.  termination  of  that  duct  in  the  confluent  of  the  j'ugulars. 


706  THE   VEINS. 

Bernard's  opinion ;  and  there  is  every  reason  to  believe  that  the  system  of 
the  vena  ports  and  that  of  the  vena  cava  do  not  communicate,  in  the  adult, 
otherwise  than  by  the  capillary  network  which  is  intermediate  to  the  interlobular 
and  sublobular  vessels.  If  any  other  means  of  communication  exist,  they  must 
be  extremely  small. 

(Ligature  of  the  portal  vein  causes  distension  of  all  the  abdominal  vessels, 
and  a  highly  congested  state  of  the  abdominal  viscera  ;  whilst  the  blood-pressure 
quickly  falls,  and  the  animal  dies.  So  distensible  are  the  abdominal  vessels, 
that  they  can  contain  nearly  all  the  blood  in  the  body.  The  ventricular  systole 
may  send  a  pulse  down  the  valveless  posterior  vena  cava,  and  cause  a  pulse  in 
the  liver.  That  gland  swells  with  each  systole,  and  relaxes  with  each  diastole  of 
the  heart.) 

Constitumt  vessels  of  the  vena  portm. — The  three  roots  of  this  vein  are  the 
anterior  and  posterior  mesenteries  and  the  splenic  vein. 

The  collateral  affluents  it  receives  on  its  course  are  principally  two  :  the 
right  gastro-epiploic  or  gastro-omental  veins  and  anterior  gastric. 

We  will  make  a  rapid  survey  of  all  these  vessels. 

1.  Roots  of  the  Vena  Port^. 

A.  Anterior  Mesenteric  or  Anterior  Mesaraic  Vein  (Figs.  380,  44  ; 
390,  2,  7). — This  is  an  enormous  venous  canal  into  which  flows  the  blood  that 
has  passed  through  the  walls  of  the  small  intestine,  caecum,  large  colon,  and 
the  origin  of  the  small  colon,  the  divisions  of  which  con-espond  exactly  to 
the  different  branches  furnished  by  the  anterior  mesenteric  artery. 

When  traced  from  its  opening  to  its  origin,  in  an  inverse  direction  to  the 
course  of  the  blood,  it  is  observed  to  lie  between  the  two  colic  arteries,  and 
proceed  beyond  the  flexure  formed  by  the  supra-sternal  and  diaphragmatic 
flexures,  beyond  which  it  divides  into  two  satellite  branches  for  the  colic 
arteries,  which  anastomose  in  arcade  towards  the  pelvic  flexure,  like  the  arteries 
they  accompany. 

It  is  therefore  by  the  union  of  two  colic  veins  (Fig.  .390,  8,  9)  that  the 
anterior  mesenteric  vein  is  constituted,  and  in  this  formation  numerous  collateral 
affluents  concur  ;  among  these  may  be  noticed  the  two  cceecd  veins  (Fig.  390, 
5,  6),  the  ilio-ccecal  vein  (Fig.  390,  4)  coming  from  the  origin  of  the  floating 
colon,  and  the  veins  of  the  small  intestine — vessels  arranged  so  exactly  like  the 
corresponding  arteries,  that  we  may  dispense  with  any  further  description  of 
them. 

B.  Posterior  Mesenteric  or  Posterior  Mesaraic  Vein  (Figs.  389,  43  ; 
390,  12). — This  vessel  commences  above  the  rectum,  near  the  anus,  by  large 
hcmiorrhoidal  branches  which  communicate  with  the  homonymous  ramuscules 
of  the  internal  pudic.  It  is  directed  forwards,  between  the  two  layers  of  the 
second  mesentery,  along  the  small  mesenteric  artery,  which  it  passes,  and  extends 
to  the  great  mesenteric  artery,  on  the  left  side  of  which  it  unites  with  the  splenic 
vein,  before  opening  into  the  anterior  mesenteric  to  form  the  vena  portfe.  In 
its  course  it  receives  all  the  satellite  venous  branches  of  the  divisions  of  the 
artery  of  the  same  name,  the  arrangement  of  these  being  similar  to  that  of  the 
arterial  ramifications. 

C.  Splenic  Vein  (Fig.  390,  13). — This  is  an  enormous  canal  which 
accompanies  the  splenic  artery,  and  comports  itself  exactly  like  it.  It  begins 
by  the  left  gastro-omental  vein  (Fig.  390,  14)  anastomosing  in  arcade  with  the 


TEE  POSTERIOR    VENA   CAVA. 


707 


Fig.  390. 


right  gastro-omental,  receiving  on  its  track  gastric,  splenic,  and  omental  hranches^ 
and  joining  the  posterior  mesenteric  after  passing  above  the  left  extremity  of 
the  pancreas,  and  obtaining  the  posterior  gastric  vein  (Fig.  390,  16). 

2.  collateeal  affluents  of  the 
Vena  Port^. 

A.  Right  Gastro-omental  or  Gas- 
tro-epiploic  Vein  (Fig.  390,  15).— We 
already  know  that  the  hepatic  artery,  be- 
fore entering  the  liver,  gives  off  pancreatic 
branches,  a  pyloric  branch,  and  a  gastro- 
omental  division,  which  in  turn  detaches 
a  small  duodenal  artery ;  the  vessel  de- 
scribed as  the  right  gastro-omental  vein 
corresponds,  in  every  respect,  to  all  these 
collateral  ramifications  of  the  hepatic  artery. 

This  vein,  then,  has  its  origin  from 
around  the  great  curvature  of  the  stomach, 
but  at  an  undetermined  point,  as  it  forms 
an  anastomotic  arch  with  the  left  gastro- 
omental  vein.  Posteriorly,  it  crosses  the 
dilatation  at  the  origin  of  the  duodenum, 
receives  the  pyloric,  duodenal,  a.nd  pancreatic 
veins,  and  opens  into  the  vena  portJB  after 
traversing  the  pancreas. 

B.  Anterior  Gastric  Vein. — Satel- 
lite of  the  homonymous  artery,  this  vein 
joins  the  vena  portae  separately,  after  the 
entrance  of  that  vessel  into  the  great  pos- 
terior fissure  of  the  liver,  and  when  very 
near  the  terminal  extremity  of  that  fissure.^ 

Renal  Veins. 

Two  in  number,  like  the  arteries  they 
accompany,  these  veins  are  distinguished 
by  their  enormous  volume  and  the  thin- 
ness of  their  walls.  The  left,  having  to 
cross  the  abdominal  aorta  before  entering 
the  vena  cava,  is  longer  than  the  right. 
They  receive  the  majority  of  the  veins  from 
the  supra-renal  capsules  (Fig.  389,  10). 

Spermatic  Veins. 

These  vessels  correspond  to  the  sper- 
matic arteries  in  the  male,  and  the  utero- 
ovarian  arteries  in  the  female. 


the  vena  portie  and  its  roots  (partly 
theoretical). 

1,  Trunk  of  the  vena  poi-tse ;  2,  its  origin; 
3,  veins  of  the  small  intestine ;  4,  ilio- 
caecal  vein ;  5,  external  caecal  vein ;  6, 
internal  coecal  vein;  7,  anterior  mesenteric 
vein ;  8,  9,  colic  veins  forming  the  roots 
of  that  vessel ;  10,  collateral  vein  some- 
times continuing  the  left  colic,  and 
joining  the  anterior  mesenteric  vein  near 
its  origin  ;  11,  common  confluent  of  the 
posterior  mesenteric  and  splenic  veins ; 
12,  posterior  mesenteric  vein  and  its 
collateral  branches;  13,  splenic  vein;  14, 
left  gastro-omental  vein  ;  15,  right  ditto; 
16,  posterior  gastric  vein,  a.  Stomach  ;  b, 
duodenum;  c,  small  intestine;  d,  caecum; 
e,  large  colon;  /,  floating  colon;  g,  rectum; 
h,  portion  of  the  great  omentum ;  i, 
spleen  ;  j,  mesentery  ;  k,  colic  mesentery. 


•  Among  these  collateral  affluents  of  the  vena  portse,  it  is  necessary  to  mention  the  biliary 
veins  which  Claude  Bernard  has  injected  in  the  Dog.  These  vessels,  whicli  correspond  to  the 
hepatic  artery,  pass  from  the  posterior  surface  of  the  liver,  and  open  into  the  portal  vein  at  a 
short  distance  from  th;it  j;l,ind. 


708  TEE   VEINS. 

Testicular  vein. — The  radicles  which  constitute  this  vein  present,  at  their 
emergence  from  the  superior  border  of  the  testicle,  a  flexif orm  and  very  com- 
plicated arrangement,  enlacing,  turning,  and  inflecting  themselves  in  a  thousand 
ways  around  the  convolutions  of  the  great  spermatic  artery,  and  ascending  in 
this  manner  towards  the  neck  of  the  abdominal  ring,  which  they  pass  through, 
usually  after  joining  to  form  two  trunks.  These  rise  towards  the  sublumbar 
region,  beneath  the  peritoneum,  in  a  fold  of  which  they  are  at  first  included ; 
they  communicate  with  one  another  in  their  course  by  anastomosing  branches, 
and  are  generally  united  into  a  single  spermatic  vein,  which  opens  into  the  vena 
cava  near  the  renal  vein  (Fig.  389,  8). 

Utero-ovarian  vein. — This  vein — which  is  very  voluminous — enters  the  vena 
cava  at  the  same  point  as  the  corresponding  vessel  in  the  male,  and  proceeds, 
as  its  name  indicates,  from  the  ovaries  and  uterus  by  flexuous  and  reticular 
branches,  the  fusion  of  which  into  a  single  trunk  only  takes  place  near  the  vena 
cava. 

Lumbar  Veins. 

Satellites  of  the  arteries  of  the  same  name,  these  vessels  enter  the  vena  cava 
separately.     The  most  anterior  often  open  into  the  vena  azygos. 

Common  Iliac  Veins. 

This  appellation  is  given  to  two  enormous  vessels,  into  which  are  collected 
all  the  veins  of  the  abdominal  limb  and  the  posterior  part  of  the  trunk — very 
short  vessels,  that,  by  their  junction,  form  the  posterior  vena  cava  (Fig.  389, 
3,  4). 

The  common  iliac  vein  is  lodged  in  the  angle  of  separation  comprised  between 
the  external  and  internal  iliac  arteries,  and  is  a  continuation  of  the  two  satellite 
veins  of  these  vessels.  The  right — shorter  than  the  other — passes  above  the 
external  iliac  artery  to  join  the  vena  cava  at  its  origin.  The  left — longer — 
insinuates  itself  between  the  body  of  the  second  last  lumbar  vertebra  and  the 
terminal  extremity  of  the  posterior  aorta,  to  open  into  the  other. 

If  we  trace — as  was  done  with  the  veins  of  the  anterior  extremity — from  the 
ungual  region  to  the  pelvis,  all  the  branches  which  concur  in  the  formation  of 
these  two  trunks,  we  shall  find,  as  the  common  point  of  departure  for  each,  a  rich 
subungual,  plexus,  from  which  spring  two  digital  veins.  To  these  succeed  three 
metatarsal  veins,  the  common  origin  of  all  the  vessels  of  the  leg.  These  latter 
are  distinguished  as  superficial  and  deep,  and  are  four  in  number — -two  saphena 
veins  in  the  first  group,  and  two  tibial  veins  in  the  second — continued  by  the 
poplitecd  vein.  This  vessel  is  itself  continued  by  the  femorcd  and  extermd  iliac 
veins,  which  finally  form  the  common  iliac,  by  opening  into  the  interned  diac  vein. 

All  these  vessels  will  be  studied  in  an  inverse  order  to  that  in  which  they 
have  been  enumerated,  and  as  follows  : — 

1.  Internal  iliac  vein. 

2.  Extermd  iliac  vein. 

3.  Femorcd  vein. 

4.  Poplitecd  vein. 

5.  Deep  veins  of  the  leg. 

6.  Superficial  veins  of  the  leg. 

7.  Metatarsal  veins. 

8.  Veins  of  the  digital  region. 


THE  POSTERIOR    VENA   CAVA.  709 


1.  Internal  Iliac  Vein. 


This  vessel  is  formed  by  the  satellite  veins  of  the  branches  furnished  by 
the  homonymous  artery  :  these  are  the  iliaco-femoral,  obturator,  iUaco-muscuIar, 
gluteal,  lateral  sacral,  and  internal  pudic,  the  distribution  of  which  does  not  differ 
from  that  of  the  corresponding  arterial  divisions. 

The  trunk  resulting  from  the  union  of  these  different  branches  is  usually 
very  short ;  it  may  even  be  altogether  absent,  and  we  then  see  the  veins  which 
should  form  it,  open  into  the  common  ihac  vein  by  forming  two  or  three  separate 
groups,  situated  very  close  to  each  other. 

2.  External  Iliac  Vein. 

This  vein  constitutes  the  principal  root  of  the  common  iliac,  which  is  but 
a  continuation  of  it — the  internal  iliac  being  only,  properly  speaking,  a  collateral 
affluent  of  the  single  canal  represented  by  the  external  and  common  iliac  veins. 

Situated  behind  the  iliac  artery,  this  external  iliac  vein  commences  at  the 
anterior  border  of  the  pubis,  where  it  is  directly  continued,  without  any  line  of 
demarcation,  liy  the  femoral  vein. 

The  only  important  vessel  it  receives  on  its  course  is  the  iliac  circumflex  vein, 
which,  however,  opens  more  frequently  into  the  common  than  the  external  iliac. 

3.  Femoral  Vein. 

Continuous  by  its  superior  extremity  with  the  external  iliac  vein,  and 
inferiorly  with  the  popliteal,  the  femoral  vein  is  remarkable  for  its  large  volume  ; 
it  closely  follows  the  artery  of  the  same  name  throughout  its  extent  (Fig. 
389,  5). 

The  collateral  affluents  it  receives  in  its  course  are  distinguished  by  their 
number  and  considerable  volume.     They  are  : — • 

1.  The  satellite  veins  of  the  miiscidar  arteries. 

2.  The  internal  saphena  vein,  which  will  be  again  referred  to  in  describing 
the  superficial  veins  of  the  leg. 

3.  The  preiyubic  vein,  formed  by  the  posterior  ahdominal  and  the  branches  of 
the  internal  piidic.  The  latter  are  very  numerous  and  large,  and  anastomose 
with  each  other,  forming  between  the  thighs,  in  the  texture  of  the  scrotum  and 
sheath,  and  above  the  penis,  a  very  rich  network  which  communicates  behind 
with  the  cavernous  veins.  This  network  only  sends  a  small  trunk  into  the 
inguinal  canal,  along  the  external  pudic  artery  ;  in  its  middle  part  it  opens  into 
an  enormous  branch  which  passes  through  the  ring  in  the  sartorius  muscle,  and 
is  lodged  in  the  inferior  groove  of  the  pubis  to  join  the  femoral  vein. 

One  of  these  external  pudic  veins  represents  the  subcutaneous  abdominal 
vein,  and  communicates  with  the  subcutaneous  thoracic  vein. 

All  these  branches  in  the  female  show  an  analogous  disposition. 

4.  Popliteal  Vein. 

Satellite  of  the  -popliteal  artery,  this  vein  is  formed  by  the  union  of  the 
anterior  and  posterior  tibial  veins. 

Among  the  branches  it  receives  on  its  course,  the  femoro-popliteal  vein  may  be 
particularly  noted  ;  this  accompanies  the  artery  of  the  same  name,  and  joins  the 
external  saphena  before  opening  into  the  popliteal  vein. 


710  TEE   VEINS. 

5.  Deep  Veins  of  the  Leg. 

These  are  two  in  number  :  the  anterior  and  posterior  tibial. 

A.  Anterior  Tibial  Vein. — Placed  beside  the  homonymous  artery,  often 
double,  always  very  ample,  this  vein  originates  on  the  anterior  face  of  the  tarsal 
articulations  by  means  of  several  anastomosing  roots,  the  principal  of  which  is 
formed  by  the  deep  metatarsal  vein,  that  passes  through  the  cuboido-cuneo- 
scaphoid  canal  from  behind  to  before.  After  crossing  the  fibular  arch  with  the 
artery,  it  joins  the  posterior  tibial  to  constitute  the  popliteal  vein. 

B.  Posterior  Tibial  Vein. — This  commences  near  the  hollow  of  the  hock, 
in  front  of  the  calcis,  by  radicles  which  principally  come  from  the  two  saphena 
veins.  It  then  ascends  along  its  satellite  artery,  to  open  into  the  anterior  vein 
beneath  the  popliteal  muscle. 

6.  SuPEEFiciAL  Veins  of  the  Leg. 

These  are  the  internal  and  external  saphena. 

A.  Internal  Saphena  Vein. — This  vessel  shows  two  roots — an  anterior 
and  posterior  (Fig.  389,  39,  40). 

The  first  proceeds  from  the  internal  metatarsal  vein,  the  second  from  the 
external.  Both  ascend,  in  converging  towards  each  other,  on  the  internal  face 
of  the  tibia,  uniting  into  a  single  branch  before  reaching  the  thigh. 

This  single  branch — always  very  voluminous — glides  upwards  on  the  sartorius 
muscle,  and  terminates  in  a  variable  manner  on  reaching  the  groin  :  sometimes 
it  is  insinuated  into  the  interstice  between  the  gracilis  and  sartorius,  to  join  the 
femoral  vein,  and  at  other  times  it  ascends  to  the  ring  of  the  gracilis,  to  open 
into  the  external  pudic  veins. 

B.  External  Saphena  Vein. — It  rises,  by  a  short  branch,  outside  the  os 
calcis,  communicates,  even  at  its  origin,  with  the  posterior  root  of  the  internal 
saphena  by  means  of  a  large  reticular  anastomosis  thrown  transversely  in  front 
of  the  apex  of  the  calcis  ;  and  with  the  posterior  tibial,  by  a  large  branch  that 
passes  between  the  tibia  and  the  flexor  pedis  perforans  muscle.  It  follows  the 
external  saphena  nerve  outside  the  gastrocnemius  tendon,  behind  the  external 
head  of  the  gastrocnemius  muscle,  and  enters  the  popliteal  vein,  after  joining  the 
femoro-popliteal  vessel. 

7.  Metataesal  Veins. 

These  veins  are  three  in  number,  and  are  distinguished  as  internaL  external^ 
and  deep ;  they  proceed  from  the  sesamoidean  arch,  which  is  formed  by  the 
anastomosis  of  the  two  digital  veins. 

A.  Internal  Metatarsal  Vein. — This  vessel,  the  most  considerable  of  the 
three,  appears  more  particularly  to  continue  the  digital  vein  of  the  same  side. 
For  the  greater  part  of  its  extent  it  is  placed  with  the  internal  plantar  nerve, 
along,  and  a  little  in  advance  of,  the  flexor  tendons.  Arriving  near  the  tarsus, 
it  deviates  slightly  to  reach  the  anterior  face  of  the  tarsal  articulations,  and 
there  communicates — by  a  very  large  transverse  branch — with  the  origin  of  the 
anterior  tibial  vein  ;  afterwards  it  rises  on  the  internal  face  of  the  leg,  where  it 
constitutes  the  anterior  radicle  of  the  internal  saphena  vein. 

B.  External  Metatarsal  Vein. — It  occupies,  outside  the  flexor  tendons,  a 
position   analogous  to  the  preceding.     Towards  the  superior  extremity  of  the 


THE  POSTERIOR    VENA    CAVA.  711 

metatarsus,  it  communicates,  by  a  short,  thick  branch,  with  the  deep  vein.  It 
then  continues  its  ascending  course  by  entering  the  tarsal  sheath  along  with  the 
plantar  arteries,  and  is  prolonged  in  the  hollow  of  the  hock,  passing  along  the 
femoro-popliteal  nerve,  forming  the  posterior  root  of  the  internal  saphena. 

C.  Deep  Metatarsal  Vein. — This  is  placed  beneath  the  suspensory  liga- 
ment, at  the  inner  side  of  the  principal  interosseous  plantar  artery.  Near  the 
tarsus,  it  receives  a  very  large  branch  from  the  external  vein,  and  then  passes 
through  the  cuboido-cuneo-scaphoid  canal,  to  form  the  largest  root  of  the  anterior 
tibial  vein. 

8.  Veins  of  the  Digital  Region. 

As  these  resemble,  in  every  respect,  those  belonging  to  the  anterior  limb,  the 
same  description  will  suffice  for  both  (see  p.  698). 

Differential  Characters  in  the  Veins  of  the  other  Animals. 
It  does  not  come  within  our  plan  to  give  a  complete  description  of  the  venous  system  in 
these  animals,  because  of  the  small  utility  of  such  a  study.  To  remain  faithful  to  our  object, 
we  confine  ourselves  to  tlie  indication  of  the  special  characters  of  the  veins  on  which 
bleeding  is  usually  practised,  and  those  which  may  be  interesting  in  a  surgical  point  of  view — 
such  as  tlie  digital  veins  of  Ruminants. 

A.  Angular  Vein  of  the  Eye. — This  vessel  is  remarkable  for  its  large  volume  in  the 
Sheep ;  and  as  it  is  well  defined  beneath  the  skin,  in  consequence  of  the  fineness  of  that 
meml>rane,  it  is  more  frequently  selected  for  phlebotomy  than  in  other  animals. 

B.  Jugular  Vein. — Very  large  in  all  animals,  and  particularly  in  the  Ox,  this  vein 
deserves  the  preference  given  to  it  when  it  is  proposed  to  abstract  a  certain  quantity  of  blood 
from  the  system. 

In  all  non-soliped  animals  there  is  found  an  accessory  jugular,  which  sometimes  exists  in 
tlie  Horse — but  is  much  less  in  size — alongside  the  common  carotid  artery.  It  arises  from  the 
occipital  vein,  and  therefore  extends  the  whole  length  of  the  neck.  Sometimes  its  diameter 
is  small;  but  it  is  often  so  large  as  to  receive  a  very  notable  quantity  of  blood  from  the 
principal  jugular,  when  compression  is  applied  to  the  latter  to  favour  the  flow  of  blood  after 
opening  it — a  circumstance  that  explains  the  difliculty  sometimes  experienced  in  obtaining  a 
voluminous  jet  of  blood. 

C.  Abdominal  Subcutaneous  Vein.— In  the  Bovine  species,  this  vessel  has  an  enor- 
mous volume,  especially  in  the  Milch-cow,  in  contradistinction  to  the  subcutaneous  thoracic 
vein,  which  is  always  very  small. 

This  vein  is  prolonged  forward  on  the  wall  of  the  abdomen,  to  near  the  xiphoid  cartilage, 
where  it  passes  through  to  join  the  internal  thoracic  vein.'  Behind,  it  is  formed  by  multiple 
branches,  which  anastomose  with  each  other,  or  with  those  of  the  opposite  vein,  and  are  in 
communication  with  the  proper  external  pudic  veins. 

D.  Internal  Saphena  Vein. — This  is  always  smaller  than  in  Solipeds,  and  is  rarely 
selected  to  extract  blood_from. 

E.  External  Saphena  Vein.— This  vessel  is,  on  the  contrary,  more  voluminous  than  in 
the  Horse,  and  at  the  same  time  more  superficial ;  consequently,  it  is  more  favourably  situated 
for  phlebotomy,  as  well  in  Pigs  and  the  Carnivora,  as  in  Ruminants.  It  arises  from  the  union, 
in  the  hollow  of  the  hock,  of  the  two  principal  roots  furnished  by  the  metatarsal  veins. 

F.  Veins  of  the  Posterior  Foot  in  the  Ox. — As  in  the  Horse,  they  commence  in  the 
subungual  network  of  the  digital  region,  which  is  double,  like  the  region  itself. 

a.  Three  digital  veins  leave  this  reticulum :  1.  A  median  or  anterior  one,  arising  by  two 
roots  from  the  anterior  part  of  each  network,  passing  between  the  two  digits,  and  joining  the 
anterior  .superficial  metatarsal  vein  above  the  fetlock.  2.  Two  laterals,  communicating  with 
one  another,  behind,  by  a  transverse  anastomosis  which  receives  several  venules  from  the 
ungual  plexus,  and  with  the  anterior  vein  by  an  iuterdigital  branch,  united  by  an  arch  in  front 
of  the  flexor  tendons,  above  the  sesamoid  groove. 

b.  These  digital  veins  are  continued  by  five  metatarsal  veins :  two  deep  and  one  superficial 
anterior,  and  two  posterior. 

'  The  openings  through  which  these  vessels  pass  in  the  abdominal  parietes,  are  commonly 
named  the  milk  fountains  or  doors. 


712  THE  VEINS. 

The  two  deep  anterior  veins  are  small  vessels  which  accompany  the  collateral  artery  of  the 
cannon,  wliich  is  placed  between  them.  They  arise  in  the  interdigital  space  from  the  anterior 
digital  vein,  communicating,  by  the  inferior  metatarsal  foramen,  with  the  sesamoid  arch, 
sending  off  on  their  way  transverse  anastomoses,  and  being  continued  above  the  tarsus  by  the 
two  anterior  tibial  veins,  whose  roots  they  constitute. 

The  anterior  superficial  vein  is  very  voluminous.  It  proceeds  from  the  sesamoid  arch, 
receives  near  its  origin  the  middle  digital  vein,  rises  in  front  of,  and  a  little  to  the  outside  of, 
the  tarsus,  communicating  at  this  point  with  the  anterior  tibial  veins ;  it  divides  above  the 
tibio- tarsal  articulation  into  two  branches :  a  posterior,  forming  the  anterior  root  of  the  external 
saphena  ;  the  other  anterior,  joining  the  anterior  tibial  vein  of  tlie  external  side. 

The  two  posterior  veins  spring  from  the  sesamoid  arch.  Situated  at  first  between  the  sus- 
pensory ligament  of  the  fetlock  and  the  posterior  face  of  tiie  metatarsus,  and  communicating 
there  by  several  anastomoses,  tiiese  two  veins  are  continued  along  the  tarsus — the  one  within, 
the  other  without.  The  internal  follows  the  corresponding  plantar  artery,  and  is  prolonged  in 
the  tibial  region  by  tlie  posterior  tibial  and  internal  saphena  veins.  The  external  ascends 
within  the  calcis,  and  is  united  to  a  branch  of  the  anterior  superficial  metatarsal,  to  form  the 
external  saphena  vein.  Before  leaving  the  deep  situation  they  occupy  below  tlie  suspensory 
ligament  of  the  fetlock,  these  two  vessels — but  especially  the  internal — concur  to  form  a  perfo- 
rating branch  which  traverses  the  cuboido-scaphoid  canal  to  join  the  anterior  tibial  veins. 

G.  Veins  of  the  Anterior  Foot  in  the  Ox. — Four  digital  veins  escape  from  the  two 
subungual  plexuses :  an  anterior,  posterior,  and  two  lateral. 

a.  The  anterior  digital  vein,  which  is  very  slender,  is  lodged  superficially  between  the 
two  digits,  and  comports  itself  at  its  origin  like  the  analogous  vein  of  the  posterior  limb,  in 
rising  by  two  roots.  In  being  prolonged  above  the  fetlock,  it  constitutes  a  subcutaneous  meta- 
carpal brand),  which  occupies  the  anterior  and  internal  plane  of  the  cannon,  and  is  united 
above  the  knee  to  the  principal  cutaneous  vein  of  the  forearm. 

b.  The  posterior  digital  vein — often  doubled  by  a  small  accessory  branch — accompanies  the 
common  digital  artery,  and  extends  along  the  collateral  artery  of  the  cannon,  to  constitute  one 
of  the  posterior  radial  veins. 

c.  The  internal  digital  vein,  after  passing  the  digital  region,  is  lodged  between  the  cannon 
bone  and  tlie  internal  border  of  the  suspensory  ligament,  proceeds  outside  the  carpal  sheath 
■with  the  radio-palmar  artery,  and  divides  above  the  knee  into  two  branches— an  anterior,  the 
origin  of  the  internal  subcutaneous  vein  of  the  forearm;  the  other  posterior,  forming  one  of 
the  posterior  radial  veins. 

d.  The  external  digital  vein  occupies,  on  the  outer  side  of  the  external  digit  and  the  cannon 
bone,  a  po.-ition  analogous  to  the  internal  vein.  It  gives  rise  to  several  deep  metacarpal  veins 
which  anastomose,  and  are  mixed  with  the  interosseous  palmar  arteries;  the  principal  vein  and 
its  accessory  branches  are  joined,  below  the  carpus,  to  the  internal  vein. 

It  is  to  be  remarked  that  these  four  digital  veins  communicate,  in  the  interdigital  space, 
by  anastomoses  resembling  those  of  the  posterior  limb;  and  that  the  last  three,  or  principal 
veins,  anastomose  above  the  fetlock  in  forming  a  complicated  and  variably  arranged  sesamoid 
arch,  on  leaving  which  these  digital  veins  become  metacarpal  vessels. 

Comparison  of  the  Veins  in  Man  with  those  of  Animals. 

In  Man,  as  in  animals,  the  veins  are  grouped  into  those  of  the  lesser  circulation — m  pul- 
monary veins— and  those  of  the  greater  circulation.  The  latter  open*  into  the  heart  by  three 
trunks— the  cardiac  veins,  and  superior  and  inferior  vena  cava. 

The  superior  vena  cava  represents  the  anteri<jr  vena  cava  of  animals,  and  receives  the  blood 
from  the  veins  of  the  head,  thoracic  limbs,  and  a  portion  of  the  chest.  It  extends  from  the 
first  costal  cartilage  to  the  heart,  and  commences  after  the  junction  of  the  two  brachio- 
cephalic trunks  or  innominate  veins. 

The  superficial  veins  of  the  thoracic  limb  at  first  form,  on  the  back  of  the  hand,  a  plexus 
of  elongated  meshes  from  which  the  median,  radial,  and  ulnar  veins  spring.  Near  the  bend  of 
the  elbow,  the  median  bifurcates  and  gives  rise  to  the  median  ce^ihalic  and  median  basilic. 
Blood  is  abstracted  from  one  or  other  of  these  branches.  At  the  arm,  all  the  superficial  veins 
constitute  but  two  trunjcs — the  cephalic  and  basilic  veins.  The  deep  vessels  join  these  to  form 
the  axillary  vein,  which  becomes  the  subclavian  below  the  clavicle,  then  the  brachio-cephalic 
trimk  (vena  innomlnata)  when  it  receives  the  internal  jugular. 

The  venous  sinuses  of  the  cranial  dura  mater  are  proportionately  more  developed  than  in 
Solipeds,  though  they  have  the  same  arrangement.  There  is  constantly  present  a  middle  or 
inferior  longitudinal  sinus. 

The  jugulars,  which  carry  the  blood  from  the  cranium  and  face  to  the  heart,  are  four  in 


THE  LYMPHATICS.  713 

number.  The  anterior  jugular — the  smallest — descends  beneath  the  superficial  cervical  aponeu- 
rosis, in  front  of  the  sterno-mastoideus  muscle,  and  enters  the  subclavian  vein.  The  external 
jugular  commences  by  the  union  of  the  facial  and  temporal  veins ;  in  its  disposition  it  resembles 
the  jugular  of  the  Horse,  and  would  be  a  complete  representative  if  deprived  of  the  branches 
from  the  cranial  sinuses.  The  internal  jugular  arises  at  the  posterior  foramen  lacerum,  at  a 
dilatation  of  the  lateral  sinus  named  the  bulbus  venoe  jugularis,  and  passes  to  the  subclavian 
vein.  Lastly,  the  posterior  jugular  (or  vertebral  vein)  situated  beneath  the  complexus  muscle, 
and  in  relation  with  the  cervical  vertebrae,  carries  the  blood  from  the  spinal  sinuses  in  this 
region,  and  which,  in  Solipeds,  is  received  by  the  occipital  and  vertebral  veins. 

The  inferior  vena  cava  corresponds  to  the  posterior  vena  cava  of  animals,  and  receives  the 
blood  from  all  the  sub-diaphragmatic  veins.  It  originates  from  the  union  of  the  two  common 
iliac  veins,  at  the  third  lumbar  articulation,  and  terminates  in  the  right  auricle.  In  its  course 
it  receives  the  median  sacral,  lumbar,  renal,  supra-renal,  inferior  phrenic,  and  right  spermatic 
veins.  The  latter  forms  on  the  surface  of  the  testicle,  and  at  the  origin  of  the  cord,  a  rich 
network — the  spermatic  plexus;  on  the  abdominal  portion  of  the  cord  it  constitutes  the 
pampiniform  plexus. 

The  vena  cava  also  receives  the  vena  portce,  which  has  the  same  disposition  as  in  animals. 
It  begins  by  three  branches — the  great  and  small  mesenteric  and  splenic  veins.  For  affluents, 
it  has  the  pancreatic  and  duodenal  venules,  and  the  right  gastro-omental  vein.  It  passes 
behind  the  pancreas,  and  not  through  that  gland,  as  in  the  Horse. 

The  veins  of  the  abdominal  limb  are  divided  into  deep  and  superficial.  The  first  terminate 
by  forming  the  femoral  vein,  which,  in  joining  the  vessels  of  the  pelvis,  constitutes  the  common 
iliac  vein.  The  superficial  veins  commence  by  a  network  on  the  dorsum  of  the  foot,  which 
gives  origin  to  the  two  saphenas— external  and  internal. 


FOURTH   SECTION. 
THE    LYMPHATICS. 

CHAPTER  I. 

General  Considerations. 

Charged  with  the  absorption  and  transport  of  the  chyle  and  lymph,  the 
lymphatic  or  absorbent  vessels  are  convergent  canals  with  thin  and  transparent 
walls,  which  originate  in  the  texture  of  organs  by  fine  reticulated  radicles  ;  these, 
after  passing  through  one  or  more  glands — glandiform  bodies  placed  on  their 
course — enter  the  venous  system  by  two  trunks — the  thoracic  duct  and  the  great 
lymphatic  vein. 

Lymphatic  Vessels. 

These  vessels  resemble  veins  in  so  many  points,  as  to  merit  the  name  of  ivhite- 
blood  veins.  Like  these  vessels,  the  lymphatics  are  directed  from  the  periphery 
to  the  centre  of  the  circulatory  apparatus  ;  hke  them,  they  are  nodulated  cylin- 
drical tubes  ;  internally,  and  at  those  points  where  they  outwardly  appear  to 
be  constricted,  they  show  numerous  valves  which  look  towards  the  heart.  Like 
the  veins,  again,  they  separate  into  two  orders  of  canals — the  ones  deep-seated, 
lodged  in  the  vasculo-nervous  intermuscular  sheaths  ;  the  others  superficial, 
situated  on  the  surface  of  containing  aponeuroses.  Like  the  veins,  also,  the 
lymphatics  terminate  in  two  principal  trunks  resembling  the  venas  cavEe ;  and, 


714  THE  LYMPHATICS. 

finally,  as  the  veins  have  three  tunics,  so  have  the  lymphatics,  these  not  differing 
in  any  respect,  except  in  being  very  much  thinner. 

If  we  pass  into  the  domain  of  physiology,  it  is  also  easy  to  observe  characters 
which  are  common  to  the  two  anatomical  systems  under  comparison.  They,  in 
fact,  almost  equally  divide  the  absorbent  function  between  them — a  function 
which  is  accomplished  in  the  radicular  network  of  each  ;  and  the  dynamical 
process  which  gives  impulsion  to  the  fluids  they  carry,  if  it  is  not  quite  identical 
in  both,  is  at  any  rate  very  similar  in  many  points. 

We  may,  nevertheless,  observe  numerous  differences  between  the  veins  and 
the  lymphatics,  and  chiefly  in  their  form,  number,  capacity,  and  structure. 

The  form  of  the  lymphatic  canals  is,  as  we  have  said,  nodulated  and  cylin- 
drical ;  but  their  nodosities  are  much  less  marked,  and  are  closer  together  than 
in  the  veins,  owing  to  the  larger  number  and  greater  development  of  the  valves. 
Besides,  as  these  vessels  proceed  for  considerable  distances,  and  preserve  their 
regularly  cylindrical  form  with  undiminished  capacity,  if  we  mentally  bring  all 
the  divisions  of  the  lymphatic  system  to  a  single  canal,  we  no  longer  have  a 
hollow  cone  the  apex  of  which  corresponds  with  the  heart — although  the  capacity 
of  the  lymphatic  vessels  augments  from  the  trunk  towards  the  branches  ;  for 
this  canal  only  represents  a  series  of  cylinders  joined  end  to  end,  and  successively 
decreasing  from  its  origin  to  its  termination. 

The  number  of  lymphatic  vessels  in  a  certain  region  is  always  much  greater 
than  that  of  the  veins.     But  as  the  lymphatics  are  much  smaller  than  the  veins, 


Fig.   391. 


A    LYMPHATIC    VESSEL   WITH    ITS   VALVES. 

there  is  not,  as  might  at  first  be  supposed,  a  proportional  increase  in  their  total 
capacity.  Observation,  indeed,  demonstrates  that  the  relation  between  the 
capacity  of  the  lymphatics  and  the  corresponding  veins  of  a  region  does  not 
exceed  one  to  two. 

The  structure  of  the  lymphatics  differs  from  that  of  veins,  in  that  there  exists, 
in  those  of  average  dimensions,  smooth  muscular  fibres  in  the  adventitious  tunic. 
The  presence  of  muscular  fibres  in  the  external  tunic  of  these  vessels  is  rendered 
necessary  by  the  absence  of  an  impelling  organ  at  the  origin  of  the  lymphatic 
system — such  an  organ  being,  in  reality,  disseminated  throughout  the  extent  of 
the  vessels,  and  aids  the  vis  a  tergo  that  causes  tiie  lymph  to  cu'culate  in  their 
interior. 

We  terminate  this  short  parallel,  to  notice  in  detail  several  points  connected 
with  the  general  history  of  the  lymphatics,  and  which  merit  particular  attention  ; 
we  allude  to  the  origin,  course,  and  termination  of  these  vessels. 

Origin. — For  a  long  period  after  the  discovery  of  the  lymphatic  vessels,  a 
state  of  profound  ignorance  existed  as  to  their  origin.  Nevertheless,  the 
importance  of  the  solution  of  the  problem  was  well  appreciated,  as  it  was  really 
the  key  to  the  theory  of  absorption  ;  numerous  hypotheses,  therefore,  sprang 
into  existence.  The  anatomists  who  occupied  themselves  with  the  question, 
were  hindered  in  their  investigation  by  the  imperfect  means  of  research  at  their 
disposal.     Beyond  the  larger  branches,  the  lymphatics  escaped  attention,  owing 


THE  LYMPHATICS.  715 

to  their  transparency  and  tenuity.  Thanks,  however,  to  the  patient  and  minute 
researches  of  Hunter,  Cruikshank,  Mascagni,  Fohmann,  Panizza,  Cruveilhier, 
and  Sappey,  the  lymphatics  were  injected  by  colouring  matters  or  by  mercury, 
and  thus  rendered  visible  to  their  finest  ramifications. 

It  is  now  known  that  the  lymphatics  arise  from  ccqnllaries,  which  form  net- 
works or  terminal  culs-de-sac. 

These  terminal  culs-de-sac  exist  in  the  intestinal  villi ;  and  it  is  no  longer 
maintained  that  the  ends  of  these  small  appendages  have  an  opening  by  which 
the  lymphatic  vessels  receive  the  chyle  that  bathes  the  mucous  membrane  of  the 
intestine. 

The  plexuses  are  composed  of  more  or  less  irregular  meshes,  and  their  form 
and  volume  often  vary  with  the  arrangement  of  the  tissues  or  organs  in  which 
they  are  studied.  They  may  be  superficial  or  deep,  and  exist  together  or  sepa- 
rately. In  many  membranes  the  two  networks  are  found,  but  then  the  superficial 
is  thinner  than  the  deep.  They  are  mixed  with,  or  placed  above,  the  blood-vessel 
plexuses,  but  never  communicate  with  them. 

Do  these  lymphatic  plexuses  exist  in  all  the  tissues,  properly  speaking  ?  Here 
is  another  question  of  incontestible  importance,  the  solution  of  which  for  a 
long  time  occupied  the  attention  of  anatomists.  Judging  by  analogies,  one  is 
tempted  to  reply  in  the  affirmative — why,  in  fact,  should  the  lymphatics  not 
«xist  everywhere  throughout  the  organism,  when  the  blood-capillaries  are  con- 
stituent parts  of  the  framework  of  each  tissue  ?  Nevertheless,  direct  observa- 
tion has  not  revealed  lymphatic  plexuses  in  all  organs  ;  there  are  even  tissues  in 
which  theii-  existence  has  been  absolutely  denied — though  prematurely,  it  is  well 
to  say,  because  we  may  always  ascribe  the  non-success  of  a  lymphatic  injection 
either  to  the  imperfection  of  the  instruments  employed,  the  insufficiency  of  the 
measures  adopted,  or  to  certain  peculiar  conditions  as  yet  unknown  and  attach- 
ing to  the  species  of  animals  selected  for  the  demonstration  of  the  lymphatic 
networks  in  a  certain  region.  In  support  of  this  last  assertion,  we  may  observe 
that  Sappey  has  not  yet  been  able  to  inject  the  pituitary  plexuses  in  Man  or  the 
Calf,  and  that  he  looks  upon  their  existence  as  being  at  least  doubtful ;  while 
in  the  Horse,  this  lymphatic  apparatus  is  as  remarkable  for  its  richness,  as  for 
the  facility  with  which  it  may  be  filled  with  mercury. 

It  may  be  asserted  that  they  do  not  exist  in  the  epidermis,  or  in  epithelial 
layers. 

The  following  are  the  most  trustworthy  notions  available  on  this  subject. 

The  lymphatic  vessels  of  the  sMn  are  very  numerous,  and  form  two  networks  : 
one,  with  extremely  fine  meshes,  occupies  the  most  superficial  layer  of  the  dermis  ; 
the  other,  placed  beneath  the  deep  face  of  the  integument,  includes  vessels  more 
voluminous  than  the  first,  and  communicates  with  it  by  multiple  ramuscules. 
These  lymphatic  plexuses  are  far  from  being  equally  developed  in  every  region, 
though  it  is  unanimously  agreed  that  no  part  is  entirely  destitute  of  them. 

In  the  mucous  membranes,  an  analogous  arrangement  of  these  vessels  is  met 
with.  It  is  more  than  probable  that  they  exist  throughout  the  whole  extent  of 
these  membranes,  though  their  positive  demonstration  has  yet  to  be  made  in 
some  regions.  In  other  regions,  the  injection  of  these  networks  is,  on  the 
contrary,  very  easy,  and  gives  the  most  magnificent  results  ;  we  particularly 
mention  the  lingual,  intestinal,  and  pituitary  mucous  membranes.  The 
lymphatics  belonging  to  the  latter  membrane  assume  so  beautiful  an  aspect 
in  the  Horse,  that  we  would  advise  anatomists  who  desire  to  inject  lymphatics 


716  THE  LYMPHATICS. 

always  to  choose  that  animal.  The  operation  is  simple  and  always  successful, 
and  we  are  astonished  that  in  the  hands  of  some  mdividuals  it  should  fail.  Not 
only  can  the  two  networks  of  the  membrane  be  filled,  but  also  the  trunks 
arisin<i:  from  them,  and  which  are  directed  towards  the  entrance  of  the  nasal 
cavities,  collect  in  several  thick  branches  around  the  nostril,  and  curve  up 
towards  the  face  to  reach  the  submaxillary  space,  where  they  enter  the  glands 
situated  to  the  right  and  left  of  that  region. 

The  majority  of  anatomists  admit  the  presence  of  lymphatic  plexuses  in  the 
splanchnic  or  synovicil  serous  memhranes.  Sappey,  however,  denies  this  ;  he  con- 
siders the  vessels  that  can  be  so  easily  injected  by  pricking  the  external  surface 
of  a  viscus,  as  belonging  to  its  proper  tissue,  and  not  to  the  serous  membrane 
covering  it.  Those  on  the  inner  face  of  the  walls  of  the  splanchnic  or  synovial 
cavities,  and  which  are  sometimes  filled  with  mercury,  do  not,  according  to  him, 
come  from  the  serous  tunic,  but  from  the  subjacent  tissues. 

The  lymphatics  do  not  exist  in  vessels.  The  lymphatic  sheaths  discovered  by 
His,  Robin,  and  Tomaso,  around  the  blood-capillaries  of  the  Frog,  and  those 
of  the  brain  and  spleen  of  Man,  and  recognized  by  Rusconi,  Milne-Edwards,  as 
well  as  demonstrated  by  Ranvier  around  the  vessels  of  the  mesentery,  ought  not 
to  be  considered  as  the  lymphatics  of  vessels  ;  they  merely  surround  the  ultimate 
vascular  ramifications,  and  do  not  arise  in  the  substance  of  their  walls. 

In  the  nerve  tissue  lymphatics  have  not  been  discovered,  though  they  are 
present  in  the  meninges. 

Their  existence  is  doubtful  in  hone  tissue  and  in  the  muscles ;  but  they  are 
abundant  in  the  glands  and  glandiform  organs  of  the  animal  economy,  forming 
the  finest,  richest,  and  most  easily  demonstrated  plexuses,  Sappey  admits  that 
they  are  exceeded  by  smaller  capillary  networks  and  spaces. 

It  has  been  stated  above  that  the  lymphatics  commence  by  capillaries  arranged 
in  networks.  Are  these  networks  the  real,  or  only  the  apparent  origin  of  the 
lymphatics  ?  This  is  a  question  that  has  been,  and  is  still,  warmly  discussed. 
It  is,  however,  believed  that  the  plexuses  are  fed  by  very  minute  radicles  lodged 
in  the  substance  of  the  tissues. 

But  how  do  these  radicles  originate  ?  In  the  epithelium,  says  Kiiss  ;  in  the 
plasmatic  cells  of  the  connective  tissue,  asserts  Virchow  ;  in  the  serous  membranes, 
states  Recklinghausen,  since  he  observed  fatty  matters  penetrate  the  lymphatics 
by  the  abdominal  surface  of  the  diaphragm.  The  opinion  of  Yirchow  is  upset 
at  present  by  the  researches  of  Ranvier,  which  have  modified  the  descriptions 
given  of  the  connective  tissue.  According  to  this  authority,  plasmatic  cells  do 
not  exist  in  that  tissue  ;  and  what  have  been  described  as  such  by  Virchow,  have 
been  only  radiating  spaces  hmited  by  the  fascicuh  of  connective-tissue  fibres,  in 
which  elements  analogous  to  lymph  corpuscles  circulate.  The  researches  of 
Ranvier  tend  to  support  the  hypothesis  of  Recklinghausen,  and  show  that  in  the 
connective  tissue  of  the  economy  there  is  an  infinite  number  of  minute  serous 
cavities  into  which  the  lymphatic  vessels  open,  in  which  the  lymph  circulates, 
and  which  are  in  communication,  on  the  other  hand,  with  the  great  splanchnic 
cavities. 

Course  of  the  Lymphatic  Vessels. — The  lymphatics  follow  the  course 
of  the  veins,  and  are  divided,  exactly  like  them,  into  superficial  and  deep  vessels. 
The  latter,  running  parallel  to  each  other,  are  grouped  immediately  around  the 
corresponding  veins,  on  which  they  generally  lie.  The  first,  although  situated 
in   proximity  to  the  superficial  veins,  are  widely  spread  on  each  side  and  on 


TEE  LYMPHATICS. 


717 


the  surface  of  the  superficial  aponeuroses,  in  forming  parallel  fasciculi,  like  the 
deep  lymphatics. 

The  direction  followed  by  the  lymphatics  m  their  course,  is  nearly  always 
somewhat  rectilinear  ;  they  never  show  the  flexuosities  which  are  so  marked 
in  the  course  of  certain  arteries,  and  even  some  veins.  Neither  do  they  com^ 
municate  with  one  another  by  transverse  or  arching  anastomoses,  Uke  those  so 
commonly  met  with  in  the  other  two  orders  of  vessels  belonging  to  the  circulatory 
apparatus.  They  frequently,  however,  in  their  parallel  course,  bifurcate  and 
join  the  neighbouring  vessels.  (At  certain  situations— as  at  some  of  the  articula- 
tions, and  in  other  parts — the  larger  trunks  suddenly  break  up  into  a  close 
interlacing  plexus  of  small  vessels  or  capillaries — Fig.  392 — which  in  their 
arrangement  greatly  resemble  the  refe  mirahiU  of  the  blood-vessels.    This  plexus 

F>K.  392. 


A   SECTION   OF   A   SIMPLE   LYMPHATIC   RETE   MIRABILE,   VIEWED   FROM   THE   SURFACE. 

a,  a,  Afferent  vessels ;  h,  b,  efferent  vessels  only  partially  visible  (from  the  popliteal  space). 

is  surrounded  by  condensed  connective  tissue,  and  is  penetrated  by  blood-vessels, 
though  no  communication  takes  place  between  them  and  these,  the  only  points 
at  which  communication  occurs  being  where  the  great  lymphatic  trunks  empty 
themselves  into  the  vena  cava.  This  refe  would  appear  to  be  the  first  step 
towards  the  formation  of  a  lymphatic  gland.) 

But  of  all  the  considerations  relative  to  the  course  of  these  vessels,  the  most 
interesting  are  those  which  belong  to  the  glandiform  bodies  placed  along  their 
track,  the  abridged  history  of  which  we  shall  give  immediately. 

Termination. — We  have  already  mentioned  the  thoracic  duct  and  the  right 
great  lymphatic  vessel  as  being  the  receptacles  of  all  the  absorbent  vessels  of 
the  body,  and  we  have  also  stated  that  these  two  trunks  enter  the  general  venous 
system  ;  this  union  of  the  blood  with  the  lymphatic  system  takes  place  at  the 
origin  of  the  anterior  vena  cava,  and  this  vessel  may  be  considered  as  the 
general  confluent  for  all  the  absorbents  of  the  body.  The  researches  of  Haller, 
Cruikshank,  and  Mascagni  first  threw  light  on  this  important  fact ;  and  it  is  to 
those  of  Fohmann,  Panizza,  Rossi,  etc.,  that  we  owe  the  realization  of  this 
discovery. 

48 


718 


THE  LYMPHATICS. 


Nerves. — Bert  and  Laffont  have  demonstrated  the  existence  of  vaso-motar 
nerves  in  the  chyliferous  vessels  of  the  Dog.  Galvanization  of  the  solar  plexus 
or  the  great  splanchnic  nerve,  causes  contraction  of  the  wall  of  these  lymphatics. 
(The  lymphatic  spaces  surrounding  vessels  are  designated  })erivasciilar  canals. 
Lymphatics  originate  in  lacunte,  or  spaces  between  the  fibres  of  the  connective 
tissues,  and  these  are  lined  by  endotlielial  cells  ;  they  are  drained  by  lymphatic 
vessels — the  arrangement  presenting  an  analogy  to  the  vascular  system  of  insects 
and  Crustacea.  Masses  of  protoplasm — the  connective-tissue  corpuscles — abound 
in  many  tissues,  occupying  some  of  the  interstitial  spaces  ;  the  latter  communicate 
freely  with  each  other,  the  communication  being  tubes  in  the  form  of  small 
pores  or  canals.  The  fluid  drained  off  is  the  lymph,  which  passes  into  gradually 
enlarging  canals.) 

Lymphatic   Glands. 

The  lymphatic  glands  are  ovoid,  spherical,  or  discoid  bodies  of  medium 
consistency,  grey,  rosy,  or  red-coloured,  and  sometimes  quite  black,  and  which 
at  several  points  intercept  the  course  of  the  lymphatic  vessels. 

Their  number  is  considerable,  and  they  are  rarely  single,  but  most  frequently 


Fig.  394. 


Fig.  393. 


SEOriUN    OF    A    LYMPHATIC    GLAND. 

O,  a,  The  fibrous  tissue  that  forms  its  exterior ; 
6,  6,  superficial  vasa  inferentia ;  c,  c,  larger 
alveoli,  near  the  surface  ^  d,  d,  smaller  alveoli 
of  the  interior ,  e,  e,  fibrous  walls  of  the  alveoli. 


SIMPLE   LYMPHATIC   GLAND. 

,  The  capsule  with  sections  of  lym- 
phatics, d,  d,  passing  through  it ; 
6,  lacunar  and  intercommunicating 
passages,  permeated  by  the  lymph, 
and  forming  the  superficial  lymph- 
path  of  Frey ;  c,  nucleus,  or  me- 
dullary portion,  with  section  of 
blood-vessel  in  the  centre. 


are  collected  in  groups  along  the  blood-vessels.  They  are  always  larger  in  youth 
than  in  old  age. 

All  the  vessels  of  the  lymphatic  system  are  provided  with  at  least  one  gland 
on  their  course,  and  some  even  pass  through  two  or  three  before  opening  into 
the  thoracic  duct  or  great  lymphatic  trunk.  On  reaching  these  glands,  they 
plunge  into  their  substance  by  ramifications,  appearing  on  the  opposite  point 
after  being  reconstituted  into  several  principal  canals,  which  are  generally  larger 
and  less  numerous  than  the  original  vessels.  The  latter  take  the  name  of 
afferents  {vasa  inferentia  or  afferentia)  ;  the  others  are  named  efferents  {vasa 
vfferentia),  because  they  leave  the  gland  to  reach  the  central  canal. 

Structure. — The  structure  of  the  glands  is  extremely  complex. 

They  have  an  envelope  of  connective  tissue  (continuous  with  the  tunics  of  the 


THE  LYMPHATICS. 


719 


Fig.  395. 


afferent  and  efferent  vessels)  that  surrounds  their  proper  substance,  which  is 
composed  of  two  layers  of  a  different  aspect — one  cortical,  the  other  medullary. 

The  first  appears  to  be  granular,  the  second  somewhat  fibrous.  This  proper 
tissue  is  sustained  by  connective  laminse  (or  trabeculce.  septa — continuations  of 
the  capsule)  which  contain  smooth  muscular  fibres.  The  trabeculge  form  alveoli 
in  the  cortical  layer,  and  a  sort  of  minute  tubes  in  the  central  layer.  These 
alveoli — or  follicles — are  in  their  turn  divided  by  fine  reticular  connective 
tissue  into  secondary  spaces,  which  become  smaller  as  they  lie  nearer  the  centre  ; 
at  the  periphery,  where  they  are  most 
voluminous,  they  are  named  lymph  sinuses. 
Everywhere  these  sinuses  are  filled  with 
lymph  corpuscles.  The  arrangement  is 
identical  in  the  medullary  substance;  in  the 
interior  are  seen  a  great  number  of  arterial 
capillaries  or  lymphatic  cords.  The  nerves 
are  derived  from  the  sympathetic  system. 

The  afferent  lymphatics,  where  they 
■enter  the  gland,  communicate  with  the 
alveoli  in  the  cortical  substance  ;  these 
alveoli  are  connected  by  the  cords  of  the 
central  layer,  and  the  latter  are  united, 
in  their  turn,  to  the  alveoli  of  the  op- 
posite side  of  the  cortical  substance,  from 
which  the  efferent  ramuscules  spring.  The 
lymph,  therefore,  traverses  every  part  of 
the  gland,  and  during  this  very  tortuous 
course  becomes  charged  with  lymph-cells. 

Certain  glands  have  a  much  simpler 
structure,  being  entirely  composed  of 
lymphatic  capillaries  rolled  up  on  them- 
«elves  in  clusters,  and  anastomosing  in 
networks.  These  capillaries  arise  from 
the  divergent  arborization  of  the  afferent 
vessels,  and  are  continuous  with  the  con- 
vergent branches  which,  by  their  union, 
form  the  efferent  lymphatics.  The  organs 
have  received  the  name  of  fcdse  ylctnds, 
though  they  are  really  lymphatic  glands. 
In  support  of  this  assertion,  it  may  be 
said  that  "  in  descending  the  animal  series, 
we  see  the  glands  becoming  more  and 
more  simplified,  and  transformed  at  a 
great  number  of  points  into  an  interlacing  of  vessels.  In  birds,  they  only  occupy 
the  base  of  the  neck  and  the  entrance  to  the  chest,  forming  in  all  the  other 
regions  simple  plexuses  ;  in  reptiles  and  fishes,  the  lymphatic  glands  disappear 
altogether,  and  the  plexuses  that  replace  them  are  themselves  not  at  all  compli- 
cated" (Sappey). 

(The  cortical  part  of  the  gland  contains  the  round  masses  of  adenoid  tissue — 
sometimes  called  secondary  nodnles — which  are  continuous  with  the  oval  masses, 
also  adenoid  tissue,  found  in  the  medullary  portion  ;  and  both  oval  and  round 


PORTION  OF  THE  MEDULLARY  SUBSTANCE  OP 
THE  MESENTERIC  GLAND  OF  AN  OX,  THE 
ARTERY  OF  WHICH  IS  INJECTED  WITH 
CHROMATE  OF  LEAD  (MAGNIFIED  300 
DIAMETERS). 

a,  Medullary  substance  with  capillary  net- 
work, fine  reticulum  of  connective  tissue, 
and  a  few  lymph  corpuscles  ;  b,  b,  super- 
ficial lymph-path,  traversed  by  a  reticulum 
of  nucleated  cells  (c,  c),  with  numerous 
anastomosing  prolongations.  The  lymph 
corpuscles  have  for  the  most  part  been 
removed  ;  d,  d,  trabeculae  composed  almost 
exclusively  of  unstriped  muscular  tissue ; 
g,  a  small  medullary  cord,  or  bridge,  con- 
taining a  blood-vessel  and  numerous  lymph 
corpuscles. 


720  THE  LYMPHATICS. 

masses  are  surrounded  by  the  lymph  sinuses.  In  the  centre  of  the  meshes  of 
the  adenoid  tissue  is  a  dark  portion  filled  with  cells  showing  karyokinetic  division 
— this  is  a  germ  centre,  which  is  more  particularly  the  seat  of  the  formation  of 
leucocytes  which  pass  into  the  lymph  sinuses,  and  thence  into  the  vasa  efferentia. 
The  sinuses  are  lined  by  a  single  layer  of  flat  endothehal  cells,  a  similar  layer 
covering  the  surface  of  the  round  masses  in  the  cortex,  the  strands  in  the 
medulla,  and  the  surface  of  the  trabeculse — these  cells  being  even  found  in  the 
bands  of  reticular  connective  tissue  passing  from  the  trabecule. 

Lymphatic  glands  are  richly  supplied  with  blood-vessels,  either  entering  the 
hilum  or  distributed  over  the  surface.  Those  on  the  surface  ramify  on  the 
capsule,  and  penetrate  the  gland  by  running  along  the  centres  of  the  trabeculae. 
The  large  vessel  entering  the  hilum  divides  into  branches,  surrounded  by  con- 
nective tissue,  and  these  also  run  along  the  trabeculae.  From  these  minute 
branches  spring,  which  pass  through  the  lymph  sinuses,  and  are  ultimately  dis- 
tributed to  the  round  masses  in  the  cortex  and  to  the  strands  in  the  medulla, 
ending  in  a  very  fine-meshed  capillary  network.  The  veins  pass  out  of  the  gland 
at  the  hilum.  Nerves  also  penetrate  lymphatic  glands,  and  medullated  and  non- 
medullated  fibres  have  been  traced,  but  their  mode  of  ending  is  unknown. 

It  is  important  to  observe  that  adenoid  tissue  containing  leucocytes  is  not 
limited  to  lymphatic  glands,  but  is  found  in  many  mucous  membranes  some- 
times diffused  in  a  stratum,  and  sometimes  in  sharply  defined  masses  ;  small 
nodules  or  follicles  are  also  found  in  mucous  membranes,  containing  germ 
centres,  and  resembling  the  round  masses  in  a  lymphatic  gland.  These  are 
seen  in  the  solitary  and  agminated  glands  of  Peyer  in  the  intestinal  canal ; 
they  vary  much  in  different  species  of  animals,  and  even  in  individuals  of  the 
same  species  ;  and  they  differ  from  ordinary  lymphatic  glands,  chiefly  in  the  less 
intimate  connection  existing  between  them  and  lymphatic  vessels.  The  leucocytes 
originating  in  them  probably  do  not  enter  the  lymphatic  system  directly,  but 
wander  through  the  epithelium  covering  the  surface  of  the  mucous  membrane. 
Amphibia  have  no  lymphatic  glands,  but,  as  may  be  seen  in  the  Frog,  there  are 
large  lymphatic  spaces  beneath  the  skin,  which  are  traversed  by  very  delicate 
bands  of  connective  tissue. 

Preparation  of  the  Lymphatic  Vessels. — The  lymphatic  networks  can  only  be  studied 
after  having  been  filled  with  mercury  by  means  of  injection;  but  as  this  operation  is  not 
usually  practised  by  the  pupils  for  whom  this  book  is  written,  the  mode  of  performing  it  will 
only  be  traced  in  a  few  words. 

The  apparatus  in  use  consists  of  a  glass  tube  continued  by  a  flexible  one,  which  carries  at 
its  inferior  extremity  an  iron  tap  and  a  fine  cannula,  also  of  iron,  or  (better)  glass.  To  apply 
this  apparatus,  the  tube  ought  to  be  suspended  and  then  filled  with  mercury ;  the  cannula  is  then 
seized  by  the  right  hand,  keeping  it  parallel  to  the  membrane  we  wish  to  inject,  and  burying 
it  in  the  most  superficial  layer  of  that  membrane.  The  extremity  of  the  cannula  is  thu& 
introduced  into  th*:  midst  of  the  meshes  of  the  lymphatic  network,  and  necessarily  wounds 
some  of  the  capillaries  which  compose  it.  In  opening  the  tap,  the  mercury  is  allowed  to  flow 
into  the  capillaries  by  the  solutions  of  continuity  they  present,  and  fills  them  in  the  most  per- 
fect manner.  The  lymphatic  plexuses  being  always  superposed  on  the  capillary  blood-vessels, 
one  is  always  certain  of  injecting  them  only,  in  taking  the  precaution  to  penetrate  the  membrane 
as  superficially  as  possible.  If  the  point  of  the  cannula  enters  too  deeply,  the  mercury  will 
pass  into  the  veins,  and  the  operation  will  be  unsuccessful,  and  must  be  commenced  again. 

To  study  the  branches  and  lymphatic  trunks,  it  will  sufiice  to  inflate  them  from  their  origin 
towards  their  termination.  This  procedure,  properly  conducted — and  it  was  almost  exclusively 
the  only  one  adopted  by  the  older  anatomists — gives  the  most  satisfactory  results,  and  is  even 
suificient  to  demonstrate  the  texture  of  the  glands.  Or  the  trunks  may  be  filled,  from  their 
termination  to  their  origin,  by  some  solidifiable  substance. 


THE  THORACIC  DUCT.  721 

CHAPTER  II. 

THE   LYMPHATICS   IN   PARTICULAR. 

We  will  commence  with  the  examination  of  the  thoracic  duct  and  all  its  affluents, 
and  terminate  by  studying  the  great  lymphatic  vein  {ductus  lymphaticus  dexter'). 

In  this  description  the  glands  and  principal  lymphatic  vessels  will  be  only 
referred  to,  the  arrangement  of  the  networks  being  already  noticed  when  speak- 
ing of  the  different  organs,  and  they  will  be  further  alluded  to  when  treating  of 
the  nervous  system,  the  organs  of  sense,  and  those  of  generation. 

Article  I. — The  Thoracic  Duct  (Fig.  389,  t  t). 

Preparation. — Tie  the  jugulars  and  axillnry  veins  near  their  termination,  as  well  as  the 
anterior  vena  cava  about  the  middle  of  its  length  ;  expose  the  thoracic  duct  by  removing  the 
ribs  on  the  right  side  ;  open  that  vessel  near  the  pillars  of  the  diaphragm,  and  throw  into  its 
interior  two  injections  of  tallow,  one  forward,  the  other  backward  from  the  incision.  The  first 
injection  will  lill  the  canal  and  the  venous  reservoir  which  is  intersected  between  the  ligatures 
applied  to  the  above-named  vessels;  the  second,  although  directed  in  opposition  to  the  valves, 
overcomes  the  resistance  oftVred  by  them,  and  passes  into  Pecquet's  cistern  and  the  principal 
branches  which  open  into  that  confluent. 

Or  we  may  seL-ct  one  of  these  branches  in  the  abdominal  cavity — for  example,  one  of  those 
which  lie  beside  the  colic  arteries  near  tlieir  origin — and  inject  the  entire  thoracic  duct  from 
its  origin  to  its  termination.  But  this  proceeding  requires  more  practical  ability  than  the  first, 
in  order  to  find  the  vessel  which  is  to  receive  the  cannula ;  if  the  animal  is  very  fat,  it  is 
impossible. 

The  thoracic  duct  is  the  general  confluent  for  all  the  lymphatics  of  the  body, 
with  the  exception  of  those  which  come  from  the  right  anterior  hmb  and  the 
right  moiety  of  the  head,  neck,  and  thorax. 

Extent. — It  extends  beneath  the  vertebral  column,  from  the  first  lumbar 
vertebra  to  beyond  the  entrance  to  the  thorax. 

Origin. — Its  origin  is  marked  by  a  very  irregular  dilatation,  described  as  the 
suUumhar  reservoir,  or  cistern  of  Pecquet  {receptacuhim  or  cysterna  chyli),  into 
which  open  the  principal  affluents  of  the  canal. 

This  reservoir  is  divided,  internally,  by  lamellfe  into  several  incomplete  com- 
partments, and  may  be  more  or  less  voluminous  and  circumscribed,  as  well  as 
very  variable  in  shape. 

It  is  placed  above  the  abdominal  aorta  and  the  posterior  vena  cava,  at  the 
anterior  mesenteric  artery,  or  more  frequently  a  little  behind  it. 

Course. — To  this  receptacle  succeeds  a  tube,  the  calibre  of  which  is  very 
irregular,  and  appears  singularly  slender  when  compared  with  the  diameter  of 
the  commencing  dilatation,  or  that  of  the  affluent  vessels  composing  it.  This  is 
the  thoracic  duct.  It  enters  between  the  two  pillars  of  the  diaphragm  (hiatus 
aorticus),  along  with  the  posterior  aorta,  deviating  more  or  less  to  the  right  side 
of  that  vessel,  and  accompanies  it  to  about  the  sixth  dorsal  vertebra,  in  passing 
to  the  outside  of  the  right  intercostal  arteries,  which  it  crosses,  and  beneath  the 
vena  azygos,  beside  which  it  lies.  Sometimes,  however,  we  find  it  carried  in  this 
first  part  of  its  course  directly  above  the  thoracic  aorta,  between  the  double 
series  of  intercostal  arteries,  and  to  the  left  of  the  vena  azygos,  which  is  then 
found  immediately  in  contact  with  the  right  side  of  the  aorta  ;  or  it  may  even 


722  THE  LYMPHATICS  IN  PARUCULAM. 

pass  to  the  right  of  that  vein,  concealing  the  greater  part  of  it  from  sight. 
Leaving  the  above-mentioned  dorsal  vertebra,  the  thoracic  duct  abandons  the 
aorta  and  crosses  the  flexm-e  of  the  vena  azygos  to  the  left,  to  extend  itself 
forward  on  the  left,  but  often  also  on  the  right  side  of  the  trachea.  It  after- 
wards places  itself  between  the  two  axillary  arteries,  crosses  the  interval  between 
the  pre-pectoral  glands,  emerges  from  the  chest,  and  terminates  in  a  manner  to 
be  indicated  hereafter. 

Termination. — The  terminal  extremity  of  the  thoracic  duct  has  always  a  dila- 
tation analogous  to  that  which  exists  at  its  origin,  though  much  smaller,  better 
circumscribed,  and  less  irregular — a  dilatation  which  opens  into  the  anterior 
vena  cava  sometimes  by  a  single  orifice  furnished  with  valves,  at  other  times  by 
two  very  short  branches,  the  length  of  which  cannot  be  estimated  at  more  than 
the  fifth  part  of  an  inch,  and  which  are  also  valvular  at  their  entrance.  The 
point  where  this  entrance  takes  place  is  nearly  always  at  the  summit  of  the  vena 
cava,  and  precisely  at  the  point  of  junction  of  the  two  jugulars.  The  thoracic 
duct  rarely  opens  elsewhere  ;  though  the  fact  that  it  does  so  at  times  is  exempli- 
fied in  a  specimen  in  the  museum  of  the  Lyons  School,  in  which  the  opening  of 
the  duct  is  placed  between  the  termination  of  the  left  jugular  and  that  of  the 
corresponding  axillary  vein. 

Varieties  in  Solipeds. — "  The  thoracic  duct  is  far  from  always  showing  itself 
in  Solipeds  as  I  have  described  it,  but  in  its  course  and  insertion  it  presents  a 
great  number  of  variations  which  we  w^ill  now  pass  in  review. 

"  The  single  canal  is  sometimes  divided  into  two  branches,  which,  after  pro- 
ceeding parallel  to  each  other,  soon  unite  to  form  a  single  vessel.  This  division 
usually  takes  place  at  the  base  of  the  heart,  where  the  lymphatics  of  the 
bronchial  and  a-sophageal  glands  enter  ;  it  forms  a  ring  the  diameter  of  which 
is  often  not  more  than  f  of  an  inch,  or  an  ellipse  whose  larger  axis  is  from  § 
to  f  of  an  inch.  We  see  this  happen  once,  twice,  and  even  thrice  in  the  anterior 
half  of  the  canal,  which  becomes  single  at  its  termination  as  it  was  at  its  origin. 
The  spaces  circumscribed  by  the  bifurcations  constitute  what  have  been  termed 
the  insuhe. 

"  The  duct,  instead  of  remaining  single,  very  often  becomes  double  from  its 
commencement  (Fig.  397).  Then  the  two  canals  are  sensibly  equal,  or  one  is 
larger  than  the  other.  If  they  are  unequal,  it  is  usually  the  right  which  has  the 
advantage,  though  the  contrary  sometimes  occurs.  In  any  case,  the  two  ducts 
are  isolated — one  being  to  the  right,  the  other  to  the  left  of  the  aorta.  In 
advancing  towards  the  entrance  to  the  thorax,  they  remain  completely  separated, 
or  communicate  with  each  other  by  one  or  two — more  or  less  voluminous,  trans- 
verse anastomosing  branches.  Reaching  to  ten,  eight,  and  sometimes  even  to 
two  inches  from  their  opening  into  the  jugular  gulf,  the  two  ducts  approach 
each  other,  and  become  at  last  a  single  vessel.  Their  fusion  generally  takes 
place  at  the  base  of  the  heart,  and  I  have  never  seen  them  remain  distinct 
throughout  their  whole  extent,  to  enter  the  vena  cava  separately. 

"  Sometimes  (Fig.  39k)  there  emanates  from  the  gland,  at  the  entrance  to  the 
thorax,  a  long  canal  which  proceeds  parallel  to  the  first,  and  joins  it  after  a 
retrogade  course,  near  the  crura  of  the  diaphragm. 

"  The  thoracic  duct,  double  for  the  greater  part  of  its  extent,  from  the  time 
it  leaves  the  receptaculum  chyli,  occasionally  ends  by  becoming  triple.  In  this 
case,  the  largest  of  the  two  canals  is  divided  into  tAvo  branches  ;  then  the  three 
canals,  after  pursuing  a  certain  course,  all  join  at  the  same  point,  or  two  are  first 


THE   THORACIC  DUCT 
Fig.  396, 


Fig.  397. 


Fig.  398. 


DIFFERENT    VARIETIES   OF    THE    THORACIC    DUCT   IN    THE    HORSE. 

A,  Receptaculum  chyli ;  b,  sublumbar  branches  ;  c.  anterior  mesenteric  branch  ;  d,  posterior  mesen- 
teric  branch.  In  Fig.  396  the  duct  is  single,  the  usual  condition,  and  enters  the  summit  of  the 
anterior  vena  cava  by  two  short  branches.  It  is  double  in  Fig.  397 ;  and  in  Fig.  398  it  has  a 
long  branch  that  arises  at  the  entrance  to  the  thorax  and  joins  the  duct,  by  a  retrograde  course 
near  the  pillars  of  the  diaphragm. 


724  TEE  LYMPHATICS  IN  PARTICULAR. 

united  into  a  single  vessel,  into  which  the  third  opens  at  a  variable  distance  from 
the  confluent  of  the  first."  ^ 

The  affluents  of  the  thoracic  duct. — The  lymphatic  vessels  which  enter  the 
thoracic  duct  are  as  remarkable  for  their  number  as  their  volume.  Some  empty 
themselves  into  the  receptaculum  chyli  ;  a  few  vessels  open  into  the  great 
lymphatic  vessel  of  the  thorax,  and  the  others  terminate  in  that  canal  near  its 
entrance  into  the  venous  system. 

The  first,  variable  in  their  number — particularly  the  largest — are  more  espe- 
cially regarded  as  the  roots  of  the  thoracic  duct. 

Ordinarily  three  are  found,  with  a  certain  number  of  small  accessory  trunks. 
One  of  the  largest  branches  enters  the  posterior  part  of  the  receptaculum  chyli. 
Very  often  double,  and  even  multiple,  it  arises  from  an  enormous  group  of  glands 
in  the  sublumbar  region,  around  the  posterior  extremity  of  the  abdominal  aorta 
and  vena  cava,  and  into  which  are  collected  all  the  vessels  of  the  posterior  limbs, 
the  pelvis,  abdominal  walls,  and  the  pelvi-inguinal  viscera.  The  other  two  trunks 
reach  the  left  side  of  the  receptaculum,  and  result  from  the  union  of  the  lym- 
phatics which  come  from  the  abdominal  digestive  organs ;  among  these 
lymphatics,  however,  there  are  some  belonging  to  the  parietes  of  the  stomach 
and  the  parenchyma  of  the  liver  and  spleen,  and  which  reach  the  right  side  of 
the  receptaculum,  to  open  singly  into  that  cavity. 

The  affluents  the  thoracic  duct  receives  on  its  course,  proceed  from  the  viscera 
contained  in  the  thoracic  cavity,  and  from  the  walls  of  that  cavity. 

Those  which  terminate  at  the  anterior  extremity  of  the  duct  are  formed  by 
the  lymphatics  of  the  left  anterior  Hmb,  and  the  left  half  of  the  thorax, 
diaphragm,  neck,  and  head. 

We  will  now  examine  rapidly  all  the  radicles  of  these  affluents. 

Article  II. — The  Lymphatics  which  foem  the  Affluents  of  the 
Thoracic  Duct. 

These  lymphatic  vessels  are  divided  into  five  groups  :  1.  Those  of  the 
abdominal  limb,  the  pelvis,  the  abdominal  parietes,  and  the  pelvi-inguinal  organs. 
2.  Those  of  the  abdominal  digestive  viscera.  3.  Those  of  the  organs  contained 
in  the  chest.  4.  Those  of  the  thorax.  5.  Those  of  the  head,  neck,  and  anterior 
limb. 

Lymphatics  of  the   Abdominal   Limb,  Pelvis,  Abdominal   Parietes, 
and  the  Pelvi-inguinal  Organs. 

All  these  vessels  converge  towards  an  immense  group  of  glands — the  sub- 
lumbar.  Besides  these,  there  are  other  groups  on  different  parts  of  their  course, 
constituting  the  deep  inguinal,  superficial  inguinal,  popliteal,  iliac,  and  precrural 
glands.  The  successive  description  of  these  glands,  and  their  afferent  and 
efferent  vessels,  will  complete  the  study  of  this  apparatus. 

1.  Sublumbar  Glands  (Fig.  399). 

This  group,  which  occupies,  as  its  name  indicates,  the  sublumbar  region, 
comprises  :  1.  A  small  single  mass  situated  in  the  sinus  of  the  angle  formed  by 
the  two  internal  iliac  arteries,  and  is  often  only  a  single  large  gland.    2.  Another 

'  G.  Colin,  Traite  de  Physiologie  Comparde  det  Animauz  Domestiques,  2nd  Edition,  vol.  ii 
Paris;  1871. 


THJiJ  AFFLUENTS  OF  THE  THORACIC  DUCT. 

Fig.  399. 


725 


THK    LYMPHATIC   SYSTEM   OF    THE    HORSE. 


Facial   and   nasal   ple.xus  the    branches   of  which  pass  to  the  subglossal  glands  ;  B,  c,  parotid 
lymphatic  gland,  sending  vessels  to  the  pharyngeal  gland;  d,  E,  large  trunks  passing  towards 


726  THE  LYMPHATICS  IN  PARTICULAR. 

mass  lodg^ed  between  the  two  iliac  arteries,  and  a  third  placed  without,  and  to 
the  front  of,  the  common  iliac  ;  these  two  are  double.  3.  A  single  agglomera- 
tion of  glandular  lobules  dispersed  around  the  origin  of  the  posterior  mesenteric 
and  spermatic  arteries  ;  these  are  separate  from  one  another. 

The  different  masses  receive  the  lymphatics  of  the  pelvis,  the  emergent 
branches  of  the  deep  inguinal  glands,  those  which  come  from  the  iliac  glands, 
some  ramuscules  from  the  rectum  and  large  colon,  and  those  from  the  spermatic 
cord. 

They  are  bound  to  each  other  by  communicating  branches,  and  give  rise  to 
several  series  of  emergent  branches,  which  soon  collect  into  one  or  more  trunks 
that  enter  the  receptaculum  chyli. 

2.  Deep  Inguinal  Glands. 

This  is  a  considerable  mass  of  glandular  lobules  lodged  beneath  the  crural 
aponeurosis  and  arch  in  the  interstice  between  the  adductor  muscles  of  the  leg, 
along  with  the  iliac  vessels,  within  which  they  are  placed. 

The  form  of  this  group  is  elongated,  and  its  length  may  be  six  to  eight 
inches,  or  even  more  ;  its  superior  extremity  extends  as  high  as  the  anterior 
border  of  the  pubis.  It  is  composed  of  from  fifteen  to  twenty  lobules,  which 
rarely  have  a  uniform  colour— some  being  grey  and  others  brown,  or  nearly 
black. 

The  afferents  are  formed  by  the  superficial  lymphatics  that  accompany 
the  internal  saphena  vein — the  radicles  of  which  may  be  traced  beyond  the  fet- 
lock- and  by  the  deep  satellite  vessels  of  the  iliac  artery  and  vein.  The  efferents 
proceed  to  the  sublumbar  glands,  by  ascending  in  the  abdomen  along  the 
external  iliac  artery  and  vein. 

3.  SuPEEFiciAL  Inguinal  Glands. 

These  are  placed  in  front  of  the  inguinal  ring,  at  the  side  of  the  sheath,  on 
the  track  of  the  subcutaneous  abdominal  artery,  where  they  form  a  small 
elongated  mass  from  two  and  a  haK  to  three  inches  in  length,  and  are  composed 
of  a  dozen  principal  lobules. 

Their  afferents,  which  are  very  numerous,  come  from  the  inner  aspect  of  the 
thighs,  the  sheath,  scrotum,  and  the  inferior  abdominal  wall.  The  efferent 
vessels,  much  larger,  but  less  numerous — there  are  only  five  or  six — ascend  in 
the  inguinal  canal,  accompanying  the  external  pudic  artery  and  the  inguinal 
nerves.  They  enter  the  deep  inguinal  glands,  after  traversing  the  inguinal  canal 
in  company  with  the  prepubic  artery. 


the  thorax ;  F,  G,  H,  glands  receiving  the  superficial  lymphatics  of  the  neck,  a  portion  of  those 
of  the  limbs,  and  those  of  the  pectoral  parietes  ;  i,  junction  of  the  jugulars;  j,  axillary  veins; 
K,  summit  of  anterior  vena  cava ;  L,  thoracic  duct ;  M,  lymphatics  of  spleen — N,  of  stomach — 0, 
of  large  colon — S,  of  small  colon  ;  R,  lacteals  of  small  intestine — all  joining  to  form  the  two 
trunks,  p,  Q,  which  open  directly  into  the  receptaculum  chyli ;  T,  trunk  which  receives  the 
branches  of  the  sublumbar  glands,  u,  to  which  the  vessels  of  the  internal  iliac  glands,  V,  the 
receptacles  of  the  lymphatics  of  the  abdominal  parietes,  pass ;  w,  precrural  glands  receiving 
the  lymphatics  of  the  posterior  limb,  and  which  arrive  independently  in  the  abdomen;  X,  super- 
ficial inguinal  glands  into  which  the  lymphatics  of  the  mamma:,  external  generative  organs,  some 
superficial  trunks  of  the  posterior  limb,  etc.,  pass ;  Z,  deep  inguinal  glands  receiving  the  super- 
ficial lymphatics,  z',  of  the  posterior  limbs. 


THE  AFFLUENTS  OF  THE  THORACIC  DUCT.  727 

4.  Popliteal  Glands. 

These  are  a  very  small  mass  of  from  three  to  five  independent  lobules, 
situated  behind  the  great  sciatic  nerve  and  gastrocnemius  muscle,  between  the 
biceps  femoris  and  semitendinosus  muscles,  and  near  the  femoro-popliteal  artery. 

They  receive  some  of  the  lymphatics  from  the  neighbourhood  of  the  hock, 
and  those  coming  from  the  posterior  and  inferior  part  of  the  gluteal  region. 
Their  efferents  join  the  deep  inguinal  glands,  by  followmg  the  muscular  inter- 
stices of  the  thigh. 

5.  Iliac  Glands. 

Slightly  yellow  in  colour,  and  of  a  soft  consistence,  these  glands  are  five 
or  six  in  number,  and  form  a  group  which  is  situated  in  the  triangular  space 
between  the  two  branches  of  the  circumflex  iliac  artery.  They  receive  the 
emergent  branches  of  the  precrural  glands,  and  a  great  number  of  deep 
lymphatics  from  the  abdominal  wall.  Their  efferent  branches,  four  or  five  in 
number,  follow  the  circumflex  iliac  artery  to  pass  to  the  sublumbar  glands. 

6.  Precrural  Glands. 

Placed  within  the  anterior  border  of  the  tensor  fascia  lata,  on  the  course  of 
the  circumflex  iliac  artery,  these  glands  form  a  small  elongated  mass,  composed 
of  a  dozen  lobules  lying  close  to  each  other.  To  this  group  come  afferent 
vessels  from  the  anterior  and  internal  part  of  the  thigh.  It  gives  origin  to 
three  or  four  large  efferent  vessels,  which  ascend  the  internal  face  of  the  fascia 
lata  muscle,  accompanying  the  circumflex  iliac  artery,  and  entering  the  abdominal 
cavity  near  the  angle  of  the  haunch,  to  join  the  iliac  glands. 

Lymphatics  of  the  Abdominal  Viscera. 

1.  Glands  and  Lymphatic  Vessels  of  the  Rectum  and  Floating  Colon. 

The  glands  in  this  portion  of  the  intestinal  tube  are  :  at  flrst,  two  or  three 
lobules  placed  at  the  base  of  the  tail  and  on  each  side  of  the  sphincter  ani ;  in 
the  second  place,  a  very  numerous  series  of  small  glandular  bodies  situated  along 
the  small  curvature  of  the  viscus  ;  thirdly,  some  rounded  lobules  comprised 
within  the  tAvo  layers  of  the  mesentery,  and  placed  on  the  course  of  the  arterial 
and  venous  divisions. 

Originating  in  the  texture  of  the  mucous  and  muscular  tunics,  the  lymphatic 
radicles  gain  the  glands  of  the  small  curvature  of  the  colon,  and  escape  from 
them  as  efferent  branches,  which  pass  in  great  numbers  into  the  mesentery. 
These  efferents — or  at  least  some  of  them — pass  through  the  lymphatic  glands 
placed  on  the  course  of  the  blood-vessels,  and  collect,  near  the  origin  of  the 
posterior  mesenteric  artery,  into  several  somew^hat  luminous  branches,  which 
join  the  divisions  of  the  sublumbar  glands,  or  those  of  the  large  colon. 

2.  Glands  and  Lymphatic  Vessels  of  the  Double  Colon. 

There  is  seen  on  this  enormous  viscus  ^  double  chain  of  glands,  lying  beside 
the  colic  arteries,  and  numerous  small  lobules  disseminated  at  a  short  distance 
from  the  principal  glands,  and  on  the  track  of  the  collateral  branches  furnished 
by  these  two  vessels. 


728  THE  LYMPHATICS  IN  PARTICULAR. 

Received  at  first,  for  the  most  part,  by  these  lobular  bodies,  the  lymphatics 
which  have  emanated  from  the  tmiics  of  the  double  colon  afterwards  join  the 
principal  glands,  from  which  they  emerge  in  forming  several  large  satellite 
branches  for  the  colic  vessels.  Only  two  or  three  in  nimiber  at  the  pelvic 
flexure,  these  branches  are  increased  to  ten  or  twelve  on  arriving  near  the  origin 
of  the  colic  arteries.  It  is  from  the  union  of  these  vessels  with  those  of  the 
small  intestine,  tli^it  the  two  large  mesenteric  trunks  (Fig.  896,  a,  c)  arise, 
which,  with  the  branches  emanating  from  the  sublumbar  glands  (Fig.  396,  b), 
form  the  receptaculum  chyli. 

3.  Glands  and  Lyjiphatic  Vessels  of  the  C^cu:\r. 

There  exists,  on  the  track  of  each  ca^cal  artery,  a  moniliform  series  of  glands, 
farther  apart  from  one  another  than  those  of  the  double  colic  chnin,  to  which 
the  vessels  coming  from  the  caecal  membranes  are  directed,  cind  from  which 
several  long  satellite  branches  of  the  blood-vessels,  that  proceed  to  the  r^ame 
trunk  as  those  of  the  small  intestine,  depart. 

4   Glands  and  Lymphatic  Vessels  of  the  Small  Intestine. 

The  glands  which  receive  the  lymphatic  vessels  from  the  email  intestine 
are  very  large  and  abundant.  About  thirty  in  number,  of  a  grey  colour,  very 
compact,  fusiform,  often  bifurcated  at  their  superior  extremity,  these  glands 
are  placed  in  the  substance  of  the  mesentery,  near  the  origin  of  the  anterior 
mesenteric  artery,  from  which  those  belonging  to  the  portion  of  intestine 
nearest  the  end  of  the  viscus  are  most  distant.  The  latter  also  possess,  in 
addition,  fifteen  special  small  glandular  lobules,  dispersed  on  the  track  of  the 
ileo-cffical  artery. 

We  have  already  noted  the  richness  of  the  vascular  apparatus  which  rises 
from  the  wall  of  the  small  intestine,  towards  the  mesenteric  glands.  It  must 
be  added  that  these  glands  give  off,  at  their  superior  extremity,  large  l>ranches, 
two  or  three  for  each,  which  soon  coalesce  to  form  more  voluminous  branches, 
that  concur  in  the  formation  of  the  two  intestinal  roots  of  the  receptaculum 
chyh. 

5.  Glands  and  Lymphatic  Vessels  of  the  Stomach. 

There  are  two  classes  of  lymphatic  glands  for  the  stomach  :  1.  Several  large 
glands  situated  on  the  small  curvature  of  the  organ.  2.  A  series  of  small 
lobules  disseminated  along  the  great  curvature  to  the  attachment  of  the  gastro- 
colic omentum. 

The  vessels  which  emerge  from  them  "  gather  on  the  course  of  the  gastric 
arteries  and  veins,  and  ascend  to  the  great  tuberosity,  near  the  trunk  of  the 
coeliac  artery  ;  there  they  anastomose  with  the  lymphatics  from  the  spleen  and 
liver,  and  unite  into  several  flexuous  branches,  some  of  which  open  directly  into 
the  thoracic  duct,  to  which  the  others  pass,  after  joining  the  anterior  trunk  of 
the  intestinal  lymphatics  "  (Colin). 

6.  Glands  and  Lymphatic  Vessels  of  the  Spleen  and  Liver. 

"  The  lymphatic  vessels  of  the  spleen,  rising  some  from  the  interior  of  the 
viscus,  others  from  its  surface,  pass  towards  the  splenic  artery  and  vein  :  they 
traverse  several  groups  of  glands  on  the  track  of  these  vessels,  commencing  from 


THE  AFFLUENTS  OF  THE  THORACIC  DUCT.  729 

the  middle  of  the  fissure,  ascend,  five  or  six  in  number,  towards  the  origin  of 
the  artery  in  forming  a  sinuous  mass,  the  divisions  of  which,  anastomosing  with 
those  of  the  stomach  and  liver,  open,  on  the  one  hand,  with  the  latter  in  the 
anterior  trunk  of  the  intestinal  lymphatics,  and,  on  the  other,  into  a  magnificent 
plexus  communicating  directly  with  the  thoracic  duct. 

"  Finally,  the  lymphatics  of  the  liver  form  a  very  close  network  on  the 
surface,  and  another  in  the  interior  of  the  gland.  They  collect  towards  the 
posterior  fissure,  and  first  dip  into  a  primary  and  very  small  glandular  group, 
then  into  a  second  group  of  voluminous  round  glands,  which  are  concealed 
between  the  trunk  of  the  vena  portas  and  the  pancreas.  They  open  in  common 
with  the  vessels  of  the  stomach  and  spleen  "  (Colin). 

Glands  and  Lymphatic  Vessels  of  the  Organs  contained  in  the 
Thoracic  Cavity. 

We  find  annexed  to  these  organs  three  groups  of  lymphatic  glands  :  1.  A 
series  of  small  granular  masses  in  the  posterior  mediastinum,  on  the  course  of 
the  oesophagus.  2.  The  bronrhial  glands,  situated  in  the  angle  of  bifurcation 
of  the  trachea,  around  the  origin  of  the  bronchi,  which  they  follow  for  a  short 
distance  into  the  pulmonary  tissue.  3.  Two  long  strings  of  lobules  extended 
on  the  sides  of  the  inferior  face  of  the  trachea,  from  the  base  of  the  heart  to 
near  the  first  rib. 

The  first  group  receives  the  posterior  lymphatics  of  the  oesophagus,  the 
second  those  of  the  lung,  and  the  third  those  of  the  pericardium,  heart,  and  a 
portion  of  the  trachea  and  oesophagus.  Their  efferents,  uniting  into  some  large 
trunks,  enter  the  thoracic  duct  at  different  distances. 

Glands  and  Lymphatic  Vessels  of  the  Thoracic  Walls. 

These  glands  form  three  series  :  1.  A  double  chain  of  small  rounded  glands, 
situated  on  each  side  of  the  dorsal  column,  above  the  intercostal  spaces,  and 
beneath  the  costal  pleura.  2.  A  frequently  voluminous  mass,  lodged  at  the 
base  of  the  xiphoid  cartilage,  behind  the  heart,  and  in  front  of  the  inferior 
part  of  the  diaphragm.  3.  Some  rudimentary  glands  lying  beside  the  internal 
thoracic  vessels. 

The  lymphatics  of  the  diaphragm,  after  receiving  those  from  the  convex 
face  of  the  liver,  pass  to  the  glands  placed  at  the  base  of  that  muscle,  whence 
they  escape  in  the  form  of  several  vessels  that  accompany  the  internal  thoracic 
vessels,  and  open  into  the  anterior  extremity  of  the  thoracic  duct  or  the  great 
lymphatic  vein,  the  majority  of  them  through  the  medium  of  the  prepectoral 
glands.  These  vessels  receive,  on  their  course,  those  which  are  brought  from 
the  inferior  part  of  the  intercostal  spaces  into  the  supra-sternal  glands. 

The  other  lymphatic  vessels  of  the  thoracic  wall  ascend  between  the  two 
muscles  which  close  these  spaces,  and  go  to  the  subdorsal  glands,  which  after- 
wards eject  them,  near  the  origin  of  the  thoracic  duct,  in  the  form  of  one  or 
two  long  vessels  proceeding  in  a  retrograde  manner  on  each  side  of  the  dorsal 
vertebrae. 

Lymphatic  Vessels  of  the  Head,  Neck,  and  Anterior  Limb. 

These  vessels  are  aU  directed  towards  the  entrance  to  the  chest,  and  ai-e 
gathered  into  a  group  of  glands,  called  the  frejpectoral,  which,  with  regard  to 


730  TEE  LYMPHATICS  IN  PARTICULAR. 

the  lymphatics  of  the  anterior  part  of  the  body,  play  the  same  part  as  the 
sublumbar  glands  do  to  the  vessels  of  the  posterior  region. 

Before  arriving  at  this  common  point  of  convergence,  they  are  intercepted 
on  their  course  by  other  glands,  which  form  four  principal  groups  :  1.  The 
guttural  or  p?iaryngeal  glands.  2.  The  submaxillary  gkmds.  3.  The  prescapular 
glands.     4,  The  brachial  glands. 

In  studying  these  different  glandular  groups  in  succession,  with  their  afferent 
and  efferent  vessels,  a  sufficient  idea  will  be  afforded  of  the  entire  lymphatic 
apparatus  in  the  region  which  remains  to  be  examined. 

1.  Pkepectoral  Glands.^ 

These  form,  on  each  side  of  the  terminal  extremity  of  the  jugular,  within 
the  inferior  border  of  the  scalenus  muscle,  a  very  large  mass  which  extends  into 
the  chest  by  passing  beneath  the  axillary  vessels,  and  asosnds  to  the  inner  face 
of  the  first  rib  on  each  side. 

Into  these  glands  pass  the  lymphatic  vessels  emerging  from  the  prescapular 
and  axillary  glands,  those  which  descend  along  the  trachea  with  the  common 
carotid,  and  which  come  from  the  pharyngeal  glands,  as  well  as  the  majority  of 
those  which  follow  the  internal  thoracic  vessels. 

They  give  rise  to  several  short  and  voluminous  branches  :  those  from  the 
glands  of  the  right  side  form,  by  their  junction,  the  great  lymphatic  vein  ;  and 
those  from  the  left  side  join  the  thoracic  duct,  or  enter  separately  beside  the 
latter,  at  the  summit  of  the  anterior  vena  cava. 

2.  Pharyngeal  Glaot)S. 

Very  numerous,  soft,  and  loosely  united  to  one  another,  these  glands  are 
disposed  in  an  elongated  mass  that  occupies  the  lateral  plane  of  the  pharynx, 
below  the  guttural  pouch,  and  is  prolonged  backwards,  even  beyond  the  thyroid 
body. 

They  receive  all  the  lymphatics  from  the  head ;  some  come  directly  from 
the  base  of  the  tongue,  the  soft  palate,  the  pharyngeal  walls,  and  the  larynx ; 
the  others  are  derived  from  the  submaxillary  glands,  and  from  a  lobule  lodged 
in  the  substance  of  the  parotid  gland. 

The  efferent  branches  which  leave  it  are  four  or  five  in  number.  Always 
voluminous,  they  descend  along  the  trachea,  some  separately,  but  the  majority 
are  united  in  a  fasciculus  which  follows  the  carotid  artery.  They  have  on  their 
course  several  elongated  glands,  to  which  the  lymphatic  radicles  that  arise  from 
the  cervical  portion  of  the  trachea  nnd  oesophagus  pass.  On  arriving  near  the 
entrance  to  the  chest,  they  are  generally  lost  in  the  prepectoral  glands  ;  though 
some  of  them  traverse  these  without  dividing,  and  directly  enter — on  the  left — 
the  thoracic  duct,  and  on  the  right,  the  great  lymphatic  vein.  It  has  been  even 
possible  for  us  to  inject  the  latter  vessel  by  one  of  these  vessels  exposed  on  the 
right  side. 

3.  Submaxillary  or  Subglossal  Glands. 

They  represent  a  fusiform  mass  situated  at  the  bottom  of  the  submaxillary 
space,  in  the  receding  angle  comprised  between  the  digastricus  on  the  one  side, 

'  These  are  glands,  we  believe,  which  ought  to  be  regarded  as  the  representatives  of  the 
axillary  glands  of  Man. 


TEE  GREAT  LYMPHATIC  VEIN. 


731 


and  the  mylo-hyoideus  and  subscapulo-hyoideus  muscles  on  the  other,  above  and 
near  to  the  facial  artery.  The  lymphatics  of  the  tongue,  cheeks,  lips,  nostrils, 
and  nasal  cavities  join  these  glands.  Their  efferents  reach  the  pharyngeal  or 
guttural  glands. 

4.  Prescapular  Glands. 

By  their  union  these  form  a  kind  of  chain,  at  least  twelve  inches  in  length, 
placed  on  the  course  of  the  ascending  branch  of  the  inferior  cervical  artery, 
beneath  the  internal  face  of  the  mastoido-humeralis  muscle,  and  descending 
close  to  the  attachment  of  the  sterno-maxillaris  muscle. 

The  majority  of  the  lymphatics  of  the  neck,  and  those  of  the  breast  and 
shoulder,  open  into  these  glands.  Their  efferents,  short  and  volummous,  enter 
the  prepectoral  glands. 

5.  Brachial  Glands. 

Situated  beneath  the  anterior  limb,  inside  the  arm,  these  vessels  are  divided 
into  two  groups — one  placed  near  the  ulnar  articulation,  within  the  inferior 
extremity  of  the  humerus ;  the  other  disposed  in  a  discoid  mass  behind  the 


Fig.  400. 


Fig.  401. 


THE  GREAT  LYMPHATIC  VEIN  AKD  ENTRANCE  OF  THE  THORACIC  PVCT. 

A,  Thoracic  duct;  B,   great  lymphatic  vein,  or  right  lymphatic  trunk;  C,  D,  anastomoses  estab- 
lished between  them  near  their  insertion. 


brachial  vessels,  near  the  common  insertion  of  the  teres  major  and  latissimus 
dorsi. 

The  first  group  receives  the  vessels  from  the  foot  and  the  forearm,  wnich 
accompany  the  superficial  veins,  or  pass  with  the  deep  arteries  and  veins  into 
the  muscular  interstices.  It  sends  nine  or  ten  flexuous  branches  to  the  second 
group,  into  which  open  directly  the  lymphatics  of  the  arm  and  shoulder,  and 
from  which  emerge  a  certain  number  of  efferents  that  pass,  in  company  with  the 
axillary  vessels,  to  the  prepectoral  glands. 

Article  III. — Great  Lymphatic  Vein. 

The  second  large  receptive  trunk  of  the  lymphatic  vessels,  this  great  vein 
(the  dtfchis  h/mphaficus  dexter)  leaves  the  prepectoral  glands  of  the  right  side, 
and  therefore  becomes  the  general  confluent  of  the  lymphatics  from  the  right 
anterior  limb,  the  right  axillary  and  superficial  costal  regions,  as  well  as  the 
right  half  of  the  head,  neck,  and  diaphragm. 

This  trunk  is  only  from  three-fourths  of  an  inch  to  two  inches  in  length. 


732  THE  LYMPHATICS  IN  PARTICULAR. 

"  It  usually  opens  at  the  junction  of  the  jugulars,  at  the  side  of  the  vessels,  by 
an  orifice  furnished  with  a  double  semilunar  valve.  Sometimes  one  or  two  of 
the  branches  which  concur  to  form  it,  describe  circumvolutions  around  the 
corresponding  brachial  trunks  or  some  of  its  divisions,  before  joining  the  others. 
Lastly,  it  is  not  rare  to  see  this  lymphatic  trunk  anastomose  with  the  thoracic 
duct  by  voluminous  collateral  branches,  then  unite  with  it  in  such  a  way  as  to 
be  inserted  together  by  a  single  orifice  above  the  confluent  of  the  jugulars  " 
(Cohn) 

Differential  Characters  in  the  Lymphatic  System  of  other  than  Soliped  Animals. 

The  lymphatic  system,  glaiiJs  aud  vessels,  is  more  developed  in  Ruminants  and  the  Pig 
than  in  the  Carnivora. 

In  this  respect  the  domesticated  animals  may  be  classified  in  the  following  order:  Ox, 
Sheep,  Horse,  Pig,  Dog,  Cat. 

Kusiinants. — "  The  thoracic  duct  of  large  Ruminants,  when  it  has  entered  the  thorax  by 
a  special  opening  in  the  diaphragm,  almost  distinct  from  that  of  the  aortic  liiiitus,  is  placed 
above  and  to  the  right  of  the  aorta,  between  it  and  the  spine.  There,  although  outside  the 
corresponding  intercostal  arteries,  it  is  completely  concealed  by  a  thick  layer  of  adipose  tissue, 
in  which  are  numerous  subdorsal  glands.  Towards  the  fifth  dorsal  vertebrr^  ii  receives  a  large 
lymphatic  vessel  from  the  enormous  gland  on  the  track  of  the  oesophagus  in  the  posterior 
mediastinum  ;  it  then  crosses  the  direction  of  the  aorta  and  the  oesophagus,  passes  to  the  left, 
gains  entrance  to  the  thorax,  anil  upens  in  front  of  the  first  rib,  above  the  junction  of  the  left 
jugular  with  the  anterior  vena  cava."  ' 

"  The  varieties  it  presents  in  the  Ox  are  numerous  and  very  common.      The  rarest  dis- 
position is  that  of  a  canal,  single  throughout  its 
Fig.  402.  entire  length,  such  as  it  has  been  described^  and 

sucii  as  it  is  usually  found  to  be  in  small  Ruminants 
(Fig.  406).  This  canal  (Fig.  403),  single  at  its 
origin  aud  for  the  greater  part  of  its  extent,  often 
bifurcates  towards  the  base  of  the  heart,  or  at  a 
short  distance  from  its  insertion.  Of  these  two 
branches,  one  passes  to  the  rigiit  of  the  oesophagus 
and  trachea,  th<i  other  to  the  left  of  these,  in  follow- 
ing the  ordinary  direction ;  and,  at  the  entrance 
to  the  thorax,  they  either  terminate  separately,  each 
entrance  of  the  thoracic  duct  in  in  the  angle  formed  by  the  union  of  the  jugular  and 
the  ox.  corresponding  axillary  vein,  or  together  at  the  samo 

point — the  confluent  of  tlie  two  jugular  veins. 
"It  happens  tliat  one  of  the  branches  of  the  bifurcated  canal  is,  in  its  turn,  subdivided  Into 
two  smnller  branches,  and  that  the  other  experiences  at  the  same  time  a  similar  subdivision; 
so  that  the  trunk  of  the  canal,  at  first  single,  becomes  double,  then  quadruple,  and  con.-jequently 
opens  into  the  venous  system  by  four  distinct  orifices.  If  the  branches  of  the  canal,  instead  of 
remaining  isolated,  send  oflf  transverse  anastomoses,  there  results  a  complication  of  which 
Solipeds  do  not  offer  an  example  (Fig.  402). 

"  The  tlioracic  duct  is  often  double  throughout  its  extent.  The  two  canals  are  then  detached 
separately  from  the  receptaculum  chyli ;  one  follows  the  right  side,  the  other  the  left  side  of 
the  aorta,  describing  an  arch  with  concavity  downward  at  the  base  of  the  heart,  on  the  lateral 
parts  of  the  trachea,  terminating  either  very  near  one  another,  and  on  the  same  transverse  line, 
at  the  junction  of  the  two  jugulars ;  or  one  to  the  right,  the  other  to  the  left,  in  each  of  these 
two  veins,  and  not  far  from  their  junction  with  the  axillaries  (Fig.  404). 

"  When  the  two  canals  arise  from  the  receptaculum,  they  sometimes  repeatedly  anastomose 
with  each  other  by  sinuous  and  curved  branches,  as  sliown  in  Fig.  405. 

" Then  all  the  branches  collect  in  the  antejior  mediastinum,  and  constitute  a  single  canal 

0  Zundel  has  pointed  out  the  curious  fact,  that  in  Ruminants,  the  long,  special,  lymphatic 
gland  situated  between  the  layers  of  mediastinum  and  above  the  ojsophagus,  sometimes  becomes 
so  voluminous  that  its  weight  impedes  rumination,  especially  wlien  the  animal  is  lying.  The 
bolus  of  food  is  prevented  from  ascending  into  the  oesophagus,  and  this  may  become  a  frequent 
and  periodic  cause  of  indigestion.) 


THE  GREAT  LYMPHATIC   VEIN. 


733 


which,  near  its  termination,  again  subdivides  into  four  vessels  that  open  separately,  two  to  the 
right  and  two  to  the  left,  in  the  usual  place. 

"  This  variety  Is  the  most  remarkable  and  complicated  of  all  those  observed  in  the  domesti- 
cated animals. 

Pig.— "The   thoracic  duct   of  the  Pig,  usually  single   throughout  its  whole  extent,  ia 


Fig:  405. 


VARIETIES    IN    THE    THORACIC    DUCT    OF    THE    OX. 

sometimes  divided,  at  from  1  to  1|  inches  from  its  entrance,  into  two  branches  which  soon 

reunite  m  an  oval  dilatation ;  this,  after  receiving  the  vessels  from  the  head,  neck,  and  limbs 

opens  towards  the  extremity  of  the  left  jugular.  ' 

Carnivora.— "In  the  Dog,  the  receptaculum  chyli  is  enormous;  in  shape  it  is  ovoid,  and 

49 


734  THE  CIRCULATORY  APPARATUS   OF  BIRDS. 

is  prolonged  between  the  pillars  of  the  diaphragm  into  the  thoracic  cavity.  Tlie  thoracic  doct 
of  this  animal  generally  resembles  that  of  the  Pig.  Yet  it  sometimes  offers  in  its  course  and 
termination  very  numerous  variations;  Rudbecky  has  noticed  a  bifurcation  above  the  heart, 
and  another  bifurcation  the  branches  of  wliich  anastomose  with  each  other  several  times. 
Swammerdam  and  Steno  have  figured  numerous  irregular  anastomotic  divisions  towards  the 
middle  of  a  single  canal,  to  its  point  of  departure.     These  old  authors  have  indicated  and 

Fig.  406. 


THORACIC    DUCT   OF    SMALL   RUMINANTS. 


represented  double  and  triple  junctions  of  different  forms.  Lastly,  Bilsius  has  shown  an  arch, 
or  rather  a  very  remarkable  ring,  at  the  entrance  of  the  vessel,  at  its  junction  with  the 
lymphatic  vessels  of  the  neck  and  anterior  limbs,  and  which  is  more  or  less  analogous  to  that 
which  I  have  observed  on  several  occasions  in  the  Horse,  Pig,  and  Cat."  • 


CHAPTER  III. 

THE  CIRCULATORY  APPARATUS  OP  BIRDS. 

We  will  briefly  examine  the  characteristics  of  the  different  portions  of  the 
circulatory  apparatus — the  heart,  blood-vessels,  and  lymphatic  vessels — of  Birds. 

Article  I. — The  Heart. 

The  heart,  in  Birds,  is  situated  quite  at  the  entrance  to  the  chest,  in  the 
middle  line,  and  is  contained  in  a  pericardium  that  adheres  to  the  posterior 
diaphragmatic  septum  and  the  cervical  reservoir.  In  the  domesticated  species, 
it  has  the  form  of  an  acute  cone,  the  base  of  which  is  surmounted  by  a  less 
distinct  auricular  mass  than  in  the  Mammalia. 

Internally  it  has  four  cavities.  The  right  ventricle  is  more  crescent-shaped 
than  in  Solipeds,  and  in  a  manner  envelops  the  left  ventricle  in  front  and  to  the 
right ;  it  does  not  reach  the  point  of  the  heart.  The  auricular  valve  is  not 
tricuspid,  and  offers  a  very  remarkable  arrangement.  "  This  valve,  in  fact, 
instead  of  being  formed  as  usual  by  membranous  curtains,  with  margin  retained 
by  cords  fixed  to  the  walls  of  the  ventricles,  is  composed  of  a  wide  muscular  leaf 
which  appears  to  be  a  portion  of  the  inner  wall  of  the  ventricle  detached  from 
the  interventricular  septum.  This  septum  is  convex,  and  the  auriculo-ventricular 
orifice  is  situated  in  the  space  comprised  between  it  and  the  muscular  valve  in 
'  G.  Colin,  op.  cit. 


TEE  CIRCULATORY  APPARATUS   OF  BIRDS.  735 

question  ;  so  that  when  the  latter  contracts  at  the  systole,  it  is  applied  against 
this  septum  and  closes  the  passage."  ^ 

There  is  nothing  particular  to  note  with  regard  to  the  left  ventricle,  the  walls 
of  which  are  likewise  thicker  than  those  of  the  right. 

The  auricles  have  a  kind  of  diverticulum  or  sinus,  where  the  veins  that  open 
into  each  of  these  cavities  unite. 

Article  II.— The  Arteries. 

The  aorta  of  Gallinaceous  Birds  ascends  beneath  the  lower  face  of  the  right 
lung,  then  turns  abruptly  backwards  and  a  little  to  the  left.  It  attains  the 
middle  line  towards  the  anterior  extremity  of  the  kidneys,  and  in  this  situation 
it  reaches  the  sacral  vertebrae,  where  it  divides  into  three  branches — the  arteries 
of  the  pelvic  limbs,  and  the  middle  sacral  artery. 

Close  to  its  origin,  the  aorta  gives  off  the  hrachio-cephalic  (or  innominate) 
trunks.  With  the  Fowl  this  name  is  perfectly  correct,  as  they  both  furnish 
vessels  to  the  wings  and  head.  The  right  passes  upwards  and  forwards,  is 
inflected  backwards  at  the  first  rib,  and  continued  on  the  lower  face  of  the  wing 
by  the  humeral  artery.  It  throws  off  a  thoracic  artery,  the  volume  of  which  is 
in  relation  with  that  of  the  pectoral  muscles ;  this  artery  emits  superficial 
branches  that  form  in  the  skin  of  the  abdomen,  with  other  vessels,  a  very  rich 
plexus  named  by  Barkow  the  rete  mirabile  of  incubation.  It  afterwards  gives 
off  a  cephalic  trunk,  from  which  arise  the  ascending  cervical,  vertebral,  and  right 
carotid  artery.  The  left  brachio-cephalic  trunk  has  the  same  distribution  as  the 
right,  a  slight  difference  only  being  observed  in  its  direction ;  on  leaving  the 
thoracic  cavity  it  describes  a  small  S  curvature. 

The  carotid  arteries  exhibit  a  somewhat  curious  arrangement.  Each  springs 
from  a  corresponding  brachial  trunk  ;  and,  placed  at  first  on  the  sides  of  the  neck, 
they  make  a  curve,  with  convexity  anterior,  and  gain  the  middle  line  by  passing, 
the  right  above  the  oesophagus,  the  left  above  the  trachea.  They  remain  beside 
each  other,  beneath  the  longus  colli,  from  the  second  last  to  the  second  cervical 
vertebrae,  where  they  separate  at  an  acute  angle  and  reach  the  border  of  the  jaw, 
terminating  there  in  two  branches— the  internal  and  external  carotid  arteries. 

The  other  collateral  branches  furnished  by  it  are  :  1,  The  intercostal  arteries. 
These  may  arise  from  the  subcostal  branches  which  are  parallel  to  the  aorta ; 
thus,  in  the  Fowl,  there  is  a  common  descending  intercostal  which  proceeds  from 
the  vertebral,  and  a  common  ascending  intercostal  that  leaves  the  aorta  as  it  passes 
into  the  abdomen.  2.  The  codiac  trunk,  which  commences  at  the  middle  of  the 
lower  face  of  the  lung,  and,  descending  obliquely  backward,  reaches  the  posterior 
aspect  of  the  liver.  It  divides  into  several  ramuscules,  of  which  there  are  three 
principal  vessels  ;  a  very  fine  one  goes  to  the  spleen  ;  a  left  or  middle  one  passes 
to  the  gizzard  along  the  proventriculus  ;  the  third,  more  voluminous,  is  directed 
to  the  right  side,  gives  a  twig  to  the  liver,  and  is  continued  by  a  long  pancreatico' 
duodenal  branch  that  joins  the  extremity  of  the  loop  which  the  intestine  forms 
at  its  origin.  3.  The  anterior  or  superior  mesenteric,  which  arises  at  a  short  dis 
tance  behind  the  coeliac  trunk,  enters  the  mesentery,  and  is  directed  backwards, 
describing  a  curve  with  convexity  antero-inferior,  and  which  emits  twigs  to  the 
intestine.     4.  The  spermatic  or  ovarian  arteries.     The  inferior  or  posterior  mesen- 

'  Milne-Edwards,  Lemons  sur  la  Physiologie  et  V Anatomic  Comparee  de  VEomme  et  det 
Animaux,  vol.  iii. 


736  THE  CIRCULATORY  APPARATUS  OF  BIRDS. 

teric  leaves  the  subsacral  artery,  and,  by  some  ramuscules,  reaches  the  rectum  and 
cloaca. 

Shortly  before  its  termination  in  three  branches,  the  aorta  gives  off  an  artery 
that  crosses  the  middle  portion  of  the  kidneys,  leaves  the  abdominal  cavity,  and 
becomes  distributed  to  the  anterior  muscles  of  the  thigh,  after  detaching  the 
qngastrk  artery.  The  latter  proceeds  forward,  beneath  the  skin  of  the  abdomen, 
and  anastomoses  with  the  ramifications  of  the  thoracic  artery. 

The  arteries  of  the  pelvic  limbs — the  femoral  or  iliac,  in  passing  above  the 
kidneys,  furnish  the  renal  arteries  ;  they  then  leave  the  pelvis  by  the  sacro-sciatic 
foramen,  immediately  behind  the  coxo-femoral  articulation.  Placed  beneath  the 
muscles  on  the  posterior  face  of  the  thigh,  in  following  the  branches  of  the 
lumbo-sacral  plexus  as  far  as  the  femoro-tibial  articulation,  they  are  then  con- 
tinued by  the  popliteal  vessels.  These  arteries  throw  off  articular  ramuscules, 
the  nutrient  artery  of  the  tibia,  and  a  long  branch  to  the  muscles  on  the  posterior 
aspect  of  the  leg  ;  they  are  placed  in  the  groove  resulting  from  the  junction  of 
the  tibia  and  fibula,  and  pass  through  the  osseous  interspace  to  form  the  anterior 
tibial  arteries. 

The  yniddle  sacral  continues  the  aorta  to  the  bottom  of  the  pelvis  ;  when  it 
arrives  below  the  last  coccygeal  vertebra,  it  forms  a  kind  of  arch,  the  ramifications 
of  which  are  distributed  among  the  muscles  and  quills  of  the  tail. 

Aeticle  III. — The  Veins. 

As  in  Mammals,  the  veins  are  distinguished  as  belonging  to  the  great  and 
lesser  circulation. 

The  veins  of  the  great  circulation  are  collected  into  three  trunks  that  open 
into  the  right  auricle  of  the  heart ;  there  are  two  anterior  vena,  cavm  and  one 
posterior  vena  cava.  They  enter  a  particular  compartment — a  kind  of  sinus — in 
the  auricle. 

The  anterior  vence,  cavce  collect  the  blood  from  the  subclavian  arteries  and 
those  of  the  head.  The  jugular  veins,  which  are  their  principal  branches,  are 
not  the  satellites  of  the  carotid  arteries,  as  in  the  larger  domesticated  animals  ; 
they  are  superficial  and  situated  on  the  sides  of  the  trachea  ;  while  the  carotids 
are  placed  in  the  middle  line,  beneath  the  longus  colli.  They  are  not  of  the 
same  calibre  in  all  species,  the  right  jugular  being  more  voluminous  than  the 
left ;  there  is  always,  however,  a  transverse  anastomosis  between  the  two  jugulars, 
below  the  base  of  the  cranium. 

The  posterior  or  inferior  vena  cava  commences  at  the  anterior  extremity  of 
the  kidneys,  and  passes  forwards,  traversing  the  right  portion  of  the  liver, 
receiving  the  hepatic  veins,  and  enters  the  right  auricle. 

Among  the  branches  forming  it  may  be  cited  the  femoral  or  iliac  veins. 
These  vessels  do  not  accompany  the  corresponding  arteries,  and  therefore  do 
not  enter  the  pelvic  cavity  by  the  sacro-sciatic  foramen,  but  pursue  a  course 
analogous  to  that  described  for  these  vessels  in  Solipeds,  in  passing  beneath  the 
crural  arch. 

In  Birds  furnished  with  a  crest  and  mandibles,  the  skin  of  the  head  is  provided 
wit"h  an  excessively  rich  vascular  plexus. 

Article  IV. — The  Lymphatics. 
Birds  possess  lymphatic  vessels  and  glands.  The  latter  are  few,  and  are  scarcely 


THE  CIRCULATORY  APPARATUS  OF  BIRDS.  737 

met  with  elsewhere  than  in  the  cervical  region ;  the  former  are  abundant  in 
the  viscera,  and  unite  in  such  a  manner  as  to  form  tivo  thoracic  ducts.  These 
ducts  commence  at  the  coeliac  trunk,  and  pass  along  the  lower  face  of  the  lung, 
receiving  the  lymphatics  of  that  organ  and  those  of  the  wings,  and  finally  open 
into  the  jugular  veins,  a  little  in  front  of  their  union  with  the  axillary  veins. 
A  transverse  branch  forms  a  communication  between  the  two  thoracic  ducts, 
towards  their  termination. 


BOOK  YI. 

APPARATUS    OF   INNERVATION. 

FIRST  SECTION. 

THE   NERVOUS    SYSTEM   IN   GENERAL. 

The  functions  of  the  instruments  which  we  have  just  described,  suffice  in  them- 
selves to  maintain  nutrition — the  locomotory  acts  which  permit  the  animal  to 
seek  its  food  and  to  introduce  it  into  its  organism,  the  elaboration  and  absorption 
of  the  assimilable  materials  of  the  alimentary  mass  in  the  interior  of  the  digestive 
cavity,  the  circulation  of  the  reparative  fluids  in  the  economy,  and  the  depuration 
and  revivification  of  these  fluids  by  the  action  of  the  lungs  and  the  kidneys  ; 
so  that  nothing  more  is  required  to  constitute  the  conditions  necessary  for  the 
manifestation  of  the  nutritive  phenomena. 

Besides  the  apparatus  necessary  to  carry  on  the  functions  of  nutrition,  how- 
ever, there  is  needed  an  excitory  system  which  will  move  them  from  their  inertia, 
and  a  regulating  system  to  direct  their  special  activity.  These  two  systems  are 
found  in  the  apparatus  of  innervation.  Stimulated  by  the  nervous  system,  the 
properties  of  the  apparatuses  of  nutrition  no  longer  remain  in  a  latent  state, 
but  manifest  themselves  by  their  usual  results. 

Thanks  to  the  nervous  system,  the  animal  acquires  all  the  attributes  of  what 
it  has  become  habitual,  after  Bichat,  to  term  animal  life — that  is,  sensibility, 
volition,  instinct,  and  intelligence. 

The  perceptive  centre  which  receives  the  stimuli  developed  at  the  periphery 
of  organs,  or  in  their  substance  ;  the  excitatory  centre  which  induces  motion  in 
all  the  other  tissues  ;  the  seat  of  the  instinctive  and  intellectual  faculties,  charged 
with  numerous  and  important  functions — the  apparatus  of  innervation  presents 
itself  as  a  most  attractive  study.  We  will  commence  by  giving  a  general  and 
succinct  idea  of  its  conformation,  structure,  properties,  and  functions,  before 
undertaking  the  special  description  of  the  different  parts  composing  it. 

General  Conformation  of  the  Nervous  System. 

The  apparatus  of  innervation  comprises  a  central  and  a  peripheral  portion. 

The  first  represents  a  very  elongated  mass  lodged  in  the  spinal  canal,  and 
expanded  at  its  anterior  extremity,  which  occupies  the  cranial  cavity.  This  is 
named  the  cerebrospinal  axis  or  centre. 

The  second  consists  of  a  double  series  of  ramescent  branches,  which  are  given 
off  laterally  from  the  central  mass,  to  be  distributed  to  all  parts  of  the  body ; 
these  branches  are  the  nerves. 

The  Cerebko-Spinal  Axis. — The  axis,  properly  so  called,  lodged   in  the 


THE  NERVOUS  SYSTEM  IN  GENERAL.  739 

vertebral  canal,  forms  the  spinal  cord.  It  is  a  large  white  cord,  terminating  in 
a  point  at  its  posterior  extremity,  and  giving  off,  at  each  intervertebral  foramen, 
one  of  those  nerve-branches  which,  collectively,  represent  the  peripheral  portion 
of  the  apparatus  of  innervation. 

The  expanded  extremity  enclosed  in  the  cranium  is  named  the  encephalon  (or 
brain).  More  complicated  in  its  conformation  than  the  spinal  cord,  this  portion 
is  divided,  as  we  shall  see,  into  four  parts  :  1.  A  white  peduncle,  the  continuation 
of  the  spinal  cord.  2.  Three  grey-coloured  ovoid  masses,  one  of  which  is  posterior, 
the  other  two  being  anterior,  and  placed  symmetrically  side  by  side.  This 
medullary  prolongation  gives  off,  right  and  left,  like  the  cord  itself,  nerve- 
branches  destined  almost  exclusively  to  the  head. 

The  Nerves. — The  nerves  are  in  the  form  of  fasciculated  cords,  issuing 
from  the  orifices  at  the  base  of  the  cranium,  or  through  the  intervertebral 
foramina,  and  passing  into  all  the  organs  by  ramifying  like  arteries,  which  they 
generally  accompany. 

All  the  nerves  arise  from  the  medullary  axis,  or  from  its  encephalic  pro- 
longation, by  radicles  more  or  less  apparent.  They  are  divided,  according  to 
the  relative  position  of  their  point  of  emergence,  into  two  great  categories — the 
superior,  arising  from  the  corresponding  face  of  the  spinal  axis  ;  the  others, 
inferior,  escaping  from  the  lower  face — a  distinction  which  is  perfectly  appre- 
ciable with  regard  to  the  cord  itself,  but  which  is  more  difficult  to  estabhsh  in  the 
encephalic  peduncle,  as  it  is  less  distinct. 

At  their  emergence  from  the  bony  canals  which  give  them  passage,  the 
radicles  of  each  nerve  always  unite  into  a  thick  common  trunk. 

In  the  majority  of  cases,  there  enter  into  the  composition  of  this  trunk  the 
nerves  or  fibres  of  the  two  orders  ;  only  a  few  nerves  are  composed  of  fibres  of 
the  one  kind,  and  these  all  belong  to  the  brain. 

At  the  origin  of  the  trunk  into  which  the  nerve  roots  are  collected,  there  is 
a  greyish  enlargement  termed  a  ganglion ;  but  this  peculiarity  belongs  exclusively 
to  the  superior  fibres. 

After  a  variable  course,  which  is  generally  short,  this  trunk  divides  into 
branches,  the  point  of  departure  for  all  the  nerves  of  the  body.  Among  these 
branches,  those  which  are  expended  in  the  apparatuses  of  animal  life  are  pairs, 
and  perfectly  alike  on  both  sides  of  the  body.  Those  of  the  organs  of  nutrition 
are  composed  at  first  of  an  almost  symmetrical  double  chain,  placed  beneath  the 
spinal  column,  the  elements  of  which  are  borrowed  from  nearly  all  the  nerve 
trunks  issuing  from  the  cerebro-spinal  axis  ;  in  proceeding  to  their  destination, 
their  distribution  is  most  irregularly  complicated.  As  they  offer  on  their  course 
&  great  number  of  ganglia  similar  to  those  we  have  already  mentioned,  they  are 
called  ganglionie  nerves  ;  they  are  also  designated  the  net'ves  of  organic  or  vegetative 
life,  while  the  others  are  named  the  nerves  of  animal  life  or  of  relation. 

Structure  of  the  Nervous  System. 

Two  particular  substances — one  greg,  the  other  white — enter  into  the  organi- 
sation of  the  nervous  apparatus.  These  two  substances  are  formed,  the  first  of 
nerve-tubes  and  united  nerve-cells  ;  the  second  of  tubes  alone. 

The  nerve-tubes  are  microscopic  elements,  composed  of  sections  or  segments 
about  a  millimetre  in  length,  joined  end  to  end.  Each  segment  {inter anyiular 
segment)  is  formed  of  a  sheath  {Schivann's  sheath) — a  thin,  homogeneous  mem- 


740 


TEE  NERVOUS  SYSTEM  IN   GENERAL. 


Fig.  407. 


DIAGRAM  OF  STRPC 
TURE  OF  XERVE 
FIBRE. 


1,  Sh 
lary 


th;  2,  medul- 
substance  of 
Schwann  ;  3,  axis- 
cylinder,  or  primi- 
tive band. 


brane,  within  which  is  a  layer  of  protoplasm  containing  a  nucleus.  The  axis  of 
the  segment  is  occupied  by  a  slender  cylindrical  stalk  {(ixis-cyUnder  of  PurTcinjey 
or  bund  of  Remak ),  the  space  between  it  and  the  protoplasm 
being  filled  by  a  viscid  opatjue  substance  {nvjeJin,  medidla, 
white  substame  of  Schwann,  or  sheath  of  the  marrow),  which 
is  stained  black  by  osmic  acid,  and  is  quickly  coagulated 
by  cold. 

The  axis-cylinder  is  not  interrupted  at  the  points  of  con- 
tact of  the  segments,  btit  passes  through  the  annular  con- 
strictions, and  runs  from  beginning  to  end  of  the  nerve. 

When  the  medulla  is  solidified,  it  is  seen  to  be  bordered 
by  two  dark  lines,  parallel  to  the  walls  of  the  nerve-tubes  ; 
this  aspect  has  caused  the  latter  to  be  named  '•  double-con- 
totired  tubes  (or  nerve-fibres)." 

All  the  nerve-tubes  do  not  possess,  at  the  same  time, 
these  three  parts,  for  the  medulla  may  be  absent :  so  that 
there  are  distinguished  medidlated  and  non-meduUated  nerve- 
fibres.     The  first,  more  or  less  thick,  are  met  with  in  the  nerve-centres,  and  at 
the  origin  and  middle  portion  of  the  nerves  ;  the  second  are  found  at  the  termi- 
nation of  nerves,  and  in  the  great  sympathetic. 

There  are  also  observed  in  the  nerves  of  organic 
life,  elongated  elements,  designa,ted  fibres  of  Iiemak,grei/ 
fibres,  and  nucleated  nervous  fibres.  These  are  pale, 
flattened  fibres,  with  parallel  borders,  and  furnished 
with  elliptical  nuclei.  Some  authorities  consider  these 
to  be  bands  of  connective  tissue,  and  not  nerve  elements. 
The  nerve-cells,  or  corpuscles,  are  voluminous,  and 
formed  by  a  mass  of  protoplasm  without  any  enveloping 
membrane,  but  in  the  midst  of  which  are  numerous 
fibrillar.  In  the  ganglia  they  are  covered  by  a  layer  of 
fibrillar  connective  tissue,  provided  with  nticlei,  which 
appear  to  furnish  them  with  a  very  thick  enveloping 
membrane.  The  nucleus,  with  one  or  two  nucleoli,  is 
often  surrounded  by  granules  of  a  brown  colour. 

The  nerve-cells  have  prolongations  or  jwles,  the 
nmnber  of  which  varies  from  one  to  five.  Cells  with 
only  one  prolongation  are  named  unipolar ;  those  which 
have  two  are  bipolar ;  and  those  which  have  a  greater 
number  are  designated  multipolar.  In  Mammalia,  one 
of  these  prolongations — nerve  prolongation,  prolongation 
of  Deiters — in  the  spinal  cord  establishes  relations  be- 
tween a  cell  and  nerve-tube  ;  the  others  are  of  a  proto- 
plasmic nature,  and  ramify — these  ramifications  joining 
those  of  neighbouring  cells. 

Such  are  the  anatomical  elements  that  enter  into  the 
structure  of  the  nervous  system. 

In  the  white  substance  of  the  cerebro-spinal  axis, 
only  medullated  nerve-tubes  of  every  size  are  found  ;  in 
the  grey  substance  are  tubes,  and  a  more  or  less  con- 
siderable number  of  nerve-cells  are  situated  alons:  their  course. 


NERVE-TUBE. 

A,  Nerve-tube  slightly  mag- 
nified :  a,  annular  con- 
striction ;  6,  nucleus  of 
the  interannular  segment; 
c,  axis-cylinder.  B,  An- 
nular constriction  and  por- 
tions of  the  interannular 
sesments  highly  magnified 
(prepared  with  osmic  acid, 
which  colours  the  myelin 
black) :  a',  annular  con- 
striction, or  node  of  Ran- 
vier ;  h',  nucleus  of  the 
interannular  segment ;  c', 
external  nucleus  of  the 
sheath. 


THE  NERVOUS  SYSTEM  IN  GENERAL. 


741 


To  these  two  elements  is  added  a  large  quantity  of  blood-vessels,  which  are 
incomparably  more  abmidant  in  the  grey  than  in  the  white  substance.     It  must 


Fig.  409. 


MULTIPOLAR  OR   STELLATE  GANGLIONIC   NERVE-C^-LL,  WITH   ONE   OP   ITS   PROLONGATIONS 

a,  Becoming  continuous  with  the  axis-cylinder  of  a  double-coutoured  nerve-fibre,  6. 


Fig.  411. 


Fig.  410. 


SEVERAL   MULTIPOLAR   NERVE-CELLS. 

be  added  that  in  the  grey  substance  the  chief  ele- 
ments are  these  ganglionic  cells,  supported  or  bound 
together  by  neuroglia,  distinct  from  connective  tissue. 

In  the  nerves,  the  elementary  tubes  are  alone  met 
with  ;  they  are  disposed  in  long  bundles,  which  are 
collected  into  successively  increasing  fasciculi.  A 
cellulo-vascular  envelope — the  neurilemma  (or  peri- 
neurium)— binds  all  these  fasciculi  into  a  single  cord, 
and  forms  a  special  sheath  around  each  of  them. 
The  details  of  their  organization  will  be  referred  to 
hereafter. 

It  is  admitted  that  the  ganglionic  nerves,  or 


PYRAMIDAL  CELL  OF  THE  GREY 
SUBSTANCE  OF  THE  BRAIN 
CORTEX. 

N,  Nucleus;  a,  a,  small  ramified 
protoplasmic  prolongations ; 
c,  prolongations  of  the  base 
of  Deiters  (bringing  the  cells 
into  communication  with  the 
axis-cylinder  of  the  nerve- 
fibre). 


742 


TEE  NERVOUS  SYSTEM  IN  GENERAL. 


nerves  of  organic  life,  possess  a  greater  quantity  of  slender  tubes  than  the  others. 
These  tubes  are  commonly  designated  as  the  organic  nerve-fibres.  They  also 
contain  fibres  of  Remak. 

In  the  spinal  ganglia^  the  cells  are  joined  to  the  nerve-tubes.     It  has  been 


Fig.  412. 


Tig.  413. 


MICROSCOPIC   GANGLION   PROM   HEABT 
OF  FROG. 


BIPOLAR  GANGLIONIC  CELLS  AND  NERVE- 
FIBRES,  FROM  6ANGLI0N  OF  FIFTH  PAIB 
IN    LAMPREY. 


shown,  by  dissection  and  microscopical  observation,  that  the  corpuscles  com- 
posing the  ganglia  or  expansions  at  the  origin  of  the  nerves,  are  all  attached  ta 
the  superior  fibres.     The  other  tubes  have  none. 

In   the  cerebrospinal  axis,  the  two  substances  are  equally  associated,  and 


Fig.  415. 


STELLATE  NERVE-CELL,  FROM  THE  NUCLEUS 
CERVICIS  CORNU  (POSTERIOR  VESICULAR 
column)  OF  A  FCETUS  OF  SIX  MONTHS. 
MAGNIFIED    420    DIAMETERS. 


STRUCTURE    OP   GANGLIONIC    NERVE-CELL. 

A,  According  to  Beale  ;  B,  according  to  Arnold. 
a.  Straight  fibre ;  6,  double  spiral  fibre ;  c, 
capsule  of  connective  tissue. 


connected  with  each  other  by  a  prolongation  (or  single  pole)  which  is  inflected 
in  such  a  manner  as  to  resemble  a  T  or  Y  (cells  with  T-shaped  fibres),  but  in  a 
variable  manner,  according  to  the  region.  In  the  spinal  cord  and  its  prolonga- 
tions into  the  encephalon,  the  grey  substance  occupies  the  interior  ;  while  it  is 
spread  over  the  exterior  of  the  encephalic  lobes,  and  envelops  the  white  substance. 


.  THE  NERVOUS  SYSTEM  IN  GENERAL.  743 

Properties  and  Functions  of  the  Nervous  System. 

It  would  require  a  long  chapter  to  do  justice  to  this  subject,  and  we  could 
not  venture  on  it  here  without  going  beyond  our  domain.  We  will,  however, 
offer  some  remarks  on  those  notions  connected  with  the  properties  and  functions 
of  the  nervous  system,  which  are  strictly  necessary  for  the  comprehension  of  the 
anatomical  facts  to  be  hereafter  dealt  with. 
And  first  as  to  the  properties  of  the  nerves. 

"We  will  suppose  the  spinal  canal  to  be  opened  in  the  lumbar  region,  and  the 
cord  laid  bare  in  a  living  animal.  If  we  cut  across  the  inferior  roots  of  one  of 
the  spinal  nerves,  and  compress  with  a  pair  of  forceps  one  or  more  of  these  roots 
by  the  end  remaining  attached  to  the  cord,  nothing  results  to  denote  that  this 
irritation  has  had  any  influence  on  the  organism.  But  if,  instead  of  operating 
on  the  central  or  attached  end  of  these  divided  roots,  we  excite  the  peripheral 
end  which  is  continued  by  the  trunk  of  the  nerve,  contraction  of  the  muscles  of 
the  limb  which  receives  the  fibres  coming  from  the  irritated  roots  is  produced. 

The  muscular  tissue  comports  itself  as  if  the  irritation  were  directly  applied 
to  it ;  so  that  the  nerve  has  served  as  the  medium  of  communication.  It  has 
received  the  stimulus,  it  has  been  excited  by  it,  and  it  has  conducted  this  to  the 
muscles  to  which  the  nerve  is  distributed.  This  double  reaction  produced  by 
the  nerve-tubes  is  their  special  attribute,  their  essential  property.  With  Vulpian, 
we  might  designate  it  collectively  by  the  term  neurility ,-  but  it  is  necessary  to 
distinguish  the  two  modes  it  affects,  by  naming  the  property  of  being  impressed 
by  stimuli  as  the  excitahility  of  the  nerve,  and  nervous  conductibility  its  aptitude 
to  convey  the  excitations  which  have  impressed  it. 

The  same  experiment  may  be  repeated  on  the  upper  roots.  It  is  then  per- 
ceived that  the  pinching,  which  produces  no  effect  at  the  peripheral  extremity, 
causes  pain  when  applied  to  the  central  end.  The  animal  testifies  immediately, 
by  cries  and  movements,  that  it  feels  the  touch  of  the  forceps.  But,  as  will  be 
mentioned  in  a  moment,  the  impression  resulting  from  this  touch  has  only  been 
perceived  by  the  brain  ;  it  has  therefore  been  conducted  to  the  spinal  cord  by  the 
stimulated  nerve-fibres,  and  then  to  the  brain  by  the  fibres  of  this  medullary  axis. 
In  putting  to  one  side,  for  the  moment,  the  part  played  by  the  latter  in  the 
phenomenon  now  analyzed,  it  will  be  seen  that  the  superior  fibres  of  the  spinal 
nerves  enjoy  the  same  attributes  as  the  inferior  ;  neurility  is  their  appanage,  and 
this  property  is  apparent  in  its  two  qualities — excitahility  and  conductiMlity . 
Only  here  the  latter  property  is  exercised  in  a  centripetal  sense  ;  while  in  the  first 
instance  it  acted  in  a  centrifugal  sense.  But  it  must  not  be  assumed  that  these 
two  conductibilities  are  essentially  distinct.  The  physiological  differences  by 
which  they  appear  to  be  distinguished,  seem  to  belong  to  the  difference  in  the 
relations  of  the  nerve-fibres  with  the  organs  to  which  they  are  distributed.  In 
one  case  (that  of  the  centrifugal  nprves),  the  organs  of  reaction — the  muscles — 
are  placed  at  the  peripheral  extremity  of  the  nerves  ;  in  the  case  of  the  centripetal 
nerves,  the  organs  of  reaction — the  brain  and  spinal  cord — are  found  at  the 
central  extremity  of  the  nerve-fibres.  This  theory  of  the  unity  of  nervous 
conductibiUty  has,  moreover,  been  proved  to  be  correct  by  the  researches  of 
Philipeaux  and  Vulpian,  who  have  utihzed  the  experiment  of  Gluge  and  Thier- 
nesse  on  the  union  of  the  central  end  of  the  lingual  (centripetal),  with  the 
peripheral  end  of  the  hypoglossal  nerve  (centrifugal)  ;  and  recently  by  Bert,  in 
grafting  the  tail  of  the  Rat  into  that  animal's  back. 


744  THE  NERVOUS  SYSTEM  IN  GENERAL. 

It  is  easy  to  demonstrate  that  this  double  property  of  conduction  belongs  to 
all  the  nerve-fibres  arising  from  the  cerebro-spinal  axis — centripetal  conductihility 
being  peculiar  to  the  superior  fibres,  and  centrifugal  conduct ibility  to  the  inferior 
ones.  It  is  also  demonstrated  that  this  conduction  acts  in  either  one  sense  or 
the  other,  whatever  may  be  the  part  of  the  nerves  so  stimulated  ;  as  the  nerve- 
tubes  possess,  throughout  their  whole  length,  the  property  of  excitability  and 
conductihility. 

The  fibres  with  centrifugal  conductihility  are  the  motor  nerves ;  those  with 
centripetal  conductihility  are  the  sensitive  nerves.  But  sensibiUty  does  not  exist 
only  in  the  filaments  of  the  superior  roots  ;  it  has  also  been  remarked  in  the 
lower  roots,  and  these  owe  it  to  the  filaments  which  are  given  off  from  the  roots 
with  centripetal  conductihility,  and  which  return  to  the  nervous  centres  by  the 
motor  roots.  The  sensitiveness  evinced  by  these  motor  roots  is  named  recurrent 
sensibiUty.  This  sensitiveness  has  also  been  demonstrated  on  the  peripheral  end 
of  the  sensory  nerves  of  the  limbs  and  face  (xlrloing  and  Tripier). 

The  anatomical  and  physiological  characters  of  the  nerves  persist  as  long  as 
they  are  in  communication  with  the  centres.  If  they  are  divided  at  any  part  of 
their  course,  the  portion  attached  to  the  spinal  axis  still  preserves  its  properties  ; 
but  that  situated  beyond  the  section — the  peripheral  end,  as  it  is  named — 
degenerates,  and  becomes  incapable  of  conducting  the  sensitive  impressions,  or 
of  transmitting  the  voluntary  motor  stimuli. 

Now  as  to  the  spinal  cord. 

Does  the  medullary  axis,  which  has  apparently,  in  great  part,  the  structure  of 
a  nerve,  possess,  like  the  latter,  excitahility  and  conductihility — those  two  essential 
properties  of  the  peripheral  nervous  system  ? 

Excitability  is  entirely  absent  in  the  grey  substance.  On  the  surface  of  a 
section  of  the  cord,  the  slightest,  or  even  the  most  intense  irritation  of  this  por- 
tion, produces  no  reaction.  In  the  white  substance,  this  excitability  can  only  be 
easily  rendered  evident  on  the  surface  of  the  upper  bundles  or  fasciculi,  where 
it  is  exquisite.  With  regard  to  the  always  limited  reactions  observed  when  the 
stimulations  are  made  on  the  deep  part  of  the  fasciculi,  it  is  difficult  to  say  if 
they  result  from  the  excitability  of  the  spinal  cord,  or  that  of  the  nerve-roots 
which  traverse  the  white  substance. 

Nervous  conductihility  is  certainly  one  of  the  attributes  of  the  spinal  cord  ; 
the  transmission  of  stimuli  of  the  sensitive  nerves  to  the  brain,  and  the  voluntary 
movements  that  result  from  stimulation  of  the  motor  nerves,  demonstrate  that 
the  necessary  medium  between  the  nerves  and  brain — the  spinal  cord — possesses 
conductihility.  But  the  spinal  cord  may  act  as  a  nerve-centre,  and  the 
foUowin^f  experiment  irrefutably  demonstrates  it. 

I  will  suppose  that  an  animal  has  had  its  spinal  cord  cut  across  in  the  lumbar 
region,  and  I  excite,  by  pinching,  one  of  the  superior  roots  remaining  intact  on 
the  caudal  portion.  The  stimulus  cannot  be  conducted  to  the  brain,  as  this 
part  is  isolated  from  it ;  and  yet  movements  take  place  in  the  muscles  of  the 
posterior  limbs.  Does  it  happen  that,  after  section  of  the  medulla,  the  conductive 
property  of  the  nerve-fibres  which  arise  superiorly,  is  interverted  and  changed 
into  centrifugal  conductihility  ?  No  ;  for  after  the  transverse  section  of  these 
roots,  the  irritation  of  their  central  end  produces  exactly  the  same  effects.  It 
must  be,  therefore,  that  the  stimulation  had  first  reached  the  medulla,  and  was 
then  transmitted  by  it  to  the  muscles  by  means  of  the  centrifugal-current  fibres. 
And  this  is  really  what  occurred ;  section  of  the  whole  of  these  fibres  of  the 


TEE  NERVOUS  SYSTEM  IN  GENERAL.  745 

spinal  cord  hindered  the  manifestation  of  all  movement  in  the  muscles,  when  the 
superior  roots  were  touched.  There  is,  as  has  been  said,  reflexion  in  the  substance 
of  the  cord,  on  to  the  inferior  roots,  from  the  UTitation  due  to  this  pinching  ; 
the  property  which  permits  the  medullary  axis  to  act  in  this  manner  is  named 
the  reflex  power.  It  may  be  remarked  that,  if  we  suppose  for  a  moment  the 
superior  and  inferior  nerve-roots  to  be  united  in  an  arch  in  the  substance  of 
the  spinal  cord,  this  reflex  property  would  be  nothing  more  than  the  nervous  con- 
ductibility  itself  operating  precisely  in  the  direction  special  to  each  kind  of  nerves. 

This  union  really  exists  ;  only  the  nerve-roots  are  not  in  communication, 
except  through  the  medium  of  the  cells  in  the  grey  substance,  in  which  the 
sensitive  is  changed  into  motor  excitability. 

The  reflex  power  is  extinct  immediately  after  death  occurs  in  Mammals, 
but  it  may  last  for  several  hours,  or  even  for  a  day,  in  a  decapitated  animal  in 
which  asphyxia  has  been  averted  by  pulmonary  insufflation.  The  extent  of  the 
movements  it  determines  is  in  relation  to  the  intensity  of  the  stimulus  which  is 
the  primary  cause  of  it ; — merely  local  when  they  result  from  a  slight  irritation, 
these  movements  may  take  place  in  all  the  muscles  of  the  body  after  powerful 
stimulation. 

Let  us  now  inquire  into  the  attributes  of  the  encephalon. 

Excitability  has  been  determined  in  several  points  of  the  medulla  oblongata, 
and  in  the  interior  of  the  cerebellum.  Physiologists  have  long  denied  it  to  the 
surface  of  the  latter,  and  to  the  substance  of  the  cerebral  hemispheres ;  but 
within  the  last  twenty  years,  Fritsch  and  Hitzig,  Ferrier,  Carville  and  Buret,  and 
others,  have  demonstrated  that  several  points  of  the  cerebral  and  cerebellar  cortex 
are  excitable  by  electricity.  The  brain  possesses  conductibility,  because  the  grey 
substance  composing  it  is  the  receiver  of,  and  the  point  of  departure  for,  all  the 
excitations.  In  fine,  the  encephalic  mass  should  possess  neurility  like  the  nerves, 
but  this  general  property  is  more  or  less  modified.  What  more  particularly  dis- 
tinguishes the  encephalon,  is  its  action  as  a  sensitivo-motor  centre ;  in  it  arrive 
the  stimuli  from  the  sensitive  nerves,  and  there  they  are  felt  and  considered. 
In  the  brain  arise  the  motor  excitations  which  result  in  spontaneous  voluntary 
movements. 

In  an  animal  paralyzed  by  division  of  the  cord  at  the  occipito-atloid  articu- 
lation, and  in  which  death  has  been  prevented  by  artificial  respiration,  observation 
demonstrates  that  sensibility  and  spontaneous  motricity  are  preserved  in  the 
head,  the  nerves  of  which  are  in  direct  communication  with  the  brain.  Pinch 
the  upper  lip,  and  the  creature  testifies  by  the  movements  of  this  part  that  it  feels 
pain.  Pass  the  finger  to\^ards  the  eye,  and  the  eyelids  are  twinkled  and  closed — 
a  proof  that  the  animal  sees  objects,  appreciates  the  distance  which  separates  it 
from  them,  and  tries  to  remove  tlie  eye  from  their  contact.  More  striking  still, 
the  animal  feels  hungry,  and  endeavours  to  satisfy  this  craving  by  seizing  the 
food  within  its  reach,  and  masticating  and  swallowing  it.  After  this  demon- 
stration, it  is  no  longer  possible  to  doubt  that,  if  an  animal  feels,  it  is  by  the 
brain,  and  if  it  wills.,  it  is  also  by  the  brain. 

But  sensibility  and  volition  do  not  constitute  the  only  attributes  of  the  brain  ; 
for  it  is  the  seat  of  other  manifestations  not  less  interesting — those  of  the  instincts 
and  inteUigence. 

The  brain  also  contains  several  special  motor  and  sensory  centres,  the  exist- 
ence of  which  modern  physiology  and  pathology  have  completely  established. 
These  centres  are  situated  in  or  on  the  surface  of  different  parts  of  the  organ. 


746  TEE  NERVOUS  SYSTEM  IN  GENERAL. 

To  sum  up,  the  nerves  possess  a  single  physiological  property— nmrt/^. 
This  is  manifested  by  excitability  and  by  centripetal  conductibility  in  the  nerves, 
the  roots  of  which  are  uppermost,  centrifugal  conductibiliti/  in  the  nerves  with 
inferior  roots. 

The  spinal  cord  is  inexcitable  in  its  grey  substance,  but  is  excitable  on  the 
surface  of  its  superior  fasciculi,  and  with  difficulty  so  in  the  remainder  of  its 
white  substance.  It  serves  as  the  organ  of  transmission  between  the  brain  and 
the  nerve-roots  ;  and  is,  in  addition,  endowed  with  rejlex  power. 

The  brain  is  endowed  with  a  special  activity,  to  which  is  due  sensibility^ 
motUity,  and  volition,  and  the  manifestations  of  instinct  and  intelligence. 

It  remains  to  examine  the  nature  of  the  influence  the  nervous  system  exer- 
cises on  the  other  apparatuses,  through  the  properties  we  know  it  to  possess.  But 
here  again  we  must  limit  ourselves  to  principles. 

Since  Bichat's  time,  it  has  been  agreed  to  divide  into  two  great  classes  those 
functions  which  maintain  the  life  proper  of  the  individual — those  of  animal  life 
or  relation,  and  those  of  organic  or  vegetative  life. 

The  first,  which  are  exercised  with  consciousness,  comprise  the  sensorial 
functions  and  voluntary  movements ;  the  latter  are  induced  by  the  impulsion 
originating  in  the  brain,  and  transmitted  to  the  muscles  by  the  nerve-fibres  with 
centrifugal  conductibility  ;  the  former  have  for  their  object  the  appreciation,  by 
the  brain,  of  tactile  sensations — of  heat,  light,  taste,  and  smell,  by  means,  or 
through  the  instrumentality,  of  the  nerve-fibres  possessed  of  centripetal  con- 
ductibility, which  transmits  to  the  brain  the  stimulus  developed  at  their 
terminations  by  these  diverse  physical  agents. 

The  functions  of  vegetative  life — those  which  are  executed  unconsciously,  we 
may  say,  in  animals,  and  which  are  not  the  result  of  physio-chemical  forces — are 
placed  under  the  influence  of  the  reflex  power  of  the  spinal  cord.  For  example, 
the  stomach  is  empty,  and  its  mucous  and  muscular  membranes  remain  altogether 
passive — there  being  no  contractions  in  the  first,  nor  secretion  of  gastric  fluid 
in  the  second.  Food  arrives  in  its  interior,  and  immediately  its  activity  is 
developed  ;  the  muscular  tunic  executes  movements  which  produce  mixture  of 
the  food,  and  propel  it  towards  the  pyloric  orifice  ;  while  from  the  surface  of  the 
mucous  membrane  is  poured  an  abundant  solvent  secretion.  This  change  is  due 
to  the  stimulus  exercised  by  the  alimentary  particles  on  the  extremity  of  the 
centripetal  nerve-fibres,  and  which  has  been  transmitted  by  them  to  the  medullary 
axis,  there  reflected  on  the  centrifugal  fibres,  and  carried  by  these  to  the  tunics 
of  the  stomach,  the  special  functions  of  which  are  thus  brought  into  play. 

It  is  worthy  of  remark  that  the  properties  of  the  nervous  system,  which  act 
in  so  important  a  manner  on  the  organs  of  vegetative  life,  have  no  direct  influence 
on  nutrition  itself.  Destruction  of  the  nerves  in  a  certain  region  will  certainly 
derange  the  nutrition  of  its  tissues,  in  consequence  of  the  paralysis  of  the  vessels, 
but  it  is  not  destroyed.  There  is  a  very  large  category  of  organized  beings — 
vegetables,  for  instance — in  which  nutrition  is  very  active,  and  in  which  there 
is  no  nervous  system.  So  that  the  property  which  determines  the  essential 
phenomena  of  nutrition  is  an  attribute  of  living  matter. 


TEE  CEBEBBO-SPINAL  AXIS.  747 

SECOND   SECTION. 

THE    CENTRAL   AXIS   OP   THE    NERVOUS    SYSTEM. 

The  cerehro-spinal  axis  is  resolved,  as  we  have  said,  into  two  principal  sections — 
the  spinal  cord  and  the  brain.  "We  will  study  these  two  portions  in  succession — 
the  spinal  cord  first,  in  order  to  facilitate  description,  although  that  organ  only 
holds  the  second  place,  from  a  physiological  point  of  view.  The  protective  parts 
of  these  two  apparatuses  will,  however,  be  examined  before  we  proceed  further. 


CHAPTER  I. 

The  Enveloping  and  Protecting  Parts  of  the  Cerebro-spinal  Axis. 

The  cerebro-spinal  apparatus  is  lodged,  as  has  been  already  mentioned,  in  a  bony 
case — ^the  spinal  canal — which  is  prolonged  anteriorly  by  the  cranial  cavity ;  but 
it  is  protected  more  immediately  by  three  envelopes,  which  have  received  the 
names  of  chari  mater,  arachnoid,  andjsia  mater. 

The  Bony  Case  containing  the  Cerebro-spinal  Axis. 

A  knowledge  of  the  bones  which  enter  into  the  formation  of  this  protective 
case  cannot  be  acquired  without  also  knowing  the  case  itself  ;  so  that  we  dispense 
with  its  special  study  here.  We  will  allude,  however,  to  the  succinct  terms  already 
employed  in  describing  the  spijial  canal,  and  in  the  same  spirit  of  concision  will 
also  describe  what  has  hitherto  been  deferred — the  cranial  cavity. 

1.  The  Spinal  Canal. 

This  canal  communicates,  anteriorly,  with  the  cavity  of  the  cranium.  Very 
wide  at  the  atlas — to  receive  the  odontoid  process,  and  allow  those  rotatory  move- 
ments of  the  head  which  prevent  the  medulla  being  injured — the  spinal  canal 
suddenly  contracts  at  the  axis  :  it  expands  again  at  the  end  of  the  cervical  and 
commencement  of  the  dorsal  region,  where  the  medulla  presents  a  greater  volume, 
and  the  movements  of  the  spine  are  very  extensive.  Towards  the  middle  of  the 
back,  the  spinal  canal  has  its  smallest  diameter  ;  but  on  leaving  this  portion,  and 
as  far  as  the  lumbo-sacral  articulation,  it  widens  again  ;  after  which  it  rapidly 
decreases,  and  altogether  disappears  towards  the  fourth  or  fifth  coccygeal  ver- 
tebra. The  lumbo-sacral  dilatation  coincides  with  the  expansion  the  cord  shows 
at  this  point,  and  with  the  enormous  volume  of  the  nerves  lying  beside  it. 

2.  The  Cranial  Cavity  (Figs.  41,  42). 

This  is  a  very  irregular,  ovoid-shaped  box,  the  walls  of  which  are  formed  by 
the  frontal,  parietal,  occipital,  ethmoidal,  and  temporal  bones. 

It  presents  for  consideration  four  planes  and  two  extremities. 

The  superior  plane  offers  on  the  middle  line,  and  towards  its  superior  third, 
the  parietal  protuberance,  the  two  lateral  crests  of  which  concur  with  that 
eminence  in  dividing  the  cranial  cavity  into  two  compartments  :  one  posterior, 


7«  THE  CENTRAL   AXIS   OF  THE  NERVOUS  SYSTEM. 

destined  to  contain  the  cerebellum  ;  the  other  anterior,  incomparably  larger, 
lodging  the  cerebral  hemispheres,  and  divided  by  the  single  rudimentary  crest 
which  begins  at  the  falciform  process,  and  joins  the  crista  galli,  into  two  lateral 
sections — one  for  each  hemisphere.  Hereafter  we  shall  see  that  the  folds  of  the 
dura  mater  are  attached  to  this  parietal  protuberance,  and  to  the  ridges  detached 
from  it,  thus  rendering  much  more  perfect  the  partitioning  of  the  cranial  cavity. 

On  the  hiferal  planes  there  is  also  noticed  the  division  into  a  cerebellar  and 
cerebral  compartment,  due  to  the  lateral  crests  of  the  falciform  process,  which  are 
prolonged  obliquely  to  near  the  sphenoid  bone  ;  the  first  section  is  formed  by  the 
occipital  and  the  inner  face  of  the  petrous  bone  ;  the  second  by  the  squamous 
portion  of  the  temporal,  the  frontal,  and  the  great  wing  of  the  sphenoid  bone. 
Both  are  concave,  and  marked  by  digital  impressions,  as  they  also  are  on  the 
superior  plane. 

The  inferior  plane,  very  irregular,  offers  from  behind  forward  :  1.  On  the 
middle  line,  the  basilar  channel,  into  which  the  greater  portion  of  the  medulla  is 
received  ;  the  pituitary  fossa,  made  deeper  by  a  circular  fold  of  the  dura  mater, 
and  lodging  the  gland  of  that  name  ;  the  optic  fossa,  where  the  chiasma  of  the 
optic  ner\-es  is  situated.  2.  On  the  sides,  the  foramen  lacerum,  partly  closed  by 
cartilaginous  substance,  and  by  the  dura  mater  ;  the  cavernous  sinuses  and 
maxillary  fissures,  outside  which  is  remarked  a  deep  and  wide  digital  impression 
for  the  reception  of  the  mastoid  or  inferior  lobe  of  the  brain. 

The  posterior  extremity  of  the  cranial  cavity  shows  the  occipital  foramen,  by 
means  of  which  this  cavity  communicates  with  the  spinal  canal. 

The  anterior  extremity  offers,  in  the  median  plane,  the  crista  galli  process,  or 
superior  border  of  the  perpendicular  plate  of  the  ethmoid  bone  ;  on  the  sides, 
the  two  ethmoidal  f oss«  —deep  depressions  containing  the  olfactory  lobes,  and  at 
the  bottom  of  which  is  observed  the  cribriform  plate  of  that  bone. 

The  Envelopes  of  the  Cerebro-spinal  Axis. 

Preparation. — In  order  to  study  the  cerebro-spinal  axis,  the  same  preparation  as  for  the 
spinal  cord — to  be  alluded  to  hereafter  -  should  be  followed.  When  the  centres  are  freed  from 
their  bony  covering,  the  membranes  miiy  be  incised,  dissected,  and  separated  from  each  other 
— the  arrangement  of  the  sub-arachnoid  spaces  being  rendered  apparent  by  insuffliition. 

The  arrangement  of  the  cranial  dura  mater  can  be  studied  by  making  an  antero-posterior 
section  of  the  cranium  beyond  the  middle  line,  and  a  transverse  section  in  front  of  the  internal 
occipital  protubprance.  On  the  first  is  seen  the  falx  cerebri  and  pituitary  fold,  and  on  the  second 
the  tentorium  cerebelli. 

The  three  membranes  which  cover  the  cerebro-spinal  axis,  and  separate  it 
from  the  walls  of  the  bony  cavity  enclosing  it,  are  thus  designated.  Generally 
termed  meninges,  and  distinguished  as  external,  middle,  and  infernal  meninge, 
these  membranes  are  better  known  as  the  dura  mater,  arachnoid,  and  pia  mater 
— names  which  will  be  employed  in  our  description. 

The  dura  mater,  or  external  meninge,  is  a  strong  fibrous  membrane  in  contact 
with  the  walls  of  the  cranium  and  the  spinal  canal. 

The  arachnoid,  or  middle  meninge,  is  a  tunic  of  a  serous  nature,  which  resolves 
itself  into  two  layers — an  external,  applied  to  the  inner  face  of  the  dura  mater  ; 
and  an  internal,  spread,  through  the  medium  of  the  pia  mater,  over  the  cerebro- 
spinal axis,  from  which  it  is  again  separated  at  a  great  number  of  points  by  a 
particular  fluid,  the  suh-aruchnoid  (or  liqvx)r  cerebro-spinalis). 

The  pia  mater,  or  internal  meninge,  is  the  proper  envelope  of  the  central 


TEE  CEREBROSPINAL  AXIS.  749 

nervous  mass  ;  it  is  cellulo-vascular,  closely  adherent  to  the  external  surface  of 
the  mass,  attached  to  the  visceral  layer  of  the  arachnoid  by  more  or  less  dense 
connective  tissue,  between  the  meshes  of  which  is  the  sub-arachnoid  fluid. 

This  arrangement  of  the  cerebro-spinal  envelopes  permits  the  cerebro-spinal 
axis  to  be  assimilated,  to  a  certain  extent,  to  a  viscus,  and  the  bony  case  contain- 
ing them  to  a  splanchnic  cavity,  the  serous  membrane  of  which — the  arachnoid 
— is  covered  outside  its  parietal  layer  by  a  fibrous  expansion — the  dura  mater,  and 
within  its  visceral  layer  by  a  cellulo-vascular  tunic— the  pia  mater,  or  internal 
meninge. 

This  collective  view  of  the  envelopes  belonging  to  the  nerve-centres  will 
now  be  followed  by  a  special  description  of  each,  in  which  their  spinal  and  cranial 
portions  will  be  successively  considered,  after  glancing  at  them  in  a  general 
manner. 

1.  The  Duea  Matee. 

• 

This  is  the  most  external  and  the  strongest  of  the  cerebro-spinal  envelopes, 
and  lines  the  walls  of  the  cerebro-spinal  cavity,  exactly  repeating  its  shape.  It 
is,  therefore,  a  second  protective  covering,  which  is  dilated  at  its  anterior 
extremity  into  an  ovoid  cavity  that  lodges  the  brain,  and  terminates  in  a  pro- 
longed point  at  the  coccygeal  vertebrae. 

It  has  two  faces — an  external,  in  contact  with  the  walls  of  the  cranium  ;  and 
an  internal,  adhering  in  the  most  intimate  manner  to  the  external  layer  of  the 
arachnoid. 

In  several  parts  of  its  extent  it  is  traversed  by  the  nerves  that  proceed  from 
the  cerebro-spinal  axis,  and  by  the  vessels  for  this  portion  of  the   nervous 


Stkuctuee. — The  dura  mater  possesses  the  texture  of  all  white  fibrous  mem- 
branes. It  is  composed  of  parallel  longitudinal  fasciculi  of  connective  tissue, 
mixed  with  some  fine  elastic  fibres.  Bourgelat  thought  they  formed  two  distinct 
layers — an  external  and  internal  ;  but  nowhere  is  it  possible  to  demonstrate  this. 
It  receives  hlood-ve^seh  ;  the  arteries  are  derived — for  the  spinal  portion,  from 
the  vertebral,  intercostals,  lumbar,  and  lateral  sacrals  ;  for  the  cranial  portion, 
meningeal  ramuscules,  such  as  the  ethmoidal  branch  of  the  nasal,  the  spheno- 
spinous,  and  tympanic,  mastoideal,  and  cerebro-spinal  arteries.  Nerves  have  been 
seen  passing  to  its  cranial  portion  ;  these  have  been  divided  into  anterior,  middle, 
and  posterior.  The  first  are  furnished  by  the  ethmoidal  filament  of  the  nasal 
nerve  :  the  second  from  the  Gasserian  ganglion  ;  and  the  third,  by  the  ophthal- 
mic branch  of  Willis.  The  nerves  of  the  spinal  portion  are  very  fine  and  have 
no  myeline  ;  at  first  they  accompany  the  vessels,  then  leave  them  to  be  dis- 
tributed in  the  middle  part  of  the  membrane.  The  existence  of  lymphatic 
vessels  has  not  yet  been  clearly  demonstrated. 

Spinal  Dura  Mater  (Theca  Vertebkalis,  Dura  Mater  Spinalis). — 
This  is  a  very  elongated  sheath,  continuous  at  the  occipital  foramen  with  the 
cranial  dura  mater,  and  terminated  behind  by  an  attenuated  point  lodged  in  the 
narrow  channel  which,  in  the  middle  coccygeal  vertebrae,  represents  a  trace  of 
the  spinal  canal.  As  it  is  in  shape  exactly  like  the  latter,  its  largest  diameter  is 
at  the  atlas,  and  at  the  brachial  and  lumbo-sacral  enlargements  of  the  spinal 
cord.  Its  capacity  depends  greatly  on  the  volume  of  the  latter,  and  in  some  of 
its  parts  it  can  allow  accumulation  of  the  cerebro-spinal  fluid  ;  this  is  impos- 
sible, however,  for  nearly  the  whole  extent  of  the  cranial  region. 
50 


750  THE  CENTRAL  AXIS  OF  TEE  NERVOUS  SYSTEM. 

The  external  face  of  the  dura  mater  is  very  slightly  adherent— especially  above 
— to  the  walls  of  the  spinal  canal ;  and  it  is  even  separated  from  them,  at  the  inter- 
vertebral spaces,  by  a  certain  quantity  of  adipose  tissue  which  is  never  absent, 
though  the  animals  be  ever  so  emaciated.  This  face  covers,  inferiorly,  the  com- 
mon superior  ligament,  and  the  veins  we  have  described  as  spinal  sinuses. 

(It  does  not  form  an  endosteum  for  the  vertebrae  as  it  does  for  the  cranial 
bones.) 

The  interrwl  face  gives  attachment,  between  each  pair  of  nerves,  to  the 
festoons  of  the  dentated  membrane,  a  dependency  of  the  pia  mater.  It  is 
rendered  smooth  and  polished  by  the  external  layer  of  the  arachnoid,  to  which  it 
is  so  firmly  united  that  it  is  needless  to  attempt  their  separation.  Here  the 
external  layer  of  the  arachnoid  is  reduced  to  a  simple  row  of  cells  with  flattened 
nuclei. 

On  each  side,  the  substance  of  this  meninge  is  completely  traversed  by  a 
double  series  of  orifices  for  the  passage  of  the  spinal  nerves,  around  which  it  sends 
small  special  sheaths  as  far  as  the  intervertebral  foramina. 

Cranial  or  Encephalic  Dura  Mater  (Dura  Mater  Cerebralis). — 
This  membrane  forms  a  sac  which  is  exactly  moulded  by  its  external  face  to 
the  cranial  parietes,  and  by  its  internal  face  to  the  surface  of  the  brain.  The 
latter,  therefore,  completely  fills  the  cavity  of  the  cranium,  a  circumstance  that 
explains  why  an  accumulation  of  fluid  is  impossible  in  this  region. 

External  surface. — It  adheres  strongly,  by  cellulo-vascular  bands,  to  the  cranial 
walls,  the  undulations  on  which  it  follows.  This  adhesion  is  not,  however,  equally 
marked  everywhere,  for  on  the  sides  of  the  roof  of  the  cerebral  compartment  it 
is  least  intimate,  and  it  is  closest  on  the  middle  plane  of  this  roof,  on  the  crista 
galli,  around  the  parietal  protuberance,  on  its  crests,  and  towards  the  lateral  faces 
of  the  cerebellar  compartment  at  the  petrous  bones,  where  the  membrane  is  very 
thin. 

This  face  gives  rise  to  a  number  of  prolonged  sheaths,  corresponding  to  the 
nerves  leaving  the  base  of  the  cranium.  The  principal  are  found  around  the 
ethmoidal  filaments,  the  optic  nerves,  and  the  two  thick  branches  furnished  by 
the  Gasserian  ganglion. 

Internal  surface. — The  internal  surface  of  the  cranial  dura  mater  is  covered 
by  the  parietal  layer  of  the  arachnoid,  which  is  firmly  attached  to  it  only  in  the 
spinal  region.  It  sends  into  the  cranial  cavity  three  prolongations,  which  are 
distinguished  as  the  falx  cerebri  {falx,  "  a  sickle  "),  tentorium  cerebelU  {tentorium, 
"  a  tent "),  and  the  pituitary  fold.  These  processes  complete  the  partitioning  of 
the  cranial  cavity,  isolate  the  various  external  bulgings  of  the  encephalic  mass, 
and  protect  them  from  the  compression  they  might  exercise  on  each  other. 

a.  The  Falx  Cerebri  is  a  vertical  middle  layer  comprised  between  the  two 
cerebral  hemispheres,  and  owes  its  name  to  its  sickle-like  form. 

Its  antero-superior  border  is  adherent  and  very  convex,  and  corresponds  to 
the  crista  galli  process,  as  well  as  to  the  median  ridge  on  the  inner  face  of  the 
frontal  and  parietal  bones.  This  border  is  very  thick,  and  hollowed  internally 
by  a  prismatic  and  triangular  venous  canal — the  middle  sinus. 

Towards  its  inferior  border,  which  is  free  and  concave,  and  rests  on  the 
corpus  callosum,  the  falciform  process  is  extremely  thin,  and  cribbled  like 
lacework. 

The  posterior  extremity,  or  base  of  the  falx,  rests  on  the  parietal  protu- 
berance. 


THE  CEREBROSPINAL   AXIS.  75l 

The  anterior  extremity  advances  in  a  curve  to  near  the  optic  fossa. 

In  aged  animals,  there  are  sometimes  found  on  the  faces  of  the  falx  cerebri, 
especially  towards  its  posterior  extremity,  small  yellow  granulations,  known  as 
the  Pacchionian  bodies.  They  are  little  nuclei  of  connective  tissue  that  arise 
from  the  sub-arachnoideal  tissue  ;  meningeal  granulations  would  be  a  better 
designation  than  that  of  glands,  which  is  sometimes  given  to  them. 

b.  The  Tentorium  Gerebelli  is  composed  of  two  lateral  layers,  which  form  a 
transverse  partition  between  the  cerebellum  and  the  posterior  extremities  of  the 
cerebral  lobes. 

Each  layer,  coursed  internally  by  one  of  the  transverse  sinuses,  ofifers  :  an 
adherent  convex  border,  attached  to  the  parieto-temporal  crest ;  a  free  concave 
border,  turned  inwards  and  a  little  forwards,  remarkable  for  its  thickness  and 
solidity,  and,  with  the  second  lamina,  circumscribing  an  oval  opening  through 
which  the  medulla  oblongata  passes  ;  a  superior  extremity,  attached  to  the  parietal 
protuberance ;  an  inferior  extremity,  which  disappears  above  the  Gasserian 
ganglion,  near  the  fold  that  surrounds  the  pituitary  gland. 

Of  the  two  faces  of  these  layers,  the  anterior  corresponds  to  the  cerebral  lobes, 
the  posterior  to  the  cerebellum. 

c.  The  supra-sphenoidal  or  pituitary  fold,  is  a  thick,  slightly  salient,  and 
almost  circular  pad,  channeled  internally  by  the  cavernous  sinus,  and  circum- 
scribing the  sella  Turcica  by  enveloping  the  pituitary  gland  laterally  and  posteriorly. 

2.  The  Arachnoid  Membrane. 

The  arachnoid  has  the  same  arrangement  as  all  the  splanchnic  serous 
membranes,  in  being  composed  of  two  layers — a  parietal  and  a  visceral,  both 
constituting  a  perfectly  closed  sac,  outside  of  which  the  cerebro-spinal  axis  is 
contained.  The  cavity  of  this  sac  is  traversed  by  the  roots  of  nerves,  the  vessels 
of  the  brain  and  cord,  and  filaments  and  cellular  layers  which  pass  from  the  pia 
mater  to  the  dura  mater  ;  around  all  these  its  layers  form  sheaths,  by  becoming 
continuous  with  one  another. 

Each  of  these  layers  exhibits  an  adherent  and  a  free  face.  The  adherent 
face  of  the  parietal  layer  is  attached,  as  we  have  already  seen,  to  the  dura  mater. 
That  of  the  visceral  layer  covers  the  nervous  axis,  in  spreading  itself  over  the 
pia  mater,  but  without  accompanying  it  into  the  convolutions  of  the  central 
mass  ;  it  is  beneath  this  face  of  the  visceral  layer  that  the  cerebro-spinal  (or 
sub-arachnoid)  fluid  is  confined  in  spaces  which  will  be  studied  hereafter.  By 
their  free  face,  which  is  smooth  and  moist,  like  that  of  all  serous  membranes,  the 
arachnoid  layers  are  in  contact  with  each  other. 

Structure. — The  structure  of  this  membrane  resembles  that  of  all  others  of 
the  same  nature.  The  meshes  of  elastic  fibres  are  most  abundant  in  the  cranial 
portion.  Everywhere  the  parietal  layer  is  only  composed  of  a  single  layer  of 
epithehum.  The  arachnoid  has  no  proper  vessels  or  nerves  ;  those  which  pass 
through  it  only  accompany  each  other. 

Spinal  Arachnoid  Membrane. — The  parietal  layer  presents  nothing  of 
interest.  The  visceral  layer  is  separated  from  the  spinal  cord,  throughout  its 
extent,  by  a  somewhat  considerable  space  (the  sub-arachnsid),  in  which  the 
sub-arachnoid  fluid  is  collected  ;  this  space  is  greatest  posteriorly,  around  the 
terminal  extremity  of  the  cord  and  the  nerves  of  the  cauda  equina. 

The  adherent  face  of  this  membrane  is  only  connected  with  the  external 
surface  of  the  spinal  cord  by  thin  filaments  detached  from  the  pia  mater. 


752  THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 

Cranial  or  Encephalic  Arachnoid.— There  is  nothing  special  to  note  in 
the  iiarietal  Jayer. 

If  the  visceral  layer  be  traced  from  the  occipital  foramen— where  it  is 
continuous  with  the  spinal  arachnoid— to  the  anterior  extremity  of  the  cerebral 
lobes,  it  is  seen  to  be  prolonged  infer iorly  on  the  lower  face  of  the  medulla 
oblongata,  as  far  as  the  pituitary  stem,  to  which  it  furnishes  a  covering  :  the 
pituitary  gland  itseK  is  not  covered  by  the  arachnoid,  except  on  a  portion  of  the 
superior  or  deep  face  ;  from  the  medulla  oblongata  it  is  carried  forward,  and 
extends  on  each  side  of  the  cerebellum  and  cerebral  lobes.  Superiorly,  this 
internal  layer  spreads  over  the  surface  of  the  cerebellum,  and  is  reflected  at  the 
bottom  of  the  fissure  between  that  organ  and  the  cerebral  hemispheres,  over  the 
posterior  extremity  of  the  latter,  enveloping  them  separately  by  descending  into 
the  interlobular  fissure  as  far  as  the  corpus  callosum.  Reaching  the  anterior 
extremity  of  the  cerebrum,  it  gains  the  olfactory  lobes,  is  principally  prolonged 
on  their  super o-posteri or  face,  and  doubles  around  the  ganglion  of  grey  substance 
on  their  inferior  face,  to  be  continued  with  the  parietal  layer. 

In  covering  the  external  sm-face  of  the  brain,  the  cranial  arachnoid  does  not 
adhere  everywhere  to  the  nurve  substance,  but  is  only  slightly  connected  with  it, 
through  the  medium  of  the  pia  mater,  at  such  salient  points  as  the  summits  of 
the  cerebral  convolutions.  Neither  does  it  dip  down  to  enter  the  sulci  existing 
between  these  parts,  but  passes  over  them,  and  in  this  way  forms  a  large  number 
of  sub-arachnoid  spaces  {epi-cerehral  spaces)  analogous  to  that  developed  over  the 
whole  extent  of  the  spinal  cord. 

These  spaces,  which  are  filled  by  the  sub-arachnoid  fluid,  differ  widely  in 
form  and  dimensions.  In  Man,  three  principal  have  been  described,  and  these 
are  also  found  in  animals  ;  Magendie  has  named  them  the  confluents  of  the  sub- 
arachnoid  fluid.  Of  these  three  confluents,  the  antwior  is  situated  in  advance  of 
the  chiasma  of  the  optic  nerves,  between  the  two  cerebral  lobes :  the  inferior, 
the  largest,  is  comprised  between  the  pituitary  stem  and  the  pons  Varolii  to  the 
surface  of  the  peduncles  of  the  cerebrum  ;  while  the  third,  or  posterior  confluent, 
lies  behind  the  cerebellum,  at  the  calamus  scriptorius. 

None  of  these  spaces  communicate  with  the  internal  cavities  of  the  brain, 
and,  consequently,  the  sub-arachnoid  fluid  cannot  enter  them.  Magendie  has 
nevertheless  described  a  communication  between  the  posterior  confluent  and  the 
ventricle  o^  the  cerebellum  ;  though  the  opening  he  described  towards  the 
calamus  scriptorius  has  not  been  found  in  the  Horse  by  Renault,  and  we  may 
affirm,  with  Lavocat,  that  it  does  not  exist  in  the  other  animals. 

The  Sub-arachnoid  Fluid. — The  fluid  contained  in  the  sub-arachnoid 
spaces  is  slightly  yellow  or  colourless,  and  perfectly  limpid  and  transparent. 
Some  authorities  assert  that  it  is  secreted  by  the  visceral  layer  of  the  arachnoid, 
and  others  by  the  pia  mater.  According  to  the  remark  made  by  Cruveilhier,  the 
nerve-centres  are  immersed  in  it,  like  a  foetus  in  the  liquor  amnii ;  and  this 
remark,  which  is  particularly  applicable  to  the  spinal  cord,  gives  the  key  to  the 
use  of  this  fluid,  which  keeps  the  organ  away  from  the  walls  of  the  spinal  canal, 
deprives  it  of  the  greater  part  of  its  weight  (Foltz),  and  thus  diminishes  every 
kind  of  injury  to  which  it  might  be  exposed— whether  from  without  (concussion), 
or  within  (intermittent  afllux  of  blood) — in  a  word,  the  cerebro-spinal  fluid 
constantly  maintains  an  equilibrium  in  pressure  around  the  central  nervous  axis. 

(This  fluid,  so  necessary  for  the  support  and  protection  of  the  cord  and  brain, 
is  alkaline,  and  contains  but  a  small  quantity  of  albumen  ;  it  varies  in  quantity. 


THE  CEREBROSPINAL  AXIS.  753 

according  to  the  relative  size  of  the  cerebro-spinal  axis  and  its  containing  cavity, 
or  with  the  amount  of  blood  sent  to  this  region.  By  affording,  under  all 
circumstances,  an  equable  pressure  on  the  brain  and  spinal  cord,  and  the  nerves 
emanating  from  these,  its  importance  as  a  hydrostatic  agent  is  greatly  enhanced.) 

3.  The  Pia  Mater. 

The  pia  mater — the  proper  envelope  of  the  cerebro-spinal  axis — is  a  thin 
membrane,  the  framework  of  which,  essentially  connective  tissue,  sustains  on  its 
external  face  a  very  abundant  network  of  blood-vessels  and  nerves. 

Applied  immediately  to  the  surface  of  the  brain  and  spinal  cord,  it  adheres 
firmly  to  that  surface  and  follows  all  its  inequalities — penetrating  between  the 
cerebral  or  cerebellar  convolutions,  and  forming  in  each  intermediate  sulcus  two 
layers  that  lie  against  each  other. 

The  external  face  of  the  pia  mater,  bathed  in  part  of  its  extent  by  the  sub- 
arachnoid fluid,  adheres  to  the  visceral  layer  of  the  arachnoid  by  means  of  a 
more  or  less  dense  and  close  connective  tissue.  From  it  arise  the  cellular 
coverings  that  constitute  the  neurilemma  of  the  nerves.  It  detaches  a  multitude 
of  filamentous  and  lamellar  prolongations  to  the  internal  face  of  the  dura  mater, 
which  traverse  the  arachnoid  cavity  in  the  same  manner  as  the  nerves  and 
vessels,  by  being  enveloped,  like  these,  in  a  sheath  furnished  by  the  arachnoid 
membrane.  Always  very  short,  these  prolongations  resemble  the  adhesions 
between  the  two  layers  of  that  membrane. 

The  internal  face  is  attached  to  the  nerve  substance  by  multitudes  of  arterial 
and  venous  radicles  or  connective  filaments,  which  leave  the  pia  mater  to  plunge 
into  that  substance. 

The  vessels  of  the  pia  mater  form  a  very  close  network,  from  which  are 
detached  branches  that  reach  the  medulla  oblongata  and  brain.  They  are 
accompanied  by  nerve-filaments,  and  are  surrounded  hj perivascular  canals,  which 
are  now  believed  to  be  lymphatics.  Certainly,  in  their  interior  a  colourless  fluid 
circulates,  which  contains  lymph-corpuscles. 

Spinal  Pia  Mater. — Less  vascular  than  the  cranial  pia  mater,  with  which 
it  is  continuous  towards  the  medulla  oblongata,  this  membrane  is  remarkable  for 
the  arrangement  of  the  prolongations  that  arise  from  its  two  faces. 

The  internal  prolongations  form  longitudinal  layers  at  the  fissures  of  the  cord, 
and  enter  these  fissures. 

The  external  prolongations  attach,  as  we  have  said,  the  pia  mater  to  the 
external  meninge.  A  very  large  number  are  filamentous  in  form,  and  are 
dispersed  over  the  superior  and  inferior  surfaces  of  the  cord.  Others  constitute, 
on  each  side  of  the  organ,  a  festooned  band  named  the  dentated  ligament 
{ligamentum  denticulatum  or  dentata).  These  ligaments  exist  throughout  the 
entire  length  of  the  spinal  cord,  between  the  superior  and  inferior  nerve- 
roots  :  their  inner  border  is  confounded  for  its  whole  length  with  the  pia  mater  ; 
and  their  outer  margin,  cut  into  festoons,  attaches  itself  to  the  dura  mater  by 
the  summit  of  the  angles  separating  these  festoons. 

To  complete  this  description  of  the  spinal  pia  mater,  there  may  be  noticed 
a  posterior  or  coccygeal  2)rolongation  {filum  termijiale) — a  very  narrow  process 
formed  by  this  membrane  at  the  posterior  extremity  of  the  cord,  situated  in  the 
midst  of  the  cauda  equina  nerves,  and  attached  to  the  bottom  of  the  conical 
cul-de-sac  at  the  termination  of  the  dura  mater. 

(This  ligament,  or  memhrana  dentata,  serves  to  maintain  the  position  of  the 


754  THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 

spinal  cord  in  its  hydrostatic  bed,  and  so  prevents  the  nerves  proceeding  from 
it  being  dragged  during  flexion  of  the  spine.) 

Cranial  or  Encephalic  Pia  Mater. — The  vascular  element  predominates 
in  this  portion  of  the  internal  meninge. 

This  membrane  sends  scarcely  any  prolongations  to  the  dura  mater,  except 
at  the  medulla  oblongata,  though  it  projects  remarkably  large  ones  into  the 
cerebral  mass  and  the  sides  of  the  cerebellum.  The  description  of  the  velum 
interpositum,  and  the  cerebral  and  cerebellar  plexus  choroides,  belongs  to  the  brain. 

(The  pia  mater  is  extremely  vascular  on  the  surface  of  the  cerebrum,  and 
forms  remarkable  anastomosing  loops  in  the  intermediate  spaces  of  the  conr 
volutions,  which  chiefly  supply  the  grey  substance.  It  is  the  nutrient  membrane 
of  the  brain  and  spinal  cord.  Its  nerves  accompany  its  arterial  branches,  and  are 
minute  filaments  from  the  sympathetic.) 

"Differential  Characters  in  the  Enveloping  and  Protective  Parts  of  the  Cerebro- 
spinal Axis  in  the  Other  Animals. 

The  bony  space  that  protects  the  spinal  cord  and  brain  does  not  present  any  noteworthy 
diflferences  in  the  domesticated  animals,  and  the  subject  has  been  already  sufficiently  studied 
in  the  osteology  of  the  head  and  vertebral  column. 

With  regard  to  the  meninges,  their  number  and  general  disposition  are  nearly  the  same  in 
all  the  species.  In  the  Sheep,  however,  the  cranial  dura  mater  appears  to  be  absent,  or  is 
only  represented  by  a  mere  thickening  in  which  is  the  middle  sinus  ;  the  falx  cerebri  is  only 
indicated  towards  its  two  extremities.  The  vestige  of  this  septum  is  more  developed  in  the  Goat. 

Comparison  of  the  Enveloping  and  Protective  Parts  of  the  Cerebro-Spinal 
Axis  of  Man  with  those  of  Animals. 
There  is  nothing  particular  to  be  said  respecting  the  cranial  cavity  and  spinal  canal,  nor 
yet  the  arachnoid  and  pia  mater.  The  dura  mater  has  tlie  folds  described  in  Solipeds,  and, 
in  addition,  a  falx  cerehelli,  that  extends  from  the  tentorium  of  the  same  name  to  near  the 
foramen  magnum.  The  meningeal  granulations,  or  Pacchionian  glands,  are  nearly  constant 
in  aged  individuals,  and  their  volume  is  sometimes  so  considerable,  that  by  compression  they 
thin  away,  and  even  perforate,  the  cranial  bones  at  corresponding  points. 


CHAPTER  II. 
THE   SPINAL   CORD. 


Preparation. — Isolate  the  cranium  and  vertebral  column  from  all  the  other  parts  of  the 
body ;  open  the  spinal  canal  and  the  cranial  cavity  by  their  superior  surface,  as  in  Fig.  416, 
by, raising  with  a  chisel  (or  rogne-pied — the  farrier's  "  toe-knife  ")  and  hammer,  the  roof  of  the 
skull  and  annular  portion  of  all  the  vertebrae.  The  organ  may  tlien  be  studied  in  situ  in  its 
bony  case,  and  surrounded  by  its  membrane;  afterwards  extract  the  whole  spinal  cord 
enclosed  in  the  dura  mater,  and  open  up  the  latter  along  the  course  of  the  cord,  so  as  to 
completely  expose  that  portion  of  the  nervous  system. 

On  a  cord  hardened  by  water  to  which  a  tenth  part  of  nitric  acid  has  been  added,  the 
arrangement  and  distribution  of  the  grey  and  white  matter  may  be  studied;  the  different 
cords  composing  it  may  be  also  more  or  less  exactly  separated. 

(The  saw  and  farrier's  pincers,  or  spine  ratchet,  will  be  found  useful  auxiliaries  in  the 
tedious  and  delicate  operation  of  exposing  the  brain  and  cord,  and  particularly  in  laying  open 
the  cranial  cavity.  An  easy  mode  of  obtaining  access  to  the  spinal  canal  and  its  contents,  is 
to  saw  through  the  laminae  of  the  vertebrae  on  each  side,  at  the  roots  of  the  transverse  processes, 
and  raise  the  arches  with  the  chisel  or  toe-knife.) 

ExTEENAL  Conformation  of  the  Spinal  Cord. 
General  view. — The  spinal  cord  is  that  portion  of  the  nervous  centres  which 
occupies  the  spinal  canal.     It  is  a  thick,  white,  and  irregularly  cylindrical  cord, 


TEE  SPINAL   CORD. 


7M 


756  THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 

commencing  at  the  occipital  foramen,  where  it  continues  the  medulla  oblongata, 
and  terminating  in  a  point  at  the  upper  third  of  the  sacral  canal,  or  a  little 
beyond  that,  giving  off  at  each  side,  during  its  course,  the  superior  and  inferior 
roots  of  the  spinal  nerves. 

Weight. —  In  medium-sized  animals,  the  weight  of  the  cord  is  represented  by 
the  following  approximate  numbers  :  for  the  Horse,  10^  ounces  ;  the  Ass,  5i 
ounces  ;  Cow,  7|  ounces  ;  Sheep  and  Goat,  If  ounces  ;  Pig,  2^  ounces  ;  Dog,  li 
ounces  ;  Cat,  4^  drams  ;  and  Rabbit,  3i  drams. 

Shape  and  volume. — The  spinal  cord  is  slightly  flattened  above  and  below, 
throughout  its  whole  length  ;  in  whatever  part  we  examine  a  transverse  section 
of  it,  we  shall  always  find  the  lateral  diameter  greater  than  the  vertical,  and  that 
this  section  appears  regularly  elliptical. 

The  flattening  is  more  marked  in  the  lumbar  than  in  any  other  region. 

Its  volume  is  far  from  being  uniform.  In  following  it  from  before  to  behind, 
we  at  first  remark  that  it  presents  the  same  dimensions  to  the  fifth  cervical 
vertebra,  and  that  between  this  point  and  the  second  dorsal  vertebra  it  forms 
an  oblong  enlargement,  designated  the  brachial  cei'rical  e}ilargement  (or  bulb). 
Beyond  this,  it  assumes  its  original  volume,  and  even  becomes  gradually  smaller 
than  in  the  cervical  region.  Towards  the  middle  of  the  loins,  it  again  enlarges 
to  constitute  the  lumbar  enlargement  (or  bulb),  which  extends  to  the  entrance  of 
the  sacral  canal.  After  this  dilatation  comes  a  conical  prolongation  (conus 
meduUaris),  the  point  of  wliich  represents  the  terminal  extremity  of  the  cord. 

If  we  compare  the  diameter  of  this  cord  with  that  of  the  spinal  canal,  we  shall 
observe,  as  has  been  already  said,  that  the  capacity  of  the  containing  cavity 
is  generally  related  to  the  volume  of  its  contents,  and  that  the  former  is,  as  a 
rule,  most  capacious  at  the  cervical  and  lumbar  enlargements.  It  will  even  be 
noticed  that  the  dilatation  the  spinal  canal  offers  at  these  two  points,  is  relatively 
more  considerable  than  the  increase  in  volume  of  the  cord.  This  is  because  the 
mobility  of  the  spine,  which  is  very  great  in  these  two  regions,  requires  this 
difference  to  secure  the  spinal  axis  from  injury  during  the  movements  executed 
by  the  vertebral  column.  This  protective  combination  is  also  found  elsewhere — 
at  the  atlas,  for  example,  where  we  know  motion  is  considerable  ;  and  throughout 
the  entire  extent  of  the  cervical  region,  which  in  this  respect  greatly  exceeds  the 
dorsal  region. 

Means  of  fixture. — The  cord  is  relatively  fixed  in  its  envelopes  by :  1.  Its 
continuity  with  the  brain.  2.  The  coccygeal  ligament.  3.  The  dentated 
ligaments. 

E.tternal  surface  of  the  cord. — Covered  by  the  pia  mater,  this  surface  presents 
an  extremely  simple  disposition.  On  its  superior  and  inferior  planes,  at  each 
side,  we  remark  the  double  series  of  sensitive  and  motor  roots  of  the  spinal 
nerves,  which  are  implanted  in  the  same  longitudinal  line  to  right  and  left  of 
the  middle  plane,  and  are  collected  in  fasciculi  opposite  the  intervertebral 
foramina. 

In  the  middle  line,  and  throughout  the  entire  length  of  the  cord,  there  are 
two  deep  and  narrow  fissures  :  one  superior  {fissura  longitudinaUs  superior),  the 
other  inferior  {fissura  longitudinaUs  infei'ior),  into  which  the  pia  mater  enters. 
Four  other  fissures  have  been  described  at  the  point  of  emergence  of  the  nerve- 
roots,  by  the  names  of  suferior  and  inferior  collateral  fissures  (or  sulci) ;  but  the 
two  superior  alone  exist,  and  even  these  are  often  scarcely  noticeable,  being 
rather  indicated  by  the  origin  of  the  nerve-roots. 


TUE  SPINAL   COED. 


757 


Inteenal  Conformation  and  Structure  of  the  Spinal  Cord. 

In  making  a  transverse  section  of  any  portion  of  the  cord,  we  may  convince 
ourselves  that  it  has  an  internal  cavity.  This  central  canal  is  elliptical,  and 
lined  by  a  simple  layer  of  columnar  ciliated  epithelium,  resting  on  a  thin  con- 
nective membrane — the  ependymis  of  Virchow.  (The  cilia  of  these  cells  are  only 
to  be  seen  in  early  life  ;  in  advanced  age  the  canal  may  be  closed,  the  cells  then 
becoming  much  altered  in  form  from  pressure.  The  canal  is  immediately  sur- 
rounded by  spongy  horny  matter.)  This  section  also  shows  the  two  median 
fissures  mentioned  in  describing  the  exterior  of  the  cord,  the  inferior  of  which  is 
wider  and  deeper  than  the  superior,  the  situation  of  the  latter  being  scarcely 
perceptible. 

These  two  fissures  lie  one  before  the  other,  and  do  not  meet  so  as  to  com- 
pletely divide  the  cord  into  two  lateral  halves,  but  remain  separated  by  two 
thin  horizontal  and  superposed  bands 
of  nerve  matter,  that  pass  from  one 
end  to  the  other  of  the  medullary  axis. 
The  inferior,  formed  of  white  sub- 
stance, corresponds  to  the  bottom  of 
the  inferior  fissure  ;  while  the  superior, 
composed  of  grey  matter,  meets  the 
superior  fissure. 

These  bands  are  named  the  white 
and  grey  commissures  of  the  spinal  cord 
(Figs.  418,  419,  420). 

Notwithstanding  the  presence  of 
these  two  commissures  between  the 
lateral  halves  of  the  spinal  axis,  these 
latter  do  not  the  less  constitute  two 
symmetrical  systems,  the  structure  of 
which  will  now  be  studied. 

Each  medullary  cord  represents  a 
semi-cylinder  of  white  substance,  in  the 
centre  of  which  is  a  mass  of  grey  matter, 
that  varies  somewhat  in  quantity  in 
different  regions,  but  the  arrangement  of  which  is  everywhere  the  same.  Thus, 
inwardly,  this  grey  matter  joins  the  grey  commissure  ;  above,  it  sends  off  a  thin 
prolongation  that  traverses  the  substance  of  the  medullary  cord  {superior  grey 
cornu),  to  reach  the  bottom  of  the  superior  collateral  fissure  ;  below,  it  gives  rise 
to  an  analogous,  though  a  thicker  and  a  more  irregular,  prolongation  (inferior 
grey  cornu),  which  is  directed  well  in  front  of  the  inferior  roots,  but  does  not 
reach  the  surface  of  the  cord.  In  consequence  of  this  arrangement,  the  grey 
substance  of  the  cord  forms  altogether  a  kind  of  capital  H,  the  horizontal 
branch  of  which  is  perforated  in  the  middle  by  the  central  canal. 

This  arrangement  of  the  grey  substance  causes  the  white  matter  to  be 
divided,  in  each  lateral  moiety  of  the  spinal  axis,  into  three  cords  or  secondary 
columns ;  the  superior  of  these  is  perfectly  isolated,  and  is  comprised  between 
the  middle  superior  fissure  and  the  origin  of  the  sensitive  roots  ;  another,  the 
inferior,  united  to  that  of  the  opposite  side  by  the  white  commissure,  is  limited, 
inwardly,  by  the  inferior  median  fissure,  and  outwardly  by  the  line  of  origin  of 


SECTION  OF  THE  SPINAL  CORD  OF  THE  HORSE 
AT  THE  LUMBAR  REGION.  MAGNIFIED  TWO 
DIAMETERS. 

1,  Superior  median  fissure ;  2,  infei-ior  median 
fissure  ;  3,  3,  superior  collateral  fissures  ;  4,  4, 
inferior  ditto  ;  5,  grey  commissure  ;  6,  white 
commissure  ,  7,  7,  superior  grey  cornua;  8,  8, 
inferior  grey  cornua  ,  9,  central  canal. 


758 


THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 


the  motor  nerve-roots  ;  while  a  third — the  lateral  or  intermediate — thicker  than 
the  others,  is  confounded  supei-ficially  with  the  inferior,  and  formed  by  all  that 
portion  of  the  cord  situated  between  the  lines  of  origin  of  the  superior  and 


COAi- 


TRANSVERSE   SECTION   OF  THE  SPINAL  CORD   IN   THE   LUMBAR   REGION.      (AFTER   DEITERS.) 
.a.,  Inferior  root ;  R.p.,  superior  root ;  R.i.p.,  internal  portion  of  the  superior  root ;  C.p.,  superior 
commissure ;  C.a.a.,  inferior  commissure ;    C.c,  central  canal.     The  network  of  myeline  fibres 
in  the  grey  substance,  as  well  as  those  in  the  infei'ior  grey  commissure,  are  not  indicated. 


inferior  roots.     Of  these  three  columns,  the  first  is  sensory 
which  in  reaUty  are  only  one — are  not.^ 


the  other  two- 


'  The  existence  of  so-called  "  systematic  lesions  "  in  Man  has  led  anthropotomists  to  dis- 
tinguish, iu  the  white  substance  of  the  cord,  a  great  number  of  regions.  Thus,  the  innermost 
portion  of  the  anterior  column  (inferior  in  animals)  is  designated  Tiirck's  fasciculus ;  the  corre- 
sponding portion  of  the  posterior  column  (superior)  in  tiie  cervical  region  is  GolVs  column ;  the 
lateral  column  is  rigorously  limited  by  the  grey  cornua ;  while  the  regions  around  these  latter 
are  named  the  anterior  and  posterior  radicular  zones. 

In  adhering  to  the  facts  of  normal  anatomy,  it  must  be  admitted  that  some  of  these  dis- 
tinctions are  in  great  part  artificial.     Nevertheless,  there  are  found  on  the  limits  of  certain 


THE  SPINAL   CORD. 


759 


Steucture. — Independently  of  the  epithelium  mentioned  when  describing 
the  ependymis,  neuroglia,  nerve-fibres,  nerve-cells,  and  vessels  enter  into  the 
structure  of  the  spinal  cord. 

The  neuroglia  has  been  compared  to  a  kind  of  sponge  (the  so-called  spongy 
matter),  in  the  spaces  of  which  are  the  other  elements  of  the  cord.  It  exists  in 
the  white  and  the  grey  matters,  but  it  is  more  abundant  in  the  superior  grey 
cornua  than  in  the  inferior  cornua.  It  surrounds  the  upper  extremity  of  the 
former,  in  becdning  softer  and  more  transparent,  and  is  here  designated  the 
gelatinom  substance  of  Rolando  (substantia  gelatinoso  Rolandi).     It  constitutes, 


TRANSVERSE  SECTION  OF  SPINAL  CORD  THROUGH  THE  MIDDLE  OF  THE  I,UMBAR  REGION,  SHOWING 
ON  THE  RIGHT  SIDE  THE  COURSE  OF  THE  NERVE-ROOTS,  AND  ON  THE  LEFT  THE  POSITION  OF 
THE    PRINCIPAL   TRACTS   OF   VESICULAR    MATTER. 

A,  A,  Inferior  columns ;  p,  p,  superior  columns ;  L,  L,  lateral  columns ;  a,  inferior  median  fissure ; 
p,  superior  median  fissure;  6,  6,  6,  h,  inferior  roots  of  spinal  nerves;  c,  c,  superior  roots; 
d,  d,  tracts  of  vesicular  matter  in  superior  column  ;  e,  tracts  of  vesicular  matter  in  inferior  column 
/,  central  canal  ;  g,  substantia  gelatinosa. 

in  great  part,  the  grey  commissure,  and  can  be  deeply  stained  by  the  carminate 
of  ammonia. 

The  neuroglia  is  associated  with  a  small  quantity  of  connective  tissue,  which 
enters  the  cord  along  with  the  vessels.    It  is  formed  of  a  mass  of  cells,  the  mem- 


regions  either  a  depression  on  the  surface  of  the  cord,  or  on  its  substance  a  fasciculus  of 
connective  tissue,  or  a  vessel  larger  than  in  other  points. 

The  systematic  lesions  of  the  cord  not  having  yet  been  observed  in  the  domestic  animals,  it 
cannot  be  stated  at  what  point  the  distinctions  established  in  the  human  spinal  cord  are  justified, 
so  far  as  that  of  the  Horse  is  concerned.  In  some  sections  of  the  cord  of  that  animal,  it  would 
appear  that  the  fasciculus  of  Tiirck  is  distinct  from  the  other  parts  of  the  anterior  column ; 
but  in  a  great  number  the  separation  is  extremely  vague.  The  columns  of  Goll  alone  are  very 
distinct  in  the  superior  portion  of  the  cervical  region.     They  are  especially  visible  in  the  Dog. 

In  fact,  at  the  present  time  the  topography  of  the  human  spinal  cord  cannot  be  without 
uncertainty  when  applied  to  that  of  animals ;  but  the  efforts  of  pathologists  and  anatomists 
should  be  directed  to  dissipating  this  uncertainty. 


760 


THE  CENTRAL  AXIS  OF  THE  NEBVOUH  SYSTEM. 


TEK  SPINAL   CORD. 


761 


branous  bodies  of  which,  irregularly  stellate,  send 
numerous  prolongations  between  the  nerve-tubes 
and  cells. 

(In  the  substantia  gelatinosa  on  the  superior 
surface  of  the  cord  is  a  network  of  fine  fibrils, 
epithelial  in  its  nature,  and  consisting  of  cuticiilar 
matter ;  this  is  known  as  the  granular  matter, 
or  spongy  horn-substance.) 

The  fibres  and  cells  form,  with  the  neuroglia, 
the  whole  of  the  grey  substance. 

The  cells  have  a  more  or  less  large  number 
of  protoplasmic  prolongations  which  ramify  and 
anastomose,  or  have  a  process — the  prolongation 
of  Deiters — which  puts  them  in  communication 
with  a  nerve-tube.  They  are  more  or  less 
voluminous. 

The  fibres  of  the  grey  substance  are  all  very 
fine,  and  some  have  a  sheath  of  myeline ;  the 
others  are  reduced  to  an  axile  filament. 

In  the  Horse,  the  cells  are  not  universally 
distributed  throughout  this  substance,  but  are 
collected  in  small  masses  Avhich  form  longitudinal 
columns.  The  largest  are  grouped  in  three  small 
masses  around  the  inferior  cornu — one  external, 
another  internal,  and  the  third  at  the  extremity  ; 
the  latter  is  the  most  considerable.  They  are 
in  relation  with  the  motor  roots  of  the  nerves. 

Some  are  spread  in  the  middle  part  of  the 
grey  substance,  and  principally  opposite  the  point 
where  the  grey  commissure  joins  the  cornua. 
There  they  form  Lochhart  Clarke''s  column. 

A  small  number  are  placed  on  the  margin 
of  the  superior  grey  cornu,  and  these,  as  well  as 
the  cells  of  Clarke's  column,  receive  radicular 
filaments  from  the  spinal  sensory  nerves. 

Finally,  some  form  an  external  column 
{column  of  Burdach)  at  the  junction  of  the  two 
cornua,  whence  emerges,  above,  the  small  nerve 
of  Wrisberg.  They  are  probably  connected  with 
the  vaso-motor  phenomena. 

The  nerve-tubes  (or  tubules)  affect  longi- 
tudinal, transversal,  oblique,  and  vertical  direc- 
tions. They  bring  the  cells  of  one  lateral  moiety 
of  the  medulla  into  communication  with  :  1. 
The  tubes  of  the  white  substance  which  pass 
towards  the  brain.  2.  Each  other.  3.  The  cells 
of  the  opposite  moiety,  by  passing  into  the  com- 
missures. 4.  The  tubes  of  the  white  substance 
of  the  opposite  moiety,  by  following  the  same 
course. 


Fig.  422. 


LONGITUDINAL  SECTION  THROUGH 
CERVICAL  ENLARGEMENT  OF  SPINAL 
CORD  OF   CAT. 

AC,  Inferior  white  columns ;  Ac',  por- 
tion showins  the  arrangement  of 
the  longitudinal  fibres ;  PC,  pos- 
terior white  columns  ;  G,  grey  sub- 
stance between  them  (the  vesicles 
being  omitted  to  avoid  obscuring 
the  course  of  the  fibres);  A,  anterior 
roots  of  the  nerves ;  p,  posterior 
roots,  consisting  of  three  kinds : 
the  first,  a,  crossing  the  posterior 
columns  horizontally,  and  then 
passing  obliquely  downwards, 
across  the  grey  substance,  into  the 
anterior  columus ;  the  second,  6, 
traversing  the  posterior  columns 
horizontally,  and  then  losing  them- 
selves in  the  grey  substance  ;  the 
third,  c,  for  the  most  part  becoming 
continuous  with  the  longitudinal 
fibres  of  the  posterior  column  ;  all, 
or  ne:irly  all,  ultimately  entering 
the  grey  substance. 


762  TEE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 

The  neuroglia  and  nerve-tuhes  constitute  the  ivhite  substance,  which  Is 
arranged,  as  we  know,  into  three  columns  at  least.  All  the  tubes  of  this  sub- 
stance do  not  ascend  to  the  brain,  as  was  believed  for  a  long  time  ;  the  opinion 
that  the  tubes  of  the  spinal  nerves  formed  the  medulla  and  extended  to  the  brain, 
has  been  abandoned  since  Volkmann  measured,  comparatively,  the  section  of  all 
these  nerves  and  that  of  the  nervous  spinal-axis. 

The  tubes  or  fibres  of  the  white  substance  have  not  always  the  same  com- 
position, nor  the  same  size.  Many  have  no  enveloping  membrane,  and  those 
which  possess  one  have  not  a  nucleus  ;  so  that  it  is  difficult  to  regard  this  as  a 
true  sheath  of  Schwann.  Certain  anatomists,  however,  consider  them  to  be  so, 
but  without  the  constriction  (Ranvier)  ;  while  others  admit  that  they  are  so 
provided,  like  the  elements  of  the  nerves  (Tourneur  and  Legoff ). 

These  tubes  are  thick  in  the  inferior  columns,  and  uniformly  smaller  in  the 
superior  ones.  A  mixture  of  fine  and  thick  tubes  is  observed  in  the  lateral 
columns,  but  the  finest  are  always  generally  towards  the  grey  substance.^ 

(Volkmann  has  established  the  fact,  that  the  size  of  the  medulla  corresponds 
with  the  number  of  nerve-tubes  given  off  at  any  point.  He  gives  the  weight  of 
four  segments,  each  2f  inches  in  length,  from  the  spinal  cord  of  the  Horse,  and 
the  relative  extent  of  the  grey  matter  in  square  lines  ;  these  are  as  follows  : — 


Area 

Area 

of  grey 

of  white 

Grains. 

matter. 

matter. 

rom  below  2nd  spinal  nerve,    219     . 

.      .     13       . 

.        109 

„      8th      „           „      293     . 

.      .     28       . 

.       142 

„         „     19th      „            „       163     . 

.      .     11       . 

89 

„     30th       „            „      281     . 

.      .     25       . 

.       121) 

In  the  white  substance  the  tubes  are  longitudinal,  oblique,  or  transversal ; 
the  latter  arise  from  the  cells  of  the  grey  substance,  and  form  the  roots  of  the 
nerves  emerging  either  by  the  superior  or  inferior  collateral  fissure. 

The  tubes  of  the  inferior  columns  pass  to  the  cells  of  the  grey  substance,  or 
reach  the  brain  by  remaining  in  the  corresponding  moiety  of  the  cord — the 
fibres  of  the  right  half  of  the  medulla  gaining  the  brain  without  passing  into 
the  left  half.  Those  of  the  lateral  columns  decussate,  each  sending  to,  and 
receiving  from,  the  other,  tubes  which  cross  in  the  white  commissure.  The 
superior  columns  contain  fibres  that  extend  directly  to  the  brain ;  these  are 
sensorial.  There  are  also  found  transverse  fibres  that  enter  the  cells  of  the 
superior  grey  cornua,  and  others  that  pass  into  the  cells  of  the  inferior  or  motor 
cornua. 

Such  is,  in  a  few  words,  the  arrangement  of  the  nerve-elements  in  the  spinal 
cord.  The  subject  is  a  very  long  and  complicated  one,  which  cannot  be  dealt 
with  in  a  more  detailed  manner  in  an  elementary  work  on  descriptive  anatomy. 

Vessels. — In  the  spinal  cord  the  grey  is  richer  in  vessels  than  the  white  sub- 
stance. The  capillary  networks  are  finer  in  the  former  than  the  latter,  and  chiefly 
in  the  vicinity  of  the  nerve-cells. 

Arterial  blood  entere  the  cord  by  three  orders  of  vessels  :  1.  The  median 
arteries,  which  pass  into  the  inferior  and  superior  middle  fissures.  2.  The  radi- 
cular arteries,  which  follow  the  roots  of  the  spinal  nerves.  3.  The  peripheral 
arteries,  which  arise  from  the  vascular  ramifications  of  the  pia  mater  (Duret). 
The  vessel  which  furnishes  these  divisions  is  the  middle  spinal  artery. 

'  There  is  a  tendency  now  to  the  belief  that  these  slender  tubes  serve  for  the  conveyance 
of  sensory  impressions.     An  alteration  in  tliem  is  coincident  with  deranged  sensibility. 


THE  BRAIN.  763 

The  veins  are  proportionately  large.  Two  are  lodged  in  the  grey  commissm-e  ; 
and  a  third,  which  is  voluminous,  lies  in  the  middle  superior  fissure. 

All  the  vessels  arc  accompanied  by  the  slender  nerves  disposed  in  plexuses 
issuing  with  the  communicating  veins,  or  the  superior  radicles  which  they  follow 
into  the  substance  of  the  cord. 

In  the  cord  there  are  perivascular  lymph  spaces^  which  probably  open  into  the 
deep  layer  of  the  pia  mater. 

Differential  Chaeacters  in  the  Spinal  Cord  of  the  otoee  Animals. 

In  all  the  species,  the  white  aud  grey  substances  affect  the  disposition  above  described ; 
only  some  slight  differences  in  the  reciprocal  volume  of  each  have  been  remarked.  As  in  the 
Horse,  the  spinal  cord  does  not  extend  beyond  the  sacral  region.  Its  length  has  no  relation  to 
that  of  the  coccygeal  region,  as  certain  anatomists  would,  in  principle,  establish ;  in  the  Rabbit, 
for  example,  the  tail  of  which  is  very  short,  the  spinal  cord  is  prolonged  into  the  coccygeal 
Tertebrse. 

Comparison  of  the  Spinal  Cord  of  Man  with  that  op  Animals. 

The  spinal  cord  of  achilt  Man  does  not  reach  beyond  the  first  lumbar  vertebra,  though  in 
the  foetus  it  is  in  the  coccyx.  It  is  rounder  than  in  the  Horse,  and  the  grey  substance  is, 
relative  to  the  white,  more  abundant  than  in  the  spinal  cord  of  the  domesticated  animals.  The 
posterior  grey  cornua  are  also  larger  and  less  elongated,  than  the  superior  cornua  in  the  Horse ; 
and  the  roots  of  the  nerves  are  also  more  voluminous  than  in  that  animal. 

No  nerve-cells  are  found  in  the  posterior  coiuua,  and  Clarke's  column  is  limited  to  the 
dorsal  region;  so  that  the  sensitive  nerves  of  the  back  and  loins  arise  in  the  dorsal  region. 
The  nerves  of  the  cervical  region  arise  from  a  series  of  nuclei  arranged  in  the  medulla 
oblongata. 


CHAPTER  III. 
THE   BRAIN,   OR  ENCEPHALON. 

Article  I. — The  Brain  as  a  Whole. 

The  hrain  is  that  portion  of  the  nervous  system  which  is  lodged  in  the  cranial 
cavity.  It  succeeds,  without  any  line  of  demarcation,  the  spinal  cord,  of  which 
it  may  be  considered,  with  regard  to  its  figure,  as  a  kind  of  efflorescence. 

General  form  and  composition. — In  shape  it  is  an  ovoid  mass,  elongated  from 
before  to  behind,  and  very  slightly  depressed  above  and  below. 

When  it  is  viewed  on  its  superior  face  (Fig.  423),  we  first  see,  behind,  a  white 
pedicle — the  prolongation  of  the  spinal  cord — and  a  single  lobe  of  a  grey  colour 
designated  the  cerebellum.  In  front  of  this  is  remarked  two  other  lobes,  separated 
from  the  first  by  a  deep  transverse  fissure,  into  which  the  tentorium  cerebelli 
passes.  Isolated  from  one  another  on  the  middle  line  by  a  shallower  fissure,  these 
two  lobes  constitute  the  brain,  and  are  usually  named  the  cerebral  hemispheres. 

In  turning  over  the  brain  to  examined  its  inferior  face,  we  see  that  the  posterior 
peduncle  of  the  organ — a  continuation  of  the  spinal  cord — is  prolonged  beneath 
the  cerebellum,  which  is  joined  to  the  lateral  parts  of  its  superior  face  ;  this  por- 
tion then  enters  the  cerebral  hemispheres  by  their  inferior  face,  behind  two  thick 
white  cords — the  optic  nei-ves — which  mark  the  anterior  limit  of  this  prolongation 
(Fig.  424).     This  is  the  isthmus  of  the  brain — ^a  name  given  to  it  because  it 


764 


THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 


actually  forms  an  intermediate  bond  between  the  three  enlargements  which  form 
the  principal  mass  of  the  organ. 

The  cranial  portion  of  the  central  nervous  mass  is,  then,  composed  of  three 

Fig.  423. 


BRAIN   OF   THE    HORSE    (UPPER   SURFACE).      THREE-FOURTHS   THE    NATURAL  SIZE. 

1,  Great  longitudinal  or  inter-hemispherical  fissure;  2,  2,  crucial  fissure;  3,  3,  fissure  of  Rolando; 
4,  4,  its  anterior  branch ;  5,  5,  its  posterior  branch ;  6,  6,  plaits  of  the  ascending  frontal  convolu- 
tion ;  7,  7,  the  two  plaits  of  the  external  parieto-occipital  convolution  ;  8,  8,  internal  parieto- 
occipital convolution;  9,  9,  first  frontal  convolution;  10,  10,  second  frontal  convolution;  11,  11, 
sigmoid  gyrus,  often  concealed  by  the  annectent  gyrus  of  12,  which  joins  the  ascending  frontal  convo- 
lution of  the  second  frontal ;  13,  lobule  of  the  curved  plait ;  14,  14,  annectent  gyrus  uniting  the  two 
parietal  convolutions  to  the  sigmoid  gyrus,  and  through  it  to  the  frontal  convolutions,  o,  0, 
Olfactory  bulbs;  B,  medulla  oblongata;  c",  middle  lobe  of  the  cerebellum;  c*,  lateral  lobes  of 
ditto. 


apparatuses  :  the  isthmus  of  the  brain — a  prolongation  of  the  spinal  cord  ;  and  the 
cerebellum  and  cerebrum — bulbous  lobes  grafted  on  the  superior  face  and  anterior 
extremity  of  this  peduncle.      These  three  divisions  are  very  well  seen  in  their 


THE  BRAIN,    OB   ENCEPRALON.  765 

entirety  and  reciprocal  relations  in  Fig.  424.  "We  will  study  them  separately  and 
in  succession. 

Volume  of  the  brain. — Contrary  to  what  is  found  in  the  spinal  cord,  the 
dimensions  of  the  brain  closely  represent  those  of  the  cavity  containing  them  : 
the  visceral  layer  of  the  arachnoid  lying  everywhere  immediately  on  the  proper 
envelope  of  the  nervous  mass — the  pia  mater — except  at  the  sub-arachnoid  spaces  ; 
and,  on  the  other  hand,  the  arachnoid  cavity  can  scarcely  be  said  to  exist  while 
the  dura  mater  is,  as  it  were,  glued  to  the  cranial  walls,  and  in  reality  constitutes 
their  internal  periosteum. 

The  brain  has,  therefore,  no  room  to  move  in  its  receptacle,  but  is  maintained 
in  it  in  an  almost  absolutely  immovable  condition,  which  coincides  exactly  with 
that  of  the  sutures  or  cranial  articulations. 

Weight. — The  total  weight  of  the  brain,  in  average-sized  animals,  may  be 
inferred  from  the  following  figures  :  Horse,  22  oz.  15  drams  ;  Ass,  12  oz.  11 
drams  ;  Ox,  16  oz.  15  drams  ;  Sheep  and  Goat,  4  oz.  9^  drams  ;  Pig,  5  oz.  10 
drams  ;  Dog,  6  oz.  5i  drams  ;  Cat,  1  oz.  1  dram  ;  Rabbit,  5i  drams. 

Cornevin  has  remarked  that  the  cranial  capacity,  if  not  the  weight  of  the 
brain,  is  greater  in  the  female  than  in  the  male  of  the  domestic  species  and  breeds 
of  animals. 

In  comparing  these  figures  with  those  of  the  spinal  cord,  it  will  be  seen  that 
the  relative  weight  of  the  latter  to  that  of  the  encephalic  mass  differs  notably  in 
the  several  animals,  being  highest  in  the  Dog,  and  lowest  in  the  Rabbit.  The 
relations  in  each  species,  between  the  two  divisions  of  the  nervous  system,  are  the 
following  :  Dog,  1  :  5-14  ;  Cat,  1  :  3-75  ;  Sheep  and  Goat,  1  :  2'60  ;  Ass,  1  : 
2-40  ;  Pig,  1  :  2-30  ;  Horse,  1  :  2-27  ;  Ox,  1  :  2-18  ;  Rabbit,  1  :  2.  We  give 
these  numbers,  as  it  has  always  been  attempted  to  establish,  in  the  predominance 
of  the  brain,  the  cause  of  the  development  of  intelligence,  and  that  the  best 
measure  of  this  predominance  is  really  the  relation  of  the  spinal  cord  to  the  brain. 
It  has  also  been  attempted  to  measure  this  predominance  of  the  brain  by  compar- 
ing its  weight  with  that  of  the  entire  body  ;  but  it  is  sufficient  to  cast  one's  eye 
over  the  tables  drawn  up  with  this  view  in  several  anatomical  and  physiological 
works,  to  be  convinced  that  this  basis  does  not  possess  all  the  value  desirable. 

Preparation  of  the  train. — To  study  the  brain,  it  is  necessary  to  extract  it  from  its  bony 
receptacle ;  a  result  achieved  in  two  ways.  The  first  consists  in  opening  tlie  roof  of  the 
cranium  by  hammer  and  chisel,  after  removing  from  its  exterior  all  the  parts  covering  it,  or 
which  are  in  its  vicinity.  The  dura  mater  is  then  excised  with  scissors,  and  the  brain,  which  is 
thus  directly  reached,  is  completely  isolated  by  raising  its  posterior  extremity,  and  cutting  from 
behind  to  before  all  the  nerves  passing  through  the  foramina  at  the  base  of  the  cianium,  with 
the  pituitary  stem,  as  well  as  the  extremity  of  the  olfactory  bulbs.  This  method  is  very  ex- 
peditious, but  it  sacrifices  the  pituitary  gland,  which  remains  firmly  embedded  in  the  sella 
Turcica — an  inconvenience  we  obviate  by  resorting  to  the  second  procedure.  In  this,  the 
cranium  is  opened  by  its  base  or  floor,  after  separating  tiie  head  from  the  trunk,  cutting  away 
the  lower  jaw.  tongue,  and  os  hyoides.  and  excising  all  the  soft  parts  so  as  to  expose  the  bony 
surfaces.  The  head,  thus  prepared,  is  held  by  an  assistant,  the  roof  of  the  cranium  resting 
on  a  table  or  block.  Armed  with  a  chisel  and  hammer,  the  operator  first  removes  the 
zygomatic  arches  and  the  styloid  processes  of  the  occipital  bone,  then  the  condyles  of  this  bone, 
the  basilar  processes,  and  the  sphenoid,  palatine,  and  ethmoid  bones,  returning  to  the  lateral 
portions  of  the  cranium,  which  are  chiselled  away  in  succession  from  the  occipital  to  the  eth- 
moid bones.  The  brain,  being  suflBciently  exposed,  is  relieved  from  its  dura  mater  as  in  the 
first  method,  and  raised  in  the  left  hand  to  destroy,  by  means  of  scissors  held  in  the  right  hand, 
the  attachments  which  yet  fix  it  to  the  cranial  roof,  and  which  are  chiefly  the  veins  that  open 
into  the  sinuses  of  the  dura  mater.  In  afterwards  excavating  the  ethmoidal  fossae  with  the 
point  of  a  scalpel,  the  olfactory  bulbs  are  detached  and  the  mass  is  free.  This  procedure 
51 


766  TEE  CENTRAL  AXIS  OF  TEE  NERVOUS  SYSTEM 

is  more  diflScnlt  than  the  first,  bnt  possesses  several  advantages  over  it;  for  not  only  do  we 
preserve  the  pituitary  gland,  but  have  the  ethmoidal  lobes  more  intact,  and  may  also  have, 
if  desired,  the  ganglia  of  the  cranial  nerves,  with  a  more  or  less  considerable  portion  of  the 
nerves  themselves. 

After  indicating  the  methods  for  extracting  the  brain  from  its  bony  case,  we  ought  to  say 
some  words  as  to  tlie  course  to  be  pursued  in  order  to  study  it  successfully.  To  do  this  it  is 
advantageous  to  have  two  brains ;  one  of  these  should  be  hardened  by  steeping  it  for  some 
weeks  in  alcoliol  (or  methylated  spirit),  or  in  water  to  which  has  been  added  a  tenth  part  of 
nitric  acid.  This  hardening  contracts  the  nerve  substance,  and  causes  the  cavities  and  reliefs 
to  appear  more  manifest.  (It  is  a  good  plan  to  place  the  brain,  base  uppermost,  in  a  suitable 
vessel,  and  if  a  piece  of  cloth  be  spread  beneath  it,  its  removal  therefrom  will  subsequently  be 
greatly  facilitated.) 

We  commence  by  examining  rapidly  the  whole  apparatus,  and  pass  immediately  to  the  study 
of  the  isthmus,  of  which  it  is  necessary  to  have  at  first  a  well-defined  idea.  We  therefore  take 
a  hardened  specimen,  and  isolate  this  portion  of  the  brain  in  the  manner  represented  in  Fig. 
425  ;  to  do  this,  it  suffices  to  cut  through  tlie  peduncles  of  tbe  cerebellum,  and  excise  the  cere- 
bral liemispheres  upwards  and  backwards;  the  remains  of  these  and  the  cerebellum  should  be 
preserved  for  an  analysis  of  their  structure.  The  isthmus  thus  isolated  is  fitted  for  an  examina- 
tion of  its  external  conformation  and  its  internal  cavities — the  ventricle  of  the  optic  layers  and 
the  aqueduct  of  Sylvius — into  which  we  may  penetrate  by  a  superior  longitudinal  incision. 

After  the  isthmus,  the  cerebellum  is  to  be  studied — in  its  external  conformation — on  an 
intact  specimen  ;  and  in  its  internal  conformation  and  structure  on  the  incised  piece. 

We  terminate  with  the  cerebrum,  the  superficies  of  which  is  soon  examined ;  its  interior 
should  be  studied  in  the  following  manner:  It  is  necessary  to  begin  by  demonstrating  the 
.  existence  of  ventricles  in  the  olfactory  lobes,  and  their  communication  with  all  the  other  in- 
ternal cavities  of  the  brain,  which  can  easily  be  done  by  the  inflation  of  one  of  these  organs  by 
means  of  a  straw  (or  dissecting-case  tube),  which  raises  the  pituitary  gland,  the  cerebrallobes 
and  the  cerebellum.  Tiien  we  pass  to  the  corpus  callosum,  which  is  exposed,  as  in  Fig.  434, 
by  a  horizontal  section  of  the  hemispheres  across  the  centrum  ovale.  The  corpus  callosum  of 
each  side  is  afterwards  excised  in  the  middle  line  to  reach  the  interior  of  the  lateral  ventricles, 
and  this  great  commissure  of  the  brain  ought,  after  studying  the  septum  lucidum,  to  be  cut 
across  in  the  middle  and  turned  over,  as  in  Fig.  435,  so  as  to  show  the  fornix.  The  foramen 
of  Monro  is  next  examined;  then  the  corpus  striatum,  hippocampi,  taenia  semicircularJB, 
choroid  plexus,  and  velum  interpositum.  which  are  exposed  by  the  ablation  of  the  hippocampi 
and  fornix  Lastly,  we  return  to  the  foramen  of  Monro  to  study  its  communication  with  the 
ventricle  of  the  (jptic  thalanii ;  it  will  be  well,  also,  to  again  examine  the  latter,  as  well  as  the 
aqueduct  of  Sylvius  and  the  ventricle  of  the  cerebellum,  which  we  arrive  at  in  dividing 
that  organ  through  the  middle  and  separating  the  halves. 

Two  longitudinal  and  vertical  sections,  one  median  (Fig.  428),  the  other  at  the  side  (Fig. 
431),  will  not  be  without  utility  in  the  study  of  these  particulars.  They  may  be  made  by 
means  of  a  saw,  the  brain  remaining  enclosed  in  the  cranial  cavity. 

(A  useful  implement  I  have  employed  for  removing  the  bony  casing  of  the  brain  without 
risk  of  injuring  the  latter,  is  a  chisel  with  a  thin  cutting  edge  which  is  slightly  concave,  the 
corners  being  smooth  and  rounded,  and  projecting  beyond  the  cutting  edge.) 

The  brain  may  be  preserved  for  an  indefinite  time  when  it  has  undergone  the  following 
preparation  :  1.  Place  it  for  from  twelve  to  fifteen  days  in  a  solution  of  nitric  acid  (10  to  100). 
2.  Then  leave  it  for  a  week  in  a  solution  of  bichromate  of  potassium  (20  to  1000).  3.  Afterwards 
sleep  it  for  three  or  four  days  in  alcohol  at  40°  4.  Take  it  from  the  alcohol,  allow  the  latter 
to  evaporate,  then  put  it  in  a  paraffin  bath  for  from  ten  to  fifteen  minutes,  not  allowing  it  to  boil. 
5.  Withdraw  it  from  the  paraffin  and  allow  it  to  dry.  After  this  series  of  preparations  the 
brain  shrivels,  but  it  preserves  its  shape,  and  will  not  putrefy. 

Article  II. — The  Isthmus  (or  Medulla  Oblongata). 

We  will  study  in  succession  the  external  and  internal  conformation  of  this 
part,  and  its  structure. 

External  Conformation  of  the  Isthmus. 

The  isthmus,  or  medulla  oblongata,  is  a  prismatic  prolongation  of  the  spinal 
cord  supporting  the  cerebellum,  and  terminating  in  the  cerebral  hemispheres  ; 


TEE  ISTHMUS.  767 

it  increases  in  size  from  behind  to  before,  and  may  be  considered  as  having 
ioxiT  faces  and  ttvo  extremities. 

The  inferior  face  (Fig.  424),  on  which  we  can  distinctly,  and  without  any 
preparation,  perceive  the  natural  limits  of  the  isthmus,  is  crossed  nearly  in  its 
middle  by  a  thick  fasciculus  of  arciform  fibres,  which  constitute  the  annular  pro- 
tuberance {protulerantia  annularis),  pons  Varolii,  or  mesocephalon  (or  nodus 
encephali).  All  the  portion  lying  behind  this  fasciculus  belongs  to  the  medulla 
oblongata.     That  in  front  forms  the  cerebral  peduncles  {crura  cerebri). 

The  superior  face  (Fig.  425),  covered  by  the  cerebellum  and  the  posterior 
extremity  of  the  cerebral  lobes,  is  more  mammillated  than  the  preceding.  Passing 
from  behind  to  before — on  the  superior  face  of  the  medulla  oblongata — there  is 
remarked  the  section  of  the  peduncles  of  the  ce^-ebellum,  the  vcdve  of  Vieussens,  the 
corpora  quadrigemina,  and  the  thalami  optici. 

The  lateral  faces  (Fig.  426),  concealed  in  their  anterior  part  by  the  hemi- 
spheres of  the  brain,  exhibit  the  profile  of  the  medulla  oblongata,  pons  Varolii, 
peduncles  of  the  cerebellum  (crura  cerebelli),  cerebral  peduncles  (crura  cerebri), 
corpora  quadrigemina,  and  thalami  optici. 

The  posterior  extremity  of  the  isthmus  belongs  to  the  spinal  bulb,  and 
continues  the  spinal  cord,  from  which  it  is  only  distinguished  artificially. 

The  anterior  extremity  is  enveloped  below,  and  on  each  side,  by  the  oblique 
fasciculi  which  form  the  two  optic  nerves,  and  beneath  which  are  insinuated  the 
fibres  of  the  isthmus  before  they  pass  into  those  parts  of  the  cerebral  hemispheres 
which  bear  the  name  of  corpora  striata. 

After  this  enumeration  of  all  the  parts  which  constitute  the  isthmus  of  the 
brain,  we  will  examine  them  in  detail,  and  in  the  following  order :  1.  Medulla 
oblongata.  2.  Po7is  Varolii.  3.  Crura  cerebri.  4.  Crura  cerebelli.  5.  Valve 
of  Vieussens.  6.  Corpora  quadrigemi?ia.  7.  Thalami  optici.  After  these  we 
will  describe  the  pineal  and  pituitary  glands — small  appended  lob^s  placed,  one  on 
the  superior,  the  other  on  the  inferior  face  of  the  isthmus.^ 

1.  Medulla    Oblongata   (Figs.  424,  425,  426). 

The  medulla  oblongata  constitutes  the  posterior  portion  of  the  encephalic 
isthmus  ;  it  succeeds  the  spinal  cord,  and  extends  forward  as  far  as  the  pons 
Varolii.  It  is  a  thick  peduncle  of  a  white  colour,  wider  before  than  behind,  flat- 
tened above  and  below,  and  having  four  faces — an  inferior,  superior,  and  two  lateral. 

Inferior  face  (Fig.  424). — This  face  rests  in  the  channel  of  the  basilar  process. 
Convex  from  side  to  side,  and  limited  anteriorly  by  a  transverse  fissure  which 
separates  it  from  the  pons  Varolii,  posteriorly  it  does  not  offer  anything  to 
distinguish  it  from  the  spinal  cord. 

'  There  is  far  from  being  any  agreement  ms  to  the  number  of  parts  which  ought  to  compose 
the  encephalic  isthmus,  some  authorities  making  more,  some  less.  The  limits  of  this  small 
apparatus  will,  nevertlieless,  be  found  perfectly  circumscribed  if  it  be  examined  in  the  lower 
animals,  and  particularly  in  the  Horse.  An  antero-posterior  section  of  the  brain,  made  to  one 
side  of  the  middle  line,  appears  to  us  all  that  is  needed  to  definitely  settle  the  point.  This 
section,  seen  in  Fig.  428,  shows  in  the  clearest  manner  that  the  encephalic  prolongation  of  the 
spinal  axis  extends  to  the  corpora  striata,  and  that  it  comprises  the  medulla  oblongata,  pons 
Varolii,  cerebral  and  cerebellar  peduncles  (or  crura),  the  corpora  quadrifremina.  and  the  thalami 
optici.  All  these,  then,  belong  to  one  and  the  same  system— the  medullary  prolongation,  which 
serves  as  a  bond  of  union  between  the  three  principal  masses  of  the  brain,  and  which  we  havu 
designated  the  isthmus.  It  may  be  added,  that  this  manner  of  considering  the  encephalic 
isthmus  perfectly  agrees  with  the  teachings  of  physiology. 


768 


THE  CENTRAL   AXIS   OF  THE  NERVOUS  SYSTEM. 


On  the  middle  line  there  is  a  well-marked  fissure — a  continuation  of  the 
inferior  fissure  of  the  cord — which  lies  between  two  very  elongated  prominences 
that  are  sometimes  but  Uttle  apparent,  and  which,  from  their  form,  are  named 
the  corpora  pyramidalia  (Fig.  424,  p,  p).     The  base  of  these  pyramids  touches 

Fig.  424. 


GENERAL    VIEW   OF   THE    HOESE'S   BRAIN   (INFERIOR   FACE). 

B,  Medulla  oblongata;  p,  p,  pyramids  of  ditto.  1,  Internal  root  of  the  spinal  accessory  nerve;  2, 
external  roots  of  ditto ;  2',  roots  of  the  pneumogastric  nerve  ;  3,  root  of  the  auditory  nerve ;  4,  root 
of  the  facial  nerve ;  5,  sixth  nerve  ;  6,  root  of  the  fifth  nerve ;  6',  6",  motor  and  sensory  roots  of 
the  fifth  nerve.  P.c,  P.c,  crura  cerebri.  7,  Third  nerve ;  8,  optic  commissure  ;  10,  fissure  of 
Sylvius;  11,  pituitary  gland  ;  12,  extra-venti'icgilar  nucleus  of  the  corpus  striatum  ;  13,  external 
root  of  the  olfactory  bulb;  14,  internal  root  of  ditto;  15,  olfactory  bulb;  16,  16,  grey  nuclei 
from  which  proceed  the  olfactory  nerves  ;  17,  lateral  lobe  of  the  cerebellum ;  18,  temporal  lobe 
of  the  brain ;  19,  first  temporal  convolution  ;  20,  lobule  of  the  curved  plait ;  21,  gyrus  rectus  ; 
22,  frontal  lobe  (antero-external  face). 

the  pons  Varolii,  and  their  apex  is  insensibly  lost,  posteriorly,  on  reaching  the 
spinal  cord. 

Outwardly  is  an  almost  plane  surface,  bordered  anteriorly  by  a  transveree 
band  (Fig.  330)  which  lies  immediately  behind  the  pons  Varolii ;  sometimes  it  is 
covered  for  the  greater  part  of  its  extent  by  a  very  thin  expansion  of  arciform 


THE  ISTHMUS.  769 

/ibres,  between  the  anterior  border  of  which  and  the  transverse  band — and 
particularly  in  pieces  that  have  been  hardened  by  alcohol  or  acidulated  water — is 
seen  a  slight  oblong  prominence  which  corresponds  to  what  in  Man  is  designated 
the  corpus  oUvare}  This  is  isolated  from  the  pyramid  by  a  longitudinal  groove, 
whence  emerge,  in  front,  the  roots  of  the  sixth  cranial  pair,  and  behind,  those  of 
the  twelfth  pair  ;  outwardly,  it  is  limited  and  separated  from  the  restiform  body 
by  the  origin  of  the  majority  of  the  roots  belonging  to  the  glosso-pharyngeal  and 
pneumogastric  nerves. 

Superior  face. — Covered  by  the  cerebellum,  it  is  channeled  in  its  middle  by  an 
excavation  (Fig.  424,  5),  which  constitutes  the  floor  of  the  fourth  ventricle. 
This  cavity  is  prolonged  forward  above  the  pons  Varolii,  between  the  crura 
cerebelli,  and  from  its  forming  an  angle  behind,  resembling  the  point  of  a  pen, 
it  has  been  named  the  calamus  scriptorius? 

Two  thick  cords,  prolongations  of  the  superior  fasciculi  of  the  medulla 
spinalis,  border  the  calamus  scriptorius  on  each  side ;  these  are  designated  the 
corpora  restiformia.^  Lying  together  at  their  posterior  extremities,  they  separate 
anteriorly,  so  as  to  represent  the  branches  of  a  V  (Fig.  425,  1). 

Lateral  faces. — Much  narrower  than  the  other  two,  and  showing  two  thick 
borders,  these  faces  give  the  profile  of  the  corpora  restiformia  (Fig.  426,  2), 
corpora  pyramidalia  (4),  and  the  fasciculus  between  these  two. 

2.  The  Pons  Varolii  (Figs.  425  ;  426,  5). 

TliQpons  Varolii — also  named  the  tuber  annulare,  or  mesocephalon — is- that  part 
of  the  brain  which  stands  out  prominently  across  the  isthmus,  between  the 
medulla  oblongata  and  the  crura  cerebri,  and  which  is  lodged  in  the  anterior 
depression  of  the  basilar  process. 

It  is  a  semicircular  band  of  white  transverse  fibres  thrown  across,  like  a 
bridge,  from  one  side  to  the  other  of  the  cerebellum.  It  has  two  faces.  The 
superior  face  is  adherent  to  the  fasciculi  of  the  medulla  oblongata,  which  is 
prolonged  to  form  the  crura  cerebri.^  The  infeiior  face  is  in  every  sense  convex, 
wider  in  its  middle  than  in  its  lateral  portions,  and  crossed  from  behind  to  before 
by  a  shallow  median  groove  for  the  basilar  artery.  It  offers  for  consideration 
two  borders  and  two  extremities. 

The  posterior  border,  sUghtly  convex,  is  separated  from  the  medulla  oblongata 
by  a  slight  groove. 

*  This  prominence  corresponds  to  the  corpus  olivare  of  Man  only  in  its  position,  as  it  has 
not  its  structure  ;  for  the  former  has  a  grey  nucleus  in  its  substance,  which  is  divided  into  two 
email  masses,  the  superior  of  whicli  is  found  in  Ruminants. 

*  In  the  bulbar  portion  of  the  calamus  gcriptarius,  are  seen  the  diversely  coloured  prominences 
which  correspond  to  the  origin  or  course  oi'  some  cranial  nerves.  These  are— viewing  them 
from  behind  to  before,  and  within  to  without,  commencing  at  the  middle  fissure — the  internal 
white  alu,  corresponding  to  the  nucleus  of  the  hypoglossal  nerve;  the  grey  ala,  corresponding 
to  the  nuclei  of  the  pneumogastric,  spinal,  and  glosso-pharyngeal  nerves ;  the  external  white 
ala,  situated  above  the  auditory  nucleus;  lastly,  the  eminentia  teres,  placed  between  the 
middle  fissure  and  the  crura  cerebelli,  lodging  the  bend  in  the  root  of  the  facial  nerve. 

The  point  of  the  calamus  scriptorius  is  covered  by  a  small  white  layer  extending  from  one 
border  to  the  other,  named  the  holt,  flie  cavity  beneath  this  being  designnted  the  ventricle  of 
Arantius,  at  the  bottom  of  which  is  usually  seen  the  opening  of  the  central  canal  of  the  spinal  cord. 

*  The  posterior  pyramids  are  formed  by  the  bulbar  prolongation  of  the  grey  column  of  the 
epinal  cord  ;  they  pass  to  the  right  and  left,  and  disappear  towards  the  posterior  crura  cerebelli ; 
they  expand  near  the  summit  of  the  calamus  scriptorius,  and  at  this  point  possess  very  great 
excitability. 

*  Some  authorities  carry  the  superior  face  of  the  pons  to  the  floor  of  the  fourth  ventricle. 


THE  CENTRAL  AXIS   OF   THE  NERVOUS  SYSTEM. 


The  anterior  border — also  convex,  but  indented  in  its  middle — largely  overhangs 
the  crura  cerebri,  which  are  limited  on  this  side  by  a  well-marked  fissure. 

The  extremities  are  bent  upwards  to  enter  the  substance  of  the  cerebellum,  in 
the  form  of  tAVo  thick  cords,  which  constitute  the  middle  crura  cerebelli  (Fig. 
425,  6).     They  exhibit  the  apparent  origin  of  the  trifacial  nerves. 

The  pons  Varolii  does  not  exist  in  Birds. 


Kig.  425. 


3.  The  Crura  Cerebri  (Figs.  425, 
426). 

These  are  two  very  large  white  fasci- 
culi, visible  at  the  inferior  surface  and 
sides  of  the  isthmus,  covered  superiorly 
by  the  corpora  quadrigemina  and  thalami 
optici,  and  continuous — above  the  pons 
Varolii — with  the  fibres  of  the  medulla 
oblongata  ;  while  their  anterior  extremi- 
ties enter  the  cerebral  hemispheres. 

These  peduncles  are  separated  from 
each  other  by  a  middle  fissure — the  inter- 
pedunndar — which  bifurcates  in  front  to 
circumscribe  the  fisiform  tubei'de  {corpus 
albicans,  hidhi  fornicis) — a  small,  single, 
and  rounded  elevation  of  a  white  colour 
like  the  peduncles,  covered  by  the 
pituitary  gland  (Fig.  423,  4),  the  root 
of  which  is  represented  by  the  tuber 
cinereum,  and  which  is  situated  in  front 
of  this  body  (see  Description  of  the  pitui- 
tary gland  on  p.  773).^ 

Behind,  the  crura  cerebri  are  limited 
by  the  anterior  border  of  the  pons 
Varolii.  In  front,  they  are  circumscribed 
by  the  optic  nerves,  which  pass  ob- 
liquely around  their  anterior  extremity 
and  join  on  the  middle  line  before  the 
tuber  cireneum,  to  form  a  commissure 
called  the  chiasma  (or  commissure)  of  the 
optic  nerves  (Fig.  424,  8).  On  the  sides, 
their  tissue  is  confounded  with  that  of 
the  corpora  quadrigemina  and  thalami 
optici,  which  are  superposed  on  the  crura 
cerebri.  It  may  be  remarked  that  the 
part  of  their  lateral  face  situated  below 

•  The  inferior  fHce  of  the  crura  cerebri  offer  some  more  interesting  details.  Tlius,  behind 
the  corpus  albicans  is  a  triangular  space— ^/se  interpedunmlar  perforated  layer  (locust  perforatus 
posticus,  pons  Tarini)  pierced  by  a  large  number  of  openings  for  the  posterior  group  of  arterioles 
given  off  from  the  circle  of  Willis.  On  each  crus  is  seen,  near  the  middle  line,  a  longitudinal 
fissure  from  which  issues  the  nerve  of  the  third  pair ;  outside  tliis  is  another  groove  that 
separates  a  fasciculus  of  white  fibres  from  a  mammilated  surface  of  a  grey  colour.  There  are 
also  observed  some  fasciculi  of  transverse  fibres  which  proceed  from  the  band  of  Reil.  The 
crura  cerebri  represent  two  stages,  separated  by  a  mass  of  grey  substance  named  the  locus  niger. 


SUPERIOR   VIEW  OF   THE  ENCEPHALIC   ISTHMUS. 

1,  1,  Corpora  restiformia ;  2,  section  of  the 
middle  cerebellar  peduncle  ;  3,  section  of  the 
posterior  cerebellar  peduncle ;  4,  anterior 
cerebellar  peduncle  ;  5,  floor  of  the  postt^rior 
ventricle  ;  6,  valve  of  Vieussens  ;  7,  7,  tuber- 
cula  testes ;  8,  8,  tubercula  nates ;  9,  9, 
thalami  optici;  10,  corpus  geniculatuin  in- 
ternum; il,  corpus  geniculatum  externum; 
12,  corpus  striatum  ;  13,  taenia  semicircularis; 
14,  pineal  gland;  15,  its  peduncle;  16,  com- 
mon anterior  opening  ;  17, 17,  anterior  pillars 
of  the  trigonum  or  fornix  ;  18,  trifacial 
nerve;  19,  facial  nerve;  20,  auditory  nerve; 
21,  glosso-pharyngeal  nerve ;  22,  pneumo- 
gastric  nerve ;  23,  spinal  nerve. 


TEE  ISTHMUS.  771 

the  tubercula  testes,  forms  a  well-defined  triangular  space,  designated  the  band  of 
Eeil,  lateral  triangular  fasciculus,  and  lateral  oblique  fasciculus  of  the  isthmus. 

4.  The  Crura  Cerebelli. 

The  cerebellum  is  attached  to  the  upper  face  of  the  isthmus,  by  two  short  and 
thick  lateral  funiculi  of  white  substance,  between  which  is  comprised  the  posterior 
ventricle  ;  these  constitute  the  crura  cerebelli. 

Three  distinct  fasciculi  enter  into  the  composition  of  each  of  these  cords — an 
anterior,  a  posterior,  and  a  middle. 

The  latter,  or  middle  cerebellar  peduncle  (crus  cerebelli  ad  pontem),  is  the 
largest  of  the  three.  It  is  formed  by  the  prolongation  of  the  extremities  of  the 
pons  Varolii  (Figs.  425,  2  ;  426,  6). 

The  posterior  cerebellar  peduncle  (crus  ad  medullam  oblongatum) — the  most 
slender— is  formed  by  the  restiform  body,  one  portion  of  which  is  reflected  below 
the  posterior  root  of  the  auditory  nerve  to  reach  the  substance  of  the  cerebellum. 
It  is  closely  united  to  the  preceding,  from  which  it  is  with  difficulty  distinguished 
(Fig.  425,  3). 

The  anterior  cerebellar  peduncle  {processus  e  cerebello  ad  testes)  (Fig.  425,  4)  is 
a  fasciculus  very  distinct  from  the  other  two,  related  by  its  inner  border  to 
the  middle  peduncle,  which  it  obliquely  crosses,  loses  itself  in  the  cerebellum  by 
its  supero-posterior  extremity,  arriving  behind  the  testes,  and  passing  beneath 
these  small  organs  by  its  antero-inferior  extremity,  along  with  the  band  of  Reil 
or  supero-lateral  fasciculus  of  the  cerebral  peduncles. 

In  studying  the  structure  of  the  cerebellum,  we  will  see  how  these  peduncles 
comport  themselves  in  its  interior. 

5.  Valve  of  Vieussens  (Fig.  425,  6). 

This  designation  is  given  to  a  very  thin,  white  layer  which  unites,  on  each 
side,  the  two  anterior  cerebellar  peduncles.  In  shape  it  is  nearly  a  parallelogram. 
Its  superior  face  is  covered  by  the  cerebellum  ;  the  inferior  concurs  in  forming 
the  roof  of  the  cerebellar  {fourth)  ventricle.  The  two  lateral  borders  are  joined 
to  the  peduncles  which  this  valve  unites  ;  the  anterior  is  attached  behind  the  testes  ; 
while  the  posterior  adheres  to  the  anterior  vermiform  process  {linguetta  laminosa) 
of  the  cerebellum. 

Gall  has  considered  this  layer  as  a  commissure  of  the  anterior  cerebellar 
peduncles,  and  we  think  rightly  ;  for  we  see  it  formed  almost  exclusively  of 
transverse  fibres  which  run  from  one  of  these  peduncles  to  the  other.  These 
fibres  are  most  apparent  in  front,  where  the  membrane  is  much  thicker  ;  behind, 
they  are  mixed  with  some  longitudinal  fasciculi. 

6.  Corpora  Quadrigemina  or  Bigemina  (Figs.  425,  7,  8  ;  426,  8,  9). 

These  are  four  round  eminences,  placed  in  pairs,  which  surmount  the  cerebral 
peduncles  behind.  The  two  posterior,  the  smallest,  are  also  named  the  tubercula 
testes,  and  the  anterior  pair  the  tubercida  nates. 

The  posterior  corpora  quadrigemina,  or  tubercula  testes,  are  related,  in  front, 
to  the  anterior  eminences  ;  behind,  to  the  anterior  cerebellar  peduncles  and  the 
valve  of  Vieussens,  from  which  they  are  separated  by  a  transverse  groove,  at 
the  bottom  of  which  arise  the  pathetici  nerves.     An  oblique  band  unites  them, 


772  TEE  CENTRAL  AXIS  OF  TEE  NERVOUS  ST8TEM. 

outwardly,  to  that  portion  of  the  optic  layer  named  the  corpus  geniculatum 
internum ;  while  they  limit,  externally,  the  bands  of  Reil. 

The  anterior  corpora  quadrigemina,  or  tubercula  nates,  are  distinguished  from 
the  preceding  not  only  by  their  larger  volume,  but  by  their  colour,  which  is  grey, 
that  of  the  testes  being  white.  They  are  also  rounder,  nearer  each  other,  and 
covered  by  the  cerebral  hemispheres  ;  while  the  posterior  rather  lie  beneath  the 
cerebellum.     A  curved  groove  isolates  them,  in  front,  from  the  thalami  optici. 

7.  Thalami  Optici  (Fig.  425,  9). 

This  name  is  given  to  that  part  of  the  upper  face  of  the  isthmus  which  is 
situated  in  front  of  the  corpora  quadrigemina.  These  thalami  are,  therefore, 
placed  above  the  anterior  part  of  the  cerebral  peduncles. 

Larger  altogether  than  the  corpora  quadrigemina — and  more  so  before  than 
behind— each  exhibits  a  grey,  slightly  convex,  and  very  irregularly  quadrilateral 
surface,  covered  by  the  velum  interpositum,  which  separates  it  from  the  cornu 
Ammonis  {pes  hippocampi),  and  from  the  posterior  pillars  of  the  fornix,  beneath 
which  they  are  placed. 

Imvardlij,  they  incline  towards  each  other  in  forming  on  the  middle  line 
a  somewhat  deep  fissure,  in  which  runs,  from  before  to  behind,  two  white 
longitudinal  bands  that  will  be  noticed  hereafter  as  the  anterior  peduncles  of  the 
pineal  gland.  This  fissure  enters,  behind,  the  common  posterior  opening  {foramen 
commune  posterius)  ;  in  front,  into  the  common  anterior  opening  {forammi  commune 
anterius) — orifices  which  will  be  described  with  the  interior  of  the  isthmus. 

Outwardly,  each  thalamus  opticus  shows  two  prominences  called  the  corpora 
geniculata,  from  which  arise  the  second  pair  of  nerves ;  placed  one  before  the 
other,  the  posterior  nearer  the  middle  line  than  the  anterior,  these  two  projections 
are  distinguished  as  external  and  internal.  The  corpus  geniculatum  externum  is 
•  always  more  voluminous,  better  defined,  and  situated  on  a  more  elevated  plane 
than  the  corpus  geniculatum  internum,  which  is  united  to  the  posterior  corpora 
quadrigemina  by  an  oblique  band  (Figs.  425  ;  426,  10,  11). 

Behind,  the  thalami  optici  appear  to  be  notched  to  receive  the  nates,  which 
they  slightly  enclose. 

In  front,  they  are  separated  from  the  coi-pus  striatum  by  a  groove,  at  the 
bottom  of  which  is  a  narrow  strip  named  the  semicircular  band  {taenia  semi- 
circularis). 

8.  Pineal  Gland,  or  Conarium  (Epiphysis  Cerebri)  ^  (Fig.  425,  14). 

This  name  has  been  given  to  a  small  tubercle  of  a  reddish-brown  colour,  in 
the  form  of  a  pine-cone,  enveloped  by  a  duplicature  of  pia  mater  from  the  velum 
interpositum,  with  its  apex  upwards,  and  its  base  resting  on  the  common 
posterior  opening  {foramen  of  Monro),  which  it  closes,  and  around  which  it  is 
attached  by  a  circular  ridge. 

From  this  lamella  is  detached,  in  front,  two  fibrous  cords — the  anterior 
peduncles  of  the  conarium  (or  habence).     These  (Fig.  425,  15)  are  two  narrow 

'  This  organ,  and  the  next  to  be  described,  do  not  really  belong  to  the  isthmus  system,  but 
rather — as  has  been  already  mentioned — to  the  appended  glands  which  should  receive  separate 
description.  The  first  is  probably  the  vestige  of  a  rudimentary  eye,  the  second  that  of  a 
lymphatic  gland.  (It  appears  to  be  now  conclusively  established  that  the  pineal  body  is  the 
representative  of  an  ancestral  form  of  eye — most  clearly  demonstrated  in  certain  lizards.) 


THE  ISTHMUS.  773 

white  bands,  which  commence  at  the  base  of  the  pineal  gland,  and  are  directed 
forward  parallel  to  each  other,  in  the  bottom  of  the  fissure  of  the  thalami  optici, 
to  which  they  firmly  adhere.  On  arriving  at  the  anterior  common  opening,  they 
become  attached  to  the  anterior  pillars  of  the  crura  of  the  fornix.  Sometimes 
they  are  very  narrow,  and  separated  by  an  interval ;  but  more  frequently  they  are 
relatively  wide,  and  immediately  in  contact  on  the  median  line. 

The  conarium  is  far  from  always  offering  the  same  volume ;  it  has  been 
shown  in  its  usual  dimensions  in  Fig.  425,  and  in  Fig.  429  it  is  shown  as 
incomparably  larger. 

The  tissue  of  the  pineal  gland  is  greyish  in  colour,  and  coiii-ains  more  or  less 
numerous  calcareous  granules.     In  the  midst  of  its  connective  tissue  are  vesicles 

Fig.  426. 


LATERAL   VIEW   OF   THE    ISTHMUS. 

1,  Medulla  oblongata;  2,  corpus  rectiforrae  ;  3,  lateral  fasciculi  of  the  medulla  oblongata  ;  4,  inferior 
fasciculus,  or  corpus  pyramidale;  5,  pons  Varolii;  6,  middle  peduncle  of  the  cerebellum;  7, 
cerebral  peduncle  (crus  cerebri);  8,  testis;  9,  natis ;  10,  corpus  geniculatum  intesnum  ;  11, 
corpus  geniculatum  externum;  12,  optic  nerve;  13,  fourth  nerve  resting  on  the  band  of  Reil ; 
14,  sensitive  root  of  the  trigeminal  nerve;  15,  its  motor  root;  16,  facial  nerve;  17,  auditory 
nerve. 

filled  with  polyhedral  cells  ;  it  is  in  the  centre  of  these  vesicles  that  are  found — in 
old  animals — mineral  concretions  (brain  sand — acervuJus  cerebri).  Many  anatomists 
consider  this  body  a  vascular  gland  ;  while  others  regard  it  as  a  nervous  organ, 
which  has  relations  with  the  brain  through  the  medium  of  its  anterior  peduncles. 

9.  Pituitary  Gland  (Figs.  424,  11  ;  429,  19). 
The  pituitary  gland — also  named  the  hypophysis  cerebri  and  supra-sphmioidal 
appendage — is  a  small  disc-shaped  tubercle,  fixed  to  the  anterior  extremity  of 
the  interpeduncular  fissure  by  the  pituitary  stem  {infundibulum)  and  the  tub&r 


a.  The  tuber  cinereum  is  a  little  eminence  of  a  grey  colour,  situated  in  the 
middle  line,  between  the  corpus  albicans  and  the  chiasma  of  the  optic  nerves,  at 
the  anterior  limit  of  the  isthmus.  This  eminence  is  hollow,  and  its  cavity  is 
nothing  more  than  a  diverticulum  of  the  middle  ventricle. 


774  THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 

h.  The  infimdihulum  is  only  a  short  conical  prolongation,  with  its  base  attached 
to  the  tuber  cinereum,  and  its  apex  to  the  superior  face  of  the  pituitary  gland. 
The  cavity  of  the  tuber  cinereum  is  continued  into  the  infundibulum,  and  termi- 
nates in  a  cul-de-sac  towards  its  summit.  This  prolongation,  also  formed  of  grey 
substance,  is  distinguished  by  its  great  fragility  ;  so  that  it  requires  some  care  to 
preserve  it  intact  when  opening  the  cranium  at  its  base. 

c.  The  pituitary  gland  is  lodged  in  the  sella  Turcica,  where  it  is  enveloped  by 
the  supra-sphenoidal  duplicature  of  dura  mater.  It  is  a  small,  nearly  circular 
body,  flattened  above  and  below,  and  more  or  less  thick,  according  to  the  subjects. 

Its  inferior  f me  rests  on  the  sphenoid  bone  through  the  medium  of  the  dura 
mater,  to  which  it  is  strongly  adherent ;  the  nqjerior  covers  the  corpus  albicans, 
with  a  portion  of  the  cerebral  peduncles,  and  in  front  receives  the  insertion  of 
the  pituitary  stem.  Its  circumference  is  related  to  the  supra-sphenoidal  duplicature, 
the  interior  of  which  forms  the  cavernous  sinus. 

There  is  no  cavity  in  the  pituitary  gland. 

The  matter  composing  it  is  yellow  in  the  anterior  half  of  the  organ,  and 
brown  in  its  posterior  portion.  Its  structure  resembles  that  of  the  supra-renal 
capsules,  and  there  is  a  tendency  to  regard  it  as  a  lymphatic  organ  (though  it 
has  been  surmised  that  it  may  have  a  function  in  connection  with  the  blood- 
supply  to  the  brain). 

Internal  Conformation  of  the  Isthmus  (Figs.  427,  428). 

The  isthmus  is  hollowed  at  the  thalami  optici  by  a  central  cavity,  named  the 
middle  (or  thvrcV)  ventrich,  which  is  extended  backwards  beneath  the  corpora 
quadrigemina  by  a  canal — the  aqueduct  of  Sylvius ;  this  opens,  below  the  valve 
of  Vieussens,  into  the  posterior  (or  fourth)  ventricle — another  cavity  comprised 
between  the  cerebellum  and  medulla  oblongata.  These  three  diverticuli  will  be 
studied  in  succession. 

1.  Third  or  Middle  Ventricle,  or  Ventricle  of  the  Thalami  Optici 
(Fig.  429,  13). 

The  middle  ventricle  is  an  irregular  cavity,  elongated  from  behind  to  before, 
depressed  on  each  side,  and  offering  for  study  two  ivalls,  a  floor,  a  roof  and  two 
extremities. 

The  two  walls  are  smooth,  nearly  plane,  or  very  slightly  concave  from  above 
to  below. 

The  floor  is  extremely  narrow,  and  only  forms  a  channel,  the  bottom  of  which 
corresponds  to  the  interpeduncular  fissure — which  is  nearer  in  front  than  behind— 
and  to  the  corpus  albicans  and  tuber  cinereum.  The  cavity  of  the  latter  (Fig. 
429,  20),  prolonged  into  the  pituitary  stem,  communicates  with  the  middle 
ventricle,  and  assists  in  its  formation. 

The  roof,  as  narrow  as  the  floor,  and,  like  it,  nothing  but  a  channel,  is  con- 
stituted by  the  two  thalami  optici,  which  are  joined  to  one  another  above  the 
ventricle,  forming  a  thick  grey  commissure  (Fig.  429,  16).  It  is  terminated  at 
its  extremities  by  the  two  orifices  already  noted  as  the  posterior  and  anterior 
common  foramina.  The  posterior  common  foramen  (Fig.  429,  15)  commences 
behind  the  grey  commissure,  and  terminates  at  the  base  of  the  pineal  gland  by 
an  irregularly  expanded  cid-de-sac.     It  is  Hmited  behind  by  the  posterior  tvhite 


THE  ISTHMUS. 


775 


commissure — a  thin  fasciculus  of  transverse  fibres  placed  in  advance  of  the  corpora 
quadrigemina,  above  the  entrance  to  the  aqueduct  of  Sylvius  (or  iter  a  tertio  ad 
quartum  ventrindum),  the  extremities  of  which  are  lost  in  the  substance  of  the 
thalami  optici  (Fig.  427,  9).  The  anterior  common  foramen,  also  designated  the 
foramen  of  Monro  (and  iter  ad  infundibulum)  (Fig.  429,  14),  is  the  medium  of 
communication  between  the  middle  and  lateral  ventricles,  and  affords  a  passage 
to  the  vascular  cord  which  unites  the  two  choroid  plexuses.  It  is  pierced  in 
front  of  the  grey  commissure,  beneath  the  summit  of  the  fornix,  the  two  pillars 
of  which  concur  to  circumscribe  it,  and  between  which  is  seen  the  anterior  ivhite 
commissure.  This  is  a  small  band  of  white  transverse  fibres,  analogous  to  that 
which  constitutes  the  posterior  commissure,  but  thicker,  and  passing  in  front  of 
the  anterior  pillars  of  the  fornix,  its  extremities  entering  and  becoming  lost  in 
the  corpus  striatum  on  each  side. 

The  posterior  extremity  of  the  middle  ventricle — narrower  than  the  anterior, 
and   placed    on   a   more    elevated 

plane— is  continuous  with  the  aque-  F'i?  ■iS? 

duct  of  Sylvius,  the  entrance  of 
which  (Fig.  427, 10)  is  beneath  the 
posterior  commissure,  towards  the 
common  foramen. 

The  anterior  extremity,  more 
dilated  than  the  posterior,  is  situ- 
ated immediately  above  the  optic 
chiasma,  and  is  only  separated  from 
the  bottom  of  the  great  interlobular 
fissure  of  the  brain  by  a  small  and 
very  thin  grey  lamina  attached  to 
that  chiasma,  and  for  this  reason 
named  by  writers  the  grey  root  of 
the  optic  nerves.  This  lamina 
(lamina  cinerea)  is  readily  seen  when 
the  optic  commissure  is  turned  back 
on  the  pituitary  gland  ;  it  is  suf- 
ficient to  traverse  this  to  enter  the 
middle  ventricle. 

The  ependymis,  which  forms  the 
wall  of  the  central  canal  of  the 
spinal  cord,  also  lines  the  walls  of 

this  cavity  ;  through  the  aqueduct  of  Sylvius,  it  is  prolonged  into  the  posterior 
(or  fourth)  ventricle  ;  by  the  foramen  of  Monro  it  passes  into  the  lateral 
ventricles,  and  thence  into  the  spaces  in  the  middle  of  the  olfactory  lobes. 


TRANSVERSE   SECTION   OF   THE   BRAIN   AT   THE 
POSTERIOR   COMMON    FORAMEN. 

White  substance  of  the  hemisphere,  or  centrum 
ovale  of  Vieussens  ;  2,  2,  grey  substance  forming 
the  external  layer  of  the  convolutions;  3,  section 
of  the  corpus  callosum  ;  4, 4,  interior  of  the  lateral 
ventricles ;  5,  section  of  the  great  vena  Galeni  ; 
6,  6,  cerebral  peduncles ;  7,  7,  section  of  the 
isthmus ;  8,  posterior  common  foramen ;  9,  pos- 
terior white  commissure ;  10,  entrance  to  the 
aqueduct  of  Sylvius. 


2.  Aqueduct  of  Sylvius  (Fig.  429,  6). 


This  is  a  longitudinal  median  canal,  passing  beneath  the  corpora  quadrige- 
mina, and  above  the  crura  cerebri. 

It  is  prismatic  in  shape  ;  its  anterior  extremity  communicates  with  the 
middle  ventricle,  and  the  posterior  opens  below  the  valve  of  Vieussens  into  the 
fourth  ventricle. 


776 


THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 


3.  The  Posterior  or  Cerebellar  Ventricle  (Fig.  429,  5). 

This  ventricle^  (or  sinus  rhomboidalis),  situated  beneath  the  cerebuUum, 
between  its  peduncles,  and  above  the  medulla  oblongata  and  pons  Varolii,  is  a 
cavity  elongated  from  before  to  behind,  and  ahnost  entirely  occupied  by  the 
vermiform  processes. 

Its  superior  ivall  is  formed  by  these  two  processes,  the  valve  of  Vieussens, 
and  that  of  Renault.  The  inferior,  or  floor  of  the  cavity,  is  represented  by  the 
depression  on  the  upper  face  of  the  medulla  oblongata,  and  which  is  prolonged 
in  front,  above  the  pons  Varolii,  to  near  the  testes.^ 

The  anterior  extremity  communicates  with  the  aqueduct  of  Sylvius.  The 
posterior  occupies  the  summit  of  the  calamus  scriptorius. 

Structure  of  the  Isthmus. 

The  isthmus,  being  only  a  prolongation  of  the  spinal  cord,  ought  to  resemble 

it  in  its  structure  ;    and   this  is,  in 


Fig.  428. 


fact,  what  is  observed,  particularly 
in  its  posterior  part,  the  common 
features  in  their  organization,  how- 
ever, disappearing  as  we  approach  its 
anterior  extremity. 

We  will  follow  the  distribution  of 
the  white  and  grey  substance  in  the 
isthmus. 

The  white  substance  includes  the 
longitudinal  tvhite  fibres,  as  well  as  the 
transverse  white  fibres.  Among  the 
first  may  be  mentioned  the  infero- 
lateral  columns.  These  decussate  at 
the  neck  of  the  medulla  oblongata,  in 


DISSECTION  OF  THE  MEDULLA  OBLONGATA,  SHOW- 
ING THE  CONNECTION  OF  ITS  SEVERAL  FASCI- 
CULI,   OR   STRANDS. 

A,  Corpus  striatum ;  B,  thalamus  opticus ;  C,  D, 
corpora  quadrigemina ;  E,  commissure  connecting 
them  with  the  cerebellum ;  F,  corpora  resti- 
formia  ;  P,  P,  pons  Varolii ;  st,  st,  sensory  tract ; 
mt,  mt,  motor  tract ;  g,  olivary  tract ;  p,  pyra- 
midal tract ;  og,  olivary  ganglion ;  op,  optic 
nerve  ;  3m,  root  of  third  pair  (motor)  ;  5s,  sen- 
sory root  of  the  fifth  pair. 


successive  layers ;  afterwards  they 
pass  along  the  inferior  middle  fissure, 
where  they  constitute  the  motor  por- 
tion of  the  pyrafnids  of  the  medulla 
oblongata,  and,  traversing  the  pons 
Varolii,  they  then  form  the  upper 
stage  of  the  crura  cerebri,  finally 
entering  the  corpora  striata. 

The  posterior  columns  also  decus- 
sate a  little  in  front  of  the  antero-lateral  columns.  When  this  intercrossing  of 
fibres  has  terminated,  they  form  the  deep  or  sensitive  portion  of  the  pyramids,  pass 
beyond  the  pons  Varolii,  constitute  the  upper  stage  of  the  crura  cerebri,  and  pass 
into  the  substance  of  the  thalami  optici. 

With  regard  to  the  inferior  columns  of  the  spinal  cord,  they  do  not  decussate 
on  entering  the  isthmus,  but  they  are  displaced  by  the  infero-lateral.  We  then 
find  them  in  the  centre  of  the  medulla,  beneath  the  grey  substance  in  the  floor  of 

'  As  the  cerebellum  concurs  in  the  formation  of  this  cavity,  it  would  perhaps  be  better  to 
defer  its  study  until  that  organ  has  been  described. 

*  For  the  features  of  this  region,  see  the  description  of  the  upper  face  of  tiie  medulla 
oblongata. 


THE  ISTHMUS.  ITl 

the  fourth  ventricle.    After  passing  through  the  pons  Varolii  and  the  upper  stage 
of  the  crura  cerebri,  they  enter  the  thalami  optici. 

To  the  longitudinal  fibres  which  continue  those  of  the  spinal  cord,  must  be 
added  the  fibres  of  the  corpora  restiformia  and  those  of  the  anterior  cerebellar 


The  corpora  restiformia  proceed  from  the  cerebellum,  of  which  they  form  the 
posterior  peduncles,  and  go  to  be  lost  on  the  surface  or  in  the  mass  of  the 
medulla  oblongata,  under  the  surface  of  the  white  transverse  tractus. 

The  anterior  cerebellar  peduncles  descend  from  the  cerebellum,  approach  the 
middle  line,  concur  in  the  formation  of  the  upper  stage  of  the  crura  cerebri,  and 
terminate  in  the  thalami  optici. 

To  this  important  system  of  white  longitudinal  fibres — a  prolongation  of  those 
of  the  spinal  cord — are  found  annexed  as  complimentary  elements  in  the  organi- 
zation of  the  isthmus,  several  systems  of  transverse  fibres  and  masses  of  grey 
substance.  The  following  is  a  summary  account  of  the  arrangement  of  these 
new  elements. 

In  proceeding  from  behind  to  before,  we  notice,  among  the  white  transverse 
fibres — 

1.  The  expansion  of  arciform  fibres  which  sometimes  covers  the  inferior  face 
of  the  medulla  oblongata  (Fig.  456,/)  :  their  superior  extremity  is  lost  on  the 
corpus  restiforme  ;  the  inferior  passes  into  the  intermediate  fissure  of  the  pyramid 
and  the  lateral  fasciculus.     It  is  derived  from  the  column  of  GoU  (Fere). 

2.  The  proper  fibres  of  the  pons  Varolii :  they  constitute  a  very  thick  semi- 
circular fasciculus,  the  extremities  of  which  form  the  middle  cerebellar  peduncles 
and  enter  the  cerebellum.  A  portion  of  this  fasciculus  envelops,  inferiorly  and 
laterally,  the  longitudinal  fibres  of  the  isthmus ;  the  other  passes  between  the 
two  portions  of  the  anterior  pyramids. 

3.  The  transverse  fibres  of  the  valve  of  Vieussens  and  those  of  the  white 
commissure,  which  have  been  already  noticed. 

The  grey  substance  of  the  isthmus,  which  now  remains  to  be  mentioned,  is  far 
from  being  so  abundant  as  the  white  substance,  and — as  in  the  spinal  cord — it  is 
principally  situated  deeply  in  the  substance  of  the  organ — at  least  in  the  greater 
number  of  points. 

If  the  grey  matter  of  the  cord  is  traced  into  the  medulla  oblongata,  it  will  be 
found  that  it  undergoes  modifications  in  its  distribution,  with  regard  to  the  course 
and  displacement  of  the  columns  of  fibres.  The  inferior  cornua  are  divided  into 
two  portions,  in  consequence  of  the  decussation  of  the  infra-lateral  columns.  Their 
bases  are  spread  along  the  middle  fissure  on  the  floor  of  the  fourth  ventricle, 
where  they  form  the  fiuclei  of  the  cranial  motor  nerves.  The  heads,  carried 
backwards  and  outwards,  constitute  the  motor  nuclei  of  the  mixed  cranial  nerves. 
The  superior  cornua  are  also  divided  into  two  portions  on  entering  the  medulla 
oblongata,  by  the  decussation  of  the  superior  columns.  The  base,  which  accom- 
panies the  central  canal  of  the  spinal  cord,  is  spread  on  the  floor  of  the  fourth 
ventricle,  and  forms — to  the  outer  side  of  the  nuclei  of  the  motor  nerves — the  grey 
mass  known  as  the  sensitive  nuclei  of  the  mixed  cranial  nerves.  The  head  is 
abruptly  thrown  outwards,  and  constitutes  the  sensitive  nucleus — the  origin  of 
the  large  branch  of  the  trigemini. 

To  these  grey  formations  must  be  added  the  masses  alien  to  the  spinal  cord. 
We  mention  :  the  pyramided  nuclei,  which  occupy  the  inner  border  of  the 
pyramids  ;  the  olivary  nuclei,  that  are  found  in  other  than  Soliped  animals  ;  the 


778  THE  CENTRAL  AXIS  OF  TEE  NERVOUS  SYSTEM. 

small  protuberential  masses,  disseminated  between  tlie  transverse  fibres  of  this 
region  ;  and  the  locus  niger — a  grey  mass  that  separates  the  two  stages  of  the 
crura  cerebri.  Finally,  there  is  a  small  mass  of  this  grey  substance  which  con- 
stitutes each  of  the  corpora  quadrigemini,  and  which  is  covered  by  a  thin  pellicle 
of  white  matter,  scarcely  visible  in  the  anterior  eminences. 

The  fhalami  optici  is  a  similar  mass,  though  more  volummous,  darker  coloured, 
and  without  a  layer  of  white  substance  on  its  superficial  face. 

Lastly,  nerve-cells  exist  between  the  various  layers  of  transverse  fibres  of  the 
pons  Varolii,  and  between  the  tubes  which  constitute  the  valve  of  Vieussens. 

Differential  Characters  in  the  Isthmus  op  the  other  Animals. 

Apart  from  its  volume,  the  isthmus  does  not  present  any  sensible  differences  in  Rumi- 
nants and  the  Pig.  In  the  Ox,  it  is  remarked  tliat :  1.  The  inferior  pyramids  of  the  medulla 
oblongata  are  more  prominent,  and  the  transverse  cords  parallel  to  the  pons  Varolii  more 
voluminous  than  in  Solipeds.  2.  The  crura  cerebri  are  short.  3.  The  optic  nerves  are  larger 
than  in  Solipeds.  4.  Tliere  is  a  large  developed  pituitary  gland,  excavated  by  a  wide  cavity, 
and  flattened  above  and  below.  5.  Lastly,  the  testes  are  more  conical,  and  less  distinct  from 
the  nates  than  in  the  animals  already  studied. 

In  the  Carnivora,  the  fourth  ventricle  is  very  wide  and  deep,  and  bordered  by  salient 
and  detached  corpora  restiformia.  Its  floor  is  marked  by  some  white  transverse  striae,  more 
apparent  than  in  the  Horse.  The  pons  Varolii  is  large ;  the  columns  of  the  medulla  oblongata, 
parallel  to  its  posterior  border,  are  as  developed  as  in  the  Horse,  without  taking  into  con- 
sideration the  difl"erence8  in  size  of  the  two  species.  The  pyramids  are  voluminous,  and  the 
olivary  bodies  well  defined.     The  testes  are  larger  than  the  nates. 

Asa  general  rule,  the  development  of  the  pons  Varolii  is  in  relation  to  that  of  the  lateral 
lobes  of  the  cerebellum. 

Comparison  of  the  Isthmus  of  Man  with  that  of  Animals. 

In  human  anatomy,  the  medulla  oblongata  and  isthmus  are  described  separately. 

The  first  shows  on  its  lower  face  a  well-marked  groove — a  continuation  of  that  of  the  spinal 
cord.  It  terminates  anteriorly  in  a  deep  fossa,  named  the  foramen  cascuin  of  Vicq-d'Azyr. 
The  pyramids  are  well  marked.  The  olivary  bodies  are  much  more  prominent  than  in  animals, 
and  are  also  distinguished  by  the  presence  of  a  grey  nucleus  in  tlieir  interior.  The  medulla 
oblongata  of  Man  has  not  the  transverse  band,  behind  the  pons  Varolii,  which  we  have  found 
in  the  Horse  (Fig.  424). 

With  regard  to  the  isthmus  proper,  it  contains  the  parts  in  front  of  the  medulla  oblongata 
already  studied  in  the  domesticated  animals.  Tlie  pons  Varolii  is  very  large ;  the  crura  cerebri 
are  separateil  from  each  other  by  a  groove,  at  the  bottom  of  which  are  several  small  openings. 
The  fourth  ventricle  is  deep,  is  bordered  by  well-developed  corpora  restiformia,  and  enclosed 
posteriorly  and  laterally  by  the  valves  of  Tarini  (velum  medullare  posterius).  On  its  floor  are 
remarked  transverse  strise  (lineas  transversae)  named  the  barbs  of  the  calamus  scriptorius,  which 
are  also  found  in  the  Dog.  The  testes  are  smaller  than  the  nates;  but  the  diflerence  in  their 
volume  is  less  considerable  than  exists  between  Solipeds  and  Ruminants.  Their  structure  is 
identical  with  that  already  described. 

Article  III. — The  Cerebellum. 

The  cerebellum,  or  posterior  enlargement  of  the  brain — is  the  single  mass 
supported  by  the  isthmus,  separated  from  the  cerebrum  by  the  transverse  parti- 
tion constituting  the  tentorium  cerebelli,  and  lodged  in  the  posterior  compart- 
ment of  the  cranial  cavity,  which  almost  exactly  gives  the  measure  of  its  volume. 

Leuret  has  ascertained  the  weight  of  this  organ.  On  the  average  it  weighs 
2i  ounces  in  the  entire  Horse  and  Mare,  and  2|  ounces  in  the  castrated  Horse. 
This  weight  is  to  that  of  the  brain  as  1  :  7"07  in  Stallions  ;  as  1  :  6-59  in 
Mares  ;  and  as  1  :  5'97  in  Geldings. 


THE  CEREBELLUM.  779 

1.    EXTEENAL   CONFOKMATION   OF   THE    CEREBELLUM   (FigS.  423,  433). 

The  cerebellum — isolated  by  dividing  its  lateral  peduncles  from  the  medulla 
oblongata  on  which  it  is  fixed — is  almost  globular  in  form,  slightly  elliptical,  and 
elongated  transversely  ;  while  its  external  surface  is  furrowed  by  a  great  number 
of  sulci,  the  two  principal  of  which  {sulci  horizontalis)  pass  in  a  circular  manner 
on  each  side  of  the  middle  line  around  the  organ,  dividing  it  into  three  lobes — a 
middle  and  two  lateral. 

The  three  lobes  of  the  cerebellum  are  not  always  readily  distinguished  from 
each  other,  in  consequence  of  the  shallowness  and  irregularity  of  the  two  sulci 
separating  them.  We  will,  nevertheless,  study  them  in  succession,  and  afterwards 
examine— in  a  general  manner — the  furrows  on  their  superficies. 

lliddle  lobe  (Fig.  423,  c^).— This  has  been  compared  to  a  silkworm  rolled 
in  a  circular  manner  around  the  middle  portion  of  the  cerebellum,  with  its  two 
extremities  joined— without  being  confounded — below  the  inferior  face  of  the 
organ. 

This  vermicular  disposition  is  not  well  defined  in  the  middle  and  superior 
portions  of  the  cerebellum,  where  this  lobe  is  always  more  or  less  subdivided  into 
large  multiple  and  irregular  lobules  ;  but  it  is  better  marked  before  and  behind, 
in  those  points  which  correspond  to  the  two  extremities  of  the  creature  selected 
as  a  term  of  comparison.  There  may  be  remarked  two  longitudinal  eminences 
transversely  annulated  on  their  surface,  and  curved  beneath  the  cerebellum  in 
such  a  way  as  to  come  in  contact  with  each  other.  These  eminences  constitute 
the  anterior  and  posterior  vermiform  processes.  Their  extremities  are  lodged  in 
the  fourth  ventricle,  the  roof  of  which  they  concur  in  forming. 

On  the  anterior  vermiform  process  the  posterior  border  of  the  valve  of 
Yieussens  is  inserted. 

The  posterior  vermicular  process  also  receives  the  insertion  of  a  valve  already 

mentioned,  and  which  must  be  again  briefly  referred  to.     This  valve described 

for  the  first  time  by  Renault— forms  a  lamina  of  a  certain  thickness  stretched 
above  the  calamus  scriptorius.  It  has  exactly  the  triangular  form  of  this  space, 
and  presents  a  superior  face  covered  by  the  posterior  vermiform  process  ;  an 
inferior  face,  studded  in  some  points  with  small  vascular  loops  ;  a  base  fixed  to 
the  vermis,  near  the  free  extremity  of  that  prominence,  and  to  its  lateral  parts  ; 
two  lateral  borders,  attached  to  the  corpora  restiformia  on  each  side  of  the 
calamus  scriptorius  ;  and  a  summit  corresponding  to  the  receding  angle  of  the 
excavation.  This  lamina  is,  doubtless,  nothing  more  than  a  septum  formed  by 
the  external  pia  mater,  and  on  which  is  extended  the  internal  membrane  that 
lines  the  walls  of  the  cerebellar  ventricle.  Otherwise,  it  is  in  direct  continuity, 
towards  its  base,  with  an  evident  dependency  of  the  pia  mater — the  plexus 
choroides} 

Lateral  lobes  (Fig.  423,  c^,  c^).— These  are  shaped  like  two  irregular  seg- 
ments of  a  sphere.  Their  surface,  fissured  and  lobulated  in  every  direction, 
presents  nothing  interesting  externally,  superiorly,  or  posteriorly.  It  is  by 
their  inferior  part  that  the  peduncles  enter  the  substance  of  the  cerebellum ; 
and  behind  this  point,  beneath  their  lateral  parts,  lies  the  cerebellar  plexus 
choroides. 

The  cerebellar  choroid  plexuses. — This  name  is  given  to  two  small  reddish 
granular  masses,  formed  of  vascular  loops,  elongated  from  before  to  behind, 

>  This  septum  is  represented  in  the  rudimentary  state  in  Man,  by  the  valvulx  Tarini. 


780 


THE   CLNTBAL  AXIS  OF  THE  NERVOUS  SYSTEM. 


flattened  above  and  below,  and  comprised  at  their  internal  borders  between  the 
corpora  restiformia  and  the  inferior  face  of  the  lateral  lobes  of  the  cerebellum, 
to  which  they  are  strongly  adherent  by  their  superior  face.  These  two  plexuses 
are  joined  by  means  of  Renault's  valve,  which  is  united  to  them  towards  its 
base. 

Sulci  and  lobules  of  the  cerebellum. — On  examining,  in  a  general  manner,  all 
the  sulci  which  intersect  the  external  surface  of  the  cerebellum,  we  see  that  they 
penetrate  to  very  unequal  depths  in  the  substance  of  the  organ,  and  that  they 


Fig.  429. 


MEDIAN   AND    VERTICAI,   SECTION   OF   THE   BRAIN. 


1,  Section  of  the  medulla  oblongata ;  2,  ditto  of  the  pons  Varolii ;  ditto  of  the  crura  cerebri ;  4, 
ditto  of  the  cerebellum,  showing  the  arbor  vita;  5,  posterior  ventricle  covered  by  the  cerebellum  ; 
6,  aqueduct  of  Sylvius;  7,  section  of  the  valve  of  Vieussens  (the  figure  and  the  line  proceeding 
from  it  are  too  much  forward)  ;  8,  natis  ;  9,  internal  extremity  of  the  hippocampus  ;  10,  section 
of  the  pineal  gland  (it  is  as  voluminous  as  it  was  in  the  specimen  from  which  this  drawing  was 
taken)  ;  11,  great  vena  Galeni,  proceeding  from  the  velum  interpositum  and  choroid  plexus,  12  ; 
13,  middle  ventricle;  14,  foramen  of  Monro;  15,  common  posterior  foramen;  16,  grey  com- 
missure; 17,  anterior  white  commissure;  18,  section  of  the  corpus  albicans;  19,  ditto  of  the 
pituitary  gland;  20,  interior  of  the  pituitary  stem  communicating  with  the  middle  ventricle; 
21,  section  of  the  optic  chiasma ;  22,  ditto  of  the  fornix;  23,  ditto  of  the  corpus  callosum ;  24, 
septum  lucidura;  25,  cerebral  convolutions;  26,  olfactory  lobule. 

divide  it  into  successively  decreasing  segments,  of  which  Figs.  429  and  482  may 
furnish  a  sufficient  idea. 

There  is  at  first  a  certain  number  of  principal  lobules,  which  are  divided 
into  secondary  lobules  ;  and  these,  again,  are  in  their  turn  separated  into  short 
lamellae,  representing  the  extreme  limits  of  cerebellar  lobulation. 

Leuret  has  counted  178  lamellae  in  a  section  of  the  middle  cerebellar  lobe  of 
the  Horse.     In  this  animal  he  found  the  largest  number. 


2.  Internal  Conformation  and  Structure  of  the  Cereb"ellum. 

The  cerebellum  concurs — by  its  inferior  plane  and  the  internal  face  of  its 
peduncles— to  form  the  cavity  already  described  as  the  posterior  or  cerebellar 


TEE  CEREBELLUM. 


781 


ventricle ;  but  in  the  mass  of  the  organ  itself  there  is  no  trace  of  excavation  or 
other  peculiarity.  This  is  demonstrated  in  the  most  evident  manner  by  sections 
of  its  substance  made  either  in  an  antero-posterior  or  in  a  transverse  direction. 
"We  only  see  in  these,  traces  of  the  sulci  which  divide  the  organ  into  lobules  ;  and 
they  also  afford  evidence  as  to  the  structure  of  the  cerebellum,  showing  that — 
like  all  the  other  parts  of  the  cerebro-spinal  axis — it  is  formed  of  white  and  grey 
substance. 

The  latter — spread  over  the  entire  surface  of  the  organ — constitutes  the 
cortical  layer  of  the  different  segments  of  which  it  is  composed.  It  is  even 
prolonged  into  the  convolutions,  which  increase  the  surface-extent  of  the  cere- 
bellum. In  each  lobule  it  may  be  resolved  into 
superposed  layers,  parallel  to  the  layer  of  white 
substance  that  forms  the  nucleus  of  the  lobule  ; 
between  these  layers  of  grey  substance  is  a  very 
thin  mass  of  white  matter. 

The  white  substance,  enveloped  on  every 
side  by  the  grey,  forms  two  thick  nuclei 
occupying  the  centre  of  the  lateral  lobes,  and 
which  are  united  and  confounded  on  the  median 
line  in  the  texture  of  the  middle  lobe. 

These  two  nuclei — in  continuity  on  each 
side  with  the  cerebellar  peduncles — are  only 
their  prolongations  or  intercerebellar  portions. 
They  send  into  the  middle  of  each  principal 
lobule  a  long  and  thick  branch,  which  gives  off 
smaller  divisions  that  ramify  in  the  secondary 
lobules,  and  from  which  escape  a  new  series  of 
ramuscules  that  enter  the  smallest  segments  ; 
this  gives  to  the  cerebellum  a  beautiful  arboreal 
aspect,  justly  designated  by  the  older  anatomists  the  arbor  vitcR  (see  Figs.  429, 432, 
for  representations  of  the  arbor  vitce,  cerebelli). 

In  the  interior  of  these  nuclei  a  little  in  front,  there  sometimes  exists  a 
small,  slightly  grey  streak  ;  this  is  the  trace  of  the  corpus  rhomboideum  (or  corpus 
dentatum  of  Man). 

Stilling  has  noted  two  small  grey  nuclei,  which  are  symmetrical,  and  are 
situated  in  the  inferior  layers  of  the  middle  lobe. 

The  nuclei  of  the  white  substance  of  the  cerebellum  are  constituted  by  nerve- 
tubes,  which  are  intermixed  with  numerous  nuclei,  and  are  continuous  on  one 
side  with  the  crura  cerebelh,  and  on  the  other  tenninate  in  the  cells  of  the  grey 
substance. 

In  the  grey  streak  that  forms  the  corpus  rhomboideum,  is  a  great  number  of 
large  nerve-cells. 

With  regard  to  structure,  the  grey  matter  of  the  cerebellum  is  made  up  of 
three  layers  ;  the  superficial  is  very  rich  in  blood-vessels,  has  a  greyish  tint,  and 
is  composed  of  rounded  elements,  indeterminate  in  their  nature,  lying  in  an 
amorphous  substance  ;  the  middle  layer,  is  composed  of  Purkinje's  cells — large 
elements  disposed  in  a  single  row,  and  provided  with  ramifying  prolongations 
which  are  at  first  directed  to  the  preceding  layer,  and  are  then  reflected  downwards 
into  the  deep  layer,  where  they  are  perhaps  continuous  with  the  axis-cylinder  of 
the  nerve-tubes  of  the  white  substance.  The  latter — also  named  the  rust-coloured 
52 


ARRANGEMENT  OF  THE  LAYERS  AND 
CELLS  OF  THE  CENTRAL  GREY  MAT- 
TER OF  THE  CEREBELLUM. 

A,  White  matter.  1,  Granular  or  rust, 
coloured  layer  (substantia  ferruginea)  • 
2,  layer  of  Purkinje's  cells  ;  3,  super- 
ficial amorphous  layer. 


782 


THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 


layer  (substantia  ferrugineu) — has  a  yellow  tint,  and  a  mass  of  nuclei  pressed 
against  one  another. 

If  the  direction  of  the  white  substance  fibres  is  traced, 
Fig-  ■*3i-  it  will  be  found  that  some  form  an  intra-cerebellar  com- 

missural system,  while  others  constitute  a  radiation  system 
fy-i/r'i^^  that  unite  the  cerebellum  to  the  other  parts  of  the  brain. 

The  first  extend  from  one  corpus  rhomboideum  to  the  other, 
across  the  cerebellum,  or  in  following  the  middle  cerebellar 
peduncles.  The  second  represent  the  anterior  and  posterior 
cerebellar  peduncles  and  a  part  of  the  middle  peduncle. 
The  anterior  peduncles,  after  intercrossing,  pass  into  the 
thalami  optici  (red  nmlei  of  Stilling) ;  the  posterior  enter 
the  nuclei  of  the  restiform  bodies  and  ohvary  body,  where 
they  become  united  to  the  sensory  system  of  the  spinal 
cord  ;  lastly,  the  middle  ones,  after  intercrossing,  disappear 
in  the  grey  nuclei  of  the  pons  Varolii. 

The  prolongations  of  the  large  cells  in  the  cortex  cere- 
belli — also  named  the  cells  of  Purkinje — are  continuous  with 
the  fibres  of  the  white  substance. 


SECTION  OF  THE  COR- 
TICAL SUBSTANCE  OF 
THE   CEREBELLUM. 

a,Medullary  substance, 
showing  its  fibres; 
6,  substantia  ferru- 
ginea,  composed  of 
fibres  and  cell-nu- 
clei ;  c,  grey  surface, 
granular  at  the  sur- 
face, and  contain- 
ing large  multipolar 
branching  cells  near 
the  substantia  fer- 
ruginea. 


Differential  Characters  in  the  Cerebellum  of  other  than 
SoLiPED  Animals. 

The  external  and  internal  conformation  of  the  cerebellum  offers 
the  closest  analogies  in  the  domesticated  Mammalia.  In  all,  its 
volume,  compared  with  that  of  the  other  encephalic  lobes,  is  not  in- 
variable. Thus,  while  the  relation  between  the  weight  of  the  cere- 
bellum and  that  of  the  brain  of  the  Horse  is  as  1  to  7 ;  in  the  Ox  it  is 
as  1  to  9 ;  the  Dog  1  to  8 ;  the  Cat  1  to  6 ;  and  the  Sheep  1  to  3.  The 
cerebellar  cortical  convolutions  are  less  numerous  than  in  the  Horse. 
Leuret  has  found  175  lamellae  in  the  middle  cerebellar  lobe  of  the 
Ox,  77  in  the  Sheep,  66  in  the  Cat,  and  32  in  the  Rabbit.  These 
are  the  only  differences  to  be  noted. 

Comparison  of  the  Cerebellum  op  Man  with  that  of  Animals. 


In  Man,  the  encephalic  mass  being  enormous,  the  cerebellum  is 
absolutely  more  considerable  in  volume  than  in  the  larger  domesticated 
animals ;  though,  in  proportion  to  the  cerebral  hemispheres,  it  is 
smaller  than  in  the  Ox,  its  relation  to  the  latter  lobes  being  as  1  to  8. 

It  is  covered  by  the  occipital  lobes  of  the  brain ;  is  wider  than 
it  is  long,  and  projects  much  beyond  the  medulla  oblongata.  It  has 
three  lobes ;  but  these  are  only  visible  on  its  lower  aspect ;  on  the  opposite  face,  the  median 
lobe  is  depressed  and  concealed  beneath  the  lateral  lobes,  which  are  so  large  tiiat  they  have 
been  named  the  cerebellar  hemispheres.  The  fissure  which  separates  these  hemispheres  is 
named  the  great  middle  fismre  of  the  cerebellum ;  it  lodges  the  falx  cerebelli.  The  inferior 
vermis  forms  a  free  projection  in  which  is  the  fourtli  ventricle ;  this  is  termed  the  uvula  of  the 
cerebellum.  The  uvula  is  connected  at  each  side  with  the  valves  of  Tan/w'— laminae  of  nerve- 
substance  lodged  for  the  most  part  in  the  fourth  ventricle,  and  hidden  by  the  lower  face  of  the 
cerebellar  hemispheres.  Tlie  latter  constitute,  on  the  sides  of  the  medulla  oblongata,  two 
prominences  situated  one  below  the  other,  above  the  crura  cerebelli;  the  first  is  designated  the 
amygdala  or  tonsil,  the  second  the  pneumogastric  lobule  (oi  flocculus). 


Article  IV. — The  Cerebrum. 
The  cerebrum,  the  principal  portion  of  the  brain,  comprises  the  two  anterior 


THE  CEREBRUM. 


783 


lobes  or  hemispheres  of  that  apparatus — enlargements  which  are  elongated  in  the 
direction  of  the  great  diameter  of  the  head  and  cranial  cavity,  lie  beside  each 
other  in  the  middle  line,  and  are  united  at  their  central  part  by  a  transverse 
commissure,  and  by  the  isthmus,  the  anterior  extremity  of  which  penetrates 
their  substance  inferiorly  (see  Figs.  424,  429,  432  for  a  good  idea  of  this 
penetration). 

These  two  lobes  together  represent  an  ovoid  mass,  having  its  larger  extremity 
adjacent  to  the  cerebellum  ;  it  is  depressed  above  and  below  ;  deeply  divided 
above,  in  front,  and  behind  by  a  median  antero-posterior  tissure,  and  receives  in 
the  middle  of  its  inferior  face  the  insertion  of  the  crura  cerebri. 

This  mass — seven  to  nine  times  more  voluminous  than  the  cerebellum — fills  the 
anterior  compartment  of  the  cranial  cavity,  and  thus  occupies  the  greater  portion 
of  that  space. 

Leuret  has  found  that,  on  the  average,  it  weighs  in  the  Stallion,  15^  ounces  ; 
in  the  Mare,  14i  ounces  ;  and  in  the  castrated  Horse,  14  ounces  12i  drams. 

Fiff.  432. 


ANTERO-POSTERIOR    AND    VERTICAL    SECTION    OF    THE    BRAIN,  TO    ONE    SIDE    OF    THE    MEDIAN    LINE. 

1,  1,  Isthmus;  2,  medulla  oblongata;  3,  pons  Varolii;  4,  crus  cerebri;  5,6,  corpora  bigemina; 
7,  optic  thalamus;  8,  pituitary  gland;  9,  pituitary  stem;  10,  optic  nerve;  11,  cerebellum; 
12,  12,  cerebral  hemisphere;  13,  ventricle  of  the  hemisphere;  14,  corpus  striatum;  15,  cornu 
Ammonis;  16,  olfactory  bulb;   17,  ventricle  in  the  olfactory  bulb. 

It  offers  for  study  its  external  conformation,  its  internal  conformation,  and  its 
structure. 

ExTEENAL  Conformation  of  the  Cerebrum. 

Instead  of  examining  the  organ  in  mass,  with  regard  to  its  external  conforma- 
tion, we  will  first  consider  the  great  longitudinal  fissure  which  divides  it  length- 
ways ;  and  afterwards  study  its  two  lateral  halves,  or  cerebral  hemispheres,  which 
in  reality  constitute  two  symmetrical  organs. 


1.  The  Longitudinal  Fissure  (Figs.  423,  424), 

This  fissure  exists  throughout  the  entire  vertical  and  antero-posterior  circum- 
ference of  the  cerebrum,  but  does  not  everywhere  offer  the  same  arrangement. 


784  THE  CENTRAL   AXIS  OF  THE  NERVOUS  SYSTEM. 

On  the  superior  aspect  of  the  organ  it  is  very  deep,  and  when  the  two  hemispheres 
are  separated  to  discover  its  extent,  we  see  that  it  reaches  to  the  upper  face  of  the 
great  commissure — the  coi-pus  callosum.  Behind,  it  curves  between  the  posterior 
lobes  of  the  hemispheres,  but  without  corresponding  directly  with  the  posterior, 
thick,  rounded  margin  of  the  coi-pus  callosum,  above  which  there  is  a  feeble 
adhesion  between  the  two  halves  of  the  cerebrum,  forming  a  kind  of  bridge.  But 
in  front  it  passes  to  the  anterior  margin  of  this  commissm'e,  and  is  prolonged  in 
the  interval  between  the  anterior  lobes  of  the  hemispheres,  to  reach  the  inferior 
face  of  the  brain. 

Examined  inferiorly,  this  interlobular  fissure  is  well  defined  in  front,  where  it 
reaches  the  anterior  border  of  the  coi-pus  callosum  ;  but  behind,  on  leaving  the 
optic  commissure — and  which  marks  the  anterior  limit  of  the  isthmus — this  fissure 
appears  suddenly  to  stop.  This  is  because  it  becomes  considerably  enlarged,  and 
is  changed  into  a  vast  notch  which  admits  the  anterior  extremity  of  the  isthmus 
— or  rather,  it  bifurcates  to  pass  on  each  side  between  the  hemisphere  and  the 
anterior  extremity  of  the  spinal  prolongation,  at  first  crossing  the  optic  nerve, 
then  turning  round  the  crara  cerebri  and  corpora  bigemina,  above  which  its 
branches  unite,  and  are  confounded  with  the  undivided  part  of  the  fissure  that 
separates  the  posterior  lobes  of  the  hemispheres  (Fig.  424). 

There  exists,  then,  around  the  point  of  entrance  of  the  isthmus  into  the  cere- 
brum a  well-marked  Une  of  demarcation,  which  constitutes — above  and  laterally — ■ 
a  very  deep  fissure,  in  which  is  embedded  the  vascular  expansion  known  as  the 
velum  interpositum ;  this  space  is  designated  the  fissure  of  Bichdt,  or  great  {trans- 
verse) cerebral  fissure. 

The  longitudinal  fissure  receives  the  longitudinal  septum  of  the  dura  mater, 
or  falx  cerebri.  It  also  lodges  arteries  and  veins,  among  which  it  is  necessary  to 
distinguish  the  great  vena  Galeni,  which  ascends  from  the  bottom  of  the  fissure, 
after  passing  round  the  posterior  border  of  the  corpus  callosum. 


2.  The  Cerebral  Hemispheres. 

Preparation. — To  see  the  fissures,  sulci,  and  convolutions  of  the  brain,  the  organ  should  be 
macerated  for  some  days  in  a  solution  of  nitric  acid  (5  or  10  to  100  of  water).  On  removing 
it  from  this,  the  pia  mater  and  vessels  (ire  carefully  taken  away  and  the  brain  gently  dried, 
when  the  grooves  and  fissures  widen,  and  the  lobes  and  lobules  can  be  distinctly  seen. 

Each  hemisphere — or  lateral  moiety  of  the  cerebrum — represents  an  ovoid 
segment,  in  which  we  may  consider  four /aces  and  two  extremities. 

The  supei-ior  face  is  convex,  and  is  covered  by  the  roof  of  the  cranium,  which 
is  formed  by  the  frontal  and  parietal  bones. 

The  external — equally  convex  and  insensibly  confounded  with  the  adjacent 
faces — corresponds  to  the  lateral  walls  of  this  cavity — that  is,  with  the  squamous 
portion  of  the  temporal  bone,  the  parietal  and  frontal  bones,  and  the  ala  of  the 
sphenoid. 

The  inferior — irregularly  mammillated — rests  on  the  sphenoid  bone.  The 
intm-nal  is  plane,  and  for  the  greater  part  of  its  extent  is  related  to  the  other 
hemisphere  through  the  medium  of  the  falx  cerebri ;  it  is  in  its  central  and 
inferior  portion  that  the  union  of  the  two  halves  of  the  cerebrum  takes  place,  by 
means  of  the  great  cerebral  commissure  and  the  anterior  extremity  of  the 
isthmus. 

The  posterior  extremity  of  the  hemisphere  corresponds  to  the  cerebellum,  which 


THE  CEREBRUM.  785 

slightly  depresses  it,  and  from  which  it  is  separated  by  the  transverse  septum  of 
the  dura  mater  (tentorium). 

The  anterior  extremity — or  late — is  lodged  in  the  fossa  formed  on  each  side  of 
the  crista  galli  by  the  frontal  and  sphenoid  bones. 

The  most  important  peculiarities  to  be  noted  on  the  surface  of  the  hemi- 
spheres, are  the  convolutions,  which  we  will  now  describe. 

Cerebral  Convolutions.^ — These  are  the  portions  of  the  cerebral  cortex 
which  are  disposed  in  the  form  of  more  or  less  sinuous  ridges,  separated  from 
each  other  by  deep  grooves  or  fissures  {sulci). 

A  convolution  (or  gyrus)  may  include  several  plaits  or  folds — that  is,  several 
parts  separated  or  merely  indicated  by  shallow  grooves  ;  so  that  convolutions 
should  not  be  confounded  with  plaits. 

The  convolutions  are  not  independent,  strictly  speaking,  but  are  often  united 
to  those  adjoining  by  more  or  less  concealed  reliefs,  called  passage  plaits  (annec- 
tent  or  bridging  gyri)  ;  sometimes  two  or  more  are  very  ostensibly  connected  in 
this  way. 

The  convolutions  in  Solipeds  are  very  sinuous,  and  limited  by  deep  sulci ; 
some  of  these  latter — more  important  than  the  others  by  their  depth  and  constancy 
— are  named  ^sswres.  Notwithstanding  an  apparent  great  irregularity,  the  cere- 
bral convolutions  are  somewhat  constant  in  their  aiTangement  ;  so  that  it  is 
possible  to  describe  them  one  by  one. 

a.  Fissure  and  grooves. — On  the  inferior  face  of  the  brain  is  seen  a  transverse 
depression  at  the  optic  commissure  (Fig.  424,  10).  This  depression — named  the 
fissure  or  vcdley  of  Sylvius — passes  from  within  to  without,  and,  on  arriving  at  the 
side  of  the  brain,  divides  into  two  or  three  branches,  of  which  one — the  principal 
— is  inflected  backwards,  reaches  the  posterior  extremity  of  the  hemisphere,  and 
forms  the  superior  limit  of  a  lobe  named  the  temporal  or  sphenoidal  lobe  (Fig.  433, 
7).  The  other  one  or  two  branches  remain  slightly  buried  in  the  middle  part  of 
the  hemisphere  ;  they  lodge  the  divisions  of  the  middle  cerebral  artery. 

In  glancing  over  the  superior  surface,  there  will  be  perceived  a  deep  groov^e 
coming  from  the  great  longitudinal  fissure,  which  it  intersects  at  nearly  a  right 
angle.  This  groove — which  Leuret  has  named  the  crucial  fissure  (Fig.  423,  12) 
— is  surrounded  by  a  more  or  less  apparent  convolution,  designated  the  sigmoid 
gyrus  (Fig.  423,  11).  The  crucial  fissure  divides  the  superior  face  of  the  hemi- 
sphere into  two  parts — the  anterior  belonging  to  the  frontal  lobe,  the  posterior  to 
the  parieto-occipitcd  lobe. 

On  the  external  face  of  the  hemisphere  is  seen  a  deep  groove,  which,  com- 
mencing between  the  middle  and  posterior  branch  of  the  fissure  of  Sylvius,  is 
directed  upwards  in  a  curve,  the  concavity  of  which  is  inferior,  and  ends  in  the 
vicinity  of  the  crucial  fissure  (Fig.  433,  8,  8).  This  curved  groove  resembles  the 
fissure  of  Rolando.  If  looked  at  in  the  other  direction — from  before  to  behind 
— it  appears  to  bifurcate  in  its  middle  part,  and  the  upper  branch  {interparietal 

'  Leuret  believes  that  the  cerebral  convolutions  of  animals  are  arranged  after  a  certain 
type  (longitudinal  type)  essentially  different  from  the  human  type.  We  think  the  difference 
is  not  so  great  as  has  been  imagined ;  and  it  appears  possible  to  discover  in  the  brain  of  brutes 
if  not  the  longitudino-transverse  type,  at  least  the  tendency  to  this  type  observed  in  the  human 
brain.  In  the  description  given  above,  the  value  of  this  assertion  can  be  judged.  We  ought 
to  state  that  our  conclusions  are  based  on  the  comparative  examination  of  the  brains  of  adults 
and  foetuses,  on  tlie  distribution  of  the  blood-vessels,  and  on  the  physiological  experiments 
which  enabled  us  to  fix  the  position  of  the  excitable  zones  of  the  cerebral  cortex  in  the  larger 
Quadrupeds. 


786  TEE  CENTRAL   AXIS   OF   TEE  NERVOUS  SYS  1  EM. 

fissure)  passes  back  to  disappear  in  the  posterior  extremity  of  the  hemisphere  (Fig. 

423,  5).  The  fissure  of  Rolando  separates  the  frontal  from  the  parietal  lobe,  and 
the  portion  of  the  brain  comprised  between  its  bifm-cation  and  the  posterior 
branch  of  the  fissure  of  Sylvius,  forms  a  quadrilateral  lobe  (Figs.  423,  13  ;  433, 
10),  which  resembles  the  lobule  of  the  curved  plait  in  the  brain  of  Man. 

Lastly,  on  the  internal  face  of  the  hemispheres  is  found  the  inner  portion  of 
the  frontal  and  parieto-occipital  lobes,  and  a  long  convolution  that  accompanies 
the  coi-pus  callosum  (Fig.  429),  named  the  caUosal  convolution,  or  crested  con- 
volution {gyrus  fornicatus),  because  of  the  notches  on  its  upper  border  in  Man. 
It  is  separated  from  the  frontal  and  parieto-occipital  lobes  by  a  deep  groove 
— the   calloso-maryinal fissure. 

The  crested  convolution  commences,  in  front,  beneath  the  genu  of  the  corpus 
callosum  ;  behind,  it  is  inflected  downwards,  is  continuous  with  the  liippocampal 
convolution,  and  by  some  annectent  gyri  is  in  relation  with  the  posterior 
extremity  of  the  hemisphere. 

In  fine,  a  cursory  examination  of  the  surface  of  the  hemispheres  denotes  the 
presence  of  some  principal  grooves  Hmiting  three  lobes  and  a  lobule  ;  these  are  the 
frontal,  2)arieto-occi]ntal,  and  spJienoidal  lobes,  and  the  lobule  of  the  curved  plait} 

We  will  now  describe  the  convolutions  of  these  lobes  and  lobule. 

b.  Frontal  lobe. — This  lobe  presents  three  faces. 

The  inferior  face  {orbital  lobe)  is  triangular  (Fig.  424),  and  its  base  is  occupied 
by  the  fissure  of  Sylvius,  in  front  of  which  is  remarked  the  extra- ventricular  nucleus 
of  the  corpus  striatum  (Fig.  424, 12),  which  has  a  portion  of  itssm'face  perforated 
by  vascular  openings — the  locus  perforatus.  Near  the  summit  it  detaches  the 
olfactory  or  ethmoidal  lobide  (Fig.  424, 15),  which  arises  by  two  white-coloured  roots 
that  margin  the  extra- ventricular  nucleus  ;  the  external  root  (Fig.  424,  13)  is  con- 
tinuous with  the  convolution  that  is  prolonged  on  the  temporal  lobe  ;  the  internal 
root  (Fig.  424,  14),  which  is  shorter,  arises  from  the  inner  face  of  the  hemisphere, 
in  front  of  the  optic  commissm-e.  This  appendicular  lobule  is  directed  forwards, 
and  terminates  by  an  oval  expansion — the  optic  bulb  (Fig.  424,  16) — which 
extends  beyond  the  anterior  extremity  of  the  brain  to  be  lodged  in  the  ethmoid 
fossa.  The  olfactory  lobule  has  a  cavity  in  its  interior — a  diverticulum  of  the 
lateral  ventricle — and  is  received  into  a  depression  of  the  frontal  lobe,  named 
the  olfactory  fissure,  that  extends  to  the  summit  of  the  orbital  lobule,  and 
separates  two  convolutions,  the  internal  of  which  is  named  the  yyrus  rectus  (Fig. 

424,  21). 

The  external  face  of  the  frontal  lobe  shows  a  great  fissure  almost  parallel  with 
that  of  Rolando,  and  between  these  two  fissures  is  a  long  convolution  that  usually 
describes  three  curves  (Figs.  423,  6,  6  ;  433,  11,  11)  ;  this  limited  convolution 
takes  the  place  of  the  ascending  frontal  convolution  in  Man.  In  front,  it  is 
always  united  to  the  other  frontal  convolutions,  and  the  fusion  is  more  or  less 
apparent. 

On  the  same  face  is  perceived  another  great  fissure,  that  commences  in  the 
vicinity  of  the  crucial  fissure,  where  it  sometimes  appears  to  be  continuous  with 

»  In  the  domestic  animals,  the  occipital  lobe— already  so  difficult  to  circumscribe  in  Man — 
iB  not  more  distinct  in  his  neighbour.  The  posterior  extremity  of  the  hemispheres  is,  as  it  were, 
pushed  forward  by  the  internal  occipital  protuberance  and  the  cerebellum.  We  make  of  the 
posterior  region  of  the  hemisphere  a  parieto-occipital  lobe,  implying  by  this  term  the  fusion  of 
the  two  parietal  and  occipital  lobes.  The  latter  is  certainly  very  small,  but  we  cannot  admit 
its  disappearance.  We  do  not  find  in  the  brain  of  the  Horse,  the  lobule  of  the  insula  or  island 
of  Heil,  which  in  Man  is  concealed  at  the  bottom  of  the  fissure  of  Sylvius. 


THE  CEREBRUM. 


787 


that  of  Rolando  :  it  is  directed  forwards,  outwards,  and  downwards — that  is  to  say, 
it  turns  round  the  anterior  extremity  of  the  hemisphere  to  terminate  near  the 
fissure  of  Sylvius.  Within  this  fissure  is  a  triangular  convolution,  with  its 
summit  directed  backwards  ;  it  is  generally  divided  into  two  folds  at  its  inferior 
part — this  is  the  first  frontal  convolution  (Figs.  423,  9  ;  433,  15,  15). 

Another  convolution  is  included  between  this  fissure  and  that  which  margins 
the  ascending  frontal  convolution  ;  it  is  doubled  into  two  wide  flexuous  folds 
which  pass  into  the  latter  in  front,  and  represents  the  second  frontal  convolution 
(Figs.  423,  10,  10  ;  433,  14,  14). 


Fig.  433. 


BRAIN  OF  THE  HORSE  (LATERAL  FACE). 

■,  Medulla  oblongata;  Pr,  pons  Varolii ;  Pc,  cei-ebral  peduncle  (crus  cerebri).  1,  Middle  lobe  of  the 
cerebellum;  2,  lateral  lobe  of  ditto;  3,  medullary  root  of  the  spinal  accessory  nerve;  4,  internal 
roots  of  ditto  and  roots  of  the  pneuraogastric  ;  5,  transverse  fasciculus  of  the  medulla  oblongata, 
at  the  extremity  of  which  the  facial  nerve  appears  to  arise  ;  7,  fissure  of  Sylvius  ;  8,  8,  8, 
fissure  of  Rolando;  9,  posterior  branch  of  ditto;  10,  lobule  of  the  curved  plait;  11,  11,  11, 
limiting  frontal  convolution;  12,  12,  parieto-temporal  convolution  (analogous  to  the  ascending 
parietal  convolution);  13,  second  parieto-temporal  convolution;  14,  14,  the  two  principal  folds 
of  the  second  frontal  convolution;  15,  15,  folds  of  the  first  frontal  convolution;  17,  fiarieto- 
occipital  lobe;  18,  inferior  tempoi-al  convolution  (2nd  and  3rd  of  Man)  ;  19,  superior  temporal 
convolution  (1st  of  man);  20.  intra-ventricular  nucleus  of  the  corpus  striatum  ;  21,  external  root 
of  the  olfactory  lobule;  22,  olfactory  nerves. 


The  third  convohition  seen  in  Man  is  not  defined  in  the  Horse  by  an  impor- 
tant fissure,  and  if  it  exists  in  this  animal  it  is  probably  represented  by  the  origin 
of  the  inferior  fold  of  the  second  convolution,  which  is  sometimes  separated  from 
the  rest  by  a  shallow  sulcus. 

The  internal  face  of  the  frontal  lobe  shows  the  internal  part  of  the  first 
frontal  convolution,  and  a  portion  of  the  calloso-marginal  fissure  and  crested 
convolution. 

c.  Temporal  or  sphenoid(d  lobe. — Also  named  the  mastoid  lohde  by  Veterinary 
Anatomists,  the  temporal  lobe  in  Solipeds  is  a  large  pyrif  orm  eminence  occupying 


788  THE  CENTRAL  AXIS   OF  THE  NERVOUS  SYSTEM. 

the  posterior  part  of  the  inferior  face  of  the  hemisphere  (Figs.  423, 18, 19  ;  433, 
18,  19).  It  is  curved  on  itself,  the  convexity  being  outwards,  and  its  inner 
border  is  related  to  the  crus  cerebri.  It  concurs  in  forming  the  great  longi- 
tudinal fissure,  its  large  extremity  being  turned  forwards  and  margins  the  fissure 
of  Sylvius,  while  the  posterior  extremity  disappears  in  the  posterior  lobe  of  the 
hemisphere. 

The  surface  of  the  temporal  lobe  is  almost  smooth,  and  shows  scarcely  more 
than  one  slight  fissure,  parallel  to  the  posterior  branches  of  the  fissure  of  Sylvius 
(Fig.  433).  This  fissure  (the  parallel  fissure)  terminates  more  or  less  directly 
behind,  between  the  branches  of  a  ^  convolution — the  curved  j^lffit-  The 
external  branch  of  the  latter  is  continuous  with  the  superior  temporal  convolution 
(Fig.  433,  19),  which  is  comprised  between  the  parallel  fissure  and  the  fissure  of 
Sylvius.  The  part  situated  below  the  parallel  fissure  (Fig.  433,  18)  represents 
the  second  and  third  temporal  convolutions  of  Man.  The  temporal  lobe  is  very 
simple  in  Solipeds,  and  is  hollowed  internally  by  a  cul-de-sac  cavity  that  consti- 
tutes the  bottom  of  the  posterior  or  reflected  portion  of  the  lateral  ventricles. 

d.  Lobule  of  the  curved  plait. — Nearly  quadrilateral  in  shape  (Figs.  423,  13  ; 
433,  10),  this  lobule  is  included  between  the  fissure  of  Sylvius,  the  inferior  part 
of  the  fissure  of  Rolando,  and  the  interparietal  fissure.  It  is  formed  by  a  large 
convolution,  confounded  at  its  commencement  with  the  ascending  frontal  convo- 
lution, and  which  soon  divides  into  two  undulating  plaits  that  unite,  behind, 
with  the  superior  temporal  convolution,  the  curved  plait,  and  sometimes  with 
the  convolutions  of  the  parieto-occipital  lobe. 

e.  Parieto-occipital  lobe. — The  limits  of  the  occipital  lobe — so  difficult  to 
establish  in  the  human  brain — cannot  be  determined  in  that  of  the  Horse  ;  for 
this  reason  it  is  that  we  now  describe  a  parieto-occipital  lobe  resulting  from  the 
fusion  of  the  parietal  with  the  occipital  lobe. 

This  lobe  offers  three  faces.  The  external  face  is  almost  entirely  occupied 
by  a  large  convolution — the  parieto-temporal — formed  by  two  folds,  the  outer  of 
which  (Figs.  323,  7,  7  ;  433,  12,  12)  margins  the  interparietal  fissure  and  the 
anterior  part  of  the  fissure  of  Rolando  ;  in  front,  it  is  continuous  with  the  plait 
that  surrounds  the  crucial  fissure  and — through  the  medium  of  the  latter — the 
first  frontal  convolution  ;  behind,  it  is  inflected  downwards  to  be  continued  on 
the  posterior  face  of  the  lobe. 

The  internal  face  shows  the  parieto-occipital  portion  of  the  corpus  callosum 
convolution,  and  of  the  second  parieto-occipital  convolution  ;  these  two  being 
separated  by  the  calloso-marginal  fissure,  from  which  is  detached  a  branch  that 
rides  on  the  superior  border  of  the  hemisphere  and  forms  the  crucial  fissure. 

The  second  parieto-occipital  convolution  (Figs.  423,  8,  8  ;  433,  13)  has  the 
form  of  a  wedge,  the  summit  of  which  is  directed  forward ;  here  it  is  single, 
and  is  confounded  with  the  first  convolution  of  the  same  lobe,  and  with  the 
plait  that  surrounds  the  crucial  fissure  ;  but  it  afterwards  divides  into  two 
principal,  almost  straight  plaits,  which  are  continued  on  the  posterior  face  of  the 
lobe. 

The  latter  is  occupied  by  the  posterior  extremity  of  the  parieto-occipital 
convolutions.  It  is  oblique  downwards  and  forwards,  and  is  separated  from  the 
cerebellum  by  the  transverse  duplicature  of  the  dura  mater.  On  this  face  are 
seen  three  or  four  undulating  plaits  which  join  each  other,  and  pass  on  to  the 
convolutions  of  the  hippocampus. 


TEE  CEREBHUM. 


Inteenal  Conformation  of  the  Brain. 

In  separating  the  cerebral  hemispheres  by  their  upper  face,  we  discover  the 
great  commissure  known  as  the  corpus  callosum — the  first  object  that  presents 
itself  for  study  in  the  internal  conformation  of  the  brain. 

If  we  afterwards  remove,  with  a  sharp  instrument,  and  by  a  horizontal 
section,  all  that  portion  of  the  hemispheres  which  covers  this  commissure,  and 
also  if  the  latter  be  excised  to  a  certain  extent  to  the  right  and  left  of  the  middle 
line,  we  shall  penetrate  two  symmetrically  disposed  cavities  in  the  centre  of  each 
hemisphere.     These  cavities  are  the  lateral  or  cerebral  ventricles. 

They  are  separated  on  the  middle  plane  by  a  thin  partition — the  septum 
lucidum — which  is  attached  to  the  corpus  callosum  by  its  upper  border,  and 
fixed  by  its  inferior  border  into  the  fornix^  a  kind  of  middle  arch,  beneath  which 
is  the  foramen  of  Monro,  or  orifice  communicating  with  the  two  ventricles.  On 
the  floor  of  these  cavities  is  observed  two  large  eminences— the  corpus  striatum 


Fig.  434. 


Fig.  435. 


THE  CORPUS  CALLOSUM  OF  THE  HORSE,  AFTER 
REMOVAL  OP  THE  UPPER  POKTIOM  OP  THE 
CEREBRAL   HEMISPHERES. 

I,  Centrum  ovale  of  Vicq-d'Azyr ;  2,  2,  trans- 
verse fibres  of  the  corpus  callosum  ;  3,  3, 
tractus  longitudinales;  4,4,  cornua,  or  angles 
of  the  posterior  extremity  ;  5,  5,  ditto  of 
anterior  extremity. 


ANTERIOR  PORTION  OF  THE  LATERAL  VENTRI- 
CLES OF  THE  DOG,  EXPOSED  BY  REMOVAL  OF 
THE    ROOF. 

1,  Corpus  callosum;  2,  anterior  part  of  the 
corpus  callosum,  turned  forward  after  de- 
stroying the  septum  lucidum,  to  show  the 
fornix,  3,  3 ;  4,  4,  hippocampi ;  5,  5,  taeniae 
semicircularis ;  6,  6,  choroid  plexus ;  7,  7, 
corpora  striata. 


and  the  hippocampus ;  with  a  vascular  and  apparently  granular  cord  forming  the 
cerebral  choroid  plexus — a  dependency  of  the  velum  interpositum. 

It  now  remains  to  enter  into  some  detail  with  regard  to  the  anatomical 
characteristics  of  all  these  parts. 

1.  The  Corpus  Callosum  (Figs.  434,  435). 

The  corpus  callosum  is  a  kind  of  arch  thrown  over  the  two  lateral  ventricles, 
while  at  the  same  time  it  is  a  commissure  uniting  the  two  hemispheres.  It 
belongs  exclusively  to  Mammalia. 

Composed  entirely  of  white  substance,  this  arch  is  of  an  elongated,  quadri- 
lateral sliape,  being  elongated  in  an  antero-posterior  direction ;  it  thus  presents 
for  study  two  faces,  two  boi-ders,  and  two  extremities. 


790  THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 

The  superior  face,  free  in  the  middle,  and  corresponding  to  the  bottom  of  the 
interlobular  fissure,  is  covered  right  and  left  by  the  substance  of  the  hemispheres. 
It  is  traversed  from  before  to  behind  by  two  white,  and  generally  very  delicate, 
cords— the  tradus  longitudinalis  (the  chonlm  lonyitudinalis  of  Lancisi)  of  the 
corpus  callosum — which  lie  together  on  the  middle  line.  The  inferior  face  is 
divided — by  the  insertion  of  the  septum  lucidum — into  two  lateral  portions,  each 
of  which  forms  the  roof  of  one  of  the  cerebral  ventricles.  Behind,  it  rests  on 
the  middle  part  of  the  fornix. 

The  two  lateral  borders  of  the  corpus  callosum  disappear  in  the  central  sub- 
stance of  the  hemispheres,  where  it  is  almost  impossible  to  distinguish  their 
limits. 

The  posterior  extremity  appears  at  the  bottom  of  the  interlobular  fissure — 
after  destroying  the  adhesion  usually  established  above  it  between  the  two  hemi- 
spheres— in  the  form  of  a  thick,  rounded  enlargement  {splenium)  doubled  below, 
and  confounded  with  the  middle  part  of  the  fornix.  It  is  prolonged,  laterally, 
above  the  ventricular  cavities,  in  forming  two  angles  {linece  transversm)  which 
are  soon  lost  in  the  white  central  substance  of  the  cerebrum. 

The  anterior  extremity  comports  itself  in  a  similar  manner  between  the 
anterior  lobes  of  the  hemispheres.  It  is  named  the  genu  of  tJie  corpus  callosum, 
and  is  doubled  more  abruptly  than  the  posterior  end,  terminating  by  a  thin 
narrow  portion — the  rostrum. 

2.  The  Lateral  or  Cerebral  Ventricles  (Figs.  429,  435). 

The  lateral  veyitricles  are  two  large  elongated  cavities  excavated  in  the  hemi- 
spheres, lying  against  each  other  in  their  anterior  moiety,  and  divergent  in  their 
posterior  part,  which  is  very  much  curved  backwards,  outwards,  and  downwards, 
to  open  into  the  substance  of  the  sphenoidal  lobe. 

This  disposition  permits  the  division  of  the  cerebral  ventricles  into  two 
regions — an  anterior,  and  a  posterior  or  reflected. 

The  anterior  region — anterior  cornu,  or  frontal  diverticulum — is  separated  in 
the  median  plane  from  the  opposite  ventricle,  by  the  septum  lucidum  and  the 
summit  of  the  fornix,  beneath  which  is  the  foramen  of  Monro  establishing  a 
communication  between  the  middle  and  the  two  lateral  ventricles,  and  between 
these  latter.  Above,  it  offers  a  smooth  wall  formed  by  the  corpus  callosum. 
Below,  on  its  floor,  there  is  first  remarked,  in  front,  the  corpus  striatum  ;  behind, 
the  internal  portion  of  the  hippocampus  ;  in  the  middle,  an  oblique  groove 
running  backwards  and  inwards,  at  the  bottom  of  which  floats  the  choroid 
plexus.  The  anterior  extremity  of  this  region,  occupied  by  the  base  of  the 
corpus  striatum,  is  continued  by  a  narrow  opening  into  the  interior  of  the 
olfactory  lobe.  The  posterior  is  prolonged,  without  any  Hne  of  demarcation,  by 
the  reflected  portion  of  the  ventricular  cavity. 

The  latter  region  (posterior  or  descending  cornu,  or  sphenoidal  diverticulum) 
occupies  the  most  declivitous  portion  of  the  posterior  lobe  of  the  hemisphere, 
and  is  a  much-curved  canal  with  its  concavity  forward  ;  this  canal  terminates 
in  a  cul-de-sac  in  the  substance  of  the  sphenoidal  lobe.  On  the  floor  of  this 
canal  is  marked  the  posterior  portion  of  the  hippocampus  and  the  choroid  plexus. 

A  very  fine  membrane — the  ventricular  arachyioid — plays  the  part  of  a  serous 
membrane  and  covers  the  walls  of  these  cavities,  being  spread  everywhere  over  a 
layer  of  white  substance,  prolonged  into  the  ethmoidal  diverticulum,  and  con- 
tinuous, through  the  foramen  of  Monro,  with  that  of  the  middle  ventricle.    This 


TEE  CEREBRUM.  791 

membrane  secretes  a  limpid  and  transparent  fluid,  analogous  to  the  cerebro- 
spinal fluid,  though  in  health  it  is  always  in  small  quantity. 

3.  The  Septum  Lucidum  (Fig.  429,  24). 

This  appellation  is  given  to  a  thin  middle  band,  standing  vertically  between 
the  two  lateral  ventricles,  elongated  from  before  to  behind,  widened  considerably 
at  its  anterior  extremity,  terminating  in  a  point  at  its  posterior  extremity,  and 
inserted  above  into  the  corpus  callosum,  below  into  the  back  of  the  fornix. 

On  the  faces  of  this  partition,  which  is  formed  of  white  substance,  is  spread 
the  proper  membrane  of  the  lateral  ventricles.  In  the  human  species,  a  narrow 
ventricle  has  been  described  as  found  in  its  substance  ;  but  this  does  not  appear 
to  exist  in  the  domesticated  animals. 

4.  The  Fornix,  or  Trigonum  (Fig.  435,  3). 

Also  named  the  vault  of  three  or  four  pillars,  the  fornix  {arch)  is  a  single 
middle  body  in  the  interior  of  the  brain,  concurring  to  separate  the  two  ven- 
tricles, and  serving  to  support  the  septum  lucidum.  It  is  depressed  below  and 
above,  and  is  of  a  triangular  form  ;  its  apex,  looking  downward,  stands  in  the 
median  plane  above  the  foramen  of  Monro  and  the  thalami  optici,  though  sepa- 
rated from  the  latter  by  the  velum  interpositum  and  the  hippocampi,  and 
receives  on  its  upper  face  the  insertion  of  the  septum  lucidum.  Behind,  at  its 
base,  and  in  the  middle  line,  the  fornix  is  confounded  with  the  corpus  callosum, 
which  it  supports  ;  it  is  prolonged  on  each  side  by  a  lamina  extending  to  the 
surface  of  the  hippocampus,  forming  the  cortical  layer  of  this  deep  convolution 
of  the  brain,  and  with  its  congener  constituting  the  posterior  pillars  ( posterior 
crura,  tmnice  hippocampi,  or  corpora  fimhriata)  of  the  fornix.  These  two  pillars 
are  united  by  some  white  transverse  fibres,  which  form  what  has  been  named 
the  lyre. 

In  front,  at  its  apex,  the  fornix  is  also  attached  to  the  corpus  callosum,  and 
divides  into  two  cords  or  anterior  pillars  {crura) — (Figs.  425  ;  429,  17),  which 
pass  in  front  of  the  anterior  cerebral  commissure,  are  inflected  downwards  and 
backwards,  in  traversing  the  optic  thalamus,  on  the  sides  of  the  middle  ventricle, 
and  finally  have  their  extremities  confounded  with  the  mammillary  process 
{corpus  albicans). 

These  two  crura  limit,  in  front,  the  foramen  commune  anterius,  or  foramen  of 
Monro  (Fig.  425,  16),  over  which  the  apex  of  the  fornix  is  thrown  across  like  an 
arch  (Fig.  425). 

The  fornix  is  white  throughout  its  whole  extent,  with  a  greyish  tint  towards 
its  summit. 

5.  The  Hippocampi  (Fig.  435,  4). 

The  hippocampus,  or  cornu  Ammonis  (from  its  resemblance  to  a  ram's  horn, 
the  crest  of  Jupiter  Ammon),  is  an  elongated  projection,  a  veritable  internal 
convolution  of  the  brain  (is,  in  fact,  the  internal  sm-f ace  of  the  ffi/rus  fornicatus, 
or  convolution  lying  upon  the  corpus  callosum,  and  which  terminates  at  the 
fissure  of  Sylvius).  It  occupies  the  floor  of  the  anterior  part  of  the  lateral 
ventricle,  and  is  prolonged  throughout  its  reflected  portion,  the  curvature  of 
which  it  exactly  follows.  Considered  together,  the  two  hippocampi  somewhat 
closely  resemble  the  uterine  cornua  of  the  Cow. 

By  their  internal  extremity,  they  are  in  contact  with  each  other  beneath  the 
middle  portion  of  the  fornix,  and  above  the  optic  thalamus,  which  is  separated  from 


792  TBE  CENTRAL  AXTS   OF  THE  NERVOUS  SYSTEM. 

them  by  the  velum  interpositum  (Fig.  429,  9).  Their  external  extremity  occupies, 
in  the  sphenoidal  lobe,  the  cul-de-sac  of  the  reflected  portion  of  the  lateral  ventricle. 

The  central  mass  of  this  projection  is  formed  of  a  nucleus  of  grey  substance, 
covered  on  both  faces  by  a  layer  of  white  substance.  The  layer  that  covers  its 
inferior  face  is  named  the  subicidum,  and  that  which  extends  over  its  surface  is 
designated  the  alreiis ;  it  is  a  kind  of  prolongation  of  the  posterior  pillars  of  the 
fornix. 

Towards  the  concave  border  of  the  hippocampus,  this  white  layer  offers  a 
kind  of  wide  hem,  beneath  which  the  choroid  plexus  passes  ;  this  hem  constitutes 
a  small  curved  band,  like  the  cornu  Ammonis,  wider  in  its  middle  part  than  at 
its  extremities,  and  is  named  the  corpus  fimbriatum,  or  tcBnia  hippocampus. 

The  grey  layer  comprised  between  the  two  white  bands  also  makes  a  slight 
projection  at  the  inner  border  of  the  hippocampus,  and  forms  the  fascui  dentata} 

6.  The  Corpora  Striata  (Fig.  435,  7). 

The  corpus  striatum  is  a  mass  of  grey  matter  interposed  on  the  course  of  the 
crura  cerebri.  It  includes  the  entire  thickness  of  the  floor  of  the  lateral  ventricle, 
and  projects  outwards,  on  the  lower  face  of  the  hemisphere,  between  the  two 
roots  of  the  olfactory  lobule. 

The  corpus  striatum  owes  its  name  to  its  structure  :  the  thick  nucleus  of 
grey  matter  composing  it  is,  in  fact,  traversed  by  white  fibres  from  the  crura 
cerebri,  which  pass  into  the  hemispheres  ;  these  fibres  appear  at  several  points 
in  the  form  of  sharply  defined  white  strias. 

It  is  divided  into  two  portions  by  these  fibres,  which  collectively  constitute 
the  internal  capsule  (Fig.  436,  Ci).  The  external  portion  is  the  extra-ventricular 
niccleus  of  the  corpus  striatum,  so  named  because  of  its  position,  and  lenticular 
nucleus,  in  consequence  of  its  shape ;  just  as  the  internal  portion  is  most 
frequently  designated  the  intra-ventricular  nucleus  of  the  corpus  striatum,  or 
caudate  nucleus  (Fig.  436).  The  caudate  or  intra-ventricular  nucleus  occupies  the 
anterior  region  of  the  lateral  ventricle  (Fig.  435,  7) 

This  eminence  is  pyriform  in  shape,  and  obHquely  elongated  forward  and 
inward.  Its  surface  is  smooth,  and  regularly  convex.  Its  base,  or  anterior 
extremity,  corresponds  to  the  anterior  cid-de-sac  of  the  ventricle.  The  simamit, 
or  posterior  extremity,  disappears  at  the  commencement  of  the  reflected  portion 
of  the  ventricular  cavity.  Outwardly,  the  corpus  striatum  is  limited  by  a  groove 
that  forms  the  angle  of  union  between  the  floor  and  roof  of  the  ventricle. 
Inwardly,  it  is  separated  from  the  optic  thalamus  and  cornu  Ammonis  by  another 
groove,  in  which  the  choroid  plexus  floats,  and  which  is  oblique  inwards  and 
forwards,  and  shows  at  the  bottom  the  tcenia  semicircularis  (Fig.  432,  13).  This 
is  a  flattened  white  cord,  which  disappears  inwardly  towards  the  foramen  of 
Monro,  and  bends  outwards  along  the  optic  nerve  to  within  about  |  of  an  inch 
from  the  optic  commissure  ;  in  this  way  it  forms  a  kind  of  circular  band  around 
the  anterior  extremity  of  the  isthmus,  beneath  which  all  the  fibres  of  the  latter 
pass  to  reach  the  cerebral  hemispheres. 

7.  The  Velum  Interpositum  and  Choroid  Plexus  (Fig.  435,  6). 
The   velum   interpositum   (velum   vasculosum,   tela  choroidea)   is   a   vascular 
expansion  derived  from  the  pia  mater,  which  penetrates  the  brain  by  the  great 

'  Sabatier,  taking  comparative  anatomy  and  embryology  as  his  guide,  regarded  the  hem  of 
the  hippocampus  as  a  ganglion  spread  along  the  origin  of  tlie  optic  nerve. 


THE  CEREBRUM. 


793 


transverse  fissure,  and  insinuates  itself  between  the  thalamus  opticus  and  the 
convolution  of  the  cornu  Ammonis.  The  velum,  on  arriving  beneath  the  taenia 
hippocampus,  terminates  in  the  choroid  plexus — a  red,  granular-looking  cord, 
which  is  suspended  by  its  antero-external  border,  and  projects  into  the  interior  of 
the  lateral  ventricle. 

The  choroid  plexuses  of  the  brain  (plexus  choroidece)  extend  from  the  anterior 
extremity  of  the  corpus  striatum  to  the  bottom  of  the  cul-de-sac,  or  sphenoidal 
diverticulum.  In  the  anterior  part  of  the  ventricle,  they  occupy  the  oblique  fissure 
which  traverses  that  part,  to  the  inner  side  of  the  caudate  nucleus.  In  the  posterior 
region,  they  float  in  front  of  the  cornu  Ammonis.  Their  anterior  or  internal 
extremity,  more  voluminous  than  the  external,  always  forms  a  small  appendage 

Fig.  436. 


1         i 

CA        L 
DIAGRAM   OF   A   TRANSVERSE   SECTION   OF   THE   HUMAN    BRAIN   AT   THE   MIDDLE    PART   OP 
THE   CORPUS  STRIATUM. 

CO,  Corpus  callosum ;  CA,  intra-ventricular  (or  caudate)  nucleus  of  the  corpus  striatum  ;  L,  extra- 
ventricular,  or  lenticular  nucleus  of  the  corpus  striatum  ;  ci,  ci,  internal  capsules  placed  between 
these  two  nuclei. 

which  remains  quite  free.  They  are  united  to  each  other,  near  this  extremity, 
by  an  intermediate  cord,  which  goes  through  the  foramen  of  Monro  in  passing 
l)eneath  the  fornix. 

Like  the  velum  interpositum,  the  choroid  plexuses  are  formed  by  a  network 
of  arteries  and  veins.  They  are  often  incrusted  in  calcareous  matter,  and  may 
be  the  seat  of  more  or  less  voluminous  cysts. 

The  veins  proceeding  from  this  vascular  apparatus  are  very  voluminous,  and 
by  their  union  form  the  great  vena  Galeni,  which  bends  round  the  splenium  of 
the  corpus  callosum  to  reach  the  interlobular  fissure,  and  proceeds  to  the  sinus 
of  the  falx  cerebri. 

The  Steucture  of  the  Brain. 

The  structure  of  the  brain  is  certainly  one  of  the  most  interesting  points  in 


7M 


THE   CENTRAL   AXIS   OF  TEE  NERVOUS  SYSTEM. 


the  study  of  the  nerve-centres  ;  for  on  a  perfect  knowledge  of  it  depends  the 
sokition  of  the  most  difficult  problems  in  the  physiology  of  the  nervous  system. 
Numerous  attempts  have  been  made  to  elucidate  its  intimate  organization  ;  but 
we  must  here  omit  the  multitude  of  secondary  details  revealed  by  these  researches, 
and  limit  ourselves  to  the  essential  and  fundamental  facts. 

The  tu'o  nerve-suhstances  enter  into  the  texture  of  the  cerebral  hemispheres, 
and  both  are  exactly  disposed  as  in  the  cerebellum. 

The  grey  substance  extends  over  the  entire  external  surface  of  the  brain,  and 
is  prolonged  into  the  plaits — thereby  augmenting  the  extent  of  that  surface,  and 
so  forming  the  cortical  layer  of  the  cerebral  convolutions.  Gratiolet  has  compared 
this  layer  to  a  ring-purse  opening  on  the  internal  face  of  the  hemisphere,  having 
for  its  rings  the  convolutions  of  the  hippocampus  and  corpus  callosum,  in  which 
is  included  the  white  medullary  substance. 

The  grey  matter  projects  into  the  lower  face  of  the  olfactory  lobes  and 


Fig  437 


COURSE  OF  ONE  PORTION  OF  THE  ASSOCIATION    NERVE-FIBRES  IN  A  HEMISPHERE.     (DIAGRAMMATIC.) 


interior  of  the  hemispheres,  where  it  forms  the  central  ganglia  known  as  the 
claustrum,  lenticular  nucleus,  and  caudate  nucleus. 

In  order  to  study  the  distribution  of  the  central  grey  masses,  horizontal  and 
vertical  sections  must  be  made  of  the  brain,  through  the  corpora  striata.  In 
a  vertical  section  by  the  optic  commissure  (Fig.  436),  will  be  seen  the  caudate 
nucleus  limiting  outwardly  the  lateral  ventricle,  and  separated  from  the  lenticular 
nucleus  by  a  layer  of  white  substance — the  internal  capsule;  between  the 
lenticular  nucleus  and  the  cerebral  cortex  there  is  a  certain  amount  of  white 
matter.  If  the  section  is  made  a  little  more  behind,  there  will  be  observed, 
between  the  grey  matter  and  tlie  lenticular  nucleus,  a  small  greyish  band  named 
the  claustrum  ;  this  is  separated  from  the  lenticular  nucleus  by  the  external  capsule. 

To  sum  up,  it  is  easy  to  perceive  that  the  distribution  of  the  central  grey 
masses  Qenticulo-striated  bodies)  is  subordinate  to  the  internal  capsule.  Otherwise, 
this  plays  a  considerable  part  in  the  physiology  of  the  hemispheres. 


THE  CEREBRUM. 


795 


In  the  middle  of  each  hemisphere,  the  white  substance  constitutes  a  consider- 
able nucleus,  which,  from  its  form,  is  named  the  centrum  ovale  (Vicq-d'Azyr) 
(Fig.  427,  1  ;  434,  1),  and  which  is  united  to  that  of  the  opposite  side  by  the 
great  cerebral  commissure,  or  corpus  callosum,  sending  a  prolongation  into  each 
convolution  ;  thus  exhibiting  the  exact  disposition  of  the  lateral  white  masses  of 
the  cerebellum,  with  which  the  nuclei  of  the  hemispheres  have  also  another  point 
of  resemblance,  in  that  they  are  attached  to  the  cerebral  peduncles,  as  the  first 
are  to  the  cerebellar.  But  the  latter  peculiarity  is  less  evident  than  the  others — 
which  are  at  once  obvious  in  horizontal  and  transverse  sections  of  the  brain — 
and  can  only  be  clearly  demonstrated  by  the  manipulations  necessary  to  unravel 
the  intimate  texture  of  the  white  substance. 

In  studying  this  texture  in  brains  hardened  by  nitric  acid,  washed  in  pure 
water,  and  exposed  to  dry  air  for  a  day  or  two,  we  perceive  that  the  white 
cerebral  substance  is  entirely  composed  of  fine  fibrous  lamellae,  diverging  in  every 


Fig.  438. 


Fi£r.  439. 


DIAGRAM  OF  THE  COURSE  OF  THE  ASSOCIATION 
NERVE-FIBRES  OF  THE  CORPUS  CALLOSUM  AND 
OF  THE  ANTERIOR  COMMISSURE. 


DIAGRAM  OF  THE  COURSE  OF  THE  RADIAT- 
ING NERVE-FIBRES  OF  THE  CORONA 
RADIATA,  AND  THE  RELATIONS  OF  THE 
CORPORA  STRIATA  WITH  THE  CORTICAL 
GREY   SUBSTANCE. 


direction,  corresponding  by  their  concentric  extremity  to  the  centre  of  the 
hemisphere,  and  abutting,  by  their  peripheral  extremity,  on  the  inner  face  of  the 
grey  covering  of  the  convolutions. 

With  regard  to  the  relations  between  the  centrum  ovale  and  the  cerebral 
isthmus,  and  those  the  fibres  of  the  former  have  with  the  other  parts  of  the  brain, 
it  is  found  that  the  fibres  of  the  lower  stage  of  the  peduncles  attach  the 
isthmus  to  the  cerebral  hemispheres,  in  passing  through  the  corpora  striata,  and 
radiate  in  the  centrum  ovale.  Here  these  fibres  form  a  kind  of  fan — the  radiant 
crown  {corona  radiata)  of  Reil.  The  internal  capsule  is  the  point  of  departure 
of  these  fibres,  and  is  therefore  designated  t\iQfoot  {pes)  of  the  radiant  croivn. 

In  the  centrum  ovale,  the  nerve-fibres  form  two  great  apparatuses — an 
apparatus  of  association  and  an  apparatus  of  radiation  (Pitres). 

The  first  comprises  a  system  of  intra-hemisphere  commissures,  and  a  system  of 
inter-hemisphere  commissures. 

The  fibres  of  the  first  system  unite  the  neighbouring  convolutions,  and  those 
more  or  less  distant  from  each  other. 


796 


THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 


The  second  system  comprises  the  fibres  of  the  corpus  callosum.  It  was 
formerly  believed  that  these  fibres  arose  from  the  cerebral  peduncles,  but  now  it 
is  thought  they  pass  merely  from  one  hemisphere  to  another.  The  anterior  com- 
missure belongs  also  to  this  system ;  but  great  uncertainty  exists  as  to  the 
connections  of  its  fibres. 

The  radiation  apparatus  is  formed  by  the  fibres  of  the  corona  radiata.  Among 
them  a  great  number  should  proceed,  according  to  Meynert,  to  the  caudate 
nucleus,  the  lenticular  nucleus,  and  the  optic  thalamus  {cortico-striated,  cortico- 
lenticular,  and  cortico-optic  fihres).  The  others  form  two  direct  peduncular 
fasciculi — one,  occupying  the  anterior  two-thirds  of  the  corona  radiata,  going 
from  the  motor  convolutions  of  the  cortex  to  the  infero-lateral  fasciculi  of  the 


Fig.  440. 


Fig.  441. 


ARRANGEMENT  OF    THE    LAYERS   AND  CELIiS 
OP   A    FRONTAL   CONVOLUTION. 

1,  Hyaline  layer;  2,  layer  of  the  small 
pyritmid  cells ;  3,  thick  layer  of  the  great 
pyramid  cells ;  4,  granular  layer  ;  5,  6, 
layer  of  so-called  volition  cells  (beneath 
this  layer  is  the  white  fibrillated 
substance). 


CORTICAL  SUBSTANCE 
OF  THE  CEREBRAL 
HEMISPHERES. 

a,  Medullary  .sub 
stance ;  b,  reddish 
grey  layer ;  c,  clear 
white  streak,  com- 
posed of  horizontal 
fibres;  d,  grey  layer; 
e,  external  white 
layer. 


spinal  cord ;  the  other  occupies  the  posterior  part  of  the  corona  radiata,  and 
passes  from  the  lateral  and  posterior  convolutions  of  the  hemisphere  to  disappear 
in  the  cerebral  peduncle.     This  fasciculus  is  sensitive. 

The  white  substance  of  the  brain  is  formed  of  very  fine  nerve-fibres.  The 
grey  substance  of  the  cortex  is  made  up  of  five  or  six  superposed  layers.  In  the 
frontal  region  there  are  six  layers,  as  follows  :  1.  A  granular  layer,  with  very 
small  stellate  cells.  2.  A  stratum  containing  numerous  small  pyramidal  cells. 
3.  A  very  thick  layer  with  large  cells — great  pyramidal,  or  giant  cells.  4.  A 
granular  layer  formed  of  numerous  small  and  uniform  cellular  elements.  5  and 
6.  Two  layers  having  for  their  principal  elements  stellate  or  fusiform  cell^ 
{volition  cells). 

In  the  occipital  region,  the  third  layer  is  absent ;  but  in  the  cornu  Ammonia 
it  is  very  developed.  Lastly,  the  giant  pyramid  cells  are  more  particularly  found 
in  the  cortical  regions  in  the  vicinity  of  the  crucial  fissure. 


THE  CEREBRUM. 


797 


The  grey  substance  forming  the  corpora  striata  has,  for  its  essential  elements, 
cells  analogous  to  the  medium  cells  of  the  cerebral  cortex. 

Vessels. — The  arteries  of  the  brain  come  from  the  three  cerebral  arteries  (see 
the  internal  carotid).  The  branches  of  these  vessels  form  two  systems  which 
have  a  common  origin,  but  which  remain  distinct  at  the  periphery.     The  cortical 

Fig.  442. 


BRAIN   OF   THE   OX  (UPPER   FACE).      THREE-FOURTHS   NATURAL   SIZE. 

,  Neck  of  the  medulla  oblongata;  Pj,  posterior  pyramid  of  the  medulla  oblongata;  S,  inter-hemi- 
spherical fissure.  1,  Middle  lobe  of  the  cerebellum;  2,  2,  lateral  lobes  of  the  cerebellum;  4,4, 
anterior  part  of  the  fissure  of  Rolando  interrupted  by  an  annectent  gyrus  uniting  convolutions  9 
and  6  ;  4',  inferior  part  of  ditto  ;  4",  posterior  branch  ot  ditto  ;  5,  second  parietal  convolution  with  its 
plaits ,  6,  first  parietal  convolution  with  its  plaits  ;  7,  7,  crucial  fissure  (the  sigmoid  gyrus  surround- 
ing it  is  hidden  beneath  the  before-mentioned  plait);  8,  first  frontal  convolution;  9,  union  of  the 
second  frontal  with  the  limited  frontal  convolution ;  10,  limiting  front  convolution ;  11,  lobule  of 
the  curved  plait. 


si/stem  furnishes  blood  to  the  pia  mater  and  the  grey  cortex.  The  central  system 
leaves  the  circle  of  Willis,  and  is  distributed  to  the  ganglionic  centres.  The 
arterioles  of  this  system  form  groups  which  are  generally  independent  of 
each  other  (Duret). 

The  venous  blood  from  the  centre  of  the  hemispheres  issues  by  the  vena 
53 


798 


THE  CENTRAL   AXIS   OF  THE  NERVOUS  SYSTEM. 


Galeni.     On  the  surface  of  the  hemispheres  are  large  veins  which  enter  the 
sinuses  of  the  dura  mater. 

The  lymphatics  form  sheaths  around  the  small  blood-vessels. 

Development. — See  "  Embryology,"  for  the  development  of  the  brain. 


Differential  Characters  in  the  Brain  of  the  other  Animals. 

In  the  animals  which  interest  us,  the  brain  presents  differences  with  regard 

to  volume,  as  might  be  sur- 
mised from  what  has  been  stated 
in  our  general  remarks,  when 
dealing  with  the  cerebrum  and 
cerebellum ;  in  the  arrange- 
ment of  the  convolutions  there 
are  also  important  differences. 

Ruminants  (Figs.  442, 
443). — In  these  creatures,  the 
brain  is  more  globular  than  in 
Solipeds.  The  hemispheres  are 
wider  behind  than  in  the  Horse 
and  Ass,  but  they  are  narrower 
in  the  frontal  region ;  there  they 
are  a  little  flattened  on  each  side, 
and  curved  downwards.  The 
fissure  of  Sylvius  is  deeper  at 
its  commencement ;  its  middle 
branch,  much  more  developed, 
ascends  to  near  the  upper  face 
of  the  hemisphere  ;  at  the 
bottom  of  the  latter  is  a  V- 
shaped  plait,  which  unites  the 
ascending  frontal  convolution 
to  the  second  frontal  convolu- 
tion. This  plait  is  concealed  in 
Solipeds. 

The  large  fissures  are  dis- 
posed nearly  as  in  the  Horse ; 
but  it  should  be  noted  that  the 
fissure  of  Rolando  is  interrupted, 
near  its  origin,  by  an  annectent 
gyrus  which  is  thrown  from 
the  curved  plait  on  to  the  as- 
cending frontal  convolution, 
and,  in  front,  by  another  plait 
that  unites  the  first  parietal 
convolution  to  the  limited  fron- 
tal convolution. 

The  sigmoid  gyi'us,  or  its 
analogue,  is  concealed  between 
the  passage  plait  that  joins  the  parietal  to  the  frontal  convolutions. 

In  the  Sheepy  the  convolutions  and  the  sulci  on  the  surface  of  the  brain  are 


brain  of  the  sheep  (upper  face),     natural  size. 

B,  Medulla  oblongata  :  1,  posterior  pyramiil  of  ditto.  Ce, 
Cerebellum:  2,  2,  lateral  lobes  of  ditto;  3,  middle  lobe 
of  ditto.  C,  Right  hemisphere  of  the  brain.  12,  Inter- 
hemispherical  fissure  ;  13,  13,  upper  end  of  the  fissure 
of  Sylvius;  14,  14,  fissure  of  Rolando;  15,  15,  postero- 
inferior  branch  of  ditto  ;  16,  16,  posterior  branch  of 
ditto ;  4,  external  parietal  convolution ;  5,  internal 
parietal  convolution;  6,  lobule  of  the  curved  plait;  7, 
annectent  gyrus  uniting  the  frontal  lobe  to  the  lobule 
of  the  curved  plait,  above  the  fissure  of  Sylvius ;  8, 
second  frontal  convolution  ;  9,  first  frontal  convolution  ; 
10,  annectent  gyrus  uniting  the  first  frontal  convolution 
to  the  second  parietal  convolution  ;  17, 17,  crucial  fissure. 
G,  G,  Sigmoid  gyrus. 


TEE  CEBEBRUM. 


799 


arranged  in  exactly  the  same  manner  as  in  the  Ox,  as  may  be  seen  in  comparing 
Figs.  442  and  443. 

Pig. — The  cerebellum  is  flattened  before  and  behind,  against  the  base  of  the 
brain.  The  latter  is  much  more  elongated  than  in  Ruminants.  The  convolutions 
are  much  more  simple  and  less  undulating  than  in  the  brain  of  the  Ox  and  Sheep, 
and  in  this  respect  they  establish  a  kind  of  transition  between  Kuminants  and 
the  Carnivora.     In  front  of  the 

crucial  fissure   there  is  a  deep  ^'8-  *"**• 

incision  on  the  upper  border  of 
the  hemisphere,  and  which  is 
continued  by  a  fissure  between 
the  two  frontal  convolutions  to 
the  anterior  extremity  of  the 
brain  (Fig.  444). 

The  gyri  fissures  —  those 
which  separate  the  convolutions 
of  each  lobe — are  larger  than  in 
the  Horse. 

T\iQ  convolutions  of  the  frontal 
lobe  are  here  also  three  in  num- 
ber. The  ascending  frontal  and 
first  frontal  show  scarcely  any 
differences.  On  the  contrary, 
however,  the  second  frontal 
passes  almost  directly  backwards, 
instead  of  being  oblique  up- 
wards and  forwards,  as  in  Soli- 
peds.  Simple  in  front,  it  bifur- 
cates behind,  and  its  two  branches 
pass  into  the  ascending  frontal 
convolution. 

There  is  nothing  worthy  of 
remark  with  regard  to  the  tem- 
poral lobe,  nor  to  the  lobule  of 
the  curved  plait. 

The  first  par  ieto-occipital  con- 
volution is  less  distinctly  divided 
into  two  plaits  than  in  the 
Horse  ;  it  joins,  in  front,  the 
first  frontal  and  the  ascending 
frontal  convolution.  The  second 
offers  nothing  in  particular. 

Dog. — The  hemispheres  are  much  more  elongated  than  in  the  preceding 
species,  except  in  the  Bulldog  ;  the  convolutions  are  very  slightly  flexuous.  At 
first  sight,  it  is  difficult  to  find  on  the  brain  of  the  Dog  the  sulci  and  lobes  dis- 
tinguished in  Solipeds  ;  but  an  attentive  examination  allows  it  to  be  approximated 
to  the  brains  of  these  animals. 

It  is  to  be  noted  that  the  middle  branch  of  the  Jissure  of  Sylvius  (Fig.  445, 3) 
is  very  oblique  backwards,  which  causes  the  fissure  of  Rolando  to  commence 
much  further  back  than  in  Solipeds  and  Ruminants.    This  fissure  at  first  ascends 


BRAIN   OF   THE   PIG   (UPPER   FACE). 

B,  Medulla  oblongata.     C,  Cerebellum 


NATURAL  SIZE. 

1,  middle  lobe  of 
ditto  ;  2,  2,  lateral  lobe  of  ditto.  S,  Inter-hemispheri- 
cal fissure  :  3,  3,  crucial  fissure ;  4,  4,  deep  fissure 
separating  the  first  frontal  convolution,  9,  from  the 
second;  12,  13,  5,  fissure  of  Rolando;  6,  first  parietal 
convolution;  7,  second  ditto;  8,  limited  frontal  convo- 
lution ;  10,  annectent  gyrus  between  the  limiting  fron- 
tal convolution  and  frontal  convolutions  (probably  the 
sigmoid  gyrus)  ;  11,  lobule  of  the  curved  plait. 


800 


THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 


backwards,  describes  a  marked  curve  with  concavity  antero-inferior,  then  returns 
forwards,  and  terminates  by  two  branches  at  some  distance  from  the  sigmoid 
gyrus,  from  which  it  is  separated  by  a  plait  that  unites — as  in  Ruminants — the 
first  parieto-occipital  convolution  to  the  anterior  convolutions.  The  result  of 
this  arrangement  is  that  the  frotital  lobe  extends  well  backwards  on  the  external 
face  of  the  hemisphere.  On  the  other  hand,  the  convolution  that  occupies  the 
position  of  the  lobule  of  the  curved  plait  is  much  reduced  ;  it  communicates  by  an 
annectent  gyrus  with  the  parieto-occipital  lobe.  The  latter  occupies  two-thirds  of 
the  upper  face  of  the  hemisphere  ;  it  is  limited  in  front  by  a  very  evident  crucial 


LATERAL  FACE  OF  THE  DOG  S  BRAIN. 


BULLDOG. 


1,  Inter-hemispherical  fissure;  2,  crucial  fissure;  3,  fissure  of  Sylvius;  4,  fissure  of  Rolando;  5, 
olfactory  bulb  ;  6,  temporal  lobe;  7,  7,  sigmoid  gyrus  ;  8,  9,  the  two  convolutions  of  the  parieto- 
occipital lobe;  10,  convolution  of  the  curved  plait;  11,  12,  the  two  plaits  of  the  ascending  frontal 
convolution  ;  13, 14,  frontal  convolutions  ;  15,  annectent  gyrus  uniting  the  ascending  frontal  to  the 
frontal  convolutions  ;  16,  plait  uniting  the  external  parietal  to  the  frontal  convolutions  ;  17, 
annectent  gyrus  uniting  the  internal  parietal  convolution  to  the  sigmoid  gyrus.  C,  Cerebellum  ;  Bu, 
medulla  oblongata ;  P,  Pons  Varolii. 


fissure  and  a  sigmoid  gyrus.    The  temporal  lobe  is  well  defined  ;  its  parallel  sulcus 
is  completely  effaced. 

To  sum  up  :  in  the  Dog,  the  lobes  and  lobules  observed  in  Solipeds  and  Rumi- 
nants are  found  ;  their  relative  extent  alone  is  changed.  A  word  has  to  be  said 
with  regard  to  the  frontal  and  parieto-occipital  lobes.  The  fii-st  is  enveloped  by 
an  ascending  frontal  convolution  that  describes  a  very  sudden  flexuosity,  and 
enters  the  sigmoid  gyrus.  The  second  frontal  convolution  immediately  surrounds 
the  middle  branch  of  the  Sylvian  fissure  ;  behind,  it  has  the  same  relations  with 
the  ascending  convolution  as  in  the  Horse  ;  in  front,  it  passes  into  that  convolu- 
tion.   Lastly,  the  first  frontal  convolution  is,  like  the  orbital  lobe  it  surmounts, 


TEE  CEREBRUM. 


80] 


suddenly  and  greatly  flattened  on  each  side  ;  it  is  nearly  smooth,  and  is  joined, 
behind  and  downwards,  to  the  second  frontal  convolution  and  external  root  of 
the  olfactory  lobe  ;  it  is  confounded,  above,  with  the  convolution  surrounding 
the  crucial  fissure.  The  upper  face  of  the  parieto-occipital  lobe  forms  a  longer 
triangle  than  in  Solipeds  and  Ruminantl. 

^\\Q  first  parieto-occipital  convolution,  double  as  in  the  other  animals,  bifurcates 
in  front ;  its  internal  branch  runs  into  the  extremity  of  the  second  convolution 
and  the  sigmoid  gyrus,  while  its  external  branch,  as  in  the  Ox,  passes  on  to  the 
ascending  frontal  convolution.  If  we  supposed  this  branch  interrupted  by  a 
notch,  the  fissure  of  Rolando  would  be  disposed,  in  front,  in  the  same  way  as  in 
Solipeds. 

Cat. — The  brain  of  the  Cat  is  more  regularly  ovoid,  and  more  flattened  than 


Fig.  446. 


Fig.  447. 


BRAIN   OF   THE   CAT  (NATURAL  SIZE). 

B,  Medulla  oblongata.  c,  Cerebellum :  1, 
middle  lobe  of  ditto ;  2,  3,  lateral  lobes  of 
ditto.  S,  Inter-hemispherical  fissure  ;  4,  4, 
crucial  fissure ;  5,  second  parietal  convolu- 
tion; 6,  first  parietal  convolution;  7,  limiting 
frontal  convolution ;  8,  sigmoid  gyrus. 


BRAIN   OF   THE    DOG   (UPPER   FACE). 
NATURAL  SIZE. 

B,  Medulla  oblongata.  C,  Cerebellum :  1, 
middle  lobe  of  ditto ;  2,  3,  lateral  lobes  of 
ditto.  S,  Inter- hemispherical  fissure;  4,4', 
crucial  fissure  ;  5,  sigmoid  gyrus  ;  6,  second 
parietal  convolution ;  7,  first  parietal  con- 
volution; 8,  limiting  frontal  convolution; 
9,  first  and  second  frontal  convolutions. 

that  of  the  Dog.  The  convolutions,  less  flexuous  than  in  that  animal,  also  afifect 
the  longitudinal  type,  as  may  be  seen  in  Fig.  447.  The  crucial  Assure  is  placed 
quite  in  front,  near  the  anterior  extremity  of  the  hemispheres,  which  is  occupied 
by  a  very  short,  first  frontal  convolution.  The  occipital  portion  of  the  parieto- 
occipital lobe  is  very  reduced,  and  the  region  it  occupies  is  indented  to  receive  a 
part  of  the  cerebellum. 

Comparison  op  the  Cerebrum  op  Man  with  that  op  Animals. 
The  cerebrum  of  Man  (Fig.  448)  is  distinguished  by  its  regularly  ovoid  shape,  and  its  great 
development,  particularly  behind,  where  it  covers  the  cerebellum — a  feature  never  observed 
in  animals. 


802  TKE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 

Viewed  superiorly,  it  shows  the  upper  part  ot  the  frontal,  parietal,  and  occipital  lobes.  The 
frontal  lobe  is  separated  from  the  parietal  by  the  fissure  of  Rolando,  which  is  very  deep,  and 
almost  transversely  intersects  the  middle  portion  of  the  hemisphere.  The  parietal  lobe  is 
separated  from  the  occipital  by  the  external  perpendicular  fissure. 

The  fissure  of  Rolando  is  separated  by  two  large  convolutions — the  frontal  ascending  and 
parietal  ascending.  % 

The  inferior  face  of  the  hemisphere  is  intersected  by  a  deep  fissure  of  Sylvius,  at  the  bottom 
of  which  is  found  the  lobule  of  the  insula,  when  the  temporal  lobe,  situated  in  front  of  it,  is 
separated  from  the  frontal  lobe,  situated  behind  it. 

The  internal  face  presents,  besides  the  parts  described  in  animals,  two  fissures — the  internal 
perpendicular  and  vertical  branch  of  the  calloso-marginal  fissure.  Between  these  two  fissures 
is  the  central  or  quadrilateral  lobule — a  dependency  of  the  parietal  lobe  ;  in  front,  the  paracentral 
lobule  that  surrounds  the  termination  of  tlie  fissure  of  Rolando,  and  the  internal  face  of  the 
frontal  lobe ;  behind,  the  cuneiform  lobule,  the  internal  portion  of  the  occipital  lobe. 

Its  convolutions  are  larger,  and  separated  by  deeper  sulci  than  in  the  domestic  aoimals. 

Fig.  448. 


THE    BASE  OF   THE    HUMAN    BRAIN. 

1,  Longitudinal  fissure ;  2,  anterior  lobes  of  cerebrum  ;  3,  olfactory  bulb  ;  4,  lamina  cinerea  ;  5,  fis- 
sure of  Sylvius ;  6,  locus  perforatus  anticus ;  7,  optic  commissure ;  8,  tuber  cinereum  ;  9,  third 
nerve;  10,  corpus  albicantium  ;  11,  fourth  nerve  ;  12,  locus  perforatus  posticus  ;  13,  fifth  nerve; 
14,  crus  cerebri ;  15,  sixth  nerve  ;  16,  pons  Varolii ;  17,  portio  dura  of  seventh  nerve  ;  18,  middle 
lobe  of  cerebrum;  19,  portio  molliss  of  seventh  nerve;  20,  anterior  pyramid;  21,  glosso-pharyn- 
geal  nerve;  22,  olivary  body;  23,  pneumogastric  nerve;  24,  lateral  tract;  25,  spinal  accessory 
nerve;  26,  digastric  lobe;  27,  hypoglossal  nerve;  28,  cerebellum;  29,  amygdala;  30,  slender 
lobe ;  32,  posterior  inferior  lobe. 

'Yhe  frontal  convolutions  are  three  in  number;  the  third,  or  external,  indistinct  in  animals, 
is  situated  on  the  externo-inferior  part  of  the  lobule,  immediately  above  the  fissure  of  Sylvius; 
it  is  named  the  language  convolution,  or  convolution  of  Broca,  to  signify  that  this  surgeon 
demonstrated  that  it  was  the  seat  of  language.  These  convolutions,  all  proceeding  backwards, 
pass  into  the  ascending  frontal  convolution. 

The  temporal  lobe,  which  is  very  developed,  shows  three  undulating  convolutions  on  its 
surface,  distinguished  as  first,  second,  and  third. 

The  convolutions  of  the  lobule  of  the  curved  plait  are  incomparably  more  developed  than  in 
animals. 

Lastly,  the  occipital  lobe  has  three  convolutions— ^rs<,  second,  and  </jt>d— joined  to  those  of 
the  parietal  lobe  by  two  annectent  gyri. 


THE  NERVES.  803 

It  may  be  added  that  the  olfactory  lobes  arise,  as  in  animals,  from  two  orders  of  roots,  but 
they  are  small  and  entirely  hidden  beneath  the  inferior  face  of  the  frontal  lobes. 

Examined  internally,  the  brain  of  Man  offers  the  following  principal  differences  :— 

The  corpus  callosum  is  very  developed,  and,  above  the  ventricle,  forms,  from  before  to 
behind,  a  salient  angular  prolongation  named  the  frontal  cornu  and  occipital  prolongation, 
ov  forceps  major. 

There  is  nothing  to  note  concerning  the  fornix  and  septum  lucidum,  except  that  there  is 
a  ventricle  in  the  latter  which  communicates  with  the  middle  ventricle  by  a  small  aperture — 
the  vulva. 

The  lateral  ventricles  offer  remarkable  differences.  They  are  not  prolonged  into  the 
olfactory  lobes,  but  possess  a  diverticulum  that  enters  the  occipital  lobe,  below  the  forceps 
major.  This  space  is  more  or  less  developed,  and  terminates  in  a  point;  it  is  named  the 
ancyroid  or  digital  cavity,  and  shows  on  its  floor  a  small  convolution  which  has  been  designated 
the  ergot  of  Morand  (pes  hippocampi).  The  diverticulum  and  convolution  do  not  exist  in 
animals.  The  cornu  Ammonis  is  slightly  uneven  on  its  surface ;  it  is  limited,  inwardly,  by 
a  band,  and  belnw  this  by  a  grey  denticulated  lamina— the  gyrus  fornicatus. 

The  optic  thalamus  forms  an  enormous  prominence  on  the  floor  of  the  lateral  ventricle, 
between  the  caudate  nucleus  and  tlie  cornu  Ammonis,  while  it  is  entirely  covered  by  the  latter 
in  the  brain  of  animals. 


THIRD   SECTION. 
THE  NERVES. 


The  n&rves  represent  the  peripheral  portions  of  the  apparatus  of  innervation. 
They  are  cords  ramifying  in  every  part  of  the  body,  having  their  origin  in  the 
spinal  cord  or  its  prolongation — the  brain.  Before  commencing  their  special 
study,  it  is  necessary  to  possess  a  summary  notion  of  the  principal  distinctions 
of  which  they  are  susceptible,  with  regard  to  their  origin,  distribution  and 
termination. 

Structure. — The  nerves  are  formed  by  an  aggregation  of  the  nerve-tubes 
already  described.  These  are  grouped  in  primary  fasciculi,  which  are  rectilinear 
or  slightly  undulating,  and  enveloped  in  a  sheath  of  delicate  connective  tissue — • 
the  perineurium  {internum).  These  primary  fasciculi  are  again  collected  into 
bundles  to  form  secondary  fasciculi,  which  are  maintained  by  a  layer  of  fibrillar 
connective  tissue  thicker  than  the  perineurium  {perineurium  externum).  Finally, 
these  secondary  bundles  by  their  union  constitute  the  nerve,  around  which  the 
connective  tissue  becomes  condensed,  and  constitutes  the  neurilemma. 

(Extremely  small  septa  pass  into  the  secondary  bundles  of  nerves,  consti- 
tuting the  endoneurium  ;  from  this  delicate  folds  or  lamellae  are  given  off  around 
each  nerve-fibre,  corresponding  to  the  perimysium  of  individual  muscle-fibres. 
The  coverings  of  the  nerves  are  anatomically  continuous  with  the  connective 
tissue  coverings  of  the  brain  and  spinal  cord.  The  perineurium  consists  both  of 
ordinary  connective  tissue  and  elastic  tissue  ;  and  it  is  hned  by  two,  and  in 
small  nerves  by  one,  layer  of  endothelial  cells,  forming  the  sheath  of  Henle.) 

Vessels  traverse  the  connective  tissue  separating  the  fasciculi  from  each 
other ;  they  anastomose  in  a  network  with  elongated  meshes  which  are  parallel 
with  the  nerve-tubes,  and  they  are  also  surrounded  by  the  tiervi  nervorum. 

(Lymph-spaces  exist  between  the  layers  or  lamellse  of  the  perineurium,  and  it 
would  also  appear  that  each  individual  nerve  is  surrounded  by  a  lymphatic 
space,  which  is  continuous  with  the  subdural  and  subarachnoid  lymph-spaces 


804  TEE  NERVES. 

of  the  spinal  cord  and  brain,  while  it  has  no  communication  with  the  lymphatics 
in  the  vicinity  of  the  nerve.  It  follows  that  any  increase  of  pressure  in  the 
lymphatic  spaces  of  the  central  organs,  will  afPect  the  nerve-ramifications 
throughout  the  body.) 

On  the  track  of  certain  nerves  is  observed  a  greyish  enlargement,  or  ganglion. 
This  is  composed  of  a  mass  of  nerve-cells  situated  on  the  course  of  the  tubes. 
All  the  upper  roots  of  the  spinal  nerves  are  provided  with  a  ganglion.  In  these 
spinal  ganglia  in  Mammalia,  the  nerve-cells  are  unipolar,  and  the  single  prolon- 
gation is  directed  towards  the  periphery.  Ranvier  has  demonstrated  that  this 
prolongation  is  united  to  the  nerve-tubes  of  the  roots  of  the  nerves  at  an 
annular  constriction,  and  that  from  this  arrangement  there  result  T  or  Y-shaped 
tubes. 

Division. — Nerves  are  divided,  with  reference  to  their  destination,  into  two 
principal  groups  :  1.  The  cerehro-spinal  nerves,  or  nerves  of  animal  life ;  2.  The 
ganglionic  nerves^  or  nerves  of  organic  life. 

Cerehro-spinal  nerves. — These  emanate  directly  from  the  cerebro-spinal  axis, 
and  are  divided  into  two  secondary  groups  :  1.  The  cranial  or  encephalic  nerves^ 
which  arise  in  the  brain,  and  make  their  exit  by  the  foramina  at  the  base  of  the 
cranium,  to  be  distributed  almost  exclusively  in  the  head.  2.  The  spinal  or 
rachidian  nerves,  arising  in  the  spinal  cord,  and  passing  to  the  muscular  or 
tegumentary  parts  of  the  trunk  and  limbs,  through  the  intervertebral  foramina. 

After  what  has  been  said  with  regard  to  the  apparatus  of  innervation,  we 
know  that  the  fibres  composing  these  cords  are  distinguished — by  their  point 
of  origin  and  their  properties — into  fibres  of  superior  origin  or  of  centripetal 
conduct ihility,  and  fibres  of  inferior  origin  or  of  centrifugal  conductibility.  The 
first  have  a  ganglion  on  their  course. 

The  cerebro-spinal  nerves  are  exclusively  formed  of  the  first  description  of 
fibres,  and  are  named  sensitive  nerves,  as  they  conduct  the  stimulus  which  brings 
into  play  the  sensibility  of  the  brain.  They  are  distinguished  as  nerves  of  general 
sensibility  and  nerves  of  special  sense.  The  first  are  destined  to  convey  all 
stimuli  except  those  produced  by  light,  sounds,  or  odoriferous  particles ;  the 
second  exclusively  conduct  the  latter. 

The  nerves  which  are  composed  only  of  fibres  of  the  second  kind  are  called 
motor  nerves,  because  it  is  they  which  carry  to  the  muscles  the  spontaneous 
stimulus  to  motion  originated  by  the  will. 

Those  which  are  composed  at  once  of  motor  fibres  and  fibres  of  general 
sensibility,  constitute  the  mixed  nerves ;  these  form  the  largest  category. 

Ganglionic  Nerves. — These  nerves — collectively  representing  the  great  sympa- 
thetic system — form  below  and  on  the  sides  of  the  spine,  two  long  cords,  rendered 
moniliform  by  the  presence  of  ganghonic  enlargements.  In  the  constitution  of 
these  cords  nearly  all  the  cerebro-spinal  nerves  concur ;  their  ramifications — 
frequently  ganglionic  also — are  sent  to  the  viscera  of  the  neck,  the  thorax,  and 
the  abdomen. 

In  these  nerves  of  organic  life  are  found  the  two  kinds  of  nerve-tubes — fibres 
of  centripetal  and  fibres  of  centrifugal  conductibility.  But  these  tubes  appear  to 
have  only  very  indirect  relations  with  the  brain,  for  the  will  has  no  influence 
over  the  organs  which  receive  their  nerves  from  the  great  sympathetic  ;  and 
besides  this,  in  health  the  excitations  developed  in  these  organs  are  all  reflected  by 
the  spinal  cord,  and  do  not  provoke  in  any  way  the  special  activity  of  the  brain 
— they  are  not  felt. 


THE  NERVES.  805 

However  this  may  be,  it  must  be  remarked  that  the  special  anatomical  and 
physiological  characteristics  of  the  sympathetic  nerves,  should  not  cause  them  to 
be  considered  as  a  system  independent  of  the  first,  or  cerebro-spinal  nerves.  The 
fibres  composing  both  have,  in  fact,  a  common  origin  in  the  spinal  cord — or, 
rather,  those  of  the  ganglionic  nerves  emanate  from  the  nerve-cords  of  animal 
life.  In  the  considerations  which  follow,  we  will  therefore  omit  this  distinction 
of  the  nerves  into  two  groups. 

(The  nerve-fibres  in  the  sympathetic  system  of  nerves  are  chiefly  non-medul- 
lated,  and  form  the  preponderance  of  this  kind  of  nerve-fibre.  Syrnpathetic 
nerves  are  whiter  than  cerebro-spiift,!  nerves,  or  have  a  pale-grey  hue.) 

Origin  of  the  Nerves. — We  ought  to  distinguish  in  these  cords  their 
real  or  deep  origin,  and  their  superficial  or  apparent  origin. 

The  latter  is  represented  by  the  point  of  issue  of  the  roots  of  the  nerves, 
which  are  ordinarily  spread  in  a  fan-shape,  then  united — generally  after  a  very 
brief  course — into  a  single  trunk,  which  offers  at  its  commencement  a  ganglionic 
enlargement,  if  fibres  of  general  sensibility  enter  into  its  constitution.  The 
inferior  spinal  roots  issue  from  the  bottom  of  the  inferior  collateral  furrow  of  the 
spinal  cord ;  the  superior  roots  from  slightly  within  the  superior  collateral  furrow. 
Their  real  origin  is  the  point  of  departure  of  these  roots  in  the  substance  of  the 
cerebro-spinal  axis.  The  nuclei  of  the  nerves  have  been  the  object  of  much 
investigation  during  recent  years,  and  we  therefore  know  the  majority  of  them. 
It  may  be  remarked  that  the  cells  of  the  nuclei  of  the  spinal  nerves  are  larger 
than  those  of  the  grey  matter  of  the  medulla  oblongata.  Otherwise,  the  motor 
cells  diminish  in  volume  from  below  upwards — that  is,  from  the  lumbar  region 
to  the  medulla  oblongata  (Pierret). 

Distribution  of  Nerves. — The  nerve-trunks,  formed  by  the  radicles  of 
which  we  have  just  spoken,  issue  in  pairs  from  the  foramina  at  the  base  of  the 
cranium  or  in  the  walls  of  the  spine,  to  be  distributed  to  all  parts  of  the  body  by 
dividing  into  successively  decreasing  branches. 

Those  among  these  branches  which  ramify  in  the  organs  of  animal  life, 
generally  follow  the  track  of  the  deep  vessels  or  the  subcutaneous  veins,  and  are 
always  found  most  superficial.  Their  ramescence  is  effected  in  a  very  simple 
manner,  by  the  successive  emission  of  the  fasciculi  composing  the  principal 
trunks,  until  these  are  completely  expended.  These  branches  pursue  their 
course  nearly  always  in  a  direct  line  ;  only  some — as  the  ramifications  of  the 
two  principal  nerves  of  the  tongue — describe  very  marked  flexuosities,  with 
the  same  protective  intention  as  the  arteries  of  that  organ.  Anastomoses  some- 
times join  these  branches  to  one  another  ;  and  anastomoses — frequently  compli- 
cated -  unite  many  nerves  together,  forming  what  are  called  plexuses.  But  in 
these  anastomoses,  no  matter  how  comphcated  they  may  be,  there  is  never  any 
fusion  of  the  nerves,  but  merely  aggregation  of  their  fibres,  which  always  pre- 
serve their  independence,  characters,  and  special  properties.  These  anastomoses, 
then,  differ  essentially  from  those  of  arteries,  and  never  permit  two  trunks  to 
mutually  supplement  each  other  when  the  course  of  one  is  inteiTupted. 

The  nerves  sent  to  the  organs  of  vegetative  life,  and  which  arise  from  the 
two  subspinal  chains  in  the  formation  of  which  nearly  every  pair  of  nerves 
concurs,  comport  themselves  in  their  distribution  in  a  slightly  different  manner. 
They  are  enlaced  around  arteries,  forming  on  these  vessels  very  complicated 
plexiform  networks,  and  yet  the  fibres  composing  them  are  as  absolutely  inde- 
pendent as  in  the  anastomoses  above  described. 


806  THE  NERVES. 

Termination  of  the  Nerves. — This  point  should  he  examined  separately 
in  the  case  of  the  motor  and  the  sensitive  nerves — that  is,  in  the  muscles  and 
the  integumentary  membranes.  The  distinction,  however,  is  not  quite  so  abso- 
lute as  this,  for  the  muscles  always  receive  some  sensitive  tubes,  with  their  motor 
filaments. 

In  entering  the  muscles  the  7notor  nerves  divide  their  branches,  still  appearing 
as  double-contoured  tubes.  It  was  at  one  time  believed  that  these  fibres  formed 
loops  (Valentin)  in  the  interior  of  the  muscle,  and  retm'ned  to  their  starting- 
point.  This  opinion  has  become  obsolete  since  the  ultimate  termination  of  the 
nerves  has  been  studied  by  Rouget,  Krause,  Kiihne,  Kolliker,  Engelmann,  Ranvier, 
and  others.  What  is  kiaown  of  this  subject  is  as  follows  :  The  voluminous, 
double-contoured  nerve-tubes  which,  more  or  less,  cross  the  direction  of  the 
muscular  fibres,  soon  divide  and  form  pale  tubes,  with  nuclei  disseminated  on 
their  course.  These  tubes  contain  an  axis-cylinder  and  a  medullary  layer.  They 
pass  on  to  a  muscular  fibre  in  the  following  manner  :  the  nucleated  sheath  of 
the  nerve-tube  spreads,  and  is  confounded  with  the  sarcolemma  ;  the  medulla 
suddenly  stops  when  it  has  reached  the  ?notor  end-plate,  which  is  granular  and 

Fig.  449. 


MUSCULAR   FIBRES,    WITH   TERMINATION   OF   MOTOR   NERVE   (FROM    THE   GASTROCNEMIUS 
OF   THE   RANA   ESCULENTA). 

«,  Terminal  pencil  of  a  dark-bordered  nerve-fibre  ;  b,  intramuscular  naked  axis-cyliuder ;  c,  nucleus 
of  the  neurilemma  ;  d,  clavate  extremities  of  the  neive  ;  e,  spaces  of  the  muscle-nuclei ;  /,  terminal 
knob  of  nerve,  with  central  fibres  and  vesicular  dilatations  of  the  nerve. 

has  small  nuclei.  The  axis-cylinder  enters  this  little  plate,  and  breaks  up  into 
fibrillae,  which  terminate  in  a  manner  unknown  on  coming  into  contact  with  the 
contractile  fibrillfe. 

(When  the  ultimate  nerve-fibre  approaches  the  muscular  fibre,  the  former 
loses  the  white  substance  of  Schwann,  while  the  axis-cylinder  pierces  the  sarco- 
lemma and  terminates  in  the  motor  end-plate.  These  plates  vary  much  in  form 
and  general  appearance.  Sometimes  they  seem  to  consist  of  very  minute  fibres, 
formed  by  the  splitting  up  of  the  axis-cylinder,  anastomosing  so  as  to  form  a 
network,  but  usually  they  take  the  form  of  irregularly  shaped  granular  masses 
or  discs,  containing  numerous  vesicular  nuclei.) 

The  mode  of  termination  of  the  sensitive  nerves  varies,  according  as  they  are 
sensorial  or  general  sensibility  nerves. 

It  appears  to  be  demonstrated  that  the  tubes  of  the  sensorial  nerves  have  at 
their  extremity  an  elongated  cell,  analogous  to  that  from  which  they  started. 
An  idea  has  been  given  of  this  arrangement  in  describing  the  olfactive  portion  of 


THE  CRANIAL   OB   ENCEPHALIC  NERVES.  Sffl 

the  pituitary  mucous  membrane.     Other  examples  will  be  given  when  studying 
the  organs  of  the  senses. 

The  other  sensitive  nerves — the  cutaneous  nerves,  for  example — have  been 
supposed  to  terminate  by  peripheral  loops,  and  again  by  free  extremities  passing 
into  a  kind  of  cell  elements.  It  is  certain  that  these  two  modes  exist  simul- 
taneously ;  recurrent  sensibility,  which  Claude  Bernard  demonstrated  in  some 
cranial  nerves,  proves  that  certain  nerves  have  pre-terminal  peripheral  loops. 
Our  own  experiments  have  shown  :^  1.  That  this  recurrent  sensibility  is  a 
general  phenomenon  belonging  to  the  sensitive  nerves  of  the  limbs,  and  even  to 
all  the  sensitive  ramifications  of  the  spinal  nerves  and  those  of  the  face.  2.  That 
the  recurrent  anastomotic  loops  are  formed  at  different  parts  along  the  course  of 
the  nerves,  either  beneath  the  integuments  or  in  their  texture.  It  may  be  added 
that  there  are  found  in  the  papillae  of  the  skin,  in  certain  regions — hand,  foot, 
lips,  tongue,  glands,  clitoris — the  corpuscles  of  Meissner,  or  tactile  corpuscles. 
These  are  composed  of  condensed  connective  tissue,  and  are  conical,  like  a  pine- 
cone,  the  summit  towards  the  periphery.  By  their  base  they  enter  one  or  more 
nerve-tubes,  which  terminate  in  enlargements.  In  the  conjunctiva,  lips,  etc., 
are  also  found  rounded  bodies  analogous  in  their  structure  to  the  tact  corpuscles, 
and  which  are  named  the  corpuscles  of  Krause.  Lastly,  on  the  course  of  the 
collateral  nerves  of  the  fingers  and  in  the  mesentery  of  the  Cat,  are  the  Pacinian 
corpuscles.,  or  corpuscles  of  Vater — small  globular  or  ovoid  bodies,  formed  of 
several  concentric  layers  of  tissue,  and  with  a  central  cavity  or  canal  into  which 
penetrates  and  terminates — by  one  or  more  enlargements — a  filament  from  the 
nerve-trunk  (reduced  to  the  axis-cylinder  only). 


CHAPTEE  I. 

The  Cranial  or  Encephalic  Nerves. 

The  cranial  nerves  leave  the  brain  in  pairs,  regularly  disposed  to  the  right  and 
left,  and  designated  by  the  numerical  epithets  of  first,  second,  etc.,  counting 
from  before  backwards. 

Willis,  taking  for  a  basis  the  number  of  cranial  openings  through  which 
the  nerves  passed,  divided  them  into  nine  pairs,  with  which  he  described  the 
first  spinal  pair,  making  it  the  tenth  in  the  series  of  cranial  nerves.  This 
division  being  faulty  in  some  respects,  it  was  sought  to  perfect  it.  Haller  com- 
menced by  removing  the  first  spinal  or  suboccipital  pair  of  nerves  to  their 
proper  region  ;  then  followed  Soemmering  and  Vicq-d'Azyr,  who  doubled  the 
seventh  pair  of  Willis,  and  reduced  his  eighth  into  three  distinct  pairs,  according 
to  considerations  derived  from  the  destination  and  uses  of  these  nerves.  The 
number  of  pairs  of  cranial  nerves,  their  order  of  succession,  and  their  nomen- 
clature were  then  estabhshed  in  the  following  manner  : — 

'  Arloing  and  Tripicr,  "  Recherches  sur  la  Sensibility  des  Teguments  et  des  Nerfs  de  la 
Main"  {Archives  de  Physiologie,  1869). 


THE  NERVES. 

Ist  pair,  or  olfactory  nerves  .      .      corresponding  to  the     1st  pair  of  Willis. 

2nd  pair,  or  optic  nerves 2nd  pair  „ 

3rd  pair,  or  common  motores  oculorum  nerves 3rd  pair  „ 

4th  pair,  or  pathetici  nerves 4th  pair  „ 

5th  pair,  or  trigeminal  nerves 5th  pair  , 

6tii  pair,  or  abducentes  nerves 6th  pair  „ 

7th  pair,  or  facial  nerves \ 

8th  pair,  or  auditory  nerves /         ^^^  " 

9th  pair,  or  glosflo-pharyngeal  nerves     ......) 

10th  pair,  or  pneumogastric  nerves >  8th  pair  „ 

11th  pair,  or  accessory  or  spinal  nerves ) 

12th  pair,  or  great  hypoglossal  nerves 9th  pair  „ 


In  the  following  table,  these  nerves  are  classed  according  to  their  properties  :— 

,    ^^  „         .  ,  (  olfactory  nerves or    Ist  pair. 

1.  Nerves  of  special  )      *•    „  o„-i 

*^  s  optic  nerves 2na   „ 

sense     .     .     .  (  auditory  nerves 8th    „ 

2.  Mixed      nerves  /"  trigeminal  nerves 5th    „ 

with        double  <  glosso-pharyngeal  nerves 9th    „ 

roots       .     .     .  (  pneumogastric  nerves 10  th    „ 

/  common  motores  oculorum  nerves       ....    3rd    „ 

9     M  t.  „^,^„o  i  pathetici  nerves 4th  „ 

8.    Motor        nerves  \  '^i  ,         ,  ^^,. 

with  single  I  abducentes  nerves 6th  „ 

,  ^     j  facial  nerves 7th  „ 

"  r  accessory  or  spinal  nerves Uth  „ 

^  great  hypo-glossal  nerves 12th  „ 

(Sir  Charles  Bell  considered  the  fourth,  seventh,  and  eighth  nerves  as  form- 
ing a  separate  system,  and  to  be  allied  in  the  functions  of  expression  and  respira- 
tion. In  consonance  with  this  view,  he  termed  them  respiratory  nerves,  and 
named  that  portion  of  the  medulla  oblongata  from  which  they  arise,  the 
respirator  1/  tract.) 

One  of  the  characteristics  of  the  cranial  nerves  being  their  diversity,  it  is 
scarcely  possible  to  study  them  as  a  whole,  and  it  is  only  in  their  origin  that 
they  resemble  each  other  in  some  points.  A  good  idea  of  their  origin  is  given 
in  Fig.  452. 

Preparation  of  the  cranial  nerves. — Four  preparations  are  necessary  for  the  study  of  the 
cranial  nerves : 

1.  A  brain  extracted  after  opening  the  cranium  by  its  base,  and  hanlened  by  prolonged 
immersion  in  alcohol  or  very  diluted  nitric  acid.  This  piece  permits  the  origin  of  the  nerves 
to  be  studied  (Fig.  424). 

2.  The  superficial  nerves  of  the  head  :  these  are  the  auricular  nerves,  and  the  divisions  of 
the  subzygomatic  plexus,  with  the  infra-orbital  and  mental  branches,  as  well  as  the  superficial 
ramuscules  of  the  three  nerves  of  the  ophthalmic  branch  of  the  fifth  pair  (Fig.  168). 

3  A  piece  disposed  as  in  Fig.  454,  for  the  study  of  the  maxillary  nerves.  To  prepare  it, 
the  greater  part  of  the  masseter  muscle  should  be  removed  in  dissecting  the  masseteric  nerve; 
the  globe  of  the  eye  must  be  extirpated,  the  orbital  and  zygomatic  processes  excised,  the  two 
maxillary  sinuses  opened,  and  the  branch  of  the  inferior  maxillary  bone  chiselled  off  as  in  the 
figure.  Lastly,  the  anastomosis  of  the  facial  with  the  subzygomatic  nerve  is  dissected,  by 
cutting  away  the  parotid  gland. 

4.  The  deep  nerves,  including  those  of  the  globe  of  the  eye ;  this  preparation  should  be 
made  by  following  exactly  the  instructions  given  for  dissecting  the  arteries  of  the  head.  Figs. 
450  and  454  will  serve  as  guides  for  details. 

The  pneumogastric  and  spinal  nerves,  which  are  not  included  in  these  considerations, 
should  be  prepared  and  studied  at  the  same  time  as  the  great  sympathetic.  When  treating  of 
the  latter,  we  will  refer  to  them. 

Preparations  2.  3,  and  4  may  be  made  on  one  head,  and  simultaneously.  With  this  object, 
the  head  is  skinned,  and  the  facial  panniculus,  beneath  which  the  branches  of  the  subzygo- 
matic plexus  lie,  is  removed.     The  parotid  gland  is  carefully  dissected  off,  to  expose  the  sub« 


TEE  CRANIAL   OR   ENCEPHALIC  NERVES.  809 

parotideal  branches  of  the  facial  nerve ;  then  proceed  as  if  preparing  the  muscles  of  the  tongue 
and  pharynx  and  the  arteries  of  the  eye.  Finally,  the  branches  of  the  fifth  pair,  hypoglossal, 
glosso-pharyngeal,  and  ocular  nerves  are  exposed  by  freeing  them  from  the  tissues  surround- 
ing them. 

To  follow  more  easily  the  ramifications  of  the  cranial  nerves  in  their  intra-osseous  course, 
the  head  may  be  macerated  in  a  bath  of  diluted  nitric  acid.  The  bones  being  softened,  are 
more  easily  cut  and  chiselled,  while  at  the  same  time  the  nerves  themselves  are  rendered  more 
firm  and  apparent  by  the  dissolution  of  the  connective  tissue. 

1.  FiEST  Paik,  or  Olfactory  Nerves  (Figs.  423,  424). 

The  first  cranial  pair  is  constituted  by  the  olfactory  lobules,  the  anterior 
extremities  of  which  give  off  a  great  number  of  nerve-filaments ;  these  pass 
through  the  cribriform  foramina  to  ramify  in  that  part  of  the  pituitary  mem- 
brane lining  the  bottom  of  the  nasal  fossae. 

Each  olfactory  lobule  is  connected  with  the  brain  by  two  roots — an  external 
and  an  internal — both  composed  of  white  substance  (Fig.  424).  The  external 
commences  by  a  grey-coloured  convolution  which  borders,  externally,  the  tempo- 
ral lobe  of  the  hemisphere.  The  internal,  followed  from  before  backwards,  turns 
round  in  the  interlobular  fissure,  in  front  of  the  optic  commissure,  to  mix  with 
the  cerebral  convolutions.  These  two  roots  circumscribe  a  triangular  space 
occupied  by  the  extra-ventricular  nucleus  of  the  corpus  striatum,  which  they 
embrace.  In  brains  which  have  been  macerated  for  a  long  time  in  alcohol,  it  is 
easy  to  see  that  the  fibres  of  these  roots  are  continuous,  in  very  great  part,  with 
those  of  the  corpus  striatum,  and  leave  with  the  fasciculi  of  the  isthmus,  which 
radiate  and  spread  through  the  grey  matter  of  the  corpus  striatum. 

According  to  Meynert  and  Luys,  a  portion  of  the  radicular  fibres  of  the 
olfactory  nerves  intercross  in  the  substance  of  the  white  commissure  of  the 
encephalic  isthmus. 

After  the  union  of  its  two  roots,  the  olfactory  lobule  is  constituted  by  a  wide 
white  band  that  passes  forward  on  the  inferior  face  of  the  hemisphere,  and  soon 
terminates  in  a  very  elongated  oval  dilatation  lodged  in  the  ethmoidal  fossa. 
This  bulb  is  formed  by  grey  substance  on  its  inferior  face,  and  white  substance 
on  the  superior.  It  is  said  to  be  a  flattened  ganglion  laid  on  a  band  of  white 
substance,  which  at  first  represents  in  itself  the  olfactory  lobule. 

We  have  already  seen  that  this  lobule  is  hollow,  and  that  it  communicates 
with  the  lateral  ventricles  of  the  brain.  This  peculiarity,  added  to  the  special 
features  of  its  external  physiognomy,  might,  it  appears  to  us,  give  rise  to  doubts 
as  to  the  real  nature  of  the  lobules  in  question.  It  is  evident  that  they  are  not 
nerves,  but  rather  dependencies  of  the  brain ;  and  it  is  only  conformable  to 
custom  that  we  describe  them  here  as  the  first  pair  of  cranial  nerves. 

The  real  olfactory  nerves  are  the  filaments  which  arise  from  the  inferior  face 
of  the  ganglion  or  oJfactory  bulb,  and  which  traverse  the  cribriform  plate  to  reach 
the  mucous  membrane  of  the  nose.  Their  number  corresponds  to  the  ethmoidal 
foramina.  At  first  very  soft,  delicate,  and  easily  torn,  they  are  enveloped  on 
their  passage  through  these  apertures  by  a  very  strong  neurilemma,  which  gives 
them  great  solidity.  Some,  in  ramifying,  descend  on  the  septum  nasi ;  others — 
and  these  are  the  most  numerous — divide  on  the  ethmoidal  cells,  where  they  form 
fine  and  more  or  less  plexuous  tufts  among  the  no  less  interesting  divisions  of 
the  ethmoidal  branch  of  the  ophthalmic  artery.  Their  terminal  extremities  do 
not  descend  below  the  upper  third  of  the  nasal  fossae,  but  remain  confined  to  the 
bottom  of  these  cavities. 


810  THE  NERVES. 

These  are  the  special  nerves  of  smell.  They  receive  the  impression  of  odours 
and  transmit  it  to  the  brain  ;  this  function,  which  has  been  accorded  and  refused 
them  time  after  time,  appears  to  be  now  definitively  accepted. 

2.  Second  Pair,  or  Optic  Nerves  (Fig.  424). 

The  nerves  of  vision  present  for  consideration  in  their  interesting  study,  their 
origin,  course,  termination,  andi  properties. 

There  has  been  much  dispute — and  there  will  probably  be  much  more — with 
regard  to  the  origin  of  the  second  pair.  But  without  confining  ourselves  to  an 
appreciation  of  the  opinions  which  have  pervaded  science  on  this  matter,  we  will 
describe  what  we  have  observed  in  the  domesticated  animals. 

When  the  isthmus  is  isolated  from  the  brain  (Fig.  426,  12)  and  examined 
laterally,  we  recognize  on  its  anterior  limit  the  white  band  that  constitutes  the 
optic  nerve.  Studied  at  its  origin,  this  band  is  continuous,  in  the  most  evident 
manner,  with  the  external  side  of  the  thalamus  opticus,  where  it  forms  the  two 
enlargements  known  as  the  corpora  geniculata.  This  thalamus  ought,  therefore, 
to  be  regarded  as  the  point  of  departure  of  the  nerve  that  bears  its  name.  But 
as  the  external  corpus  geniculatum  is  in  contact  with  the  natis,  and  as  the 
internal  is  united  to  the  testis  by  a  band  of  white  fibres,  it  is  almost  certain, 
according  to  several  authorities,  that  the  corpora  quadrigemina  concur  in  furnish- 
ing the  constituent  fibres  of  the  optic  nerves.^ 

At  first  wide  and  thin,  the  optic  band  (tractus  opticus)  is  rolled  round  the 
cerebral  peduncle  downwards  and  forwards,  and  gradually  narrows.  Arrived  at 
the  inferior  surface  of  the  brain,  it  is  changed  into  a  funicular  cord,  which  unites 
with  that  of  the  opposite  side  to  form  the  commissure  or  chiasma  of  the  optic 
nerves  ;  this  is  only  a  temporary  fusion,  as  beyond  it  the  two  nerves  reappear, 
each  passing  into  the  optic  foramen,  to  reach  the  interior  of  the  ocular  sheath 
and  the  bottom  of  the  globe  of  the  eye. 

We  will  enter  into  some  details  on  the  relations  of  the  optic  nerves  in  the 
different  points  of  the  course  we  have  indicated. 

In  their  flat  portion,  or  origin,  they  are  comprised  between  the  cerebral 
peduncles  and  the  hemispheres.  From  the  point  where  they  arrive  free,  at  the 
inferior  face  of  the  brain,  to  the  commissure,  they  are  covered  by  the  pia  mater, 
and  adhere  by  their  deep  face  to  the  superior  extremity  of  the  peduncles. 

The  commissure  is  lodged  in  the  optic  fossa,  and  receives  on  its  deep  face  the 
insertion  of  the  small  grey  lamina  which  bounds  the  third  ventricle  in  front ;  for 
which  reason  this  is  generally  described  as  the  grey  root  of  the  optic  nerves.  But 
of  all  the  proper  connections  of  the  commissure,  the  most  important  are  certainly 
those  which  each  nerve  maintains  with  its  congener  at  their  junction.  What 
becomes  of  the  fibres  of  each  nerve  in  this  anastomosis  ?  Do  they  cross  one 
another  to  reach  the  opposite  eye  ;  or  do  they  merely  lie  together,  and  afterwards 
separate,  in  order  to  go  to  the  eye  on  their  own  side  ?  Anatomy  demonstrates 
that  the  fibres  of  the  commissure  do  not  exclusively  affect  either  of  these  arrange- 

'  To  the  optic  nerve  has  been  attributed  two  roots,  which  are  two  portion8  of  the  small  band 
of  that  name.  The  external  root  arises  in  the  optic  thalamus,  the  external  corpus  geniculatum, 
and  the  anterior  corpora  quadrigemina ;  the  internal  leaves  the  internal  corpus  geniculatum. 
According  to  certain  authorities,  the  two  roots  pass  to  the  game  points ;  but  others  assert  that 
they  reach  the  four  corpora  (juadrigemina. 


THE  CRANIAL   OR   ENCEPHALIC  NERVES.  811 

ments ;  for  in  studying  them  in  a  specimen  that  has  been  macerated  for  some 
days,  it  is  found  that  the  majority  cross  each  other  in  a  very  evident  manner, 
but  that  a  part  regain  the  nerve  corresponding  to  the  side  from  which  they  came. 
It  is  therefore  seen  that  the  nerves  of  the  second  pair  are  composed  of  one  kind 
of  fibres  on  this  side  of  the  commissure,  while  beyond  it  they  show  two  kinds — 
the  fibres  from  the  right  and  left  sides.  The  majority,  we  have  said,  cross  each 
other  ;  and  the  proof  of  this  is  afforded  in  certain  facts  observed  in  pathological 
anatomy,  which  are  of  sufficient  interest  to  be  mentioned  here.  In  the  cases  so 
frequently  occurring  in  the  Horse,  when  an  eye  is  lost  from  the  ravages  of 
periodic  ophthalmia  {fiuxion  periodique),  the  consecutive  atrophy  of  the  optic 
nerve  nearly  always  stops  at  the  commissure,  though  it  sometimes  happens  that 
it  gets  beyond  this  ;  and  it  is  observed  that  it  is  usually  the  nerve  opposite  to 
the  diseased  eye  which  suffers  the  most.  Otherwise,  the  arrangement  just  de- 
scribed is  only  a  degree  less  advanced  than  that  remarked  in  certain  species — in 
the  osseous  fishes,  for  instance — in  which  the  optic  nerves  entirely  cross  each 
other  without  confounding  or  mixing  their  fibres. 

But  behind  the  ganglionic  centre  of  these  nerves,  contained  in  the  corpora 
geniculatum  and  quadrigemina,  the  direct  fibres  of  the  optic  nerves  cross  each 
other,  and  reach — along  with  those  that  crossed  at  the  commissure — the  sensitive 
centre  spread  in  the  grey  substance  of  the  posterior  lobe  of  the  brain.  This  is 
the  opinion  of  Gudden,  Nicati,  Charcot,  Landolt,  etc.  ;  they  compare  the  optic 
nerves  to  the  other  cranial  nerves. 

Beyond  their  commissure,  the  nerves  of  the  second  pair  are  in  relation  with 
the  walls  of  the  optic  foramina  ;  then  with  the  posterior  rectus  muscle  {retractor 
ocuJi),  which  envelops  each  nerve  as  in  a  sheath.  In  the  orbital  cavities  they 
are  also  related  to  some  other  nerves  and  vessels. 

"With  regard  to  its  termination,  the  optic  nerve  enters  the  globe  of  the  eye 
by  piercing  the  sclerotic  and  choroid  coats,  towards  the  most  declivitous  part  of 
its  posterior  surface,  and  expands  in  the  form  of  a  membrane,  which  is  described 
in  the  apparatus  of  vision  as  the  retina.  Before  traversing  the  bottom  of  the 
eye,  this  nerve  always  becomes  markedly  constricted. 

The  study  of  the  structure  of  the  optic  nerve  reveals  some  peculiar  facts 
which  it  is  well  to  know,  though  they  are  more  curious  than  interesting.  The 
upper  part  is  entirely  destitute  of  envelope,  while  the  inferior — that  in  front  of 
the  commissure — has  a  double  neurilemma.  The  external  layer  of  this  is  only 
a  dependency  of  the  dura  mater— a  kind  of  fibrous  sheath  attached  at  one  end 
to  the  margin  of  the  optic  foramen,  and  at  the  other  to  the  sclerotica.  The 
internal,  which  is  analogous  to  the  neurilemma  of  the  other  nerves,  emanates 
"from  the  pia  mater,  and  shows  a  multitude  of  septa  (forming  the  lamina  cribrosa), 
which  keep  the  fibres  of  this  nerve  apart  from  each  other.  To  make  this 
organization  manifest,  the  nerve  should  be  steeped  in  an  alkaline  solution  for 
some  days,  and  then  washed  in  a  stream  of  water  to  remove  the  softened  nervous 
matter  ;  the  nerve  is  to  be  afterwards  tied  at  one  of  its  extremities,  inflated,  tied 
at  the  opposite  end,  and  dried.  By  means  of  some  sections,  all  the  canals  that 
lodge  the  fasciculi  of  nerve-tubules,  and  which  are  formed  by  the  internal 
neurilemma,  are  visible. 

Concerning  the  properties  of  the  optic  nerve,  we  will  say  nothing  ;  though 
they  are  analogous  to  those  of  the  other  nerves  of  special  sense.  It  transmits  to 
the  brain  the  impressions  f m'nished  by  the  sense  of  vision,  and  mechanical  irrita- 
tion of  it  does  not  cause  pain. 


812 


THE  NERVES. 


3.  Third  Pair,  or  Common  Oculo-motor  Nerves  (Figs.  424,  450). 

The  nerves  of  the  third  pair  emanate  from  the  cerebral  peduncles,  near  the 
interpeduncular  fissure,  and  at  an  almost  equal  distance  between  the  corpus 
albicans  and  the  pons  Varolii,  in  front  of  the  loats  niger.  Their  roots,  seven 
or  eight  in  each,  penetrate  the  texture  of  these  peduncles,  pass  backwards,  traverse 
the  red  nuclei  of  Stilling,  and  may  be  traced  to  their  nucleus,  placed  aV)ove  the 
anterior  border  of  the  pons  Varolii.  This  nucleus  is  united,  in  the  middle  line, 
to  that  of  the  opposite  side. 

From  the  union  of  these  roots  results  a  flattened  trunk,  which  is  at  first 
carried  outward,  and  is  almost  immediately  inflected  forward,  to  enter — along 

with  the  sixth  pair  and  the  ophthalmic 
Fig.  450.  branch  of  the  trigeminal  nerve — the 

smallest  of  the  great  supra-sphenoidal 
foramina — the  sphenoidal  fissure 
{foramen  lacerum  basis  cranii).  The 
common  oculo-motov  nerve  afterwards 
arrives,  by  the  orbital  hiatus,  at  the 
bottom  of  the  ocular  sheath,  where 
it  separates  into  several  branches 
destined  to  the  following  muscles  of 
the  eye  :  the  elevator  of  the  upper 
eyelid,  superior  rectus,  internal  rectus^ 
inferior  rectus,  posterior  rectus — ex- 
cept its  internal  fasciculus — and  the 
small  oblique.  The  branch  to  the 
latter  is  remarkable  for  its  great 
length ;  it  reaches  its  destination  in 
passing  to  the  outside  of,  and  then 
below,  the  inferior  rectus.  The 
motor  roots  of  the  ophthalmic  gang- 
lion furnished  by  this  nerve,  are  given 
off  from  the  same  point  as  the  branch 
or  the  small  oblique  muscle. 

The  nerves  of  the  third  pair  are 
purely  motor,  as  is  shown  by  their 
connections  with  the  inferior  plane 
of  the  cerebral  peduncles,  and  their^ 
exclusive  distribution  to  contractile  organs.  They  excite  all  the  muscles  lodged 
in  the  ocular  sheath,  except  the  external  rectus,  the  great  oblique,  and  posterior 
rectus.  They  also  innervate  the  constrictive  muscular  fibres  of  the  iris ;  the  dilating 
fibres  are  supplied  with  nerves  by  the  sympathetic. 

4.  Fourth  Pair,  or  Pathetici  (or  Trochlearis)  (Fig.  450,  6). 
The  pathetic  or  internal  oculo-motor  (or  trochlearis)  nerve  is  the  smallest  of  all 
the  cranial  nerves.  Its  description  is  extremely  simple.  It  arises  from  the  band 
of  Reil,  immediately  behind  the  coi-pora  quadrigemina,  by  two  short  roots,  which 
reach  the  anterior  border  of  the  valve  of  Vieussens,  where  are  some  cells,  and  from 
there — their  real  nucleus,  which  is  confounded  with  that  of  the  conunon  oculo- 
motor— after  intercrossing  on  the  middle  hue  with  the  pathetic  of  the  opposite 


KERVES   OP  THE    EYE. 

I,  Ophthalmic  branch  of  the  fifth  pair ;  2,  palpebro- 
nasal br  nch;  3,  lachrymal  nerve;  3',  temporal 
branch  of  that  nerve ;  4,  frontal  nerve ;  5,  ex- 
ternal oculo-motor  nerve  ;  6,  trochlear  nerve  ; 
8,  9, 10,  11,  branches  of  the  common  oculo-motor 
nerve;  12,  superior  maxillary  nerve;  13,  its 
orbital  branches. 


THE  CRANIAL   OB  ENCEPHALIC  NERVES.  813 

Bide,  it  is  directed  outwards,  downwards,  and  forwards,  to  disengage  itself  from 
the  deep  position  it  at  first  occupies,  and  lies  beside  the  superior  branch  of  the 
trigeminus,  accompanying  it  to  the  supra-sphenoidal  foramina,  the  smallest  of  which 
it  enters  (pathetic  canal).  This  opening  is  exclusively  intended  for  it,  and  carries 
it  to  the  bottom  of  the  ocular  sheath,  when  it  gains  the  deep  face  of  the  great 
oblique  muscle,  in  which  it  ramifies. 

The  physiological  study  of  this  nerve  gives  rise  to  some  very  interesting 
remarks,  which  we  will  sum  up  here  in  a  few  words.  The  two  oblique  muscles  of 
the  eye  pivot  the  ocular  globe  in  the  orbit,  without  causing  the  slightest  deviation 
either  upwards,  downwards,  or  otherwise,  of  the  pupillary  opening.  But  this 
rotatory  movement  is  altogether  involuntary,  and  is  only  accomplished  in  certain 
determinate  conditions.  "  Guerin,  Szokalski,  Hueck,  and  Helie  have  remarked, 
that  when  the  head  is  alternately  inclined  to  the  right  or  left,  while  the  vision  is 
fixed  on  any  object,  the  ocular  globes  describe  around  their  antero-posterior  axis 
an  inverse  rotatory  movement  that  has  the  effect  of  preserving  a  constant  relation- 
ship between  the  object  from  which  the  luminous  rays  proceed  and  the  two 
retinae.  In  this  rotatory  motion,  the  great  oblique  muscle  of  one  side  has  for  its 
congener  the  small  oblique  of  the  other  side  :  thus,  when  the  head  is  inclined  on 
the  right  shoulder,  the  right  eye  revolves  inwards  and  downwards  on  its  axis, 
under  the  influence  of  the  superior  oblique  muscle,  while  the  left  eye  turns  on 
itself  outwards  and  downwards,  through  the  action  of  the  inferior  oblique  ;  when 
the  head  is  inclined  on  the  left  shoulder,  an  inverse  movement  takes  place  in  the 
two  eyes.  This  simultaneous  rotation  of  the  eyes  around  their  antero-posterior 
diameter,  when  the  head  is  inclined  to  one  side  or  the  other,  is  necessary  for  the 
unity  of  perception  of  visual  objects  ;  if  one  of  the  two  eyes  remained  fixed  while 
the  other  turned  on  its  axis,  we  should  perceive  two  images — a  superior  corre- 
sponding to  the  healthy  eye,  and  an  inferior  to  the  diseased  one.  These  two 
images  are  visible  when  the  head  is  vertical,  and  particularly  when  it  is  inclined 
to  the  affected  side ;  they  are  merged  in  one  when  the  head  is  carried  to  the 
healthy  side."  ^ 

The  involuntary  action  of  the  oblique  muscles  of  the  eye  in  this  rotatory 
movement,  strongly  attracts  attention  to  the  nerves  which  these  muscles  receive, 
and  stimulates  a  desire  to  learn  the  particular  conditions  which  permit  them  to 
act  as  excito-motors  independently  of  the  will  ;  although  they,  as  well  as  the 
muscles  which  they  supply,  belong  to  those  of  animal  life.  In  the  present  state 
of  science,  nothing  positive  can  be  affirmed  on  so  delicate  a  subject.  There  are, 
nevertheless,  two  interesting  remarks  to  make  :  the  pathetic  nerve  is  excliisively 
destined  to  the  superior  oblique  muscle,  and  the  long  branch  sent  by  the  common 
oculo-motor  nerve  to  the  inferior  oblique  does  not  give  any  filament  to  the  neigh- 
bouring parts.  This  branch  is,  therefore,  also  the  exclusive  nerve  of  the  inferior 
oblique,  and  may  be  considered  as  a  second  pathetic. 

(Sir  Charles  Bell  designated  the  fourth  nerve  the  "  respiratory  nerve  of  the 
eye,"  and  asserted  that  it  was  large  in  all  animals  capable  of  much  expression.) 

5.  Fifth  Paie,  or  Trigeminal  Nerves  (Figs.  451,  452,  453,  454). 

The  nerve  we  are  about  to  describe  has  also  been  named  by  Chaussier  the 

trifacial  nerve.     It  is  distinguished  among  all  the  cranial  nerves  by  its  enormous 

volume,  the  multiplicity  of  its  branches,  the  variety  of  its  uses,  and  its  connections 

with  the  great  sympathetic  system.     It  therefore  requires  to  be  described  as  com- 

'  Sappey,  Anatomie  Descriptive. 

54 


814 


THE  NERVES. 


pletely  as  possible  ;  and  in  this  description  we  will  include  the  study  of  the  cephalic 
ganglia  of  the  great  sympathetic  system,  which  ought  to  be  regarded  as  annexes 
of  the  fifth  pair. 

Origin. — The  trigeminus  belongs  to  the  category  of  mixed  nerves,  as  it 
possesses  two  roots — ^one  sensitive,  the  other  motor. 

Sensitive  root  (Fig.  426). — This  is  the  largest  root.  It  emanates  from  the 
outside  of  the  pons  Varolii,  near  the  middle  cerebellar  peduncle,  and  is  directed 
forward  and  downward  to  gain  the  anterior  portion  of  the  foramen  lacerum, 
where  it  terminates  in  a  very  large  semilunar  enlargement — the  Gasserian  ganglion. 
Flattened  above  and  below,  and  wider  in  front  than  behind,  this  root  on  the 
outer  side  is  about  |  of  an  inch  in  length,  but  the  inner  side  is  double  that 
measurement,  because  of  the  oblique  position  of  the  gangUon  which  continues  it. 

If  it  be  traced  into  the  substance  of  the  pons  Varolii,  it  will  be  found  that  the 
fibres  of  the  latter  separate  for  its  passage  from  the  deep  plane  it  at  first  occupies. 

Fig.  451. 


DIAGRAM   OF    A   SECTION    OF   THE    PONS    VAROLII  OF   MAN,    AT  THE    ISSUE   OF    THE    FIFTH    PAIR 
OR   TRIGEMINAL   NERVE. 

PP,  Pyramids  ;  Pr,  transverse  fibres  of  the  pons  Varolii,  with  stratification  of  the  grey  substance  ;  TT, 
grey  substance  in  the  floor  of  the  fourth  ventricle  (locus  cceruleus) ;  CP,  gelatinous  substance  of 
Rolando;  T,  ascending  roots  of  the  trigeminus,  curving  to  emerge  from  the  pons — great  or 
sensitive  root  of  the  trigeminus  ;  MA,  motor  nucleus  of  the  trigeminus  ;  M'A',  small  root  or  motor 
root  of  the  trigeminus  (masticator  nerve) ;  T',  fifth  pair  at  its  emergence ;  x,  x,  raph^. 


The  following  is  the  manner  in  which  it  comports  itself  in  this  plane  :  This  root  is 
separated  into  two  orders  of  fibres — posterior  and  anterior.  The  first  pass  beneath 
the  arcif orm  fasciculi  of  the  pons  VaroHi,  to  be  continued  with  the  grey  mass  in  the 
medulla  oblongata  (Fig.  451,  CP),  which  here  represents  the  superior  grey  cornu 
of  the  spinal  cord ;  the  others,  anterior,  separate  from  each  other,  and  soon 
become  confounded  with  the  mass  of  cells  in  the  interior  of  the  isthmus,  on  the 
walls  of  the  aqueduct  of  Sylvius.  Others,  finally,  reach  the  locus  cmrulms  (TT) — 
a  portion  of  the  grey  substance  on  the  floor  of  the  fourth  ventricle.  The  sensi- 
tive nucleus  of  the  trigeminus  extends  from  the  pons  Varolii  to  the  neck  of  the 
medulla  oblongata  ;  it  is  very  long  (Fig.  452,  F,  F',  F')-  The  fibres  of  the 
trigeminus — or  the  cells  which  receive  these  fibres — are  in  communication  with 
several  cranial  nerves,  particularly  the  pneumogastric,  glosso-pharyngeal,  facial, 
and  auditory  (Fig.  452). 

Semilunar  or  Gasserian  ganglion  (Fig.  425, 18).— This  ganglion,  which  receives 
the  sensitive  root  of  the  trigeminus,  is  crescent-shaped,  its  concavity  being  turned 
backwards  and  inwards.     It  may  be  said  to  be  embedded  in  the  fibro-cartilaginous 


THE  CRANIAL   OR  ENCEPHALIC  NERVES. 


815 


substance  which  in  part  closes  the  occipito-spheno-temporal  hiatus,  and  divides  it 
into  several  particular  foramina.  Its  superior  face  is  covered  by  the  dura  mater, 
and  sends  a  number  of  filaments  to  that  membrane. 

The  Gasserian  gangUon  is  not  continued  by  a  single  trunk,  but  immediately 
divides  into  two  thick  branches,  one  of  which  leaves  the  cranium  by  the  foramen 
ovale — an  opening  formed  by  the  above-named  hiatus  ;  while  the  other  is  lodged 
in  the  external  fissure  in  the  intra-cranial  surface  of  the  sphenoid  bone,  and  passing 
along  it  as  far  as  the  entrance  to  the  supra-sphenoidal  foramina,  bifurcates. 

Hence  it  results  that  the  trigeminus  is  divided — even  at  its  origin — into  three 
branches  :  two  superior — the  oph- 
thalmic branch  of  Willis,  and  the 
superior  maxillary  nerve,  commenc- 
ing by  the  same  trunk  ;  and  an 
inferior,  which  constitutes  the  in- 
ferior maxillary  nerve. 

Motor  or  small  root  (Fig.  426, 
8). — This  is  a  flattened  band  which 
emerges  from  the  pons  Varolii,  at 
the  inner  side  of  the  principal  root. 
Its  fibres  may  be  easily  followed  to 
the  interior  of  the  pons  Varolii 
(Fig.  451,  M'A')  ;  they  disappear 
in  the  nucleus  of  grey  substance 
situated  inside  the  nucleus  of  the 
principal  sensitive  root,  near  the 
floor  of  the  fourth  ventricle  (MA). 
Leaving  the  pons  Varolii,  this  root 
passes  forwards  on  the  inferior  face 
of  the  Gasserian  ganglion,  which  it 
crosses  in  a  diagonal  manner  out- 
wards, and  beyond  which  it  inti- 
mately unites  with  the  fibres  of  the 
inferior  maxillary  nerve.  The 
superior  maxillary  nerve  and  the 
ophthalmic  branch  do  not  receive 
any  fibres  from  it.  In  the  fifth 
pair,  then,  it  is  only  the  inferior 
maxillary  nerves  which  are  at  the 
same  time  sensitive  and  motor,  and 
are  real  mixed  nerves. 

A,  Ophthalmic  Branch  (or 
Nerve  of  Willis)  (Fig.  450,  1).— This  is  the  smallest  of  the  three  divisions 
furnished  by  the  Gasserian  ganglion  ;  it  proceeds  by  a  trunk  common  to  it  and 
the  maxillary  nerve,  which  will  be  described  hereafter.  This  branch  enters  the 
smallest  of  the  large  supra-sphenoidal  foramina,  along  with  the  common  and  ex- 
ternal oculo-motor  nerves,  and  in  the  interior  of  this  bony  canal  it  divides  into 
three  ramuscules,  which  reach  the  bottom  of  the  ocular  sheath  by  the  orbital  hiatus. 

These  ramuscules  are  : 

1.  The  frontal  or  supra-orbital  {supra-trochlear)  nerve. 

2.  The  lachrymal  nerve. 


LATERAL  VIEW  OF  THE  MEDULLA  OBLONGATA,  SHOW- 
ING THE  ARRANGEMENT  OF  THE  FIFTH  PAIR,  AND 
RELATIVELY  OF  THE  MOST  IMPORTANT  NUCLEI. 

Py,  Pyramidal  tract ;  Gf,  genu  facialis,  or  bend  of  the 
facial  nerve ;  Os,  superior  olivary  body  ;  0,  inferior 
ditto  ;  Py.Kr,  decussation  of  pyramids.  The  nuclei, 
situated  near  the  middle  line,  are  darker  tinted. 
The  numerals  represent  the  roots  of  the  cranial 
nerves,  according  to  their  number. 


816  •  TEE  NERVES. 

3.  The  nasal  or  palpebro-nasal  nerve. 

1.  Frontal  or  Supra-orbital  Nerve  (Fig.  450,  4). — This  is  a  flat,  volu- 
minous branch  placed  on  the  inner  wall  of  the  ocular  sheath,  and  proceeding 
nearly  parallel  with  the  great  oblique  muscle  of  the  eye  to  the  supra-orbital  fora- 
men, into  which  it  passes  along  with  the  artery  of  the  same  name.  Undivided 
before  its  entrance  into  this  orifice,  immediately  after  its  exit  from  it,  it  separates 
into  several  ramuscules,  which  meet  the  anterior  auricular  nerve,  and  are  expended 
in  the  skin  of  the  forehead  and  upper  eyelid. 

2.  Lachrymal  Nerve  (Fig.  450,  3). — This  is  composed  of  several  filaments, 
which  ascend  between  the  ocular  sheath  and  the  elevator  muscle  of  the  eyelid  and 
superior  rectus,  to  enter  the  lachrymal  gland.  One  of  these  (Fig.  450,  3') 
traverses  the  occular  sheath  behind  the  orbital  process,  and  places  itself — from 
before  to  behind — on  the  external  surface  of  the  zygomatic  process,  where  it 
divides  into  a  number  of  ramuscules,  some  of  which  mix  with  those  of  the  anterior 
auricular  nerve  to  form  the  plexus  of  that  name,  while  the  others  pass  directly  into 
the  anterior  muscles  and  integuments  of  the  ear. 

3.  Nasal  or  Palpebro-nasal  Nerve  (Fig.  450,  2). — This  describes  a  curve, 
like  the  ophthalmic  artery,  and  passes  with  that  vessel  into  the  cranium  by  the 
orbital  foramen.  After  coursing  through  the  ethmoidal  fissure  that  lodges  the 
artery,  it  traverses  the  cribriform  plate,  and  divides  into  two  filaments — an 
internal  and  external,  which  ramify  in  the  pituitary  membrane  on  both  sides  of 
the  nasal  fossa.  Before  entering  the  orbital  foramen,  this  nerve  gives  off  a  long 
branch  {infra-trochlear)  that  glides  over  the  floor *of  the  orbit,  to  reach  the  nasal 
angle  of  the  eye,  where  it  is  distributed  to  the  lachrymal  apparatus  lodged  there, 
as  well  as  to  the  lower  eyelid  ;  it  also  detaches  a  long  filament  to  the  membrana 
nictitans  and  the  sensitive  roots  of  the  ophthalmic  ganglion,  which  will  be  noticed 
hereafter. 

B.  Superior  Maxillary  Nerve  (Figs.  425,  19  ;  458, 15). — This  nerve  is 
the  real  continuation  of  the  superior  trunk  given  off  by  the  Gasserian  ganglion, 
where  we  will  begin  to  follow  it  to  its  termination,  examining  briefly  the  ophthal- 
mic branch  already  described  as  a  collateral  division  of  this  trunk. 

Remarkable  for  its  volume,  and  its  prismatic  and  funicular  shape,  the  superior 
maxillary  nerve  proceeds  from  the  inner  and  upper  section  of  the  semilunar  gang- 
lion, and  at  first  occupies  the  fissure  on  the  internal  face  of  the  sphenoid  bone, 
outside  the  cavernous  sinus,  and  is  covered  at  this  point  by  the  dura  mater. 
After  sending  the  ophthalmic  branch  into  the  smallest  of  the  great  supra- 
sphenoidal  conduits — the  great  sphenoidal  fissure — it  enters  the  most  spacious  of 
these  openings — the  foramen  rotundum — arrives  in  the  orbital  hiatus  beneath  the 
ocular  sheath,  and,  with  the  internal  maxillaiy  artery,  passes  along  the  space  filled 
with  fat  which  separates  that  hiatus  from  the  origin  of  the  infra-orbital  foramen, 
which  it  follows  to  its  external  orifice  on  the  face.  There  it  terminates  in  a 
number  of  branches  named  the  infra-orbital  ramuscules  (or  pes  anserinus,  from 
their  resemblance  to  the  claws  of  a  goose's  foot). 

In  its  course,  this  nerve  gives  off  a  large  number  of  collateral  divisions,  among 
which  may  be  more  particularly  distinguished  : 

1.  An  orbital  branch. 

2.  The  great  or  anterior  palatine  nerve. 

3.  The  staphyline  or  posterior  palatine  nerve, 

4.  The  nasal  or  spheno-palatine  nerve. 

5.  The  dental  nerves. 


THE  CRANIAL  OR  ENCEPHALIC  NERVES.  817 

In  addition  to  which  are  described  : 

6.  The  infra-orhital,  or  terminal  branches  of  the  superior  mazillary  nerve. 

1.  Orbital  Branch  (Fig.  450,  13). — This  ramuscule  arises  in  the  interior  of 
the  supra-sphenoidal  canal,  and  enters  the  ocular  sheath  with  the  divisions  of 
the  ophthalmic  branch.  It  almost  immediately  breaks  up  into  two  or  three 
very  slender  filaments,  which  ascend  to  the  temporal  angle  of  the  eye,  passing 
between  the  fibrous  lining  of  the  orbit  and  the  outer  surface  of  the  motor 
muscles  of  the  eye,  and  are  distributed  to  the  eyelids  and  neighbouring 
integuments. 

2.  Great  or  Anterior  Palatine  Nerve  (or  Palato-maxillary)  (Fig. 
215,  3). — It  arises  from  the  superior  maxillary  nerve  at  the  orbital  hiatus,  from 
a  trunk  common  to  it  and  the  nasal  and  staphyline  branches  ;  it  passes  into  the 
palatine  canal  with  the  palato-labial  artery,  which  it  follows  to  the  foramen 
incisivum,  where  it  stops. 

During  its  course  in  the  palatine  canal,  this  nerve  throws  off  two  or  three 
small  filaments,  which  escape  by  particular  foramina  to  the  anterior  part  of  the 
soft  palate — median  palatine  nerve.  Freijuently  they  arise  from  a  common  trunk 
before  the  palato-maxillary  nerve  enters  its  canal,  and  -pass  to  their  destination 
by  particular  openings.  For  the  remainder  of  its  extent  on  the  roof  of  the 
palate,  this  nerve  forms,  around  the  arteries  it  accompanies,  a  plexiform  network 
similar  to  that  of  the  ganglionic  nerves  ;  the  filaments  escaping  laterally  from  it 
are  sent  to  the  soft  parts  of  the  palate,  as  well  as  to  the  gums. 

3.  Staphyline  or  Posterior  Palatine  Nerve  (Fig.  215,  8).— The  fila- 
ments composing  this  nerve  are  very  easily  separated,  and  frequently  anastomose 
with  those  of  the  preceding  nerve.  They  accompany  the  palatine  artery  in  the 
canal  of  that  name,  bend  in  front  of  the  pterygoid  process  to  penetrate  the  soft 
palate  between  the  glandular  layer  and  the  tunica  albuginea.  They  then  become 
inflected  backwards,  and  ramify  either  in  the  mucous  and  glandular  tissues  of  the 
velum  pendulum,  or  the  palato-pharyngeal  and  circumflexus-palati  muscles.  This 
destination,  therefore,  indicates  in  this  nerve  the  presence  of  motor  fibres  ;  we 
shall  see  hereafter  whence  they  come. 

4.  Nasal  or  Spheno-palatine  Nerve. — Springing  from  the  same  trunk 
as  the  two  preceding  nerves,  thicker  than  the  staphyline,  and  nearly  of  the  same 
volume  as  the  anterior  palatine,  the  nasal  nerve  passes  with  its  artery  into  the 
nasal  or  spheno-palatine  foramen,  to  penetrate  the  cavity  of  the  nose,  where  it 
separates  into  two  branches — external  and  internal,  which  are  distributed  to  the 
pituitary  membrane. 

5.  Dental  Branches. — These  are  destined  to  the  roots  of  the  upper  teeth, 
and  proceed  from  the  superior  maxillary  nerve  during  its  intra-raaxillary  course  ; 
some  even  arise  before  the  entrance  of  that  nerve  into  the  bony  conduit  which 
it  passes  through  to  reach  the  face.  These  latter — analogous  to  the  posterior 
dental  nerve  of  Man — enter  the  canal  with  the  parent  branch,  and  throw  their 
divisions  into  the  roots  of  the  last  molar  tooth,  and  sometimes  also  into  the 
second  last.  One  portion  of  them  plunges  directly  into  the  maxillary  protu- 
berance, to  be  expended  in  the  mucous  membrane  lining  it,  after  furnishing 
some  filaments  to  the  periosteum. 

Among  the  dental  branches  given  off  from  the  maxillary  nerve  during  its 
interosseous  course,  some  pass  to  the  molars,  and  others  to  the  canine  and  incisor 
teeth.  The  first — or  middle  dental  nerves  —  separate  in  groups  from  the  maxillary 
trunk  on  its  passage  above  the  roots  of  the  molar  teeth ;  they  penetrate  these 


818  ■  TEE  NERVES. 

roots  after  a  brief  forward  course,  and  give  some  thin  filaments  to  the  membrane 
lining  the  maxillaiy  sinuses. 

The  second  is  only  at  first  a  single  branch — the  anterior  dental  nei-ve — which 
rises  from  the  maxillary  trunk  shortly  before  it  leaves  its  bony  canal.  After  a 
somewhat  long  course  in  the  substance  of  the  maxillary  bones,  this  branch  becomes 
expended  in  ramuscules  for  the  canine  tooth  and  the  incisors  ;  it  is  always  accom- 
panied by  a  very  slender  aiterial  twig. 

6.  Infra-orbital  or  Terminal  Branches  of  the  Superior  Maxillary 
Nerve. — These  ramuscules  spread  on  the  side  of  the  face  in  a  magnificent 
expansion,  which  may  be  looked  upon  as  one  of  the  richest  ner\ous  apparatuses 


Fig.  453. 


GENERAL   VIEW   OF   THE   SUPERIOR  AND   INFERIOR   MAXILLARY   NERVES. 

The  eye  has  been  excised,  after  sawing  through  and  removing  the  orbital  and  zygomatic  processes. 
The  maxillary  sinuses  have  been  exposed  by  means  of  a  gouge  or  chisel,  the  masseter  muscle 
removed,  and  the  inferior  maxilla  opened  to  show  the  nerve  in  its  interosseous  course. 

1,  Facial  nerve;  2,  origin  of  the  posterior  auricular  nerve  ;  3,  filament  distributed  to  the  stylo-hyoid 
muscle;  4,  digastric  branch;  5,  trunk  of  the  anterior  auricular  nerve;  6,  origin  of  the"  cervical 
filament;  7,  plexus  formed  by  the  union  of  the  facial  and  superficial  temporal  nerve;  7',  branch 
of  that  plexus  united  to  the  infra-orbital  nerves,  15';  11,  inferior  maxillary  nerve;  8,  superficial 
temporal  nerve;  9,  masseteric  nerve;  10.  gustatory  nerve;  12,  12,  dental  branches;  13,  mylo- 
hyoidean  nerve;  14,  buccal  nerve;  15,  superior  maxillary  nerve;  16,  spheno-palatine  ganglion; 
17,  staphyline  (or  palatine)  nerve;  18,  common  carotid  ai^tery ;  J 9,  trunk  of  the  occipital;  20, 
trunk  of  the  internal  carotid;  21,  external  carotid;  22,  trunk  of  the  posterior  auricular  artery 
embraced  by  a  loop  of  the  facial ;  23,  trunk  of  the  superficial  temporal ;  24,  internal  maxillary 
artery ;  25,  trunk  of  the  deep  anterior  temporal  artery ;  26,  orbital  branch  of  the  superior 
dental;  27,  buccal  artery;  28,  inferior  dental  artery. 

in  the  animal  econon.y.  Covered  at  its  emergence  from  the  infra-orbital  foramen 
by  the  levator  labii  superioris  proprius  muscle,  this  fasciculus  descends  beneath 
the  levator  labii  superioris  alaeque  nasi  and  lateral  dilator  of  the  nostril  towards 
the  nostrils  and  upper  lip,  which  receive  the  terminal  extremities  of  its  consti- 
tuent branches  in  the  substance  of  their  muscular  and  tegumentary  tissues ; 
these  branches  are  slightly  divergent  and  flexuous,  and  for  the  most  part 
anastomose  with  a  large  motor  trunk  furnished  by  the  facial  nerve  (Fig.  453, 15'). 
C.  Infeeior  Maxillary  Nerve  (Figs.  168, 12  ;  453,  11). — At  its  exit  from 
the  cranium,  this  branch  is  situated  immediately  within  the  temporo-maxillary 
articulation,  and  thence  is  directed  forward  and  downward,   passing  at  first 


THE  CRANIAL    OR  ENCEPHALIC  NERVES.  819 

between  the  two  pterygoid  muscles,  then  between  the  inner  and  deep  face  of  the 
maxilla,  arriving  at  the  inferior  dental  foramen,  through  which  it  passes  and 
runs  along  the  whole  couree  of  the  canal,  escaping  at  last  by  the  mental  foramen 
to  form  an  expansion  of  terminal  branches  similar  to  those  of  the  superior 
maxillary  nerve,  and  named  the  mental  nerves. 

For  the  first  third  of  its  extent,  the  inferior  maxillary  nerve  is  a  flattened 
band  ;  but  beyond  this  it  becomes  thicker,  and  acquires  a  funicular  shape. 

At  its  origin  it  gives  rise  to  four  branches — 

1.  The  masseteric  nerve. 

2.  The  buccal  nerve. 

3.  The  /lerve  of  the  internal  pt&rygoid  muscle. 

4.  The  superficial  temporal  or  suhzygomatic  nerve. 

After  its  emergence  from  between  the  two  pterygoid  muscles,  it  furnishes — 

5.  The  gustatory  nerve. 

6.  The  mylo-hyoidean  nerve. 

In  its  intermaxillary  course,  it  detaches — 

7.  The  dental  branches. 

Also  a  triple  series  of  collateral  nerves,  which  we  will  study  before  describing 
the  terminal  branches  ;  these  are — 

8.  The  mental  nerves. 

The  trunk  of  the  inferior  division  of  the  fifth  pair  represents  a  mixed  nerve, 
because  it  is  formed  of  sensitive  and  motor  fibres.  Is  it  the  same  for  each  of  the 
branches  just  enumerated  :  this  is,  do  they  all  contain  fibres  of  the  two  orders  ? 
This  is  a  question  on  which  the  dissection  of  the  two  roots  has  taught  us  very 
little,  for  their  fibres  soon  become  confounded  so  intimately  that  it  has  always 
been  found  impossible  to  follow  them  separately  into  each  nerve.  But  the  study 
of  the  distribution  of  these  branches,  corroborated  by  physiological  experiments, 
has  greatly  enlightened  us  in  this  inquiry.  We  see  among  them  nerves  destined 
to  the  muscles,  and  others  to  glandular  or  integumental  structures  ;  the  first  are 
therefore  chiefly  composed  of  motor  fibres,  like  all  other  muscular  nerves  ;  and 
the  second  exclusively  contain  sensitive  fibres,  or  at  least  are  destitute  of  voluntary 
motor  fibres.  In  describing  each  branch  in  particular,  we  shall  notice  their 
special  properties. 

1.  Masseteric  Nerve  (Fig.  453,  9  ;  459,  2). — It  is  detached  from  the  prin- 
cipal trunk,  in  front  of,  though  close  to,  the  base  of  the  cranium,  bends  round  the 
anterior  face  of  the  temporo-maxillary  articulation,  and  passes  through  the 
sigmoid  notch  of  the  inferior  maxilla  to  descend  into  the  texture  of  the  masseter 
muscle  and  there  ramify. 

At  its  origin,  this  nerve  furnishes  two  filaments  which  often  proceed  from 
one  very  short  trunk,  and  ascend  to  and  expend  themselves  in  the  temporal 
muscle  ;  this  trunk  is,  then,  the  deef  posterior  temporal  nerve. 

Before  crossing  the  corono-condyloid  notch,  it  detaches  to  this  same  temporal 
muscle  a  small  branch  which  represents  the  deep  middle  temporcd  nerve. 

The  destination  of  all  these  branches  sufficiently  proves  that  they  are 
motor. 

2.  Buccal  Nerve  (Figs.  453,  14  :  459,  4). — This  nerve,  which  is  twice  the 
size  of  the  preceding,  arises  from  the  same  point,  though  slightly  below  it.  It 
is  directed  forwards,  traverses  the  external  pterygoid  muscle,  and  reaches  the 
posterior  extremity  of  the  superior  and  great  molar  gland  ;  leaving  this,  it  is 
placed  beneath  the  buccal  mucous  membrane,  and  descends  to  the  commissure  of 


820  THE  NERVES. 

the  lips,  along  the  inferior  molar  gland  and  the  inferior  border  of  the  buccinator 
muscle. 

It  gives  some  very  fine  filaments  to  the  external  pterygoid,  in  its  passage 
across  that  muscle.  Beyond  this,  it  furnishes  a  very  slender  ramuscule  to  the 
orbital  portion  of  the  temporal  muscle — the  analogue  of  the  anterior  deep  temporal 
nerve  of  Man. 

On  the  superior  molar  gland,  it  emits  a  fasciculus  of  branches  to  this  organ 
and  the  buccinator  muscle.  In  its  submucous  track  it  throws  off,  at  certain 
distances,  ramuscules  of  various  sizes  which  go  to  the  inferior  molar  gland  and 
the  buccal  membrane ;  while  its  terminal  filaments  are  expended  in  the  lining 
membrane  and  glands  of  the  lips,  near  the  commissure. 

The  majority  of  the  filaments  given  off  by  this  nerve  to  the  external  pterygoid 
and  temporal  muscles  are  doubtless  motor,  but  the  other  ramuscules  are  sensitive ; 
even  those  distributed  to  the  buccinator  muscle  are  no  exception,  for  its  sub- 
masseteric  portion  is  supplied  by  the  facial,  as  well  as  the  superficial  or  anterior 
part. 

3.  Internal  Pterygoid  Nerve. — It  forms,  with  the  preceding  nerves,  a 
single  fasciculus,  which  leaves  the  anterior  part  of  the  inferior  maxillary  nerve. 
After  crossing,  outwardly,  the  internal  maxillaiy  artery,  it  descends  between  the 
nervous  trunk  from  which  it  emanated,  and  the  external  layer  of  the  tensor 
palati  muscle,  to  go  to  the  inner  side  of,  and  become  expended  in,  the  internal 
pterygoid  muscle. 

This  nerve  is  the  smallest  branch  of  the  inferior  maxillaiy  trunk,  after  the 
mylo-hyoidean,  and  excites  the  contraction  of  the  muscle  receiving  it. 

4.  Superficial  Temporal,  Temporo-auricularis,  or  Subzygomatic 
Nerve  (Figs.  453,  8  ;  459,  3) — This  arises  from  the  inferior  maxillary  nerve, 
at  the  opposite  side  of  the  fasciculus  formed  by  the  three  preceding  branches,  or 
posteriorly.  Placed  at  first  at  the  inner  side  of  the  temporo-maxillary  articu- 
lation, and  between  it  and  the  guttural  pouch,  it  is  afterwards  directed  down- 
wards and  outwards,  passes  between  the  parotid  gland  and  the  posterior  border 
of  the  inferior  maxilla,  and  below  the  condyle  ;  it  then  bends  round  the  neck  of 
that  bony  eminence  to  arrive  beneath,  and  to  the  outside  of,  the  precited  articu- 
lation, where  it  terminates  by  anastomosing  with  the  facial  nerve. 

In  its  course  it  sends  off  numerous  fine  filaments  to  the  guttural  pouch,  the 
parotid  gland,  and  the  integuments  of  the  temporal  region.  Among  the  latter, 
it  is  necessary  to  notice  more  particularly  those  which  accompany  the  superficial 
temporal  artery. 

This  nerve  appears  to  be  exclusively  sensitive.  Section  of  it,  before  it  anas- 
tomoses with  the  facial  nerve,  does  not  really  prevent  contraction  of  the  muscles 
which  receive  the  divisions  of  the  plexus  formed  by  this  anastomosis. 

5.  Lingual  or  Gustatory  Nerve  (Figs.  453,  10  ;  459,  5). — The  gustatory 
nerve — the  principal  branch  of  the  inferior  maxillary  trunk,  which  it  almost 
equals  in  volume — is  detached  at  an  acute  angle  from  the  anterior  border  of 
that  nerve  shortly  after  its  exit  from  the  pterygoid  muscles.  To  accomphsh 
its  course,  which  it  effects  in  describing  a  slight  cm-ve  with  concavity  antero- 
posterior, it  is  directed  forwards  and  downwards,  passing  between  the  internal 
pterygoid  muscle  and  the  branch  of  the  inferior  maxillary  bone,  and  gaining  the 
base  of  the  tongue,  where  it  is  situated  beneath  the  buccal  mucous  membrane. 
It  afterwards  descends  more  deeply,  between  the  mylo-hyoid  and  hyo-glossua 
longus  muscles,  turns  round  the  inferior  border  of  the  latter — including  also 


THE  CRANIAL   OR  ENCEPHALIC  NERVES.  821 

"Wharton's  duct — to  enter  the  space  separating  the  genio-glossus  from  the  hyo- 
glossus  longus  and  brevis  muscles.  From  this  point  it  continues  to  near  the  free 
extremity  of  the  tongue,  proceeding  in  a  veiy  flexuous  manner,  and  giving  off, 
on  its  course,  divisions  equally  tortuous,  which  traverse  the  organ,  but  without 
detaching  any  ramuscules  to  the  lingual  muscles  ;  these  divisions  terminate  in 
the  middle  and  anterior  portions  of  the  lingual  mucous  membrane. 

Before  penetrating  the  mass  of  the  tongue,  this  nerve  furnishes  :  1.  At,  and 
in  front  of,  the  posterior  pillars  of  that  organ,  some  small  ramuscules  which  are 
sometimes  plexiform,  and  are  distributed  to  the  mucous  membrane  at  the  base  of 
the  tongue.  2.  Lower,  and  behind,  one  or  two  thin  filaments  which  are  carried 
to  Wharton's  duct,  and  ascend  with  it  to  the  maxillary  gland.  3.  A  sublingual 
branch,  the  divisions  of  which  enter  the  gland  of  that  name,  as  well  as  the 
mucous  membrane  covering  the  sides  of  the  tongue. 

The  gustatory  nerve  receives,  near  its  origin,  the  tympano-lingual  filament  or 
chorda  tympani — a  branch  of  the  facial  nerve  soon  to  be  described.  Its  terminal 
divisions  mix  and  anastomose  with  those  of  the  great  hypoglossal  nerve,  in  the 
deep  muscular  interstice  which  lodges  both. 

Physiology  teaches  us  that  the  gustatoiy  nerve  gives  to  the  anterior  two-thirds 
of  the  lingual  mucous  membrane  ordinary  sensation,  and,  in  addition,  that 
special  sensibility  (or  gustatory  power)  by  virtue  of  which  that  membrane  enjoys 
the  property  of  appreciating  savours.  This  is  its  exclusive  function.  With 
regard  to  the  tympanic  filament  from  the  facial  nerve,  and  which  is  joined  to  the 
gustatory,  Bernard  is  of  opinion  that  it  participates  in  the  exercise  of  this  sense 
of  taste.  Its  radiating  fibres  extend  to  the  submucous  muscular  layer  of  which 
we  have  spoken,  and  on  which  the  lingual  papillse  rest,  and  endow  it  with  the 
property  of  acting  on  these  papillse  by  adapting  them,  we  may  say,  to  the  sapid 
substances  brought  into  contact  with  them.  Lussana  goes  further  than  this, 
and,  basing  his  statement  on  observations  made  on  Man  and  on  experiments, 
asserts  that  the  nerve  of  the  tympanum  passes  to  the  mucous  membrane,  and 
endows  it  with  the  sense  of  taste.  It  may  be  added  that  Yulpian  did  not  at  one 
time  agree  to  either  of  these  opinions,  because,  according  to  his  experience,  this 
nerve  did  not  go  to  the  tongue,  but  stopped  at  the  submaxillary  ganglion  ;  now, 
however,  he  admits  that  some  of  its  fibres  pass  into  the  lingualis  muscle,  and  may 
aid  in  causing  movement  of  the  tongue.  Prevost,  of  Geneva,  believes  that  the 
chorda  tympani  joins  the  internal  branch  of  the  Ungual  nerve. 

6.  Mylo-hyoidean  Nerve  (Fig.  453,  13). — The  designation  of  this  nerve 
indicates  its  destination  and  uses.  It  goes  to  the  muscle  bearing  its  name,  and 
excites  its  contractility  ;  it  arises  opposite  to  the  preceding,  and,  like  it,  descends 
between  the  internal  pterygoid  muscle  and  the  inferior  maxillary  bone,  adhering 
somewhat  closely  to  the  latter.  But  arriving  at  the  posterior  border  of  the  mylo- 
hyoideus  muscle,  it  passes  to  the  outside  of  it,  and,  meeting  the  sublingual 
artery,  ramifies  with  it  on  the  external  face  of  that  muscle. 

7.  Dental  Branches  (Fig.  453,  12). — These  are  of  two  orders  :  some 
passing  to  the  molar,  the  others  to  the  canine  and  incisor  teeth.  Their  description 
does  not  merit  any  special  indication. 

8.  Mental  Nerves,  or  Terminal  Branches  of  the  Inferior  Maxillary 
Nerve. — Perfectly  analogous  to  the  infra-orbital  ramuscules,  these  nerves  form 
a  fasciculus  by  diverging  and  flexuous  branches,  which  leave  the  mental  foramen 
to  be  distributed  to  the  textures  of  the  lower  lip,  after  receiving  a  branch  from 
the  facial  nerve  (Fig.  453,  11'). 


822  THE  NERVES. 

D.  The  Sympathetic  Ganglia  annexed  to  the  Fifth  Pair. — These 
ganglia,  joined  by  filaments  of  communication  to  the  anterior  extremity  of  the 
great  sympathetic  nerve,  in  reality  belong  to  the  special  system  formed  by  that 
nerve-chain,  as  they  possess  the  structure  and  properties  of  the  other  ganglia 
composing  it.  It  is  therefore  necessary  that  we  should  have  a  motive  sufficiently 
powerful  to  induce  us  to  move  them  from  their  natural  category,  and  mix  up 
their  description  with  a  nerve  so  different  to  them  in  its  nature  and  functions. 
This  motive  we  find  in  the  intimate  relations  of  contiguity  and  continuity  which 
these  ganglia  manifest  towards  the  branches  of  the  trigeminus  ;  in  the  fact  that 
we  sometimes  find  them  united  to  these  branches,  and  deeply  mixed  up  with  their 
fibres  ;  and  also  because,  in  certain  cases,  they  seem  to  disappear  entirely,  and 
then  their  filaments  of  emission  or  reception  are  directly  received  or  emitted  by 
the  fifth  pair. 

The  study  we  are  about  to  undertake  of  each  of  the  ganglia,  will  fully  justify 
what  we  have  advanced.  We  will  precede  it  by  a  few  words  of  introduction,  as 
to  the  general  facts  relating  to  these  small  organs. 

The  number  of  sympathetic  ganglia  annexed  to  the  fifth  pair  is  susceptible  of 
variation,  not  only  in  different  species,  but  also  with  individuals  of  the  same  species. 

In  the  domesticated  Mammifers,  we  somewhat  constantly — though  not 
invariably — find  three  principal  ganglia  placed  on  the  course  of  the  branches 
emanating  from  the  Gasserian  ganglion.  These  are  :  1.  The  ophthalmic  ganglion, 
belonging  to  the  nerve  of  the  same  name.  2.  The  spheno -palatine  ganglion, 
annexed  to  the  superior  maxillary  branch.  3.  The  otic  ganglion,  which  lies 
beside  the  inferior  maxillary  nerve.  Anatomists  describe  other  two — the  sub- 
maxillary  ganglion  and  the'  naso-palatine  (or  Cloquefs)  ganglion ;  but  we  have 
not  yet  dissected  them  in  Sohpeds,  though  they  should  exist.  The  submaxillary 
ganglion  has  been  found  in  the  Dog  at  a  short  distance  from  the  point  where  the 
lingual  nerve  gives  off  a  branch  to  the  maxillary  gland.  It  receives  sensitive 
roots  from  the  lingual,  and  motor  roots  (vaso-motor  or  excito-glandular)  from 
the  chorda  tympani. 

These  small  bodies  possess  those  common  charactere  which  have  been  so 
clearly  indicated  by  Longet,  and  to  which  we  will  briefly  refer.  All  are  in 
communication  with  the  superior  cervical  ganglion  by  one  or  more  generally  very 
slender  filaments,  and  all  receive  one  or  more  ramuscules  from  a  sensitive  and 
a  motor  nerve  ;  these  ramuscules — the  afferent  branches  of  the  ganglia — are 
considered  as  their  roots.  All,  finally,  emit  from  their  periphery  a  more  or  less 
considerable  number  of  emergent  branches  or  ramifications,  which  share  the 
properties,  more  or  less  modified,  of  the  two  orders  of  roots.  The  description  of 
each  ganglion  therefore  includes,  independently  of  its  form,  situation,  etc.,  an 
indication  of  all  these  ramuscules — ramuscules  of  communication  with  the  superior 
cervical  ganglion  ;  afferent  ramuscules  or  roots  ;  and  emergent  ramuscules.  This 
rule  can  be  applied  to  all  the  ganglia,  and  renders  their  study  perfectly  methodical. 

1.  Ophthalmic  (Ciliary  or  Lenticular)  Ganglion. — This  ganglion  is 
readily  discovered,  as  it  is  always  in  contact  with  the  common  oculo-motor  nerve, 
and  united  to  it  near  the  point  where  the  branch  passing  to  the  inferior  oblique 
muscle  arises.  It  rarely  exceeds  the  volume  of  a  grain  of  millet,  and  is  sometimes 
so  minute  that  it  would  altogether  escape  observation,  did  we  not  know  exactly 
where  to  look  for  it. 

Its  motor  root  is  generally  formed  of  two  very  short  ramuscules  coming  from 
the  third  pair.     Its  sensitive  root,  much  longer,  proceeds  from  the  palpebro-nasal 


THE  CRANIAL   OR  ENCEPHALIC  NERVES.  823 

nerve ;  it  is  usually  through  the  medium  of  this  root  that  the  ophthalmic 
ganglion  communicates  with  the  superior  cervical  ganglion,  by  means  of  a  thin 
filament  it  receives  from  the  cavernous  plexus. 

The  emergent  filaments  leave  the  anterior  part  of  the  ganglion,  and  arrange 
themselves  in  a  flexuous  manner  around  the  optic  nerve  to  reach  the  sclerotica, 
bearing  the  name  of  ciliary  nerves.  Some  emanate  directly  from  the  palpebro- 
nasal nerve,  especially  when  the  ganglion  is  rudimentary.  Their  number  is 
uncertain,  though  it  is  usually  from  five  to  eight. 

Reaching  the  sclerotica  at  the  bottom  of  the  eye,  they  traverse  that  membrane, 
and  pass  between  its  inner  surface  and  choroid  coat  to  the  ciUary  circle  (or 
ligament),  where  each  divides  into  two  or  three  ramuscules  that  anastomose  with 
those  of  the  adjacent  ciliary  nerves,  and  in  this  manner  they  form  a  circular 
plexus.  From  the  concavity  of  this  nerve-circle  arises  a  series  of  plexuous 
divisions,  which  are  spread  over  the  iris,  influencing  its  contractile  property. 

2.  Spheno-palatine,  or  Meckel's  Ganglion. — The  largest  of  the  cranial 
ganglia,  nothing  is  more  variable  than  its  arrangement.  The  following  appears 
to  be  the  most  constant :  in  raising  the  superior  maxillary  nerve  in  its  course 
across  the  space  separating  the  orbital  from  the  maxillary  hiatus,  we  discover, 
lying  on  the  upper  border  of  the  spheno-palatine  nerve,  a  long,  grey-coloured 
enlargement ;  this  is  the  gangUon  we  are  about  to  describe. 

It  is  elongated  and  slender,  irregularly  fusiform,  constricted  at  different 
points  of  its  extent  and  dilated  in  others  ;  it  is  not  attached  to  the  spheno- 
palatine nerve  by  simple  cellular  adhesions  or  by  some  branches  tin-own  from  one 
cord  to  the  other,  but  is  intimately  united  to  it  by  means  of  a  most  complicated 
intercrossing  of  fibres,  in  such  a  way  that  the  spheno-palatine  ganglion  really 
forms  part  of  the  nerve  of  that  name. 

Affere?it  branches. — It  receives,  posteriorly,  the  Vidian  nerve — a  composite 
ramuscule  which  constitutes  its  motor  root,  and  connects  it  with  the  superior 
cervical  ganglion.  This  nerve  will  be  described  with  the  facial,  as  that  trunk 
furnishes  ins  principal  portion.  Its  sensitive  roots  naturally  come  from  the 
spheno-palatine  nerve  ;  they  are  as  remarkable  for  their  number  as  their  volume, 
and  also  enter  the  posterior  part  of  the  ganghon. 

Emergent  branches. — Four  series  of  these  are  recognized  : 

(1)  A  very  numerous  series  which  is  detached  at  a  right  angle  from  the 
superior  border  of  the  ganglion,  and  proceeds  towards  the  ocular  sheath.  The 
majority  appear  to  be  lost  in  that  fibrous  membrane,  but  we  have  seen  some  pass 
through  it,  creep  on  the  lower  and  inner  wall  of  the  orbit,  and  arrive  at  the 
margin  of  the  orbital  foramen.  There  they  were  manifestly  united  to  the  other 
filaments  coming  from  the  palpebro-nasal  nerve,  and  formed  a  small  plexus,  the 
divisions  of  which  seemed  destined  to  the  ophthalmic  vessels,  and  even  to  some  of 
the  muscles  of  the  eye — more  especially  the  oblique  ones.  Among  these  divisions, 
we  have  observed  some  which  went  to  join  the  nerve  of  the  membrana  nictitans. 

(2)  A  second  series  proceeding  from  the  opposite  border,  and  establishing  a 
union  between  the  ganglion  and  the  spheno-palatine  nerve,  or  passing  to  the 
palatine  nerves  in  a  more  or  less  complicated  plexiform  manner,  to  increase  them. 

(3)  A  group  arising  from  the  anterior  extremity  and  immediately  passing  to 
the  spheno-palatine  nerve. 

(4)  A  last  fasciculus  detached  from  the  posterior  extremity,  to  enter  the  two 
great  supra-sphenoidal  canals. 

Such  is  the  usual  aiTangement  of  the  spheno-palatine  ganglion.     "We  have 


824  THE  NERVES. 

found  it  divided  into  three  small  masses,  connected  with  each  other  by  numerous 
filaments  of  a  deep  grey  colour,  and  free  from  all  connection  with  the  spheno- 
palatine nerve.  The  small  posterior  mass  in  this  case  received  the  Vidian  nerve 
and  the  sensitive  roots  from  the  fifth  pair.  The  distribution  of  the  emergent 
branches  was  unaltered. 

Among  the  anatomo-physiological  facts  pertaining  to  the  study  of  this 
ganglion,  we  may  remark  that  the  staphyline,  or  posterior  palatine,  nerve  derives 
from  it  the  motor  property  which  permits  it  to  cause  contraction  of  the  muscles 
in  the  soft  palate. 

3.  Otic  or  Arnold's  Ganglion. — It  appears  to  us  that  the  presence  of 
this  gangUon  is  not  constant ;  for  we  have  sometimes  found  it  replaced  by  a  small 
plexus,  provided  with  some  ahnost  microscopic  ganghonic  granules. 

When  it  does  exist,  it  presents  itself  as  a  small  fusiform  enlargement  placed 
within  the  origin  of  the  inferior  maxillary  nerve,  beneath  the  insertion  of  the 
Eustachian  tube.  To  discover  it,  we  have  only  to  look  for  the  commencement  of 
the  buccal  nerve,  to  which  it  is  joined  by  some  filaments  that  are  so  short  and 
thick,  that  we  might  imagine  it  to  be  fused  on  that  trunk. 

Its  sensitive  roots  are  represented  by  the  preceding  filaments.  The  small 
superficial  petrosal  nerve,  coming  from  the  facial,  constitutes  its  motor  root. 
From  the  sympathetic  ramuscule  accompanying  the  internal  maxillary  artery,  it 
receives  \i^  filament  of  communication  with  the  superior  cervical  gangUon. 

Among  its  efferent  ramuscules  must  be  cited  a  superior  filament,  which  enters 
the  petrous  portion  of  the  temporal  bone  to  disappear  in  the  internal  muscle  of 
the  malleus  (tensor  tympani) ;  and  two  inferior  filaments  of  a  more  considerable 
volume,  which  separate  in  numerous  ramuscules  for  the  pterygoid  muscles,  the 
Eustachian  tube,  and  the  tensor  and  levator  palati  muscles. 

PHYSiOLoaiCAL  R6suMi6  OF  THE  FiFTH  Pair. — The  trigeminus  conveys 
sensation  to  the  skin  covering  the  head,  to  the  eyelids,  the  soft  and  hard  palate, 
the  nasal  fossae  and  sinuses,  the  nostrils,  the  greater  portion  of  the  tongue,  the 
saUvary  glands  and  cheeks,  and  the  upper  and  lower  lips.  The  enormous  tuft 
formed  by  the  terminal  branches  of  the  superior  maxillary  nerve,  endow  the 
upper  lip  with  the  attributes  of  an  organ  of  very  exquisite  tact. 

The  gustatory  branch  is,  for  the  anterior  two-thirds  of  the  tongue,  the  essential 
instrument  of  the  sense  of  taste. 

By  its  motor  root,  the  inferior  maxillary  nerve  produces  contraction  of  the 
muscles  that  bring  the  jaws  into  apposition — all  those  composing  the  masseteric 
region,  except  the  digastricus.  This  root  is  often  designated,  in  consequence  of 
this  function,  the  masticatory  nerve. 

The  fifth  pair  also  influences — as  is  demonstrated  by  vivisections  and  the 
observation  of  pathological  facts — the  secretion  of  the  mucous  membranes  and 
glands  receiving  its  filaments.  Moussu  believes  he  has  experimentally  proved 
that  the  excito-secretory  fibres  of  the  inferior  molar  and  the  parotid  gland— in  the 
Horse  and  Ruminants — proceed  from  the  fifth  pair,  and  not  from  the  facial  nerve.^ 

Finally,  it  is  admitted  that  the  nutrition  of  the  tissues  in  which  the 
trigeminus  ramifies  depends  upon  this  nerve. 

'  He  says,  with  regard  to  the  Horse :  "  The  excito-secretory  nerve  of  the  parotid  can  be 
isolated  from  the  Gaeserian  ganglion.  It  is  composed  of  from  four  to  five  filaments,  which  lie 
beside  either  the  subzygomatic  or  the  inferior  maxillary  nerve  for  a  very  short  distance;  then 
it  is  placed  on  the  surface  of  the  guttural  pouch,  and  reaches  the  posterior  border  of  the  inferior 
maxilla  and  internal  maxillary  vein,  to  enter  the  parotid  gland." 


THE  CRANIAL  OR  ENCEPHALIC  NERVES. 


The  ramuscules  sent  by  the  sympathetic  chain  to  the  Gasserian  ganglion,  are 
perhaps  not  foreign  to  the  part  the  lifth  pair  seems  to  play  in  the  secretory  acts — 
nutritive  and  vaso-motor. 

Jolyet  has  found  in  the  superior  maxillary  nerve,  vaso-dilator  filaments  for 
the  mucous  membrane  of  the  nasal  fossae,  the  skin  on  the  wings  of  the  nostrils 
and  lips,  and  the  mucous  membrane  of  the  latter  and  the  gums. 

6.  Sixth  Paie  (Abducentes),  oe  External  Oculo-motor  Nerves  (Fig.  450,  5). 

The  external  oculo-motor  arises  from  the  medulla  oblongata,  immediately 
behind  the  pons  Varolii,  by  from  five  to  eight  converging  roots,  which  appear 
to   issue  from  between   the 

inferior    pyramid    and    the  Fig-  ^54. 

lateral  fasciculus  of  the  me- 
dulla oblongata  (Fig.  424,  9). 
Its  nucleus  is  confounded  with 
the  anterior  or  superior  nu- 
cleus of  the  facial,  which  will 
be  described  presently  (Fig. 
454,  ME). 

It  is  directed  immediately 
forward,  leaves  the  pons 
Varolii  in  lying  close  to  the 
inner  side  of  the  superior 
maxillary  nerve,  and  traverses 
the  foramen  lacerum  orbitale 
— which  already  lodges  the 
ophthalmic  branch  of  the 
fifth  pair  and  the  common 
oculo-motor  nerve — to  pierce 
the  bottom  of  the  orbit.  It 
is  entirely  expended  in  the 
external  rectus  (or  abductor) 
muscle  of  the  eye,  after  giving 
off  a  small  ramuscule  to  the 
external  portion  of  the  re- 
tractor muscle. 


DIAGRAM  OF   A   SECTION   OF   THE    MEDULLA   OBLONGATA   AND 
PONS   VAROLII   OF   MAN,    AT   THEIR   JUNCTION. 

PP,  Pyramids ;  Pr,  Pr,  transverse  fibres  of  the  pons  Varolii 
(between  the  various  layers  of  these  fibres  are  irregular 
strata  of  masses  of  grey  substance) ;  ME,  ME,  roots  of  the 
external  motores  oculorum  ;  M,  nucleus  common  to  the 
external  motores  oculorum  and  facial  nerve;  FT,  fasciculus 
teres  (vertical  portion  of  the  genu  facialis) ;  Fi,  inferior 
nucleus  of  the  facial,  in  which  arise  the  radicles  that 
form  the  fasciculus  teres;  GP,  gelatinous  substance  of 
Rolando  (head  of  the  posterior  cornu);  T,  ascending  or 
sensitive  root  of  the  trigeminus;  A'C,  grey  substance  on 
the  floor  of  the  fourth  ventricle  (nucleus  of  the  auditory 
nerve);  AG,  auditory  nerve;  e,  external  root  of  ditto; 
»,  internal  root  of  ditto  ;  xx,  raphe ;  GR,  restiform  body. 


7.  Seventh  Pair  (Portio  Dura),  or  Facial  Nerves  (Figs.  453,  454). 

The  facial  is  a  nerve  exclusively  motor  at  its  origin,^  but  it  becomes  mixed, 
during  its  course,  by  the  addition  of  several  sensitive  branches. 

Origin. — It  emanates  from  the  medulla  oblongata,  immediately  behind  the 
pons  Varolii,  and  appears  to  originate  at  the  external  extremity  of  the  transverse 
band  that  margins  the  posterior  border  of  that  protuberance.  But  if  we  attempt 
to  trace  its  origin  in  the  substance  of  the  medulla  oblongata,  we  see  the  single 
fasciculus  it  constitutes,  at  its  point  of  emergence,  descend  into  the  groove 
between  the  pons  Varolii  and  the  above-mentioned  band  ;  it  then  traverses 
nearly  the  whole  thickness  of  the  medulla,  passing  between  the  lateral  cord  or 
•  See  hereafter  the  description  of  the  great  petrosal  nerve,  for  an  account  of  the  constitution 
of  the  facial  nerve. 


826  THE  NERVES. 

column,  and  that  portion  of  the  restiform  body  which  is  continuous  with  the 
large  root  of  the  fifth  pair.  Arrived  near  the  floor  of  the  foui'th  ventricle,  the 
facial  nerve  separates  into  two  fasciculi.  The  less  important  goes  to  a  nucleus 
confounded  with  that  of  the  external  motores  oculorum  ;  the  other  passes  back- 
wards, and  forms  a  prominence  (fasciculus  teres)  on  the  floor  of  the  fourth 
ventricle  ;  then  it  is  suddenly  inflected  outwards  and  forwards,  forming  a  bend 
(the  geniculate  ganglion,  genu  facialis  (Fig.  452,  TT)  described  by  Deiters, 
Vulpian,  etc.,  and  terminates  in  a  nucleus  {posterior  or  inferior  nucleus)  situated 
in  the  lateral  parts  of  the  medulla  oblongata,  on  the  prolongation  of  the  inferior 
cornua  of  the  spinal  cord  (Fig.  452,  Fi).  The  cells  of  the  nucleus  are  multi- 
polar, pigmented,  and  larger  than  those  of  the  anterior  nucleus.  In  the  Cat, 
the  principal  fasciculus  has  no  bend  or  genu. 

Course. — Scarcely  has  the  facial  nerve  left  the  medulla  oblongata,  than  it  is 
directed  outwards,  to  pass  into  the  internal  auditory  meatus,  along  with  the 
auditory  nerve,  which  lies  in  contact  with  it  behind.  It  afterwards  enters  the 
aqueduct  of  Fallopius,  courses  along  it,  and  follows  its  inflections,  which  results 
in  its  forming  a  bend  forward  at  a  short  distance  from  the  internal  opening  of 
the  canal,  and  a  curve  with  concavity  anterior,  on  its  passage  behind  the  cavity 
of  the  tympanum.  On  leaving  the  aqueductus  Fallopii  by  the  stylo-mastoid 
foramen,  it  is  hidden  beneath  the  deep  face  of  the  parotid  gland,  and  continues 
to  be  inflected  forward — passing  between  that  gland  and  the  guttural  pouch — and 
reaches  the  posterior  border  of  the  inferior  maxilla,  where  it  issues  from  beneath 
the  anterior  margin  of  the  parotid  to  become  superficial  and  place  itself  on  the 
masseter  muscle,  immediately  beneath  the  temporo-maxillary  articulation.  There 
it  terminates  in  two  or  three  branches,  which  anastomose  with  those  of  the  super- 
ficial temporal  nerve  from  the  fifth  pair,  thus  forming  the  facial  or  subzygomatic 
plexus  {pes  anserinus)  (Fig.  168). 

Distribution. — a.  In  its  interosseous  course,  the  facial  nerve  successively 
furnishes — 

1.  The,  great  superficial  petrosal  nerve  {nervus  petrosus  superficialis  major). 

2.  The  small  superficial  petrosal  nerve  {nervus  petrosus  superficialis  minor). 

3.  The  filament  of  the  stapedius  muscle  {tympanic  branch). 

4.  The  chorda  tympani. 

It  communicates,  besides,  with  the  pneumogastric  nerve,  by  means  of  a 
voluminous  filament  described  as —  \ 

5.  The  anastomotic  branch  of  the  pneumogastric. 

b.  The  branches  it  emits  on  its  course  beneath  the  parotid  gland  arise  either 
from  its  superior  or  inferior  border  ;  they  are — 

6.  The  occipito-styloid  nerve. 

7.  The  stylo-hyoid  nerve. 

8.  The  digastric  nerve. 

9.  The  cervical  ramuscule. 

10.  Filaments  to  the  guttural  pouch  and  parotid  gland. 
The  superior  branches  comprise  : — 

11.  The  posterior  auricular  nerve. 

12.  The  middle  auricular  nerve. 

13.  The  anterior  auricular  nerve.^ 

■  It  Is  necessary  to  add  to  these  branches,  those  which  go  to  the  parotid  gland,  the 
stimulation  of  which  excites  its  secretion.  Moussu  believes  at  present,  that  these  excito 
secretory  branches  do  not  really  come  from  the  seventh,  but  from  the  ninth  pair. 


TEE  CRANIAL   OR  ENCEPHALIC  NERVES.  827 

c.  To  this  collection  of  collateral  ramuscules  are  added  the  terminal  branches, 
formed  by  their  anastomoses  with  the  superficial  temporal  nerve — 

14.  The  subzf/gomafic  plexus. 

A.  CoLLATBEAL  BRANCHES. — 1.  Great  Superficial  Petrosal  Nerve. — 
This  is  a  very  remarkable  ramuscule,  which  is  detached  from  the  bend  of  the 
facial  nerve  to  proceed  to  Meckel's  ganglion.  The  importance  of  the  peculiarities 
attaching  to  the  study  of  this  nerve  requires  us  to  call  special  attention  to  its 
origin,  course,  and  termination  ;  though  the  details  into  which  we  are  about  to 
enter  may  be  omitted  by  the  student. 

Origin. — Ganglion  geniculare. — The  manner  in  which  the  great  superficial 
petrosal  nerve  comports  itself  at  its  origin  is  yet  an  obscure  and  disputed  subject, 
on  which,  however,  light  is  beginning  to  be  thrown.  The  following  is  the  most 
general  opinion  :  This  nerve  arises  from  a  small  grey  enlargement,  the  geniculate 
ganglion  (or  intumescentia  gangliformis),  placed  on  the  course  of  the  facial  nerve, 
at  the  summit  of  the  angle  which  that  trunk  describes  after  its  entrance  into  the 
aqueduct  of  Fallopius.  The  presence  of  this  small  ganglion  on  the  seventh 
pair  should  assimilate  the  facial  to  a  mixed  nerve,  the  sensitive  root  of  which 
would  be  represented  by  the  -portio  intermedia  of  Wrisherg — a  thin  filament  com- 
prised between  the  seventh  and  eighth  pairs,  and  which  emanates  directly  from 
the  medulla  oblongata  to  pass  into  the  posterior  part  of  the  ganglion  geniculare. 

We  have  constantly  found  this  ganglion  in  the  domesticated  animals.  There 
exists,  in  fact,  on  this  angle  or  elbow  of  the  facial  nerve,  a  very  slight,  grey, 
conical  prominence,  composed  of  ganglionic  cells  which  a  microscopical  examina- 
tion readily  reveals,  and  giving  origin  on  its  apex  to  the  great  superficial  petrous 
nerve.  This  prominence,  which,  we  repeat,  is  very  small,  forms  part  of  the  facial 
nerve,  on  which  it  only  presents  a  kind  of  swelling.  We  have  never  seen  the 
sharp  and  precise  limitation  of  its  base  that  is  figured  in  the  majority  of  icono- 
graphies of  human  anatomy. 

On  the  other  hand,  when,  on  portions  steeped  for  several  weeks  in  water 
acidulated  by  nitric  acid,  we  have  studied  the  constitution  of  the  great  petrosal 
nerve,  even  at  its  origin,  we  have  found  it  formed  of  two  fasciculi  very  easily 
separated — one  internal,  the  other  external.  The  latter  alone  is  continuous  with 
the  geniculated  ganglion;  the  other^ traverses  the  facial  nerve  from  before  to 
behind,  then  it  is  suddenly  inflected  inwards  to  ascend  to  the  origin  of  the  nerve, 
and  mix  with  its  fibres.  But  this  fasciculus  very  often  maintains  its  independence 
as  far  as  the  medulla  oblongata,  into  which  its  fibres  penetrate  separately  ;  they 
then  appear  as  a  small  particular  trunk  beside  that  of  the  principal  nerve,  and 
comprised  between  it  and  the  auditory  nerve.  The  great  petrosal  nerve  does  not, 
therefore,  proceed  exclusively  from  the  ganglion  geniculare,  as  considerable  por- 
tions of  its  fibres — entirely  destitute  of  ganglionic  cells — ^emerge  directly  from  the 
facial  nerve.  With  regard  to  the  external  fasciculus,  the  separation  of  its  fibres  by 
the  action  of  the  acid  shows  very  plainly  that  the  grey  substance  of  the  ganglion 
is  found  almost  exclusively  on  their  track  ;  and  if  we  trace  these  fibres — like 
those  of  the  preceding  fasciculus — into  the  substance  of  the  facial  nerve,  we  shall 
find  that,  instead  of  proceeding  towards  its  origin,  they  appear  to  be  directed  to 
its  termination — a  remarkable  circumstance,  which  we  believe  may  be  explained 
by  admitting  that  they  come  from  the  anastomosing  branch  of  the  pneumogastric 
nerve,  of  which  we  will  speak  hereafter. 

From  this  arrangement,  it  results  that  the  great  petrosal  nerve  arises  from 
the  facial  by  two  real,  though   intimately  connected,  roots  :   the  internal  is 


828  THE  NERVES. 

evidently  motor  ;  the  external  possesses  the  ganglionic  cells  of  a  sensitive  root ; 
and  the  trunk  they  both  form  may  be  regarded  as  a  mixed  nerve. 

As  will  be  observed,  our  view  of  the  ganglion  geniculare  differe  from  the 
general  opinion  held  with  regard  to  it,  inasmuch  as  we  make  it  belong  exclusively 
to  the  great  petrosal  nerve,  and  not  to  the  whole  of  the  facial  fasciculi.  On  the 
other  hand,  the  portio  intermedia  of  Wrisberg  is  not,  in  our  opinion,  the  sensitive 
root  of  the  facial,  the  fibres  of  which  we  only  look  upon  as  motor  ;  it  is  not  even 
that  of  the  great  superficial  petrosal  nerve,  of  which  it  might,  at  the  most,  be  con- 
sidered as  only  an  accessory  filament.  In  the  Horse,  this  ramuscule  is  extremely 
attenuated,  and  can  scarcely,  if  at  all,  be  distinguished  at  its  origin  from  the 
filaments  of  the  lateral  root  of  the  auditory  nerve  ;  it  is  seen  to  enter  the  aqueduct 
of  Fallopius,  and  divide  on  the  bend  (or  gangliform  enlargement)  of  the  facial 
nerve  into  several  gradually  diminishing  filaments,  which  are  confounded  with 
the  proper  fibres  of  this  nerve,  or  the  ganglion  geniculare.  What  a  difl'erence 
there  is  between  this  arrangement,  and  that  of  the  real  sensitive  roots  opposite 
the  ganglia  placed  on  their  track  ! 

The  opinion  which  regards  the  nerve  of  "Wrisberg  as  the  sensitive  root  of  the 
facial  has,  we  beheve,  been  more  particularly  accredited  by  the  apparent  impos- 
sibility of  otherwise  accounting  for  the  sensibility  this  nerve  possesses,  even  at 
its  exit  fi'om  the  stylo-mastoid  foramen — that  is,  before  contracting  any  anasto- 
mosis with  the  fifth  pair  ;  but  this  sensibility  belongs  exclusively  to  the  fibres  of 
the  communicating  branch  sent  by  the  pneumogastric  nerve,  and  not  to  the 
fasciculi  of  the  facial,  as  is  proved  by  stimulating  the  latter  outside  the  aqueduct 
of  Fallopius,  after  destroying  the  pneumogastric  at  its  origin.  If  it  is  sought  to 
regard  the  intermediate  nerve  absolutely  as  a  branch  distinct  from  the  original 
filaments  of  the  auditoiy,  and  if  it  be  determined  to  make  it  a  sensitive  nerve, 
then  it  must  at  least  be  admitted  that  it  does  not  caiTy  its  sensibility  beyond 
the  stylo-mastoid  foramen,  and  that  all  its  filaments  disappear  in  the  ramuscules 
furnished  by  the  facial  in  its  interosseous  coui-se.  Otherwise,  it  is  known  that 
Longet  considers  this  nerve  as  forming  the  small  superficial  petrosal  branch  and 
the  nervous  filament  of  the  stapedius  muscle  ;  but  he  makes  it  a  motor  branch, 
destined  to  supply  the  muscles  of  the  middle  ear.  His  idea  is  very  ingenious, 
and  would  assuredly  be  feasible  if  it  werf  possible  to  follow  the  intermediate 
nerve  from  its  origin  to  the  lateral  column  of  the  medulla  oblongata ;  but, 
unfortunately,  this  is  not  the  case,  as  the  small  ramuscule  only  appears  to  be 
an  offshoot  of  the  fibres  proper  to  the  auditory  nerve. 

To  sum  up,  the  great  superficial  petrosal  nerve  proceeds  from  the  facial  by 
two  roots — one  motor,  the  other  sensitive — assimilable,  to  a  certain  point,  to  the 
roots  of  the  spinal  nerves.  The  first  is  furnished  by  the  filaments  of  the  seventh 
pair  ;  while  the  second  probably  comes  from  the  pneumogastric  nerve,  and  has 
annexed  to  it  on  its  course  the  ganglion  geniculare.  The  nerve  of  Wrisberg 
perhaps  concurs  in  the  formation  of  this  ganglion,  but  it  is  certainly  not  its 
principal  source.  We  ought  to  add,  that  a  study  of  microscopical  sections  of  the 
isthmus  has  caused  Mathias  Duval  to  regard  this  nerve  as  an  en-atic  portion  of 
the  glosso-pharyngeal ;  and  Pierret  has  assimilated  it  to  the  vaso-motor  filaments 
which  leave  the  lateral  column  of  the  spinal  cord,  to  form  the  rami  communicantes 
of  the  great  sympathetic,  while  the  nucleus  from  which  the  branch  proceeds 
constitutes  the  anterior  extremity  of  this  column.  A  good  deal  of  obscurity 
still  prevails  with  regard  to  the  intermediate  nerve,  and  Sapolini  has  proposed 
to  make  it  a  thirteenth  cranial  nerve. 


THE  CRANIAL   OR  ENCEPHALIC  NERVES.  829 

Course  and  Termination. — The  great  petrosal  nerve,  after  being  detached  from 
the  facial,  and  forming  with  it  an  obtuse  angle  opening  outwards,  enters  the 
aqueduct  of  Fallopius — a  small  passage  running  from  behind  forward,  in  the 
substance  of  the  petrous  bone,  above  the  fenestra  rotunda  and  cochlea.  Arriving 
at  the  interior  of  the  cavernous  sinus — which  it  passes  through,  immersed  in  the 
blood  that  sinus  contains — it  receives  a  branch  from  the  ganglionic  plexus  there, 
is  lodged  in  the  Vidian  fissure,  then  in  the  Vidian  canal,  and  in  this  manner 
gains  the  orbital  hiatus,  where  it  separates  into  several  branches — most  frequently 
two — which  join  the  posterior  part  of  Meckel's  ganglion.  It  constitutes  the 
motor  root  and  sympathetic  filament  of  that  ganghon. 

2.  Small  Superficial  Petrosal  Nerve. — A  very  thin  filament  detached 
from  the  facial  to  the  outside  of  the  preceding,  and  likewise  traversing  the 
petrous  bone  from  behind  to  before,  to  enter  the  otic  ganghon,  as  its  motor  root. 

3.  Filament  of  the  Stapedius  Muscle  (Tympanic). — The  facial  nerve, 
in  its  passage  above  and  in  front  of  the  stapedius  muscle,  closely  adheres  to  it, 
and  gives  it  one,  perhaps  several,  extremely  short  filaments. 

4.  Chorda  Tympani  (Fig.  459,  6). — This  filament — also  named  the  tympano- 
lingual  nerve — arises  at  a  very  obtuse  angle  from  the  facial,  near  the  external 
orifice  of  the  aqueductus  Fallopii ;  but  in  reality  it  comes  from  the  trigeminus. 
It  penetrates  the  cavity  of  the  tympanum  by  a  particular  opening,  courses  from 
its  posterior  to  its  anterior  wall  in  describing  a  curve  downwards,  and  passes 
among  the  chain  of  auditory  bones,  between  the  handle  of  the  malleus  and  long 
branch  of  the  incus.  Escaping  from  the  middle  ear  by  a  canal  {fissura  Glaseri) 
on  the  hmits  of  the  mastoid  and  petrous  portions  of  the  temporal  bone,  it  proceeds 
foi-wards  and  downwards,  and  finally  joins  the  gustatory  nerve  after  a  short  course 
beneath  the  external  pterygoid  muscle,  outside  the  guttural  pouch. 

It  is  distributed  with  the  lingual  in  the  mucous  membrane  of  the  anterior 
portion  of  the  tongue,  and  even,  according  to  Vulpian,  in  the  muscles  of  that 
organ  ;  as  stimulation  of  the  chorda  tympana  causes  movement  of  the  tongue 
several  days  after  division  of  the  great  hypo-glossal  nerve.  That  physiologist 
attributes  to  it  all  the  phenomena  that  Claude  Bernard  had  observed  in  the 
submaxillary  gland,  after  stimulation  of  the  ganglion  of  that  name — vaso-dilating 
and  excito-secretory  effects.  Consequently,  the  choroda  tympanum  should  throw 
a  certain  number  of  fibres  in  that  ganglion,  and  from  it  into  the  gland. 

5.  Anastomosing  Branch  of  the  Pneumogastric  Nerve. — {See  the 
description  of  the  tenth  pair.) 

6.  Occipito- Styloid  Nerve  (Fig.  453,  3). 

7.  Stylo-hyoid  Nerve. 

8.  Digastric  Nerve  (Fig.  453,  4). — These  three  spring  from  a  common 
fasciculus  at  the  stylo-mastoid  foramen,  and  ramify  in  their  respective  muscles, 
after  a  certain  course  beneath  the  parotid  gland. 

9.  Cervical  Branch  (Figs.  453,  6). — This  nerve  has  its  origin  almost  in 
the  middle  of  the  subparotideal  portion  of  the  facial,  near  a  particular  loop 
thrown  by  that  nerve  around  the  posterior  auricular  artery,  and  often  from  this 
loop  itself. 

It  afterwards  traverses  the  parotid  gland  from  within  to  without,  and  above 
to  below,  to  descend  at  first  on  its  external  face — beneath  the  parotido-auricularis 
muscle — then  into  the  jugular  channel,  where  it  is  lodged  below  the  deep  face  or 
in  the  substance  of  the  panniculus  muscle,  which  receives  its  terminal  divisions 
near  the  anterior  appendix  of  the  sternum. 
55 


830  THE  NERVES. 

In  its  course  this  nerve  communicates  with  the  inferior  branches  of  the 
second,  third,  fourth,  fifth,  and  sixth  cervical  pairs  by  branches  from  them  ;  it 
sends  numerous  collateral  filaments  into  the  texture  of  the  panniculus. 

10.  Filaments  of  the  Guttural  Pouch  and  Parotid  Gland. — Re- 
markable for  their  number  and  tenuity,  these  filaments  do  not  otherwise  deserve 
particular  mention. 

11.  Posterior  Auricular  Nerve  (Fig.  453,  2). — It  commences  at  the 
stylo-mastoid  foramen,  is  directed  upwards  beneath  the  parotid  gland,  accom- 
panying the  posterior  auricular  artery,  and  is  distributed  to  the  posterior  muscles 
of  the  external  ear.  It  sometimes  has  at  its  origin  a  loop  analogous  to  that 
embracing  the  posterior  auricular  artery. 

12.  Middle  Auricular  Nerve. — Most  frequently  this  arise  from  the  same 
point  as  the  preceding  nerve — it  might  be  said  in  common  with  it — ascends 
towards  the  base  of  the  concha  in  traversing  the  parotid  gland,  and  pierces  the 
cartilage  to  supply  the  interconchal  integument,  and  the  muscular  fibres  which 
cover  its  adherent  face  in  some  parts. 

13.  Anterior  Auricular  Nerve  (Fig.  453,  5). — This  is  the  largest  of  the 
three  auricular  nerves.  After  being  detached  from  the  facial  nerve,  opposite 
the  cervical  branch,  and  after  ascending  across  the  parotideal  tissue,  it  gains 
the  external  face  of  the  zygomatic  process,  where  it  meets  the  superficial 
divisions  of  the  lachrymal  nerve  ;  it  continues  forward  beneath  the  external 
pariefeo-auricular  muscle,  reaches  the  base  of  the  orbital  process  at  the  supra- 
orbital foramen,  there  crossing  the  terminal  branches  of  the  nerve  of  that  name  ; 
it  then  descends  vertically  within  the  orbit  to  below  the  nasal  angle  of  the  eye, 
where  it  mixes  with  the  superficial  divisions  of  the  palpebro-nasal  nerve,  and 
finally  terminates  on  the  face  of  the  lachrymalis  and  levator  labii  superioris 
alaequi  nasi  muscles. 

In  its  progress,  it  gives  off  numerous  ramuscules  to  the  anterior  muscles  of 
the  ear,  the  levator  palpebrse  superioris,  and  the  orbicularis  of  the  eyelids. 

This  nerve  is  remarkable  for  the  relations  it  maintains  with  the  terminal 
ramuscules  of  the  three  branches  of  the  ophthalmic  nerve,  or  fifth  pair. 
Although  there  do  not  exist  any  real  anastomoses  between  it  and  these  various 
branches,  it  is  customary  to  designate  the  reticular  mass  they  form  in  front  of 
the  ear  and  on  the  side  of  the  face,  as  the  anterior  auricular  plexus. 

Terminal  Branches  of  the  Facial  Nerve,  or  Subzygomatic  Plexus 
(Fig.  168,  11,  12). — The  facial  nerve,  as  we  have  seen,  terminates  in  several 
branches — usually  two,  on  arriving  beneath  the  temporo-maxillary  articulation, 
where  they  join  the  superficial  temporal  nerve.  After  becoming  sensori-motor, 
they  are  continued  on  the  external  face  of  the  masseter,  covered  by  the  panni- 
culus muscle  of  the  head,  to  which  they  give  some  ramuscules,  and  are  united 
to  each  other  by  anastomosing  branches  of  variable  disposition.  It  is  always 
observed,  with  regard  to  this  arrangement,  that  the  branches  of  the  subzygo- 
matic  plexus,  on  arriving  near  the  anterior  border  of  the  masseter,  are  divided 
into  a  series  of  divergent  ramuscules  which  pass  to  the  surface  of  the  vascular  or 
glandular  canals  situated  in  front  of  the  masseter,  to  enter  the  tissues  of  the 
lips,  cheeks,  and  nostrils.^ 

'  The  following  is  an  extract  from  a  memoir  by  Arloing  and  Tripier.  "  On  the  Conditions 
of  Persistency  of  Sensibility  in  the  Peripheral  Extremity  of  Cut  Nerves "  (Archives  de 
Physiologie,  1876),  relating  the  differences  observed  in  the  arrangement  of  the  subzygomatic 


TEE  CBANIAL   OR  ENCEPHALIC  NERVES.  831 

Among:  these  ramuscules,  the  superior  is  remarkable  for  its  great  volume ; 
it  passes  beneath  the  zygomaticns  muscle,  lies  close  to  the  inferior  border  of 
the  dilator  naris  lateralis,  beside  the  superior  coronary  artery,  and  afterwards 
runs  below  that  muscle,  where  it  joins  the  terminal  ramuscules  of  the  superior 
maxillary  nerve,  with  which  it  is  distributed  to  the  textures  of  the  upper  lip  and 
alje  of  the  nose  (Fig.  453,  7')- 

A  second  ramuscule — the  inferior,  smaller  than  the  preceding — follows  the 
inner  aspect  of  the  depressor  labii  inferioris  muscle,  to  mix  by  its  anterior 
extremity  with  the  terminal  fasciculus  of  the  inferior  maxillary  nerve,  and 
ramify— with  the  proper  filaments  of  that  fasciculus — in  the  tissue  of  the  lower 
lip. 

Between  these  two  principal  branches  is  a  series  of  smaller  ramifications 
destined  to  the  buccinator  muscle.  Among  these  are  some  which  become 
inflected  on  the  inner  face  of  the  masseter,  and  reach  the  deep  portion  of  the 
buccinator,  where  they  anastomose  with  the  filaments  of  the  buccal  nerve. 
Other  ranuiscules— situated  below  the  principal  inferior  branch— are  expended 
in  the  panniculus  on  the  face  ;  one  of  them,  after  bending  round  the  lower 
border  of  the  inferior  maxilla,  reaches  the  submaxillary  space. 

Functions  of  the  Facial  Nerve. — This  nerve  excites  contraction  of  the 
muscles  of  the  middle  ear,  external  ear,  the  cheeks,  lips,  nostrils,  orbicularis  of 
the  eyelids,  and  the  cervico-facial  panniculus.  By  its  great  superficial  petrosal 
filament,  it  influences  the  movements  of  the  muscles  of  the  soft  palate,  and  it  is 
admitted — as  already  noticed  when  speaking  of  the  gustatory  nerve — that  its 
tympano-lingual  ramuscule  acts  on  the  submucous  muscular  layer  of  the  tongue. 
The  facial  nerve,  also,  without  doubt,  exercises  its  influence  on  the  parotid 
gland. 

It  serves  as  a  medium  for  the  passage  for  vaso-motor  and  excito-secretory 
filaments. 

It  is  to  be  remarked  that  the  facial  nerve  has  no  influence  over  the  masseter 

plexus  of  Soliptids.     It  is  useful  to  know  these  differences  in  accounting  for  the  phenomena 
that  accompany  accidental  or  experimental  lesions  in  this  plexus. 

As  a  general  rule,  the  facial  nerve  divides  into  two  branches  close  to  the  parotid  gland. 
The  auriculo-temporal  nerve  divides  into  three  unequal  branches  when  it  reaches  the  max- 
illary condyle ;  the  upper  branch — slender,  single,  or  bifurcated — follows  the  superficial 
temporal  artery  and  disappears  in  the  skin  of  this  region,  or  rejoins  in  part  the  temporo-facial 
plexus.  The  other  branches  lie  close  beside  the  two  branches  of  the  facial  nerve — the  two 
nerves  being  confounded  with  each  other  as  they  proceed  to  their  terminations.  This  type, 
■which  we  consider  very  rare,  is  modified  in  various  Witys : — 

1.  The  sensitive  and  motor  filaments,  instead  of  being  confounded  suddenly  at  the  anterior 
border  of  the  parotid  gland,  may  proceed  side  by  side.  This  separation  is  generally  less 
marked  in  the  superior  temporo-facial  branch  ;  when  it  exists  in  the  inferior  branch,  the  motor 
filament  is  situated  between  the  masseter  and  the  panniculus,  the  sensitive  filament  between 
the  latter  and  the  skin. 

2.  Separation  of  the  sensitive  and  motor  portions  is  complete.  The  inferior  facial  branch 
especially  may  proceed  alone  to  the  lips;  the  sensitive  branch  for  it  follows  at  first  the 
superior  branch  of  the  plexus,  and  only  leaves  it  about  the  middle  of  the  masseter,  to  pass  on 
the  cheek  and  rejoin  its  satellite  motor  filament  in  the  lower  lip  only.  In  this  case,  the 
inferior  branch  has  only  filaments  from  the  facial. 

3.  Instead  of  a  prompt  separation  between  the  branches  of  the  temporo-auricular  and  the 
facial  nerve,  tliere  is  sometimes  observed  fusion  of  the  four  branches,  whicli  may  be  pro- 
longed some  distance  beyond  the  parotid  gland.  We  have  seen  dispositions  of  this  kind,  in 
which  the  inferior  branch  (tiien  always  mixed)  was  detached  from  the  fasciculus,  at  the 
level  of  the  eye,  in  forming  a  very  acute  angle. 

Sometimes  marked  differences  are  observed  in  the  two  plexuses  in  the  same  animal. 


832  THE  NERVES. 

muscle  :  notwithstanding  their  intimate  relations,  it  does  not  detach  the  smallest 
filament  to  it. 

Its  anastomoses  with  the  various  branches  of  the  trigeminus  and  pneumo- 
gastric  nerves,  endow  some  of  its  branches  with  great  sensibility. 

8.  Eighth  Paie,  or  Auditory  Nerves  (Figs.  424,  455,  456). 

This  is  the  nerve  of  hearing  ;  it  has  a  very  simple  disposition,  which  we  will 
sum  up  in  a  few  words. 

Origin. — The  auditory  nerve  {portio  mollis)  proceeds  from  the  medulla 
oblongata  by  two  roots — an  anterior  or  lateral,  and  a  posterior.  The  latter 
(Fig.  425,  20)  commences  on  the  floor  of  the  fourth  ventricle  by  some  con- 
vergent strise  (limce  transverse^  stricB  medullares),  as  is  admitted  in  the  majority 
of  treatises  on  human  anatomy — though  we  have  never  been  able  to  discover 
these  strise  in  the  domesticated  animals  ;  it  is  afterwards  directed  outwards, 
round  the  posterior  cerebellar  peduncle,  and  unites  with  the  anterior  root  on 
the  side  of  the  medulla  oblongata.  The  latter  root  (Fig.  456,  g),  consists  of 
a  single  fasciculus  joined  with  that  of  the  facial,  and  escapes  from  between  the 
fibres  of  the  restiform  body.  The  nucleus  of  the  auditory  nerve  has  been  dis- 
covered by  Schroeder  Van  der  Kolk,  a  little  below  that  of  the  facial  nerve. 

Course  and  Termination. — These  two  roots  immediately  unite  into  a  single 
soft  cord,  situated  behind  that  of  the  seventh  pair,  with  which  it  is  directed 
outwards  to  reach  the  internal  auditory  meatus.  There  it  divides  into  two 
branches — an  anterior  and  posterior — the  fasciculi  of  which  traverse  the  fora- 
mina at  the  bottom  of  the  meatus  :  the  former  to  gain  the  axis  of  the  cochlea 
(the  cochlear  branch),  and  the  latter  the  semicircular  canals  {vestibular  branch). 
The  description  of  these  two  branches  will  be  deferred  until  we  come  to  study 
the  sense  of  hearing. 

9.  Ninth  Pair,  or  Glosso-Pharyngeal  Nerves  (Figs.  456,  3  ;  459,  10). 

The  glosso-pharjTigeal  is  a  mixed  nerve,  which  conveys  general  sensation, 
with  gustative  sensibility,  to  the  posterior  third  of  the  tongue,  and  excites 
contraction  of  the  pharyngeal  muscles. 

Origin. — This  nerve  originates  on  the  side  of  the  medulla  oblongata,  behind 
the  eighth  pair,  by  eight  or  ten  fine  roots,  some  of  which  are  implanted  in  the 
restiform  body  ;  while  the  others — the  smallest  number— escape,  like  the  fila- 
ments of  the  facial  nerve,  from  the  interstice  between  that  body  and  the  lateral 
column  of  the  medulla  oblongata.^  The  roots  of  this  nerve  pass  into  two 
diflPerent  nuclei.  The  sensitive  fibres  reach  a  nucleus  (Fig.  455,  pn)  situated  near 
the  floor  of  the  fourth  ventricle,  in  the  prolongation  of  the  superior  cornu  of  the 
medullary  axis ;  while  the  motor  fibres  enter  another  nucleus  (Fig.  455,  s) 
belonging  also  to  the  hypo-glossal,  and  which  lies  in  the  direction  of  the  inferior 
cornua  of  the  spinal  cord.     At  their  exit  from  the  medulla  oblongata,  these 

'  This  disposition— which  is  readily  exposed  in  the  Horse— appears  to  us  sufficient  to  remove 
all  the  doubts  existing  iu  the  minds  of  a  large  number  of  anatomists,  as  to  tiie  nature  of  the 
glosso-pharyngeal  nerve.  It  evidently  possesses  at  its  origin,  as  motor  filaments,  those  arising 
from  the  same  part  as  the  facial  nerve,  and  as  sensitive  filaments  those  from  the  restiform 
body.  Besides,  we  may  object  to  the  opinion  whicii  would  also  attribute  the  motor  property 
of  the  glosso-pharyngeal  nerve  to  the  anastomosing  branches  passing  between  it  and  the 
seventh  pair,  on  the  ground  that  tliese  anastomoses  are  far  from  being  constant,  and  that  in 
Bome  species  they  are  always  totally  absent. 


THE  CRANIAL    OR  ENCEPHALIC  NERVES. 


roots  soon  unite  in  a  single  cord,  which  issues  from  the  cranium  by  a  particular 
orifice  in  the  posterior  part  of  the  foramen  lacerum,  and  at  this  point  it  exhibits 
a  grey  oval-shaped  enlargement — the  ganglion  petrosum  or  ganglion  of  Andersch, 
in  which  it  is  somewhat  difficult  to  distinguish  the  motor  filaments  of  the  nerve 
from  those  which  arise  between  the  lateral  and  superior  columns  of  the  medulla 
(Fig.  456,  2). 

Course  a?id  Termination. — Scarcely  has  the  glosso-pharyngeal  nerve  escaped 
from   the   cranium,  than   it  descends,  in   describing   a   curve  with   concavity 
forward,  behind  the  large  branch  of  the  os  hyoides,  included  at  first  between 
a  fold  of  the  guttural  pouch,  then  between  the  latter  and  the  internal  pterygoid 
muscle.     Lying  beside  the  ex- 
ternal carotid    artery   in    the  F'S-  "^55. 
latter   part   of    its    course,   it                                 x'-*"''**\  ^^^  ^ 
passes  with  it  along  the  pos-                      "^^^ ^      ^      \f      ^    V^' 
terior  border  of  the  great  cornu                    ^/^Vpys>^-^^<lX^->^^^^7^^^^^ 
of  the  hyoid  bone,  and  gains 
the  base  of   the   tongue  with 
the  lingual  artery,  by  coursing 
beneath  the  hyo-glossus  brevis 
muscle.      The  papillae  on  the 
posterior  portion  of  the  lingual 
mucous  membrane  receive  the 
terminal    ramuscules    of    this 
nerve.    (See  the  Sense  of  Taste. ) 

Collateral  Branches. — On 
its  course  it  furnishes — 

1.  Jacobson's  nerve  {tym- 
fanic  hranch),  a  very  thin  fila- 
ment springing  from  An- 
dersch's  ganghon,  proceeding 
upwards,  and  entering  a  par- 
ticular foramen  in  the  petrous 
portion  of  the  temporal  bone,  to 
be  distributed  more  especially 
to    the    tympanum ;    sending 

also  to  the  superficial  petrosal  nerves  two  branches,  which  are  designated  the 
great  and  deep  small  petrosal  nerves. 

2.  Filaments  of  communication  with  the  superior  cervical  ganglion,  two  or  three 
in  number,  though  sometimes  replaced  by  a  single  ramuscule. 

3.  A  brafich  to  the  carotid  plexus,  which  passes  back  on  the  guttural  pouch 
to  reach  the  terminal  extremity  of  the  common  carotid,  whence  its  filaments 
are  sent,  with  those  of  the  sympathetic  nerve,  either  to  the  external  carotid, 
occipital,  or  even  to  the  common  carotid  artery  itself.  This  branch  communi- 
cates, by  several  anastomoses,  with  the  numerous  sympathetic  branches  which 
pass  from  the  superior  cervical  ganglion  to  the  surface  of  the  guttural  pouch, 
and  which  are  either  expended  in  that  membrane,  or  join  the  posterior  border  of 
the  great  hypoglossal  nerve. 

4.  A  pharyngeal  branch  (Fig.  459,  11),  which  is  generally  detached  close 
to  the  pharyngeal  artery,  and  forms — along  with  the  pharyngeal  filaments  of 
the  pneumogastric  nerve — a  remarkable  intricate  plexus  {^pharyngeal)  on  the 


Aft 


DIAGRAM    OF   A  SECTION  OF    THE   MIDDLE    PORTION  OF   THE 
MEDULLA    OBLONGATA    OF    MAN. 

PP,  Pyramids  ;  CC,  floor  of  the  fourth  ventricle  :  H,  radicular 
fibres  of  the  great  hypoglossal  nerve ;  nh,  classical 
nucleus  of  ditto;  n'h',  accessory  nucleus  of  ditto;  S, 
accessory  (motor)  nucleus  of  the  mixed  nerves ;  pn, 
sensitive  nucleus  of  the  mixed  nerves  (glosso-pharyngeal, 
pneumogastric,  spinal  accessory) ;  nr,  nucleus  of  the 
restiform  bodies;  GP,  gelatinous  substance  of  Rolando 
(head  of  the  posterior  cornu) ;  T,  ascending  root  of  the 
trigeminus  ;  M,  radicular  fibres  of  the  pneumogastric ; 
01,  grey  layer  of  the  olivary  body  ;  R,  internal  juxta- 
olivary  nucleus  ;  T,  external  ditto ;  xx,  raphe. 


834  THE  NERVES. 

upper  wall  of  tne  pharynx,  below  the  guttural  pouch.     This  plexus  receives 
a  filament  from  the  hypoglossal  nerve. 

10.  Tenth  Paie,  Vagus,  or  Pneumogastric  Nerves  (Figs.  452,  455, 

458,  480). 

The  pneumogastric  nerve  is  as  remarkable  for  its  extent,  as  for  the  multi- 
plicity of  physiological  uses  ascribed  to  it. 

It  is  prolonged  beyond  the  stomach,  after  distributing  to  that  viscus,  the 
oesophagus,  pharynx,  lung,  bronchi,  trachea,  and  larynx  a  large  number  of 
filaments  on  which  depend  the  movements,  secretory  functions,  and  purely 
sensory  phenomena  of  which  all  these  organs  are  the  seat. 

Origin. — The  pneumogastric  is  a  fixed  nerve,  and  consequently  arises  from 
two  kinds  of  roots  ;  these  we  will  successively  describe  before  passing  to  its 
distribution,  though  it  must  be  remarked  that  this  subject  has  not  yet  been  fuhy 
determined. 

Sensitive  roots. — These  arise  from  a  nucleus  of  grey  substance  situated  near 
the  floor  of  the  fourth  ventricle,  a  little  behind  the  glosso-pharyngeal  nucleus — 
sensitive  nucleus  of  the  mixed  nerves  (Fig.  455,  pn) — and  in  which  the  fibres  of 
the  antero-lateral  columns  of  the  medulla  oblongata,  or  respiratory  tract  of  Bell, 
appear  to  be  lost.  In  leaving  the  medulla,  they  form  from  four  to  ten  bundles, 
which  describe  a  shght  curve  with  convexity  upwards  ;  the  highest  middle  fibres 
coi-respond  to  the  groove  that  limits,  superiorly,  the  respiratory  fasciculus,  the 
posterior  and  anterior  fibres  bending  downwards  to  the  pyramids — the  second 
more  than  the  first. 

These  roots  proceed  transversely  outwards,  mixed  with  connective  tissue 
and  some  fine  muscular  ramifications,  and  leave  the  cranium  by  one  of  the 
openings  (jugular  foramen)  in  the  posterior  part  of  the  foramen  lacerum, 
uniting  in  their  passage  through  that  aperture  into  a  somewhat  voluminous 
ganglion,  called  in  Man  the  jugular  ganglion  {iqiper  ganglion,  or  ganglion  of  the 
root). 

Motor  roots. — Several  anatomists  and  physiologists  consider  these  as  a  portion 
of  the  accessory  nerve  of  Willis,  and  give  them  the  name  of  internal  or  bulbar 
root  of  the  spinal  nerve.  They  are  situated  a  little  behind  the  preceding,  and 
arise,  in  the  middle  of  the  respiratory  tract,  from  a  mass  of  grey  substance  which 
also  emits  the  motor  fibres  of  the  glosso-pharyngeal  {motor  nucleus  of  mixed  nei'ves 
— Fig.  455,  s)  ;  consequently,  they  are  not  so  elevated  as  the  whole  of  the  sensitive 
fibres.  They  are  separated  from  the  latter  by  a  comparatively  large  vein,  and  are 
distinguished  from  them  by  their  anastomotic  tendency.  Becoming  longer  as 
they  are  more  posterior,  and  frequently  anastomosing  with  each  other,  the  fila- 
ments forming  these  motor  roots  converge,  and  gain  the  posterior  part  of  the 
foramen  lacerum  ;  this  they  pass  through  by  one  or  two  special  openings  to  join 
the  jugular  ganglion,  beneath  and  behind  which  we  find  them  applied.  A  certain 
number  of  the  most  posterior  of  these  filaments  lie  beside  the  medullary  root  of 
the  spinal  accessory  nerve  ;  but  they  are  soon  detached  to  pass  with  the  others  to 
the  jugular  ganglion. 

Jugidar  or  Ehrenritter's  ganglion. — Elongated  from  before  to  behind,  and 
flattened  above  and  below,  the  jugular  ganglion  is  embedded  in  the  cartilaginous 
substance  that  fills  the  foramen  lacerum.  When  it  has  been  macerated  for  some 
time  in  dilute  nitric  acid,  it  may  be  resolved  into  two  portions — one  correspond- 
ing to  the  sensitive,  the  other  to  the  motor  roots.     Some  white  nerve-filamentiS 


THE  CRANIAL   OR  ENCEPHALIC  NERVES  835 

appear  to  pass  to  its  surface  without  becoming  confounded  with  it.  It  is  in 
relation,  in  front,  with  the  ganglion  of  Andersch  ;  behind,  it  crosses  somewhat 
obliquely  the  medullary  root  of  the  spinal  accessory  nerve. 

The  jugular  gangUon  is  also  in  relation  with  the  spinal,  glosso-pharyngeal, 
and  facial  nerve.  It  communicates  with  the  external  root  of  the  spinal  accessory 
nerve  by  the  few  radicular  filaments  indicated  above.  With  the  glosso-pharyn- 
geal it  IS  connected  by  :  1.  An  afferent  filament  coming  from  the  highest  roots 
of  the  ninth  pair,  and  which  meets  it  at  its  antero-internal  angle.  2.  By  an 
efferent  branch  it  sends  to  the  ganglion  of  Andersch.  3.  Lastly,  it  is  united  to 
the  facial  by  a  branch  we  have  named  the  anastomosing  branchy  extending  from 
the  pneumo gastric  to  the  facial  nerve. 

This  anastomotic  branch,  on  leaving  the  jugular  ganglion,  is  somewhat  con- 
siderable in  volume,  and  it  has  appeared  to  us  that,  at  times,  among  its  radicles 
there  were  some  in  direct  continuity  with  the  sensitive  roots  of  the  pneumogastric 
nerve.  This  branch  is  directed  forward,  above  the  ganglion  of  Andersch,  crosses 
Jacobson's  branch,  traverses  the  petrous  temporal  bone,  and  arrives  in  the 
aqueduct  of  Fallopius  ;  here  it  meets  the  facial  nerve,  at  the  point  where  the 
latter  gives  off  the  chorda  tympani.  A  small  number  of  fibres  then  lie  beside  the 
nerve  of  the  seventh  pair  in  ascending  towards  the  origin  of  that  nerve,  where, 
in  our  opinion,  they  constitute  a  large  portion  of  the  great  petrosal  nerve— that 
which  has  at  its  origin  the  ganghon.  Other  fibres  descend,  on  the  contrary,  in 
following  the  proper  fibres  of  the  facial  nerve,  and  are  lost  among  these  ;  but  the 
largest  number  cross  that  nerve  and  continue  their  course  in  the  substance  of 
the  temporalis  muscle,  to  be  chiefly  distributed  to  the  membrane  lining  the 
internal  auditory  canal. 

Course  and  relations. — Beyond  the  jugular  ganglion,  the  trunk  of  the 
pneumogastric  remains  intimately  allied  with  the  spinal  accessory  for  about  f 
of  an  inch  ;  these  two  nerves  then  separate  to  allow  the  great  hypoglossal  nerve 
to  pass  between  them  ;  after  which  the  pneumogastric  nerve  descends  alone 
behind  the  guttural  pouish,  in  proximity  to  the  superior  cervical  ganglion. 

Near  the  origin  of  the  occipital  artery  it  crosses  to  the  inner  side  of  that 
vessel,  and  beyond  this  it  is  joined  in  the  most  intimate  manner  to  the  cervical 
portion  of  the  sympathetic  chain  ;  the  single  cord  resulting  from  this  fusion 
follows  the  common  carotid  artery,  above  which  it  is  situated,  to  near  the  entrance 
of  the  thorax.  The  two  nerves  then  resume  their  reciprocal  independence,  the 
pneumogastric  penetrating  the  thorax  a  little  below  the  sympathetic,  in  passing 
among  the  lymphatic  glands  lying  between  the  two  first  ribs. 

In  this  course,  the  two  pneumogastrics  have  nearly  the  same  relations  ;  though 
there  is  something  special  connected  with  the  left,  which  is  related  to  the 
cesophagus  towards  the  lower  part  of  the  neck. 

Within  the  chest,  however,  these  two  nerves  comport  themselves  a  little 
differently.  The  right  passes  round  the  axillary  artery  very  obliquely,  upwards, 
outwards,  and  backwards  beneath  the  mediastinal  pleura,  to  follow  the  external 
face  of  the  trachea  to  above  the  origin  of  the  bronchi,  where  this  nerve  termi- 
nates. The  left  also  passes  below  the  brachial  trunk  ;  but  instead  of  turning 
round  the  trachea,  it  merely  lies  beside  that  tube,  and  reaches  the  root  of  the 
lung,  after  crossing,  outwardly,  the  origin  of  the  two  aortae. 

When  these  nerves  arrive  above  the  bifurcation  of  the  trachea,  they  terminate 
by  forming  the  bronchial  plexus  and  cesophogeal  nerves — the  latter  being  prolonged 
to  the  stomach  and  the  solar  plexus. 


836  TEE  NERVES. 

Beneath  the  jugular  ganglion,  but  in  the  upper  part  of  the  neck,  the  pneumo- 
gastric  receives  iilaments  from  the  spinal  accessory,  ganglion  of  Andersch,  sympa- 
thetic, hypoglossal,  and  the  two  first  cervical.  These  different  nerves  cross  each 
other  in  a  very  complex  manner  on  the  surface  of  the  guttural  pouch,  the 
pharynx,  and  divisions  of  the  carotids,  and  form  the  guttural,  pharyngeal,  and 
cartoid  plexuses. 

Distribution. — The  branches  furnished  by  the  pneumogastric  on  its  course 


are 


Fig.  456. 


^ 

^^^fi; 

'^*^ 

^^^5^8!!""' 

il- 

(MUGIN    OF   THE   NERVES   ARISING   FROM    THE   MEDULLA    OBLONGATA,  AND   PARTICULARLY   THAT  OF 
THE   PNEUMOGASTRIC,   SPINAL   ACCESSORY,    HYPOGLOSSAL,   AND   GLOSSO-PHARYNGEAL. 

a,  Medulla  oblongata  ;  6,  pyramids  ;  c,  enlargement  simulating  the  olivary  body  ;  c?,  latei'al  posterior 
fissure ;  e,  fissure  limiting,  superiorly,  the  respiratory  tract  of  Ch.  IJell ;  /,  corpus  restiforme ; 
g,  auditory  nerve ;  h,  external  oculo-motor ;  «",  trigeminus  ;  j,  arciform  fibres  of  the  medulla 
oblongata.  1,  Pneumogastric  ;  2,  spinal  accessory,  inner  root ;  3,  glosso-pharyngeal ;  4,  spinal 
accessory,  medullary  column;  5.  inferior,  or  anterior,  root  of  the  great  hypoglossal;  5',  its 
ganglionic  root;  6,  facial  nerve;  7,  jugular  ganglion;  8,  anastomosis  of  the  pneumogastric  with 
the  facial ;  9,  ramuscule  from  the  external  branch  of  the  spinal  accessory  passing  to  the  pneumo- 
gastric. (From  Toussaint's  Thesis  on  the  Anatomie  Compare'e  du  Nerf  Pncumogastrique. 
Lyons:  1869). 


1.  Communicating  filaments  tvith  the  sup&rior  cervical  ganglion^ 

2.  Pharyngeal  branch. 

3.  Superior  laryngeal  nerve. 

4.  Communicating  filaments  ivith  the  infe^'ior  cervical  ganglion. 

5.  Inferior  laryngpal  nerve. 

6.  Cardiac  filaments. 

We  will  pass  in  review  these  collateral  divisions  before  studying  the  terminal 
branches,  which  are  : 


THE  CRANIAL   OR  ENCEPHALIC  NERVES. 


887 


1.  Those  forming  the  bronchial  plexus. 

2.  Those  constituting  the  esophageal  nerves. 

COLLATEEAL    BRANCHES   OF   THE    PnEUMOGASTRIC 

Nerve. — 1.  Filaments  of  the  Inferior  Cervical 
Ganglion. — Always  very  slender,  these  sometimes 
come  from  the  pharyngeal  ramuscule. 

2.  Pharyngeal  Nerve  (Fig.  459, 15). — Originat- 
ing from  the  pneumogastric  nerve  at  the  middle  part 
of  the  superior  cervical  ganglion,  the  pharyngeal  passes 
forwards  and  downwards  on  the  side  of  the  guttural 
pouch,  and  gains  the  upper  face  of  the  pharynx,  where 
it  terminates  in  forming  a  plexus  with  the  pharyngeal 
branch  of  the  ninth  pair.  This  is  a  sensory-branch. 
It  gives  off  a  large  division  that  passes  backwards  to 
the  surface  of  the  middle  and  posterior  constrictor 
muscles,  to  which  it  gives  branches,  and,  throwing  off 
a  filament  to  the  external  laryngeal  nerve,  reaches  the 
commencement  of  the  oesophagus  ;  it  descends  on  the 
outside  of  that  tube,  by  becoming  distributed  in  its 
muscular  tunic.  This  division — which  w^e  have  named 
the  cesopjhageal  branch  of  the  pharyngeal  nerve — may  be 
traced  on  the  oesophagus  to  the  lower  part  of  the  neck, 
and  in  some  subjects  even  into  the  thoracic  cavity. 

3.  Superior  Laryngeal  Nerve  (Fig.  458,  1). — 
More  voluminous  than  the  preceding,  and  arising  a 
little  lower,  this  nerve  follows  an  analogous  course  to 
reach  the  side  of  the  larynx,  where  it  enters  the  aperture 
below  the  appendix  of  the  superior  border  of  the  thyroid 
cartilage,  to  be  almost,  entirely  expended  in  the  laryngeal 
mucous  membrane,  which  it  endows  with  a  very 
exquisite  degree  of  sensibility. 

At  the  inner  face  of  the  thyroid  cartilage,  it  has 
several  branches  that  are  directed  forward,  upward, 
and  backward.  The  first  pass  to  the  mucous  membrane 
at  the  base  of  the  tongue  and  the  two  surfaces  of  the 
epiglottis.  The  second  are  distributed  in  the  lateral 
walls  of  the  pharynx.  Of  the  third,  some  go  to  the 
mucous  membrane  of  the  arytenoid  cartilages  and  that 
of  the  oesophagus  ;  while  others  descend  on  the  thyro- 
arytfenoid  and  lateral  crico-arytgenoid  muscles,  to  unite 
with  the  branches  coming  from  the  recurrent,  and 
form  an  anastomosis  analogous  to  the  anastomosis  of 
Galien  (Fig.  458,  5). 

Before,  penetrating  the  larynx — and  even  very  near 
its  commencement — it  furnishes  a  motor  filament  to 


ORIGIN  AND  DISTRIBUTION 
OF  THE  EIGHTH  PAIR  OP 
NERVES    IN    MAN. 

1,  3,  4,  Medulla  oblongata; 
1,  corpus  pyramidale  of 
one  side ;  2,  pons  Varolii  ; 
3,  corpus  olivare;  4,  corpus 
restifbrme  ;  5,  facial  nerve  ; 
6,  origin  of  gloss^^-pharyn- 
geal  nerve ;  7,  ganglion  of 
Andersch  ;  8,  trunk  of  the 
nerve  ;  9,  spinal  accessory ; 
10,  ganglion  of  pneumo- 
gastric; 11,  its  plexiform  ganglion;  12,  its  trunk;  13,  its  pharyngeal  branch,  forming  the 
pharyngeal  plexus,  14,  assisted  by  a  branch  from  the  glosso-pharyngeal,  8,  and  one  from  the 
superior  laryngeal,  15;  16,  cardiac  branches;  17,  recurrent  laryngeal  branch;  18,  anterior 
pulmonarv  iiranches ;  19,  posterior  pulmonary  branches;  20,  oesophageal  plexus;  21,  gastric 
branches ;' 22.  origin  of  the  spinal  accessory  nerve;  23,  its  branches  distributed  to  the  sterno- 
maxillaris  and  mastoido-humeralis ;  24,  its  branches  to  the  trapezius  muscle. 


TEE  NERVES. 


the  crico-pharyngeal  and  crico-thyroid  muscles.  This  filament  either  arises  directly 
from  the  pneumogastric  nerve,  or— as  is  most  frequently  the  case — from  the 
pharyngeal  ramuscule  ;  this  is  the  external  laryngeal  nerve  of  anthropotomists 


(Fig.  458,  8). 


The  external  laryngeal 

Fig.  458. 


DISTRIBUTION  OF   THE  NERVES  IN   THE    LARYNX 
OF   THE   HORSE, 

s,  Base  of  the  tongue  ;  h,  epiglottis  ;  c,  arytenoid 
muscles ;  c?,  section  of  the  thyroid  cartilage  to 
show  the  parts  it  covers;  e,  cricoid  cartilage; 
/,  trachea;  g,  oesophagus;  h,  thyro-arytaenoid 
muscle ;  i,  lateral  crico-arytaenoid  muscle ; 
j,  posterior  crico-aryiaenoid  muscle  ;  k,  arytse- 
noid  muscle.  1,  Superior  laryngeal  nerve ; 
2,  inferior  laryngeal ;  3,  br:iuches  of  the 
superior  laryngeal  passing  to  the  epiglottis 
and  tongue;  4,  branches  of  the  superior  laryn- 
geal passing  to  the  oesophagus  ;  5,  very  rine 
multiple  anastomoses  between  the  two  laryn- 
geals ;  6,  tracheal  branches  ;  7,  branch  to  the 
posterior  crico-arytfenoid  muscle  (a  portion  is 
distributed,  tlirough  the  muscles,  to  the 
subjacent  mucous  membrane);  8,  branch  to 
the  lateral  crico-arytaenoid  muscle;  9,  branch 
to  the  thyro-arytfenoid  muscle ;  10,  branch 
passing  to  the  arytaenoid  muscle;  11,  (Esopha- 
geal branch  of  the  pharyngeal  nerve  (it  some- 
times comes  from  the  external  laryngeal). 
(From  Toussaint's  work.) 


receives  accessory  branches  from  the 
superior  cervical  ganglion,  the  oesopha- 
geal branch,  and  the  pharyngeal  nerve, 
and  is  then  distributed  to  the  muscular 
tunic  of  the  oesophagus.  It  is  to  the 
union  of  this  branch  with  the  oesopha- 
geal branch  of  the  pharyngeal  nerve, 
that  we  have  given  the  name  of  ^mperior 
(Bsopliageal  nerves} 

4.  Communicating  Filaments 
with  the  Inferior  Cervical  Gang- 
lion.— These  do  not  always  directly 
enter  this  ganglion,  for  when  the  middle 
cervical  ganglion  exists  they  pass  to  it. 
They  are  not  similarly  disposed  on  both 
sides.  The  filaments  of  the  right  pneu- 
mogastric, two  or  three  in  number,  are 
extremely  short,  though  voluminous. 
The  left  pneumogastric  usually  only 
furnishes  a  single,  long,  thin  ramuscule, 
which  is  detached  in  the  region  of  the 
neck  near  the  point  where  the  pneumo- 
gastric commences  to  separate  from  the 
cervical  branch  of  the  sympathetic,  and 
reaches  the  inferior  cervical  branch  of 
the  sympathetic,  and  reaches  the  inferior 
cervical  ganglion  by  remaining  along- 
side the  principal  nerve. 

5.  Inferior  Laryngeal  Nerve 
(Figs.  458,  2;  480,  27,  28).— Also 
named  the  recurrent,  or  tracheal  re- 
current, because  of  its  disposition.  It 
begins  in  the  thoracic  cavity,  and 
ascends  along  the  trachea  to  the  larynx, 
the  intrinsic  muscles  of  which  it  stimu- 
lates, with  the  exception  of  the  crico- 
thyroid. 

The  two  recurrent  nerves  are  not 
quite  symmetrical  at  their  origin.  That 
of  the  right  side  is  detached  from  the 
pneumogastric  below  the  axillary  artery, 
near  the  dorso-cervical  artery.  It  is 
immediately  reflected  forward  in  em- 
bracing the  origin  of  that  vessel, 
asrainst    the   trachea,    in    the   middle 


which  it   crosses  inwards  to  be   placed 

•  Toussaint  has  seen  this  branch  leave  the  oesophagus  to  lie  beside  the  recurrent ;  but  its 
filaments  always  return  to  that  tube  as  ascending  twigs. 


TEE  CRANIAL   OR  ENCEPHALIC  NERVES.  839 

of  the  principal  cardiac  nerves,  with  some  of  which  it  contracts  intimate 
relations. 

On  the  left  side,  it  is  only  when  the  pneumogastric  nerve  arrives  near  the 
root  of  the  Imig  that  it  gives  off  its  recurrent.  To  be  reflected  forward,  the 
latter  turns  from  left  to  right  behind  the  arch  of  the  aorta,  and  arrives  beneath 
the  inferior  face  of  the  trachea,  among  the  cardiac  nerves,  with  which  it  com- 
municates, like  the  right. 

The  inferior  laryngeal  nerves  are  in  this  way  mixed,  at  a  greater  or  less  dis- 
tance from  their  commencement,  with  those  branches  of  the  sympathetic  (see 
the  description  of  the  si/mpathetic)  which  collectively  constitute  the  tracheal 
plexus.  They  are  soon  disengaged,  however,  and  leave  the  chest,  but  always  in 
proceeding  along  the  inferior  face  of  the  trachea,  then  ascending  on  its  sides, 
below  the  carotid  arteries,  which  they  gradually  approach,  and  finally  attain  the 
larynx  in  penetrating  beneath  the  crico-pharyngeal  muscle. 

According  to  Goubaux,  the  left  recurrent  must  be  situated  more  superficially 
than  the  right  in  the  lower  part  of  the  neck,  and  for  this  reason  should  be  more 
exposed  to  compression.  He  thus  explains  why,  in  chronic  "roaring,"  the 
alterations  observed  are  nearly  always  in  the  left  muscles  of  the  larynx. 

The  terminal  divisions  of  the  recurrents  are  distributed  to  the  posterior  and 
lateral  crico-aryttenoid,  and  the  arytainoid  and  thyro-arytasnoid  muscles,  as  well 
as  to  the  subglottic  mucous  membrane. 

In  their  long  course,  they  emit  collateral  ramuscules  that  also  ascend,  and 
are  distributed  to  the  mucous  membrane  and  muscular  layer  of  the  trachea,  as 
well  as  to  that  of  the  oesophagus.' 

The  recurrent  msophageal  ramuscules  are  all  sensitive,  and  form  five  groups  : 
the  first  and  second  arise,  on  the  left  side,  close  to  the  arch  of  the  aorta,  ascend 
on  the  sides  of  the  trachea,  and  pass  to  the  portion  of  the  oesophagus  lying 
between  that  tube  and  the  thoracic  section  of  the  longus  colli  muscle.  The 
third,  more  considerable,  springs  from  a  branch  given  off  at  the  brachial  trunks  ; 
it  is  markedly  recurrent,  and  forms  on  the  side  of  the  trachea,  with  the  second, 
a  small  plexus,  and  then  lies  closely  alongside  the  oesophagus,  which  it  accom- 
panies for  a  distance  of  eight  inches  from  the  first  rib.  The  branch  constituting 
the  fourth  group  is  the  longest  of  all ;  it  is  detached  about  two  or  two  and  a  half 
inches  in  front  of  the  first  rib,  and  after  emitting  several  long  tracheal  filaments, 
it  ascends  on  the  side  of  the  trachea,  close  to  the  border  of  the  oesophagus,  where 
it  generally  disappears  at  about  six  or  eight  inches  from  the  pharynx.  The  fifth 
group  is  composed  of  a  branch  detached  from  the  recurrent,  about  the  point 
where  the  preceding  terminates  ;  it  goes  entirely  to  the  origin  of  the  tube. 

6.  Cardiac  Filaments. — These  will  be  alluded  to  when  describing  the 
sympathetic  nerves. 

Terminal  Branches  of  the  Pneumogastric  Nerves.  1.  Bronchial 
Plexus  (Fig.  480,  29). — The  bronchial  plexus  is  formed  by  several  branches 
from  the  pneumogastric,  on  the  arrival  of  that  nerve  above  the  roots  of  the 
lungs  ;  these  interlace  into  a  network  and  ramify  around  the  bronchi,  following 
these  into  the  texture  of  the  lungs.  It  is  these  branches  which  give  to  the 
mucous  membrane  its  great  sensibility,  and  which  provoke  those  evident  con- 
tractions of  which  the  bronchioles  are  the  seat. 

2.  (Esophageal  Branches  (Fig.  480,  30,  31).— After  emitting  the  ramus- 

('  For  a  detailed  description  of  the  superior  and  inferior  laryngeal  nerves,  see  my  treatise 
on  "■Roaring  in  Horses."     London  :  1889.) 


840  TEE  NERVES. 

cules  of  the  bronchial  plexus,  each  pneumogastric  is  continued  along  the 
oesophagus  by  two  branches — a  superior  and  inferior — making  four  branches 
for  the  two  nerves.  The  two  superior  lie  together,  and  form  a  single  cord, 
either  immediately  or  after  a  certain  course  :  the  two  inferior  comport  them- 
selves in  the  same  manner  with  one  another — making  a  double  anastomosis,  from 
which  arise  the  two  nerves  we  are  about  to  describe,  and  which  are  designated 
the  oesophageal  nerves,  because  of  their  situation.  The  right  nerve  forms  a  large 
portion  of  the  superior  cord  ;  the  left,  especially,  gives  ramuscules  to  the  inferior. 

Placed  between  the  layers  of  the  posterior  mediastinum,  these  two  nerves 
follow  the  oesophagus  for  a  certain  distance — one  above,  the  other  below — giving 
off  some  ramuscules  to  that  muscular  tube,  detaching  one  or  two  communicating 
branches,  and  traversing  the  foramen  sinistrum  in  the  diaphragm  to  enter  the 
abdominal  cavity. 

The  inferior  terminates  in  the  parieties  of  the  stomach,  by  forming  on  the 
small  curvature,  to  the  right  of  the  cardia,  a  very  rich  pre-stomachal  plexus, 
which  throws  the  majority  of  its  ramuscules  on  the  right  sac  of  that  viscus. 

The  superior  passes  to  the  left  of  the  oesophageal  insertion,  along  with  the 
gastro-pulmonary  artery,  and  is  lost  in  the  solar  plexus,  after  giving  off  numerous 
divisions  on  the  left  sac  of  the  stomach,  mixing  with  the  sympathetic  ramuscules 
that  encircle  the  gastric  artery,  and  anastomosing  around  the  cardia  with  those 
of  the  inferior  cord.  It  is  very  difficult  to  follow  the  filaments  of  this  cord  from 
the  pneumogastrics  after  their  arrival  at  the  solar  plexus  ;  we  nevertheless  observe 
some  of  them  passing  to  the  liver,  others  accompanying  the  sympathetic  branches 
that  come  from  the  solar  to  the  posterior  mesenteric  plexus  in  following  the 
small  mesenteric  vein  ;  and  no  doubt  others  find  their  way  among  the  filaments 
of  the  trisplanchnic  nerve,  which  proceed  with  the  anterior  mesenteric  artery. 

Functions  of  the  Pneumogastric. — Formed  by  the  two  orders  of  fibres, 
the  pneumogastric  is  a  sensory-motor  nerve,  and  the  seat  ot  reflex  currents  which 
make  it  play  a  very  important  part  in  several  acts  of  vegetative  life,  and  bring  it 
into  relationship  with  the  great  sympathetic  nerve,  with  which  we  have  seen  that 
the  tenth  pair  maintains  anastomotic  connections  in  several  points  of  its  course. 

It  is  the  pneumogastric  nerve  that  gives  to  the  mucous  membrane  of  the 
larynx  the  exquisite  sensibility  it  enjoys. 

It  stimulates  the  motor  muscles  of  the  larynx  to  movement. 

To  it  is  also  due  the  sensibility  of  the  broncho-pulmonary  mucous  membrane. 

It  causes  contractions  of  the  muscular  fibres  in  the  broncho-tracheal  passages 
— contractions  which  are  involuntary,  and  due  to  reflex  influence. 

It  also  causes  movements  of  the  oesophagus  and  the  stomach,  which  are 
involuntary  and  due  to  reflex  currents. 

Perhaps  it  acts  in  an  analogous  manner — by  reflex  action — in  the  secretion  of 
the  gastric  fluid  and  the  functions  of  the  Hver  ;  but  these  are  points  which  science 
has  not  yet  determined. 

It  appears  proved  that  it  exercises  an  influence  on  the  essential  phenomena  of 
respiration  (liaulanie),  as  it  participates  in  the  centripetal  stimulation  which 
brings  the  respiratory  mechanism  into  play. 

It  transmits  to  the  heart  the  influence  of  the  moderating  centre  of  that  organ 
which  is  situated  at  its  roots  in  the  meduUa  oblongata. 

After  its  section  in  the  region  of  the  neck,  the  movements  of  the  heart 
become  very  precipitate,  and  we  may  diminish  the  force  of  these  movements,  or 
even  completely  arrest  them,  by  galvanizing  the  peripheral  end  of  the  nerve.     In 


TEE  CRANIAL   OB  ENCEPHALIC  NERVES.  841 

this  action  on  the  heart,  one  nerve,  usually  the  right,  plays  a  predominant  part 
(Arloing  and  Tripier). 

It  also  transmits  to  the  bulbar  vaso-motor  centres,  through  the  medium  of 
the  depressor  nerve  of  the  circulation — Cyon's  nerve — which  forms  part  of  it,  a 
stimulus  that  leaves  the  heart  and  produces  a  general  vaso-dilatating  effect — 
chiefly,  however,  in  the  abdominal  cavity. 

11.  Eleventh  Pair,  Spinal  Accessory  Nerves,  or  Accessory  Nerves  of 
THE  Pneumogastrics  (Fig.  456,  2,  4). 

The  spinal  accessory  is  an  exclusively  motor  nerve,  which,  at  its  exit  from 
the  cranium,  is  so  intimately  connected  with  the  pneumogastric,  that  we  might 
perhaps  follow  the  example  of  Miiller,  and  describe  the  two  as  forming  one  and 
the  same  pair. 

Origin. — This  nerve  exhibits  a  singular  disposition,  in  that  it  arises  from  the 
"whole  extent  of  the  cervical  spinal  cord,  and  ascends  in  the  spinal  canal  to  near 
the  pneumogastric,  with  which  it  leaves  the  cranium  by  the  posterior  part  of 
the  foramen  lacerum.  It  is  also  described  as  a  cranial  nerve,  in  consequence 
of  the  latter  peculiarity  ;  but  from  its  origin  it  is  rather  a  spinal  nerve,  a  fact 
which  is  sufficiently  indicated  by  the  name  generally  given  to  it. 

In  the  interior  of  the  spinal  canal,  it  is  a  long  cord  measuring  from  27  to  31 
inches  in  middle-sized  animals.  It  commences,  by  a  very  fine  point,  at  the 
cervical  or  brachial  enlargement  of  the  spinal  cord,  follows  that  organ  in  an 
ascending  course,  lying  close  to  its  lateral  column,  and  passing  between  the  roots 
of  the  two  orders  of  cervical  nerves  until  it  arrives  at  the  medulla  oblongata, 
where  it  is  inflected  outwards  at  the  foramen  lacerum  posterius,  into  which  it 
passes  to  leave  the  cranium. 

In  this  ascending  course  it  gradually  increases  in  volume,  as  it  at  intervals 
receives  additional  filaments  from  the  lateral  column  of  the  spinal  cord,  like  the 
radicular  extremity  of  the  nerve  itself.  Traced  into  the  spinal  cord,  the  radicular 
filaments  are  found  to  arise  from  a  nucleus  situated  outside  the  base  of  the 
inferior  cornua.  Before  making  its  escape  from  the  cranium,  it  receives,  besides, 
some  of  the  posterior  or  motor  roots  of  the  pneumogastric  nerve.  In  the  fora- 
men lacerum,  it  becomes  applied  against  the  ganglion  (jugular)  of  that  nerve,  in 
the  manner  of  motor  fibres  of  mixed  nerves,  and  gives  it  some  of  its  own  filaments, 
while  it  also  receives  others. 

The  long  cord  here  described  as  the  root  of  the  spinal  accessory,  is  considered 
by  some  authorities  as  only  a  portion  of  this  nerve,  to  which  they  give  the  name 
of  external  or  medullanj  root  of  the  spinal  accessory.  They  designate  as  the 
internal  or  bulbar  root  of  that  nerve,  the  anastomosing  filaments  already  described 
as  the  motor  roots  of  the  pneumogastric.  According  to  them,  this  internal  root 
only  lies  beside  the  pneumogastric  for  a  very  short  distance,  ultimately  leaving 
it  and  forming  the  superior  laryngeal  and  pharyngeal  nerves,  which  seem  to  arise 
from  the  vagus  rather  than  from  the  accessory  of  Willis. 

Distribution. — Beyond  the  ganglion  of  the  pneumogastric,  the  spinal  accessory 
nerve  remains  beside  the  trunk  of  the  pneumogastric  for  scarcely  an  inch ;  it 
then  separates  from  it  at  an  acute  angle,  the  sinus  of  which  is  occupied  by  the 
great  hypoglossal  nerve,  is  directed  backwards,  passing  beneath  the  superior 
extremity  of  the  maxillary  gland  and  mastoido-humeralis  muscle,  gains  the 
supero-posterior  border  of  that  muscle,  and  follows  it  to  the  front  of  the  shoulder. 


842  TEE  NERVES. 

Here  it  slightly  ascends,  crosses  that  region  below  the  inner  face  of  the  cervical 
trapezius,  and  is  distributed  to  the  dorsal  trapezius. 

On  its  passage  it  emits  :  1.  One  or  two  thick  filaments  to  the  superior  cervical 
ganglion,  proceeding  from  the  spinal  accessory  by  a  small  plexiform  network, 
where  the  nerve  separates  from  the  pneumogastric.  2.  Near  the  maxillary  gland, 
a  thick  branch  to  the  sterno-masillaris  muscle.  3.  Slightly  beyond  this,  another 
branch  destined  to  the  anterior  portion  of  the  mastoido-humerahs,  4.  A  series 
of  ramuscules  to  the  cervical  trapezius. 

In  its  course,  the  spinal  accessory  traverses  the  anterior  part  of  the  superficial 
cervical  plexus,  and  receives  additional  ramuscules  from  the  first,  second,  third, 
fourth,  fifth,  and  sometimes  even  from  the  sixth  cervical  nerves. 

Reduced  to  its  medullary  root,  as  has  been  described,  the  spinal  accessory 
stimulates  the  muscles  to  which  it  is  distributed,  and  through  them  has  a  share 
in  expiration.  By  the  contraction  of  these  muscles,  the  ribs  may  be  maintained 
raised  for  a  certain  period,  and  cause  the  air  to  be  slowly  expelled  ;  also  allowing 
the  sounds  or  voice  produced  by  its  passage  through  the  larynx  to  be  modulated. 
Crowing  is  no  longer  possible  in  Birds  when  the  medullary  root  of  the  spinal 
accessory  has  been  divided,  as  has  been  demonstrated  by  Bernard. 

12.  Twelfth  Paie,  ok  Hypoglossal  Neeves  (Figs.  171,  22 ;  456,  5;  459,  10). 

The  hypoglossal  nerve  is  exclusively  motor,  and  stimulates  the  muscles  of  the 
tongue. 

Origin. — It  apparently  arises  from  the  lower  face  of  the  medulla  oblongata, 
on  the  prolongation  of  the  line  of  origin  of  the  inferior  spinal  nerves,  by  a  dozen 
converging  filaments.  Traced  into  the  medulla,  these  filaments  are  found  to  pass 
into  a  principle  nucleus  situated  near  the  point  where  the  central  canal  of  the 
spinal  cord  enlarges  to  form  the  floor  of  the  fourth  ventricle,  inside  the  pneumo- 
spinal  nucleus,  and  in  the  small  masses  of  grey  substance  placed  below  and  out- 
side the  preceding,  named  the  accessory  nucleus. 

The  roots  of  the  hypoglossal  nerve  pass  through  the  dura  mater  in  two  or 
three  bundles,  which  enter  the  condyloid  foramen  of  the  occipital  bone,  where 
they  unite  to  form  a  single  cord.  The  hypoglossal  has  also  a  ganglionic  root 
which  Toussaint  constantly  found  in  the  Ass,  Mule,  Ox,  and  Bog,  and  which 
had  been  previously  seen  by  Meyer  and  Yulpian.  The  ganglion  of  the  hypo- 
glossal in  the  Horse  is  fusiform,  and  the  size  of  a  small  lentil  (Fig.  456,  5').  It 
is  sometimes  absent. 

Distrihution. — The  hypoglossal  nerve,  thus  constituted,  immediately  after  its 
departure  from  the  condyloid  foramen,  communicates  with  the  first  cervical  pair 
by  means  of  a  transverse  ramuscule  ;  it  then  passes  between  the  spinal  accessory 
and  pneumogastric  nerves,  descends  on  the  external  face  of  the  guttural  pouch, 
where  it  is  connected  with  the  superior  cervical  ganglion  of  the  sympathetic  by 
numerous  filaments,  which  in  great  part  form  the  plexiform  network  called  the 
"  guttural  plexus."  The  nerve  afterwards  crosses  to  the  outside  of  the  external 
carotid  artery,  in  proceeding  forward  and  downward  on  the  side  of  the  pharynx 
and  larynx,  receiving  at  that  point  a  slender  ramuscule  from  the  first  cervical ; 
it  then  passes  within  the  inferior  extremity  of  the  stylo-hyoid  muscle  and  the 
submaxillary  artery,  which  it  crosses  very  obliquely,  is  prolonged  between  the 
mylo-hyoid  and  great  hyo-glossus  muscles,  sends  numerous  small  filaments  to 
the  latter  and  a  ramuscule  to  the  genio-hyoideus,  and  finally  terminates  in  a 


THE    CBANIAL   OR  ENCEFEALIC  NERVES, 


843 


series  of  branches  analogous  to  those  of  the  gustatory  nerve,  and  which  mix 

with  them.  ,    ,  ^    • 

These  branches  are  therefore  reflected  upwards,  bendmg  round  the  posterior 

Fig.  459. 


DEEP  NERVES  OF  THE  HEAD  IN  THE  MULE. 

1   Superior  maxillary  nerve  at  its  exit  from   the  foramen  lacerum  ;   2,  masseteric  nerve;   3,  sub- 
'  zygomatic  nerve ;    4,  buccal ;    5,  lingual  or  gustatory  nerve ;    6,  chorda  tympani ;    7,  inferior 
maxillary  nerve,  cut  near  where  it  enters  the  maxillo-dental  canal;  8,  mylo-hyoideus  nerve 


maxiuary  ueive,  uui.  ncai   «iicic   ii,  c.cio   x..^   ............  ..., „„.....,   _,..._,-.  -j -■_  ,. 

pterygoid  nerve;  10,  glosso-pharyngeal  nerve;  11,  its  pharyngeal  branch;  12,  its  lingual  branch; 
13,  pneumogastric  nerve;  14,  superior  laryngeal  branch  of  that  nerve;  15,  its  pharyngeal 
branch;  16,  spinal  accessory  of  Willis;  17,  hypoglossal  nerve;  18,  origin  of  the  cervical  cord  of 
the  great  sympathetic;  19,  the  same  after  its  union  with  the  pneumogastric.  A,  Common 
carotid  artei-y  ;  B,  accessory  thyroid  artery  ;  C,  thyro-laryngeal  artery  ;  D,  origin  of  the  internal 
carotid  artery  (the  vessel  is  concealed  by  the  guttural  pouch)  ;  E,  occipital  artery ;  F,  external 
carotid  artery;  G,  internal  maxillary  artery;  JI,  pharyngeal  artery  (drawn  too  large);  /,  sub- 
maxillary artery;  J,  lingual  artery;  A',  origin  of  the  maxillo-muscular  artery;  L,  posterior 
auricular  artery  ;  M,  trunk  or  origin  of  the  superficial  temporal  artery ;  0,  inferior  dental  artery ; 
F.  posterior  deep  temporal  artery;  Q,  anterior  deep  temporal  artery;  ^,  maxillary  gland;  S, 
Wharton's  duct ;  T,  sublingual  gland.  The  letter  N  placed  at  the  upper  end  of  the  large  cornu 
of  the  hyoid  bone  has  no  signification. 

border  of  the  great  hyo-glossus,  and  pass  into  the  interstice  between  that  muscle 
and  the  genio-glossus.     They  are  distributed  to  all  the  muscles  of  the  tongue. 

The  hypoglossals,  being  motor  nerves,  cause  the  contraction  of  the  muscles 
of  the  tongue  during  the  movements  proper  to  mastication  and  the  production 
of  the  voice.  Though  they  most  frequently  act  together,  yet  they  may  do  so 
separately,  as  in  the  unilateral  movements  of  the  tongue. 

Differential  Characters  in  the  Cranial  Nerves  of  the  other  Animals. 

In  the  domesticated  Mammals,  the  cranial  nerves  offer  the  greatest  analogies;  their  origin 
is  the  same  in  all,  and  it  is  only  in  their  distribution  that  we  find  some  variety,  due  to  the 


844  THE  NERVES. 

difference  in  the  form  of  the  head.  Consequently,  in  this  comparative  analysis  we  shall  not 
discover  any  fundamental  differential  characters. 

Ruminants. — There  is  no  difference  to  note  in  the  four  fimt  pairs. 

Trigeminal  nerve. — Divided  into  three  branches  as  in  Solipeds.  It  has  been  stated  that  in 
Ruminants  the  ophthalmic  branches  are  distributed  to  the  majority  of  tlie  muscles  of  the  eye; 
in  the  Sheep,  we  have  only  seen  the  palpebro-nasal  nerve  offering  this  relationship  to  the 
motor  organs  of  that  part.     Tiie  anterior  palatine  nerve  is  relatively  voluminous. 

In  the  Ox  and  Sheep,  the  buccal  nerve  furnishes  the  excito-secretory  nerve  of  the  parotid 
gland;  it  is  inflected  on  the  anterior  border  of  tlie  masseter,  and  follows  Steno's  duct,  iu  both 
species,  to  reach  the  gland.  It  is  often  formed  by  two  parallel  filaments  (Moussue).  A  filament 
of  the  inferior  branch  of  the  buccal  nerve  which  goes  to  the  molar  gland,  is  also  excito-secretory 
(Moussu). 

Facial  nerve. — Towards  the  middle  of  its  subparotideal  course,  tliis  gives  off  a  large 
anterior  auricular  nerve ;  when  it  arrives  at  the  middle  of  the  posterior  border  of  the  masseter 
muscle,  it  divides  into  two  branches.  The  inferior  branch  passes  obliquely  downwards  and 
forwards,  towards  the  mental  foramen,  where  it  terminates  as  in  the  Horse;  it  furnishes  an 
anastomotic  branch  to  the  superior.  The  latter  crosses  the  middle  portion  of  the  masseter,  and 
becomes  mixed  with  the  suborbital  ramuscules  of  the  fifth  pair;  about  the  midille  of  its 
course  it  receives  a  filament  from  the  superficial  temporal  nerve.  We  need  not  allude  to  the 
auditory  and  glosso-pharyngeal  nerves,  except  to  say  that  the  latter  communicates  with  the 
pneumogastric  soon  after  its  exit  from  the  foramen  lacerum. 

Pnenmogastric  nerve. — This  offers  numerous  differences  in  its  roots  and  distribution. 

In  the  Ox  and  Sheep,  the  sensitive  roots  arise  from  an  irregularly  elliptical  surface  com- 
prising the  whole  of  the  respiratory  tract.  They  are  from  fifteen  to  twenty  in  number,  and 
often  join  each  other;  they  may  divide  into  three  principal  fasciculi  arising  at  slight  distances. 

The  Tnotor  roots  are  a  little  larger  than  in  the  Horse  ;  before  joining  the  sensitive  roots  they 
are  confounded  in  a  small  ganglion  that  pertains  to  them. 

The  jitgular  ganglion  is  voluminous,  but  apart  from  this  it  presents  the  same  features  as  in 
the  Horse,  receiving  all  the  proper  roots  of  tlie  pneumogastric  and  internal  root  of  the  spinal 
accessory,  and  even  those  which  are  united  in  their  own  ganglion.  The  portion  of  the 
ganglion  that  is  more  especially  formed  by  the  roots  of  tlie  spinal  accessory  is  rather  an  intri- 
cation  of  nerve-fibres  than  a  real  ganglion ;  it  is  impossible  by  the  most  minute  dissection  to 
separate  it  from  the  rest  of  the  ganglion. 

The  jugular  ganglion  also  receives  a  division  of  the  glosso-pharyngeal,  and  it  gives  one  to 
this  nerve  and  the  external  branch  of  the  spinal  accessory. 

The  pneumogastric  nerve,  in  the  guttural  -portion,  is  much  larger  than  in  the  Horse.  This 
peculiarity  is  noticeable  throughout  its  whole  extent,  and  is  indicated  at  its  roots. 

The  ganglionic  plexus  is  absent  in  the  Ox.  The  course  and  relations  of  the  nerve  in  this 
portion,  are  analogous  to  those  observed  in  Solipeds. 

The  pharyngeal  nerve  is  voluminous,  and  the  branch  it  sends  to  tlie  oesophagus  is  the 
largest  of  its  divisions:  this  branch  passes  backwards  to  the  surface  of  the  constrictors  of  the 
pharynx,  joins  the  external  laryngeal,  gives  a  large  branch  to  the  thyro-pharyngeus,  and  is 
insinuated  on  the  sides  of  the  oesophagus,  between  it  and  the  thyroid  gland ;  there  it  divides 
into  two  portions,  one  of  which  descends  on  the  sides  of  the  oesophagus,  where  it  forms  a  very 
rich  plexus  with  the  l)ranche8  from  the  inferior  laryngeal,  wliile  the  other  is  lost  immediately 
in  the  recurrent  nerve  at  the  thyroid  gland. 

The  external  laryngeal  arises  at  a  short  distance  above  the  superior  laryngeal,  where  it 
receives  a  large  branch  from  the  glosso-pharyngeal  and  another  from  the  sympathetic,  and 
immediately  passes  alongside  the  oesophageal  branch  of  the  pharyngeal  nerve.  With  a  little 
attention,  we  may  dissect  a  fasciculus  coming  from  the  external  laryngeal  and  passing  to  the 
crico-thyroid  muscle,  and  the  thyroid  gland  and  its  vessels,  after  receiving  a  branch  from 
the  superior  laryngeal.  In  the  Sheep,  the  external  laryngeal  sometimes  gives  a  branch  to 
the  oesophagus,  and  whicli  anastomoses  with  the  inferior  laryngeal,  or  descends  on  the  side 
of  the  tube,  conjointly  with  the  oesophageal  branch  of  the  pharyngeal. 

The  superior  laryngeal  rises  below  the  preceding ;  it  is  very  voluminous,  and  communicates 
with  the  sympathetic,  either  directly  or  through  the  medium  of  the  guttural  plexus,  and  with 
the  pharyngeal  nerves  and  external  laryngeal.  Beneath  the  thyroid  cartilage,  a  large  division 
anastomoses  with  the  inferior  laryngeal,  and  is  finally  lost  in  that  nerve  below  the  larynx.  It 
is  easily  seen  that  this  brancli  gives,  in  the  cervical  region,  a  great  number  of  filaments  to  the 
oesophagus  and  trachea. 

With  the  exception  of  some  insignificant  peculiarities,  the  pneumogastric  comports  itself  In 
the  cervical  and  thoracic  regions  as  in  the  Horse. 


THE  CRANIAL   OR  ENCEPHALIC  NERVES. 


The  recurrente  arise  as  in  Solipeds,  but  their  relations  are  somewhat  different  in  the  cervical 
region.     They  are  placed  in  the  channel  formed  by  the  trachea  and  oesophagus,  and  are 

Fig.  460. 


NERVES  OF  THE  GUTTURAL  REGION  IN  THE  OX. 

fl,  (Esophagus ;  6,  trachea;  c,  common  carotid  artery;  c?,  glosso-facial  artery.  1,  Pneumogastric 
nerve;  2,  spinal  accessory;  3,  glosso-pharyngeal ;  4,  great  sympathetic  and  cervical  ganglion; 
5,  pharyngeal  nerve;  6,  external  laryngeal;  7,  superior  laryngeal;  8,  inferior  laryngeal;  9,9, 
oesophageal  branches  of  tiie  pharyngeal  and  external  laryngeal. 

56 


846  THE  NERVES. 

separated  from  the  carotid  artery  and  the  cord  common  to  the  sympathetic  and  pneumog;a8trifl 
by  the  very  great  width  of  the  CESophagus.  Their  distribution  to  the  muscles  of  the  larynx 
takes  place  as  in  the  Horse ;  the  only  noteworthy  feature  is  the  anastomosis  of  the  nerve,  end 
to  end,  witli  the  superior  laryngeal.  In  the  wliole  of  its  cervical  portion,  the  branches  to  the 
oesophagus  are  more  numerous  and  voluminous  than  in  Solipeds,  although  they  all  have  the 
same  physiological  oflSce,  except  those  that  are  derived  from  the  branch  of  tlie  superior  laryngeal, 
which  are  motor. 

The  differences  remarked  in  the  nerve  in  the  abdominal  cavity,  are  in  relation  to  the  volume 
and  form  of  the  stomach  and  its  compartments. 

The  following  is  what  we  have  observed  in  the  Sheep : — 

After  receiving  a  large  filament  from  the  superior  cord,  the  inferior  oesopJiageal  nerve 
divides  into  three  principal  branches :  one  passes  to  the  left,  furnishing  nerves  to  the  anterior 
face  and  greater  curvature  of  the  reticulum  and  the  upper  border  of  the  rumen ;  a  median, 
which  is  distributed  to  the  anterior  face  of  the  psalterium,  reaches  the  substance  of  the 
mesentery,  follows  the  abomasum,  to  which  it  sends  some  filaments,  and  finally  anastomoses 
with  the  retrograde  nerves  coming  from  a  rich  plexus  that  exists  on  the  posterior  face  of  the 
liver  and  gall-bladder ;  it  forms,  conjointly  with  the  divisions  of  tiie  solar  plexus  and  superior 
oesophageal  nerve,  a  rich  plexus,  from  which  arise  branches  to  the  liver,  abomasum,  and 
duodenum. 

The  superior  cesophageal  nerve  is  chiefly  distributed  to  the  rumen.  Before  reaching  the 
stomach,  it  gives  several  divisions  to  the  plexus  already  mentioned — and  which  might  be 
named  the  "  hepatic  plexus" — receives  a  large  branch  from  the  solar  plexus,  and  sends  to  it  a 
smaller  one.  It  afterwards  divides  into  two  principal  branches,  the  largest  of  which  passes 
along  the  superior  fissure  of  tije  rumen,  along  with  the  vessels  of  that  organ.  According  to 
Lavocat,  this  branch  forms  a  large  plexus  there,  which  has  in  its  centre  a  guuglionic  enlarge- 
ment, whence  emanate  the  ramuscules  that  go  to  the  whole  of  the  upper  face,  sides,  and  lower 
surface  of  the  rumen.  In  the  Sheep  we  have  not  found  a  ganglion,  but  this  does  not  prevent 
this  branch  from  being  distributed  to  all  the  parts  indicated  by  Lavocat. 

The  other  branch  is  very  large,  and  situated  in  the  omentum  until  it  arrives  at  its  convex 
border,  when  it  leaves  it  to  be  distributed  to  the  left  side  of  ti  e  abomasum;  while  the  analo- 
gous nerve  fiom  the  inferior  oesophageal  passes  more  especially  to  the  right  face. 

In  the  Camel,  the  pneumogastric  gives  off,  near  the  point  where  it  joins  the  cervical 
branch  of  the  sympathetic,  a  very  remarkable  branch.  This  is  somewhat  plexiform  at  its 
origin,  and  directly  furnishes  a  certain  number  of  pharyngeal  filaments,  the  superior  laryngeal 
nerve,  and,  a  little  lower,  the  inferior  laryngeal  nerve,  forming  a  slight  arch  where  it  curves  to 
ascend;  it  tiien  descends  along  the  oesophagus  into  the  thorax,  giving  filaments  to  that  tube 
and  to  the  trachea.  When  it  reaches  the  second  dorsal  vertebrae,  this  branch  unites,  below 
the  oesophagus,  with  that  of  the  opposite  side.  The  single  branch  resulting  from  this  union 
runs  between  the  trachea  and  oesophagus,  and  ends  by  dividing  into  several  filaments  that 
enter  the  bronchial  plexus. 

For  the  whole  of  its  cervical  course,  the  pneumogastic  lies  close  beside  the  sympathetic 
and  does  not  give  off  any  ramuscles  worthy  of  note.  After  separating  from  the  sympathetic 
at  the  entrance  to  the  chest,  it  passes  into  that  cavity  alongside  the  trachea  to  the  commence- 
ment of  the  bronchi ;  there  it  forms,  with  its  congener  of  the  opposite  side,  the  hroncho-oesopha- 
geal  plexus,  which  is  extremely  remarkable,  and  is  prolonged  behind  by  the  oesophageal  nerves 
— similar  to  those  in  the  Horse.  The  pneumogastric  does  not  appear  to  directly  furnish 
filaments  to  the  inferior  cervical  ganglion. 

Spinal  accessory.— The  origin  of  this  nerve  offers  slight  differences,  which  we  have  indicated 
in  speaking  of  the  motor  roots  of  the  pneumo.i^astric.  With  regard  to  its  distribution  in  the 
Ox,  it  offers  the  following  features :  At  the  inferior  extremity  of  the  transverse  process  of  the 
atlas,  it  divides  into  two  branches— a  superior  and  inferior.  The  first  is  a  little  larger  than 
the  spinal  accessory  of  the  Horse,  and  comports  itself  as  in  that  animal.  The  inf.  rior  branch 
is  directed  downward  and  backward,  traverses  the  muscle  we  have  named  the  sterno-sub- 
occipital  (see  Myology),  beneath  a  tendon  that  runs  across  the  muscular  fibres,  and  arrives 
letween  that  muscle  and  the  sterno-maxillaria.  At  this  point  it  separates  into  a  certain 
number  of  ramuscules,  the  first  three  or  four  of  which  are  slightly  recurrent,  and  enter  the 
upper  part  of  the  sterno-maxillaris ;  the  others  are  large  and  directed  towards  the  sternum, 
to  be  distributed  to  the  latter  muscle,  or  to  it  and  the  sterno-suboccipitalis. 

These  branches  ot  the  spinal  accessory  represent  the  branch  which,  in  the  Horse,  passes 
exclusively  to  the  sterno-maxillaris.  In  reflecting'  on  the  distribution  they  offer  in  the  Ox,  we 
are  biought  to  the  conclusion  that  the  sternal  hand,  which  has  been  described  as  belonging  to 
the  first,  forms,  with  the  sterno-suboccipitalis,  one  and  the  sacre  muscle— the  analogue  of  the 


THE  CRANIAL    OR  ENCEPHALIC  NERVES.  847 

sterno-maxillaris  or  sterno-mastoideus  of  Solipeds.  These  two  muscular  fasciculi  are,  other- 
wise, closely  attached  to  each  otlier,  if  not  cunfouuded  near  their  origin  at  the  anterior  pro- 
longation of  the  sternum. 

Lastly,  the  hypoglossal  nerve,  before  crossing  the  pneumogastric,  communicates  with  the 
first  cervical  by  a  considerable  brancli ;  lower,  it  gives  off  a  long  ramuscule  that  descends  on 
the  carotid  artery. 

Pig. — We  need  not  refer  to  the  olfactory,  optic,  or  motores  oculorum,  neitlier  to  the  glosso- 
pharyngeal,  as  what  has  been  siiid  about  them  in  Solipeds  holds  good  in  this  animal. 

Trigeminal  werye.— This  also  divides  into  tliree  principal  branches.  The  palpebro-nasal 
ramuscule  of  the  ophthalmic  branch,  anastomoses  with  a  motor  nerve  of  the  eye  on  the  deep 
face  of  the  external  rectus  muscle.  The  superior  maxillary  nerve  leaves  the  cranium  by  the 
great  sphenoidal  slit,  and  immediately  enters  the  superior  dental  foramen ;  its  orbital  course  is 
therefore  very  short. 

Its  spheno -palatine  branch  passes  at  once  below  the  alveolar  tuberosity,  where  it  divides 
into  several  ramuscules:  one,  entering  the  palatine  fissure,  forms  the  posterior  palatine  nerve; 
the  others  pass  into  the  palatine  arch  at  various  distances,  to  cont^titute  the  middle  palatine 
nerves ;  some  of  them  even  enter  the  palatine  canal  with  the  anterior  palatine  or  palato-labial 
nerve. 

Facial. — Beneath  the  parotid  gland,  this  divides  into  several  branches,  of  which  there  are 
three  principal.  One  is  directed  upwards,  and  passes  in  front  of  the  ear ;  this  is  the  smallest. 
The  second  jiroceeds  forward,  crosses  the  masseter  near  the  zygomatic  process,  unites  with  the 
inferior  branch,  and  is  expended  among  the  suborbital  ramuscules  of  the  superior  maxillary. 
The  third  passes  downward  and  forward,  under  the  parotid  gland,  arrives  in  the  intermaxillary 
space,  is  inflected  in  front  of  the  masseter  to  become  superficial,  and  terminates  with  the 
middle  branch.  Towards  the  maxillo-labialis  muscle,  this  inferior  branch  gives  off  a  ramuscule 
.to  the  lower  lip. 

Pneumogastric. — This  joins  the  sympathetic  near  the  upper  third  of  the  neck,  and  at  its 
point  of  union  offers  a  greyish  enlargement  resembling  the  gaugliform  plexus  of  Man.  As  far 
as  the  origin  of  the  oesophageal  nerves,  the  pneumogastric  of  the  Pig  resembles  that  of  the 
Horse.  The  latter  is  voluminous,  and  does  not  divide  into  two  branches  immediately  beyond 
the  bronchial  plexus,  but  at  some  distance  from  it.  Numerous  anastomoses  exist  between  the 
two  oesophageal  nerves — superior  and  inferior.  At  their  termination  they  differ  much  from 
each  other  in  volume ;  the  inferior  is  very  small,  and  terminates  on  the  anterior  face  of  the 
stomach;  the  superior,  much  larger,  partly  remains  at  the  stomacii,  and  partly  crosses  the 
small  curvature  of  that  viscus  to  enter  the  solar  plexus. 

Spinal  accessory. — This  nerve  commences  and  terminates  as  in  Solipeds.  After  being 
inflected  backward  on  the  anterior  border  of  the  raastoido-humerali.-<,  it  divides  into  two 
ramuscules — a  deep  and  superticial.  The  first  is  confounded  with  a  cervical  nerve,  near  the 
intervertebral  foramen  through  which  the  latter  passes;  the  second  goes  to  the  trapeziug 
muscle,  in  which  it  is  expended. 

Near  the  base  of  the  tongue,  the  hypoglossal  gives  off  a  filament  that  passes  to  the  genio- 
hyoideus  muscle. 

Carnivora. — In  these  animals  the  majority  of  the  cranial  nerves  do  not  offer  any  important 
differences.  We  will,  therefore,  say  nothing  concerning  the  first  two  pairs,  or  of  the  motores 
oculorum,  spinal  accessory,  and  glosso-pliaryngeal,  except  that  the  motor  nerves  of  the  eye  are 
mixed  with  the  filament  of  the  ophthalmic  branch  among  the  muscles  of  the  orbit. 

Trigeminal  nerve. — When  the  branch  constituting  the  superficial  temporal  nerve,  reaches 
the  posterior  border  of  the  maxilla,  it  divides  into  several  ramuscules ;  one  portion  lies  beside 
the  middle  branch  of  the  facial,  the  other  accompanies  the  anterior  auricular  nerve  by  becoming 
intimately  united  to  it.  We  have  also  found,  in  the  Dog,  a  branch  that  is  detached  from  the 
inferior  maxillary,  almost  immediately  after  its  exit  from  the  cranium.  It  descends  into  the 
intermaxillary  space,  in  company  with  the  facial  artery.  At  the  posterior  border  of  the  mylo- 
hyoideus  muscle  it  separates  into  two  ramuscules:  one  is  applied  to  that  muscle,  and  follows 
it  to  near  the  symphysis  of  the  jaw;  the  other  is  inflected  outwards  and  upwards,  in  front  of 
the  masseter  muscle,  and  joins  the  inferior  branch  of  the  facial.  Owing  to  this  arrangement, 
each  of  the  branches  of  the  facial  is  provided  with  a  sensitive  ramuscule  from  the  fiftli  pair. 

The  lingual  nerve  furnishes  vaso-motor  and  excito-secretory  nerves  to  the  submaxillary 
and  sublingual  glands,  as  is  shown  in  Fig.  461,  borrowed  from  Bernard. 

Facial, — At  its  exit  from  the  external  auditory  hiatus,  it  divides  into  four  branches,  three 
of  which  appear  to  form  its  termination.  The  first — the  smallest — is  directed  downwards 
across  the  parotid  gland,  and  constitutes  the  cervical  ramuscule.  The  other  three  are  dis- 
tinguished as  superior,  middle,  and  inferior. 


THE  NEEVES. 


The  superior  branch,  the  largest,  ascends  towards  tlie  forehead,  and  describes  a  curve  with 
convexity  upwards,  turns  round  the  orbit,  and  terminates  near  its  nasal  angle.  In  its  course  it 
furnishes:  1  An  anterior  auricular  ramuscule.  2.  Above  the  insertion  of  the  masseter,  several 
muscular  filaments.  3.  It  is  crossed,  above  the  eye,  by  the  superciliary  filaments  of  the 
ophthalmic  nerve.  The  middle  branch  accompanies  Steno's  duct  to  the  surface  of  the  cheek ; 
reaching  the  anterior  border  of  the  masseter,  it  anastomoses  in  a  very  flexuous  manner  with 
the  ramuscule  of  the  inferior  branch,  and  ti-rminatps  in  the  upper  lip  and  the  end  of  the  nose. 
The  inferior  branch  pas&es   towards   the   maxillary  fissure;   there  it  receives   the  sensitive 


5    .jtf  m 
^    IT  t 


ramuscule  sent  to  it  by  the  fifth  pair,  gives  off  filaments  to  the  middle  branch,  and  is  then 
continued  into  the  lower  lip. 

Pneumogastric. — The  sensitive  roots  closely  resemble,  in  their  disposition,  those  in  the  Ox. 
The  motor  roots  are  separated  into  two  series  of  filaments ;  the  anterior  unite  in  a  small  ganglion 
then  pass  into  the  jugular  ganglion ;  the  posterior  lie  beside  the  medullary  root  of  the  spinal 
accessory,  but  leave  it  to  become  united  with  the  jugular  ganglion. 

Below  the  foramen  lacertim,  the  pneumogastric  nerve  gives  off  tlie  pharyngeal  nerve  before 
forming  the  analogue  of  the  plexifnrm  ganglion  of  Man.  This  plexus  is  better  defined  than 
in  him,  and  is  a  real  fusiform  elongated  ganglion,  at  the  grey  basis  of  which  some  white 
e  seen.     It  is  situated  a  little  farther  from  the  cranium  than  the  superior  cervical 


THE  CRANIAL   OR  ENCEPHALIC  NERVES.  849 

ganglion.  The  ganglion  itself  furnishes  the  superior  laryngeal  nerve,  which  gives  off,  as  in 
Man,  the  external  laryngeal  nerve. 

There  is  nothing  to  indicate  in  the  pharyngeal  nerve,  its  disposition  being  absolutely  the 
same  as  in  the  Ox. 

In  the  Dog,  the  superior  laryngeal  nerve  has  a  curious  disposition,  whicli  has  not  yet,  to 
our  knowledge,  been  described.  Reaching  the  inner  face  of  the  thyroid  cartilage,  it  gives  off, 
as  in  the  other  animals,  filaments  to  the  glottis,  epiglottis,  liase  of  the  tongue,  and  oesophagus; 
but  the  ramuscule  of  Galien,  which  nearly  equals  the  superior  laryngeal  in  volume,  does  not 
anastomose  with  the  inferior  laryngeal ;  it  gives  a  large  branch  to  the  crico-arytaeiioid  muscle 
in  passing  to  its  surface,  and  then  leaves  the  larynx  to  the  inside  of  the  recunent,  descending 
on  the  trachea  as  far  as  the  entrance  to  the  chest.  In  that  cavity,  the  descending  branch  of 
the  superior  laryngeal  forms  two  divisions  that  communicate  with  the  ramuscules  of  various 
other  nerves  passing  into  this  region.  On  the  right  side,  the  largest  division  receives  a 
voluminous  branch  from  the  inferior  cervical  ganglion;  then  the  two  divisions  unite,  and  join 
the  pneumogastric  after  it  has  turned  round  the  brachial  trunk,  a  little  behind  the  point  of 
emergence  of  the  inferior  laryngeal. 

On  the  left  side  the  same  arrangement  is  found;  the  anastomoses  are  larger  and  more 
numerous  than  on  the  right  siie;  the  branch  follows,  in  an  inverse  direction,  the  course 
pursued  by  the  recurrent  nerve,  to  join  the  pneumogastric  at  the  part  where  the  recurrent 
originates  from  the  latter. 

In  this  course,  the  branch  gives  large  ramuscules  to  the  oesophagus  and  trachea ;  those 
distributed  to  the  former  either  pass  along  the  muscular  tunic  and  return  again  to  the  nerve, 
or  continue  along  the  surface  of  that  tube.  In  all  cases,  there  is  found  on  the  sides  of  the 
oesophagus  a  rich  plexus  formed  by  these  filaments,  as  well  as  by  those  coming  from  the 
pharyngeal  nerve. 

•  This  branch  also  offers  other  peculiarities.  Thus,  it  is  very  often  found  alongside  tlie 
laryngeal  nerve  for  some  distance,  and  sometimes  at  several  points.  When  this  happens  in 
the  upper  part,  at  tiie  larynx,  as  occurs  in  many  cases,  it  appears  to  have  an  anastomosis  as 
in  the  Ox ;  but  it  is  always  easy  to  separate  the  two  nerves,  even  in  fresh  specimens,  and  this 
separation  is  greatly  facilitated  if  the  piece  lias  been  steeped  in  water  acidulated  by  nitric  acid. 

In  the  cervical  portion,  the  pneumogastric  nerve  is  closely  united  to  the  sympathetic,  the 
separation  of  the  nerves  being  no  longer  possible  as  in  the  Horse  and  Ox. 

We  have  already  described  a  portion  of  the  inferior  laryngeal  nerve,  in  speaking  of  the 
tracheo-oesophageal  branch  of  the  superior  laryngeal.  Comparison  with  otiier  animals  requires 
that  we  should  transfer  the  latter  to  the  recurrent.  In  the  Dog,  the  inferior  laryngeal  rises  by 
two  distinct  branches,  a  short  distance  from  each  other, on  the  right  and  left  aides;  these  may, 
or  may  not,  lie  together  for  some  distance,  but  they  never  become  fused.  The  external  part  of 
the  nerve  receives  at  intervals  filaments  proceeding  from  the  superior  laryngeal  branch,  and  it 
rarely  gives  very  fine  twigs  to  tiie  trachea  and  oesophagus.  The  conimunicatious  with  the 
cardiac  and  tracheal  nerves  are  also  chiefly  made  by  the  tracheo-oesophageal  branch. 

The  bronchial  nerves  are  large  and  numerous. 

The  oesophageal  plexus,  which  is  furnished  by  the  nerves  of  the  same  name,  is  larger  and 
finer  than  in  the  Horse. 

There  is  nothing  to  note  particularly  in  the  termination  of  the  nerves  in  the  stomach. 

The  hypoglossal  gives  a  long  branch  that  passes  to  the  sides  of  the  larynx,  and  enters  the 
muscles  on  the  anterior  face  of  tlie  trachea. 

Rabbit. — We  shall  only  notice  some  differences  in  the  facial  and  pneumogastric  nerves. 

The  facial  gives  two  or  three  fine  branches  to  the  temporo-auricular  nerve,  on  its  sub- 
parotideal  course.  When  these  two  nerves  reach  the  anterior  border  of  the  parotid,  they  are 
parallel  to  and  superposed  on  each  other,  and  it  is  only  on  the  middle  of  tht;  masseter  that  the 
temporn-facial  plexus  is  formed.  Sometimes  the  branch  for  the  risorius  of  Santorini  is  detached 
before  the  formation  of  the  plexus. 

The  pneumogastric  has  a  gangliform  plexus,  like  that  of  Carnivora.  In  the  cervical  region, 
it  is  isolated  from  the  filament  of  the  sympathetic.  The  Rabbit  has  a  sensitive  heart-nerve, 
discovered  by  Ludwig  and  Cyon,  and  named  by  them  the  depressor  nerve  of  the  circulation.  It 
usually  begins  by  two  roots — one  furnished  by  the  pneumogastric,  the  other  by  the  superior 
laryngeal  nerve.  It  descends  along  the  neck,  beside  the  cord  of  the  sympatlietic,  receives — on 
entering  the  thorax — ramuscules  from  the  first  thoracic  ganglion,  and  is  soon  lost  in  the  substance 
of  the  heart.  The  root  from  the  superior  laryngeal  should  be  the  largest,  as  Toussaint  has 
always  found  it,  while  he  has  rarely  seen  that  which  is  detached  before  the  formation  of  the 
plexus. 


THE  NERVES. 


Comparison  of  the  Cranial  Nerves  of  Man  with  those  of  Animals. 

The  few  modifications  offered  by  the  cranial  nerves  of  Man,  when  compared  with  those  of 
animals,  are  dictated  by  the  dispositiou  of  tlie  [larts  and  organs  to  which  tliey  are  distributed. 

We  have  spoken  of  the  ulfactury  lobes  when  studying  the  brain,  so  that  we  need  not  again 
refer  to  them.     The  three  succeeding  nerves  offer  nothing  worthy  of  mention. 

Trigeminal  nerve. — This  has  the  same  origin  and  divisions  as  in  animals. 

The  frontal  nerve  of  the  ophthalmic  portion  divides  into  two  branches;  these  are  inflected 
upwards  on  the  margin  of  the  orbit,  and  distributed  to  the  skin  of  the  forehead.  These  two 
branches— well  developed  in  the  Dog— are  distinguished  as  internal  and  external.  The  latter 
anastomoses  with  a  brancli  of  the  facial.  TJie  nasal  nerve,  after  spreading  over  the  surface  of 
the  turbinated  bones  and  tiie  meatus,  gives  off  a  ramuscule  that  becomes  subcutaneous  in 

Fig.  462. 


NERVES   OF   THE   FACE   AND   SCALP. 

,  Attrahens  aurem  muscle;  2,  anterior  belly  of  occipito-frontalis ;  3,  auriculo-temporal  nerve; 
4,  temporal  branches  of  facial;  5,  attolens  aurem  muscle;  6,  supra-trochleav  (5th);  7,  posterior 
belly  of  occipito-frontalis ;  8,  supra-orbital ;  9,  retrahens  aurem  muscle;  10,  temporal  branch  of 
temporo-orbital ;  11,  small  occipital ;  12,  malar  branches  of  facial ;  13,  posterior  auricular  (7th)  ; 
14,  malar  branch  of  temporo-malar  (5)  ;  15,  great  occipital ;  16,  infra-orbital  branches  of  facial ; 
17,  facial;  18,  nasal;  19,  cervico-facial  division  of  7th  ;  20,  iufra-orbital ;  21,  branches  of  digastric 
and  stylo-hyoid  ;  22,  temporo-facial  division  of  7th  ;  23,  great  auricular ;  24,  buccal  branches  of 
facial;  25,  trapezius  muscle  ;  26,  buccinator  (5th)  ;  27,  splenius  capitis  ;  28,  masseter;  29,  sterno- 
mastoideus  ;  30,  superma.xillary  branches  of  facial  nerve  ;  31,  superficial  cervical ;  32,  mental ; 
33,  platysma  muscle  ;  34,  submaxillary  branches  of  facial  nerve. 


passing  between  the  inferior  border  of  the  nasal  bone  and  cartilage  of  the  nostril ;  this  is  the 
naeo-lobular  nerve. 

The  superior  maxillary  nerve  leaves  the  cranium  by  the  foramen  rotundum.  reaches  the 
suborbital  furrow,  and  spreads  over  the  face  by  suborbital  branches.  Like  thnt  of  animals,  it 
gives  rise  to  an  orbital  ramuscule,  and  posterior  and  anterior  dental  branches.  Differences 
appear  in  the  other  branches  which  are  furnished,  in  animflls,  by  the  superior  maxillarv  nerve; 
in  Man  these  branches  leave  Meckel's  ganglion.  The  filaments  leaving  this  ganglion  are; 
1.  The  pharyngeal  nerve  of  Bock,  which  is  distributed  in  the  upper  portion  of  the  mucous 
membrane  of  the  pharynx,  in  that  of  the  Eustachian  tube,  and  the  posterinr  orifice  of  the 
nasal  cavities.     2.  The  palatine  nerves — great  or  antenor— sent  to  the  mucous  membrane  of 


THE  CRANIAL    OR   ENCEPHALIC  NERVES. 


851 


the  anterior  portion  of  the  palate;  middle  palatine,  distributed  to  that  of  the  soft  palate,  and 
posterior  palatine,  tliat  goes  to  the  two  faces  of  the  soft  palate  and  its  muscles.  3.  The  nasal 
or  spheno-palatine  nerve. 


DISTRIBUTION   OF   THE    EIGHTH    PAIR   OF   NERVES   ON   LEFT   SIDE. 

1,  Gasserian  ganglion  of  5th  nerve ;  2,  internal  earotid  artery ;  3,  pharyngeal  branch  of  pneumo- 
gastric  ;  4,  glosso-pharyngeal  nerve  ;  5,  lingual  nerve  ;  6,  spinal  accessory  ;  7,  middle  constrictor 
of  pharynx;  8,  jugular  (internal)  vein  (cut);  9,  superior  laryngeal  nerve;  10,  ganglion  of  trunk 
of  pneumogastric  ;  11,  hypoglossal  nerve  on  hyoglossus  ;  12,  ditto  communicating  with  8th  and 
1st  cervical  nerve;  13,  external  laryngeal  nerve  ;  14,  second  cervical  looping  with  the  first;  15, 
pharyngeal  plexus  or  inferior  constrictor;  16,  superior  cervical  ganglion  of  sympattietic  ;  17, 
superior  cardiac  nerve  of  pneumogastric  ;  18,  third  cervical  nerve;  19,  thyroid  body  ;  20,  fourth 
cervical  nerve;  21,  21,  left  recurrent  laryngeal  nerve;  22,  spinal  accessory  communicating  with 
cervical  nerves;  23,  trachea  ;  24,  middle  cervical  ganglion  of  sympathetic;  25,  middle  cardiac 
nerve  of  pneumogastric;  26,  phrenic  nerve  (cut);  27,  left  carotid  artery;  28,  brachial  plexus; 
29,  phrenic  nerve  (cut);  30,  inferior  cervical  ganglion  of  sympathetic;  31,  pulmonary  plexus  of 
pneumogastric;  32,  thoracic  aorta;  33,  oesophageal  plexus  ;  34,  vena  azygos  superior ;  35,  vena 
azygos  minor  ;  36,  gangliated  cord  of  sympathetic. 


The  inferior  maxillary  nerve  closely  resembles  that  of  animals,  the  only  differences  consisting 
in:  1.  The  deep  middle   temporal  nerve  rising  direct  from  the  maxillary.     2.  The  lingual 


852  THE  NERVES. 

nerve  is  detached  near  the  base  of  the  cranium.  3.  The  superficial  temporal  uerve  fumishea — 
independently  of  the  filaments  uniting  it  to  the  facial — an  auriculo-temporal  branch  that 
ascends  iu  front  of  the  ear,  and  terminates  in  the  skin  of  the  temporal  region. 

In  Man,  there  is  annexed  to  the  fifth  pair  the  submaxillary  ganglion,  which  receives  a 
sensitive  branch  from  the  lingual,  a  motor  filament  from  the  chorda  tympani,  and  sympathetic 
filaments;  it  gives  off  several  emergent  filaments,  nearly  all  of  which  pass  into  the  maxillary 
gland.     There  is  nothing  to  say  of  the  internal  motores  ocuhrum. 

Facial. — In  its  collateral  branches,  the  facial  nerve  of  Man  is  absolutely  the  same  as  in 
animals.  It  has,  however,  a  brunch  not  described  in  them — the  ramuscule  of  Hirsch/eld,  which 
reaches  the  base  of  the  tongue,  where  it  is  distributed  by  mixing  with  the  glosso-pharyngeal. 
The  termination  much  resembles  that  of  the  Dog.  Two  principal  brandies  have  been  named 
the  temporo-facial  and  the  cervico-facial.  The  first  receives  the  superficial  temporal  nerve,  and 
describes  an  arch  from  which  are  detached  the  temporal,  frontal,  palpebral,  suborbital,  and 
buccal  ramuscules,  which  form  the  subparotideal  plexus.  The  second,  lodged  in  the  parotid 
gland,  passes  towards  the  angle  of  the  jaw,  where  it  anastomoses  with  the  cervical  plexus ;  it 
furnishes  the  inferior  buccal,  mental,  and  cervical  branches. 

Glosso-pharyngeal. — This  nerve  commences  and  terminates  as  in  Solipeds,  and  has  the  same 
relations.  It  furnishes  tlie  branches  of  the  digastric  and  stylo-hyoid  muscles,  the  filament  of  the 
stylo-glossus  muscle,  and,  finally,  the  tonailitic  ramuscules  that  form,  around  the  amygdala,  the 
tonsilar  plexus. 

Pneumogastric. — Formed  by  the  union  of  the  sensitive  roots,  the  pneumogastric  leaves  the 
cranial  cavity  bj'  the  posterior  foramen  lacerum  ;  in  the  interior  of  that  foramen  it,  shows  the 
jugular  ganglion ;  a  little  lower,  it  has  a  second  fusiform  enlargement— the  gangliform  plexus— 
which  is  found  in  the  Dog.  Here  it  receives  the  internal  branch  of  the  spinal  accessory,  or 
otherwise  its  motor  roots.  Beyond  this  gangliform  enlarjjement,  the  pneumogastric  is  placed 
a  little  within  the  sympathetic,  descends  along  the  neck,  enters  the  chest,  and  terminates  on 
the  stomach  and  in  the  solar  plexus.  The  relations  of  the  two  pneumogastrics  in  the  thoracic 
cavity  are  the  same  as  in  animals.  In  terminating  in  the  semilunar  ganglion,  the  two  pneu- 
mogastrics unite  and  form  an  arch  named  the  memorable  loop  of  Wrisberg. 

The  Viirious  anastomoses  of  the  pneumogastric  iu  Man  cflfer  nothing  particular. 

The  pharyngeal  branches  leave  the  gangliform  plexus,  and  are  constituted  by  the  filaments 
carried  to  the  pneumogastric  by  the  internal  root  of  the  spinal  accessory.  They  are  two,  three, 
or  four  in  number,  and  form  the  pharyngeal  plexus. 

The  superior  laryngeal  nerve  also  arises  from  the  gangliform  plexus,  and  oflfers,  as  in 
Ruminants,  a  Galien  branch  that  anastomoses,  end  to  end,  with  a  branch  of  tiie  inferior 
laryngeal.  The  external  laryngeal  is  furnished  by  this  nerve;  it  is  distributed  to  the  inferior 
constrictor  muscle  of  the  pharynx,  the  crico-thyroid  muscle,  and  the  mucous  membrane  of  the 
subglottic  portion  of  the  larynx  and  the  ventricle  of  the  glottis. 

The  recurrent  nerves  aflfect  a  distribution  analogous  to  that  already  made  known. 

The  pneumogastric  also  gives  cardiac,  pulmonary,  and  oesophageal  branches.  The  cardiao 
lie  beside  those  coming  from  the  sympathetic  and  recurrents,  and  enter  the  ganglion  of 
"Wrisberg,  situated  at  the  base  of  the  heart.  The  oesophageal  branches  are  remarkable  for 
their  number  and  complexity,  and  form  a  veritable  oesophageal  plexus.  The  gastric  branches 
are  also  very  numerous. 

Spinal  accessory, — It  presents  bulbous  roots  which  are  well  known,  and  medullary  roots 
which  usually  extend  to  the  fifth  cervical,  and  sometimes  to  the  first  dorsal.  After  its  exit 
from  the  posterior  foramen  lacerum,  it  divides  into  two  branches— an  internal  and  externaL 
The  internal  branch,  formed  by  the  bulbous  roots,  enters  the  gangliform  plexus  of  the  pneu- 
mogastric.    The  external  branch  comports  itself  as  in  animals. 

The  hypoglossal  resembles  that  of  Carnivora,  and,  like  it,  possesses  a  branch  for  th« 
hyo-thyroideus  and  genio-hyoideus. 


SPINAL  NERVES.  853 

CHAPTER  II. 

SPINAL  NERVES. 

"We  designate  as  spinal,  vertebral,  or  rachicUan  nerves,  those  which  emanate  from 
the  spinal  cord,  and  leave  the  vertebral  canal  by  the  intervertebral  foramina  to 
proceed  to  the  various  organs. 

They  are  estimated  at  42  or  43  pairs,  and  are  apportioned  as  follows  in  the 
five  regions  of  the  spine  :  cervical,  8  pairs  ;  dorsal,  17  pairs  ;  lumbar,  6  pairs ; 
sacral,  5  pairs  ;  and  coccygeal,  6  to  7  pairs. 

They  differ  from  the  cranial  nerves  in  closely  resembling  each  other  in  the 
fundamental  points  of  their  constitution.  All  proceed  from  the  lateral  aspects 
of  the  spinal  cord  by  two  orders  of  roots  :  one  motor,  the  other  sensitive.  In  all, 
these  two  roots  unite  into  a  very  short  trunk  in  passing  through  the  intervertebral 
foramen  ;  and  this  mixed  nerve  divides  almost  immediately  into  two  terminal 
branches — a  superior,  destined  to  the  spinal  muscles  and  the  integuments 
covering  them ;  the  other,  inferior,  passes  to  the  lateral  and  lower  parts  of  the 
trunk  or  to  the  limbs.  All  send,  from  their  inferior  branch,  one  or  more 
ramuscules  to  form  the  great  sympathetic. 

The  roots  of  the  spinal  nerves  olfer  everywhere  the  same  disposition ;  each 
nerve  is  formed  by  two  fasciculi  of  converging  filaments — superior  and  inferior — 
which  are  naturally  more  numerous  and  large  when  they  belong  to  voluminous 
trunks,  as  may  be  remarked  in  those  proceeding  from  the  two  bulbous  enlarge- 
ments of  the  spinal  cord.  The  common  axis  of  these  two  fasciculi  affects  a 
transverse  direction  in  nearly  all  the  spinal  pairs  ;  but  that  of  the  posterior 
nerves  inclines  more  backwards,  as  they  reach  the  terminal  extremity  of  the  cord. 

The  filaments  of  the  superior  fasciculi — or  sensitive  roots — are  larger  than  the 
others,  and  emerge  from  the  collateral  groove  on  the  spinal  cord.  They  may  be 
followed,  in  animals,  to  the  cells  of  the  superior  grey  cornua.  But  these  cells  are 
not  sufficiently  numerous  to  receive  all  the  fibres  of  the  superior  roots,  and  some 
of  these  pass  into  the  cells  of  Clarke's  columns. 

The  filaments  of  the  inferior  fasciculi — or  motor  roots — arise  opposite  the  pre- 
ceding, on  the  lower  face  of  the  cord,  at  a  short  distance  from  the  middle  line, 
and  on  the  limits  of  the  inferior  and  lateral  columns.  They  may  also  be  traced 
to  the  interior  of  the  cord,  as  far  as  the  inferior  grey  cornua. 

These  filaments  do  not  unite  to  form  their  common  trunk  until  after  they 
have  passed  through  the  dura  mater.  This  is  an  extremely  short  trunk  that 
occupies  the  corresponding  intervertebral  foramen,  and  presents  on  its  upper 
face  a  ganglionic  enlargement,  which  is  exclusively  placed  on  the  course  of  its 
sensitive  fibres  ;  the  motor  filaments  being  simply  laid  beside  them,  and  do  not 
mix  with  them  until  beyond  the  ganglion.  Immediately  after  this  union,  a  small 
filament  is  given  off  that  enters  the  spinal  canal  to  be  distributed  to  the  sinuses 
and  the  bodies  of  the  vertebra. 

After  leaving  the  meningeal  sheath,  the  radicular  fasciculi  of  the  nerves, 
furnished  by  the  terminal  extremity  of  the  spinal  cord,  run  a  somewhat  long 
course  in  the  sacral  canal,  before  finally  uniting  and  passing  into  the  tissues. 
The  common  fasciculus  they  collectively  form  at  the  posterior  extremity  of  the 
spinal  canal  is  named  the  cauda  equina. 

The  distributive  branches  of  the  spinal  nerves  cannot  be  considered  in  a 


854 


THE  NERVES. 


general  manner,  because  of  their  diversity, 
each  region  of  the  spine. 


We  will  study  them  successively  in 


Fig.  464. 


Article  I. — Cervical  Nerves  (8  Pairs). 

Superior  Branches. — The  Jirst  (the  suboccipital  of  Willis)  passes  through 
the  superior  foramen  of  the  atlas,  in  company  with  the  cerebro-spinal  artery. 
It  arrives  in  the  space  between  the  small  oblique  muscle  of  the  head  and  the 
posterior  straight  muscles,  and  divides  immediately  into  several  divergent 
branches,  which  are  distributed  to  the  three  above-named  muscles,  the  anterior 
extremity  of  the  complexiis,  and  the  cervico-  and  temporo- 
auricular  muscles.  The  ramuscule  sent  to  the  latter 
ascends  within  the  concha,  and  breaks  up  into  several 
filaments  that  supply  the  skin  of  the  external  ear. 

The  second  immediately  furnishes  some  ramuscules 
to  the  obliquus  capitis  posticus  muscle,  beneath  which  it 
is  placed,  as  well  as  to  the  anterior  oblique.  It  is  after- 
wards directed  backwards,  comporting  itself  like  the  suc- 
ceeding ones. 

These  diminish  in  volume  from  the  third  to  the  eighth. 
All  pass  through  the  intertransversales  muscle,  and 
divide  into  several  branches,  which  are  distributed  to  the 
muscles  and  integuments  of  the  superior  cervical  region. 
Among  these,  the  superficial,  which  are  almost  rudimentary 
in  the  two  last  pairs,  reach  the  inner  face  of  the  splenius. 
The  others,  deep  and  more  voluminous,  cross  the  semi- 
spiiialis  colli,  and,  dividing,  ascend  between  the  complexus 
and  cervical  ligament,  to  near  the  superior  border  of  that 
large  elastic  layer.  They  generally  intercommunicate  by 
several  filaments,  and  in  this  way  form  a  network  on  the 
inner  face  of  the  complexus,  which  Girard  named  the  deep 
cervical  plexus. 

Inferior  Branches. — These  branches  augment  in 
size  from  the  first  to  the  last,  and  separate  into  two 
perfectly  distinct  groups.  The  divisions  of  the  first  six 
cover  the  lateral  and  anterior  parts  of  the  neck,  as  well 
as  the  muscles  of  the  breast.  Usually  anastomosing  with 
each  other  by  long  communicating  branches,  they  in  this 
waj  form  a  vast  nervous  network  traversed  by  two  important  nerves — the  spinal 
accessory  and  cervical  filament  of  the  facial ;  this  is  the  superficial  cervical  plexus. 
The  other  two  are  united  with  the  preceding  by  a  filament  passing  between  the 
sixth  and  seventh,  soon  l)ecoming  confounded  with  each  other,  as  well  as  with 
the  two  first  branches  of  the  dorsal  region  ;  they  constitute — in  common  with  the 
latter — the  brachial  plexus. 

Without  saying  any  more  as  to  the  disposition  of  this  double  plexus,  we  will 
pass  to  the  particular  description  of  each  cervical  pair  of  nerves. 

First. — Deeply  situated  beneath  the  transverse  process  of  the  atlas,  this  nerve 
leaves  the  anterior  foramen  of  that  vertebra,  and  accompanies  the  occipital  artery 
and  vein  to  place  itself  immediately  between  the  rectus  capitis  anticus  minor  and 
rectus  lateralis  muscles.  It  then  crosses  the  rectus  capitis  anticus  major  and  the 
spinal  accessory  nerve,  which  it  separates  ;  and  arrives,  after  describing  a  slight 


GANGLION  OF  A  SPINAL 
NERVE  FROM  THE  LUM- 
BAR REGION  OF  A 
POPPY. 

a,  Superior  root ;  6,  in- 
ferior root;  c,  ganglion 
on    the    superior    root; 

d,  e,  junction  of  the 
fibres  from  the  inferior 
and  superior  roots  with 
those  comins;  from  the 
ganglion ;  d,  superior 
trunk   of  spinal  nerve  ; 

e,  its  inferior  trunk. 


CERVICAL  NERVES.  855 

curve  forward,  near  the  thyroid  gland,  finally  entering  the  subscapulo-hyoideus 
by  several  terminal  divisions. 

Near  its  origin,  this  inferior  branch  of  the  first  cervical  nerve  furnishes 
collateral  ramuscules  to  the  three  recti  muscles  of  the  head.  Lower,  it  is  in 
commimication  with  the  superior  cervical  ganglion  and  the  spinal  accessory 
nerve  by  several  filaments.  At  the  carotid  artery,  it  sends  forwards,  to  the  side 
of  the  larynx,  a  very  fine  branch  that  quickly  divides  into  two  ramuscules,  one 
of  which  joins  the  hypoglossal  nerve,  and  the  other  goes  to  the  thyro-hyoid 
muscle.  It  then  throws  off,  from  its  convex  side,  several  small  descending 
nerves,  all  of  which  are  destined  to  the  subscapulo-hyoid,  sterno-hyoid,  and 
thyroid  muscles. 

One  of  these  filaments,  joined  by  a  ramuscule  from  the  second  pair,  is  dis- 
tinguished for  its  great  length ;  it  may  be  followed  to  near  the  sternum,  where 
it  is  expended  in  the  fleshy  mass  common  to  the  four  mnscles  that  extend  from 
that  bone  to  the  larynx  and  os  hyoides.  Its  constant  disposition  should  obtain 
for  it  the  name  of  pre-cprviml  7ierve. 

Second. — This  descends  beneath  the  obliquus  posticus,  crossing  the  direction 
of  the  rectus  anticus  major,  and  ramifying  therein  by  numerous  branches.  We 
specially  indicate  :  1.  Those  furnished  to  the  latter  muscle,  and  which  are  the 
shortest  and  deepest  2.  The  atloid  loop,  a  long,  thick  superficial  branch,  which 
enters  the  anterior  portion  of  the  levator  humeri,  and  is  directed  forward  and 
upward  on  the  parotid  gland,  bending  round  the  transverse  process  of  the  atlas  ; 
this  ramuscule  gives  off  filaments  to  the  parotido-auricularis,  as  well  as  to  the 
panniculus  of  the  face,  and  terminates  in  two  branches  of  unequal  volume,  the 
largest  of  which  ascends  on  the  outer  side  of  the  concha,  and  the  other,  situated 
behind,  reaches  the  cervico-auricular  muscles.  3.  Another  superficial  branch, 
which  passes  over  the  jugular,  near  the  junction  of  the  glosso-facial,  and  divides 
into  two  ramuscules  ;  these  proceed  forward  with  the  submaxillary  facial  vein  to 
the  submaxillary  space,  where  they  are  distributed  to  the  skin  and  subcutaneous 
muscle.  4.  Anastomosing  filaments,  which  unite  it  to  the  two  branches  of  the 
spinal  nerve.  5.  Accessory  ramuscules  to  the  cervical  filament  of  the  facial 
nerve.  6.  Two  communicating  branches  which  pass  beneath  the  rectus  anticus 
major  :  one  going  to  the  first,  the  other  to  the  third  pair  of  nerves.  7.  A  deep 
branch  going  to  join  the  pre-cervical  filament  of  the  first  pair,  and  directly 
throwing  off  some  fine  divisions  to  the  subscapulo-hyoideus  muscle.  8.  A  last 
branch  that  arises  at  the  intervertebral  foramen,  and  passes  at  first — with  the 
vertebral  artery — into  the  posterior  foramen  of  the  second  vertebra,  and  after- 
wards those  of  the  succeeding  vertebrte,  to  enter  the  inferior  cervical  ganglion 
of  the  sympathetic  nerve,  receiving  on  its  course  filaments  from  the  third,  fourth, 
fifth,  sixth,  and  seventh  pairs. 

Third,  fourth,  fifth,  and  sixth. — Each  of  these  crosses  the  intertransversales 
colli  by  a  different  interstice  to  that  through  which  the  corresponding  superior 
branch  passes.  They  gain  the  inner  face  of  the  mastoido-humeralis,  where  they 
divide  into  deep  and  superficial  ramifications. 

The  first  are  distributed  to  the  deep  muscles  of  the  sides,  and  anterior  part  of 
the  neck  and  shoulders.  Among  them  ought  to  be  distinguished  those  which 
form  a  communication  between  the  four  pairs,  and  the  third  with  the  second. 
Veiy  long  and  thin,  these  filaments  lie  on  the  side  of  the  large  muscular  mass 
formed  in  front  of  the  cervical  vertebrae  by  the  rectus  anticus,  longus  colli,  and 
scalenus  muscles.     There  they  form  sometimes  arches,  and  at  other  times 


856  THE  NEBVE8. 

anastomoses  by  convergence.  Those  of  the  fifth  and  sixth  pairs,  uniting  at  the 
anterior  border  of  the  scalenus  with  a  branch  of  the  brachial  plexus,  constitute  the 
diaphrngmatic  {phrenic)  nerve,  which  will  be  noticed  hereafter. 

The  superficial  ramuscules  gain  the  external  surface  of  the  mastoido- 
humeralis  by  traversing  its  substance,  or  passing  between  its  two  portions. 
Much  more  numerous  and  larger  than  the  preceding,  they  are  distributed — in 
front — to  the  cervical  panniculus ;  behind,  to  the  trapezius ;  or  below,  to  the 
mastoido-humeralis  and  pectoralis  anticus  and  transversus.  Those  passing  to  the 
two  last  muscles  are  very  long  and  voluminous  ;  they  represent  the  acromial  and 
clavicular  branches  of  the  cervical  plexus  of  Man.  It  may  be  remarked  that  the 
posterior  filaments  generally  communicate  with  the  spinal  accessory,  while  the 
anterior  ones,  in  meeting  the  cervical  branch  of  the  facial  nerve  on  the  jugular, 
often  give  it  some  anastomosing  fibres. 

Seventh. — An  enormous  branch  comes  from  the  interstice  between  the  two 
portions  of  the  scalenus,  to  pass  entirely  into  the  brachial  plexus.  It  usually 
receives  an  anastomosing  twig  from  the  diaphragmatic  filament  furnished  by  the 
sixth  pair. 

Eighth. — This  is  thicker  than  the  preceding,  and  comports  itself  like  it.  It 
directly  furnishes  its  anastomotic  branch  to  the  inferior  cervical  ganglion. 

Aeticle  II. — DoESAL  Nerve  (17  Paies). 

These  nerves,  numbering  seventeen  pairs,  comport  themselves  in  an  extremely 
simple  and  almost  identical  manner  ;  so  that  their  description  is  not  nearly  so 
complicated  as  that  of  the  nerves  of  the  cervical  region. 

Superior  Branches. — They  present  two  principal  ramuscules  for  the  spinal 
muscles  and  the  skin  of  the  dorso-lumbar  region.  One  ascends  towards  the  summit 
of  the  spinous  processes  of  the  dorsal  vertebrae,  by  passing  between  the  semi- 
spinalis  and  longissimus  dorsi ;  the  other  is  directed  outwards,  in  traversing  the 
substance  of  the  latter  muscle. 

Inferior  Branches. — These  are  more  considerable  in  size  than  the  pre- 
ceding, and  descend  into  the  intercostal  spaces,  between  the  pleura  and  the 
internal  intercostal  muscles,  or  even  in  the  texture  of  these.  With  the  exception 
of  the  first,  the  arrangement  of  which  is  different,  they  all  pass  at  first  over  the 
head  of  the  posterior  rib  to  reach  the  convex  border  of  the  anterior  one,  and 
follow  it  to  the  extremity  of  the  intercostal  space. 

There  they  terminate  in  the  following  manner  :  those  of  the  sternal  ribs 
traverse  the  pectoral  muscles,  giving  filaments  to  these,  and  are  expended  in  the 
skin  of  the  subthoracic  region.  Those  of  the  asternal  ribs  enter  the  abdominal 
muscles,  passing  between  the  transversalis  and  rectus  abdominis  ;  they  also  give 
cutaneous  filaments  to  the  skin  of  the  abdomen. 

Near  their  origin,  the  inferior  branches  communicate  with  the  sympathetic, 
for  the  most  part,  by  several  filaments. 

In  their  course  they  furnish  numerous  fine  ramuscules  to  thf^  intercostal 
muscles,  and,  in  addition,  give  off — about  the  middle  of  their  length — a  very  thick 
division — the  perforating  intercostal  hranch,  which  traverses  the  costal  muscles 
and  descends  beneath  the  panniculus  carnosus,  ramifying  partly  in  that  muscle 
and  partly  in  the  skin.  The  most  anterior  perforating  branches  generally  anas- 
tomose with  the  subcutaneous  thoracic  branch  of  the  brachial  plexus. 

With  regard  to  the  first  dorsal  pair,  its  inferior  branch  enters  the  latter 
plexus  ;  but  it  nevertheless  furnishes  an  intercostal  branch,  always  extremely 


LUMBAR  NERVES.  857 

slender,  which  passes  over  the  external  intercostal  muscle  to  be  expended  in  its 
substance,  before  aiTiving  at  the  sternum.  The  second  pair  also  concurs  in  the 
formation  of  the  brachial  plexus,  though  only  by  a  small  branch. 

Article  III. — Lumbar  Nerves  (6  Pairs). 

Superior  Branches. — Distributed  to  the  spinal  muscles  and  the  integu- 
ments of  the  loins  and  croup,  these  are  larger  than  the  corresponding  branches 
of  the  dorsal  region,  but  present  an  analogous  disposition.  They  give  superior 
ramuscules  to  the  muscles  of  the  spine,  and  very  long  external  divisions  which 
pass  through  these  muscles,  to  be  distributed  to  the  skin  of  the  croup. 

Inferior  Branches. — The  /rs^— comprised  in  the  interval  separating  the 
last  rib  from  the  first  lumbar  transverse  process,  between  the  quadratus  lumborum 
and  the  psoas  magnus — passes  downwards  and  backwards  until  it  arrives  between 
the  transverse  and  internal  obUque  muscles  of  the  abdomen,  to  which  it  gives 
filaments,  and  is  finally  distributed  in  the  rectus  abdominis  muscle. 

Above  the  superior  border  of  the  internal  obhque  muscle,  it  furnishes  a  per- 
forating branch  to  the  skin  of  the  flank  and  the  posterior  part  of  the  panniculus 
carnosus. 

The  second,  disposed  in  the  same  manner  as  the  preceding,  follows  an  analogous 
course,  and  breaks  up  into  several  divisions  which  are  lost  in  the  internal  oblique 
muscle.  From  one  of  these  sometimes  emanates  a  slender  filament,  which  joins 
one  of  the  inguinal  nerves  of  the  third  pair.  We  must  not  overlook,  in  the 
enumeration  of  the  branches  emitted  by  this  second  pair  of  lumbar  nerves,  the 
two  perforating  branches  which  descend  in  front,  and  on  the  inside,  of  the  thigh, 
to  be  distributed  to  the  skin  of  the  flank  and  the  internal  crural  region. 

The  third  ^  also  passes  outwards,  above  the  psoas  muscles,  which  receive 
from  it  several  divisions,  and  ramifies  in  the  muscles  of  the  flank.  It  has  also 
perforating  nerves,  destined  to  the  inguinal  region,  and  these  comport  them- 
selves in  a  sufficiently  interesting  manner  to  merit  particular  mention.  They 
are  usually  three  in  number — an  internal  and  two  external  inguinal  nerves. 
The  three  pass  at  first  beneath  the  peritonemn,  and  are  directed  backwards, 
downwards,  and  outwards,  towards  the  inguinal  canal,  which  they  enter — one 
to  the  inside,  the  other  to  the  outside  of  the  spermatic  cord.  They  give  off 
some  filaments  to  the  cremaster  and  abdominal  muscles,  and  at  last  ramify 
in  the  envelopes  of  the  testicle,  the  sheath,  and  the  skin  of  the  inguinal  region. 
The  two  external  nerves  are  often  confounded  in  a  single  trunk,  on  their  arrival 
at  the  cremasteric  muscle.  The  disposition  they  affect  at  their  origin  is 
extremely  variable  ;  sometimes  they  have  each  a  distinct  commencement,  and 
separately  traverse  either  the  small  or  large  psoas  muscle,  or  the  space  between 
these  ;  and,  at  other  times,  the  internal  and  one  of  the  external  inguinal  nerves 
proceed  from  a  common  trunk  at  the  intervertebral  foramen,  the  second  external 
nerve  then  arising  alone  towards  the  external  border  of  the  psoas  magnus 
muscle.  Most  frequently,  the  internal  nerve  receives  a  branch  from  the  fourth 
pair,  and  it  is  even  sometimes  entirely  formed  by  that  branch.  This  variation 
in  arrangement  is  not,  however,  the  exclusive  appanage  of  the  inguinal  nerves  ; 
we  have  seen  the  third  pair  alone  furnish  these  three  nerves  and  the  filaments 
to  the  psoas  muscles,  without  being  prolonged  into  the  muscles  of  the  flank. 

The  fourth  ^  pierces  the  psoas  parvus  muscle,  and  enters  the  space  separating 

'  Representing  the  ahdomino-gen>tal  B.n(i  femoro-genital  branches  of  Man. 
*  The  femoro-cutaneous  branch  of  the  lumbar  plexus  of  Man. 


858  THE  NERVES. 

it  from  its  congener — the  psoas  magnus.  After  passing  between  the  peritoneum 
and  the  lumbo-iliac  aponeurosis,  it  arrives  below  the  angle  of  the  haunch,  and 
makes  its  exit  from  the  abdomen  ;  it  then  descends  within,  and  in  front  of,  the 
tensor  fascia  lata  muscle,  and,  accompanying  the  divisions  of  the  circumflex 
iliac  artery,  it  is  prolonged  to  the  stifle,  where  it  is  expended  in  the  skin.  At 
its  origin,  it  gives  :  1.  A  thick,  short  branch  to  the  psoas  magnus  muscle. 
2.  A  large  anastomosing  branch  which  concurs  in  the  formation  of  the  lumbo- 
sacral plexus.  3.  A  filament  that  joins  the  internal  inguinal  nerve  furnished  bj 
the  third  pair.  We  have  already  mentioned  that  this  nerve  sometimes  emanates 
entirely  from  the  fourth  pair. 

The  fifth  and  sixth — much  more  voluminous  than  the  preceding — unite,  and, 
with  the  three  first  sacral  pairs,  form  the  plexus  of  the  abdominal  limb. 

All  the  inferior  lumbar  branches  communicate  with  the  sympathetic  by 
several  filaments,  which  pass  across  the  fasciculi  of  the  psoas  parvus  muscle ; 
and  all  communicate  with  each  other — the  two  last  by  fusion  of  their  fibres, 
and  the  first  five  by  means  of  more  or  less  voluminous  anastomotic  branches, 
which  are  far  from  being  constant. 

Aeticle  IV. — Sacral  Nerves  (5  Pairs). 

We  describe,  as  sacral  nerves,  not  only  the  four  double  cords  which  escape 
by  the  lateral  foramina  of  the  os  sacrum,  but  also  the  nerve  that  passes  through 
the  intervertebral  foramen  between  that  bone  and  the  last  lumbar  vertebra. 

Superior  Branches. — These  are  small  ramuscules  that  pass  through  the 
supra-sacral  foramen,  reach  the  muscles  lodged  on  the  sides  of  the  sacral  spine, 
and  terminate  in  the  skin  of  the  croup. 

Inferior  Branches. — Thick  nerves,  which  diminish  in  volume  from  the 
first  to  the  fifth,  and  leave  the  sacral  canal  to  pass  downwards  and  backwards  on 
the  sides  of  the  pelvic  cavity. 

The  first,  second,  and  third  are  directed  towards  the  great  sciatic  opening, 
and  are  united  into  a  wide  nervous  band  that  constitutes  the  pelvic  portion  of 
the  lumbo-sacral  plexus,  to  be  described  at  another  time. 

The  fourth  and  fifth  course  along  the  side  of  the  pelvic  cavity — in  the 
texture  of  the  sacro-sciatic  ligament,  or  even  within  it ;  united  at  their  base  by 
an  anastomosing  filament,  they  do  not  usually  communicate — at  least,  in  a  direct 
manner — with  the  fasciculus  formed  by  the  three  first  pairs. 

The  fourth  constitutes  the  internal  pudic  nerve,  which  passes  between  the 
two  roots  of  the  corpora  cavernosa  in  bending  round  the  ischial  arch,  where 
it  lies  nearly  alongside  its  fellow  of  the  opposite  side.  This  nerve  afterwards 
descends  on  the  dorsal  border  of  the  penis,  in  the  midst  of  the  magnificent 
venous  plexus  of  that  organ,  describing  flexuosities  which  allow  it  to  adapt 
itself  to  the  elongation  of  the  penis.  Arriving  at  the  extremity  of  the  organ, 
it  terminates  in  numerous  divisions  in  the  proper  erectile  tissue  of  this  part, 
or  in  the  mucous  membrane  covering  it.  On  its  course  it  emits  very  long 
flexuous  branches,  the  ultimate  ramifications  of  which  enter  the  corpora  caver- 
nosa, or  go  to  the  urethral  canal.  Before  leaving  the  pelvis,  it  gives  off",  behind, 
two  thin  ramuscules  to  the  muscles  and  skin  of  the  perineo-anal  region.  These 
ramuscules,  like  the  principal  trunk,  receive  anastomotic  filaments  from  one  of 
the  ischio-muscular  branches  of  the  lumbo-sacral  plexus. 

The  fifth  is  the  anal  or  hcemorrhoidal  nerve.     It  passes  backward,  above 


DIAPHRAGMATIC  NERVE.  859 

the  preceding,  and  is  distributed  to  the  sphincter  ani  muscle  and  the  surround- 
ing integuments.  Before  quitting  the  pelvis,  it  gives  a  ramuscule  to  the 
levator  ani. 

The  five  inferior  sacral  branches  emit,  near  their  origin,  a  more  or  lesa 
slender  filament  that  proceeds  to  the  pelvic  or  hypograstic  plexus.  The  anasto- 
mosing divisions,  through  which  they  communicate  with  the  sympathetic  chain, 
are  generally  thick,  short,  and  multiple. 

Aeticle  v.— Coccygeal  Neeves  (6  to  7  Paies). 

In  the  coccygeal  region  are  found  two  pairs  of  nerves — one  placed  beneath 
the  compressor  muscle  of  the  tail,  the  other  below  the  curvator  muscle.  These 
two  nerves  extend  to  the  extremity  of  the  tail,  throwing  off  on  their  track  some 
muscular  and  cutaneous  filaments.  They  are  formed  by  the  superior  and  inferior 
branches  of  the  coccygeal  nerves,  which  gradually  amalgamate  to  form  the  two 
nerves. 

These  coccygeal  branches  are  six  or  seven  in  number,  and  very  distinct ;  they 
diminish  in  volume  from  the  first  to  the  last.  The  first  only  gives  a  slender 
filament  for  the  formation  of  each  coccygeal  trunk  ;  it  is  chiefly  expended  in  the 
integuments  and  muscles  at  the  base  of  the  tail. 

Aeticle  VI. — Composite  Neeves  foemed  by  the  Infeeioe  Beanches  op 
THE  Spinal  Neeves. 

We  already  know  that  these  nerves  represent  three  groups  :  1.  The  dia- 
vhragmatic  nerve.  2.  The  brachial  plexus.  3.  The  lumbosacral  plexus.  They 
will  be  studied  in  this  order. 

Diaphragmatic  (or  Phrenic)  Nerve. 

The  diaphragmatic  nerve  (the  internal  respiratory  nerve  of  Bell)  is  formed  by 
two  principal  branches,  and  a  small  accessory  ramuscule,  the  presence  of  which 
is  not  constant.  The  latter  comes  from  the  fifth  cervical  pair ;  the  two  others 
proceed,  one  from  the  next  pair,  the  other  from  the  brachial  plexus.  The  branch 
from  the  sixth  pair  pierces  the  inferior  scalenus  muscle  from  within  to  without, 
gives  off  a  filament  to  the  brachial  plexus,  and  descends  obliquely  backAvards  to 
the  surface  of  the  muscle  it  passes  through,  to  unite — at  the  entrance  to  the 
chest — with  the  branch  of  that  plexus.  This  latter  branch,  generally  shorter  and 
thicker,  comes  exclusively  from  the  seventh  cervical  pair. 

The  trunk  of  the  diaphragmatic  nerve,  formed  in  this  manner,  passes  into  the 
thorax  after  receiving  the  branch  of  the  fifth  pair — when  it  exists — passes  within 
the  axillary  artery,  along  with  the  pneumogastric  nerve,  and  often  at  this  point — 
if  not  always — obtains  a  filament  from  the  sympathetic.  It  then  gains  the  side 
of  the  base  of  the  heart,  passing  beneath  the  pleura,  and  finally  attains  the  tendi- 
nous centre,  after  a  course  of  at  least  eight  inches  between  the  two  layers  of  the 
posterior  mediastinum — the  left  nerve  being  in  the  mediastinum  proper,^  while  that 
of  the  right  side  lies  in  the  special  serous  partition  for  the  posterior  vena  cava. 

'  Lesbre  has  found,  in  an  Ass,  an  anomaly  in  the  course  of  the  left  diaphragmatic  nerve. 
It  passed  directly  from  the  base  of  the  heart  to  the  anterior  face  of  the  diaphragm,  being  sus- 
tained in  the  middle  of  the  corresponding  portion  of  the  pleural  cavity  by  a  special  fold, 
analogous  to  that  of  the  posterior  vena  cava  in  the  right  pleura. 


SCO  TEE  NERVES. 

Even  before  its  aiTival  at  the  tendinous  centre,  this  nerve  divides  into 
several  branches,  the  ramifications  of  which  pass  to  the  sides  of  the  crura  of  the 
diaphragm. 

Brachial  Plexus. 

This  plexus  comprises  an  enormous  fasciculus  of  nerves,  situated  between 
the  thoracic  parietes  and  the  inner  face  of  the  anterior  limb,  formed  by  the 
inferior  branches  of  the  sixth,  seventh,  and  eighth  cervical,  and  the  two  first 
dorsal  pairs ;  they  are  principally  sent  to  the  muscles  and  integuments  of  that 
limb. 

Mode  of  constitution. — The  sixth  cervical  pair  only  assists  in  the  fomiation 
of  this  plexus,  by  the  slender  filament  from  its  diaphragmatic  branch ;  but  the 
next  two  are  entirely  devoted  to  it,  as  well  as  the  first  dorsal,  with  the  exception 
of  a  very  thin  ramuscule,  which  constitutes  the  first  intercostal  nerve.  The  root 
furnished  by  the  second  dorsal  pair  only  represents  a  very  small  part  of  its 
inferior  branch,  the  other  portion  forming  a  somewhat  voluminous  intercostal 
nerve. 

The  various  branches  converge  towards  each  other,  and  gain  the  space 
between  the  two  portions  of  the  scalenus  muscle  (if  we  consider  it  as  one),  where 
they  unite,  and  become  confounded  into  a  single  fasciculus  by  sending  filaments 
and  ramuscules  to  each  other ;  this  fasciculus  soon  separates  into  a  certain 
number  of  divisions,  the  disposition  of  which  will  be  referred  to  presently.  It 
will  be  remarked  that  the  intercrossing  of  the  branches  composing  the  brachial 
plexus  does  not  occur  in  a  confused  and  irregular  fashion,  and  if  the  reticulation 
of  the  ramuscules  passing  from  one  to  another  does  not  take  place  in  a  constant 
manner,  it  is,  at  any  rate,  far  from  being  inextricable.  It  is  easy  to  follow  the 
filaments  from  any  pair  of  nerves  for  a  certain  distance  in  the  divisions  given 
off  by  the  brachial  plexus,  especially  after  maceration  in  dilute  nitric  acid.  This 
originating  fasciculus  of  the  brachial  plexus  is  very  wide  and  short.  It  is  at 
first  comprised  between  the  superior  portion  of  the  scalenus  (or  superior  scalenus) 
and  the  longus  colU.  In  its  course  between  the  two  portions  of  that  muscle, 
it  bends  round  the  first  rib  by  its  posterior  border,  and  is  related  inwardly  to  the 
vertebral  artery  and  vein,  as  well  as  to  the  vertebral  nerve-filament  proceeding 
to  the  sympathetic,  and  accompanying  these  vessels. 

3Iode  of  distribution. — Immediately  after  leaving  the  interspace  in  the 
scalenus,  the  brachial  plexus  arrives  beneath  the  shoulder,  near  the  scapulo- 
humeral angle.  There  it  divides  into  a  certain  number  of  branches,  amongst 
which  it  is  impossible  to  distinguish  the  terminal  divisions  and  collateral 
ramuscules.  Without  noticing  this  distinction,  however,  we  will  describe  them 
in  succession,  commencing  with  those  that  pass  to  the  trunk,  and  afterwards 
those  which  are  destined  for  the  limb.  The  latter  will  be  examined  in  the 
following  order  :  first,  the  shortest  branches,  or  those  which  proceed  to  the 
upper  parts  of  the  member;  and  next,  the  longest  branches,  or  those  passing 
to  the  foot. 

All  these  divisions  are  named  and  classified  in  the  following  enmneration  : — 


BRACHIAL  PLEXUS. 


861 


Name. 

Origin. 

A.  Branches  to  the  Body. 

1.  Diapliragmatic  (phrenic)  branches. 

2.  Levator  anguli  scapulae  and  rhoniboideus  branch. 

3.  Serratus  magims,  or  superior  thoracic  branch. 

4.  Pectoral  or  inferior  thoracic  branches. 

5.  Subcutaneous  thoracic  branch. 

6.  Latissimus  dorsi  branch. 

5th,  6th,  and  7tii  cervical  pairs. 
6th  cervical  pair. 
6th  and  7th  cervical  pairs. 
6tii  and  7th  cervical  pairs. 
1st  and  2nd  dorsal  pairs. 
8th  cervical  pair. 

B.  Branches  to  the  Shouldeb. 

7.  Circumflex  or  axillary  nerve. 

8.  Teres  major  branches. 

9.  Subscapular  branches. 
10.  Supra-scapular  nerve. 

8th  cervical  pair. 
8th  cervical  pair. 
7th  cervical  pair. 
6tii  and  7th  cervical  pairs. 

C.  Branches  to  the  Arm  and  Fore-arm. 

11.  Anterior  brachial  or  musculo-cutaneous  nerve. 

12.  Musculo-spiral  or  radial  nerve. 

7th  and  8th  cervical  pairs. 
1st  dorsal  nerve. 

D.    Branches  to  the  Forearm  and  Foot. 

13.  Ulnar  or  cubito-cutaneous  nerve. 

14.  Median  or  cubito-plantar  nerve. 

Ist  and  2nd  dorsal  pairs. 
8th    cervical,   and    1st  and    2nd 
dorsal  pairs. 

Preparation  of  the  Brachial  Plexus. — The  animal  is  placed  in  the  first  position,  and 
slightly  inclined  to  one  side  by  allowing  one  of  the  anterior  limbs  to  hang  unrestrained.  The 
pectoral  muscles  are  then  excised  close  to  their  insertion  in  the  unfixed  limb,  and  turned 
upwards,  maintaining  them  in  this  position  by  the  chain  tentacula  which  are  attached 
superiorly  to  a  band  that  unites  the  extremities  of  the  two  suspensory  diagonal  bars.  Care 
should  be  taken  to  separate  the  pectoralis  magnus  from  the  panniculis,  in  allowing  the  latter 
to  fall  on  the  table  along  with  the  limb.  By  tearing  through  the  considerable  mass  of  con- 
nective tissue  surrounding  the  nerves  of  the  brachial  plexus,  these  soon  appear,  and  may  be 
isolated  with  the  greatest  facility.  It  is  advisable,  in  this  dissection,  to  preserve  the  arteries; 
and  it  is  also  of  importance  to  leave  the  perforating  intercostal  branches  intact,  in  order  to 
observe  the  anastomoses  of  these  with  the  subcutaneous  thoracic  division. 

In  this  operation,  the  anterior  limb  is  very  much  separated  from  the  trunk,  and  the 
relations  of  the  nerves  are  necessarily  more  or  less  changed;  but  it  exhibits  the  whole  of 
the  plexus  in  the  most  perfect  manner. 

To  trace  the  divisions  of  the  principal  nerves  from  tiiis  plexus,  a  limb  enti|gly  removed 
from  the  body  is  made  use  of,  and,  if  possible,  with  the  arteries  injected.  The  ne^es  are  then 
found  in  their  natural  relations,  and  can  be  more  readily  dissected.  Figs,  465,  466  will 
guide  the  student  in  looking  for  these  nerve-divisions. 

1.  Diaphragmatic  Branches. 

See  the  description  of  the  diaphragmatic  nerve  above. 

2.  The  Levator  Anguli  Scapula  and  Rhomboideal  Branch  (Fig.  465,  7). 

Entirely  furnished  by  the  sixth  cervical  pair,  this  branch  is  directed  upwards 
to  the  surface  of  the  levator  anguli  scapulge.  It  soon  divides  into  several  fila- 
ments, which  are  wholly  expended  in  the  substance  of  that  muscle,  the  serratus 
magnus,  and  the  rhomboideus.  The  filament  supplying  the  latter  is  slender 
and  very  long,  and,  to  reach  its  destination,  passes  through  the  levator  anguli 
scapulas. 

3.  Serratus  Magnus,  or  Superior  Thoracic  Branch  (Fig.  465,  8). 

This  very  remarkable  branch  proceeds,  by  two  principal  portions,  from  the 
fasciculus  common  to  all  the  divisions  of  the  brachial  plexus — one  emanating 

57 


862  THE  NERVES. 

from  the  sixth  cervical  pair  ;  the  other  from  the  seventh,  and  always  traversing 
the  last  fasciculus  of  the  superior  scalenus  before  joining  the  first.  The  single 
branch  resulting  from  the  union  of  these  two  roots  is  thin  and  very  wide.  It 
passes  back  to  the  surface  of  the  serratus  magnus,  crossing  the  direction  of  its 
fibres,  and  is  expended  in  its  substance,  sending  regularly  arranged  ramifications 
upwards  and  downwards. 

This  is  the  respiratory  nerve  of  Bell. 

4.  Pectoeal,  or  Inferior  Thoracic  Branckes. 

Five  principal  are  distinguished  : — 

1.  One  emanating  from  the  sixth  and  seventh  cervical  pairs — particularly  the 
former — and  passing  to  the  internal  face  of  the  anterior  deep  pectoral  muscle, 
to  ramify  exclusively  among  its  fibres,  after  dividing  into  two  branches  :  an 
anterior,  short  and  thick,  and  a  posterior,  long  and  slender  (Fig.  465,  10). 

2.  A  second  branch,  arising  from  the  anterior  brachial  and  cubito-plantar 
(or  median)  nerves,  by  two  roots,  which  join  in  forming  an  arch  beneath  the 
axillary  artery. 

It  passes  between  the  anterior  and  posterior  deep  pectoral  muscles,  and 
terminates  in  the  superficial  one,  after  furnishing  some  ramuscules  to  the 
posterior  deep  pectoral  by  means  of  a  long  thin  filament,  which  is  carried  back 
to  the  external  surface  of  that  muscle  (Fig.  465,  11). 

3.  The  other  three,  passing  to  the  posterior  deep  pectoral  muscle,  generally 
come  from  the  trunk  that  constitutes  the  subcutaneous  thoracic  branch.  Com- 
prised between  the  serratus  magnus  and  posterior  deep  pectoral,  they  are 
directed  downward  and  backward,  and  enter  the  latter  muscle.  One  of  them — 
longer  and  thicker  than  the  other — follows  the  course  of  the  spur  vein. 

5.  Subcutaneous  Thoracic  Branch  (Fig.  465,  9). 

This  is  a  very  remarkable  nerve,  arising  from  the  brachial  plexus  by  a  trunk 
common  to  it  and  the  ulnar  nerve.  Placed  at  first  to  the  inside  of  that  nerve, 
it  soon  leaves  it  to  pass  backward  to  the  internal  face  of  the  caput  magnum  and 
the  panniculus  carnosus.  In  its  long  com'se,  it  acts  as  a  satellite  to  the  spur 
vein,  above  which  it  is  situated.  It  may  be  followed  to  the  flank,  where  its 
terminal  divisions  are  lost  in  the  substance  of  the  panniculus  muscle.  Those  it 
gives  off  are  also  destined  to  that  muscle  ;  they  anastomose  with  the  majority  of 
the  perforating  intercostal  nerves,  forming  an  elaborate  network  on  the  inner 
face  of  the  panniculus. 

One  of  its  branches,  along  with  a  voluminous  perforating  nerve,  bends  round 
the  inferior  border  of  the  latissimus  dorsi,  and  passes  forward  to  enter  the 
scapulo-humeral  portion  of  the  panniculus. 

6.  Latissimus  Dorsi  Branch  (Fig.  465,  6). 

Formed  of  fibres,  the  larger  portion  of  which  come  from  the  eighth  cervical 
pair,  this  branch  proceeds  backwards  and  upwards  to  the  internal  face  of  the 
latissimus  dorsi,  and  is  soon  expended  in  that  muscle.     It  is  long  and  thick. 

7.  Circumflex  or  Axillary  Nerve  (Fig.  465,  13). 

Somewhat  considerable  in  voliune,  this  nerve  is  furnished  directly  by  the 
eighth  cervical  pair.     It  passes  backward  and  do^vnwa^d  on  the  internal  face  of 


;ig.  465. 


NERVES   OF    THE    BRACHIAL    PLEXUS. 

1,  Diaphragmatic  branch  of  the  sixth  cervical  pair, 
^     branch  to  the  brachial  plexus  ;  2,  seventh  cervical  pai 

eio-hth  cervical  pair  ;  4,  first  dorsal  pair  ;  5,  second  dorsal  pair  ; 
6,  great  dorsal  branch;  7,  levator  anguli  scapulae  and  rhom- 
boideal  branch  ;  8,  superior  thoracic  branch  ;  9,  subcutaneous 
thoracic  branch,  giving  rise,  near  its  origin,  to  the  three  in- 
ferior thoracic  branches;  10,  11,  two  other  inferior  thoracic 
branches;  12,  nerve  of  the  teres  major;  13,  axillary  nerve; 
14,  subscapular  nerves  ;  15.  supra-scapular  nerve ;  16,  radial 
nerve;  17,  anterior  brachial  nerve;  18,  ulnar  nerve;  19,  its 
internal  cutaneous  branch  ;  20,  median  nerve  ;  21,  its  mus- 
culo-cutaneous  branch ;  22,  22,  22,  superficial  ramuscules  of 
iiuit  branch.     A,  Humeral  artery  ;  b,  posteripr  radial  artery. 


EXTERNAL   NERVES   OF   THE    ANTERIOR   LIMB. 

Supra-scapular  nerve  ;  2,  axillary  nerve  ;  3,  radial 
nerve;  4,  superficial  ramuscuJe  of  the  musculo- 
cutaneous nerve  ;  5,  ulnar  nerve  ;  6,  its  terminal 
cutaneous  branch.     A,  Anterior  radial  artery. 


864  THE  NERVES. 

the  subscapularis  muscle,  to  the  intei-stice  between  it  and  the  teres  major,  where 
it  crosses  the  subscapular  artery.  It  proceeds  behind  the  scapulo-humeral 
articulation,  along  with  the  circumflex  artery,  entere  between  the  teres  minor 
and  the  caput  magnum  and  medium,  and,  arriving  beneath  the  deltoid,  it 
divides  into  several  diverging  branches,  destined  to  the  teres  minor,  deltoid, 
mastoido-humeralis,  and  even  to  the  integuments  covering  the  anterior  region 
of  the  arm. 

Before  entering  the  space  that  lodges  the  subscapular  artery,  it  sends  filaments 
to  the  scapulo-humeralis  and  gracilis  muscle. 

8.  Nerve  of  the  Teres  Major  (Fig.  465,  12). 

This  arises  from  the  eighth  cervical  pair — like  the  preceding — by  the  one 
trunk,  and  passes  backward,  at  first  on  the  subscapularis  muscle,  then  on  the 
adductor,  in  the  substance  of  which  it  disappears  by  numerous  filaments. 

9.  Subscapular  Branches  (Fig.  465,  14). 

These  branches  are  two  in  number,  and  are  generally  derived  from  the  trunk 
of  the  seventh  pair.  After  a  short  course  backwards,  they  divide  into  several 
ramuscules,  which  pass  among  the  fibres  of  the  subscapularis  muscle. 

10.  Supra-scapular  Nerve  (Fig.  465,  15). 

Very  short  and  thick,  this  nerve  is  formed  by  the  sixth  and  seventh  cervical 
pairs.  After  a  brief  course  backwards,  between  the  levator  anguli  scapulae  on 
the  one  side,  and  the  anterior  deep  pectoral,  prescapularis,  and  supra-spinatus  on 
the  other,  it  gains  the  space  between  the  latter  muscle  and  the  subscapularis, 
and  enters  it  a  little  above  the  supra-scapular  artery.  It  is  then  carried  to  the 
external  face  of  the  scapula,  after  bending  round  the  anterior  border  of  that 
bone,  passes  across  the  acromion  spine,  and  ascends  to  the  infra-spinous  fossa,  to 
expend  itself  in  the  muscle  occupying  this  space.  On  its  passage  beneath  the 
supra-spinatus  muscle,  it  gives  it  several  ramuscules. 

11.  Anterior  Brachial  or  Musculo-cutaneous  Nerve  (Fig.  465,  17). 

This  nerve  proceeds  from  the  seventh  and  eighth  cervical  pairs,  descends  to 
the  internal  face  of  the  scapulo-humeral  articulation,  and  meets  the  axillary 
artery,  which  it  crosses  outwardly,  at  an  acute  angle.  It  then  joins  the  median 
nerve  by  a  large  short  branch,  that  passes  beneath  the  artery  and  forms  a  loop 
around  it ;  descending  in  front  of  the  median  nerve,  to  the  bifurcation  of  the 
coraco-humeralis,  it  insinuates  itself  between  the  two  branches  of  that  muscle, 
and,  breaking  up  into  several  ascending  and  descending  ramuscules,  enters  the 
substance  of  the  biceps.  It  also  furnishes  filaments  to  the  coraco-humeralis, 
before  its  passage  between  the  two  branches  of  that  muscle.  Besides  this,  it 
concurs,  by  a  small  branch,  in  the  formation  of  one  of  the  anterior  thoracic  nerves. 

12.  Radial  (or  Musculo-spiral)  Nerve  (Figs.  465,  16  ;  466,  3). 

This  is  certainly  the  largest  nerve  furnished  by  the  brachial  plexus.  It  arises 
chiefly  from  the  first  dorsal  pair,  and  is  directed  backwards  and  downwards,  on 
the  inner  face  of  the  subscapularis  and  teres  major  muscles,  crossing  their 
direction.     In  this  portion  of  its  course,  it  proceeds  parallel  to  the  humeral 


TEE  BEACH  I AL   PLEXUS.  865 

artery,  from  which  it  is  separated  by  the  ulnar  nerve.  Arriving  at  the  deep 
humeral  artery — which  it  leaves  on  the  outside — it  passes  behind  the  humerus  with 
the  divisions  of  that  artery,  and  enters  between  the  caput  magnum  and  brachialis 
anticus.  After  creeping  along  the  posterior  border  of  the  latter  muscle,  it  gains 
the  anterior  face  of  the  ulna-radial  articulation,  where  it  is  covered  by  the  two 
principal  extensors  of  the  metacai-pus  and  the  phalanges,  and,  meeting  the  radial 
artery,  accompanies  it  on  to  the  oblique  extensor  of  the  metacarpus.  There  it 
terminates  by  two  branches,  which  enter  the  texture  of  that  muscle. 
In  its  course,  it  successively  gives  off — 

1.  Before  leaving  the  internal  face  of  the  limb,  to  pass  beneath  the  mass  of 
extensor  muscles  of  the  forearm,  a  very  thick  fasciculus,  composed  of  several 
branches — descending  and  ascending.  The  latter  bend  round  the  terminal 
tendon  common  to  the  latissimus  dorsi  and  teres  major,  to  become  lost  in  the 
body  of  the  great  extensor ;  the  others  reach  either  the  long  and  middle 
extensors,  or  the  inferior  portion  of  the  principal  muscle — the  large  extensor. 

2.  Behind  the  arm,  filaments  to  the  caput  medium  and  anconeus,  and 
several  cutaneous  ramuscules,  disengaged  from  beneath  the  former  muscle, 
that  descend  beneath  the  skin  on  the  anterior  face  of  that  part. 

3.  In  the  antibrachial  region,  branches  to  the  extensor  metacarpi  magnus 
and  flexor  metacarpi  externus,  and  the  two  extensors  of  the  digit. 

In  brief,  we  see  that  the  radial  nerve  is  distributed  to,  and  therefore 
stimulates,  the  whole  mass  of  the  extensor  muscles  of  the  forearm  and  foot, 
besides  a  flexor  of  the  latter  ;  and  that  it  endows  the  integument  of  the  anterior 
antibrachial  region  with  sensibility. 

13.  Ulnar  or  Cubito-cutaneous  Nerve  (Figs.  465,  18  ;  466,  5). 

Chiefly  formed  by  fibres  from  the  dorsal  pairs,  this  nerve — less  considerable  in 
volume  than  the  preceding — passes  backward  and  downward,  and  places  itself 
behind  the  humeral  artery,  which  it  accompanies  to  below  the  origin  of  the  deep 
humeral.  After  crossing  the  latter  vessel,  it  passes  between  the  scapulo-ulnaris 
and  caput  parvum,  and  gains  the  inner  side  of  the  elbow,  running  over  the 
epicondyle,  below  the  ulnar  band  of  the  oblique  flexor  of  the  metacarpus.  It 
follows  the  posterior  border  of  that  muscle  to  near  the  pisiform  bone,  where  it 
terminates  by  two  branches.  In  the  latter  part  of  its  course,  it  lies  beneath  the 
antibrachial  aponeurosis,  accompanied  by  a  division  of  the  epicondyloid  artery. 

One  of  the  two  branches — the  cutaneous  (Fig.  466,  6) — crosses  the  space 
between  the  terminal  tendons  of  the  external  and  obhque  flexor  muscles  of  the 
metacarpus,  as  well  as  the  antibrachial  aponeurosis,  to  expend  itself  in  several 
ascending  horizontal  and  descending  filaments,  beneath  the  skin  of  the  forearm, 
the  anterior  face  of  the  knee,  and  the  external  side  of  the  cannon.  The  other 
branch,  with  a  ramuscule  from  the  median  nerve,  constitutes  the  external  plantar 
nerve. 

In  its  course,  the  ulnar  nerve  gives  off  two  fasciculi  of  collateral  branches. 
The  first  (Fig.  465,  19)  is  detached  from  the  principal  trunk  a  little  above  the 
epicondyloid  artery,  and  passes  backward  and  downward  between  the  scapulo- 
ulnaris  and  the  anterior  superficial  pectoral — supplying  some  filaments  to  the 
latter — traverses  it  to  become  subcutaneous,  and  to  be  distributed  to  the  skin  of 
the  forearm,  beneath  the  elbow  {internal  brachial  cutaneous).  The  second  arises 
at  the  epicondyle,  and  is  destined  to  all  the  muscles  of  the  posterior  antibrachial 
region,  except  the  external  and  internal  flexors  of  the  metacarpus. 


866  THE  NERVES. 

14.  Median  or  Cubito-plantar  Nerve  (Fig.  465,  20). 

This  nerve  is  composed  of  fibres  coming  from  the  dorsal  and  eighth  cervical 
pairs.  It  is  detached  from  the  posterior  part  of  the  trunk  of  the  plexus  and 
proceeds  towards  the  axillary  artery,  where  it  forms  an  anastomosis  with  the 
anterior  brachial  nerve,  through  the  loop  already  noticed  when  describing  that 
nerve  as  being  formed  by  filaments  passing  from  one  cord  to  the  other,    x 

Leaving  this  point,  it  is  placed  in  front  of  the  humeral  artery,  and  accom- 
panies it  to  its  terminal  bifurcation  ;  then  it  continues  to  descend  on  the  inner 
face  of  the  limb,  along  with  the  principal  branch  of  that  artery — the  posterior 
radial — until  it  reaches  the  ulnar  articulation,  where  it  lies  against  the  internal 
ligament  of  that  joint,  and  crosses — at  a  very  acute  angle — the  direction  of  its 
satelUte  vessel  to  become  posterior.  This  position  it  inverts  below  the  articu- 
lation, when  it  assumes,  and  preserves  for  the  greatest  part  of  its  extent,  its 
antibrachial  course,  remaining  always  a  little  more  superficial  than  the  artery. 
Above  the  lower  third  of  the  forearm,  it  bifurcates  to  form  the  plantar  nerves. 

In  its  course,  this  nerve  successively  furnishes — 

1.  Before  its  arrival  on  the  axillary  artery,  one  of  the  originating  branches  of 
the  thoracic  nerve  passing  to  the  anterior  superficial  pectoral  muscle. 

2.  At  the  middle  of  the  humerus,  a  long  branch,  represented  in  Man  by  that 
portion  of  the  musculo-cutaneous  nerve  which  proceeds  to  the  anterior  brachial 
muscle  and  the  skin  of  the  forearm.  This  branch  enters  beneath  the  biceps, 
and  forms  two  divisions  ;  one  of  these  is  expended  in  the  brachialis  anticus 
while  the  other  passes  between  that  muscle  and  its  congener — the  long  flexor — to 
become  superficial  and  gain  the  internal  aspect  of  the  limb,  when  it  breaks  up 
into  two  principal  filaments,  which  pass  to  the  external  face  of  the  antibrachial 
aponeurosis,  and  accompany  with  their  divisions  the  two  subcutaneous  veins  of 
the  forearm  to  below  the  carpal  region  (Fig.  465,  21,  22). 

3.  In  the  antibrachial  region,  and  at  various  elevations — but  particularly  below 
the  ulnar  articulation — ramifications  to  the  internal  flexor  of  the  metacarpus  and 
the  two  flexors  of  the  phalanges. 

Plantar  Nerves. — These  nerves,  two  in  number,  are  distinguished  as 
internal  and  external. 

The  internal  plantar  nerve — one  of  the  terminal  branches  of  the  median  nerve — 
lies  beside  the  large  metacarpal  artery,  and  follows  that  vessel  along  the  perforans 
tendon  to  near  the  fetlock,  where  it  ends  in  several  digital  branches.  In  its 
track  it  furnishes  a  number  of  cutaneous  metacarpal  ramuscules,  and  an  anasto- 
mosing branch,  which,  after  being  detached  from  the  principal  trunk,  about  the 
middle  of  the  cannon,  bends  obliquely  behind  the  flexor  tendons  to  join  the 
external  plantar  nerve.  This  is  formed  by  the  union  of  two  branches— one 
coming  from  the  ulnar  nerve,  the  other  from  the  median,  and  joining  the  first 
at  the  upper  border  of  the  pisiform  bone,  after  passing  beneath  the  inferior 
extremity  of  the  oblique  flexor  of  the  metacarpus.  This  nerve,  which  accom- 
panies the  external  metacarpal  vein  for  its  entire  length,  descends  with  it,  and 
with  an  arteriole  that  concurs  in  forming  the  subcarpal  arch,  outside  the  flexor 
tendons,  in  a  special  fibrous  channel  of  the  carpal  sheath.  Near  the  superior 
extremity  of  the  cannon,  within  the  head  of  the  external  metacarpal  bone,  it 
sends  on  the  posterior  face  of  the  suspensory  ligament  of  the  fetlock  a  deep 
plantar  branch,  chiefly  destined  to  the  fleshy  portion  of  the  interosseous  muscles. 
It  is  the  analogue  of  the  deep  palmar  branch  of  the  ulnar  nerve  in  Man.     Con- 


THE  BRACHIAL   PLEXUS. 


867 


tinuing  its  descending  course  along  the  perforans  tendon,  it  throws  off  some 
superficial  metacarpal  ramuscules,  receives  the  accessory  branch  supplied  by  the 
internal  nerve,  and  terminates,  like  the  latter,  in  a  number  of  digital  branches 
on  aiTiving  at  the  fetlock  ;  these  it  now  remains  for  us  to  examine. 


NERVES   OF   THE   DIGIT. 

P,  Plantar  nerve ;  B,  median  branch ;  C,  anterior  branch ;  d,  digital  artery ;  H,  inconstant  division 
given  off  to  the  cartilaginous  bulbs;  i,  i,  branch  to  the  plantar  cushion  ;  K,  transverse  coronary 
branch  ;  m,  podophyllous  branch ;  0,  preplantar  branch  ;  Q,  descending  ramuscule  to  the  fissure 
of  the  patilobes ;  R,  ramuscules  accompanying  the  digital  artery  in  the  plantar  fissure ;  v,  vein 
which  is  not  constant,  and  which  sometimes  accompanies  the  plantar  nerve  throughout  its 
phalangeal  course. 


The  digital  branches  are  the  terminal  branches  of  the  plantar  nerves  ;  they 
are  three  in  number  on  each  side,  and  accompany  the  digital  artery  and  vein. 


868  TEE  NERVES. 

which,  at  some  points,  they  cover  with  their  divisions.  They  separate  from  one 
another  nearly  at  the  insertion  of  the  suspensory  hgamerit  into  the  sesamoid 
bones.  One  of  them  descends  in  front  of  the  vein  ;  another  passes  between  the 
two  vessels ;  while  the  third  follows  the  artery  behind.  They  may,  therefore, 
be  distinguished,  according  to  their  position,  into  anterior,  middle,  and  posterior 
(Fig.  467,  M,  0,  r). 

The  anterior  branch  distributes  its  collateral  divisions  to  the  skin  on  the 
anterior  face  of  the  digit,  and  its  terminal  ramuscules  in  the  coronary  cushion. 

The  middle  branch  frequently  anastomoses  with  the  other  two,  particularly 
with  the  anterior,  and  to  such  a  degree  as  to  be  scarcely  distinguished  from  it ; 
it  enters  the  coronary  cushion  and  the  podophyllous  tissue. 

The  posterior  branch — much  more  considerable  than  the  preceding,  and  a  real 
continuation  of  the  plantar  nerve — is  at  first  superposed  on  the  digital  artery^ 
then  it  is  placed  immediately  behind  that  vessel.  It  descends  with  it  to  near 
the  basilar  process  of  the  third  phalanx,  follows  the  preplantar  ungual  artery  into 
the  lateral  fissure  of  that  phalanx,  and,  like  that  vessel,  expends  itself  in  the 
midst  of  the  podophyllous  tissue,  as  well  as  in  the  osseous  structure.  This  branch 
gives  off  numerous  ramuscules  on  its  course.  Of  these  there  may  be  more  par- 
ticularly noticed  :  1 .  Some  posterior  divisions,  distributed  behind  the  flexor 
tendons,  especially  at  the  fetlock.  2.  A  satellite  branch  to  the  artery  of  the 
plantar  cushion.  3.  A  filament  arising  below  the  lateral  cartilage,  passing  for- 
ward, in  proximity  to  the  anterior  branch  of  the  arterial  coronary  circle,  and 
becoming  lost  in  the  meshes  of  the  deep  venous  network  of  the  cartilage.  4.  A 
small  podophyllous  division,  the  origin  of  which  is  placed  at  the  same  height  as 
the  preceding  filament,  but  opposite  it,  and  which  descends  on  the  retrossal 
process,  where  it  traverses  the  cartilaginous  tissue  to  pass  to  the  podophyllous 
reticulation,  after  distributing  posterior  ramuscules  to  the  plantar  cushion.  5. 
Several  extremely  fine  filaments  enlaced  around  the  plantar  ungual  artery,  and 
with  it  passing  to  the  interior  of  the  os  pedis  ;  some  of  these  filaments  ascend  to 
the  nerve  of  tlie  opposite  side.-^ 

Differential  Characters  in  the  Brachial  Plexds  of  the  other  Animals. 

In  the  domesticated  Mammals,  the  nerves  of  the  brachial  plexus  do  not  offer  any  very 
important  differences  in  the  upper  part  of  the  limb ;  these  only  become  apparent  in  the  nerves 
of  the  last  section. 

Ruminants.— The  brandies  of  the  plexus— the  same  in  number  as  in  the  Horse— are  rela- 
tively more  voluminous  than  in  that  animal.  In  the  Ox  they  are  often  tiexuous  in  tiieir  upper 
part.  In  the  Sheep,  the  diaphragmatic  nerve  is  formed  by  a  single  filament,  detached  from 
the  branch  the  sixth  cervical  nerve  gives  to  the  brachial  plexus,  and  whicii  passes  over  the  surface 
of  the  scalenus;  and  a  second  branch  which  comes  from  the  fifth  pair,  runs  beneath  the 
scalenus,  and  joins  the  first  on  the  inner  surface  of  the  first  rib  (Toussaint).     There  are  no 


'  It  is  because  we  conform  to  established  usages,  and  are  unwilling  to  force  analogies,  that 
we  preserve  the  designations  of  "  plantar  nerves  "  and  "  digital  branches,"  as  well  as  the  above 
manner  of  describing  them.  Comparative  anatomy  desires  other  names  and  a  different  descrip- 
tion ;  for  it  demonstrates  that  the  external  plantar  nerve  corresponds  to  the  interosseous  palmar 
of  the  second  space  in  pentadactylous  animals ;  and  the  internal  plantar  to  the  interosseous  palmar 
of  the  third  space.  It  also  shows  that  the  digital  branches  are  the  exact  representatives  of  the 
collaterals  of  the  digits  which  result,  in  the  pentadactylous  species,  from  a  bifurcation  of  each 
interosseous  nerve. 

According  to  this  description,  it  will  be  seen  that  the  terminal  branches  of  the  meiiiau 
nerve  are  not  only  distributed  over  the  posterior  face  of  the  digit,  hut  that  a  good  number  of 
fiilaments  are  sent  to  tiie  dorsal  face— a  remark  which  has  been  made  in  recent  years,  with 
leference  to  the  distribution  of  the  collateral  palmar  neives  of  the  human  fingers. 


THE  BRACHIAL  PLEXUS. 


diflferences  in  the  branch  of  the  angularis  and  rhomboideus,  in  the  branches  of  the  pectoral 
muscles,  the  subcutaneous  thoracic  branch,  or  the  anterior  brachial  or  musculo-cutaneous  nerve. 

The  nerve  of  the  serratus  magnus  does  not  sliow  the  branch  which,  in  the  Horse,  arises  from 
the  sixth  nerve  and  passes  tlirough  the  scalenus;  but  on  the  surface  of  the  serratus  magnus  it 
receives  a  filament  from  the  branch  of  the  angularis.     The  latter  is  detached  from  the  sixth. 

The  branch  of  the  latissimus  dorsi  muscle  and  the  axillary  nerve  are  confounded  at  their 
origin,  and  also  adhere  fo  one  of  the  two 
branches  of  the  siibscapularis  nerve.  The 
second  branch  of  the  latter  is  free  through- 
out its  extent,  and  distributed  in  the  mus- 
cle of  the  same  name,  along  with  some  fila- 
ments furnisiied  by  the  supra-scapularis. 

The  radial  nerve,  when  it  reaches  the 
teres  major,  divides  into  three  branches  : 
one  is  buried  in  the  long  extensor  of  the 
forearm ;  the  other  traverses  the  middle 
extensor ;  and  the  third  is  inflected  on  the 
tendon  of  the  latissimus  dorsi,  and  passes 
between  the  middle  and  large  extensor 
of  the  forearm.  "When  the  radial  nerve 
turns  outwards  around  the  arm,  and  is 
placed  between  the  anterior  brachial  and 
the  mass  of  the  olecranian  muscles,  it 
furnishes :  1.  Muscular  branches  that  pass 
immediately  beneath  the  extensors  of  the 
metacarpus  and  phalainges.  2.  A  sensitive 
branch  that  leavesthis  muscular  interstice 
to  become  subcutitneous.  This  cutaneous 
branch  of  the  radial  nerve  gains  the  inner 
face  of  the  forearm,  and  divides  in  two 
branches  that  descend  parallel  to  the 
median  subcutaneous  vein.  One  of  these 
is  distributed  around  the  carpus ;  the 
other  is  placed  a  little  in  front  of  the  meta- 
carpus, and  reaches  the  mctacarpo-plialan- 
goal  articulation,  where  it  terminates  by 
two  principal  filaments  that  constitute  the 
dorfiol  collaterals  of  the  difjits ;  there  is 
a  third  which  crosses  the  interdigital  to 
anastomose  with  the  palmar  collaterals. 

The  ulnar  and  median  nerve  of  Kuuii- 
nants  lie  beside  each  other,  as  far  as  the 
middle  of  the  arm.  This  double  cord  is 
situated  at  the  surface  of  the  humeral 
artery ;  at  the  carpus  the  two  nerves  otfer 
the  same  distribution  as  in  the  Horse,  but 
beyond  tliis  there  are  some  differences. 

The  ulnar  does  not  receive  a  branch 
from  the  median  at  the  carpus,  and  it 
forms  the  external  plantar  nerve  or  iiiter- 
os.seous  palmar  of  the  second  space,  placed 
at  the  external  border  of  t  h  e  flexor  tendons. 
This  nerve  is  reinforced  by  a  filament  de- 
tached from  the  external  plantar,  that 
joins  it  a  little  above  the  fetlock -joint ;  it 
gives  ramuscules  to  the  ergot,  and  is  then 
continued  by  the  external  collateral  nerve 
of  the  outer  digit,  into  the  toe. 

The  median  is  continued  by  the  internal  plantar,  or  interosseous  palmnr  of  the  third  space. 
Towards  the  inferior  third  of  tlie  metacarpus,  it  divides  into  three  branches :  the  third  passes 
to  the  external  plantar ;  the  second  proceeds  to  the  interdigital  space,  where  it  bifurcates  to 
form  the  internal  collateral  palmar  nerves  of  the  external  digit,  and  external  collateral  of  the 


NERVES   OF   THE    DIGITAI;   REGION   OF    RUMINANTS 

(POSTERIOR  face). 

M,   Internal    plantar    nerve,    a    continuation   of    the 


C,  internal  plantar  nerve,  a  continuation 
of  the  ulnar.  1,  Branch  of  the  plantar,  furnishing, 
2,  the  internal  collateral  nerve  of  the  internal 
digit ;  3,  branch  giving  otF  the  internal  collaterals 
of  the  digits ;  1',  branch  of  the  internal  plantar 
that  joins  the  e.\ternal  plantar ;  4,  external  col- 
lateral of  the  e.'cternal  digit. 


870  THE  NERVES. 

internal  digit;  the  third  gives  some  filaments  to  the  ergot,  and  passes  along  the  digital  region, 
where  it  constitutes  the  internal  collateral  of  the  internal  digit. 

Pig. — Three  fasciculi  are  detached  from  the  brachial  plexus;  the  posterior  is  the  most 
voluminous,  and  furnishes  the  radial,  median,  and  ulnar. 

The  branches  of  the  plexus  that  pass  to  the  trunk  and  the  first  segments  of  the  anterior 
limb  much  resemble  those  of  Ruminants;  the  branch  of  the  serratas  magnus  is  remarkable  for 
its  length  and  size. 

The  median  nerve  is  disposed  like  that  of  Solipeds  and  Ruminants,  as  far  as  the  carpus*, 
from  this  point  it  passes  beneath  the  flexor  tendons  of  the  phalanges,  gives  filaments  to  the 
interosseous  palmar  muscles,  and  at  the  two  rudimentary  digits  divides  into  four  branches: 
the  two  upper  are  the  smallest,  and  forms  the  collaterals  of  the  rudimentary  digits;  tlie 
inferior  two  are  tiie  longest,  and  reach  the  principal  interdigital  space,  forming  the  collaterals 
of  the  two  great  digits. 

The  ulnar  gives  off,  towards  the  middle  of  the  arm,  a  branch  that  passes  to  the  ulna ;  at 
the  ulnar  it  furnishes  several  muscular  branches.  The  nerve  then  bend  round  to  the  outside 
of  the  forearm,  and  on  arriving  above  the  pisiform  bone,  bifurcates  :  one  branch  goes  along 
the  outer  border  of  the  flexor  tendons,  and  is  continued  by  the  collateral  of  the  external  digit; 
the  other  is  placed  on  the  anterior  face  of  the  metacarpus,  and  also  bifurcates  to  give  the 
external  digits  their  dorsal  collateral  nerves. 

Caknivoba. — The  four  last  cervical  and  first  dorsal  compose  the  brachial  plexus  in  the 
Caruivora ;  the  fifth  cervical  gives  an  insignificant  filament.  When  the  plexus  is  unravelled, 
its  principal  brandies  are  observed  to  send  fibres  to  each  other. 

The  number  of  the  distributive  branches  is  the  same  as  in  Solipeds,  and  the  disposition  ol 
the  superior  branches  is  so  analogous  as  to  call  for  no  remark ;  so  we  will  only  describe  the 
anterior  brachial,  radial,  median,  and  cubital  nerve. 

The  anterior  brachial,  or  muscnlo-cutaneous,  is  constituted  by  a  filament  from  the  sixth 
cervical  and  the  more  voluminous  branches  coming  from  the  seventh.  Placed  in  front  of  the 
axillary  artery,  this  cord  arrives  at  the  scapulo-humeral  articulation,  where  it  bifurcates  :  one 
of  the  branches  passes  forward  to  the  biceps  ;  the  other  remains  alongside  the  anterior  border 
of  the  humeral  artery,  and  terminates  by  a  slightly  recurrent  branch  that  is  buried  in  the 
anterior  brachial  muscle,  and  by  a  very  fine  filament  that  becomes  subcutaneous  at  the  elbow, 
and  descends  on  the  inner  border  of  the  forearm  to  be  lost  in  the  vicinity  of  the  carpus.  The 
anterior  brachial  is,  therefore,  in  these  animals,  a  muscnlo-cutaneous  nerve.  The  branch 
uniting  it  to  the  median  nerve  is  situated  a  little  below  the  middle  of  the  humerus,  instead 
of  being  beneath  the  axillary  artery,  as  in  Solipeds. 

The  radial  nerve,  in  the  35og,  is  exclusively  formed  by  the  eij;hth  cervical ;  it  receives 
filaments  from  the  median,  ulnar,  and  axillary  nerve,  and  gives  branches  to  these  three.  When 
it  reaches  tlie  interstice  of  the  triceps  and  anterior  brachial,  it  crosses  the  limb  above  the  outer 
face  of  the  elbow,  and  divides  into  two  series  of  terminal  branches. 

The  muscular  branch  enters  beneath  the  muscles  on  the  anterior  face  of  the  forearm. 
The  cutaneous  bifurcates  immediately  :  the  smallest  branch,  passing  inwards,  extends  beyond 
the  bend  of  the  elbow,  lies  at  the  inner  border  of  the  median  subcutaneous  vein,  and  is  dis- 
tributed to  the  lower  moiety  of  the  forearm,  the  thumb,  and  internal  border  of  the  index  digit. 
The  largest  lies  at  the  outer  side  of  the  median  subcutaneous  vein ;  it  sends  a  recurrent 
ramuscule  to  the  bend  of  the  elbow,  and,  at  the  elbow,  detaches  three  filaments  to  the  first, 
second,  and  third  dorsal  intermetacarpal  spaces ;  these  filaments  bifurcate  at  the  dorsum  of  the 
digits  to  constitute  the  collateral  dorsal  nerves.  The  first  metacarpal  nerve  anastomoses,  by  a 
fin  transverse  brancli,  with  the  ulnar  ramuscule  that  constitutes  the  external  dorsal  collateral 
of  the  small  digit. 

To  resume  :  the  radial  of  the  Dog  gives  branches  to  the  dorsal  face  of  all  the  digits,  except 
the  external  border  of  first  digit,  or  auricularis. 

In  the  Cat,  there  are  some  differences.  The  internal  branch  of  the  radial  sometimes 
lies  with  the  external  branch;  it  is  placed  at  the  inner  border  of  the  metacarpus,  gives  off  a 
filament  to  the  dorsal  face  of  the  thumb,  and  afterwards  forms  the  internal  dorsal  collateral 
nerve  of  the  index.  The  external  branch  leaves  the  anterior  face  of  the  carpus,  and  is  situated 
at  the  origin  of  the  third  interosseous  space,  where  it  divides  into  three  metacarpal  branches; 
the  external  of  these  is  very  fine,  and  directed  obliquely  outwards,  anastomosing  with  the 
dorsal  branch  of  the  ulnar,  between  the  first  and  second  digits. 

The  median  of  the  Dog  is  united  to  the  ulnar  as  far  ns  the  lower  fourth  of  the  arm  ;  it  is 
situated  behind  the  humeral  artery,  and  the  filament  it  receives  from  the  musculo-cutaneous 
joins  it  at  a  short  distance  from  the  elbow-joint.  Placed  beside  the  radial  artery,  tlie  median 
is,  towards  the  lower  third  of  the  forearm,  immediately  below  the  posterior  border  of  the 


THE  BRACHIAL   PLEXUS. 


871 


great  palmar  tendon :  it  afterwards  passes  through  the  carpal  sheath,  siving  a  branch  that 
constitutes  the  internal  palmar  collaterals  of  the  thumJt,  and  external  of  the  index;  it  finally 
forms  three  branches,  the  first  of  whicli  anastomoses  with  the  ulnar,  at  the  surface  of  the  palmar 
arcli,  and  is  lost  on  an  artery ;  the  other  two,  receiving  a  filament  from  the  ulnar  at  the  origin 
of  the  digits,  bifurcate  to  form  the  internal  palmar  collateral  of  the  annularis,  and  collaterals  of 
the  medius  and  index.     The  second  gives,  in  addition,  a  slender  branch,  that  is  lost  in  the 

Fig.  469. 


¥vi  4-70, 


NERVES   OF    THE    PALMAR   FACE   (DOG). 

A,  Trunk  of  the  median  dividing  into  six  branches; 
Bl,  branch  of  the  superficial  nervous  arch;  b2, 
branch  disappearing  on  a  vessel ;  b3,  b4,  branches 
uniting  with  the  corresponding  ramuscules  of  the 
ulnar;  b5,  branch  forming  the  internal  collateral 
of  the  index  ;  b6,  rudimentary  branch  passing  to 
the  thumb;  C,  collateral  given  off  by  the  median; 
Cl,  C2,  C3,  c4,  collaterals  furnished  by  the  median 
and  ulnar,  a,  Palmar  branch  of  the  ulnnr;  6, 
superficial  branch  giving  off  a  filament  to  the  hypo- 
thenar,  and  a  second  that  forms  the  superficial 
nervous  arch  ;  61,  deep  branch  passing  to  the 
muscles  of  the  skin  ;  in,  not  anastomosing  with  the 
median  ;  ml,  m2,  anastomosing  with  the  correspond- 
ing branch  of  the  median  ;  the  innermost  passes  to 
the  muscles  of  the  thumb;  c,  c,  c,  collaterals  fur- 
nished by  the  ulnar. 


NERVES   OF   THE    PALMAR    FACE  (CAT). 

A,  Trunk  of  the  median  dividing  into 
two  branches;  B,  internal  branch, 
giving  a  rudimentary  filament  to  the 
thumb,  Bl,  external  branch,  receivmg 
a  filament,  /,  from  the  ulnar;  c,  C,  C,  C, 
collaterals  furnished  by  the  median. 
a,  Palmar  branch  of  the  ulnar  divid- 
ing into  three  branches ;  h,  internal 
branch,  detaching  the  filament,  /,  to 
the  median;  61,  external  branch; 
62,  deep  branch  ;  c,  c,  c,  collaterals 
furnished  by  the  ulnar. 


internal  and  middle  lobe  of  the  large  cushion  of  the  paw.     In  fine,  the  median  of  the  Dog 
furnishes  to  all  the  digits,  except  the  auricularis  and  external  border  of  the  annularis. 

In  the  Cat,  the  median  traverses  the  bony  canal  at  the  lower  extremity  of  the  humerus, 
and  separates  below  the  carpal  arch  into  three  branches.  The  internal  branch  is  destined  to 
the  rudimentarv  thumb,  and  the  internal  palmar  border  of  the  index.     The  middle  branch 


872 


THE  NERVES. 


descends  in  the  third  interosseous  space,  furnishes  a  filament  to  the  large  cushion  of  the  paw, 
and  divides  to  form  the  external  palmar  collaterals  of  the  index  and  internal  of  the  medius. 
Finally,  the  external  branch  is  placed  in  the  second  intermetacarpal  space,  and  gives  the 
following  palmar  collaterals :  the  external  of  the  medius  and  internal  of  the  annularis. 

The  ulnar  nerve  of  the  Dog,  below  the  elbow,  lies  beside  the  ulnar  artery  to  the  lower  third 
of  that  vessel ;  there  it  forms  two  branchLS— a  dorsal  and  palmar.  The  dorsal  branch  becomes 
subcutaneous,  passes  along  the  external  border  of  the  forearm,  metacarpus,  and  small  digit,  and 
constitutes  the  external  dorsal  collateral  nerve  of  the  latter. 

The  palmar  branch  leaves  the  carpal  sheath,  gives  otf,  at  the  trapezoides,  a  ramuscule  that 
passes  to  the  surface  of  the  palmar  muscles  to  form  the  external  collateral  palmar  of  the 
auricularis,  and  then,  at  the  surface  of  the  deep  palmar  arch,  divides  into  eight  terminal 
t 

Fig.  471. 


THE  NERVES  OF  THE  AXILLA.  OF  MAN. 

1,  Scalenus  medius;  2,  scalenus  anticus;  3,  cord  formed  by  5th  and  6th  cervical  nerves;  4,  7th 
cervical  nerve  ;  5,  superscapular  nerve  ;  6,  subclavian  avteiy  (cut)  ,  7,  insertion  of  subclavius  ;  8, 
cord  formed  by  8th  cervical  and  1st  dorsal  nerves  ;  9,  pectoralis  major  (reflected);  10,  internal 
anterior  thoracic  nerve  ;  12,  origin  of  subclavius ;  13,  pectoralis  minor  (reflected) ;  14,  internal 
cutaneous  nerve;  15,  axillary  artery  (cut);  16,  posterior  thoracic  nerve  ;  17,  musculo-cutaneous 
nerve;  18,  origin  of  pectoralis  minor;  19,  median  nerve;  20,  nerve  of  Wrisberg ;  "21,  coraco- 
brachialis ;  22,  intercosto-humeral  nerve;  23,  ulnar  nerve;  24,  subscapularis ;  25,  brachial 
artery  ;  2'i,  lateral  cutaneous  branch  of  3rd  intercostal  nerve  ;  27,  middle  subscapular  nerve  ;  28, 
short  subscapular  nerve;  29,  pectoralis  major  (cut);  31,  basilic  vein;  32,  serratus  magnus;  33, 
latissimus  dorsi. 


ramuscules.  The  smallest  of  these  is  expended  in  the  rudimentary  muscles  of  the  thumb,  the 
small  digit,  and  interosseous  muscles ;  the  largest,  three  in  number,  lie  on  the  interosseous 
arteries,  and  bifurcate  at  the  digits  to  form  the  palmar  collaterals  ;  the  two  internal  ramuscules 
are  previously  confounded  with  the  corresponding  branches  of  the  median.  From  this  arrange- 
ment, it  results  that  the  ulnar  nerve  supplies  the  palmar  surface  of  all  the  digits,  except  the 
internal  border  of  the  index. 

The  ulnar  of  the  Cat  also  divides  into  a  dorsal  and  a  palmar  branch,  but  the  distribution 
of  these  is  not  the  same  as  in  the  Dog. 

The  dorsal  branch  bifurcates  at  the  carpus  :  one  of  the  filaments  forms  the  external  dorsal 
collateral  of  the  small  digit;  the  other  reaches  the  first  interosseous  space,  receives  a  branch 


THE  BRACHIAL   PLEXUS. 


878, 


from  the  radial,  and  afterwards  gives  off  the  internal  dorsal  collateral  of  the  small  digit,  and 
external  of  the  auricularis. 

The  palmar  branch  does  not  extend  to  all  the  digits  as  in  the  Dog.  Passing  within  the 
pisiform  bone,  it  divides  into  several  filaments ;  some  of  these  are  distributed  to  the  muscles  of 
the  small  digit  and  thumb ;  another  follows  the  external  border  of  the  small  digit,  and  con- 
stitutes its  external  palri)ar  collateral ;  one  of  the  longest 

is  lodged  in  the  first  intermetacarpal  space,  giving  a  fila-  _Zi?i  *'^2- 

ment  to  the  large  cushion  of  the  paw,  and  the  internal 
palmar  collaterals  of  the  small  digit  and  external  of  the 
annularis. 

Comparison  of  the  Brachial  Plexus  in  Man  with 
THAT  of  Animals. 

The  brachial  plexus  of  Man,  like  that  of  the  Dog,  is 
constituted  by  the  anterior  branches  of  the  four  last  cervi- 
cal, and  the  last  dorsal  nerves.  The  few  variations  ob- 
served are  very  slight,  and  are  to  be  ascribed  to  the  differ- 
ence in  form  of  the  regions  to  which  the  nerves  are  dis- 
tributed. 

The  shoulder  of  Man  being  short,  and  the  other  seg- 
ments of  the  limb  long  and  well  detached,  the  branches 
of  the  brachial  plexus  can  be  divided  into  collateral  and 
terminal. 

Tlie  coZiafem?  branches  are:  1.  The  subclavian  branch, 
whicii  is  not  found  in  our  animals,  they  having  no  sub- 
clavian muscle.  2.  The  nerve  of  the  levator  anguli 
tcapulx.  3.  Nerve  of  the  rhomhovhus.  4.  Supra-scapular 
nerve.  5.  The  serratus  mngnus  (posterior  ihnracic)  nerve. 
6.  Subscapular,  which  is  divided  at  its  origin  into  two 
branches  as  in  the  Sheep  and  Cainivora.  7.  The  nerves  of 
the  great  and  small  pectorals  (anterior  thoracic).  The 
accessory  nerve  of  the  internal  cutaneous,  reprpsented  in 
quadrupeds  by  the  subcutaneous  thoracic.  9.  The  nerve 
of  the  latissimus  dor  si.     10.  The  nerve  of  the  teres  major. 

The  terminal  branches  go  to  the  arm,  forearm,  and  hand. 
They  iire : 

1.  The  internal  cwtoneoMg,  which  in  tije  Horse  is  fur- 
nished  by  the  ulnar  nerve.  It  becomes  subcutaneous  at 
the  upper  third  of  the  arm,  and  a  little  above  the  elbow 
bifurcates ;  the  anterior  is  spread  on  the  anterior  aspect  of 
the  arm  to  the  wrist ;  the  posterior  passes  backwards,  and 
is  expended  in  the  skin  of  the  lack,  and  inner  part  of  the 
forearm. 

2.  The  musculo-cutaneous,  or  perforans  Casserii,  the 
disposition  of  whicli  is  analogous  to  that  of  Carnivnra. 

3.  The  axillary  nerve,  regarding  which  there  is  nothing 
to  say. 

4.  The  radial  nerve  (musculo- spiral)  passes  as  in 
animals,  lies  in  the  musculo-spiral  groove  of  tiie  humerus, 
gives  off  an  internal  and  external  cutaneous  branch,  and 
reaches  the  antero-external  part  of  the  arm.  in  the  space 
between  the  anterior  brachial  and  long  supinator,  where 


NERVES  OF   THE   FRONT  OF   FORE- 
ARM   AND    HAND   OF    MAN. 

1,  Supinator  longus  (cut) ;  2,  ulnar 
nerve  ;  3.  brachialis  anticus  ;  4, 
biceps;  5,  musculo-spiral  nerve; 
6,  median  nerve ;  7,  posterior 
interosseous  nerve;  8,  pronator 
teres    and    flexor    carpi    radialis 


(cut) ;  9,  extensor  carpi  radialis 
longior  (cut)  ;  10.  brachial  artery;  11,  supinator  brevis  ;  12,  flexor  sublimis  digitorum  (cut); 
13,13,  radial  nerve;  14,  14,  flexor  carpi  ulnaris  ;  15,  extensor  carpi  radialis  brevier;  16,  ulnar 
artery;  17,  radial  origin  of  flexor  sublimis  digitorum  (cut);  18,  flexor  profundus  digitorum;  19, 
tendon  of  pronator  teres;  20,  20,  dorsal  branch  of  ulnar  nerve;  21,  21,  radial  artery;  22,  22, 
deep  branch  of  ulnar  nerve;  23,  flexor  longus  pollicis;  24,  abductor  minimi  digiti ;  25,  anterior 
interosseous  nerve;  26,  digital  branches  of  ulnar  nerve;  27,  tendon  of  supinator  longus;  28,  one 
of  the  lumbricales  muscles;  29,  pronator  quadratus ;  31,  tendon  of  flexor  carpi  radialis;  33, 
digital  branches  of  median  nerve ;  35,  adductor  pollicis. 


874  TEE  NERVES. 

it  terminates  by  two  brauches.  The  anterior  of  these  reaches  the  back  of  the  liand,  and  gives 
off  three  rainuscules  there,  which  are  distributed  as  follows :  the  first  forms  the  external  dorsal 
collateriil  of  the  thumb ;  the  second  bifurcates,  and  constitutes  the  internal  dorsal  collateral 
of  the  thumb  and  external  collateral  of  the  index ;  lastly,  the  third  supplies  the  internal 
collateral  of  the  index  and  external  of  the  medius.  This  brancli  always  anastomoses  with  the 
dorsal  branch  of  tlie  ulnar.  Tlie  posterior  branch — motor — is  expended  in  the  muscles  on  the 
posterior  and  external  aspect  of  the  forearm. 

5.  Thti  median  nerve  commences  by  two  branches.  One  arises  in  common  with  the  musculo- 
cutaneous or  anterior  brachial,  and  corresponds  to  the  anastomosis  found  around  the  axillary  artery 
of  the  Horse;  tiie  other  is  detached  from  the  trunk  common  to  the  ulnar  and  internal  cutaneous. 
The  median  runs  along  the  biceps,  passes  in  front  of  the  elbow,  and  lies  beneath  the  annular 
Ijo-ament  of  the  carpus,  where  it  terminates  in  furnishing:  1.  A  filament  to  the  short  abductor 
of  the  thumb.  2.  Palmar  ramuscules  to  the  thumb,  index,  and  medius,  and  external  border  of 
the  annularis.     This  disposition  of  the  medius,  therefore,  much  resembles  that  of  the  Cat. 

6.  The  ulnar  nerve  passes  along  the  inner  border  of  the  arm  and  forearm,  and  divides,  a 
little  above  the  inferior  extremity  of  the  olecranon,  into  tNvo  terminal  branches— a  dorsal  and 
palmar.  The  first  is  directed  on  the  back  of  the  hand,  and  separates  into  three  metacarpal 
branches,  which,  in  their  course,  furnish  the  dorsal  collaterals  of  the  auricularis  and  annularis, 
and  internal  collateral  of  the  medius  ;  the  otiier  parts  of  the  hand  are  supplied  by  the  radial. 
The  second,  or  palmar  branch,  is  superficial,  and  detaches  the  palmar  collaterals  of  the  little 
finger  and  internal  collateral  of  the  annularis,  as  well  as  a  deep  ramuscule  that  lies  across  the 
interosseous  muscles,  and  is  a  motor  nerve.  To  resume,  we  see  that  this  distribution  of  the 
terminal  branches  of  the  brachial  plexus  of  Man  much  resembles  that  described  lu  Carnivora, 
and  especially  in  the  Cat. 

Lumbo-sacral  Plexus. 

The  last  two  lumbar  pairs,  and  the  three  first  sacral,  in  becoming  fused 
together,  form  the  lumbo-sacral  plexus,  which  corresponds  in  every  respect — by  its 
constitution,  as  well  as  by  its  mode  of  distribution — to  the  plexus  of  the  thoracic 
limb. 

It  is  usual,  in  human  anatomy,  to  describe  a  lumbar  and  a  sacral  plexus,  each 
formed  by  the  inferior  branches  of  all  the  spinal  pairs,  the  names  of  which  they 
bear.  In  our  opinion,  this  course  has  two  inconveniences.  At  first,  it  apportions 
into  two  fasciculi  the  nerves  of  the  abdominal  limb,  and,  besides  in  including  in 
the  description  of  these  nerves  the  first  lumbar  pair  and  the  last  sacral,  elements 
are  introduced  in  this  description  which  are  altogether  foreign  to  it.  It  may  be 
remarked,  that  the  four  first  lumbar  pairs,  when  they  anastomose  with  each  other, 
do  so  by  very  slender  filaments  ;  that  they  only  send  some  subcutaneous  filaments 
to  the  posterior  limb  ;  that  the  two  last  sacral  branches— principally  for  the  genito- 
urinary organs  and  the  posterior  extremity  of  the  digestive  tube— are  usually  with- 
out any  direct  communication  with  the  others  ;  that  the  two  last  lumbar  pairs 
and  the  three  first  sacral  are  alone  fused  in  the  same  manner  as  the  brachial  plexus, 
and  comport  themselves  like  that  plexus  in  the  distribution  of  their  branches. 

It  is  with  some  reason,  then,  that  we  have  described,  in  a  special  manner,  the 
inferior  branches  of  the  four  lumbar  pairs  and  the  two  last  sacral,  reserving  the 
fasciculus  formed  by  the  five  intermediate  pairs  for  a  special  description,  under 
the  name  of  the  lumbo-sacral  plexus. 

Mode  of  constitution.— In  glancing  at  this  plexus,  we  may  perceive  that  it  is 
divided  into  two  portions— an  interior  and  posterior,  each  having  a  thick  trmik 
in  the  centre. 

The  first  of  these  trunks  is  formed  by  the  two  above-named  lumbar  pairs, 
which  join  each  other  after  a  short  course,  and  after  receiving  an  accessory  branch 
from  the  fourth  pair.  The  second— wider  and  thinner  than  the  preceding— com- 
prises the  fibres  of  the  three  sacral  pairs  which  escape  from  beneath  the  subsacral 
vessels,  and  unite  in  a  smgle  fasciculus.     These  two  trunks  are  connected  with 


THE  LUMBOSACRAL  PLEXUS.  875 

each  other  by  one  or  two  branches  proceeding  from  the  first  sacral  pair  to  the 
obturator  nerve — one  of  the  distributive  branches  of  the  first. 

Relations. —The  anterior  portion  of  the  lumbo-sacral  plexus  is  concealed 
beneath  the  psoas  parvus  muscle,  and  separated  by  the  internal  iliac  artery  from 
the  posterior  portion.  The  latter,  placed  above  and  on  the  side  of  the  pelvis,  at 
the  sacro-sciatic  foramen,  corresponds,  inwardly,  to  the  subsacral  vessels  ;  out- 
wardly, and  in  front,  to  the  gluteal  vessels. 

Mode  of  distribution.— The  anterior  portion  of  the  plexus  at  first  gives  off 
several  small  branches  to  the  psoas  muscles,  and  particularly  to  the  iliacus — these 
branches  were  designated  by  Girard  the  iliaco-muscular  nerves  ;  it  then  termi- 
nates in  two  large  branches— the  crural  and  obturator  nerves.  The  posterior  por- 
tion is  continued  by  two  important  trunks— the  great  and  small  femoro-popliteal 
n&rves.  At  the  base  of  the  latter,  it  emits  the  anterior  and  posterior  gluteal 
nerves.    These  branches  and  their  ramifications  will  be  successively  studied. 

Preparation  of  the  lumbo-sacral  plexus.— After  removing  the  skin  and  abdominal  viscera,  the 
hind  quarters  are  isolated  by  sawing  through  the  vertebral  column  behind  the  last  rib  ;  then,  by- 
means  of  a  section  almost  in  the  middle  of  the  pelvis,  one  of  the  limbs  is  cut  off,  and  the  pieces, 
disposed  as  in  Fig.  473,  should  be  maintained  iu  the  first  position— that  is,  with  the  croup 
resting  on  the  dissecting-table  near  one  of  the  bars,  and  the  limb  suspended  vertically,  the  foot 
upwards,  by  a  cord  attached  to  the  ring  of  the  bar. 

Afterwards,  the  preparation  is  executed  in  two  stages.  In  the  first,  after  the  excision  of 
the  pelvic  organs  and  the  psoas  parvus  muscle,  the  whole  of  the  plexus  and  its  formative 
branches  are  dissected,  taking  Fig.  373  as  a  guide.  In  the  second,  the  posterior  part  of  the 
plexus,  with  the  nerves  it  gives  off,  are  exposed  on  the  external  side,  by  excising  the  greater 
portion  of  the  principal  gluteal  muscle  and  the  anterior  portion  of  the  biceps  femoris,  as  in 
Fig.  474. 

To  follow  the  various  divisions  of  the  nerves  emanating  from  the  plexus,  to  their  termma- 
tioas,  it  is  well  to  use  the  other  limb,  which,  not  being  fixed,  can  be  laid  on  a  table,  and  in  this 
way  is  uiore  convenient  than  the  first  for  this  part  of  the  operation. 

A.  Anteeior  Portion. 
1.  Iliaco-muscular  Nerves. 

These  nerves  are  of  little  importance.  The  principal  one  accompanies  the 
iliaco-muscular  artery  across  the  iliacus  muscle. 

2.  Crural  or  Anterior  Femoral  Nerve  (Fig.  473,  2). 

This  is  the  largest  of  the  branches  arising  from  the  anterior  portion  of  the 
plexus.  It  descends  between  the  psoas  magnus  and  parvus,  to  the  common  conical 
extremity  of  the  latter  muscle  and  the  iliacus,  where  it  is  covered  by  the  sartorius  ; 
there  it  terminates  in  a  wide  tuft  of  branches,  which,  pass  to  the  rectus  femoris 
and  vastus  internus. 

Below  the  sartorius,  it  successively  emits  two  long  branches,  which  deserve  a 
particular  description. 

The  first  represents  the  fasciculus  which,  in  Man,  includes  the  crural  musculo- 
cutaneous branch.  We  have  named  it  the  accessory  branch  of  the  internal  saphenic 
nerve.  It  reaches  the  interstice  between  the  sartorius  and  gracilis  muscles,  in 
crossing  the  crural  vessels  very  obhquely  forward.  Leaving  this  space,  it  becomes 
subcutaneous,  in  forming  numerous  divisions  which  surround  the  saphena  artery 
and  vein. 

The  second,  or  internal  saphenic  nerve,  passes  at  first  between  the  sartorius 
and  vastus  internus,  and  parallel  to  the  first,  which  is  situated  more  inwardly  and 


876 


THE  NERVES. 


posteriorly.  Near  the  inferior  extremity  of  the  interstice  separating  the  sartorius 
and  gracilis,  it  escapes  and  becomes  subcutaneous,  dividing  into  a  number  of 
filaments  which  meet  those  of  the  accessory  nerve. 

Fig.  473. 


LTJMRO-SACRAL   PLEXUS  AND   INTERNAL   NERVES  OF    THE   POSTERIOR   LIMB. 

i,  1,  Lumbo-sacral  plexus ;  2,  anterior  femoral  nerve ;  3,  internal  saphena  nerve  ;  4,  obturator 
nerve;  5,  originating  fasciculus  of  the  great  and  small  femoro-popliteal  nerves;  6,  superficial 
ramuscules  of  the  posterior  gluteal  nerves;  7,  great  femoro-popliteal  nerve;  8,  internal  pudic 
nerve ;  9,  haemorrhoidal  or  anal  nerve ;  10,  internal  plantar  nerve  ;  11, 12,  its  digital  ramifications. 

Note. — In  the  above  figure  is  seen  tlie  posterior  part  of  the  plexus  formed  by  the  nerve- branches  which  pass 
through  the  three  first  subsacral  foramina.  That  which  escapes  from  the  foramen  between  the  sacrum  and  last 
lumbar  vertebra,  only  gives  a  fine  branch  to  this  part  of  the  plexus,  and  sends  the  greater  portion  of  its  fibres,  in 
two  cords,  to  the  anterior  part.  This  arrangement  is  not  rare,  and  is  generally  seen,  we  believe,  when  there  are 
only  five  lumbar  vertebra :  as  is  remarked  in  the  Ass  and  Mule,  and  sometimes  in  the  Horse.  It  will,  therefora, 
be  understood  that  ttie  nerve  deecribed  by  us  as  the  first  sacral  pair  becomes  a  lumbar  pair. 


THE  JjUMBO-SACRAL  PLEXUS.  ST! 

These  two  branches  communicate  by  deep  or  superficial  anastomosing  loops. 
Before  leaving  the  space  between  the  sartorius  and  gracilis,  they  give  some 
slender  filaments  to  these  two  muscles,  particularly  to  the  latter.  Near  their 
origin,  they  even  distribute  some  to  the  iJiacus.  Becoming  subcutaneous,  theii 
ramuscules  cover  the  inner  face  of  the  thigh  and  leg  ;  the  longest  of  these  accom- 
pany the  saphena  vein  to  the  anterior  aspect  of  the  hock. 

It  sometimes — indeed,  most  frequently — happens  that  the  internal  saphena 
nerve  and  its  accessory  form  only  a  single  branch,  the  muscular  or  cutaneous  divi- 
sions of  which  otherwise  comport  themselves  exactly  like  the  above.  This  is 
exemplified  in  the  dissection  represented  in  Fig.  473. 

3.  Obturatoe  Nerve  (Fig.  473,  4). 

Situated  underneath  the  peritoneum,  to  the  inner  side  of  the  iliac  vessels — which 
it  accompanies  to  the  origin  of  the  obturator  artery — this  nerve  follows  the  latter 
to  the  upper  face  of  the  pubes,  and  passes  with  it  beneath  the  internal  obturator 
muscle,  to  traverse  the  obturator  foramen.  In  this  way  it  arrives  outside  the 
pelvis,  where  it  nevertheless  remains  deeply  concealed  by  the  muscular  masses  on 
the  internal  aspect  of  the  thigh.  Its  terminal  ramification  are  expended  in  the 
obturator  externus,  adductors  of  the  thigh,  pectineus,  and  gracilis.  The  branch 
to  the  latter  muscle  is  the  longest  ;  it  leaves  the  space  between  the  pectineus  and 
graciUs,  and  descends  backwards  on  the  internal  face  of  the  muscle  to  which  it  is 
distributed. 

B.  Posterior  Portion. 
4.  Small  Sciatic  or  Anterior  and  Posterior  Gluteal  Nerves. 

The  small  sciatic  nerve  of  the  Horse  is  composed  of  several  cords  that  issue 
from  the  pelvis  by  the  upper  part  of  the  great  sciatic  notch,  and  which  have  been 
for  a  long  time  described  as  the  anterior  and  posterior  gluteal  nerves. 

The  anterior  gluteal  or  ilio-musmlar  nerves  (Fig.  474,  2,  3,  4,  5)  are  four  or 
five  in  number,  and  arise  either  separately  or  in  groups  from  the  posterior  portion 
of  the  lumbo-sacral  plexus.  They  appear  to  be  more  particularly  furnished  by 
the  two  first  sacral  branches.  All  leave  the  pelvic  cavity  by  the  gi-eat  sciatic 
opening,  along  with  the  anterior  gluteal  vessels.  The  principal  branches  are  lost 
in  the  middle  gluteal  muscle.  One  of  them  (Fig.  474,  4)  crosses  the  neck  of 
the  ilium  above  the  superficial  gluteal  muscle,  and  passes  outwards  to  be  dis- 
tributed to  the  tensor  vaginae  femoris.  The  last,  which  is  the  most  slender, 
descends  to  the  external  surface  of  the  superficial  gluteus,  and  is  distributed  in 
its  substance  (Fig.  474,  5). 

The  posterior  gluteal,  or  isrhio-muscular  nerves  (Fig.  474,  6,  6',  8),  are  usually 
two  in  number — a  superior  and  inferior. 

The  first  escapes  through  the  great  sacro-sciatic  notch,  along  with  the  femoro- 
popHteal  nerves,  and  is  situated  on  the  external  surface  of  the  sciatic  ligament. 
It  passes  backward,  between  this  ligament  and  the  middle  gluteus,  to  beneath 
the  anterior  or  croupal  portion  of  the  biceps  femoris,  in  which  it  is  distributed 
by  several  filaments.  Besides  these,  it  gives  :  1.  In  passing  beneath  the  gluteus 
middle,  a  slender,  but  constant  filament  to  the  posterior  portion  of  that  muscle. 
2.  Another,  and  more  considerable  branch,  which  bends  round  the  posterior 
border  of  that  muscle,  to  be  directed  forward  and  outward  to  the  superficial 
gluteus 

58 


g78  THE  NEEVES. 

The  second  nerve,  situated  beneath  the  preceding,  appears  to  be  detached 
from  the  posterior  border  of  the  great  sciatic  nerve.  It  is  placed  on  the  external 
surface  of  the  sciatic  Ugament,  is  directed  backwards  in  passing  below  the  croupal 
portion  of  the  rectus  femoris,  and  vastus  externus  and  internus,  passes  through 
those  muscles  above  the  ischial  tuberosity,  descending  underneath  the  sacral 
portion  of  the  semitendinosus,  soon  to  leave  its  deep  track  and  become  superficial. 
It  escapes  from  between  the  latter  muscle  and  the  three  just  named,  and  is  lost 
beneath  the  skin  covering  the  posterior  part  of  the  thigh.    Its  deep  portion  gives 


POSTERIOR   PORTION   OF   THE    LUMBO-SACRAL   PLEXUS. 

t  Conioining  fasciculi  of  the  three  first  sacral  nerves ;  2,  3,  4,  5,  anterior  gluteal  nerves ;  6,  6',  8, 
posterior  gluteal  nerves;  7,  9,  branches  which  traverse  the  great  sciatic  ligament,  and  com- 
municate between  the  posterior  gluteal  branches  and  the  divisions  of  the  internal  pudic  nerve  ; 
10  11  12  13,  great  sciatic  nerve  and  its  crural  branches;  14,  small  femoro-popliteal  nerve;  15, 
its  cutaneous  or  peroneal-cutaneous  branch. 

off  collateral  branches  which  reinforce  the  divisions  of  the  internal  pudic  nerve, 
as  well  as  filaments  to  the  long  branch  of  the  semitendinosus  muscle. 

5.  Geeat  Sciatic  or  Great  Femoro-popliteal  Nerve  (Figs.  201,  13 ; 
475,  1,  2). 

This  enormous  nerve  (the  largest  in  the  body),  issues  by  the  great  sciatic 
opening  in  the  form  of  a  wide  band,  which  is  applied  to  the  external  face  of  the 
sciatic  ^Hgament.  Comprised  at  first  between  that  ligament  and  the  middle 
gluteus,  it  is  directed  backwards  in  passing  over  the  fixed  insertion  of  the 
gluteus  internus,  and  arrives  behind  the  gemelli  and  quadratus  femoris  muscles. 
On  leaving  this  point,  it  is  inflected  to  descend  behind  the  thigh,  where  it  is 
lodged  in  the  muscular  sheath  formed  for  it  by  the  biceps,  the  semitendinosus 


THE  LUMBO-SAURAL  PLEXUS.  879 

and  membranosus,  and  the  great  adductor  of  the  thigh.  Arriving  towards  the 
superior  extremity  of  the  leg,  it  enters  between  the  two  bellies  of  the  gastroc- 
nemius muscle,  passes  along  the  posterior  aspect  of  the  perforatus  muscle,  and 
descends  in  the  channel  of  the  hock,  beneath  the  tibial  aponeurosis,  following 
the  internal  border  of  the  fibrous  band  that  reinforces  the  tendon  of  the  hock. 
It  finally  terminates  at  the  calcis  by  two  branches — the  external  and  internal 
plantar  nerves. 

From  the  point  at  which  the  great  sciatic  enters  between  the  bellies  of  the 
gastrocnemius  muscle,  and  as  far  as  the  furrow  of  the  calcis,  this  nerve  corre- 
sponds to  the  branch  named  in  Man  the  "  internal  popliteal  " — a  branch  that  is 
continued  by  the  posterior  tibial,  which  terminates  in  the  plantar  filaments. 

In  its  long  course,  this  nerve  successively  gives  off  :  1.  The  external  popliteal 
nerve,  2.  A  branch  to  the  muscles  of  the  deep  pelvi-crural  region.  3.  Another 
to  the  posterior  crural  muscles.  4.  The  external  saphenous  nerve.  5.  A 
voluminous  fasciculus  to  the  muscles  of  the  posterior  tibial  region.  All  these 
branches  will  be  studied,  more  especially  the  external  popliteal — which  is  so 
disposed  in  Solipeds,  that  Veterinary  authorities  have  described  it  as  a  special 
trunk,  by  the  name  of  the  "  small  femoro-popliteal,"  and  even  as  the  "  small 
sciatic  nerve."     We  will  afterwards  pass  to  the  terminal  branch. 

Collateral  Branches  of  the  Great  Sciatic  Nerve. 

1.     EXTEENAL     POPLITEAL     OR     SmALL     FeMORO-POPLITEAL     NeRVE. — This 

nerve  separates  from  the  great  sciatic  at  the  gemelli  muscles  of  the  pelvis.  It 
is  then  directed  forward  and  downward,  proceeds  between  the  biceps  and  the 
gastrocnemius  muscles,  and  arrives  outside  the  superior  extremity  of  the  leg, 
behind  the  lateral  ligament  of  the  femoro-tibial  articulation,  where  it  terminates 
by  two  branches — the  musculo-mtaneous,  and  the  anterior  tibial  nerve. 

In  the  long  course  it  follows  from  its  origin  to  its  bifurcation,  the  external 
pophteal  nerve  only  furnishes  a  single  collateral  branch — this  is  the  cutaneous 
nerve  which  is  detached  from  the  parent  trunk  above  the  gastrocnemius,  and 
traverses  the  inferior  extremity  of  the  biceps  to  terminate  by  divergent  ramuscules 
to  the  skin  of  the  leg.  It  might  be  named  the  peroneal-cutaneous  branch.  Before 
becoming  superficial,  this  cutaneous  nerve  gives  off  a  small  descending  filament 
which  goes  to  reinforce  the  external  saphenous  nerve,  after  creeping  over  the 
aponeurotic  layer  of  the  external  portion  of  the  gastrocnemius.  This  branch — 
which  might  be  designated  the  accessory  of  the  external  saphenous — sometimes 
proceeds  directly  from  the  popliteal,  as  may  be  remarked  in  Fig.  475. 

Terminal  Branches. — These  two  branches  stimulate  the  muscles  belonging  to 
the  anterior  tibial  region,  and  endow  the  skin  on  the  anterior  surface  of  the  foot 
with  sensation. 

The  musculo-cutaneous  nerve  is  situated  beneath  the  tibial  aponeurosis  ;  it 
first  sends  a  bundle  of  ramuscules  to  the  lateral  extensor  of  the  phalanges,  and 
continues  to  descend  between  that  muscle  and  its  congener — the  anterior  extensor 
— to  the  middle  of  the  tibia.  It  then  traverses  the  fibrous  envelope  of  the  tibial 
muscle,  becomes  subcutaneous,  and  gains  the  anterior  face  of  the  metatarsus, 
where  it  is  lost  in  the  skin.  Some  of  its  terminal  filaments  may  be  followed  to 
the  fetlock,  and  even  beyond  it  (Fig.  475,  6). 

The  anterior  tibial  nerve  passes  in  front  of  the  preceding,  to  one  side  of  the 
superior  extremity  of  the  leg,  and  then  plunges  beneath  the  anterior  extensor  of 


THE  NERVES. 


the  phalanges,  giving  to  that  muscle  and  the  flexor  of  the  metatarsus  short,  but 
thick,  ramuscules.  It  descends  to  the  front  of  the  tarsus,  always  covered  by  the 
anterior  extensor  of  the  phalanges,  and  placed  at  the  external  side  of  the  anterior 
tibial  vessels.  When  it  arrives  below  the  tibia,  it  lies  immediately  alongside  the 
pedal  artery,  and  follows  it,  in  its  metatarsal  portion,  to  near  the  fetlock.     It 

then  separates  from  its  satellite  vessel — and 
passes  on  the  side  of  the  digit,  where  it  ends 
in  cutaneous  filaments  (Fig.  375,  5). 

Among  the  ramuscules  this  nerve  gives 
off  in  its  course,  are  cited  those  to  the  pedal 
muscle. 

2.  Branches  of  the  Muscles  of  the 
Deep  Pelvi-crural  Regiox.  —This  region 
comprises  the  obturator  internus,  gemelli, 
and  quadratus  femoris  muscles.  The  nerve 
sent  to  them  is  long  and  attenuated  ;  it  is 
detached  from  the  sciatic  nerve  at  the  middle 
of  the  supra-cotyloid  ridge,  and  descends 
with  that  trunk  behind  the  coxo-femoral 
articulation,  to  distribute  its  terminal  di- 
visions to  the  above-named  muscles.  The 
longest  and  thickest  of  these  goes  to  the 
quadratus  femoris.  That  passing  to  the 
obturator  internus  re-enters  the  pelvic  cavity 
by  the  small  sacro-sciatic  notch,  and  ascends 
to  the  vicinity  of  the  ilio-sacral  articulation. 

3.  Branch  to  the  Ischio-tibial,  or 
Posterior  Crural  Muscles. — This  branch 
is  thick  and  short.  It  arises  from  the  bend 
formed  by  the  great  femoro-popUteal  nerve 
at  the  gemelli  muscles,  and  soon  divides 
into  several  ramifications  which  are  distri- 
buted to  the  short  portion  of  the  biceps,  the 
middle  and  inferior  parts  of  the  semitendi- 
nosus,  and  into  the  semimembranosus.  Some 
of  the  filaments  for  the  latter  muscle  pass 
between  it  and  the  adductor  magnus,  in 
which  they  partly  terminate  (Fig.  474,  12). 

4.  External  Saphenic  Nerve. — This 
branch  commences  at  from  2  to  6  inches 
from  the  point  where  the  great  sciatic  nerve 
dips  between  the  two  portions  of  the  gastroc- 
nemius muscle.  It  is  placed  on  the  external 
portion,  and  descends  beneath  the  special 
aponeurotic  layer  covering  that  muscle,  to 

the  origin  of  the  tendon  of  the  hock.  It  then  receives  its  accessor!/  nerve — the 
reinforcing  filament  which  comes  from  the  cutaneous  branch  of  the  small  femoro- 
popliteal  nerve,  and  is  prolonged  beneath  the  tibial  aponeurosis  into  the  channel  of 
the  hock,  accompanying  the  external  saphenic  vein,  and  following  the  external 
border  of  the  fibrous  band  that  goes  to  strengthen  the  tendo-Achillis.     In  this 


EXTERNAL   NERVES   OF   THE   POSTERIOR 
LIMB. 

1, 2,  Great  sciatic  nerve ;  3,  external  saphenic 
nerve;  4,  external  popliteal  nerve;  5, 
anterior  tibial  nerve;  6,  musculo-cuta- 
neous  nerve;  7,  origin  of  the  peroneal- 
cutaneor.s  branch ;  8,  accessory  branch 
of  the  external  saphenic  nerve;  9,  ex- 
ternal plantar  nerve  with  its  divisions, 
which  cover  the  digital  artery  and  vein. 


THE  LUMBOSACRAL   PLEXUS.  881 

way,  it  occupies  the  same  situation  outside  the  hock  that  the  great  sciatic  does 
on  the  inner  side.  It  afterwards  passes  over  the  tarsal  region,  and  is  expended 
on  the  outside  of  the  metatarsus  in  several  filaments,  some  of  which  descend 
to  the  outer  aspect  of  the  digit  (Figs.  473,  11,  12  ;  475,  9). 

5.  Fasciculi  to  the  Posterior  Tibial  Muscles.— This  fasciculus  is 
composed  of  numerous  branches,  which  are  detached  together  from  the  sciatic 
nerve  on  its  passage  between  the  two  portions  of  the  gastrocnemius  muscle,  in 
the  form  of  a  thick  short  trunk.  The  muscles  of  the  superficial  layer — the 
gastrocnemius,  perforatus,  and  the  thin  fleshy  band,  improperly  designated  the 
"  small  plantaris  "  by  Veterinarians — receive  ramuscules  which  are  remarkable  for 
their  large  number  and  their  shortn  'ss.  Those  of  the  deep  layer  are  supplied 
by  filaments  from  a  single  long  and  thick  branch,  which  descends  between  the 
perforatus  and  the  internal  portion  of  the  gastrocnemius.  It  may  be  remarked, 
that  the  filament  going  to  the  so-called  small  plantaris  muscle  passes  underneath 
the  external  division  of  the  gastrocnemius,  outside  the  perforatus,  and  that,  by 
its  position,  it  exactly  represents  the  soleus  ramuscule  in  Man.  We  are,  therefore 
— with  Vicq-d' Azyr,  Cuvier,  and  others — justified  in  naming  this  little  muscle  the 
soleus,  instead  of  continuing  to  designate  it  the  small  plantaris,  which  appellation 
is  given  to  another  muscle. 

6.  In  its  course  along  the  tendo-Achillis,  the  sciatic  nerve  emits  some  slender 
cutaneous  filaments,  which  we  do  not  consider  worthy  of  further  notice. 

Terminal  Branches. 

Plantar  Nerves  (Fig.  473,  10,  12). — These  two  nerves  enter  the  tarsal 
sheath,  behind  the  perforans  tendon,  along  with  the  plantar  arteries.  Towards 
the  superior  extremity  of  the  cannon,  they  definitively  separate  from  each  other  ; 
the  external  is  carried  outwards  between  the  precited  tendon  and  the  rudimentary 
metatarsal  bone ;  the  internal  is  placed  with  that  tendon,  and  follows  the 
posterior  border  of  the  inner  metatarsal  bone.  Both  afterwards  descend  on  the 
fetlock,  where  they  comport  themselves  like  the  analogous  nerves  of  the  anterior 
limb. 

Differential  Characters  in  the  Lumbo-sackal  Plexus  of  the  other  Animals. 

As  was  tlie  case  with  the  brachial  plexus,  so  with  this;  the  diflferences  observed  being 
trifling  in  the  upper  part  of  the  limb,  but  more  numeious  and  important  in  the  region  of  the 
foot,  the  complexity  ot  arrangement  varying  with  the  species. 

Ruminants. — The  lumbo-sacral  plexus  of  these  animals  is  constituted  by  two  lumbar  and 
tl\ree  sacral  nerves,  as  in  Solipeds ;  but  tlie  third  sacral  only  gives  a  very  fine  filament,  which 
reaches  the  second  in  passing  downward  and  forward. 

At  the  femoro-tibial  articulation,  the  branches  of  the  plexus  are  similar  to  those  in  the 
Horse.     Below  that  articulation,  the  following  disposition  has  been  observed  in  the  Sheep. 

Tlie  muscido-cutaneous  branch  of  the  popliteal  is  long  and  thick.  It  descends  on  the 
anterior  face  of  the  metatarsus,  and  at  the  metatnrso-phalangeal  articulation  bifurcates,  the 
branches  forming  the  dorsal  collaterals  of  the  digits.  The  anterior  tibial  nerve  presents  two 
branches  parallel  to  the  tibial  vessels;  one  passes  along  the  metatarsal  region,  and  when  it 
arrives  at  the  bottom  of  the  groove  between  the  condyles  of  the  metatarsus,  it  divides  into  two 
branches  that  constitute  the  deep  collaterals  of  the  digits ;  these  collaterals  furnish  filaments 
to  the  posterior  face  of  the  digital  region. 

The  great  sciatic  resembles  that  of  Solipeds.  Its  terminal  branches — or  plantar  nerves — 
differ  from  those  of  the  Horse,  in  the  absence  of  the  transverse  anastomosis  that  unites  the  two 
cords  in  the  region  of  the  tendons. 

Pig. — The  lumbo-sacral  plexus  of  this  animal  Is  composed  of  two  lumbar  and  three  sacral 
nerves;  reckoning,  of  course,  as  a  sacral  nerve,  the  trunk  that  escapes  from  between  the  last 


882  TEE  NERVES. 

lumbar  vertebra  and  the  sacrum.  The  plexus  may  be  divided  into  two  povtinns.  the  first 
furnishing  a  femoral  and  an  obturator  nerve.  The  internal  saphenic  branch  of  the  femoral  nerve 
is  lone  and  voluminous;  at  its  origin  it  is  as  large  as  the  branch  }ia8sinK  to  the  anterior 
muscles  of  the  thigh,  and  it  descends  on  the  inner  face  of  the  metatarsus,  forming  the  dorsal 
collateral  of  the  internal  digit. 

The  great  sciatic  is  voluminous  and  round.  The  branches  it  gives  to  the  muscles  of  the 
pelvis  and  femur  are  disposed  nearly  as  in  Solipeds  and  Kuminants ;  but  differences  are 
observed  in  the  external  popliteal  and  the  terminal  branches. 

The  musculo-cntaneous  nerve  reaches  the  metatarsal  region,  where  it  separates  into  three 
branches,  which  form  the  dorsal  collaterals  of  the  digits. 

Tlie  anterior  tibial  nerve  descends  between  the  two  principal  metatarsals,  and  at  the  root 
of  the  middle  digits  divides  to  anastomose  with  the  plantar  nerves.  Of  these  the  external  is 
small,  and  gives  collaterals  to  the  two  external  digits;  the  internal,  the  largest,  descends 
between  the  two  principal  digits,  where  it  bifurcates;  above,  it  gives  a  branch  to  tiie  internal 
digit. 

Carnivora. — In  these  animals,  the  lumbo-sacral  plexus  is  formed  by  the  last  four  lumbar 
and  the  first  two  sacral. 

The  crural  and  obturator  nerves,  which  arise  from  the  fourth,  fifth,  and  sixth  lumbar  nerves, 
offer  nothing  particular  in  their  disposition. 

The  internal  saphenic  branch  is  as  long  as  in  the  Pig;  it  passes  to  the  internal  face  of  the 
tarsus,  lies  alongside  the  fourth  metatarsal  bone,  and  forms  the  internal  dorsal  collateral  of 
the  fourth  toe. 

The  great  sciatic  may  be  described  as  having,  as  in  Man,  two  terminal  branches  which 
separate  a  little  above  the  posterior  face  of  the  femoro-tibial  articulation.  The  external 
popliteal  nerve  passes  to  the  surface  of  the  external  gastrocnemius,  enters  between  the  common 
long  flexor  of  the  toes  and  the  long  lateral  peroneal  muscle,  where  it  bifurc;ites.  The  musculo- 
cutaneous branch  descends  beneath  the  latter  muscle  to  the  lower  third  of  the  leg,  when  it 
becomes  superficial,  and,  accompanied  by  a  vein,  is  lodged  in  the  interspace  between  that 
muscle  and  the  anterior  tibial ;  it  passes  in  front  of  the  tarsus,  and  reaches  the  upper  part  of 
the  metatarsus,  where  it  divides  into  three  divisions.  It  must  be  mentioned  that  at  the  tibio- 
tarsal  articulation  is  thrown  off  a  very  fine  cord,  which  is  directed  outwards,  and  forms  the 
external  dorsal  collateral  of  the  first  toe.  Each  of  its  three  terminal  branches  courses 
along  an  intermetatarsal  space,  and  at  the  metatarso-phalangeal  articulations  separates  into 
two  filaments,  whence  results  the  following  distribution:  the  external  branch  forms  the 
internal  dorsal  collaterals  of  the  first  toe  and  external  of  the  second ;  the  middle  constitutes 
the  internal  dorsal  collaterals  of  the  second  toe  and. external  of  the  third;  lastly,  the  internal 
furnishes  the  internal  dorsal  collaterals  of  the  third  toe  and  external  of  the  fourth.  The 
anterior  tibial  nerve  accompanies  the  artery  of  that  name,  descends  along  the  external  face  of 
the  tibia,  and  terminates  in  two  branches  at  the  tarsus.  Of  these,  one  is  distributed  to  the 
tarsal  articulations  and  the  pedal  muscle:  the  other,  internal,  enters  the  intermetatarsal 
space,  and  at  the  corresponding  metatarso-phalangeal  joints  anastomoses  with  the  internal 
branch  of  the  musculo-cutaneous  nerve,  and  is  lost  in  the  same  parts.  Tiie  internal  popliteal 
forms  the  second  terminal  branch  of  the  great  sciatic  nerve,  and  in  the  Dog  and  Cat  repre- 
sents that  portion  of  the  latter  which,  in  the  Horse,  is  situated  behind  the  femoro-tibial 
articulation.  It  is  continued  by  the  posterior  tibial  nerve,  which  terminates  by  the  two 
plantar  nerves.  During  its  course,  the  external  popliteal  furnishes  articular  and  muscular 
filaments,  as  well  as  cutaneous  twigs  subsequently ;  among  the  latter  may  be  mentioned  the 
external  saphenic,  which  arises  by  two  brandies,  and  is  expended  behind  the  malleolus,  at  the 
outer  side  of  the  tarsus.  The  plantar  nerves  are  external  and  internal ;  the  latter  lies  at  the 
inner  border  of  the  tendon  of  the  superficial  fiexor  muscles  of  the  phalanges,  and  when  it 
joins  the  middle  of  the  metatarsus,  it  detaches  a  fine  filament  that  forms  tlie  internal  plantar 
collateral  of  the  fourth  toe ;  it  then  passes  obliquely  towards  the  first  toe,  at  the  deep  face  of 
the  above-named  tendon,  and  successively  gives  off  three  filaments— one  for  each  intermetar 
tarsal  space.  These  filaments  anastomose  with  the  terminal  branches  of  the  external  plantar, 
at  the  metatarso-phalangeal  articulations;  the  first  two  filaments  supply  the  large  cushion 
of  the  paw. 

The  external  plantar  nerve  passes  between  the  two  flexor  tendons  of  the  toes,  where  it 
gives  a  filament  that  constitutes  the  external  plantar  collateral  of  the  first  toe.  It  is  after- 
wards placed  outside  the  deep  flexor,  then  enters  beneath  the  short  flexor  and  divides  into 
several  branches— muscular  and  digital.  Each  of  the  latter— three  in  number— passes  into  a 
corresponding  interosseous  space  and  bifiurcates  at  the  metatarso-phalangeal  articulations, 
receiving  filaments  from    he  internal  plantar,  and  forming  the  following  plantar  collaterals : 


THE  LUMBOSACRAL   PLEXUS 


Fig.  476. 


the  internal  of  the  first  toe,  internal  and  external  of  the  second,  internal  and  external  of  the 
third,  and  external  of  the  fourth  digit. 

Comparison  of  the  Lumbo-sacral  Plexus  in  Man  with  that  of  Animals. 

It  is  usual,  in  human  anatomy,  to  describe  a  lumbar  and  a  sacral  plexus. 

The  lumbar  plexus  is  constituted  by  the  anastomoses  of  the  anterior  branches  of  the  five 
lumbar  nerves ;  >  these  are  united  by  fine  filaments,  which  are  not  intricately  associated.  The 
divisions  of  this  plexus  are  distinguished  as  collateral  and  terminal  branches.  The  first, 
destined  to  the  upper  part  of  the  limb  and  the  skin  covering  the  external  genital  organs,  are 
represented  in  Solipeds  by  the  ramifications  of  the  lumbar  nerves,  which  have  been  separately 
described.  The  terminal  branches  are 
the  obturator  crural,  and  anterior 
femoral  (or  anterior  crural).  There  is 
nothing  to  be  said  respecting  the  ob- 
turator nerve ;  it  leaves  the  pelvis  by 
the  obturator  foramen,  as  in  all  the 
animals  mentioned.  The  crural  has 
been  described  as  having  four  terminal 
branches:  the  internal  and  external 
musculo-cutaneous,  the  nerve  of  the 
triceps  crureus  {muscular  branch),  and 
the  internal  saphenous.  The  two 
musculo-cutaneous  branches  have  their 
analogue  in  the  Horse,  in  the  filament 
we  have  named  the  accessory  branch 
of  the  internal  saphenic.  The  nerve 
of  the  triceps  is  expended  in  the  an- 
terior rectus,  and  the  vastus  intern  us 
and  externus.  The  saphenic  de- 
scends between  the  muscles  of  the 
inner  aspect  of  the  tliigh,  beneath  the 
aponeurosis,  and  becomes  superficial 
at  a  short  distance  from  the  condyle 
of  the  femur,  giving  a  patellar  branch 
that  divides  in  the  skin  of  the  knee, 
and  a  tibial  branch  that  is  expended 
on  the  inner  face  of  the  tarsal  articula- 
tions and  the  foot. 

The  sacral  plexus  comprises  the 
first  three  sacral  nerves,  to  which  is 
added  a  lumbo-sacral  branch  furnished 
by  the  lumbar  nerves,  and  a  fine  fila- 
ment that  ascends  from  the  fourth 
eacral. 

Ten  collaterals  and  a  terminal 
branch  arise  from  this  plexus. 

The  collateral  branches  are  divided 
into  intra-pelvic  and  extra-pelvic: 
they  are  five  in  each  group.  The  first 
are  destined  to  the  muscles  of  the 
inner  aspect  of  the  pelvis,  and  to  those 
of  the  perineum  and  the  skin  of  this 


lumbar  plexus  of  man. 
1,  Right  gangliated  cord  of  .sympathetic ;  2,  abdominal 
aorta  ;  3,  3,  last  dorsal  nerves ;  4,  psoas  parvus ;  5, 
quadratus  lumborum ;  6,  psoas  magnus;  7,  7,  ilio- 
hypogastric nerves;  8.  iliacus  iuternus;  9,  9,  ilio- 
inguinal nerve;  10,  lumbo-sacral  nerve;  11,  genito- 
crural  nerve;  12,  gluteal  nerve;  13,  iliac  branch  of 
ilio-hypogastric  nerve;  14,  sacral  plexus;  15,  1.5,  15, 
external  cutaneous  nerves;  17,  transversalis  abdomi- 
nis; 19,  obliquus  internus  ;  21,  obliquus  externus; 
23,  23,  anterior  crural  nerves ;  25,  25,  obturator 
nerves ;  27,  27,  crural  branch  of  genito-crural  nerve  ; 
2>,  genital  branch  of  genito-crural  nerve;  31, external 
iliac  artery ;  33,  external  abdominal  ring. 


region.     The  second  are  distributed  to 

the  muscles  on  the  outer  aspect  of  the  pelvis,  and  the  skin  on  the  posterior  face  of  the  thigh. 

They  are — 

1.  Visceral  branches  that  descend  on  the  sides  of  the  rectum  and  are  lost  in  the  hypogastric 
plexus.  2.  Nerve  of  the  elevator  of  the  anus.  3.  Exmorrhoidal  or  anal  nerve.  4.  Nerve  of  the 
internal  obturator  that  apptars  to  arise,  in  the  Horse,  from  the  sciatic  trunk.  5  Internal 
fudic,  which  has  been  described  with  the  sacral  nerves.     In  Man  this  nerve  leaves  the  pelvis 


('  Wilson  says  the  four  upper  lumbar  nerves  and  the  last  dorsal ;  Heath  gives  the  same 
constitution.) 


884  THE  NERVES. 

by  the  great  sciatic  notch  (or  foramen),  and  retuma  to  it  by  the  lesser ;  within  the  iachiatio 

F'g-  477.  Fig.  478. 


ITERVES    AT    THE    POSTERIOR   ASPECT  OF 
HUMAN    LEG. 

1,  Popliteal  artery ;  2,  great  sciatic  nerve ; 
3,  adductor  magnus;  4,  biceps;  5,  superior 
internal  articular  artery;  6,  external  pop- 
liteal nerve;  7,  gastrocnemius  (cut);  8, 
anterior  tibial  artery  ;  9,  tendon  of  semi- 
membranosus ;  10,  peroneus  longus  ;  11, 
sural  arteries  and  nerves ;  12,  peroneal 
artery ;  13,  internal  popliteal  nerve  ;  14, 
tibialis  posticus;  15,  portion  of  soleus; 
16,  peroneus  brevis ;  17,  popliteus;  18, 
flexor  longus  pollicis;  19,  posterior  tibial 
nerve ;  20,  calcanean  branch  of  posterior 
tibial  nerve  ;  21,  posterior  tibial  artery  ; 
22,tendn-Achillis  ;  23,  flexor  longus  digit- 
orum;  25,  tendon  of  tibialis  posticus;  27, 
plantar  nerves;  29,  plantar  arteries. 


NERVES  AT   THE    FRONT    ASPECT   OF    HUMAN 
LEG. 

1,  External  popliteal  nerve ;  2,  anterior 
tibial  artery;  3,  musculo-cutaneous  nerve; 
4,  anterior  tibial  nerve;  5,  peroneus 
longus;  6,  tibialis  anticus;  7,  extensor 
longus  digitorum  ;  8,  anterior  annular 
ligament;  9,  peroneus  brevis;  10,  tendon 
of  extensor  proprius  pollicis;  11,  extensor 
proprius  pollicis;  12,  dorsal  artery  of  foot; 
13,  point  at  which  the  musculo-cutaneous 
nerve  pierces  the  fascia  and  bifurcates;  14, 
tendon  of  tibialis  anticus ;  15,  internal 
branch  of  musculo-cutaneous  nerve;  16, 
cutaneous  branch  of  anterior  tibial  nerve; 
17,  external  branch  of  musculo-cutaneous 
nerve;  19,  deep  branch  of  anterior  tibial 
nerve;  21,  external  saphenic  nerve;  23, 
extensor  brevis  digitorum. 


THE  GREAT  SYMPATHETIC  NERVOUS  SYSTEM.  885 

tuberosity  it  divides  into  two  branches — an  inferior  or  perineal,  and  a  superior  or  dorsalis  penis 
nerve.  The  latter  is  placed  on  the  dorsum  of  the  penis,  and  reaches  tlie  mucous  membrane  of 
the  glans  and  prepuce;  the  former  does  not  go  beyond  the  muscles  and  integuments  of  the 
perineum.  6.  The  superior  gluteal  nerve.  7.  Nerve  of  the  pyramidalis.  8.  Nerve  of  the 
superior  gemellus.  9.  Nerve  of  the  inferior  gemellus  and  quadratus  cruralis.  10.  The  small 
sciatic,  or  inferior  gluteal  nerve,  the  inferior  or  femoral  branch  of  whicii  is  very  long,  descend- 
ing, as  it  does,  to  the  middle  of  the  posterior  face  of  tlie  thigh,  beneath  the  crural  aponeurosis, 
to  the  popliteal  space,  where  it  becomes  superficial,  and  terminates  in  the  skin  of  the  upper 
portion  of  the  leg. 

The  terminal  branch  of  the  sacral  plexus  forms  the  great  sciatic  nerve,  the  distribution  of 
which  is  the  same  as  that  of  Carnivora.  The  collateral  ramuscules  of  the  great  sciatif  are  the 
branch  of  the  long  portion  of  the  biceps ;  the  semitendinosus  and  semimeiubranosus  branch  ;  the 
branch  to  the  great  adductor;  and,  lastly,  tliat  to  the  short  portion  of  the  biceps.  It  terminates 
by  the  external  and  internal  popliteal. 

Tiie  musculo-cutaneous  and  anterior  tibial,  continuations  of  the  external  popliteus,  comport 
themselves  almost  the  same  as  in  the  Dog.  They  form  dorsal  collaterals  to  the  third,  fourth, 
and  fifth  toes,  as  well  as  to  tlie  second. 

The  internal  popliteal  presents  an  external  saphenous  nerve  that  passes  along  the  external 
border  of  the  foot,  and  has,  in  addition,  a  branch  that  ascends  on  the  dorsum  of  that  organ. 
The  external  saphenous  furnishes  the  dorsal  collaterals  to  the  first  toe,  and  the  external 
collateral  to  the  second.  Tlie  posterior  tibial  nerve  continues  the  internal  sciatic  in  the  leg;  it 
terminates  in  the  plantar  nerves.  The  internal  plantar  furnishes  the  collateral  nerves  to  the 
fifth,  fourth,  and  third  toes,  and  the  internal  collateral  of  the  second  toe.  The  external 
divides  into  three  branches :  the  two  superficial  branches  form  the  collaterals  of  the  first  toe, 
and  the  external  collateral  of  the  second ;  the  deep  branch  passes  inwards,  behind  the  inter- 
osseous muscles,  and  is  expended  in  those  of  the  fourtii  space,  after  giving  filaments  to  the 
oblique  abductor  of  the  large  toe,  transverse  abductor,  last  two  lumbricales,  to  the  interosseous, 
and  very  fine  filaments  to  the  articulations  of  the  tarsus  with  tlie  metatarsus. 

It  will  therefore  be  seen,  that,  in  Man,  the  brandies  of  the  deep  trunk  of  the  external 
plantar  join  those  of  the  internal  plantar,  to  form  the  collateral  nerves. 


CHAPTER  III. 

THE   GREAT    SYMPATHETIC   NERVOUS    SYSTEM. 

Preparation  of  the  Great  Sympathetic— 7%e  same  subject  ought  to  suffice  for  the  prepara- 
tion of  this  as  well  as  for  the  pneumogastric  and  spinal  nerves.  After  placng  the  animal  in 
the  first  position,  the  intestines  are  remuved,  one  of  the  posterior  limbs  cut  off,  and  the  greater 
portion  of  the  os  innominatum  cleared  away  by  sawing  through  the  symphysis  pubis  and  the 
neck  of  the  ilium ;  the  dissection  of  all  the  abdomino-pelvic  portion  of  the  system,  and  that  of 
the  terminal  branches  of  the  pneumogastric  nerve,  is  then  proceeded  with.  The  anterior  limb 
of  the  same  side  should  be  afterwards  detached,  the  scapula  having  been  previously  sawn 
across  its  middle  part,  and  tlie  thorax  thrown  open  by  the  ablation  of  the  entire  costal  wall,  in 
sawing  throu^di  the  sternal  cartilages  below,  and  the  ribs  above,  at  their  superior  extremity. 
All  the  thoracic  portion  of  the  ganglionic  nervous  apparatus,  and  the  pneumogastric  nerves, 
may  then  be  prepared,  Notliing  more  remains  to  be  accomplished  except  the  dissection  of 
tlie  sympathetic  and  the  vagus  nerve  in  the  cervico-cephalic  region,  with  that  of  the  spinal 
nerve ;  this  operation  is  not  attended  with  any  difficulty,  and  should  be  preceded  by  the  extir- 
pation of  a  branch  of  the  inferior  maxilla.  It  is  useful  to  inject  the  arteries  previously ;  as 
then  the  filaments  of  the  sympathetic  that  lie  alongside  the  vessels  of  the  different  organs  in 
the  abdominal  cavity  can  be  more  easily  followed. 

The  great  sympathetic,  also  named  the  trisplanchnir  system  ((nrXavxvov,  an 
intestine  or  viscus),  because  of  its  position  and  destination,  is  the  nervous  appa- 
ratus of  the  organs  of  vegetative  life. 


THE  NERVES. 


As  has  been  already  shown  in  the  general  consideration  of  the  nerves  and 
the  whole  nervous  system,  this  apparatus  has  for  its  base  two  long  cords  extend- 
ing from  the  head  to  the  tail,  underneath  the  vertebral  column,  and  to  the  right 
and  left  of  the  mesian  line.  Towards  the  last  sacral  vertebra,  a  portion  of  these 
two  cords  converge  towards  each  other,  and  lie  beside  the  mesial  coccygeal 
artery.  '  Some  anatomists  think  that  the  great  sympathetic  does  not  stop  at  this 
point,  but  is  prolonged  beneath  the  coccygeal  vertebrae,  where  it  enters  a  gan- 
glion that  has  been  described  of  late  years  as  the  "  coccygeal  gland  "  {Luschka's 
gland) ;  this,  however,  is  not  a  nerve-ganglion. 

Each  cord  presents  on  its  course  numerous  ganglia,  to  which  it  owes  its 
chain-like  aspect ;  they  are  usually  elliptical  in  shape,  though 
they  may  also  be  round  or  semilunar  ;  some  are  studded  with 
prolongations  at  their  borders.  Beneath  each  of  the  regions 
of  the  spine,  these  ganglia  are  equal  in  number  to  the 
vertebrse,  with  the  exception  of  the  cervical  region,  in  which 
there  are  only  two — one  at  the  top,  the  other  at  the  bottom, 
of  the  neck. 

To  this  chain  arrive  afferent  branches,  by  the  union  of 
which  it  is  constituted  ;  these  branches  are  furnished  by  the 
nerves  of  the  medulla  oblongata  and  the  inferior  spinal 
branches,  except  those  of  the  coccygeal  region.  The  ajfferent 
branches  join  the  sympathetic  at  each  ganglion  ;  but  as  there 
are  only  two  ganglia  in  the  region  of  the  neck,  the  afferent 
filaments  of  the  cervical  nerves  are  grouped  in  such  a  manner 
as  to  reach  the  superior  and  inferior  ganglion. 

Those  nerves  which  are  given  off  from  the  ganglia  to  be 
distributed  to  the  viscera,  are  named  the  effei-ent  or  emergent 
branches.  They  are  interlaced  around  the  arteries  to  reach 
their  destination,  forming  plexuses  on  the  surface  of  these 


STMPATHETIC  GAN- 
GLION FROM  A 
PUPPY. 

a,  a,  Trunk  of  the 
sympathetic  nerve ; 

b,  communicating 
branches  from  a 
spmal  nerve;  these 
diviJe  into  two  fas- 
ciculi which  pass 
upwards  and  down- 
wards in  the  trunk; 

c,  c,  the  ganglion 
composed  of  gan- 
glion cells;  d, small 
branch,  probably 
destined  to  accom- 
pany an  artery ;  e, 
visceral  branch. 


This  general  idea  of  the  disposition  of  the  great  sym- 
pathetic is  sufficient  to  show  that  its  double  ganglionic  chain 
does  not  represent  two  particular  nerves  arising  at  one 
determinate  point,  and  ending  at  another.  Properly  speak- 
ing, they  have  neither  origin  nor  termination  :  they  are 
always  giving  off  branches,  which  are  as  frequently  replaced 
by  others.  In  this  way  they  might  be  compared  to  the  median 
spinal  artery,  which  offers  somewhat  the  same  mode  of  con- 
stitution— with  its  afferents  supplied  by  the  spinal  branches 
from  the  intervertebral  foramina,  and  its  efferents  destined  to  the  substance  of 
the  spinal  cord. 

Structure. — The  ganglia  of  the  great  sympathetic  differ  but  little  in  their 
structure  from  the  spinal  gangha,  which  have  been  already  described.  They 
have  an  envelope  of  connective  tissue,  which  sends  very  fine  septa  into  their 
interior.  In  the  spaces  are  cells  a  little  smaller  and  paler  than  those  of  the 
spinal  ganglia  ;  they  are  round,  or  furnished  with  poles  that  bring  them  into 
communication  with  the  afferent  and  efferent  nerve-tubes  ;  there  are  also,  in  the 
ganglia,  tubes  which  only  pass  through  it,  and  merely  lie  beside  the  cells. 

The  afferent  branches  of  the  ganglia  have  not  the  white  tint  of  the  cerebro- 
spinal nerves  ;  they  are  named  the  greij  nerves.     They  owe  their  colour  to  the 


THE  GREAT  SYMPATHETIC  NERVOUS  SYSTEM.  887 

fibres  of  Remak,  which  they  contain  in  large  quantity.  With  these  nucleated 
fibres  are  associated  fine  double-contoured  fibres — myelin  fibres — which  proceed 
from  the  communicating  rami,  or  afferent  filaments  supplied  by  the  spinal  nerves  ; 
these  fibres  often  leave  the  ganglia  to  pass  directly  to  organs. 

In  describing  the  sympathetic  chain,  it  is  divided  into  five  sections :  a  cranial^ 
cervical,  dorsal,  lumbar,  and  sacral. 

1.  Cranial  Portion  of  the  Sympathetic. 

This  is  composed  of  the  spheno-palatine,  ophthalmic,  and  otic  ganglia,  all  of 
which  communicate  with  the  superior  cervical  ganglion.  Their  description  has 
been  given  with  that  of  the  fifth  cranial  pair  of  nerves. 

2.  Cervical  Portion  of  the  Sympathetic. 

The  cervical  section  of  the  ganglionic  chain  is  formed  by  two  large  ganglia 
placed  one  at  the  top,  the  other  at  the  bottom,  of  the  neck,  and  united  to  each 
there  by  an  intermediate  cord. 

A.  Superior  Cervical  or  Guttural  Ganglion  (Fig.  480,  1). — This 
ganglion  is  a  very  elongated  fusiform  body,  lying  beside  the  internal  carotid 
artery,  comprised  with  it  in  a  particular  fold  of  the  membrane  forming  the 
guttural  pouch,  and  therefore  situated  in  front  of  the  transverse  process  of 
the  atlas,  in  proximity  to  the  glosso-pharyngeal,  pneumogastric,  spinal,  and 
hypoglossal  nerves,  as  well  as  the  inferior  branch  of  the  first  cervical  pair.  All 
these  nerves  communicate  with  the  ganglion  by  slender  filaments,  and  in  this 
way  form  around  it  a  veritable  plexus,  which  has  been  designated  the  guttural 
plexus  by  Veterinary  Anatomists. 

Afferent  Branches. — These  are  communicating  filaments  belonging  to  the 
nerves  already  enumerated.  They  do  not  possess  sufficient  importance  to  merit 
particular  mention.  We  may  notice  the  existence  of  the  filaments  supplied  by 
the  inferior  branches  of  the  first  four  cervical  nerves. 

Efferent  Branches. — These  are  :  1.  Branches  accompanying  the  internal 
carotid  arteiy  into  the  cranium.  2.  A  thick  fasciculus  which  reaches  the  origin 
of  the  three  terminal  divisions  of  the  common  carotid.  3.  Small  filaments  to 
the  membrane  of  the  guttural  pouch  and  the  wall  of  the  pharynx. 

The  following  are  the  principal  anatomical  characters  of  these  three  orders 
of  branches  : — 

a.  The  satellite  branches  of  the  internal  carotid  artery  arise  at  the  superior 
extremity  of  the  ganglion.  They  may  vary  in  number.  Two  are  generally 
found,  of  unequal  volume — a  posterior,  and  an  anterior,  which  is  the  smallest. 
They  interlace  around  the  internal  carotid  in  anastomosing  with  each  other,  and 
with  that  vessel  enter  the  cavernous  sinus,  where  they  form,  by  their  divisions, 
a  little  plexiform  apparatus  named  the  cavernous  plexus,  the  various  branches  of 
which  connect  it  with  several  of  the  cranial  nerves.  Among  these  branches  are 
remarked  :  1.  Some  filaments  joined  to  analogous  filaments  from  the  opposite 
side,  on  the  transverse  anastomosis  which  unites  the  two  internal  carotids  in  the 
cavernous  sinus.  2.  A  branch  lying  beside  the  great  petrosal  nerve,  and 
concuiTing  in  the  formation  of  the  Vidian  nerve,  which  enters  the  spheno-palatine 
ganglion.  3.  A  ramuscule  going  to  the  ophthalmic  ganglion,  in  company  with 
fibres  from  the  ophthalmic  branch  of  the  fifth  pair.  4.  Several  filaments  passing 
to  the  Gasserian  ganglion.  5.  Branches  which  mix  with  the  fibres  of  the  three 
motor  nerves  of  the  eye. 


TEE  NEBVES. 


THE  GREAT  SYMPATHETIC  NERVOUS  SYSTEM.  889 

b.  The  inferior  carotid  fasciculus,  sent  to  the  terminal  extremity  of  the 
sommon  carotid,  escapes  from  the  inferior  part  of  the  guttural  ganglion. 
Frequently  at  its  origin  it  is  only  a  thick  cord,  but  ordinarily  it  is  composed, 
from  its  commencement,  of  several  branches  bound  to  one  another  by  com- 
municating filaments.  Reaching  their  destination,  these  branches  meet  ramuscules 
emanating  from  the  glosso-pharyngeal  and  pneumogastric  nerves,  and  anastomose 
with  them  to  form,  around  the  origin  of  the  three  terminal  branches  of  the 
common  carotid,  the  so-called  carotid  plexus,  the  ramifications  of  which  almost 
exclusively  follow  the  external  carotid,  the  greater  part  being  distributed  to  the 
glands  and  salivary  lobules.  In  Man,  the  division  which  follows  the  spheno- 
spinal  artery  passes  to  the  otic  ganglion  ;  the  same  takes  place,  no  doubt,  in 
animals. 

c.  The  guttural  or  pharyngeal  filaments,  arising  from  the  anterior  border  of 
the  ganglion  and  the  inferior  carotidean  fasciculus,  are  generally  very  delicate. 
Those  which  reach  the  superior  wall  of  the  pharynx  concur,  with  the  glosso- 
pharyngeal and  the  pneumogastric,  to  form  the  phan/ngeal  plexus. 

B.  Intermediate  Cord  of  the  Two  Cervical  Ganglia. — This  cord 
leaves  the  inferior  extremity  of  the  superior  cervical  ganglion,  lies  close  beside 
the  pnemnogastric  nerve,  which  always  exceeds  it  in  volume,  and  descends  to  the 
entrance  of  the  thorax,  where  it  separates  from  the  vagus  nerve,  and  joins  the 
inferior  cervical  ganglion.  It  neither  receives  nor  gives  off  any  branch  in  its 
course. 

G.  Inferior  Cervical  Ganglion  (Fig.  480,  2). — Generally  thicker  than 
the  superior,  this  ganglion  is  placed  within  the  costal  insertion  of  the  inferior 
scalenus.  The  right,  always  a  little  more  anterior  than  the  other,  is  applied 
immediately  against  the  side  of  the  trachea.  That  of  the  left  side  is  separated 
from  it  by  the  oesophagus.     Both  are  related,  externally,  to  the  vertebral  artery. 

The  inferior  cervical  ganglion  is  very  liable  to  vary,  and  become  irregular  in 
form.  It  is  sometimes  lenticular,  at  others  more  or  less  elongated,  always 
stellate,  and  not  unfrequently  double.  In  the  latter  case — which  is  perhaps  more 
frequent  in  the  left  than  the  right — its  two  portions  are  distinguished  into  anterior 
and  posterior.  The  last  forms  the  inferior  cervical  ganglion,  properly  called  (Fig. 
480,  2)  ;  the  former  is  much  smaller,  and  is  bound  to  the  other  by  a  wide  and 
short  greyish  band,  constituting  what  has  been  designated  in  Man  the  middle 
cervical  ganglion  (Fig.  480,  3). 

In  front,  the  ganglion  which  we  are  describing  receives  the  cord  intermediate 


to  2,  Cervical  portion  of  the  sympathetic  chain;  1,  superior  cervical  ganglion,  in  the  middle  of  the 
guttural  plexus ;  2,  inferior  cervical  ganglion ;  3,  middle  cervical  ganglion ;  4,  intermediate 
cervical  cord,  intimately  united  at  its  middle  portion  with  the  pneumogastric  nerve;  5,  cardiac 
nerves;  6,  dorsal  portion  of  the  sympathetic  chain;  7,  great  splanchnic  nerve;  8,  lesser  splanchnic 
nerve;  9,  semilunar  ganglion,  centre  of  the  solar  plexus;  10,  portion  of  the  hepatic  artery 
encircled  by  its  splexus ;  11,  the  splenic  artery,  ditto ;  12,  the  gastric  artery,  ditto ;  13.  the 
anterior  mesenteric  artery,  ditto;  14,  kidney,  elevated,  receiving  the  renal  plexus  ;  15,  the  supra- 
renal capsule  with  its  plexus;  16,  lumbn-aortic  plexus;  17,  lumbar  portion  of  the  sympathetic 
chain;  18,  posterior  mesenteric  plexus;  19,  branches  from  it  passing  to  the  anterior  mesenteric 
plexus  :  20,  spermatic  plexus ;  21,  branches  going  to  the  pelvic  plexus  ;  22,  sacral  portion  of  the 
sympathetic  chain ;  23,  pelvic  plexus;  24,  afferent  brauches  furnished  to  the  sympathetic  by  the 
spinal  pairs;  24',  the  cord  which  receives  six  of  the  cervical  ra.m\xs,cxx\e%\  2h,  pneumogastric 
nerve;  26,  superior  laryngeal  (the  pharyngeal  branch  is  seen  to  be  detached  from  the  pneumo- 
gastric a  little  below);  27,  inferior  laryngeal  nerve  of  the  right  side;  28,  that  of  the  left  side  at 
the  point  where  it  bends  round  the  arch  of  the  aorta;  29,  nerves  of  the  bronchial  plexus  ;  30, 
superior  oesophageal  branch;  31,  inferior  ditto;  32,  spinal  nerve;  33,  hypoglossal  nerve;  34, 
glosso-pharyngeal  nerve  (represented  too  thick). 


890  THE  NERVES. 

to  the  two  ganglionic  enlargements  in  the  region  of  the  neck,  either  directly,  or 
through  the  medium  of  the  middle  cervical  ganglion,  when  that  is  present.  It  is 
continued  backwards  with  the  dorsal  portion  of  the  sympathetic  chain. 

Afferent  Branches. — These  are  two,  proceeding  from  the  cervical  pairs. 

One  is  a  thick  nerve,  satellite  to  the  cervical  vertebral  arteiy  (sometimes 
named  the  vertebral  plexus),  and  lodged  with  it  in  the  foramina  of  the  cervical 
vertebrae ;  it  is  formed  by  filaments  emanating  from  the  second,  third,  fourth, 
fifth,  sixth,  and  seventh  pairs  of  cervical  nerves,  and  thus  carries  in  a  mass,  to 
the  sympathetic,  the  contingent  of  afferent  nerve-fibres  of  the  majority  of  these 
nerves  (Fig.  480,  24'). 

The  other  branch  is  an  isolated  one,  proceeding  from  the  eighth  cervical  pair. 

Besides  these  afiferents,  there  ought  to  be  noticed  the  filaments  sent  by  the 
pneumogastric  nerve,  and  which  join  the  middle  cervical  ganglion,  when  it  is 
present  (see  the  description  of  the  pneumogastric  nerve). 

Efferent  Branches. — These  are  detached  from  the  posterior  and  inferior 
parts  of  the  ganghon,  and  for  the  most  part  proceed  to  the  heart.  Some  extremely 
fine  filaments  go  to  the  anterior  mediastinum,  or  pass  on  to  the  collateral  arteries 
of  the  brachial  trunk. 

The  cardiac  nerves  (Fig.  480,  5)  cross  the  base  of  the  pericardium,  alongside 
the  common  aorta,  and  are  then  distributed  to  the  tissue  of  the  auricles  and 
ventricles.  Some  follow  the  divisions  of  the  pulmonary  artery,  and  concur  in  the 
formation  of  the  bronchial  plexus. 

To  arrive  at  the  heart,  these  nerves  accompany  the  axillary  arteries  and  the 
trachea,  giving  origin,  on  the  inferior  face  of  the  latter,  to  a  very  large  fasciculus, 
named,  in  Veterinary  anatomy,  the  tracheal  plexus  ;  this  is  single,  and  is  travereed 
from  behind  to  before  by  the  two  recurrent  nerves,  which  give  or  receive  from  it 
numerous  filaments. 

The  cardiac  nerves  come  from  the  right  and  left  sides.  In  the  Horse  they 
usually  have  the  following  disposition  : — 

a.  On  the  left  side  are  four  nerves,  two  of  which — very  fine — proceed  from 
the  middle  cervical  ganglion  and  disappear  on  the  vessels  whicli  arise  from  the 
convexity  of  the  brachial  arteiy.  Of  the  other  two,  one  is  superficial,  the  second 
deep.  The  former — the  most  voluminous — begins  as  a  filament  from  the  middle 
cervical  ganglion,  and  passes  backwards  and  downwards,  forming  an  arching 
anastomosis  below  the  brachial  artery  with  a  branch  detached  from  the  inferior 
cervical  ganghon,  then  lies  beside  the  following.  The  deep  nerve  is  at  first 
formed  of  three  elements  :  1.  Medullary  fibres  furnished  by  the  spinal  pairs. 
2.  A  ramuscule  from  the  cervical  cord  of  the  sympathetic.  3.  A  slender  filament 
which  leaves  the  left  pneumogastric,  near  the  entrance  to  the  thorax.  It  places 
itself  in  the  direction  of  the  heart,  adheres  to  the  superficial  nerve,  is  inflected  on 
the  concavity  of  the  brachial  artery,  margins  that  vessel  on  the  left,  and  insinuates 
itself  between  the  aorta  and  the  pulmonary  artery.  At  this  point,  these  nerves 
are  distributed  to  the  heart  and  large  vessels,  a  branch  passing  beneath  the 
right  auricle  and  entering  the  cardiac  muscle  ;  a  second  branch  ramifies  on  the 
commencement  of  the  pulmonary  artery  and  on  the  right  ventricle  ;  two  other 
grey,  plexif orm  branches  anastomose  more  or  less  between  the  aorta  and  pulmonary 
arteiy,  and  unite  beneath  the  arch  of  the  aorta,  with  a  nerve  from  the  right  side, 
then  descend  in  the  vertical  groove  on  the  heart,  to  be  expended  in  the  left 
ventricle ;  lastly,  other  ramuscules,  parallel  to  the  pneumogastric,  go  to  the 
pulmonary  artery  and  aorta. 


THE  GEE  AT  SYMPATHETIC  NERVOUS  SYSTEM.  891 

5.  On  the  right  side  are  two  principal  cardiao  nerves,  and  four  secondary 
filaments.  The  first  cardiac  nerve  is  a  long  branch  that  arises  at  fhe  middle 
cervical  ganglion.  It  is  formed  by  fibres  from  the  sympathetic,  and  by  a 
fasciculus  furnished  by  the  right  pneumogastric,  at  the  entrance  to  the  thorax  ; 
it  also  probably  receives  medullary  fibres  through  the  medium  of  a  communicating 
branch  between  the  middle  and  inferior  ganglion.  This  nerve  is  reinforced  by 
two  filaments  that  proceed  from  the  inferior  cervical  ganglion,  and  sometimes 
from  the  second  middle  ganglion,  one  of  which — the  posterior — is  itself  reinforced 
by  a  left  sympathetic  filament  that  reaches  its  destination  in  passing  along  the 
recurrent  nerve.  When  it  is  entirely  constituted,  the  first  nerve  creeps  on  the 
base  of  the  heart,  turns  round  the  arch  of  the  aorta,  and  mixes  its  terminal  fibres 
with  those  of  the  left  cardiac  nerves.  The  second  right  cardiac  nerve  is  formed 
by  the  union  of  tkree  branches  that  arise  successively  from  the  corresponding 
pneumogastric,  behind  the  dorsal  artery,  along  the  right  side  of  the  trachea. 
This  nerve  attaches  itself  to  the  sympathetic  in  the  dorsal  region,  by  three 
branches  that  approach  the  latter  below  the  first,  fourth,  and  sixth  ribs. 

When  the  second  right  nerve  arrives  above  the  termination  of  the  anterior 
vena  cava,  it  divides  into  two  branches  ;  one  of  tnese  goes  to  the  roof  of  the 
auricles,  and  the  other — joined  by  a  filament  from  the  pneumogastric — is 
expended  by  numerous  ramuscules,  on  the  surface  of  the  left  ventricle  ;  some 
even  extend  to  the  right  ventricle. 

The  four  secondary  filaments  are  echeloned  on  the  portion  of  the  pneumo- 
gastric included  between  the  entrance  to  the  thora'x  and  the  division  of  the 
bronchi,    These  filaments  go  to  the  large  vessels,  and  into  the  walls  of  the  heart.^ 

3.  Dorsal  Portion  of  the  Sympathetic. 

The  cord  represented  by  this  portion  of  the  sympathetic  chain  leaves  the 
inferior  cervical  ganglion,  and  extends  from  before  to  behind,  towards  the 
diaphragm,  passing  beneath  the  superior  extremities  of  the  ribs — or  rather,  below 
the  vertebro-costal  articulations,  against  which  it  is  maintained  by  the  pleura — 
and  crossing  the  intercostal  arteries.  It  is  continued  in  the  abdominal  cavity  by 
the  lumbar  portion,  after  passing  through  the  arch  in  the  superior  border  of  the 
diaphragm,  along  with  the  psoas  parvus. 

Along  its  course,  this  cord  exhibits,  at  each  intercostal  space,  a  small  fusiform 
ganglionic  enlargement — seventeen  in  all.  The  two  or  three  first  are  most 
frequently  absent ;  but  then  the  anterior  extremity  of  the  nerve  has  for  some 
extent  the  appearance  of  a  ribbon-shaped  ganglion,  which  seems  to  be  due  to  the 
elongation,  posteriorly,  of  the  inferior  grey  mass  of  the  cervical  portion. 

Afferent  Branches. — Furnished  by  the  inferior  branches  of  the  dorsal 
nerves,  these  ramuscules  number  from  one  to  three  for  each  ganglion.  In 
proceeding  from  the  intervertebral  foramina  to  the  sympathetic,  they  traverse  the 
superior  extremity  of  the  intercostal  space,  passing  sometimes  behind,  sometimes 
before,  the  arteries  of  that  name. 

Efferent  Branches. — A  very  few  delicate  branches  pass  to  the  pleurae ; 
those  which  demand  notice  are  the  great  and  lesser  splanchnic  nerves. 

•  To  sum  up — the  cardiac  nerves  contain  fibres  from  the  pneumogastrics.  The  rifjht 
pneumogastric  furnishes  a  greater  number  to  them  tkan  the  left.  Perhaps  to  this  circumstance 
is  due  the  predominance  of  the  right  vagus  in  the  phenomena  attending  arrest  of  the  heart's 
action  (Arloing  and  Tripier,  "  Contribution  a  la  Physiologie  des  Nerfs  Vagues,"  in  Archiv.  de 
Phyeiologie  Nor.  et  Path.     1872). 


892  THE  NERVES. 

a.  Great  splanchnk  nervps  (Fig.  480,  7). — This  commences  to  be  detached 
from  the  doreal  chain  towards  the  sixth  or  seventh  ganglion,  is  directed  backwards 
bj  the  external  side  of  that  chain,  receives  an  accessory  branch  from  each  of  the 
enlargements  it  passes  by,  except  the  last  two  or  three,  and  enters  the  abdominal 
cavity  through  the  arch  of  the  psoas  parvus,  where  it  usually  looks  like  a  small 
ganglionic  mass  ;  after  which,  it  is  inflected  inwards,  and  terminates  on  the 
side  of  the  aorta,  between  the  coeliac  and  mesenteric  trunks,  by  a  second  and 
enormously  developed  mass — the  solar  ganglion. 

The  two  solar.,  or  semilunar  ganglia,  as  they  have  also  been  designated,  and 
which  are  the  largest  in  the  body,  are  elongated  from  before  to  behind,  and 
flattened  above  and  below.  They  communicate  with  one  another  by  means  of 
a  wide  and  thick  greyish  cord,  which  encircles,  posteriorly,  the  trunk  of  the  great 
mesenteric  artery,  and  by  a  multitude  of  filaments  which  pass  from  the  left  to 
the  right,  in  front  of  that  vessel.  From  this  arrangement  results  a  single  plexus, 
situated  at  the  inferior  face  of  the  aorta,  between  the  origin  of  the  two  precited 
arterial  trunks. 

This  plexus,  named  the  solar  plexas,  receives  some  branches  from  the  superior 
oesophageal  cord  of  the  pneumogastric  nerve.  It  subdivides  on  its  periphery 
into  several  secondaiy  plexuses,  which  leave,  as  from  a  centre,  the  principal 
network  :  the  ramifications  of  this— very  large  and  numerous — proceed  to  the 
neighbouring  organs  in  accompanying  the  arterial  divisions,  around  which  we  see 
them  interlacing  and  anastomosing  in  a  very  complicated  manner.  It  is  for  this 
reason  that  there  have  been  described  separately:  1.  A  gastric  plexus,  going  to 
the  stomach,  on  the  parietes  of  which  its  branches  anastomose  with  those  of  the 
pneimiogastrics.  2.  A  hepatic  plexus,  for  the  liver,  duodenum,  pylorus,  and 
pancreas.  3.  A  splenic  plexus,  one  part  of  which  passes  to  the  spleen,  the  other 
to  the  stomach.  4.  An  anterior  mesenteric  plexus — the  most  considerable  of  all — 
is  distributed  to  the  same  organs  as  the  artery  of  that  name.  5.  A  renal  and  a 
supra-renal  plexus — double,  and  scarcely  distinct  from  each  other — send  their 
terminal  divisions  to  the  kidneys  and  supra-renal  capsules.  The  terminations  of 
the  filaments  of  these  plexuses  have  been  already  described  in  the  Splanchnology. 

It  is  necessary  to  add  to  this  rich  nervous  apparatus,  the  lumbo-aorfic  plextis, 
formed  by  the  large  and  numerous  branches  which  spring  from  the  solar  plexus 
behind  the  great  mesenteric  artery,  creep  along  the  sides  and  the  inferior  face  of 
the  aorta,  frequently  anastomose  with  each  other,  and  reunite  at  the  posterior 
mesenteric  plexus. 

h.  Lesser  splanchnic  nerve  (Fig.  480,  8). — This  branch  is  composed  of  two 
or  three  filaments  that  emanate  from  the  last  subdorsal  ganglia,  and  which, 
instead  of  joining  the  great  splanchnic  nerve  like  the  others,  with  which  they 
communicate  by  one  or  two  fine  divisions,  collect  in  a  short  thin  cord,  the  rami- 
fications of  which  pass  directly  into  the  solar  plexus,  or  are  confounded  with  the 
nerves  of  the  kidney  and  the  supra-renal  capsule. 

4.  Lumbar  Portion  of  the  Sympathetic. 
This  is  a  cord  similar  to  that  of  the  dorsal  portion,  and  provided  with  fusi- 
form ganglionic  enlargements  equal  in  number  to  the  pairs  of  lumbar  nerves. 
This  cord  is  applied  against  the  psoas  parvus,  near  the  common  inferior  vertebral 
ligament,  and  is  covered  on  the  left  by  the  aorta,  on  the  right  by  the  posterior 
vena  cava.  It  is  directly  continued  by  the  sacral  portion  of  the  sympathetic 
chain,  at  the  lumbo-sacral  articulation. 


THE  GREAT  SYMPATHETIC  NERVOUS  SYSTEM.  893 

Afferent  Branches. — Furnished  by  the  inferior  branches  of  the  lumbar 
nerves,  tliese  raujuscules  comport  themselves  exactly  like  those  of  the  dorsal  region. 

Efferent  Branches. — These  are  short  filaments,  analogous  to  those  which, 
by  their  union,  constitute  the  splanchnic  nerves.  Their  number  is  not  constant, 
and  is  generally  less  than  that  of  the  ganglia.  Two  or  three  join  the  lumbo- 
aortic  plexus  ;  the  others  reach  the  origin  of  the  small  mesenteric  artery,  anas- 
tomose around  it  with  the  posterior  extremities  of  the  branches  of  that  plexus, 
and  thus  form  another  single  network,  designated  the  posterior  mesenteric  plexus 
(Fig.  480,  18). 

This  plexus,  in  the  centre  of  which  is  a  more  or  less  voluminous  ganglion, 
sends  to  the  various  branches  of  the  small  mesenteric  artery  ramifications  for  the 
walls  of  the  small  colon  and  the  rectum. 

It  supplies  besides  :  1.  Two  or  three  large  branches  which  follow  the  posterior 
mesenteric  vein,  and  join  the  anterior  mesenteric  plexus,  after  throwing  some 
divisions  into  the  colic  mesentery  (Fig.  480,  19). 

2.  Satellite  branches  to  the  two  spermatic  arteries,  constituting  the  plexus  of 
that  name  (Fig.  480,  20). 

.3.  Two  or  three  long  divisions  (Fig.  480,  21)  which  enter  on  each  side  of 
the  pelvis,  by  passing  beneath  the  external  face  of  the  peritoneum,  and  reach 
the  lateral  plane  of  the  rectum,  where  they  meet  the  filaments  emanating 
directly  from  the  inferior  sacral  nerves.  From  the  anastomosis  of  these  divisions 
results  a  rich  nervous  network,  called  in  Man  the  hypogastric  plexus,  and  which 
we  have  designated  the  pelvic  plexus ;  this  network  supplies  all  the  organs  con- 
tained in  the  pelvic  cavity  (Fig.  480,  23). 

5.  Sacral  Portion  of  the  Sympathetic. 

A  continuation  of  the  lumbar  cord,  this  portion  of  the  sympathetic  chain  is 
situated  beneath  the  sacrum,  to  the  inner  side  of  the  inferior  sacral  nerves.  It 
offers  four  very  elongated  ganglia,  which  communicate  with  these  nerves  by  one 
or  more  filaments,  and  which  give  rise  to  several  very  fine  ramuscules  that  are 
lost  in  the  connective  tissue  on  the  inferior  face  of  the  sacrum. 

Its  posterior  extremity,  which  terminates  behind  the  great  sympathetic,  does 
not  always  comport  itself  in  the  same  manner.  We  sometimes  see  it  become 
attenuated  to  a  very  delicate  ramuscule,  which  passes  on  to  the  mesian  coccygeal 
artery,  and  anastomoses  with  that  of  the  opposite  side.  But  sometimes,  also, 
this  ramuscule  cannot  be  distinguished,  and  the  sub-sacral  cord  seems  to  be 
abruptly  terminated  by  the  filament  of  communication  from  the  last  sacral  pair. 

Functions. — The  functions  of  the  sympathetic  are  as  yet  incompletely 
known,  notwithstanding  the  labours  of  many  physiologists,  at  whose  head  must 
be  placed  Claude  Bernard.  In  a  physiological  condition,  this  nerve  possesses 
an  extremely  obscure  sensibility,  but  which  may,  nevertheless,  become  very  acute 
in  pathological  states.  It  conveys  to  organs  the  unconscious,  motor  excitations 
originating  in  the  spinal  cord  or  its  ganglia  ;  and  through  the  filaments  it 
furnishes  to  the  vessels — the  vaso-motor  nerves — it  holds  under  its  control  the 
circulatoiy  phenomena,  especially  in  the  capillary  plexuses,  causing  these  canals 
to  suddenly  dilate  or  contract,  and  thus  diminish  or  accelerate  the  flow  of  blood 
in  them.  By  this  action  on  the  blood-vessels,  it  may  have  a  secondaiy  influence 
on  the  nutrition  of  the  organs  to  which  these  vessels  are  distributed.^ 

'  Francois  Franck  has  published,  in  the  Travaux  du  lahoratoire  de  M.  Marey,  pour  VAnn€e 
1875,  a  long  memoir  on  the  "  Nerfs  Vasculaires  de  la  tete."     The  author  passes  in  review  the 
59 


894  THE  NERVES. 

Differential  Characters  in  the  Great  Sympathetic  of  the  other  Animals. 

In  all  the  domesticated  Mammals,  the  general  disposition  of  the  great  sympathetic  is  very 
similar ;  so  that  there  are  but  few  and  slight  differences  to  note. 

In  the  Ox,  the  cervical  filament  of  the  sympathetic  does  not  arise  from  the  lower  extremity 
of  the  superior  ganglion,  but  behind,  from  its  middle  portion ;  it  is  divisible  into  two  or  three 
filaments  for  a  certain  distance,  after  which  it  lies  beside  the  pneumogastrio.  The  ramuscule 
that  leaves  the  lower  end  of  the  cervical  ganglion  is  very  large,  and  reaches  the  division  of  the 
common  carotid ;  that  which  accompanies  the  iuternal  carotid  artery  is  also  of  considerable 
size.     (Kuminants  have  13  thoracic  and  6  lumbar  ganglia.) 

In  tlie  Dog,  the  cervical  sym[)athetic  cord  is  closely  united  with  the  pneumogastric,  and 
it  is  not  possible  to  separate  them  from  each  other,  as  can  be  done  in  Solipeds  and  Kuminants. 
(In  the  Carnivora,  there  are  13  thoracic  and  7  lumbar  ganglia.) 

In  the  Rabbit,  there  are  two  cords  which  are  independent  along  the  whole  length  of  the 
neck. 

The  Pig  has  a  superior  cervical  ganglion,  which  is  fusiform  and  very  long ;  at  its  lower 
extremity  it  gives  oli"  several  filaments,  one  of  which  lies  beside  the  pneumogastric  in  the 
cervical  region,  but  separates  from  it  to  join  tlie  middle  cervical  ganglion  ;  the  others  pass  to 
the  tenth  nerve,  and  are  confounded  with  it  at  the  ganglionic  enlargement  it  shows  behind 
the  pharynx.  At  the  entrance  to  the  chest,  a  branch  separates  from  the  pneumogastric,  passes 
along  with  tlie  axillary  arteries,  and  finally  enters  the  lieart.  This  brancli  is  perhaps  formed 
by  the  filaments  of  the  sympathetic  that  joined  the  pneumogastric  at  the  upper  part  of  the 
neck.  (The  inferior  cervical  ganglion,  according  to  Leyh,  is  completely  isolated  from  the 
thoracic  ganglion.     The  Pig  has  14  thoracic  and  7  lumbar  ganglia.) 

In  the  other  domestic  animals  other  than  Solipeds,  the  number  of  ganglia  in  the  dorsal, 
lumbar,  and  sacral  portions  depends  upon  the  number  of  vertebrae  in  these  several  regions  in 
the  different  species.  In  them,  the  first  subdorsal  ganglion  is  more  voluminous  and  detached 
than  in  the  Horse. 

Comparison  of  the  Great  Sympathetic  in  Man  with  that  of  Animals. 

It  is  divided  and  disposed  as  in  animals.  The  cervical  portion  is  composed  of  a  superioi 
fusiform  ganglion,  from  which  emerge  many  branches  that  have  been  studied  with  the  greatest 
care.  Tliere  are  described:  1.  Superior  or  intercranial  branches.  2.  External  or  anastomosing 
branches  with  the  first  four  spinal  nerves.  3.  Internal  or  visceral  branches,  which  mix  witli 
the  pharyngeal  and  laryngeal  filaments  of  the  pneumogastric.  4.  Anterior  or  external 
carotideal  branches,  which  pass  to  the  common  carotid  and  the  middle  of  a  small  ganglion, 
the  intercarotid.  5.  Posterior,  muscular,  or  osseous  branches.  All  these  are  present  in  the 
Horse.  A  cervical  filament  and  two  inferior  ganglia— middle  and  inferior— complete  this 
region,  of  which  there  is  nothing  more  to  be  said. 

The  thoracic  portion  is  absolutely  identical  in  its  disposition  with  that  of  animals  ;  it  gives 
rise  to  a  great  splanchnic  nerve,  and  terminates  in  the  semilunar  ganglia. 

There  are  no  diflferences  to  note  in  the  lumbar  and  sacral  portims,  which  we  have  described 
as  the  pelvic. 


CHAPTEK  IV. 

THE   NERVOUS    SYSTEM   IN   BIRDS. 

Pkotective  Parts  of  the  Cerebro-spinal  Axis.— The  protective  parts  of 
tlie  nerve-centres  are  the  same  in  all  vertebrate  animals  ;  consequently,  there 

works  of  his  predecessors,  and  makes  known  the  new  results  he  has  obtained  in  associating 
anatomy  with  physiology,  summing  them  up  in  the  following  principal  conclusions:  1.  The 
vessels  receive  their  nerves  from  the  free  filaments  of  the  sympathetic,  and  trom  filaments  of 
the  same  kind  contained  in  the  mixed  spinal  nerves  obtained  by  the  latter  from  tlie  spinal  cord 
and  the  ganglia.  2.  The  superficial  and  deep  vessels  of  the  face  are  nmervated  by  the  free 
sympathetic  filaments  from  the  superior  cervical  ganglion  and  the  pre-vertebral  cord,  and  by  the 
branches  of  the  facial  and  the  trigeminus.  3.  The  vessels  of  the  ear  receive  their  nerves  from 
the  free  sympathetic,  the  facial,  and  the  trigeminus,  as  well  as  the  cervical  plexus.  4.  The 
encephalic  vessels  are  innervated  by  the  carotid  and  vertebral  plexuses. 


THE  NERVOUS  SYSTEM  IN  BIBD8.  895 

is  nothing  to  remark  regarding  those  of  Birds,  beyond  what  has  been  said  at 
p.  158.  The  envelopes  or  meninges  are  three  in  number,  and  disposed  as  in 
Mammals. 

''Thefalx  cerebri  is  found  in  Birds  ;  in  the  Turkey  it  has  the  form  of  the 
segment  of  a  circle,  and  extends  from  the  middle  of  the  interval  of  the  openings 
for  the  olfactory  nerves  to  the  tentorium  cerebelli.  The  falx  cerehelli  is  absent ; 
the  tentorium  is  small  and  sustained  by  a  bony  plate,  and  there  are,  in  addition, 
two  particular  folds,  one  on  each  side,  that  separate  the  hemispheres  from  the 
tubercula  quadrigemina  "  (Cuvier).    Owing  to  the  absence  of  the  falx  cerebelli, 


Fig.  481. 


A  B 

BRAIN   OF    A   BIRD.      A,  INFERIOR   FACE  ;     B,   SUPERIOR   FACE. 

HH,  Medulla  oblongata ;  Med,  spinal  cord ;  HE,  cerebellum ;  MH,  optic  lobe ;  VH,  cerebral 
hemisphere ;  L.ol,  olfactory  lobe ;  Hyp,  hyopophysis.  Tr.  opt,  optic  tract ;  /,  olfactory  nerves. 
The  cranial  nerves  are  indicated  by  the  corresponding  numerals. 


the  meninges  of  Birds  are  closer  together  than  those  of  Solipeds  or  Man. 
According  to  Leydig,  the  falx  cerebri  is  partially  ossified  in  birds. 

Spinal  Cord. — In  Birds,  the  spinal  cord  is  perforated  by  a  central  canal, 
and  also  offers,  as  in  Mammals,  two  enlargements — a  cervico-dorsal  and  lumbar. 
It  is  prolonged  into  the  coccygeal  vertebrae,  and  thus  furnishes  another  proof 
against  the  assertion  of  certain  naturalists,  who  desire  to  establish  a  relation 
between  the  length  of  the  spinal  cord  posteriorly,  and  the  development  of  the 
coccygeal  region.  The  two  fasciculi  of  the  medullary  axis  are  separated  from 
one  another  at  the  lumbar  enlargement,  and  afterwards  join  in  the  sacral  region. 
Between  them  is  an  elliptical  space — the  rhomboidal  sinus — which  is  filled  by 
transparent  gelatinous  connective  substance — a  kind  of  efflorescence  of  the 
ependymis  of  the  central  canal. 

Encephalox. — In  a  medium -sized  Fowl,  the  brain  weighs  about  2^  drams, 
and  comprises  the  three  portions  present  in  MammaHa. 


896  THE  NERVES. 

The  encephalic  isthmus  is  not  divided  into  two  sections  by  the  pons  Varolii, 
which  is  absent  in  birds  ;  the  crura  cerebelli  are  immediately  connected  with 
the  corpora  restiformia.  The  lower  face  of  the  isthmus  is  very  convex  posteriorly ; 
in  front,  the  tubercula  bigemina  are  united  to  each  other  by  a  comparatively 
large  transverse  cord,  formed  by  the  optic  nerves  intercrossing  in  the  median 
line.  The  superior  face  is  depressed  above  the  cerebellum,  so  as  to  constitute  a 
fourth  ventricle,  the  floor  of  which  is  also  shaped  like  the  point  of  a  pen  ;  in 
front  of  this  ventricle  are  the  tubercula  bigemina  {optic  lobes) — two  voluminous 
tubercules  separated  from  each  other  above,  where  they  embrace  the  cerebellum, 
and  salient  on  the  sides  of  the  lower  face.  They  are  hollow  internally,  and 
communicate  with  the  aqueduct  of  Sylvius.  The  thalami  optici  are  little  developed. 

The  cerebellum  is  almost  reduced  to  the  median  lobe,  the  lateral  lobes — situated 
behind  and  below  it — being  very  small  and  conical.  By  its  anterior  extremity, 
this  cerebral  ganglion  passes  between  the  corpora  bigemini,  and  touches  the 
cerebral  hemispheres.  The  cerebellum  is  annulated  transversely  to  its  surface, 
and  between  the  principal  fuiTows  are  secoj^dary  ones,  as  in  Mammals.  The 
white  substance  forms,  in  its  interior,  an  arborization  in  relation,  by  the  number 
of  its  branches,  with  the  simplicity  observed  on  the  surface  of  the  organ.  In 
the  centre  of  the  cerebellum  of  birds  is  a  small  cavity  communicating  with  the 
fourth  ventricle. 

The  cerebrum,  divided  into  two  hemispheres  by  a  shallow  fissure,  has  the 
shape  of  the  heart  on  a  playing-card,  more  particularly  when  viewed  on  its  lower 
face.  The  convolutions  are  absent  on  the  upper  and  lateral  faces  of  the  organ, 
and  on  the  inferior  is  a  vestige  of  the  fissure  of  Sylvius,  which  is  directed  obliquely 
forward  and  outward.  The  olfactory  lobes  are  little  developed,  and  are  placed 
together  in  the  mesian  line. 

The  two  ventricles  are  confounded,  there  being  no  corpus  callosum  nor 
septum  lucidum.  There  is  no  reflected  portion  in  the  ventricle  ;  consequently 
the  hippocampi  and  mastoid  lobules  are  absent ;  the  corpora  striata  are,  on  the 
contrary,  large,  and  occupy  nearly  the  whole  floor  of  the  ventricles. 

Cranial  Nerves. — These  are  twelve  pairs,  as  in  Mammals  ;  and  their  origin 
is  analogous,  if  not  identical ;  the  only  trifling  differences  observed  are  due  to 
the  absence  of  the  pons  VaroUi,  and  the  convexity  of  the  lower  face  of  the 
isthmus. 

Olfactory  nerve.— We  have  mentioned  above  how  this  is  formed  at  the  anterior 
portion  of  the  cerebral  hemispheres. 

Optic  nerve.— It  appears  to  be  detached  from  the  tubercula  bigemini,  and, 
after  a  very  short  course,  to  intercross  with  that  of  the  opposite  side.  In  certain 
Birds,  and  especially  in  the  diurnal  rapacious  kind,  the  optic  nerves  are  con- 
stituted by  fasciculi  of  undulating  nerve-tubes. 

Common  motores  oculonm.  Pathetici.  External  motores  oculor urn. -There  is 
nothing  particular  to  remark  respecting  these. 

Trifieminal  nerve.— Th\^  nerve  divides  into  three  principal  branches,  as  in 
the  domesticated  animals.  The  op)hthahnic  branch  has  a  nasal  ramuscule  that 
becomes  superficial,  and  extends  to  the  extremity  of  the  beak,  as  well  as  a  third 
filament  that  is  lost  around  the  inferior  orifice  of  the  nasal  cavities. 

The  superior  maxillary  issues  from  the  cranium  by  the  opening  through  which 
the  lower  maxillary  nerve  passes,  creeps  below  the  orbit,  traverses  the  maxillary 
bone,  and  terminates  on  the  sides  of  the  beak  by  filaments  that  resemble  the 
infra-orbital  ramuscules  of  the  Horse. 


THE  NERVOUS  SYSTEM  IN  BIRDS.  897 

The  inferior  maxillary  furnishes  two  bi*anches  :  one  passes  through  the  dental 
canal,  and  arrives  at  the  extremity  of  the  Lower  mandible  ;  the  other  is  spread  in 
the  subcorneus  integuments  of  the  same. 

Facial  nerve. — This  is  small  in  Birds.  "  It  is  distributed  to  the  muscles 
of  the  jaws  and  the  small  muscles  which  erect  the  feathers  of  the  crest" 
(Cuvier). 

Glosso-pharyngeal  nerve. — This  calls  for  no  remark. 

Pneumogastric  nerve. — There  are  few  differences  observed  in  this ;  it  is  as 
extensive  as  in  Mammals,  and  its  anastomoses  and  relations  are  nearly  the  same. 
It  is  not  entirely  formed  at  its  exit  from  the  cranium,  and  always  offers  two  or 
three  constituent  filaments  that  join  it,  and  are  confounded  at  some  distance 
from  the  point  of  emergence.     The  recurrents  furnish  ramuscules  to  the  crop. 

Spinal  accessory  nerve. — This  likewise  has  a  medullary  root  that  appears  at 
the  third  cervical  vertebra ;  it  runs  along  with  the  vagus  nerve  to  become 
superficial. 

Hypoglossal  nerve. — The  same  origin  as  in  Quadrupeds.  Where  it  crosses  the 
pneumogastric,  it  detaches  a  long  filament  that  passes  along  with  the  jugular 
vein  towards  the  chest.  On  the  sides  of  the  larynx  it  bifurcates ;  one  branch 
proceeds  forward  beneath  the  tongue,  the  other  follows  in  the  same  direction,  but 
on  the  upper  surface  of  that  organ. 

Spinal  Nekves. — We  need  only  notice  the  nerves  of  the  wing  and  pelvic 
limb,  the  others  being  disposed  in  a  similar  manner  to  those  above  described. 

Brachial  plexus. — Three  principal  branches — the  last  cervical  and  first  two 
dorsal — form  this  plexus  in  Palmipeds ;  in  the  Gallinaceae  there  are  four — 
the  last  three  cervical  and  first  dorsal.  These  branches  anastomose  beneath  the 
deep  face  of  the  scapulo-humeral  articulation.  When  fully  constituted,  the 
plexus  gives  off  some  collateral  ramuscules,  and  terminates  by  two  fasciculi  of 
branches.  The  first  collateral  goes  to  the  deep  pectoral  muscle  ;  another  is  dis- 
tributed to  the  muscles  surrounding  the  head  of  the  humerus,  as  well  as  to  the 
articular  capsule.  The  fascicuh  of  terminal  branches  may  be  distinguished, 
after  their  situation,  as  anterior  and  posterior.  The  latter  represents  the  internal 
brachial,  cutaneous,  and  radial  nerves ;  it  gives  off  muscular  and  cutaneous  ramus- 
cules that  extend  to  the  digits  at  the  extremity  of  the  wing.  The  anterior 
fasciculus  is  larger,  and  is  also  extended  to  the  whole  of  the  limb,  being  expended 
in  motor  and  sensitive  filaments  ;  near  its  origin  it  furnishes  ramuscules  to  the 
superficial  pectoral  muscle.  This  fasciculus  represents  the  median,  ulnar,  and 
anterior  brachial,  or  musculo-cutaneous  of  Mammals. 

Lumbo-sacrcd  plexus. — Two  lumbar  and  four  sacral  nerves  constitute  this 
plexus.  In  the  Fowl  it  is  distinctly  divisible  into  two  portions,  an  anterior  and 
posterior,  considerably  wide  apart. 

The  anterior  portion  is  composed  of  the  lumbar  branches  and  a  portion  of  the 
first  sacral ;  their  fusion  takes  place  on  the  salient  bony  ridge  that  separates  the 
lumbar  from  the  sacral  regions.  It  gives  origin  to  four  or  five  branches,  among 
which  are  clearly  discernible  :  1.  A.  filament  to  the  tensor  fascia  lata  muscle.  2. 
A  crural  or  femoral  nerve.  3.  An  internal  saphenic  nerve  that  descends  to  the 
leg.  4.  An  obturator  nerve.  The  latter  is  very  slender,  and  directed  down- 
wards and  backwards,  passing  into  the  muscle  that  closes  the  obturator 
foramen. 

The  posterior  portion  comprises  a  portion  of  the  first  sacral,  and  the  whole  of 
the  three  succeeding  nerves.     These  are  directed  outwards,  towards  the  sciatic 


898  THE  NERVOUS  SYSTEM  IN  BIRDS. 

notch,  where  they  unite  ;  during  their  course  in  the  interior  of  the  pelvis,  they 
are  surrounded  by  the  tissue  of  the  kidney.  The  distribution  of  this  portion  of 
the  plexus  resembles  that  of  the  Horse.  Thus,  in  leaving  the  great  sciatic  notch, 
it  gives  off  the  anterior  and  posterior  gluteal  nerves,  then  two  long  branches  that 
lie  together  as  far  as  the  gemelli.  These  branches  are  :  1.  The  great  sciatic,  with 
a  ramuscule  for  the  gemelli  and  the  posterior  tibial  muscles.  2.  The  external 
popliteal,  which,  outside  the  superior  extremity  of  the  leg,  divides  into  the  musculo' 
cutaneous  and  anterior  tibial  nerve. 


BOOK  VII. 

THE    SENSORY   APPARATUSES. 

Among  the  nerves  described  in  the  preceding  book,  those  which  have  been 
designated  sensory  nerves  have  for  their  principal,  or  even  exclusive  function,  the 
transmission  to  the  brain  of  the  impressions  derived  from  the  surrounding 
physical  world.  These  nerves  are,  therefore,  the  essential  instruments  of  sensa- 
tion, and  the  organs  to  which  they  are  distributed  constitute  the  sensory 
apparatuses.  These  are  admirably  disposed  for  the  reception  of  the  cerebral 
•stimuli,  and  are  five  in  number— the  apparatuses  of  touch,  taste,  smell,  vision,  and 
hearing.    The  principal  characteristics  of  these  will  be  briefly  enumerated. 


CHAPTER  I. 
APPARATUS  OP  TOUCH. 


The  sense  of  touch  is  destined  for  the  appreciation  of  tactile  sensations,  and, 
incidentally,  those  resulting  from  variations  of  temperature.  The  apparatus 
which  ministers  to  it,  is  formed  by  the  peripheral  radicles  of  the  nerves  of  general 
sensibility  distributed  in  the  skin — the  resisting  membrane  closely  investing  the 

entire  body,  and  continuous,  at  the  margin  of  the  natural  openings,  with  the 
mucous  or  internal  membrane. 

The  entire  skin,  therefore,  represents  the  organ  of  touch  ;  but,  as  in  Man, 

this  membrane  has  certain  privileged  regions  which  are  more  active  than  others 

in  the  exercise  of  this  faculty — these  are  the  limbs  and  the  lips. 

The  structure  of  the  skin,  though  pertaining  to  general  anatomy,  will  be 

•studied  here  somewhat  in  detail,  and  then  the  arrangement  of  its  appendages— 

the  hair  and  horny  productions — will  be  examined. 

Article  I. — The  Skin. 

Preparation. — See  treatises  on  histology. 

The  skin,  properly  speaking,  is  composed  of  two  layers  :  the  derma  and 
epidermis. 

The  Derma. — The  derma  or  coriiim  (corium  cutis,  cutis  vera),  forms  nearly 
the  entire  thickness  of  the  membrane.  Its  inner  face  (stratum  subcutaneum) 
adheres  more  or  less  closely  to  the  subjacent  parts,  through  the  medium  of  a 
cellulo-adipose  expansion  {panniculus  adiposus).  Its  external  face,  covered  by 
the  epidermis,  is  perforated  by  openings  through  which  the  hairs  pass,  or  through 
which  the  secretion  of  the  sudoriparous  and  sebaceous  glands  is  thrown  out  upon 


900 


THE  SENSORY  APPARATUSES. 


the  surface  of  the  skin  ;  this  external  face  also  shows  a  multitude  of  little  eleva- 
tions termed  papilJce,  in  which  the  majority  of  the  nerves  terminate. 

The  derma  is  not  of  the  same  thickness  everywhere,  being  much  thinner 
where  it  is  protected  from  external  injury — as  on  the  under-surface  of  the  belly, 
the  inner  side  of  the  legs,  thighs,  etc. ;  it  is  also  thin  around  the  margin  of  the 


SECTION   OF    horse's   SKIN    (FROM    WING   OP   THE    NOSTRIL). 

E,  Epidermis ;  D,  derma.  1,  Horny  layer  of  the  epidermis ;  2,  stratum  mucosum  ;  3,  papillary  layei 
of  the  derma ;  4,  excretory  duct  of  a  sudoriparous  gland ;  5,  glomerule  of  a  sudoriparous  gland  ; 
6,  hair-follicle ;  7,  sebaceous  gland ;  8,  internal  sheath  of  the  hair-follicle ;  9,  bulb  of  the  hair ; 
10,  mass  ot  adipose  tissue. 


natural  openings,  to  permit  the  transition  between  the  two  membranes,  and 
to  endow  these  apertm-es  with  theu-  necessary  dilatability. 

Structure. — The  derma  is  composed  of  fasciculi  of  connective  tissue  inter- 
woven and  matted  in  a  solid  manner,  and  in  the  meshes  of  which  are  some 
smooth  muscular  fibres,  which,  by  their  contraction,  produce  the  condition  of 
the  skin  known  as  the  cutis  anserina  (goose-skin).     Somewhat  loosely  woven  in 
its  deepest  part  to  form  the  reticular  layer  {stratum 
Fig-  -193.  reticulare),  the  derma  contains  the  roots  of  the  hair- 

follicles,  the  sudoriparous  (or  sweat)  glands,  and 
small  masses  of  adipose  tissue ;  superior,  its 
structure  is  very  condensed,  to  constitute  the  papil- 
lary  layer  {stratum  papilJare),  the  superficial  Umit 
of  which  forms  an  amorphous  layer  {basal  membrane). 
The  papilke  are  of  two  kinds — vascular  and 
nervous,  and  are  regularly  arranged  in  parallel  series. 
They  are  most  numerous  in  those  parts  of  the  skin 
especially  destined  for  the  exercise  of  touch— as  at 
the  lips,  in  the  keratogenous  membrane  (of  the 
foot),  and  other  parts  where  sensibility  is  very  acute — such  as  the  scrotum,  sheath, 
and  integuments  of  the  penis.  The  papillary  prolongations  of  the  derma  are 
conical  or  fungiform,  and  pediculated  ;  their  dimensions  are  very  variable ; 
measuring  from  -j--^  to  -^  of  an  inch  in  length,  and  from  y-^  to  ^^  of  an  inch 


CAPILLARY   LOOPS   IN   THE   CUTA- 
NEOUS   PAPILLA   OF   THE   UPS. 


TBE  APPENDAGES  OF  THE  SKTN. 


901 


in  width  at  their  base.     The  nerve-papillse  are  the  organs  of  touch,  and  con- 
tain either  the  corpuscula  tactus  (or  axile  bodies)  of  Meissner  or  those  of  Kraiise. 

The  sebaceous  glands  He  beside  the  hair-follicles,  each  hair  being  flanked  by 
two  glands.  These  small  organs  are  composed  of  a  very  granular  epithelium, 
and   are   usually   oval   in  shape. 

(They  are  embedded  in  the  upper  j^  ^*S-  *84.  ^ 

stratum  of  the  derma,  and  present 
every  degree  of  complexity — from 
the  simplest  follicle  to  the  com- 
pound lobulated  gland.  In  some 
situations,  their  excretory  ducts 
open  independently  on  the  surface 
of  the  epidermis.  Those  asso- 
ciated with  the  hairs  are  raceiform 
and  lobulated,  consisting  of  glan- 
dular vesicles,  which  open  by  short 
pedunculated  tubuli  into  a  common 
excretory  duct,  and  the  latter, 
after  a  short  course,  into  the  hair- 
follicle.  In  some  parts  the  ducts 
are  short  and  straight  ;  in  others, 
where  the  skin  is  thick,  they  are 
spiral.  They  are  lined  by  an  in- 
version of  the  epidermis,  which 
forms  a  thick  and  funnel-shaped 

cone  at  its  commencement,  but  soon  becomes  soft  and  uniform.  Sebaceous  glands 
are  met  with  in  all  parts  of  the  body,  but  are  most  abundant  in  those  parts  which 
are  naturally  exposed  to  the  influence  of  friction,  or  require  to  be  supple.  The 
sebaceous  glands  of  large  hairs  are  appendages  of  the  follicles  ;  but  where  there 
are  soft  woolly  hairs,  they  are  rather  appendages  of 
the  glands.  The  secretion — sebum — is  a  fatty 
matter  mixed  with  the  debris  of  broken-down  cells. 
The  glands  are  very  large  and  numerous  in  the 
sheath — preputium  penis,  where  they  are  designated 
Tyson's  glands.  Miiller  found  in  the  Pig  a  special 
cutaneous  gland,  somewhat  resembling  the  sebaceous 
glands.  It  is  situated  on  the  inner  and  posterior 
aspect  of  the  knee,  and  is  from  |  to  ?  inches  in 


TACTILE   PAPILLA   FROM   THE   SKIN,  SHOWING   THE 

tactile  corpuscles,  OR  "  axile  bodies." 
A,  In  the  natural  state ;  B,  treated  with  acetic  acid. 


Fig.  485. 


length,  and  from 


to 


inch  in  width.     In  the 


Sheep,  there  is  found,  in  the  skin  between  the  claws, 
a  particular  inversion  of  the  integument  that  f  onus 
a   small   elongated  pouch,  curving  upwards,  and 
terminating  in   a   cul-de-sac.      This  is  the  inter- 
digitalpouch,  interungulate  gland,  sinus,  or  biflex  canal 
— sinus  cutaneus  unguJarum ,-  it  secretes  a  viscid 
matter  from  glands  which,  according  to  Ercolani, 
are  analogous  to  the  sebaceous  glands.     The  pouch  is  lined  with  very  fine  hairs, 
and  often  contains  foreign  substances,  such  as  sand  ;  it  sometimes  becomes  in- 
flamed and  its  orifice  occluded,  when  it  is  transformed  into  a  retention  cyst.) 
The  sudoriparous  glands  are  deeper  situated  than  the  last  (passing  even  into 


INTERUNGULATE   SINUS  OF  SHEEP. 


Inner  aspect  of  first  phalanx  ;  b, 
hoof,  or  claw;  c,  interungulate 
gland  ;  d,  ori6ce  of  its  duct. 


902 


THE  SENSOBY  APPARATUSES. 


the  subcutaneous  connective  tissue,  where  they  are  surrounded  by  adipose  cells). 
They  consist  of  a  convoluted  tube  (or  several  tubuli  produced  by  dichotomous 
subdivision)  embedded  in  the  reticular  layer  of  the  derma,  and  form  an  elliptical 
glomerule,  generally  lying  obliquely  to  the  surface  of  the  skin  in  the  Horse.    The 


Fig.  486. 


Fig.  487. 
d 


VERTICAL  SKCTION  OF  THE  SKIN  TREATED  WITH 
A   SOLUTION   OF    CAUSTIC   SODA,   showing    the 

branches  of  cutaneous  nerves,  a,  b,  inosculate 
incr  to  form  a  terminal  plexus,  of  which  the 
ultimate  ramifications  pass  into  the  papillae, 


excretory  canal  is  a  continuation  of  this  glomerule, 
and  passes  through  the  derma  and  epidermis  in  a 
spiral  manner.  (The  tube  is  lined  with  a  single 
layer  of  cubical  cells  containing  pigment  and 
fat-granules,  while  its  wall  is  formed  of  a  delicate 
ynembrana propria.  In  large  glands,  smooth  muscu- 
lar fibres  are  found  between  the  memhrane  propria 
and  the  gland  cells.) 

The  blood-vessels  form  a  very  rich  network  in 
the  papillary  layer  of  the  derma,  and  also  surround 
the  sebaceous  and  sudoriparous  glands.  The  li/m- 
phatirs  are  disposed  like  the  capillaries. 

(The  arteries  arise  from  vessels  in  the  underlying 
fasciae,  and  pass  vertically  towards  the  surface, 
forming  three  sets  of  capillaries — the  deepest  to  the 
adipose  tissue,  the  next  run  round  the  sweat-glands, 
the  last — the  terminals — form  a  net-work  in  the 
stratum  papiUare,  which  sends  loops  into  the  papillae 
and  small  twigs  into  the  hair-follicles  and  sebaceous 
glands.  The  veins  arise  in  the  stratum  papillare 
from  the  loops  in  the  papillse,  and  from  the  follicles 
and  sebaceous  glands. 

The  lymphatics  form  two  capillary  networks 
— one  of  fine  vessels  forming  narrow  meshes  in 
the  stratum  papillare,   below  the    blood-capillary 

network  ;    and   one   with   wider  meshes,   in   the  subcutaneous   tissue.     Minute 
lymphatics  are  also  found  outside  the  hair-follicles  and  the  two  sets  of  glands.) 

The  nerves  are  aiTanged  in  two  layers  :  one  loosely  distributed  in  the  derma ; 


SUDORIPAROUS  GLAND  (MAGNIFIED 

40  diameters). 

a,  a,  Contorted  tubes  composing 
the  gland,  and  uniting  in  two^ 
excretory  ducts,  6,  6,  which  join 
into  one  sjiiral  canal  that  per- 
forates the  epidermis  at  c.  and 
opens  on  its  surface  at  d;  the 
gland  is  embedded  in  fat  vesi- 
cles, e,  e. 


TEE  APPENDAGES   OF  TEE  SKIN.  903 

the  other  very  close,  and  lodged  in  the  papillary  layer,  which  is  traversed  by 
recurrent  fibres  giving  off  tubes  that  pass  into  the  nerve-corpuscles  of  the  papillae. 

The  superficial  network  detaches  the  terminal  fibres  that  pass  into  these 
papillge  or  into  the  stratum  mucosum  of  the  epidermis.  The  intra-epidermic 
nerve  terminations  have  been  particularly  observed  in  the  snout  of  the  Pig. 

Epidermis. — The  epidermis  is  a  thin  pellicle,  covering  the  superficial  face  of 
the  derma  ;  it  is  destitute  of  blood-vessels,  and  is  formed  of  cells  which  are  being 
continually  deposited  on  the  derma  ;  these  cells  become  flattened  in  layers  as  they 
are  pushed  up  from  the  latter,  and  are  destroyed  by  friction  on  the  surface  of  the 
skin.  The  deep  face  of  the  epidermis  is  moulded  on  the  upper  surface  of  the 
derma  ;  consequently,  it  lodges  the  papillae,  and  dips  into  the  follicles  and  ex- 
cretory ducts  of  the  glands  of  the  skin  ;  its  external  face  is  not  a  very  exact 
repetition  of  the  surface  of  the  derma,  and  is  covered  with  hair.  The  epidermis 
tends  to  equalize,  and  to  fill  up,  the  depressions  existing  between  the  papillse. 

Structure. — The  epidermis  comprises  two  layers,  which  are  not  very  distinct 
from  each  other  in  the  Horse.    The  deep  layer,  or  rete  Malpighi  {stratum  mucosum), 
is  composed  of  soft,  nucleated,  pigmented,  denticulated 
cells,  which  are  sometimes  attached  by  their  fine  pro-  ^'s-  '*^^- 

longations  {prickle-cells)    to    other   ceils    more  or   less 
distant ;  there  are  spaces  between  them  filled  with  an       ^^ 
amorphous  semifluid  substance.     The  superficicd  or  horny 
layer  {stratum  corneum),  is  constituted  by  hard,  horny, 
flattened  cells,  which  still  contain  some  pigment-granules,  -^^^^^ 

and  are  insensibly  confounded  with  those  of  the  rete        ^^^t-S-^. 
mucosum.  ^  "^  ^  ""^-S 

(Where  the  epidermis  is  thick,  there  is  seen  between       ^.j'^ 9 n%j^--p 
the   two   layers   just  mentioned,   a   third — the  stratum         ^  <3>  ^  g,;  'C®#-<* 
lucidum — the  nature  of  which  has  not  yet  been  defined.        p^g^j©^^' 
It  is  transparent,  and  apparently  amorphous.     The  theory         "^^^S:,:^^^^^ 
of  growth  of  the  epidermis  is  believed  to  be  as  follows  :    o^^ic^^j^  section  of  epi- 

5  1  ,      •         1  J-  o  DERMIS,     SHOWING    THE 

a  layer  of  plastic  lymph  is  thrown  out  on  the  surface  ot  progressive  develop- 

the  derma,  and  is  converted  into  granules,  which  are  ment  of   its   compo- 

termed   cell-germs,  or  cytoblasts.      These  imbibe  serum  ^^'^^  cells. 

from  the  lymph  and  adjacent  tissues,  so  that  the  outer-  «'  ^",tl  ^flKra,') • 

most  covering  of  the  cytoblast  is  gradually  distended ;  these  nuclei  are  giadu- 

the  latter  becomes  a  cell,  and  its  solid  portion,  which  ally  developed  into  cells 

.  /•  .       .  at  0,  c,  and  a,  and  the 

always  remains  adherent  to  some  point  of  the  inner  sur-        cells  are  flattened  into 
face  of  the  cell  membrane,  forms  the  nucleus  of  the  cell.        lamellae,    forming    the 
Within  this  nucleus  one  or  more  nuclei  are  developed  ;        epiderm^i^l  e^^ 
these  are   named  nucleoli.      The   process  of   imbibition 

continuing,  the  cell  becomes  more  or  less  spherical ;  so  that,  after  a  certain  time, 
the  papillary  layer  of  the  demia  is  covered  by  a  thin  stratum  of  spherical  cells 
pressed  closely  together,  and  corresponding  with  every  irregularity  of  the  papillae. 
New  cells  being  continually  produced  before  the  formation  of  the  others  has 
been  quite  completed,  these  are  removed  in  layers  further  and  further  from  the 
surface  of  the  derma,  and,  becoming  subjected  to  the  influence  of  physical  laws, 
their  fluid  contents  evaporate  ;  they  collapse,  flatten,  and  gradually  assume  an 
elliptical  shape  ;  then  they  are  a  mass  of  completely  flat  cells,  with  an  included 
nucleolated  nucleus,  and  finally  become  a  thin  membranous  scale,  in  which  the 
nucleus  is  scarcely  apparent.) 


904  THE  SENSORY  APPARATUSES. 

In  Solipeds  and  other  animals,  the  epidermis  is  generally  dark-coloured,  from 
the  presence  of  pigment-corpuscles,  the  number  of  which  increases  with  their 
depth  in  the  membrane.  This  coloration  is  perhaps  intended  to  prevent  the 
rubefacient  effects  of  the  heat  of  the  sun's  rays,  by  augmenting  the  absorbing 
and  dispersing  power  of  the  cutaneous  surface.  In  the  majority  of  cases,  this 
coloration  is  absent  in  the  Sheep,  whose  skin  is  protected  by  a  thick  fleece  ;  and 
also  in  tlie  Pig,  whose  habits  in  a  wild,  as  in  a  domesticated  condition,  keep  it 
out  of  the  direct  action  of  the  sun. 

(In  some  regions  of  the  body  of  all  animals,  the  skin  forms  folds,  as  at  the 
junction  of  the  fore  limb  with  the  body,  the  flank,  and  between  the  thighs.  In 
the  Cow,  it  forms  the  large  pendulous  layer  at  the  throat  and  breast,  known  as 
the  "  dewlap  ; "  and  in  the  Goat  and  Pig,  it  not  unf requently  constitutes  teat- 
like prolongations  depending  from  the  throat,  which  nearly  always  contain  a 
small  cartilaginous  nucleuc  and  some  muscular  fasciculi.  The  thickness  of  the 
epidermis  is  sometimes  greatly  increased  by  wear  and  friction,  as  we  frequently 
see  in  the  skin  covering  the  knees  of  Sheep,  etc.) 

(The  functions  of  the  skin  are,  as  we  have  seen,  tactile  and  secretory ;  m 
addition,  it  is  eminently  protective.  Its  secretory  action  is  always  more  or  less 
active,  but  the  production  of  perspiration  is  greatest  when  the  body  is  at  a  high 
temperature,  as  during  active  exertion  ;  at  other  times  the  perspiration  is 
insensible.  In  this  respect,  the  skin  has  intimate  sympathetic  relations  with 
other  organs  which  have  somewhat  analogous  functions,  such  as  the  lungs, 
kidneys,  intestines,  etc.,  and  when  its  function  is  disordered  or  checked,  it 
induces  alterations  in  the  secretions  of  one  or  all  of  these  organs.  The  skin  is 
also  the  seat  of  a  constant  and  important  respiratory  action,  as  it  absorbs  oxygen 
and  throws  off  carbonic  acid,  and  any  interruption  to  this  process  is  injurious.) 

The  skill  of  Ruminants  shows,  at  certain  points,  depressions  destitute  of  hair,  but  extremely 
rich  in  sebaceous  glands.  Such  is  the  tear  fossa  situated  on  the  face,  and  tl  biflex  canal 
between  the  digits— as  in  the  Sheep,  and  particularly  in  the  Goat.  (It  should  be  remarked 
that  sioeat-glanih  are  found  in  the  skin  of  the  Ox,  and  in  tl. ;  pads  of  the  feet  of  Dogs  and  Cats. 
They  attain  a  great  size  in  the  pig's  snout.  The  nos;  and  upper  lip  of  Ruminants,  and  that  of 
the  Dog  an<i  Cat,  contain  racemose  glands  that  secrete  :  clear,  watery,  alkaline  fluid.) 

Article  II.— Appendages  of  the  Skin. 

Preparation. — See  treatises  on  histology. 

The  appendages  of  the  skin  are  hairs  and  horny  productions^  dependencies  of 
the  epidermic  layer. 

Hairs. 

The  hairs  are  the  filaments  which,  collectively,  form  the  external  covering  of 
the  skins  of  animals. 

In  the  Horse,  the  bristly  appendages  known  as  horsehair  should  be  dis- 
tinguished from  the  hairs  proper ;  the  latter  are  fine  and  short — particularly 
in  the  regions  where  the  skin  is  thin — imbricated  on  each  other,  and  spread 
over  the  entire  surface  of  the  body  in  c  continuous  layer  which  is  designated 
the  coat.  The  former  are  long  and  flowing,  occupy  the  summit  of  the  head, 
where  they  constitute  the  forelock ;  the  upper  border  of  the  neck,  where  they 
form  the  mane ;  and  cover  the  caudal  appendage  with  a  splendid  tuft — the  tail. 
Some  of  these  also  form  special  organs  on  the  free  margin  of  the  eyelids,  and 
are  termed  eyelashes  ;  while  others,  inserted  about  the  lips  and  below  the  eyes, 
are  named  tentacula.     (The  eyelashes  are  chiefly  implanted  in  the  upper  lid. 


TEE  APPENDAGES  OF  TEE  SKIN. 


905 


The  hairs  of  the  tail  are  the  longest  and  strongest  in  the  body.  These  par- 
ticular hairs  also  grow  on  the  posterior  aspect  of  the  limbs,  generally  from 
about  the  knees  and  hocks  to  the  hoofs  ;  at  the  sesamoid  bones  they  constitute 
a  long  tuft — the  fetlock — which  surrounds  the  horny  growth  named  the  "  ergot." 
These  "  foot-locks  "  are  peculiar  to  the  Horse,  and  vary  in  length  and  coarseness 
with  the  breed  of  the  animal.) 

"When  the  hair  is  fine,  long,  and  wavy,  it  f onus  ivool ,-  and  when  straight  and 
rigid,  as  in  the  Pig,  it  is  known  as  bristles. 

In  the  Ass  and  Mule,  the  forelock  and  mane  are  rudimentary  or  absent, 
and  the  hair  of  the  tail  is 
limited  to  a  small  tuft  at  the 
extremity  of  the  organ  in  the 
former  animal ;  while  in  the 
latter  it  is  much  less  abundant 
than  in  the  Horse. 

In  the  Ox,  these  hairs 
are  not  present,  except  at  the 
extremity  of  the  tail,  as  with 
the  Ass. 

There  are  no  other  animals 
which  have  other  hair  than 
that  composing  the  coat. 

(The  ordinary  hair  of  the 
coat  is  soft  and  elastic,  in- 
clined in  particular  directions, 
and  varies  in  length  not  only 
according  to  the  regions  of 
the  body  on  which  it  grows, 
but  also  according  to  the 
season  or  climate.  In  the 
Horse,  the  direction  of  the 
hair  of  the  coat  gives  rise  to 
curiously  fonned  waves,  lines, 
and  circles,  the  most  constant 
of  which  is  on  the  forehead. 

In  the  Cow,  the  hair  is 
frizzly  on  the  forehead  ;  on 
the  posterior  part  of  the  thighs 
it  has  a  particular  direction, 
while  on  the  outer  side  it  passes  downwards,  and  from  the  posterio"  part  of  the 
mammae  it  ascends  as  high  as  the  vulva ;  this  characteristic  disposition  forms 
what  the  French  have  termed  ecussois,  by  which  some  have  pretended  to  recognize 
the  lactiferous  qualities  of  the  animal. 

In  the  Sheep,  real  hair — not  wool — is  found  on  the  lower  part  of  the  face, 
and  the  extremities  of  the  limbs. 

In  the  Goat,  the  hairs  of  the  beard  are  veiy  long,  and  compose  a  distinc- 
tive tuft ;  this  animal  has  also  a  fine  crisp  duvet  or  dotvn  beneath  the  ordinary  hair. 

In  the  Pig,  the  bristles  are  very  strong  in  the  region  of  the  back  ;  in  old 
animals  they  are  usually  bi-  or  trifurcated  at  their  free  extremity  ;  there  also 
exists  a  fine  soft  hair  on  this  animal.     It  has  no  tentacular  hairs. 


HAIR-FOLLICLE. 


1,  External  dermic  layer  of  the  follicle ;  2,  internal  dermic 
layer;  3,  amorphous  lininr  of  the  follicle;  4,  external 
epidermic  layer ;  6,  hair-bulb ;  7,  vascular  papilla ;  8, 
cells  of  the  medullary  substance. 


906  THE  SENSORY  APPARATUSES. 

In  the  Dog,  the  length,  fineness,  and  consistency  of  the  hair  depends  on  the 
breed. 

In  the  Cat,  the  hair  in  some  breeds — as  in  the  Angora— is  remarkable  for 
its  length  and  softness.  This  creature  has  the  tentacula  enormously  developed 
as  a  moustache. 

In  "none  of  these  animals  is  there  a  "  foot-lock.") 

Steucture. — The  hairs  are  implanted  in  the  texture  of  the  derma,  and 
sometimes  even  in  the  subjacent  tissues,  their  base  being  enclosed  in  a  follicle, 
at  the  bottom  of  which  their  elements  are  developed.  It  is  therefore  necessary 
to  study  :  1.  The  structure  of  the  hair.     2.  Thaf.  of  the  hair-folHcle. 

1.  The  hair  presents  a  free  portion — the  shaft  (scapus),  and  another  con- 
cealed in  the  follicle — the  root  (radix  pili)  ;  the  latter  widens  at  its  base — the 
hulh  {bulbus  pili)  of  the  hair — to  embrace  the  papilla  or  hair-germ. 

There  are  three  superposed  layers  in  a  hair.  The  epidermis  (cuticle)  is  a  thin 
lamella  of  homy  flattened  cells,  imbricated  like  tiles  on  a  roof.  Its  elements 
are  marked  on  the  surface  of  the  hair  by  shaded  lines  anastomosing  to  form 
a  network ;  they  enlarge,  and  become  more  apparent  under  the  influence  of  an 
alkali.  The  epidermis  belongs  to  the  shaft  and  a  portion  of  the  root ;  near  the 
bulb  it  is  replaced  by  soft  nucleated  cells,  which  are  implanted  vertically. 

The  cortical  substance  (cortex)  forms  the  largest  part  of  the  thickness  of  the 
hair.  It  is  striped  longitudinally,  and  provided  with  pigment  granules,  the 
number  of  which  varies  with  the  colour  of  the  coat.  In  white  hairs  these 
granules  are  absent,  but  there  are  found  in  them,  as  well  as  in  coloured  hairs, 
small  spaces  containing  air,  and  which  exhibit  a  dark  colour  under  the  micro- 
scope. Treated  by  potassium  or  sulphuric  acid,  the  cortical  substance  is  reduced  to 
elongated  spindles,  which  again  may  be  decomposed  into  slender  epithelial 
lamellte  without  nuclei.  On  arriving  at  the  root,  the  cells  change  their  cha- 
racter, becoming  polyhedric,  filled  with  fluid,  and  exhibit  a  perfectly  distinct 
nucleus  and  more  or  less  pigment.  The  meduUary  substance  (mechdla)  occupies 
a  narrow  irregular  cavity  in  the  centre  of  the  hair,  extending  from  the  bulb 
or  termination  of  the  root,  to  the  point.  It  has  for  its  base  rectangular,  rarely 
circular,  cells,  which,  according  to  Kolliker,  contain  fat-granules  and  air- 
globules.  (Many  hairs  show  no  medulla,  and  even  in  thick  hairs  it  does  not 
always  extend  the  entire  length  of  the  hair.) 

2.  The  hair-follicle  is  a  narrow  cavity,  slightly  contracted  at  its  orifice  and 
dilated  at  the  bottom,  where  the  hair-papilla  is  placed.  It  is  a  simple  involution 
of  the  skin,  as  its  structure  demonstrates.     It  presents,  from  without  to  within  : 

1.  A  loose  conjunctival  layer,  analogous  to  the  reticular  layer  of  the  derma. 

2.  An  internal  dermic  layer,  dense  and  close  hke  the  papillary  layer  of  the  skin. 

3.  An  amorphous  limiting  membrane.  4.  An  epidermic  zone — the  external  sheath 
of  the  hair — formed  by  cells,  similar  to  those  of  the  stratum  mucosum.  5.  A 
second  epidermic  zone — the  interned  sheath  of  the  hair — which  repeats  the  horny 
layer  of  the  epidermis,  and  is  confounded  with  the  termination  of  the  epidermis 
of  the  hair  towards  the  lower  third  of  the  follicle. 

The  papilla,  or  hcdr-germ,  is  a  small,  conical,  vascular,  and  nervous  prolonga- 
tion rising  up  into  the  hair-bulb.  It  furnishes  the  hair  with  nutrition  and  the 
elements  of  growth. 

The  walls  of  the  follicles  of  the  enormous  hairs — or  tentacula — which  garnish 
the  lips  of  the  Horse,  or  bristle  from  those  of  the  Cat  (moustaches),  are  pro- 
vided with  nerve-ramifications  which   endow  these   appendages   with  a  high 


TEE  APPENDAGES  OF  THE  SKIN.  907 

degree  of  sensibility,  and  enable  them  to  play  an  important  part  as  organs 
of  touch. 

The  follicles  of  these  large  hairs  show,  between  the  second  and  third  layers  of 
their  wall,  a  vascular  dilatation — a  kind  of  erectile  tissue — that  probably  plays  a 
part  also  in  the  exercise  of  touch  (Leydig,  Odenins,  Paladino,  etc.). 

Two  sebaceous  glands,  and  a  smooth  muscular  fasciculus,  are  annexed  to  the 
pilous  follicle.  The  sebaceous  glands — which  have  been  already  described — 
open  into  the  sheath  of  the  hair  by  a  small  excretory  canal,  which  traverses 
the  fibrillar  walls  of  the  foUicle.  The  muscular  fasciculus  {musculus  arrector 
pill)  is  situated  on  the  side  to  which  the  hair  and  its  foUicle  are  inclined  ;  it 
arises  from  the  superficial  face  of  the  deima,  and  terminates  at  the  bottom  of 
the  foUicle,  which  it  erects  by  contracting.  When  the  fasciculi  contract  over  a 
wide  surface,  the  extent  of  the  skin  is  diminished,  and  the  hairs  are  erected  and 
partially  ejected  from  their  follicles — producing  the  cutis  anserina. 

(Next  to  the  innermost  layer  of  the  corium  of  the  hair  is  a  layer  of  stratified 
epithelium — the  external  root-sheath  ;  and  lining  this,  in  the  upper  part  of  the 
follicle,  is  the  internal  root-sheath,  representing  the  stratum  corneum.  This 
inner  root-sheath  divides,  near  the  orifices  of  the  sebaceous  glands,  into  two 
layers — Henle's  sheath  being  the  outer,  and  Huxley's  sheath  the  inner. 

The  formation  of  a  hair  is  identical  with  the  formation  of  the  epidermis 
by  the  papillary  layer  of  the  derma.  The  capillary  plexus  of  the  follicle  throws 
out  plastic  lymph  which  is  converted  into  granules,  then  into  cells,  which  become 
elongated  into  fibres.  The  cells  that  are  to  form  the  surface  of  the  hair,  are 
converted  into  flat  scales  that  enclose  the  fibrous  structure  of  the  interior.  As 
these  are  successively  produced,  they  overlap  those  previously  formed,  and  give 
rise  to  the  waving  lines  seen  on  the  circumference  of  the  hair  ;  this  overlapping 
also  causes  the  roughness  experienced  in  drawing  a  hair  between  the  fingers  from 
its  point  to  the  bulb.  The  latter  is  the  newly  formed  part  of  the  hair,  its 
expanded  form  being  due  to  the  greater  bulk  of  the  fresh  cells. 

The  colour  of  the  hair  is  very  varied  in  animals,  ranging  from  black  to 
white,  red  and  brown,  with  all  the  intervening  shades.  The  tint  also  changes 
at  different  periods  of  life,  being  sometimes  altogether  altered  between  the 
juvenile  and  adult  periods ;  dark-coloured  Horses  becoming  light-coloured  as 
age  advances.  Besides,  it  is  never  uniform  in  the  same  animal ;  black  Horses 
not  unfrequently  having  white  patches  and  diverse  tints,  with  other  dissimilari- 
ties. The  disease  termed  "  melanosis  "  is  very  common  in  old  white  Horses 
which  were  previously  grey,  and  is  supposed  to  be  due  to  the  localization  of  the 
black  pigment  at  certain  limited  points.  The  hair  grows  according  to  the 
climate,  seasons,  food,  etc.,  and  varies  with  the  species  and  breed.  The  coat  in 
every  animal  is  shed  at  certain  times,  and  is  replaced  by  new  hairs. 

The  hair  preserves  the  skin  from  unhealthy  external  influences — wet  and 
cold  for  example.  It  is  a  bad  conductor  of  heat,  and  therefore  keeps  the  body 
warm.  The  tentacula  are  very  useful  as  tactile  organs  ;  while  the  mane,  fore- 
lock, and  tail  keep  away  insects,  and  the  long  hairs  of  the  fetlock  and  pastern 
protect  these  parts  from  the  injurious  effects  of  cold  and  wet,  and  the  action  of 
foreign  bodies.) 

Homy  Productions. 

The  horny  tissues  form  several  groups.  The  first  comprises  the  horns  of 
Euminants  ;  the  second,  the  so-called  chestnuts  of  Solipeds  ;  the  third,  the  pro- 


THE  SENSORY  APPARATUSES. 


tective  layer  enveloping  the  digital  extremities,  and  constituting  the  claws  of 
Garni v'ora,  the  Pig,  Ox,  Sheep,  and  Goat,  and  the  hoofs  of  the  Horse,  Ass,  and 
Mule.  These  latter  productions,  ranking  as  they  do  among  the  most  important 
organs  of  the  locomotory  apparatus  of  Solipeds,  will  fii-st  receive  notice. 

1.  The  Hoof  of  Solipeds. 

The  hoof  of  Solipeds  is  an  extremely  important  study,  because  of  the 
numerous  diseases  which  affect  this  region.  Consequently,  it  has  been  the 
subject  of  several  voluminous  works,  to  which  the  student  must  be  referred 

for  a  more  complete  description  of 


Fig.  490. 


LONGITUDINAL   MEDIAN    SECTION    OF    THE    FOOT. 


1,  Anterior  extensor  of  the  phalanges,  or  extensor 
pedis;  2,  literal  extensor,  or  extensor  suffraginis; 

3,  capsule  of  metacarpo-phalangeal  articulation ; 

4,  large  metacarpal  bone  ;  5,  superficial  flexor  of 
the  phalanges,  or  perforatus ;  6,  deep  flexor,  or 
perforans ;  7,  sheath ;  8,  bursa ;  9,  sesamoid 
bone;  10,  ergot  and  fatty  cushion  of  fetlock;  11, 
crucial  ligament;  12,  short  sesamoid  ligament; 
13,  first  phalanx;  14,  bursa;  15,  second  pha- 
lanx ;  16,  navicular  bone  ;  17,  plantar  cushion  ; 
18,  third  phalanx;  19,  plantar  surface  of  hoof; 
20,  sensitive  or  keratogenous  membrane  of  tliird 
phalanx. 


its  organization  ;  ^  as  we  cannot  do 
more  here  than  give  some  essentially 
descriptive  details,  necessary  to  fill 
up  the  outline  that  we  have  traced 
out. 

We  will  at  firet  glance  at  the  parts 
contained  in  the  hoof,  returning  after- 
wards to  a  description  of  the  homy 
case  itself. 

a.  The  Pabts  contained  in  the 
Hoof. 

Proceeding  from  within  to  with- 
out, we  find,  in  the  interior  of  the 
horny  box  :  1.  The  third  phalanx, 
navicular  bone,  and  lower  part  of 
the  second  phalanx,  forming  the 
articulation  of  the  foot.  2.  The  four 
ligaments  that  bind  this  articulation. 
3.  The  tendon  of  the  common  ex- 
tensor of  the  phalanges  which  covers 
the  articulation  in  front,  and  that  of 
the  perforans  which  supports  it  be- 
hind, in  becoming  inserted  into '  the 
pedal  bone,  after  gliding  over  the 
posterior  surface  of  the  navicular 
bone.  4.  The  complementary  ap- 
paratus of   the   third   phalanx.      5. 


The  matrix  of  the  hoof,  or  kerato- 
genous membrane— a  continuation  of  the  derma  covering  the  digital  region.  To 
these  parts  must  be  added  the  vessels  and  nerves  of  thi»  region. 

The  description  of  the  bones  has  been  given  at  pp.  114,  150  ; 

Of  the  articulation  and  its  ligaments,  at  p.  209  ; 

Of  the  tendon  of  the  anterior  extensor  of  the  phalanges,  at  p.  325  ; 

Of  the  perforans  tendon,  at  p.  331  ; 

*  Pee  particularly,  among  the  French  works,  the  Traite  de  VOrgnnisation  du  Pied  du 
Cheval,  by  M.  H.  Bouley.  (See  nlso  the  still  more  recent  work  by  Leis<ring,  Der  Futz  det 
Pferdeg  Dresden  :  1870.  Also  a  long  series  of  papers  by  me  on  this  subject  in  the  Veteri- 
narian for  1871-2.^ 


TEE  APPENDAGES  OF  TEE  SKIN.  909 

Of  the  arteries,  at  pp.  636,  654  ; 
Of  the  veins,  at  pp.  698  to  703. 
Of  the  nerves,  at  pp.  865,  881. 

It  remains  to  notice  the  complementary  apparatus  of  the  third  phalanx,  and 
the  Tceratogenous  memhrane. 

Preparation. — The  dissection  of  the  fibro-cartilages  is  made  at  the  same  time  as  that  of  the 
articulation  of  the  foot.  A  good  idea  of  the  shape  of  the  plantar  cushion  can  be  obtained  in  a 
longitudinal  and  median  section  of  the  digital  region  (Fig.  493),  and  on  the  piece  prepared  to 
show  tlie  subcorneal  tissue.  This  is  obtained  by  two  proce<lures.  In  the  fiist,  we  wait  until 
decomposition  has  softened  the  cells  between  the  hoof  and  the  keratogenous  membrane,  when 
the  hoof  can  be  easily  pulled  off.  In  the  second,  the  foot  is  kept  for  several  hours  in  boiling 
water,  then  held  in  a  vice  by  the  pastern  while  the  tissues  around  the  coronet  are  slightly  cut 
through ;  a  pair  of  shoeing  pincers  is  now  employed  at  the  heels  in  pulling  the  hoof  up  and 
down  until  it  comes  off.  The  foot  is  then  washed  to  free  it  from  tlie  debris.  (The  hoof  can 
also  be  removed  by  prolonged  maceration,  or  l>y  roasting  on  a  fire,  when  it  may  be  cut  and  torn 
off  by  the  farrier's  knife  and  pincers). 


Fig.  491. 


A.  Complementary  Apparatus  of  the  Pedal  Bone. — In  the  indication 
we  gave  of  this  apparatus  at  p.  117,  it  was  mentioned  that  it  was  composed  of 
two  lateral  pieces — thejibro-cartilages  of  the  pedal 
bone,  united  behind  and  below  by  the  plantar 
cushion — a  fibrous,  elastic  mass,  on  which  the 
navicular  bone  rests,  through  the  medium  of  the 
perforans  tendon.  We  will  take  this  distinction 
as  the  basis  of  our  study. 

1 .  Pibro-cartilages  of  the  Pedal  Bone. 
— Each  of  these  pieces  represents  a  plate  flattened 
on  both  sides,  having  the  form  of  an  oblique- 
angled  parallelogram,  and  prolonged  behind  the 
third  phalanx.  The  external  face  is  convex,  and 
pierced  with  openings  for  the  passage  of  veins  ; 
it  sUghtly  overhangs  that  of  the  pedal  bone.  The 
internal  face  is  concave,  channeled  by  vascular 
furrows,  and  covers,  in  front,  the  pedal  articula- 
tion, and  the  synovial  cul-de-sac  that  projects 
between  the  two  lateral  Ugaments  of  that  joint ; 
below  and  behind,  it  is  united  to  the  plantar 
cushion,  either  through  continuity  of  tissue,  as 
at  the  inferior  border,  or  by  fibrous  bands  passing 
from  one  to  the  other.  The  upper  harder,  some- 
times convex,  sometimes  rectilinear,  is  thin  and 
bevelled  like  a  shell ;  it  is  separated  from  the 
posterior  margin  by  an  obtuse  angle,  in  front  of 

which  this  border  is  often  broken  by  a  deep  notch  that  gives  passage  to  the  vessels 
and  nerves  of  the  digital  portion.  The  inferior  border  is  attached,  in  front,  to 
the  basilar  and  retrossal  processes ;  behind  the  latter,  it  is  reflected  inwards  to 
become  continuous  with  the  tissue  on  the  lower  face  of  the  plantar  cushion. 
The  posterior  border  is  oblique  from  before  to  behind,  and  above  to  below,  and 
joins  the  preceding  two.  The  anterior  border  is  oblique  in  the  same  direction, 
and  is  united  so  intimately  to  the  anterior  lateral  ligament  of  the  pedal  articula- 
tion, that  it  cannot  be  separated  from  it  except  by  an  artifice  of  dissection.  It 
60 


horizontal  section  of  the 
horse's  foot. 
1,  Front,  or  toe  of  the  hoof;  2,  thick- 
ness of  the  wall ;  3,  laminae ;  4, 
insertion  of  the  extensor  pedis ;  5, 
OS  pedis;  6,  navicular  bone  ;  .7, 
wings  of  the  os  pedis;  8,  lateral 
cartilage:  9,  flexor  pedis  tendon; 
10,  plantar  cushion;  11,  inflection 
of  the  wall,  or  "  bar;  "  12,  horny 
frog. 


THE  SENSORY  APPARATUSES. 


sends  to  this  ligament,  and  to  the  tendon  of  the  anterior  extensor  of  the 
phalanges,  a  fibrous  expansion  that  becomes  fused  with  that  of  the  opposite 
side. 

The  fibro-cartilages  comprise  in  their  structure  a  mixture  of  fibrous  and 
cartilaginous  tissue,  though  the  mixture  of  these  is  far  from  being  perfectly 
homogeneous,  or  everywhere  in  the  same  proportions. 

The  cartilages  of  the  fore  feet  are  thicker  and  more  extensive  than  those  of 
the  hind  ones. 

(The  lateral  fibro-cartilages  are  peculiar  to  Solipeds.) 

2.  Plantar  Cushion. — The  plantar  cushion  is  a  kind  of  wedge,  situated 
in  the  space  between  the  two  cartilaginous  plates  of  the  third  phalanx,  and 
between  the  perforans  tendon  and  the  lower  part  of  the  hoof.  Its  shape  allows 
it  to  be  considered  as  having  an  antero-superior  and 
an  infero-posterior  face,  a  base,  summit,  and  two  lateral 
borders. 

The  antero-superior  face  is  moulded  on  the  aponeu- 
rotic expansion  of  the  perforans  tendon,  and  is  "  covered 
by  a  cellulo-fibrous  membrane,  the  proper  tunic  of  the 
plantar  cushion,  which  is  continuous,  on  its  inner  face, 
with  the  fibrous  septa  by  which  this  organ  is  traversed, 
and  adheres  by  its  external  or  anterior  face  to  the 
reinforcing  sheath  interposed  between  it  and  the  per- 
forans tendon  "  (Bouley).  This  expansion  is  prolonged, 
above,  to  the  fetlock,  where  it  is  confounded  with  the 
superficial  fascia  of  the  metacarpal  region  ;  it  is  mar- 
gined, laterally,  by  two  small,  very  strong'  ligamentous 
bands  which,  at  their  middle  portion,  cross  in  a  very 
oblique  manner  the  fasciculus  formed  by  the  vessels 
and  nerves  of  the  digit.  Each  of  these  bands  is  fixed, 
superiorly,  to  the  base  of  the  rudimentary  digit  known 
as  the  ergot,  and  to  the  knob  of  the  lateral  metacarpal 
bone ;  their  inferior  extremity  is  attached  within  the 
retrossal  process. 

The  infero-posterior  face  of  the  cushion  is  covered 
by  the  keratogenous  membrane,  and  presents  at  its 
middle  the  pf/rcmidal  body,  a  prominence  exactly  like 
that  of  the  frog,  to  which  it  corresponds.  It  shows, 
then,  in  front,  a  single  conical  prolongation,  and  be- 
hind, two  divergent  prominences  separated  by  a  median  excavation. 

The  base  of  the  apparatus  lies  behind,  and  is  inclined  upwards  ;  it  is  divided 
by  a  depression  into  two  lateral  masses— the  bulbs  of  the  plantar  cushion— on  the 
inside  of  which  the  posterior  prominences  of  the  pyramidal  body  reach,  and 
which  become  confounded,  outwardly,  with  the  posterior  and  inferior  angle  of 
the  cartilaginous  plates.  This  portion  of  the  cushion  is,  like  the  anterior  face, 
covered  by  a  cellulo-fibrous  expansion,  which  separates  it  from  the  skin  of  the 
pastern ;  this  expansion  is  attached,  by  its  lateral  margins,  to  the  posterior 
border  of  the  cartilages,  and  continued,  superiorly,  on  the  surface  of  the  anterior 
expansion,  with  which  it  soon  unites. 

The  summit  (jjoint  or  apex)  forms  a  sharp  border,  more  or  less  regularly 
convex  ;  it  is  fixed  into  the  plantar  face  of  the  pedal  bone,  in  front  of  the  semi- 


LOWER  FACE  OF  THE  HORSE's 
FOOT,  THE  HOOF  HAVING 
BEEN   REMOVED. 

1,  Heel ;  2,  coronary  cushion; 
3,  branch  of  the  plantar 
cushion ;  4,  median  lacuna, 
or  commissure;  5,  laminsc 
of  the  bars ;  6,  velvety 
•  tissue  of  the  sole. 


THE  APPENDAGES  OF  THE  SKIN.  911 

lunar  ridge  and  the  insertion  of  the  perforans  tendon,  with  which  the  plantar 
cushion  mixes  its  fibres  at  this  part. 

The  lateral  borders  are  wider  behind  than  before,  in  consequence  of  the 
wedge-like  shape  of  the  whole  organ  ;  they  are  continuous  with  the  inner  face 
of  the  lateral  cartilages,  as  already  indicated  in  describing  the  latter. 

The  organization  of  the  plantar  cushion  differs  much  from  that  of  the  carti- 
lages. It  has  for  its  base  a  fibrous  structure,  continuous  with  that  which  consti- 
tutes the  fundamental  framework  of  these  ;  this  structure  is  very  dense  towards 
the  infero-posterior  part  of  the  organ,  and  becomes  gradually  looser  as  it  leaves 
this  region  ;  the  meshes  it  contains  are  filled  with  a  yellow  pulp  composed  of 
fine,  elastic,  and  connective  fibres,  in  the  midst  of  which  some  adipose  cells  are 
found.  (I  have  attentively  examined  this  yellow  pulp,  and  can  perceive  that  it 
is  essentially  constituted  by  adipose  tissue).  Numerous  blood-vessels  and  nerves 
complete  this  structure. 

B.  The  Keratogenous  or  Subcorneus  Membrane.— The  keratogenous 
membrane  envelops  the  extremity  of  the  digit,  by  spreading  over  the  terminal 
■expansion  of  the  tendon  of  the  extensor  pedis,  through  the  medium  of  a  fibrous 
fascia — a  dependency  of  the  lateral  cartilages  ;  and  also  over  the  inferior  moiety 
■of  the  external  face  of  these  cartilages,  the  bulbs  of  the  plantar  cushion,  pyramidal 
l)ody,  anterior  part  of  the  plantar  face  of  the  third  phalanx,  and  over  the  anterior 
•surface  of  the  same  bone.  It  covers  all  these  parts  like  a  sock,  and  the  hoof 
■encloses  it,  as  a  shoe  does  the  human  foot. 

This  membrane  becomes  continuous  with  the  skin  of  the  digital  region,  at  a 
circular  liue  that  intereects  the  middle  portion  of  the  second  phalanx,  and  in- 
clines obliquely  downward  from  behind  to  before.  Below  this  line,  in  front  and 
laterally,  the  subungular  tissues  form  a  semi-cylindrical  protuberance,  covered 
with  vilH,  and  designated  the  "  bouiTelet."  (This  elastic  prominence  has  received 
several  most  inappropriate  names  from  English  farriers  and  hippotomists,  such 
as  "  coronary  ligament,"  "  coronary  substance,"  "  cutiduris,"  etc.  From  its 
function,  structure,  situation,  and  its  analogy  to  the  plantar  cushion,  I  have 
designated  it  the  "  coronary  cushion.") 

On  the  plantar  cushion  and  the  lower  face  of  the  pedal  bone,  this  membrane 
becomes  a  villous  tunic — the  velvety  tissue — which  is  continuous,  towards  the 
bulbs,  with  the  extremities  of  the  coronary  cushion. 

The  portion  spread  over  the  anterior  face  of  the  third  phalanx  constitutes  the 
laminal  {podophyllous)  or  "leafy  tissue,"  so  called  because  of  the  laminae  or 
parallel  leaves  seen  on  its  surface. 

The  three  regions  of  the  keratogenous  apparatus  will  be  successively  studied. 

1.  Coronary  Cushion. — This  part  is  the  matrix  of  the  wall  of  the  hoof, 
and  is  lodged  in  a  cavity  excavated  at  the  upper  border  of  this  part  of  the  horny 
case.  It  forms,  according  to  the  expression  employed  by  M.  Bouley,  a  rounded 
prominence,  which  projects  like  a  cornice  above  the  podophyllous  tissue. 

Its  inferior  border  is  separated  by  a  white  zone  from  the  upper  extremity  of 
the  laminae,  which  constitute  this  boundary. 

The  superior  border  is  limited  by  a  slightly  projecting  margin  named  the 
perioplic  ring,  because  it  secretes  the  horn  of  the  periople.  Between  this  margin 
and  the  cushion  is  a  sharply  defined  groove. 

The  extremities,  narrower  than  the  middle  portion,  on  arriving  at  the  bulbs 
of  the  plantar  cushion,  bend  downwards  into  the  lateral  lacunae  of  the  pyramidal 
body,  where  they  become  confounded  with  the  velvety  tissue. 


912 


TEE  SENSORY  APPARATUSES. 


The  surface  of  the  organ  shows  filiform  prolongations,  a  little  constricted  at 
their  base,  and  named  papiJlcE,  viUo-papiUcB,  villi,  and  villous  loops,  the  size  of 
which  is  greatest  towards  the  lower  part  of  the  cushion  ;  those  of  the  perioplic 
ring  are  smallest.  Contained  within  the  minute  apertures  at  the  upper  part 
of  the  hoof -wall,  these  papillaB— considered  as  a  whole,  and  when  the  hoof  has 
been  removed  by  maceration — form  a  tufty  surface  most  perfectly  seen  when  the 
foot  is  suspended  in  water. 

The  structure  of  the  coronary  cushion  resembles  that  of  the  derma,  of  which 
it  is  in  reality  only  a  continuation.  It  comprises  a  fibrous  framework,  remark- 
able for  its  thickness  and  density,  with  a  considerable  number  of  vessels  and 
nerves,  the  ramifications  of  which  may  be  followed  to  the  extremity  of  the  villi. 


Fig.  493. 


LATERAL  VIEW  OF  THE  HORSE'S  FOOT, 
AFTER  REMOVAL  OF  THE  HOOF. 

1,  Perioplic  ring,  divided  by  a  narrow 
groove  from  the  coronary  cushion, 
2,  which  is  continuous  with  the 
plantar  cushion,  4,  and  join=  the 
vasculnr  laminae,  3,  through  the 
medium  of  the  white  zone. 


HIGHLY  MAGNIFIED  HORIZONTAL  SECTION  OF  A  HORSE'S 
HOOF,  SHOWING  THE  RELATIONS  BETWEEN  A  KERA- 
PHYLLOUS   AND   A    PODOPHYLLOUS    LAMINA. 

1,  Principal  podophyllous  lamina;  2,  secondary  ditto 
{laminella)  \  3,  elliptical  cells  (analogous  to  the  generat- 
ing layer  in  the  rete  Malphigii) ;  4.  cells  of  the  same, 
but  already  keratinized,  and  colourable  by  carmine ;  5, 
ke)ai>hyllous  lamina. 


To  its  great  vascularity  is  due  the  bright  red  colour  it  shows  on  its  surface ; 
this  colour  is  sometimes  masked  by  black  pigment. 

(I  have  found  a  notable  quantity  of  adipose  tissue  in  the  cushion). 

2.  Velvety  Tissue. — Much  thinner  than  the  plantar  cushion,  the  velvety 
tissue— the  formative  organ  of  the  sole  and  frog — extends  over  the  whole  of  the 
plantar  region  of  the  third  phalanx,  as  well  as  the  plantar  cushion,  the  bulbs  of 
which,  and  the  pyramidal  prominence  it  covers,  by  adapting  itself  exactly  to  the 
irregularities  of  this  elastic  mass. 

Its  surface,  which  altogether  resembles  the  general  configuration  of  the 
plantar  surface  of  the  hoof,  is  divisible  into  two  regions — a  central,  correspond- 
ing to  the  pyramidal  body  and  the  frog,  and  continuous  on  the  bulbs  of  the 
cushion  with  the  extremities  of  the  coronary  cushion  and  the  perioplic  ring,  but 
chiefly  with  the  latter ;  the   other,  peripheral,  is  covered  by  the  horny  sole. 


THE  APPENDAGES  OF  THE  SKIN.  913 

separated  from  the  podophyllous  tissue  by  the  plantar  border  of  the  foot,  some- 
what encroached  upon  posteriorly  by  the  laminae  corresponding  to  the  bars,  and 
is  continuous,  above  these  laminaB,  with  the  plantar  cushion. 

The  surface  of  the  velvety  tissue  is  studded  with  villi  similar  to  those  of  the 
coronary  cushion,  and  about  the  same  size.  The  longest  are  towards  the  cir- 
cumference of  this  surface,  and  the  shortest  in  the  median  lacuna  of  the  pyra- 
midal body ;  all  are  lodged  in  the  porosities  on  the  inner  surface  of  the  horny 
sole  and  frog. 

This  tissue  shows  the  same  organization  as  the  coronary  cushion.  The 
vascular  corium,  forming  its  base,  is  thickened  at  its  peripheral  portion  by  a 
fibrous  network  named  the  plantar  reticulum,  in  the  meshes  of  which  are  sustained 
the  veins  of  the  inferior  surface  of  the  foot. 

3.  Laminal  Tissue. — This  part  of  the  keratogenous  membrane  is  also 
very  frequently  designated  the  podophyllous  tissue  (and  still  more  frequently,  in 
this  country,  as  merely  the  lamiyim).  It  is  spread  over  tlie  anterior  face  of  the 
third  phalanx,  occupying  the  interval  between  the  plantar  border  of  that  bone 
and  the  lower  margin  of  the  coronary  cushion  ;  its  width  is,  therefore,  greater 
at  the  anterior  portion  of  the  phalanx  than  on  its  sides,  where  the  extremities  of 
the  membrane  are  reflected  below  the  bulbs  of  the  plantar  cushion  on  to  the 
velvety  tissue. 

This  membrane  owes  its  name  to  the  leaves  it  exhibits  on  its  superficies  ; 
these  are  from  five  to  six  hundred  in  number — we  have  counted  560 — run 
parallel  to  each  other,  and  are  separated  by  deep  channels,  into  which  are  dove- 
tailed analogous  leaves  from  the  inner  side  of  the  wall  of  the  hoof  ;  they  extend 
from  the  white  zone  that  hmits  the  inferior  border  of  the  coronary  cushion — 
where  they  are  not  so  salient — to  the  plantar  border  of  the  foot,  where  they 
each  terminate  in  five  or  six  very  large  villous  prolongations,  which  are  lodged 
in  the  horny  tubes  at  the  circumference  of  the  sole. 

The  leaves  {lamina)  of  the  podophyllous  tissue  increase  in  width  from  above 
to  below  ;  their  free  margin  is  finely  denticulated,  and,  under  the  influence  of 
any  inflammatory  cause  (laminitis,  ablation  of  the  horny  wall),  these  denticulse 
become  largely  developed,  and  transformed  into  veritable  papifla^.  Their  sides  are 
traversed  by  folds,  about  sixty  in  number,  which  pass  uninterruptedly  from  top 
to  bottom.  These  secondary  leaves,  or  lamellae,  are  fixed  obliquely  on  the  sides 
of  the  lamiufe,  as  the  barbules  of  a  feather  are  attached  to  the  barbs  (Figs.  494, 
4  ;  496,  f,"  c!') 

The  podophyllous  tissue  is  not  in  immediate  contact  with  the  keraphyllous 
tissue,  or  horny  laminge  ;  between  the  two  there  is  a  mass  of  soft,  elHptical  cells, 
always  destitute  of  pigment,  easily  stained  with  carmine,  and  appearing  to  stud 
the  ramifications  of  the  vascular  laminse  (Fig.  494,  4).  A  transverse  section  of 
the  union  of  the  hoof  with  these  laminae,  when  treated  with  carmine,  presents  a 
very  fine  aspect,  appearing  as  so  many  fern  or  acacia-of-Judsa  leaves  placed 
between  the  keraphyllous  laminae — the  principal  nerves  and  the  secondary 
nervules  of  the  leaves,  being  represented  by  the  lamina  and  its  lateral  ridges,  the 
limb  of  the  leaves  by  the  young  cells  spread  around  the  latter. 

The  structure  of  the  podophyllous  membrane  resembles  that  of  the  other  parts 
of  the  keratogenous  apparatus.  Its  corium  is,  like  that  of  the  peripheral  portion 
of  the  velvety  tissue,  separated  from  the  os  pedis  by  a  fibrous  reticulum,  which 
supports  the  veins,  and  forms,  to  some  extent,  the  periosteum  of  the  third 
phalanx. 


914 


TEE  SENSORY  APPARATUSES. 


The  leaves  of  the  podophyllous  membrane  are  immense  lamellar  papillae,  which 
should  be  included  among  the  principal  instruments  concerned  in  the  tactile 
sensibility  of  the  Horse's  foot,  and  which  play  a  really  mechanical  part,  in  con- 
curring— by  their  dovetailing  with  the  keraphyllous  (or  horny)  laminae — to  assure 
the  solidity  of  the  union  of  the  hoof  with  the  living  parts.     The  cells  which 

Fig.  495. 


be  d 

HORIZONTAL  SECTION   OF   THE    JUNCTION    OF    THE   WALL   WITH   THE    SOLE    OF   THE    HOOF. 

a,  Wall,  with  its  horn-tubes;  6,  6,  horny  laniinse  projecting  from  the  wall;  c,  c,  horn-tubes  formed 
by  the  terminal  villi  of  the  vascular  laminae,  the  horn  surrounding  them  and  occupying  the  spaces 
between  the  horny  laminae,  constituting  the  "  white  line ;  "  d,  horny  sole,  with  its  tubes. 

multiply  on  their  surface  have  usually  but  little  share  in  the  formation  of  the 
horn.     This  will,  however,  be  alluded  to  hereafter. 

h.  Description  of  the  Hoof. 

The  hoof  of  the  Horse — considered  as  a  whole — represents  a  kind  of  box  that 
envelopes  the  inferior  extremity  of  the  digit,  by  fitting  closely  on  the  keratogenous 


HORIZONTAL    SECTION    OF   THE   WALL,    AND    HORNY    AND   VASCULAR    LAMINA,    TO   SHOW   THE 
JUNCTION    OF   THE    LATTER   AND   THE   LAMINELLjE. 

a,  Inner  portion  of  the  wall  with  the  laminae  arising  from  it ;  6,  vascular  laminae ;  c,  horny  lamina 
of  aver.ige  length  ;  c',  c',  unusually  short  lamina;;  c",  c",  laminellae  on  the  sides  of  the  horny 
laminae  ;  d,  vascular  lamina  passing  between  two  horny  ditto ;  d',  vascular  lamina  passing 
between  three  horny  laminje  ;  d",  lateral  laminellae ;  e,  e,  arteries  of  vascular  laminae  which 
have  been  injected. 


membrane,  to  which  it  is  united  in  the  most  intimate  manner  by  a  reciprocal 
penetration  of  prolongations  into  cavities  that  exist  on  the  surfaces  in  contact. 

Its  general  shape  is,  as  was  demonstrated  by  Bracy  Clark,  that  of  the  moiety 
of  a  cylinder  cut  obliquely  across  its  middle,  and  resting  on  the  surface  of  this 
section.     In  nearly  all  feet,  however,  it  is  slightly  conical. 


THE  APPENDAGES  OF  THE  SKIN. 


915 


Prolonged  maceration  separates  it  into  three  portions — the  tvall,  sole,  and 
frog. 

Wall. — The  wall — also  named  the  crust — is  that  part  of  the  hoof  which  is 
apparent  when  the  foot  rests  on  the  ground.  This  thick  plate  of  horn  covers 
the  anterior  face  of  the  foot,  and,  gradually  narrowing  in  width  and  diminishing 
in  thickness,  passes  round  each  side  until  it  reaches  the  bulbs  of  the  plantar 
cushion,  when  its  extremities  are  sharply  inflected  inwards,  between  the  frog  and 
internal  border  of  the  sole,  becoming  confounded  with  the  latter  about  its  middle 
or  anterior  third,  after  being  greatly  reduced  in  breadth  and  substance. 

The  middle— or  anterior  part — of  this  horny  envelope  is  popularly  known  as 
the  toe ;  its  two  sides  are  designated  outside  and  inside  toe ,-  the  lateral  regions  con- 
stitute the  quarters ;  the  heels  are  formed  by  the  angles  of  inflection  of  its 
extremities  ;  while  these  extremities  themselves,  passing  along  the  inner  border 
of  the  sole,  are  termed  the  bars. 

Examined  with  regard  to  the  direction  it  follows  in  its  relations  with  the 
ground,  this  envelope  is  seen  to  be  much  inclined  in  its  middle  region  or  toe,  and 
this  obhquity  gradually  diminishes  until  the 
posterior  part  of  the  quarters  is  reached ;  at 
this  point  the  wall  is  nearly  perpendicular. 

The  following  are  the  characters  it  offers 
in  the  conformation  of  its  faces,  borders,  and 
extremities  : — 

The  external  face,  convex  from  side  to  side, 
and  perfectly  straight  from  the  upper  to  the 
lower  border,  is  smooth,  polished,  and  shining  : 
an  appearance  it  owes  to  a  thin  horny  layer, 
independent  of  the  wall  proper,  designated  the 
periople. 

This  periople  forms,  on  the  upper  part  of  the 
wall,  a  kind  of  ring,  continuous  with  the  bulbs 
of  the  plantar  cushion,  and  with  the  frog,  of 
which  it  is  only  a  dependency  ;  responding,  by 
its  upper  margin,  to  the  perioplic  ring,  which 
secretes  it ;  towards  the  lower  part  of  the  wall 
it  is  gradually  lost,  friction  incessantly  thinning 
and  destroying  it. 

The  inner  face  presents,  over  its  entire  ex- 
tent, the  white  parallel  leaves  which  dovetail  with  the  laminae  of  the  podophyllous 
tissue.     Collectively,  these  are  named  the  Iter  aphyllous  tissue. 

The  superior  border  is  bevelled  off,  on  its  inner  aspect,  into  a  circular  con- 
cavity, into  which  the  plantar  cushion  is  received.  This  excavation  is  named 
the  cutigercd  cavity,  because  of  its  relations  ;  it  offers  on  its  surface  a  multitude 
of  minute  openings — the  commencement  of  the  horny  canaliculi  which  receive 
the  villosities  of  the  cutiduris. 

The  inferior  border,  in  contact  with  the  ground,  and  subjected  to  wear  in 
unshod  animals,  is  united  inwardly,  and  in  the  most  intimate  manner,  with  the 
circumference  of  the  sole. 

The  extremities,  constituted  by  the  reflected  and  re-entering  prolongations 
known  as  the  bars,iorm,  outwardly,  the  external  side  of  the  lateral  lacunge  of  the 
frog  ;  they  are  provided,  inwardly,  with  laminas  like  the  rest  of  the  wall.     The 


HOOF    JUST   REMOVED   FROM   THE 
FOOT   (SIDE   view;. 

Inner  surface  of  periople,  or  coronary 
frog-band,  with  some  hairs  passing 
through  ;  a',  outer  surface  of  same 
at  posterior  part  of  foot ;  a",  a 
section  through  the  wall  to  show 
its  thickness;  6  to  c,  quarter  of  the 
hoof,  from  b  to  the  front  is  the  out- 
side (or  inside)  toe ;  from  c  to  d  the 
outside  (or  inside  heel)  ;  e,  frog  ;  /, 
bevel  on  upper  margin  of  wall  for 
reception  of  coronary  cushion ;  g, 
keraphylla,  or  horny  laminae. 


916 


THE  SENSORY  APPARATUSES. 


upper  margin  of  these  prolongations  is  confounded  with  the  frog  and  sole  ;  the 
lower  appears  between  these  two  parts,  and  is  effaced  at  a  certain  distance  from 
the  point  of  the  frog. 

Sole. — The  sole  is  a  thick  horny  plate  comprised  between  the  inner  border 
of  the  wall  and  its  reflected  prolongations  ;  thus  occupying  the  inferior  face  of 
the  hoof.     It  offers  two  faces  and  two  borders  or  circumferences. 

The  inferior,  or  external  face,  forms  a  more  or  less  concave  surface,  according 
to  circumstances.  The  superior,  or  internal  face,  corresponds  to  the  peripheral 
portion  of  the  velvety  tissue  ;  it  shows  a  multitude  of  little  apertures  analogous 
to  those  of  the  cutigeral  cavity,  into  which  are  inserted  the  papillae  of  the  kerato- 
genous  membrane. 

The  external  border,  or  large  circumference,  is  united,  throughout  its  extent,  to 
the  inner  contour  of  the  lower  border  of  the  wall,  by  means  of  its  denticulae, 


HOOF,  WITH  OUTER  PORTIOV  OF  THE  WALL 
REMOVED   TO  SHOW   ITS  INTERIOR. 

a,  a,  Periople,  or  coronary  frog-band;  6, 
cavity  in  upper  part  of  wall  for  coro- 
nary cushion ;  c,  upper,  or  inner,  surface 
of  "bar;"  d,  vertical  section  of  wall; 
d',  the  same  at  the  heel ;  e,  horizontal 
section  of  ditto ;  /',  horny  laminae  of 
bar;  /",  ditto  of  wall ;  /"',  lateral  aspect 
of  a  lamina;  g,  upper,  or  inner  surface 
of  the  horny  sole  ;  A,  junction  of  the 
horny  iHminae  with  the  sole  (the  "  white 
line");  i,  toe-stay  at  the  middle  of  the 
toe;  k,  upper,  or  inner  surface  of  the 
horny  frog;  I,  frog-stay;  m,  cavity 
corresponding  to  a  branch  of  the  frog; 
n,  ditto  corresponding  to  the  body  of 
the  frog. 


PLANTAR  OR  GROUND  SURFACE 
OF    A    HOOF   (right    FOOT). 

The  interval  from  a  to  a  repre- 
sents the  toe ;  from  a  to  6,  6, 
outside   and   inside  quarters; 

c,  0,  commencement  of  bars; 

d,  d,  inflections  of  wall  at  the 
heels,  or  "buttresses;"  e,  La- 
teral lacuna  ;  /,  /,  /,  sole  ;  g, 
white  line ;  g,'  g',  ditto  be- 
tween the  sole  and  bar;  h, 
body  of  frog ;  »,  branch  of 
frog;  k,  k,  glomes,  or  heels  of 
frog;  /,  median  lacuna. 


which  are  reciprocally  dovetailed  into  those  on  the  inner  face  of  the  wall  near  its 
inferior  border.  The  internal  border,  or  small  circumference,  is  a  deep,  V-shaped 
notch,  widest  behind,  which  corresponds  to  the  bars,  and  at  the  bottom  of  which 
the  point  of  the  frog  is  fixed. 

Frog. — This  is  a  mass  of  horn,  pyramidal  in  shape,  and  lodged  between  two 
re-entering  portions  of  the  wall.  It  offers  four  planes  (or  sides),  a  base,  and  a 
summit  (or  point). 

The  inferior  and  the  two  lateral  planes  constitute  the  external  surface  of  the 
organ.  The  first  is  hollowed  by  a  longitudinal  excavation,  which  is  shallow  in 
well-formed  hoofs,  and  is  named  the  median  lacuna  of  the  frog,  separating  the 
two  salient  portions,  or  branches,  which  diverge  posteriorly  find  join  the  heels. 
The  other  two  planes  are  directed  obliquely  downwards  and  inwards  ;  they  adhere 


TEE  APPENDAGES  OF  THE  SKIN.  917 

closely,  at  their  upper  third,  to  the  external  side  of  the  bars,  and  anteriorly  to  the 
inner  border  of  the  sole.  "  This  union  is  so  close  that  no  line  of  demarcation  is 
apparent  between  these  parts,  and  their  separation  can  only  be  obtained  by  pro- 
longed maceration.  The  non-adherent,  or  free  portion,  forms  the  inner  side  of 
the  cavities  know  as  the  lateral  lacunce,  or  commissures  of  the  frog,  whose  external 
side  is  constituted  by  the  inferior  face  of  the  bars  "  (Bouley). 

The  superior  plane,  forming  the  internal  face  of  the  frog,  is  cribbled  with 
holes  like  that  of  the  sole,  and  is  exactly  moulded  on  the  pyramidal  body  of 
the  plantar  cushion.  It  also  offers  a  triangular  excavation,  divided  posteriorly 
into  two  latter  channels  by  a  prominence  directed  from  before  backwards,  to 
which  Bracy  Clark  gave  the  name  of  frog-stay,  but  which  M.  Bouley  prefers  to 
designate  the  stay  {arete — spine  or  ridge)  of  the  frog. 

The  hase  or  posterior  extremity  of  the  frog,  constituted  by  the  extremities  of 
its  branches,  forms  two  rounded,  flexible,  and  elastic  eminences  separated  from 
each  other  by  the  median  lacuna  ;  they  cover  the  angles  of  inflection  of  the  wall, 
and  are  continuous  at  this  point  with  the  perioplic  band.  Bracy  Clark  named 
them  the  glomes  of  the  frog. 

With  regard  to  the  summit — or  anterior  extremity  of  the  organ — it  is  a  point 
wedged  in  the  re-entering  angle  comprised  between  the  two  portions  of  the  inner 
border  of  the  sole. 

In  the  Ass  and  Mule,  the  hoof  is  always  naiTower,  laterally,  than  that  of  the 
horse  ;  the  wall  is  always  higher  and  thicker,  the  sole  more  concave,  the  frog 
smaller  and  deeper  seated  at  the  bottom  of  the  excavation  formed  by  the  sole, 
and  the  horn  is  much  more  hard  and  resisting.^ 

(The  angle  of  the  wall  of  the  hoof  in  front  varies  from  50°  to  56°,  though 
usually  eiToneously  stated  to  be  45°.  The  inner  face  of  the  wall— at  the  middle 
of  the  toe,  and  in  a  line  with  the  frog-stay — frequently  shows  a  more  or  less  salient 
and  conical  prominence — base  towards  the  lower  margin  of  the  wall — which 
corresponds  to  a  vertical  depre'fesion  in  the  os  pedis.  Vallada  imagined  that  this 
projection  served  to  unite  the  wall  and  sole  more  closely,  but  it  is  far  more  pro- 
bable that  its  function  is  the  same  as  that  of  the  frog-stay— to  maintain  the 
position  of  the  os  pedis,  and  prevent  its  rotation  within  the  hoof.  I  have,  there- 
fore, named  it  the  "  toe-stay.") 

Structure  of  the  Hoof-horn.— The  structure  of  the  horn  has  been  the 
subject  of  a  great  number  of  researches  ;  Gurlt,  Delafond,  Bouley,  Gourdon,  and 
Ercolani  ^  have  given  descriptions  of  it,  and  we  have  also  some  details  to  add  to 
the  labours  of  these  authorities. 

The  hortiy  substance  constituting  the  hoof  of  Solipeds,  has  a  fibrous  appearance ; 
this  is  most  conspicuous  in  the  wall,  less  apparent  in  the  frog  and  deeper  portions 
of  the  sole,  but  impossible  to  distinguish  in  the  superficial  layer  of  the  latter, 
where  the  disintegration  continually  taking  place  separates  the  horn  in  scaly 
fragments  of  varying  thickness  and  extent.  The  consistence  of  the  horn  is 
always  less  in  the  frog  than  in  the  sole  and  wall.  Its  tint  is  in  some  hoofs  black, 
in  others  white,  and  in  others,  again,  a  mixture  of  these  two.  The  inner  face  of 
the  wall,  however,  is  never  black  ;  and  when  the  lower  part  of  the  limb  is  partially 

'  The  third  phalanx  of  the  anterior  limb  of  these  animals  has  the  same  shape  as  in  the 
Horse,  notwithstanding  the  lateral  flattening  of  the  hoof  covering  it. 

*  (The  researches  of  Professor  Kawitsch  must  be  omitted.  They  will  be  found  in  vol. 
xxviii  of  the  Marfazin  fur  Thierheilliiinde,  and  also  in  a  little  brorhure  entitled  Ueber  den 
feineren  Ban  und  das  Wnchdhum  des  Hufhorns— Berlin  :  1863.  Leisering  must  likewise  be 
referred  to.     My  own  researoht  s  are  published  in  the  Veterinarian  for  1871.) 


918  THt:  SENSORY  APPARATUSES. 

or  wholly  white,  we  may  be  sure  that  all  the  thickness  of  the  wall  will  either  be 
white  at  corresponding  points  in  the  former,  or  entirely  so  in  the  latter. 

Except  in  the  keraphyllons  tissue,  the  minute  structure  of  the  hoof-horn 
always  exhibits  the  same  characters.  Everywhere  it  is  perforated  by  cylindrical 
canals,  the  upper  end  of  which  is  funnel-shaped,  and  these  contain  the  papillae  of  the 
matrix,  whether  they  belong  to  the  coronary  cushion  or  velvety  tissue  ;  while  the 
lower  end  reaches  the  inferior  border  of  the  wall,  or  lower  face  of  the  sole  and 
frog,  according  to  their  situation.  It  is  rare  to  find  them  in  the  horny  laminae. 
All  are  rectilinear,  with  the  exception  of  those  of  the  frog,  which  are  somewhat 
flexuous  ;  and  all  have  the  same  oblique  direction  downward  and  forward, 
following  the  inclination  of  the  anterior  portion  of  the  wall.  They  are,  therefore, 
almost  exactly  parallel  to  each  other,  not  only  in  the  same,  but  in  two  different 
regions.  Their  diameter  varies  considerably,  though  the  smallest  are  always  those 
of  the  periople  ;  in  the  wall,  they  are  smaller  as  they  approach  the  outer  surface. 

These  tubes  are  not  mere  canals  hollowed  out  of  the  horny  substance  ;  on  the 
contrary,  they  have  very  thick  walls  which  are  formed  of  numerous  concentric 
layers,  one  within  the  other,  and  the  horny  tissue  connecting  them  has  not  the 
same  apparent  stratiform  disposition.  Filled  by  the  papillte  of  the  keratogenous 
membrane  at  their  superior  extremity,  these  canals  are  not  empty  for  the  remainder 
of  their  extent  :  but  contain  a  particular  white  substance,  which  is  so  opaque 
that  it  appears  of  a  fine  black  hue  when  examined  as  a  transparency  in  the  micro- 
scope. This  matter  is  not  deposited  in  a  uniform  manner  in  the  canals,  but 
irregularly,  looking  like  a  knotted  cord  or  a  necklet  of  beads  ;  and  where  it  does 
exist,  it  does  not  always  exactly  fill  the  calibre  of  the  tube,  an  interval  being 
observed  between  the  inner  face  of  the  latter  and  the  intra-tubular  deposit. 
Sometimes  it  is  seen  outside  the  canals,  among  the  concentric  lamellae,  and  even 
in  the  horny  intertubular  substance 

If  we  are  desirous  of  completing  our  knowledge  of  the  minute  organization 
of  the  hoof -horn  by  studying  the  anatomical  elements  constituting  it,  we  shall  find 
that  it  is  formed  of  epithelial  cells  belonging  to  the  kind  most  widespread  in 
the  economy — pavement  epithelium.  These  horn  epithelial  cells  are  very  thin, 
pale,  polygonal,  and  generally  oblong,  have  sharply  defined  borders  and  finely 
granular  faces,  sometimes  showing  a  nucleus  containing  a  single  or  multiple 
nucleolus.  The  nuclei  sometimes  occupy  the  centre,  at  other  times  another  part 
of  the  cells — even  their  margins  ;  and  they  also  contain  pigment-granules  more 
or  less  coloured  and  numerous.  Acetic  acid  acts  very  slowly  on  them,  and  is 
limited  to  making  them  more  transparent.  Potassium  and  soda  at  first  softens, 
then  distends  them,  causing  their  granulated  aspect  to  disappear,  and  rounding 
their  contours ;  afterwards,  they  become  quite  diaphanous,  and  finish  by  being 
completely  dissolved 

Examined  in  their  reciprocal  relations,  these  epithelial  cells  are  seen  not  to 
be  agglomerated  comfusedly  together,  but  are,  on  the  contrary,  disposed  in  a 
regular  manner,  forming  a  real  framework  that  wonderfully  concurs  in  assuring 
solidity  and  flexibility.  In  the  walls  of  the  tubes  we  see  them  arranged 
horizontally  around  the  canal,  and  stratified  from  within  to  without,  so  as  to 
form  successive  concentric  layers.  In  the  intertubular  horn  they  are  disposed 
differently,  their  stratification  being  no  longer  parallel  to  the  direction  of  the 
tubes,  but  perpendicular  to  it,  and  piled  upon  each  other  in  the  intervals 
separating  the  latter.  This  change  of  direction  does  not  occur  suddenly  ;  at 
the  limits  of  the  tubes  epithelial  cells  are  seen  lying  obliquely. 


THE  APPENDAGES  OF  THE  SKIN. 


919 


In  a  transverse  section  of  the  wall,  there  are  observed  around  the  tubes,  in 
the  intertubular  substance,  as  well  as  in  the  horny  laminae,  small  irregularly 
elliptical  spaces  containing  a  solid  denticulated  mass  of  a  brownish  tint,  which  is 
easily  stained  with  carmine.  These  bodies  are  more  elongated  in  the  inter- 
tubular substance  than  in  the  walls  of  the  tubes,  and  have  a  certain  resemblance 
to  the  cartilaginous  capsules,  but  especially  to  the  bone  cavities  filled  by  their 
contents. 

Independently  of  the  hard,  dry,  and  flattened  cells,  there  is  found  an  opaque 
substance  that  partly  fills  the  tubes,  and  which  is  also  sometimes  met  with  in 
their  walls.  This  material  does  not  differ  from  the  last  in  its  nature  ;  it  is  also 
formed,  as  has  been  asserted  by  Gourdon  and  Ercolani,  of  irregular  granular 
cells  which  are  stained  by  the  carminate  of  •  ammonia. 

Figment-corpuscles  are  found  in  the  substance  of  the  coloured  horn,  and  are 
disposed  singly,  or  in  small  masses,  in  the  epithelial  cells  of  the  inter-tubular 


Fig.  501. 


HORN-CELLS    FROM   THE   SOLE 
OF   THE    HOOF. 

a,  Young  cells  from  the  upper 
surface  of  the  sole;  b,  cells 
from  the  lower  surface,  or 
dead  horn  of  the  sole. 


CONSTITUENT    ELEMENTS 
OF    THE    WALL. 

a,  Horn-cells ;  6,  horn- 
fibre  from  the  hoof  of  a 
new-born  foal,  showing 
the  vertical  disposition 
of  the  cells. 


substance.  The  presence  of  these  corpuscles  has  been  denied,  and  the  coloration 
has  been  attributed  to  a  greater  condensation,  at  certain  points,  of  the  epithelial 
elements.  Fine  pigment-granules  are  disseminated  in  the  cells,  but  it  is  evident 
that  beyond  these  there  are  at  different  points  pigment-corpuscles  ;  for,  after 
treating  a  section  of  coloured  horn  with  soda,  the  epithelial  elements  are  distended, 
become  pale,  and  disappear,  leaving,  however,  here  and  there,  masses  of  black 
granulations.     These  pigmentary  corpuscles  are  absent  in  white  horn. 

Development  of  the  Hoof. — The  hoof  being  a  dependency  of  the  epidermis, 
is  developed  like  it — that  is,  by  the  incessant  formation  of  cells  in  the  layer  that 
corresponds  to  the  stratum  mucosum.  The  velvety  tissue  forms  the  sole  and 
frog  ;  the  perioplic  ring  the  periople,  and  the  coronary  cushion  the  wall.  In 
these  different  parts,  the  epithelial  cells  multiply,  and  become  flattened  in  layers 
parallel  to  the  surface  that  secretes  them,  and  in  proportion  as  they  recede  from 


920  THE  SENSORY  APPARATUSES. 

that  surface  ;  so  that  the  wall  grows  from  its  superior  to  its  inferior  border,  and 
the  other  two  parts  of  the  hoof  from  their  internal  to  their  external  face. 

The  villi  of  the  coronary  cushion  and  the  velvety  tissue  are  the  organs 
around  which  the  epithelial  lamellae  are  grouped,  and  their  presence  determines 
the  tubular  structure  of  the  horn  ;  their  function  is  completed  by  the  exhalation 
of  a  particular  fluid  that  maintains  the  flexibility  of  the  hoof,  and,  probably, 
by  the  development  on  their  surface  of  the  irregular  cells  which  cluster  in  the 
interior  of  the  tubes. 

The  laminal  tissue,  in  a  normal  condition,  does  not  concur  to  any  extent  in 
the  development  of  the  wall.  The  cells  covering  it  are  multiplied  in  describing 
a  downward  and  forward  movement ;  and  though  they  are  certainly  applied  to 
the  inner  face  of  the  wall,  yet  they  do  not  constitute  the  horny  lamiuis.  The 
latter  are  formed  on  the  coronary  cushion,  at  the  commencement  of  the  vascular 
laminae,  and  they  descend  with  the  wall  in  gliding  along  the  surface  of  the  layer 
of  cells  separating  them  from  the  latter  ;  this  downward  movement  is  facilitated 
by  the  multiplication,  in  the  same  sense,  of  these  cells.  This  opinion  as  to 
the  function  of  the  vascular  laminae  is  based  on  comparative  anatomy,  on  the 
presence  of  some  longitudinal  tubes  in  the  horny  laminae,  and  on  pathological 
observations. 

When  the  podophyllous  tissue  is  inflamed — whether  or  not  it  be  exposed — its 
latent  activity  is  quickly  manifested,  and  it  rapidly  throws  out  a  large  quantity 
of  hard  consistent  horn,  traversed  by  tubes  which,  according  to  Gourdon,  are 
directed  obliquely  backwards.  These  tubes  are  more  irregular  than  those  of  the 
normal  wall,  are  disposed  in  parallel  series,  and  are  formed  around  the  villo- 
papillae  developed  on  the  free  border  of  the  laminae.  In  this  horn,  produced  by 
the  vascular  laminae  only,  there  are  never  observed  between  these  latter  the 
horny  plates  of  cells — sharp  and  distinct  in  the  midst  of  the  other  cells,  as  in 
those  of  the  wall  formed  by  the  coronary  cushion. 

The  horn  thrown  out  on  the  surface  of  the  podophyllae,  immediately  after 
the  removal  of  a  fragment  of  the  wall,  is  not  a  definitive  horn,  but  must 
be  replaced  by  that  from  the  coronet.  This  substitution  is  complete ;  as  a 
microscopical  examination  proves  that  the  wall  which  descends  from  the  cushion, 
and  is  furnished  with  horny  laminas,  passes  beneath  the  provisional  wall,  and 
glides  downward — by  the  combined  action  already  mentioned — over  the  surface 
of  the  soft  cells  of  the  vascular  laminae.  As  soon  as  the  latter  are  covered  by 
the  proper  wall,  their  marginal  papillae  become  atrophied,  and  they  again  assume 
the  limited  function  pertaining  to  their  physiological  condition. 

(The  description  of  the  disposition  of  the  epithehal  cells  given  by  Chauveau 
does  not  quite  coincide  with  my  own  observations.  As  he  correctly  states,  these 
cells  are  formed  in  planes  parallel  with  the  surface  that  secretes  them  ;  conse- 
quently, around  the  papillae  they  are  more  or  less  vertical,  while  between  them  they 
are  horizontal.  The  walls  of  the  tubes,  or  fibres,  are  therefore  composed  of  cells 
disposed  in  a  vertical  manner ;  while  in  the  inter-fibrous  horny  matter  they 
are  arranged  in  the  opposite  direction.  The  loose  nodulated  contents  of  the 
tube  is  composed  of  cells  thrown  off  from  the  termination  of  the  papilla,  and 
corresponds  to  the  pith  of  feathers.  The  soft  cells  interposed  between  the 
vascular  and  horny  laminas  are  carried  down  to  the  lower  margin  of  the  wall, 
where — with  the  elastic  horn  secreted  by  the  papillae  which  terminate  the  former — 
they  constitute  the  peculiar  light-coloured  band,  or  "  white  line,"  which  marks 
the  junction  of  the  sole  with  the  wall  (Fig.  499,  g).     This  intermediate  band  of 


THE  APPENDAGES  OF  THE  SKIN.  921 

soft  flexible  horn  at  this  point  obviates  tearing  of  the  sole  from  the  wall,  and 
fracture  of  the  former.    The  cells  of  the  horny  laminae  are  more  or  less  fusiform. 

The  beautiful  lateral  leaflets  on  the  sides  of  the  horny  laminte — corresponding 
to  those  on  the  vascular  leaves — were  observed  by  me  in  1858  ;  in  1862  they 
were  described  by  Rawitsch  and  Ercolani,  and,  at  a  later  period,  by  Colin  of 
Alfort  and  Leisering  of  Dresden.  They  are  very  conspicuous  in  a  well-prepared 
section — Fig.  496,  c",  c",  d". 

It  should  be  observed  that  the  growth  of  the  wall  of  the  hoof  is  indefinite, 
but  that  the  sole  and  frog,  after  attaining  a  certain  thickness,  exfoliate.  For 
complete  details  as  to  the  physiology  of  the  Horse's  foot,  the  student  is  referred 
to  the  Veterinarian  for  1871. 

It  may  here  be  noted  that  hairs  and  horn-tissue  contain  a  substance  named 
keratin,  which  is  remarkable  for  the  large  proportion  of  sulphui'  existing  in  it  in 
a  loose  or  free  state.) 

2.  The  Claws  of  Rumikants  and  Pachyderms. 

In  the  Ox,  Sheep,  and  Pig,  the  plantar  cushion  covers  the  bulb  of  the  heel  of  each  digit, 
wliere  it  furms  a  convex  mass ;  it  extends  to  the  insertion  of  the  deep  flexor  tendons  of  the 
phalanges,  in  becoming  triangular  in  shape,  and  thinner. 

In  the  Camel,  the  foot  rests  on  the  ground  by  the  lower  face  of  the  two  last  phalanges. 
These  are  protected  by  a  double  elastic  cushion,  but  covered  behind  by  a  single  horny  sandal. 
Tlie  third  phalanx  is  continued  in  a  short  and  very  convex  claw,  resembling  somewhat  a  Dog's 
claw. 

The  keratogenous  membrane  has  the  same  regions  as  in  the  Horse.  The  periople  is  separated 
from  the  coronary  cushion  by  a  well-marked  groove,  and  has  very  large  papillae.  The  parietal 
coronary  cushion  is  wide  and  flat,  of  a  brownish  tint  in  its  upper  moiety,  white  iuferiorly ;  it 
blends  behind  with  the  velvety  tissue  of  the  plantar  cushion,  and  ends  in  a  point  inwardly. 
The  papillae  covering  it  are  smaller  than  those  of  the  periople  and  velvety  tissue.  The  laminae 
of  the  podophyllous  tissue  are  nearer  each  other,  and  proportionately  wider  than  in  Solipeds; 
they  are  furnished  with  somewhat  atrophied  laminellse. 

The  liorny  envelope  enclosing  the  extremity  of  the  digits  of  the  Ox,  Sheep,  and  Pig, 
is  a  kind  of  copula,  having  almost  the  form  of  the  third  phalanx ;  it  is  usually  named  the  claw. 

The  claw  of  the  Ox  has  an  outer  face  resembling  the  wall  of  the  Horse's  hoof,  and  an  inner 
face  which  is  slightly  concave,  and  marked  by  undulating  grooves ;  owing  to  this  concavity 
the  two  claws  of  each  foot  only  touch  at  the  extremities  of  their  adjacent  faces.  The  plantar 
region  of  the  claw  is  slightly  depressed,  and  but  little  developed ;  it  is  chiefly  made  up  of  the 
plantar  cushion,  which  is  covered  by  a  thin  layer  of  supple  tubular  horn.  On  the  interior  of 
the  claw  is  seen  a  wide  shallow  cutigeral  cavity,  perforated  by  very  fine  openings,  and  laminae 
thinner  and  more  numerous  than  in  the  Horse's  hoof.  The  tubes  of  the  claw-horn  are  very 
small,  being  surpassed  in  diameter  by  those  of  the  periople  and  sole. 

Above  and  behind  each  claw  are  two  little  rudimentary  horny  capsules,  which  are  named 
ergots.  They  are  absent  in  the  Camel.  (Each  ergot  contains  a  small  bone,  which  is  not 
attached  to  the  skeleton  in  Ruminants.  In  the  Pig,  these  rudimentary  claws  are  larger,  and 
are  connected  with  the  bones  of  the  leg.  In  this  animal  the  horn  of  the  claws  is  altogether 
thinner,  softer,  and  less  resisting  than  in  Solipeds.  The  ergot  is  the  representative  of  those 
digits  which  are  apparently  absent  in  the  solid  and  cloven  foot.) 

3.  The  Claws  of  Caenivora. 

In  these  animals,  the  third  phalanx  of  the  digits  is  enveloped  in  a  conical  horny  sheath 
that  curves  downwards  like  the  bone  itself.  This  covering  is  designated  the  claw,  or  nail,  and 
off'ers  somewhat  the  same  organization  as  the  horns  of  Ruminants ;  it  is  developed,  and  grows 
in  the  same  manner,  as  the  hoof  of  Solipeds,  its  matrix  being  a  prolongation  of  the  corium 
which  extends  over  the  third  phalanx,  after  dipping  into  the  circular  furrow  at  the  base  of  that 
bone. 

Placed  at  the  extremity  of  the  digital  region,  the  claw  in  these  animals  is  not  utilized  in 
locomotion,  as  the  foot  does  not  rest  on  the  ground  by  the  extremities  of  the  digits,  but  by  the 
whole  plantar  surface.  Therefore  it  is,  that  we  find  on  this  face  a  kind  of  epidermic  sandal 
covering  five  fibro-adipose  tubercles— four  small  ones  placed  along  the  four  principal  digits 


922  TEE  SENSORY  APPARATUSES. 

(the  fifth  or  thumb  not  being  sufficiently  developed  to  reach  the  ground),  and  a  large  central 
one,  circumscribed  in  front  by  the  others.  This  arrangement  diffuses  the  pressure  caused 
by  the  weight  of  the  body  (and,  doubtless,  ameliorates  the  concussion  arising  from  the 
exertions  these  animals  make,  as  well  as  ensures  their  footsteps  being  noiseless  when 
approaching  their  prey). 

In  the  Cat,  the  claws  are  very  sharp  and  retractile ;  being  capable  of  erection  and  depression 
in  the  interdigital  spaces,  by  means  of  a  small  yellow  elastic  ligament  passing  from  the  second 
to  the  third  phalanx.  This  animal's  claws  constitute  its  most  powerful  weapon  of  attack  and 
defence. 

In  the  Rabbit,  the  claws  enable  it  to  burrow  in  the  ground :  and  the  Dog  can  also  employ 
them  in  this  manner. 

4.  The  Frontal  Horns. 

These  are  conical  horny  sheaths,  more  or  less  large  and  curveil,  and  annulated  transversely ; 
they  are  formed  by  concentric  layers  of  epithelial  cells  and  some  pigment-corpuscles.  The 
horns  grow  in  the  same  manner  as  the  wall  of  the  Horse's  hoof.  The  kerato^enous  membrane 
covering  the  core  arising  from  the  frontal  bone,  like  that  covering  the  last  phalanx  of  the 
Horse,  has  a  papillary  coronary  portion  at  the  base,  and  a  laminer  portion  lor  the  remainder 
of  its  extent.     The  coronary  base  fijrms  the  matrix  for  the  horn. 

(The  length,  direction,  and  general  form  of  the  horns  varies  in  Ruminants,  not  only  with 
regard  to  species,  age,  and  race,  but  also  sex.  The  Bull,  in  the  Bovine  species,  generally  has 
short,  thick,  powerful  horns;  the  Cow,  long  and  slender  ones;  and  the  Ox,  Lirge,  long,  and 
strong  ones.  Some  breeds  have  no  horns  at  all.  It  is  the  same  with  the  Goat  species, 
though  generally  the  horns  in  these  are  long,  flattened,  and  curved  backwards  and  downwards. 
With  the  Ram,  the  horns  are  sometimes  immense  and  very  powerful,  being  of  a  spiral  form. 
They  are  usually  less,  or  altogether  absent,  in  the  Ewe.  In  the  Bovine  species,  the  transverse 
rings  on  the  horns  serve  to  indicate  the  age,  the  first  appearing  after  two  years.) 

5.  The  Chestnuts. 

This  name  is  given  to  a  little  horny  (oval  or  round)  plate  found,  in  the  Horse,  on  the  inner 
face  of  the  forearm — in  the  lower  third  of  the  region,  and  at  the  upper  extremity  of  the  inner 
face  of  the  metatarsal  bone.  It  is  composed  of  a  mass  of  epithelial  cells,  arranged  in  tubes 
like  the  horn  of  the  hoof.  In  Solipeds,  the  chestnut  is  the  representative  of  tlie  thumb.' 
That  on  the  posterior  limbs  is  absent  in  the  Ass ;  in  the  Mule  it  is  very  small. 

(In  fine-bred  Horses,  this  horny  production  is  much  less  developed  than  in  the  coarser 
breeds.     It  is  always  smaller  in  the  hind  limbs. 

6.  The  Ergots. 
In  the  hind  and  fore  legs,  we  also  find  a  similar,  but  smaller  corneous  mass,  growing  from 
the  skin  of  the  fetlock,  and  named  the  ergot.     Like  the  chestnut,  it  bears  the  same  relative 
development  in  fine  and  coarse-bred  horses.) 


CHAPTER  II. 

APPARATUS   OP   TASTE. 

The  sense  of  taste  permits  the  appreciation  of  savours,  or  the  sapid  properties  of 
bodies. 

Two  nerves — the  chorda  tympani  and  the  lingual  branch  of  the  ninth  pair — 
appear  at  present  to  be  the  only  sensory  filaments  endowed  with  the  exercise  of 
this  function.  They  ramify  in  the  lingual  mucous  membrane,  which  is  thus 
made  the  organ  of  taste.     (Three  nerves  are  usually  mentioned  :  1.  The  glosso- 

('  This  is  very  doubtful,  particularly  for  any  member  of  the  class  Ungulata ;  and  from  the 
fact  that  in  the  Rhinoceros  and  Tapir  the  second  digit  is  perfectly  developed,  these  epidermic 
appendages  would  be  most  probably  larger  in  them  than  in  the  Horse,  if  they  represented  the 
pollex  and  hallux;  however,  they  are  altogether  absent.  Besides,  in  the  anterior  limb  of 
the  Horse  and  Ass  they  are  above  the  carpus.) 


TEE  APPARATUS  OF  TASTE.  923 

pharyngeal,  distributed  to  the  superior  third  of  the  tongue.  2.  The  lingual 
branch  of  the  fifth,  distributed  to  the  anterior  two-thirds.  3.  Filaments  from 
the  chorda  tympani.) 

The  tongue  and  its  investing  membrane  having  been  described  at  p.  400, 
their  anatomy  need  not  again  be  referred  to  ;  but  we  must  glance  at  the  organi- 
zation of  the  latter,  in  considering  it  as  the  special  apparatus  of  gustation.  This 
will  necessitate  a  few  words  with  regard  to  the  free  surface  of  the  membrane 
which  comes  into  contact  with  the  sapid  bodies,  and  some  considerations  on  the 
terminations  of  the  nerves  wliich  transmit  the  impressions  produced  by  these 
bodies  to  the  brain. 

Free  Surface  of  the  Lingual  Mucous  Membrane. — This  surface  is 
studded  by  a  multitude  of  papillary  prolongations,  which  are  nearly  all  Kmited 
to  the  upper  surface  of  the  tongue,  to  which  they  give  a  tufty  appearance. 
Their  form  and  volume,  as  mentioned  at  p.  402,  are  very  variable,  according  to 
their  situation  :  some  are  microscopic,  while  others  form  voluminous  caruncles  ; 
others,  again,  are  long,  conical,  and  fihform  ;  another  variety  is  round  or 
depressed,  representing  a  hemispherical  tubercle  scarcely  projected  beyond  the 
general  surface,  or  placed  at  the  bottom  of  an  excavation  in  the  mucous  mem- 
brane. The  latter  constitute  the  circumvallate  papillcB  {p.  circumvalatce,  p. 
letiticulares),  and  are  considered  the  true  organs  of  gustation  ;  the  others  are 
the  fungiform  {p.  capitat(c)  and  filiform  papilke,  which  play  a  mechanical  part  on 
the  surface  of  the  tongue. 

The  circumvallate  papiUce  in  the  Horse  are  two  in  number,  and  situated  near 
the  base  of  the  tongue  ;  their  diameter  is  so  considerable  that  they  have  been 
named  the  blind  or  caecal  openings  (taste-pores).  They  are  the  principal,  but 
not  the  only  organs  of  taste.  Their  surface  is  mammillated,  each  prominence 
corresponding  to  a  single  papilla,  and  being  placed  below  the  level  of  the  raised 
border  encircling  them.  A  deep  fossa  surrounds  them,  and  limits  at  their  base 
a  pedicle,  which  unites  them  to  the  other  portions  of  the  mucous  membrane  (see 
Figs.  218,  219). 

The  circumvallate  papillae  show,  around  their  peduncle,  a  band  of  adenoid 
tissue  ;  and  in  their  substance  conglomerate  glands,  as  in  other  parts  of  the 
mucous  membrane.  They  are  covered  by  an  epithelium  containing  some 
scattered  pigment-granules,  the  thickness  of  which  is  much  diminished  at  the 
bottom  of  the  fossa  circumscribing  them. 

Termination  of  the  Gustatory  Nerves. — The  hypoglossal  is  the  motor 
nerve  of  the  tongue,  the  lingual  the  nerve  of  general  sensibility,  and  the  chorda 
tympani  and  glosso-pharyngeal  the  filaments  of  special  sensibility  :  this  appears 
to  be  clearly  ascertained  from  the  recent  experiments  and  observations  of  Lussana, 
The  lingual  branch  of  the  glosso-pharyngeal  nerve  gives  gustatory  sensibility  to 
the  posterior  third  of  the  tongue  ;  the  chorda  tympani  to  the  anterior  two-thirds. 

The  gustatory  nerves  present— as  do  all  those  of  the  organs  of  sense — a  par- 
ticular mode  of  termination.  First  indicated  by  Axel  Key,  their  special  manner 
of  terminating  has  been  carefully  studied  by  Lowen,  Schwalbe,  and  Ranvier. 
According  to  these  anatomists,  the  terminal  nerve-tubes  lose  their  medullary 
envelope,  and,  reduced  to  their  axis-cylinder,  are  thrown  out  in  small  oval  masses 
which  might  be  termed  gmtative  huJbs  (taste-buds,  or  taste-goblets).  Sartoli  and 
Ranvier  have  seen  some  directly  enter  the  epithelium  around  the  bulbs.  The 
gustatory  bulbs  are  more  particularly  placed  around  the  pedicles  of  the  calyciform 
papillae,  in  the  substance  of   the  epithelium.     They  are  fusiform,  their  inner 


924  THE  SENSORY  APPARATUSES. 

extremity  rests  on  the  mucous  derma,  where  they  receive  the  terminal  nerve- 
tubes  ;  and  their  external  extremity  reaches  the  epithelial  layer,  where  they  are 
seen  either  between  two  cells,  or  in  an  orifice  pierced  in  a  single  pavement  cell. 
Each  taste-body  is  composed  of  a  small  cluster  of  cells,  which  are  distinguished 
from  each  other  by  their  character  and  position  ;  those  occupying  the  axis  of 
the  organule  are  the  gustative  cells ;  they  are  in  communication  with  the  nerve- 
tubes  on  one  side,  and  on  the  other  are  furnished,  for  the  most  part,  with  rods 
which  attain  the  free  surface  of  the  tongue.  The  superficial,  or  protective  cells, 
completely  envelop  the  preceding  ;  they  are  a  kind  of  epithelial-cells,  imbricated 
hke  the  skins  of  an  onion. 

These  sensitive  organs  are  very  numerous  in  the  walls  of  the  circumvallate 
papillae,  Schwalbe  reckoned  their  number  at  35,000  in  the  papillas  of  the  Ox. 
(As  many  as  1760  have  been  counted  on  one  circumvallate  papilla  of  the  Ox.  In 
the  papillm  foliatcB  of  the  Rabbit  there  are  from  14,000  to  15,000  taste-bulbs  ;  in  the 
papillae  of  the  Sheep  and  Pig  about  9500).  They  are  not  met  with  in  these  papillae 
only  ;  Lowen  has  found  them  in  a  large  number  of  fungiform  papillae,  if  not  in 
all.  There  is  nothing  extraordinaiy  in  this,  as  the  whole  surface  of  the  tongue 
may,  in  various  degrees,  appreciate  savours.  (Szabadfoldy  has  described  small 
oval  or  pyriform  bodies,  lying  with  their  long  diameter  parallel  to  the  surface. 
The  axis-cylinders  of  the  gustatory  nerves  enter  these,  and  terminate  at  their 
lower  part  in  a  slight  swelling  ;  so  that  they  resemble  small  Paccinian  bodies.) 

Differential  Characters  in  the  Apparatus  of  Taste  in  the  other  Animals. 

In  the  domestic  Manimifera,  the  differences  in  this  apparatus  are  found  in  the  number  and 
variety  of  forms  of  the  papillae  of  the  tongue. 

In  Ruminants,  the  circumvallate  papillae  are  disposed  in  two  rows  at  the  base  of  the 
tongue ;  they  are  smaller  than  in  the  Horse,  but  more  numerous— about  a  dozen  being  counted 
in  each  row.  In  the  Ox,  the  filiform  papillae  are  covered  by  a  homy  sheath,  which  renders 
them  hard  to  the  touch. 

In  the  Camel,  there  are  only  seen  five  or  six  circumvallate  papillae,  surrounded  by  papillsb 
foliatae. 

The  Pig,  like  Solipede,  has  only  two  circumvallate  papillae. 

In  the  Dog  and  Cat,  there  are  two  principal  papillae,  and  in  their  vicinity  some  smaller 
calyces.  The  filiform  papillae  are  composite,  and  covered  by  a  thick  homy  layer.  Between 
them,  regularly  placed,  are  seen  the  fungiform  papillae,  which  have  a  brilliant  aspect  when 
looked  at  obliquely  on  the  surface  of  the  tongue. 

In  the  Rabbit,  the  gustatory  nerve-endings  are  buried  in  special  papillary  organs,  situated 
on  the  limits  of  the  upper  surface  and  sides  of  the  tongue,  near  its  base,  and  named  the  foliated 
organs. 

Comparison  of  the  Apparatus  of  Taste  in  Man  with  that  of  Animals. 

This  has  been  already  alluded  to  at  p.  432. 


CHAPTER  III. 
APPARATUS   OF   SMELL. 

Preparation. — See  directions  for  the  preparation  of  tiie  nasal  cavities. 

The  sense  of  smell  gives  the  appreciation  of  odorous  emanations  to  animals. 
The  active  instruments  of  this  sense  are  the  filaments  of  the  first  pair  of  cranial 
nerves,  which  ramify  in  the  upper  part  of  the  pituitary  membrane  ;  this  becomes. 


TEE  APPARATUS  OF  SMELL.  92$ 

with  the  cavities  it  lines,  the  olfactory  apparatus.   These  parts  having  been  already 
referred  to  at  p.  523,  we  will  pass  to  the  other  senses. 

(The  olfactory  filaments,  passing  down  from  the  olfactory  ganglion,  form  a 
plexus  upon  the  surface  of  the  pituitary  membrane.  These  filaments,  as  already 
noted  (p.  523),  differ  widely  from  those  of  the  ordinary  cranial  nerves,  in  containing 
no  white  substance  of  Schwann,  but  are  nucleated  and  finely  granular  in  structure, 
and  resemble  greatly  the  gelatinous  form  of  nerve-fibres.  Their  distribution  is 
limited  to  the  membrane  at  the  upper  third  of  the  nasal  septum,  the  upper  part 
of  the  turbinated  bones,  and  the  wall  of  the  nasal  cavities  adjoining  the  cribriform 
^late  of  the  ethmoid  bone  ;  all  this  surface  being  covered  with  an  epithelium  of 
a  rich  sepia-brown  hue.  As  has  also  been  mentioned,  Schultze  divides  these  cells 
into  two  sets — supporting  cells  and  olfactory  cells.  The  first  (Fig.  309,  a)  are 
described  as  terminating  externally  by  truncated  flat  surfaces,  which  cannot  be 
observed  to  be  covered  by  any  membrane  separate  from  the  contents  of  the  cell. 
These  contents  appear  to  consist  of  protoplasma  with  a  yellow  granular  aspect 
externally,  wliile  at  the  lower  part  an  oval  nucleus  embedded  in  transparent 
protoplasm  can  be  easily  seen.  At  their  attached  end,  these  cells  become 
attenuated,  and  may  be  traced  inwards  for  a  considerable  distance  until  they 
expand  into  a  broad  flat  sheet  or  plate,  which  is  never  coloured,  though  it 
frequently  presents  a  granular  appearance.  The  processes  passing  off  from  this 
appear  to  be  continuous  with  the  fibres  of  the  submucous  connective  tissue. 
Towards  the  margin  of  the  true  olfactory  region,  cells  perfectly  analogous  to 
these  are  met  with,  the  only  difference  being  that  they  present  a  well-defined 
band  or  seam  at  their  free  extremity,  which  is  surrounded  by  a  circle  of  ciha 
{Fig.  309,  c).  The  cells  of  the  second  set  (Fig.  309,  b)  are  continuations  of  the 
nerves,  and  have  been  named  olfactory  cells.  They  are  thin,  fibrous,  or  rod-like 
bodies,  terminating  at  the  same  level  as  the  proper  epithelial  cells,  and  presenting, 
when  traced  inwards,  a  series  of  varicose  swellings  directly  continuous  with  the 
prolongations  of  deeper-seated  nerve-cells.  Clarke  states  that  the  nerve-fibres, 
on  reaching  the  base  of  the  epithelial  layer,  divide  into  finer  and  finer  branches, 
to  form  a  network  with  numerous  interspersed  nuclei,  through  which  they  are 
probably  connected  with  the  olfactory  cells  (Fig.  309,/).  The  proper  epithelial 
cylinders  {d,  e)  are  connected  at  their  bases  with  the  septa  formed  of  the  connec- 
tive tissue  belonging  to  the  subepithelial  glandular  layer.) 


CHAPTER   IV. 

APPARATUS   OP   VISION. 

Designed  for  the  perception  of  external  images  rendered  visible  by  the  luminous 
rays,  the  sense  of  sight  depends  upon  the  excitability  of  the  optic  nerve,  the 
terminal  extremity  of  which  is  expanded  as  a  thin  membrane  at  the  back  of 
each  eye.  The  latter  is  a  globular  organ  lodged  in  the  orbital  cavity,  attached 
to  muscles  which  can  move  it  in  various  directions,  and  protected  by  membranous 
and  movable  screens  known  as  the  eyelids,  the  play  of  which  over  the  surface  of 
the  eye  is  facilitated  by  the  lachrymal  fluid ;  this  keeps  their  inner  surface 
constantly  moist. 
61 


926  THE  SENSORY  APPARATUSES. 

The  essejitml  organ  of  vision,  or  glohe  of  the  eye,  will  be  first  described  ;  then, 
Tinder  the  designation  of  the  accessory  portion  of  the  visual  apparatus,  we  will 
notice  the  receptacle  for  this  globe,  or  orbital  cavity ;  the  muscles  that  move  the 
eye  ;  the  protective  membranes,  or  eyelids ;  the  membrana  tiictitans,  or  accessory 
eyelid ;  and,  lastly,  the  lachrymal  apparatus,  which  concurs  in  the  protection  of 
the  ocular  globe  by  the  fluid  it  incessantly  throws  out  upon  its  surface. 

Aeticle  I. — The  Essential  Organ  of  Vision,  or  Ocular  Globe  (Fig.  502). 

Preparaticm. — The  eye  is  removed  ftom  the  orbit,  and  freed  from  the  muscles  and  fat  on  it» 
posterior  surface.  Its  membranes  may  then  be  dissected  by  means  of  delicate  instruments,  and 
an  idea  formed  of  the  structure  of  the  eye.  But  in  order  to  study  the  form  and  relations  of  the 
diflFerent  membranes  and  media  of  the  eye,  the  globe  should  be  hardened  in  gradually  con- 
centrated solutions  of  chromic  acid.  When  it  is  so  hardened,  sections  can  be  made  in  every 
direction,  at  any  distance  from  the  axes,  as  the  shell  of  the  eye  does  not  become  deformed.  It 
it  is  very  easy  to  study  the  organization  of  the  eye  on  such  preparations. 

The  globe,  or  ball  of  the  eye,  is  a  spherical  shell,  the  interior  of  which  is  filled 
with  fluid  or  semifluid  parts,  named  the  humours  or  media  of  the  eye.  The  wall 
of  this  shell  {tunica  externa)  is  formed  of  a  continuous,  very  resisting,  colourless 
envelope,  limpid  and  translucid  in  its  anterior  portion,  which  constitutes  the 
transparmt  cornea ;  and  white  and  opaque  for  the  remainder  of  its  extent.  It  is 
known  as  the  sclerotica. 

On  the  inner  face  of  the  sclerotica  is  a  second  tunic  (tunica  media) — the 
choroid :  a  black  membrane  that  lines  the  posterior  face  of  the  retina  {tunica 
interna),  and  which,  near  where  the  two  constituent  portions  of  the  external 
envelope  unite,  throws  into  the  interior  of  the  eye  an  elliptical  diaphragm  with 
a  large  opening  in  its  centre — the  iris.  Immediately  behind  this  disc  is  suspended 
or  set,  like  a  rose-brilliant,  in  the  centre  of  a  circular  zone  depending  from  the 
choroid,  a  biconvex  body — the  crystcdline  lens,  one  of  the  media  of  the  eye,  and 
which  divides  the  interior  of  its  cavity  into  two  compartments  :  a  posterior,  very 
laro-e,  occupied  by  the  vitreous  humour  ,•  and  an  anterior,  itself  divided  by  the 
iris  into  two  chambers  of  unequal  dimensions,  which  contains  the  aqueous 
humour. 

Viewed  externally,  and  as  a  whole,  the  organ  resulting  from  the  union  of  all 
these  parts  represents  a  globular  body,  the  anterior  region  of  which  corresponds 
to  the  cornea,  and  is  more  convex  than  the  other  points  :  a  circumstance  that 
tends  to  increase  the  antero-posterior  diameter  of  the  eye.  But  as  this  ocular 
sphere— to  which  is  added,  in  front,  this  segment  of  a  smaller  sphere— is  sensibly 
depressed  from  before  to  behind,  it  results  that  the  other  two  principal  diametere 

the  vertical  and  transversal — offer  about  the  same  dimensions  as  the  first; 

Girard  has  even  stated  that  the  latter  is  the  least.  With  an  eye  hardened  by 
chromic  acid,  we  have  found  that  the  transverse  diameter  measured  0-036  m.,  and 
the  vertical  0-040  m.  (1-417  X  1-575). 

Two  paragraphs  will  be  devoted  to  the  description  of  the  constituent  parts  of 
the  globe — one  for  the  membranes,  the  other  for  the  ynedia. 

The  membranes  (or  tunics)  of  the  eye  are  of  three  kinds.  Two  are  exclusively 
fibrous,  and  form  the  framework  ;  these  are  the  sclerotica  and  cornea.  The  second 
is  characterized  by  the  association  in  its  interior  of  the  contractile  element  and 
of  vessels;  and  the  third  is  represented  by  the  retina,  which  is  nervous  in 
structure. 


TEE  GLOBE  OF  THE  EYE. 


927 


The  Membranes  of  the  Eye. 

A.  FiBKOus  Membranes. 
1.  The  Sclerotic  (Fig.  502,  h). 

The  sclerotic  is  a  white,  very  solid  membrane,  forming  in  itself  about  four- 
fifths  of  the  external  shell  of  the  eye. 

Its  external  face.,  in  relation  with  the  recti  muscles  and  adipose  tissue,  receives 
posteriorly — though  lower  than  the  middle — the  insertion  of  the  optic  nerve, 

Fig.  502. 


THEORETICAL   SECTION    OF   THE    HORSE  S   EYE 

1,  Orbital  arch  ;  2,  lachrymal  gland,  a,  Optic  nerve ;  6,  sclerotic ;  c,  choroid  ;  d,  rptina;  e,  cornea, 
/  /,  iris ;  ^,  A,  ciliary  ligament  and  processes  given  off  by  the  choroid,  though  represented  as 
isolated  from  it,  in  order  to  indicate  their  limits  more  clearly;  i,  insertion  of  the  ciliary  processes 
on  the  capsule  of  the  crystalline  lens  ;  jy  crystalline  lens ;  k,  crystalline  capsule  ;  I,  vitreous 
humour ;  ?«,  n,  anterior  and  posterior  chambers ;  o,  theoretical  indication  of  the  membrane  of 
the  aqueous  humour ;  p,  p,  tarsi  ;  q  q,  fibrous  membrane  of  the  eyelids ;  r,  elevator  muscle  of 
the  upper  eyelid;  s  s,  orbicularis  muscle  of  the  eyelids;  t  t,  skin  of  the  eyelids;  u,  conjunctiva; 
V,  epidermic  layer  of  this  membrane  covering  the  cornea  ;  x,  posterior  rectus  muscle  ;  y,  superior 
rectus  muscle;  z,  inferior  rectus  muscle;  w,  fibrous  sheath  of  the  orbit  (or  orbital  membrane). 


which  passes  through  it  and  the  choroid  to  form  the  retina.  Its  internal  face  is 
loosely  united  to  the  choroid  by  vessels,  nerves,  and  connective  tissue. 

In  front,  the  sclerotic  shows  an  elliptical  opening,  the  greatest  diameter  of 
which  is  transversal,  while  its  border — bevelled  on  the  inner  side — is  closely 
united  to  the  circumference  of  the  cornea.  The  substance  of  this  membrane  is 
traversed  by  numerous  vessels  ^and  nerves,  and  is  not  of  the  same  thickness 
throughout ;  at  the  back,  around  the  entrance  of  the  optic  nerve,  it  is  thickest ; 
it  then  diminishes  gradually  towards  the  larger  axis  of  the  organ,  and  afterwards 
increases  until  it  meets  the  cornea. 

Structure. — The  sclerotic  is  wholly  composed  of  fasciculi  of  connective 


928  THE  SENSORY  APPARATUSES. 

tissue  interwoven  in  a  very  close  manner,  with  some  elastic  fibres  and  little  masses 
of  pigment  between,  especially  at  its  posterior  part.  Among  these  fasciculi,  a 
large  number  pass  from  before  to  behind,  and  these  are  intersected  by  others 
which  are  placed  in  a  circular  manner  around  the  globe.  The  superficial  fibres 
are  continuous  with  the  neurilemma  of  the  optic  nerve.  (Delicate  elastic  fibres 
are  mixed  with  the  others,  and  in  the  lacunae  of  the  network  are  some  connective 
tissue  corpuscles.  Between  the  choroid  and  sclerotica  is  loose  connective  tissue 
containing  numerous  elastic  fibres,  and  branched  pigment-cells  and  non-pigmented 
fiat  endothelial  cells  ;  this  forms  the  lamina  supra-choroidea,  or  lamina  fusca 
sclera.  The  optic  nerve,  at  its  entrance  into  the  sclerotic,  is  very  much  con- 
stricted, and  passes  through  a  funnel-shaped,  porous  mesh  of  fibrous  tissue 
named  the  lamina  cribrosa,  in  the  centre  of  which  is  a  larger  opening  than  the 
others,  for  the  passage  of  the  arteria  centralis  retinae — the  pones  opticus.) 

The  arteries  of  the  sclerotic  are  derived  from  the  anterior  and  posterior 
ciliary  arteries ;  the  veins  pass  into  trunks  lying  parallel  to  the  ciliary  arteries. 
Nerves  have  been  found  in  the  sclerotic  of  the  Rabbit,  but  Leydig  could  not  find 
any  in  the  Calf.  Lecoq  has  remarked  that  in  the  Ass,  particularly  when  it  is 
old,  the  back  part  of  the  sclerotic  is  encrusted  with  an  unmistakable  layer  of 
bony  matter.  (In  Birds,  bony  plates  are  found  in  this  region,  and  some  Reptiles 
also  have  them.) 

2.  The  Coknea  (Fig.  502,  e). 

(Preparation. — The  cornea  should  be  removed  with  the  sclerotic  coat,  by  immersing  the 
eye  under  water,  and  making  a  circular  incision  with  scissors  about  a  quarter  of  an  inch  from 
the  margin  of  the  membrane.) 

The  cornea  is  a  transparent  membrane  forming  the  anterior  part  of  the  eye, 
to  the  interior  of  which  it  allows  the  light  to  pass.  It  closes  the  anterior  opening 
of  the  sclerotic,  and  thus  completes  the  external  envelope  or  shell  of  the  globe,  of 
which  it  forms  about  a  fifth  part. 

Elliptical— like  the  opening  it  closes — the  cornea  presents  :  1.  Two  faces, 
perfectly  smooth — one  external,  convex ;  the  other  internal — concave,  forming 
the  external  wall  of  the  anterior  chamber,  2.  A  circumference,  bevelled  on  its 
outer  edge,  and  received  into  a  similar  bevel  around  the  sclerotic  opening,  like 
the  glass  of  a  watch  into  its  case. 

Structure. — Three  layers  enter  iuto  the  composition  of  the  cornea — an 
external,  internal,  and  middle. 

Middle  layer. — This,  the  proper  cornea,  is  remarkable  for  its  thickness.  When 
pressed  between  the  fingers,  its  two  faces  can  be  easily  made  to  glide  over  each 
other — a  proof  that  its  tissue  is  disposed  in  superposed  and  parallel  planes  ;  it  is 
indeed  possible  to  decompose  the  cornea  into  several  lamina  and  laminellae. 
These  layers  are  formed  by  chondrigenous  amorphous  matter  and  connective 
fibrillse,  which  may  be  disassociated  by  pyrogallic  acid.  They  are  perforated  by 
more  or  less  irregular  openings,  and  lacunae  (spaces  of  Fontana)  occupied  by  cells, 
the  prolongations  of  which  anastomose  through  these  slits.  The  cornea  contains 
in  its  substance  a  regular  network  of  stellate  cells,  and  of  migratory  cells  wander- 
ing through  the  slits  and  in  the  lacunae.  Lecoq  a  long  time  ago  remarked  that 
this  layer  became  opaque  when  the  eye  was  strongly  squeezed,  and  attributed 
this  change  to  expression  of  the  fluid  it  contained.  Dubois  has  observed  the 
same  opacity  in  the  cornea  of  the  Dog,  as  a  consequence  of  ansesthesia  by  chloride 
of  ethylene. 


,THE  GLOBE  OF  TEE  EYE.  929 

In  the  normal  condition,  the  transparency  of  the  cornea  results  from  the 
equal  refraction  of  the  connective  tissue  fibrillae,  and  the  chondrigenous  substance 
surrounding  them. 

The  external  layer  is  only  the  conjunctival  epithelium  spread  over  the  anterior 
face  of  the  cornea.  This  epithelium  in  the  Horse  measures  '014  mm.  in  thick- 
ness ;  it  is  stratified,  flattened  on  its  surface,  but  cyhndrical  below,  where  it 
rests  on  the  middle  layer,  and  from  which  it  is  not  separated — as  in  many  other 
species  of  animals — by  a  proper  limitary  membrane. 

The  m?ier  layer  is  a  portion  of  the  membrane  of  the  aqueous  humour.  It  is 
composed  of  :  1.  A  hmitary  membrane — the  posterior  elastic  lamina  (or  nmnbrane 
of  Descemet) — •002  mm.  in  thickness,  which  becomes  slightly  fibrous  at  the  peri- 
phery of  the  cornea,  where  it  forms,  in  passing  on  to  the  iris,  the  pectinated 
ligament.  2.  A  lining  of  polygonal  (flat)  epithelial  cells  {endothelium),  which 
are  provided  with  a  large  nucleus. 

(Some  authorities  give  five  layers  to  the  cornea,  the  first  being  the  corneal 
epitheUum,  and  the  second  the  anterior  elastic  lamina,  or  Boivmaii's  membrane. 
The  third  consists  of  a  very  elastic  tissue,  perfectly  structureless,  and  possessing 
a  remarkable  tendency  to  curl  up  ;  but  boiling,  or  the  action  of  acids,  does  not 
render  it  opaque,  as  with  the  other  layers.  Very  fine  fibres— ;^&roe  arcuatoe — pass 
obliquely  between  it  and  the  next  layer — the  substantia  propria,  or  cornea  proper 
— consisting  of  a  large  number  of  strata  with  branched  fusiform  cells.  The  fourth 
layer  is  the  posterior  elastic  lamina ;  and  the  fifth  layer  consists  of  the  epithelial 
cells  already  mentioned.) 

Vessels. — The  cornea  has  Httle  vascularity  in  the  adult.  The  vessels  form 
loops  around  its  borders,  but  in  the  foetus  they  advance  to  near  its  centre. 

Nerves. — These  were  discovered  by  Schlemm.  They  penetrate  by  the  peri- 
phery of  the  cornea,  and  form  a  network  on  its  surface.  According  to  Kiihne, 
Hoyer,  Conheim,  and  Poncet,  the  ultimate  nerve-ramifications  pass  into  the 
epithelium  on  the  anterioir  surface,  and  arrive  between  the  most  superficial  cells. 

(The  nerves  of  the  eyeball  perforate  the  sclerotic  in  the  region  of  the 
optic  nerve,  and  run  between  it  and  the  choroid  anteriorly.  During  their 
course,  they  give  off  branches  provided  with  ganglion  cells,  to  the  choroid,  and, 
finally,  they  form  a  ring-like  plexus  in  the  ciliary  region,  termed  the  orbiculus 
gangliosus  ciliaris.  From  this  plexus  branches  go  to  the  ciHary  muscle,  the  iris, 
and  the  cornea.  The  nerves  for  the  cornea  pass  first  into  the  sclerotic,  and  form 
a  plexus  round  the  margin  of  the  cornea — the  plexus  cmtmlaris — from  which 
branches  run  into  the  conjunctiva  and  the  cornea.  The  fibres  entering  the 
substance  of  the  cornea  lose  their  white  substance,  and  run  on  as  naked  axis- 
cylinders  to  form  networks  in  the  different  layers.) 

B.  Musculo-Vascular  Membranes. 
3.  The  Choroid  Coat  (Figs.  502,  c ;  503). 

(Preparation. — If  the  cornea  has  not  yet  been  removed,  it  and  the  sclerotic  may  now  be 
dissected  away  from  the  choroid  or  second  tunic.  The  connections  between  them  are  closeet 
at  the  circumference  of  the  iris,  and  at  the  entrance  of  the  optic  and  ciliary  nerves  and  arteries. 
Fine  blnnt-pointed  scissors  are  necessary.  A  small  portion  of  the  sclerotic,  near  its  anterior 
circumference,  is  pinched  up  and  clipped  off,  the  edge  of  the  incision  is  raised,  the  circum- 
ference of  the  sclerotic  divided,  and  that  tunic  removed  piecemeal ;  a  gentle  pressure  with  the 
edge  of  the  knife  will  remove  it  from  its  attachments  around  tlie  circumference  of  the  iris. 
This  dissection  is  best  conducted  under  water.  The  ciliary  nerves  and  long  ciliary  arteries 
will  be  seen  passing  forward,  between  the  sclerotic  and  choroid,  to  the  iris.) 


930  THE  SENSORY  APPARATUSES. 

The  choroid  is  a  thin,  dark-coloured  membrane  spread  over  the  inner  face  of 
the  sclerotic,  the  general  conformation  of  which  it  repeats.  It  is  divided  into 
two  zones  by  the  ora  serrata — a  denticulated  line  which  corresponds  to  the  point 
where  the  retina  changes  its  characters. 

Posterior  or  choroid  zone. — Throughout  the  whole  of  this  zone  the  choroid  is 
uniformly  thin,  and  corresponds,  by  its  externa}  face  {superjicial  layer,  or  stratum 
of  the  larger  vessels),  with  the  sclerotic  ;  by  its  interned  face,  it  is  in  contact  with 
the  retina,  but  does  not  adhere  to  it.  Posteriorly,  it  shows  an  opening  through 
which  the  optic  nerve  passes.  In  front,  at  the  anterior  opening  of  the  sclerotic, 
it  is  continuous  with  the  anterior  zone. 

The  inner  face  (or  lai/er — the  membrana-chorio-capillaris)  of  the  choroid  is 
not  uniform  in  colour,  being  perfectly  black  in  the  lower  part  of  the  eye  ;  this 
is  abruptly  terminated  at  a  horizontal  line  that  passes  about  the  eighth  or  ninth 
part  of  an  inch  above  the  optic  papilla.  From  this  line,  on  the  segment  of  a 
circle  from  f  to  f  of  an  inch  in  height,  it  shows  most  brilliant  colours — at  first 
blue,  then  an  azure-blue,  afterwards  a  brownish  blue,  and  beyond  this  an  intense 
black.     The  bright  portion  is  the  tapetum  {lucidwn,  or  tapetum  fibrosiim). 

The  background  of  the  colour  is  green  with  bluish  shades,  that  vary  slightly 
according  to  the  tint  of  the  animal's  coat.  In  black  or  dark  grey  Horses,  the 
tapetum  has  a  deeper  blue  tint  than  in  others  ;  and  in  white  Horees  it  is  some- 
times yellowish  brown. 

(This  beautiful  iridescent  layer  is  composed  of  numerous  undulating  bundles 
of  connective  tissue,  contained  in  another  layer  of  fine  elastic  fibres — the  houndary 
stratum  of  the  ground  substance — placed  between  the  two  layers  of  the  choroid.) 

Anterior  or  ciliary  zone. — This  includes  two  parts— the  "  ciliary  muscle " 
and  the  "  ciliary  body."  The  ciliary  muscle  {annulus  albidus,  or  musculus 
ciliaris)  varies  in  width  from  one  to  two  millimetres  ;  its  external  face  adheres 
closely  to  the  sclerotic,  and  its  internal  is  continuous  with  the  ciliary  body  ;  the 
posterior  border  is  continuous  with  the  choroid  zone,  near  the  canal  of  Fontana, 
The  anterior  border  gives  attachment  to  the  greater  circumference  of  the  iris. 
Its  structure  and  uses  will  be  referred  to  hereafter. 

The  ciliary  body  {corpus  ciliare)  forms  a  kind  of  zone  or  ring,  wider  than  the 
ciliary  muscle,  and  consequently  overlaps  the  latter  before  and  behind.  It 
extends,  on  one  side,  on  the  inner  face  of  the  choroid,  and  on  the  other,  on  the 
posterior  face  of  the  iris.  When  the  cornea  and  sclerotic  are  removed  so  as  to 
expose  the  ciliary  muscle,  this  zone  is  not  seen  ;  and  to  discover  it,  it  is  necessary 
to  excise  all  the  posterior  part  of  the  shell  of  the  eye  by  a  circular  incision,  and 
evacuate  the  vitreous  humour.  We  then  observe,  around  the  crystalline  lens, 
a  wide,  black  circle,  forming  very  regular  radiating  folds,  projecting  inwards  by 
their  inner  extremities,  and  appearing  in  the  posterior  chamber  of  the  eye,  after 
cutting  away  the  iris  ;  all  abut  by  these  extremities  on  the  circumference  of  the 
lens,  which  they  do  not  quite  reach,  although  the  latter  is  sustained  by,  and 
"  set "  in,  the  centre  of  the  ciliary  body. 

These  radiating  folds,  named  the  ciliary  processes  (Fig.  503,  4),  are  from 
110  to  120  in  number  in  the  Horse,  and  are  constituted  by  little  parallel  leaves, 
wider  at  their  inner  than  their  outer  extremity  ;  the  furrows  that  separate  them 
posteriorly  are  partly  concealed  by  the  prolongation  of  the  retina  that  constitutes 
the  zonula  of  Zinn.  The  coronet  formed  by  the  ciliary  processes  is  usually 
asymmetrical — that  is,  narrower  on  the  inner  than  on  the  outer  side. 

(The  elements  of  the  ciliary  muscle  run  in  three  directions  :  1.  Meridional 


THE  GLOBE  OF  THE  EYE. 


931 


Fig.  503. 


fibres — numerous  bundles  near  the  sclerotic,  and  extending  to  the  choroid, 
forming  the  tensor  choroideoe.  2.  Radial  fibres,  next  the  meridional,  radiating 
towards  the  centre  of  the  eye.  3.  Circular  or  equatorial  fibres,  constituting  the 
sphincter  or  ciliary  muscle  of  Miiller. 

The  ciliary  muscle  originates  on  the  inner  wall  of  a  minute  circular  canal — • 
named  the  ciliary  canal,  canal  of  Schlemm,  sinus 
circularis  iridis,  circulus  venosus  orbicuU  ciliaris, 
or  camd  of  Fontana,  from  its  discoverer.  It  is 
surmised  to  be  a  venous  sinus,  as  it  can  always 
be  injected  from  the  arteries.) 

Structure. — The  choroid  zone  is  composed 
of  four  superposed  layers  :  1.  The  external  is 
formed  by  a  network  of  connective  elastic 
fibres,  among  which  are  disseminated  a  great 
number  of  pigment-cells.  2.  The  second  layer  is 
constituted  by  a  network  of  large  arteries  and 
veins — the  posterior  ciliary — and  a  plexus  of 
nerves  (ciliary)  accompanied  by  ganglia  and 
some  (stellate)  pigment-cells.  (The  veins  are 
arranged  with  great  regularity  in  drooping 
branches,  to  form  the  vasa  vorticosa — Fig.  505, 
2,  4  ;  these  are  chiefly  on  the  outer  surface  of 
the  layer,  the  arteries  ramifying  on  the  inner 
surface.)  The  veins  open  into  the  ophthalmic 
vein.  3.  The  third  layer,  or  tunica  Ruyschiana, 
has  for  its  basis  an  amorphous  substance  con- 
taining a  network  of  exceedingly  fine  capillaries 

(extending  to  the  ciliary  processes).  4.  The  interned  layer  is  composed  of  hexagonal 
cells,  regularly  placed  one  upon  the  other  on  the  surface  of  a  limitary  membrane  ; 
the  cells  are  provided  with  a  nucleus,  and  contain  pigment-granules  which  ex- 
clusively occupy  their  anterior  moiety.  (On  the  choroid 
this  cell-formation  is  single,  but  on  the  iris  and  ciliary 
processes  there  are  several  layers.  A  very  delicate  mem- 
brane— membrane  of  Bruch,  or  vitreous  membrane — has 
been  described  as  lining  the  inner  surface  of  the  choroid, 
and  retaining  the  pigment  in  its  place  ;  this  membrane 
may  be  seen  on  the  posterior  surface  of  the  iris,  and  it 
probably  prevents  the  pigment  being  removed  by  the 
aqueous  humour.)  The  use  of  the  choroid  membrane 
is  to  convert  the  ocular  globe  into  a  veritable  darkened 
chamber,  and  to  constitute  for  the  retina  a  calefactory 
apparatus.  (The  pigment  absorbs  the  rays  of  light  which 
pass  through  the  retina,  and  thus  prevents  their  becoming 
reflected  and  confusing  the  vision.  The  brilliant  metallic- 
coloured  layer  named  the  tapetum  is  more  particularly 

observed  in  nocturnal  animals,  and  especially  in  the  Carnivora.  By  reflecting 
the  rays  of  light  a  second  time  through  the  retina,  it  probably  enables  the  animal 
to  see  better  at  night.  It  is  the  cause  of  the  glare  perceived  in  the  eyes  of 
Cats  and  other  creatures,  in  the  dark.) 

The  ciliary  circle  is  a  contractile  body,  being  composed  of  unstriped  musculai 


ANTERIOR  SEGMENT  OF  A  TRANSVERSE 
SECTION  OF  THE  GLOBE  OF  THE  EVE 
(human),  SEEN  FROM  WITHIN. 

I,  Divided  edge  of  the  three  tunics — 
sclerotic,  choroid  (the  dark  layer), 
and  retina ;  2,  pupil ;  3,  iris  (the 
uvea)  ;  4,  ciliary  processes  ;  5,  den- 
ticulated anterior  border  of  the 
retina. 


Fig.  504. 


CELLS  FROM   THE  CHOROID 
COAT. 

a,  Pigmentary  granules 
concealing  the  nucleus  ; 
6,  the  nucleus  distinct. 


TEE  SENSORY  APPARATUSES. 


fibres  which  are  arranged  in  orbicular  fasciculi,  or  extend  backwards  (and  are 
lost  in  the  choroid,  behind  the  ciliary  processes).  These  fibres  are  mixed  in  the 
plexus  of  ciliary  nerves,  on  the  track  of  which  small  ganglia  are  formed.  By  its. 
contractions,  the  ciliary  circle  (or  muscle)  plays  an  important  part  in  accommo- 
dating the  eye  to  the  perception  of  objects  at  different  distances.  (In  Birds,  the 
muscular  fibres  are  striped.) 

The  ciliary  body  ox  processes  are  formed  by  intercrossed  fasciculi  of  (fibrillated) 
connective  tissue,  vessels,  and  some  unstriped  muscular  fibres ;  their  inner 
surface  is  covered  by  pigment,  like  that  of  the  choroid  zone. 

4.  The  Ieis  (Figs.  502,/";  505,  6). 

The  iris  forms  in  the  interior  of  the  eye — at  the  anterior  opening  of  the 
sclerotic,  and  in  front  of  the  crystalline  lens — a  veritable  diaphragm  pierced  with 
a  central  opening — the  pupil — which  contracts  or  dilates  according  to  the 
intensity  of  the  light  and  the  distance  of  the  objects  to  which  the  vision  i& 

Fig.  505. 


THE   EYE    (human)    WITH   THE    SCLEROTIC  COAT   REMOVED. 

1,  Sclerotic  coat ;  2,  veins  of  the  choroid  ;  3,  ciliary  nerves  ;  4,  veins  of  the  choroid,  or  vena 
vorticosa  ;  5,  ciliary  ligament ;  6,  iris. 

directed.  This  diaphragm  divides  the  space  between  the  cornea  and  the  anterior- 
face  of  the  lens,  and  internal  extremities  of  the  ciliary  processes,  into  two- 
compartments  or  chambers  of  unequal  size  ;  the  anterior  space  is  the  largest,  the 
posterior  having  only  a  virtual  existence,  as  the  iris  is  close  to  the  crystalline  lens. 

In  shape,  the  iris  is  elliptical,  like  the  cornea  and  the  sclerotic  aperture. 

Its  anterior  face  is  flat  or  very  slightly  convex,  and  has  very  marked  circular 
furrows  and  radiating  striae,  noticeable  only  at  the  outer  circumference  of  the 
membrane.  It  is  diversely  coloured,  not  only  according  to  species,  but  also  in 
individuals.  In  Solipeds,  it  has  nearly  always  a  brownish  yellow  tint ;  though 
sometimes  it  is  nearly  white  or  bright  grey,  when  the  animal  is  said  to  be  "  wall- 
eyed." 

The  posterior  face,  in  relation  with  the  lens  and  ciliary  processes,  is  covered 
by  a  very  thick  layer  of  pigment  named  the  uvea.  Portions  of  this  pigment, 
supported  by  a  small  pedicle,  frequently  pass  through  the  pupillary  aperture  and 
appear  in  the  anterior  chamber  of  the  eye,  where  they  are  known  as  "  soot-balls,"' 
or  corpora  nigra.     (There  are  frequently  several  of  these  black  spongy  masses^ 


TEE  GLOBE  OF  THE  EYE. 


•which  are  generally  attached  to  the  upper  border  of  the  pupil  ;  on  the  lower 
margin,  when  present,  they  are  much  smaller.  Their  colour  is  a  brownish  black. 
They  are  sometimes  so  large  as  to  give  rise  to  apprehensions  of  injury  to  the 
vision.) 

The  larger  circumference  of  the  iris  is  attached  to  the  ciliary  muscle,  which 
unites  it  to  the  choroid  ;  it  is  also  related  to  the  margin  of  the  cornea,  as  well  as 
to  that  of  the  sclerotic  opening. 

The  lesser,  or  internal  circumference,  is  elliptical,  and  circumscribes  the 
pupillary  opening. 

Structure. — The  organization  of  the  iris  has  been  much  discussed  ;  but  at 
present  it  is  admitted  that  its  principal  element  is  unsfcriped  muscular  fibre.  A 
proper  membrane  and  two  epithelial  layers  enter  into  its  formation. 

The  proper  membrane  has,  for  its  framework,  circular  or  radiating  fasciculi  of 
wavy  connective  tissue,  with  pigment- 

•cells.    Between  the  fasciculi  are  placed  f'g-  5^^- 

the  unstriped  fibres  ;  these  are  disposed 
in  a  circular  manner  around  the  pupil 
to  constitute  the pupiUary  sphincter,  and 
■others  radiate  from  the  lesser  circum- 
ference towards  the  ciliary  ligament  to 
form  the  dilator  of  the  pupil.  Very  fine 
radiating  vessels  are  disseminated  among 
these  fibres,  and  pass  to  the  anterior 
ciliary  trunks.  The  nerves  supplied  to 
the  iris  are  from  the  ophthalmic  gang- 
lion— which  has  afferent  nerves  from 
the  ophthalmic  nerve  of  Willis — the 
common  oculo-motor  nerve,  and  the 
■sympathetic.  These  nerves  regulate 
the  reflex  movements  of  contraction 
and  dilatation  of  the  pupil. 

(Behind  the  proper  membrane  has 
teen  described  a  clear,  homogeneous  one, 
■composed  of  dense  elastic  substance.) 

The  anterior  epithelial  layer  is  composed  of  the  polygonal  cells  of  the  aqueous- 
humour  membrane,  already  described  as  existing  on  the  posterior  surface  of  the 
•cornea. 

The  posterior  epithelial  layer,  or  urea,  is  constituted  by  pigment-cells  analogous 
to  those  of  the  choroid,  but  less  regular  in  shape.  (This  pigmentary  stratum — 
or  pars  iridica  retincB — in  addition  to  the  cells,  has  a  fine  covering — the  limitans 
iridis — the  continuation  of  the  limitans  interna  retince.) 

In  the  foetus,  the  pupil  is  closed  by  a  very  thin  transparent  membrane — the 
membrana  pupillaris.  (It  is  identical  with  the  anterior  layer  of  the  capsule  of 
the  crystalline  lens.) 

^  C.  Nerve-Membrane. 

5.  The  Retina  (Figs.  502,  d;  507  ;  508). 

(Preparation. — The  choroid  must  be  removed  under  water  by  means  of  forceps  and  scissors, 
after  the  lens  and  vitreous  humour  have  been  evacuated.  A  good  view  of  the  retina  is  to  be  had 
hy  looking  through  the  vitreous  humour,  after  the  lens  and  iris  have  been  excised  from  an  eye.) 


MUSCPLAR   STRUCTURE   OF   THE   IRIS   OF   A 
WHITE    RABBIT. 

Sphincter  of  the  pupil ;  6,  b,  radiating  fasciculi 
of  dilator  muscle ;  c,  c,  connective  tissue,  with 
its  corpuscles. 


984  TEE  SENSORY  APPARATUSES. 

The  retina,  the  essential  portion  of  the  eye — considered  as  the  terminal 
expansion  of  the  optic  nerve — extends  over  the  internal  face  of  the  choroid, 
from  which  it  is  easily  separated,  and  lies  between  that  membrane  and  the 
vitreous  humour.  On  arriving  at  the  cihary  body,  it  is  exactly  moulded  on 
the  radiating  folds  of  its  posterior  face,  and  with  them  is  prolonged  to  the 
circumference  of  the  crystalline  lens,  on  the  capsule  of  which  it  appears  to 
become  lost,  after  being  closely  united  to  it.  It  also  adheres  so  firmly  to  the 
ciliary  processes  that,  in  the  fresh  eye,  it  is  impossible  to  detach  it.  When  the 
eye  has  been  kept  some  time,  however,  the  two  are  easily  separated  ;  the  cornea 
is  removed  with  a  portion  of  the  sclerotic  ;  then,  dividing  the  iris  into  several 
pieces  by  diverging  incisions,  each  is  turned  outwards  by  a  slight  traction  that 
ruptures  the  ciliary  zone  and  the  choroid.  The  retina,  being  thus  divested  of 
the  parts  which  cover  it  anteriorly,  is  seen  to  form  around  the  lens  a  kind  of 
Elizabethan  ruff,  dovetailing  with  the  ciliary  processes.  This  plaited  collar  ha& 
been  named  the  zonula  of  Zi?in  {zonula  ciliaris,  and  ora  serrafa).  This  zonula — 
the  origin  of  which  has  been  so  much  discussed — probably  belongs  to  the  vitreous 
humour. 

At  the  point  where  the  optic  nerve  enters  the  eye,  there  is  found  on  the 
retina  a  small  oval  elevation,  the  larger  axis  of  which  is  about  ^  inch  ;  this  little 
prominence  is  the  optic  papilla,  or  punctum  ccecum  {papilla  conica).  From  its 
centre  emerge  the  vessels  of  the  retina. 

At  some  distance  above  the  punctum  cmcum — on  the  antero-posterior  axis  of 
the  eye — is  the  yellow  spot  {macula  lutea),  in  the  centre  of  which  is  an  oval 
depression — ila.Q  fovea  centralis.    This  region  is  the  most  sensitive  part  of  the  retina. 

Structuee. — The  retina  is  the  most  important  of  the  three  tunics  of  the 
eye,  and  it  is  also  the  thinnest  and  most  delicate.  It  forms  a  soft,  pulpy, 
transparent  expansion  when  quite  fresh,  but  becomes  white  and  opalescent  soon 
after  death.  Boll  has  discovered  that,  during  life,  the  retina  becomes  purple 
in  the  dark,  but  regains  its  normal  tint  when  again  exposed  to  light.  This 
coloration  resides  in  the  inner  segment  of  the  rod  portion.  Kiihne  has  observed 
that  the  modification  in  the  retinal  purple  also  occurs  when  the  eye  is  extirpated. 
The  author  has  obtained  permanent  pictures  of  luminous  objects  on  the  retina  in 
treating  it  with  a  5  per  cent,  solution  of  alum.  The  retina-red  is  regenerated  at  the 
expense  of  the  oil  drops  between  the  pigmentary  layer  and  the  retina.  Capranica 
studied  the  chemical  and  spectroscopic  characters  of  these  drops  in  1876-77. 

The  retina  is  composed  of  connective  tissue  and  nerve-elements,  which  are 
arranged  to  form  nine  or  ten  superposed  layers. 

Connective  Tissue. — This  is  very  delicate  and  nucleated,  and  forms  two 
thin  layers,  named  the  external  and  internal  limitary  memhranes ;  these  are 
connected  by  radiating  fibres  which  pass  through  the  nerve-elements,  and 
anastomose  very  closely  in  the  molecular  layer. 

Nerve-elements. — These  are  distributed  in  seven  layers,  which  present 
the  following  characters  : — 

1.  Layer  of  rods  and  cones  (Fig.  507,  1). — This  is  also  termed  the  memhrana 
JacoU  {hacillary  or  columnar  layer).  It  is  situated  between  the  inner  face  of 
the  choroid  and  the  external  limitary  membrane. 

Rods  and  cones,  regularly  mixed,  make  up  its  structure.  Each  of  these 
comprises  two  portions  or  segments  (separated  by  a  bright  transverse  line).  The 
outer  segment  (or  shaft)  is  brilliant  and  refractive,  and  consists  of  a  small  stalk 
terminating  in  a  point  for  the  cones  :  with  a  shorter  stalk  than  the  inner  seyment 


THE  GLOBE  OF  THE  EYE. 


985 


2.  External  granular 

Fig.  507. 


between  the  external 

Fig.  508. 


for  the  latter,  and  equal  in  length  to  this  segment  for  the  rods.  The  inner  seg- 
ment is  a  small  granular  shaft  for  the  rods,  and  an  enlargement,  the  base  of 
which  is  towards  the  centre  of  the  eye  for  the  cones.  The  elements  of  this  layer 
quickly  alter  after  death 

layer  (2). — This  is  comprised 
limitary  and  the  intermedi- 
ate membrane.  It  is  formed 
by  the  granules  of  the  cones 
and  those  of  the  rods — small 
cells  with  an  oval  nucleus 
{vision  cells),  furnished  with 
an  external  prolongation 
that  joins  them  to  the  base 
of  the  cones  and  rods,  and 
an  external  varicose  prolon- 
gation which  often  enlarges 
on  arriving  at  the  inter- 
mediate layer. 

3.  Intermediate  lager 
(3). — This  is  very  thin,  and 
composed  of  flexuous  fi- 
brillte,  which  are  connected 
with  the  adjoining  elements. 

4.  Inner  granular  layer 
(4). — In  this  we  find  cells, 
the  membrane  of  which  is 
in  immediate  contact  with 
the  nucleus.  These  cells 
have  minute  prolongments 
analogous  to  those  of  the 
external  granular  layer, 
which   connect   them   with 

the  surrounding  layers, 

5.  Molecular  layer   (5). 
layer  (the  grey  vesicular)  presents  a  granulous  aspect ; 
in  its  mass,  the  connective  tissue  forms  a  close  mesh, 
in  the  midst  ot   which  are  seen  fine  fibrillae  passing  in 
every  direction. 

6.  Ganglionic  layer  (6). — This  is  composed  of  a  single 
stratum  of  ramifying  nerve-cells,  the  prolongations  of 
which  pass  into  the  molecular  layer,  where  they  join  the 
filaments  of  the  next  layer. 

7.  Layer   of  the    optic-nerve  fibres   (7).— The   fibres 

(ultimate  fibrils)  of  the  optic  nerve,  in  passing  through  the  sclerotic  and  choroid, 
anastomose  with  each  other,  and  arrange  themselves  in  a  cone  shape,  the  apex 
of  which  corresponds  with  the  papilla  conica  ;  at  this  point  they  suddenly  spread 
out  in  every  direction,  between  the  ganglionic  layer  and  the  internal  limitary 
membrane. 

To  sum  up,  the  retina  comprises  the  following  layers,  reckoning  from  before 
to  behind  :  1.  Internal  limitary  membrane.     2.  Layer  of  optic-nerve  fibres.     3. 


VERTICAL    SECTION    OF    RKTINA. 

I,  Bacillar  layer;  2,  outer  grau- 
ular  layer;  3,  intermediate 
fibrous  layer;  4,  inner  granular 
layer;  5,  finely  granular  grey 
layer;  6,  layer  of  nerve-cells; 

7,  layer  of  fibres  of  optic  nerve; 

8,  limitary  membrane. 


-One  of   the  thickest,  this 


DIAGRAM  OF  THE  STRUC- 
TURE   OF    THE    RETINA. 

p,  Pigment -cell  of  the 
retina  connected  with  a 
rod  ;  n,  cone  seated  on 
the  raembrana  limitans 
externa,  the  inner  seg- 
ment containing  a  cone 
ellipsoid,  and  a  needle  ; 
inf,  proper  fibre  con- 
necting rod  and  cone 
with  one  of  the  cells  of 
the  membrana  fenestra, 
the  cells  of  which  are 
in  communication  with 
the  membrana  limitans 
interna,  mli,  by  means 
of  a  thick  radial  fibre 
with  an  oval  nucleus 
attached ;  gg,  multi- 
polar ganglion  of  nerve- 
elements  ;  op,  optic 
fibrilla;  gri,  supposed 
connectionof  the  nucleus 
with  prolongation  of  a 
ganglion-cell. 


936  TEE  SENSORY  APPARATUSES 

Layer  of  ganglion-cells.  4.  Molecular  layer.  5.  Inner  granular  layer.  6.  In- 
termediate layer.  7.  Outer  granular  layer.  8.  Outer  limitary  membrane.  9. 
Layer  of  rods  and  cones.  10.  Pigmentary  layer  of  the  choroid,  if  this  be  attached 
to  the  retina,  as  Schultze  proposes. 

It  is  to  be  remarked,  that  at  the  ora  serrata  all  the  nerve-elements  of  the 
retina  disappear. 

Pigment  Layer. — This  is  represented  by  a  row  of  cells  spread  on  the  posterior 
face  of  the  rod-and-cone  stratum.     These  cells  have 
F'g-  509.  many  small  prolongations,  which  are  insinuated  be- 

tween the  rods  and  cones,  and  the  elongated  or 
rounded  pigmentary  granules  of  a  more  or  less  dark 
colour. 

(At  the  papilla  conica,  all  the  other  elements  than 
the  nerve-fibres  are  entirely  absent ;  hence  this  is 
presumed  to  be  a  "  blind  spot.") 

Blood-vessels. — The  retina  possesses  a  particular 
vascular  distribution.  The  arteria  centralis  retinae,^ 
with  its  vein,  enters  the  optic  nerve  at  a  short 
distance  from  the  globe,  and  with  it  passes  into  the 
eye ;    they  traverse   the    papilla,  and  immediately 

CAPILLARIES   IN   THE   VASCULAR       ,•{.,.,        ^  i  i  r        i   •    i       •       j-         x    J 

LAYER  OF  THE  RETINA.  dividc  Hito  two  branchcs,  one  or  which  is  directed 
upwards,  the  other  do\vnwards.  Close  and  fine 
anastomoses  unite  the  vessels  of  the  retina  with  the  ciliary  vessels  at  the  back 
of  the  sclerotic. 

The  distribution  of  the  vessels  in  the  different  strata  of  the  retina  is  variable. 
They  are  only  found  in  the  layer  of  nerve-fibres,  in  the  retina  of  the  Horse,  Rabbit, 
and  Guinea-pig  ;  but  they  are  seen  in  all  the  layers — that  of  the  rods  excepted — 
of  the  retina  of  the  other  animals. 

THE   MEDIA   OP   THE   EYE. 

1.  The  Crystalline  Lens  (Fig.  502,/). 

The  lens,  as  its  name  implies,  is  a  (solid)  transparent  body,  sustained  at  the 
smaller  circumference  of  the  zone  formed  by  the  ciliary  processes  (behind  the 
pupil,  and  partially  embedded  in  the  vitreous  humour).  It  is  biconvex  in  shape, 
and  flatter  on  its  anterior  than  its  posterior  surface.  We  have  measured  the  lens 
of  the  Horse's  eye,  and  find  the  following  dimensions  :  vertical  diameter  ^^ 
and  transverse  diameter  -y^  of  an  inch.  The  posterior  face  is  evidently  more 
convex  than  the  anterior,  for  we  found  the  transverse  diameter  of  the  last  to  be 
^,  and  that  of  the  first  -^  of  an  inch. 

Structure. — The  lens  is  enveloped  in  a  transparent  membrane — the  capsule 
—  which  is  not  adherent  to  it.  Its  thickness  is  uniform  in  the  Horse,  and  its 
tissue  is  slightly  striated  transversely ;  its  internal  face  is  lined  by  a  layer  of 
pavement  epithelium.  (It  is  a  homogeneous  elastic  membrane,  partly  of  cuticular 
formation  by  epithelial  cells,  and  partly  an  altered  product  of  the  embryonic 
connective  tissue.) 

The  proper  tissue  {substantia  propria)  of  the  lens  is  disposed  in  concentric 
layers,  the  outer  of  which  are  almost  fluid  (gelatinous),  but  their  consistence 
gradually  increases  towards  the  centre.     These  layers  are  composed  of  hexagonal 


TEE  MEDIA   OF  THE  EYE.  937 

prismatic  bands  (the  fibres  of  the  lens,  themselves  extremely  long  epithelial  cells) 
denticulated  on  their  borders,  and  provided  with  one  or  more  nuclei. 

The  epithelium  on  the  inner  face  of  the  capsule  becomes  dissolved  soon  after 
death,  and  forms  the  liquor  Morgagni^  which  is,  consequently,  nothing  more 
than  a,  post-mortem  product. 

The  lens  has  neither  vessels  nor  nerves. 

In  the  foetus,  it  receives  the  central  artery  of  the  retina— a  branch  which 
passes  forwards  through  the  vitreous  humour  and  enters  the  posterior  face  of  the 
lens  ;  but  this  vessel  disappears  a  long  time  before  birth. 

(It  should  be  noted  that  the  fibres  of  the  lens  pass  in  a  meridional  direction, 
but  none  go  beyond  the  entire  half  of  the  lens — as  the  nearer  a  fibre  starts 
from  the  anterior  pole,  the  further  it  is  removed  from  the  posterior  pole  at  its 
termination. 

To  examine  the  structure  of  the  lens,  it  is  best  to  boil  it,  or  to  immerse  it  in 
alcohol  ,or  very  diluted  nitric  acid,  which  renders  it  hard  and  opaque.  It  is  then 
found  to  be  divided  into  three  equal  parts  by  three  lines,  which  radiate  from  the 
centre  to  within  one-third  of  the  circumference  ;  so  that  each  of  these  portions 
is  composed  of  hundreds  of  concentric  layers,  arranged  within  one  another,  like 
the  coats  of  an  onion.  If  any  single  layer  is  examined  with  the  microscope,  it 
is  found  to  be  made  up  of  these  parallel  fibres,  which  measure  about  :5^oW  of 
an  inch  in  thickness,  and  are  united  to  each  other  by  finely  serrated  or  scalloped 
borders  that  dovetail  in  the  most  beautiful  manner. 

The  lens  is  nourished  by  means  of  the  extremely  delicate  layer  of  nucleated 
cells  on  its  surface,  which  absort  nutriment  from  the  capsule. 

The  use  of  the  lens  is  to  bring  the  rays  of  light  to  a  focus  upon  the  retina, 
they  being  greatly  refracted  in  passing  through  it.) 

2.  The  Vitreous  Humoue  (Fig.  502, 1). 

The  vitreous  hody,  or  humour,  occupies  all  the  cavity  of  the  eye  behind  the 
lens  (about  two-thirds  of  the  interior  of  the  eye). 

It  appears  to  be  a  colourless,  transparent  jelly,  much  more  fluid  than  the 
lens,  and  is  formed  of  a  fluid  amorphous  substance  contained  between  layers  of 
extremely  delicate  connective  tissue,  anastomosing  with  each  other,  in  every 
direction.  On  the  surface  these  layers  join  a  thicker  one,  contiguous  to  a  thinner 
that  envelops  the  whole  mass,  and  named  the  hyaloid  membrane.  Beneath  this 
membrane,  in  front,  are  bundles  of  connective  tissue  which  gradually  diverge 
widely  forward,  and  become  attached  to  the  front  and  posterior  circumference 
of  the  capsule  of  the  lens,  to  constitute  the  zonula  of  Zinn, 

(This  humour  also  contains  round  cells  like  leucocytes,  and  stellate  and 
spindle-shaped  cells,  sometimes  showing  vacuoles  in  their  protoplasm.  The 
spaces  in  the  humour  communicate  freely,  and  are  rendered  apparent  by  freezing 
the  eye  or  steeping  it  in  chromic  acid,  when  it  is  found  that  the  humour  is  inter- 
sected by  a  large  number  of  delicate  partitions,  with  a  cylindrical  space — canalis 
hyaloideus,  or  the  canal  of  Cloquet — in  the  axis,  for  the  passage  of  the  central 
artery  in  the  foetus.  The  menibrane  is  firmer  on  the  surface  than  elsewhere,  so 
that  it  serves  as  a  capsule  for  the  humour,  and  suffices  to  keep  it  in  shape  after 
the  outer  envelopes  of  the  eye  are  removed.  As  mentioned,  the  lens  is  maintained 
in  situ  by  the  zonula  of  Zinn. 

This  humour  concurs  in  refracting  the  rays  of  light.) 


THE  SENSORY  APPARATUSES. 


3.  The  Aqueous  Humour. 


This  is  a  liquid  that  owes  its  name  to  its  great  fluidity  ;  it  is  contained  m 
the  anterior  and  posterior  chambera  of  the  eye,  in  front  of  the  lens.  It  is 
secreted  by  a  particular  membrane — the  membrane  of  the  aqueous  humour,  or 
membrane  of  Descemet  or  Demours — an  extremely  thin  serous  layer,  easily  dis- 
tinguished on  the  posterior  face  of  the  cornea,  and  admitted  to  exist  on  the  two 
surfaces  of  the  iris,  the  ciliary  processes,  and  anterior  face  of  the  capsule  of  the 
lens  (Fig.  502,  o),  where  it  is  reduced  to  epithelium  only. 

Schwalbe  has  observed  the  glandular  appearance  of  the  epithelium  on  the 
ciliary  processes  ;  and  Ehrlich  has  shown  that  when  flourescene  is  injected  beneath 
the  skin,  it  is  eliminated  by  the  anterior  chamber  of  the  eye  when  the  aqueous 
humour  is  evacuated  by  puncture  of  the  cornea.  From  these  facts,  conclusions 
have  been  drawn  as  to  the  analogy  between  this  epithelium  and  a  gland.  Tliis 
gland  is  completely  innervated  (Schaler  and  Uthof,  Nicati)  ;  the  Gasserian 
ganglion  is  its  moderator  centre. 

(The  eyeball  has  no  proper  lymph-vessels,  but  it  has  numerous  small  inter- 
communicating spaces  which  are  related  to  larger  spaces — such  as  Schlemm's 
canal,  the  canal  of  Petit,  the  canalis  hi/aloideus,  Tenon's  space  on  the  dural 
sheath  of  the  optic  nerve  ;  and  this  arrangement  allows  the  lymphatic  system 
of  the  eye  to  be  divided  into  two  regions — an  anterior  and  a  posterior. 

The  chief  function  of  the  aqueous  humour  appears  to  be  to  maintain  the 
convexity  of  the  cornea,  and  to  facilitate  the  movements  of  the  iris  and  lens  ;  as 
well  as  to  assist,  to  some  extent,  in  refracting  the  light  that  passes  through  it 
to  the  lens  and  retina.  The  rapidity  with  which  this  fluid  can  be  regenerated 
is  very  striking  ;  absorption  also  takes  place  very  rapidly  in  the  anterior  chamber 
of  the  eye.  The  frequency  of  adhesions  between  the  iris  and  lens,  after  attacks 
of  ophthalmia,  is  accounted  for  by  the  minute  quantity  of  this  fluid  that  exists 
between  them,  as,  owing  to  the  smallness  of  the  posterior  chamber,  this  is  reduced 
to  a  mere  film.) 

Article  II. — Accessory  Organs  of  the  Visual  Apparatus. 

ORBITAL    CAVITY. 

Preparation. — The  ocular  cavity  is  prepared  by  clearing  the  temporal  fossa  of  its  musc'es 
and  adipose  tissue,  and  removing  the  eyelids,  also  the  eye  and  its  muscles. 

Situated  at  the  side  of  the  head,  at  the  point  corresponding  to  the  union  of 
the  cranium  and  face,  the  orbital  cavity  is  circumscribed  by  a  bony  margin,  in 
the  formation  of  which  the  orbital  process,  frontal,  lachrymal,  malar,  and  a  small 
portion  of  the  zygomatic  process  of  the  temporal  bone,  concur.  Posteriorly, 
however,  there  are  no  bony  walls,  and  the  cavity— in  the  skeleton— is  continuous 
with  the  temporal  fossa.  But  a  fibrous  membrane  completes  this  cavity  in  the 
domesticated  animals,  and  keeps  it  distinct  from  the  fossa. 

Designated  the  ocular  sheath  {ocular  membrane,  or  periorbita),  this  fibrous 
structure  is  attached,  posteriorly,  to  the  border  of  the  orbital  hiatus,  and 
anteriorly  to  the  inner  face  of  the  orbit ;  being  prolonged  beyond  the  external 
lip  of  this  osseous  rim  to  form  the  fibrous  membrane  of  the  eyelids.  Strong 
externally,  the  ocular  sheath  is  thin  where  it  is  in  contact  with  the  bones  of  the 
cavity.     It  is  traversed  by  vessels  and  nerves,  and  is  composed  of  a  mixture  of 


THE  ACCESSORY  ORGANS  OF   VISION.  939 

elastic  and  inelastic  fibres.  (Unstriped  muscular  fibres  have  also  been  described 
as  existing  in  this  orbital  periosteum.) 

Thus  completed,  the  orbital  cavity  has  the  form  of  a  regular  hollow  cone, 
open  at  its  base,  and  closed  at  the  apex,  which  corresponds  to  the  orbital  hiatus. 

In  the  ordinary  position  of  the  head,  the  opening  of  this  cone  is  directed 
forwards,  downwards,  and  outwards. 

Independently  of  the  globe  of  the  eye.  the  orbital  cavity  lodges  the  muscles 
that  move  it,  the  membrana  nictitans,  and  the  lachrymal  gland. 

(Unstriped  muscular  fibres  have  been  found  in  this  ocular  sheath  in  Sheep 
and  other  animals,  also  in  Man.) 

Muscles  of  the  Globe  of  the  Eye  (Fig.  510). 

These  are  seven  in  number  :  five  termed  recti  muscles,  and  distinguished  as 
posterior,  superior,  inferior,  external,  and  internal;  two  named  oblique — a  large 
and  small. 

{Preparation. — Detach  the  eyelids  from  the  margin  of  the  orbit,  cutting  away  the  lower, 
but  leaving  the  upper.  Saw  through  the  zygomatic  process  of  the  temporal  bone,  in  front  of 
the  temporo-maxillary  articulation,  also  through  the  temporal  process  of  the  malar,  and  the 
base  of  the  orbital  process  of  the  frontal  bone ;  remove  the  excised  piece  of  bone,  and  the 
temporal  fossa  and  ocular  sheath  are  exposed.  Cutting  through  the  latter,  the  muscles  of 
the  eye  are  seen  disposed  in  a  conical  manner  around  the  globe ;  dissect  away  the  fat  lodged 
among  them,  in  order  to  isolate  them.) 

L  Posterior  Rectus  or  Suspensory  Muscle  {retractor  oculi,  retractor 
bulbi).— This,  muscle  completely  envelops  the  extra-cranial  portion  of  the  optic 
nerve,  being  a  muscular  sheath  resembling  in  shape  the  fibrous  lining  of  the 
orbit.  Its  fibres  are  disposed  longitudinally,  arise  around  the  optic  foramen,  and 
are  inserted  into  the  posterior  part  of  the  external  face  of  the  sclerotic.  It  is 
always  more  or  less  fasciculated,  and  may  be  frequently  separated  into  four 
portions — superior,  inferior,  external,  and  internal. 

In  contracting,  it  draws  the  globe  towards  the  back  of  the  orbit.  The 
physiological  result  of  this  movement  will  be  noticed  hereafter. 

2.  Superior,  Inferior,  External,  and  Internal  Recti  Muscles. — These 
four  muscles  are  placed  longitudinally  on  the  preceding,  and  repeat,  on  a  large 
scale,  the  disposition  of  its  four  bundles.  As  their  borders  are  in  contact,  they 
constitute  a  fleshy  sheath  around  it,  analogous  to  that  which  it  forms  around  the 
optic  nerve.  Exactly  resembling  each  other,  these  four  muscles  compose  so 
natural  a  group,  that  they  may  be  described  together.  Each  is  a  fiat  band, 
formed  of  parallel  fibres,  firmly  attached  by  its  posterior  extremity  to  the  back 
of  the  sheath,  and  to  the  interior  of  the  subsphenoidal  canal ;  anteriorly,  it  is 
inserted  by  a  thin  aponeurosis  into  the  sclerotic,  at  the  margin  of  the  cornea. 
Isolated  from  one  another,  and  from  the  retractor  by  the  mass  of  fat  belonging 
to  the  membrana  nictitans,  these  small  muscles  are  related,  externally,  to  the 
ocular  sheath. 

There  is  nothing  particular  to  be  noted  regarding  them,  their  position  being' 
sufficiently  indicated  by  their  names.  Their  function  is  to  bring  the  pupillary 
opening  into  contact  with  the  rays  of  light,  by  inclining  the  cornea  towards  them, 
either  upwards,  downwards,  inwards,  or  outwards  ;  or  into  intermediate  positions, 
which  happens  when  two  adjacent  muscles — the  inferior  and  external  rectus,  for 
instance — combine  their  action  at  the  same  moment. 


940 


THE  SENSORY  APPARATUSES. 


3.  Great  Oblique  Muscle  (trocMearis,  or  ohliquus  superior  oculi). — Lying- 
to  the  side  of  the  internal  and  superior  rectus,  and  formed,  like  them,  of  a  fleshy^ 
band  terminated  by  a  thin  aponeurosis,  this  muscle  differs  from  the  preceding  in 
its  interrupted  course.  Arising  from  the  back  of  the  orbit,  and  passing  forward 
against  the  inner  wall  of  that  cavity,  it  reaches  a  strong  fibro-cartilaginous, 
pully-like  process — a  dependency  of  the  aponeurosis  of  the  orbit — attached  by 
its  extremities  to  the  frontal  bone,  at  the  base  of  the  orbital  process  ;  it  passes 
through  this  loop,  and  then  bends  outwards,  to  insinuate  itself  below  the  terminal 
extremity  of  the  superior  rectus,  and  become  inserted  into  the  sclerotic,  between 
the  latter  muscle  and  the  external  rectus. 

This  muscle  pivots  the  eye  inwards  and  upwards  in  the  orbit,  carrying  the 

outer  aspect  of  the  globe  upwards, 
P'g-  ^1^'  and  its  lower  part  outwards  ;  this 

faculty  it  owes  to  its  reflection  in 
the  cartilaginous  loop,  as  it  acts  as 
if  its  insertion  were  at  the  angle  it 
forms  there. 

4.  Small  Oblique  Muscle 
{ohliquus  inferior  oculi).  —  Much 
thicker,  though  very  much  shorter 
than  the  preceding,  and  almost 
entirely  fleshy,  this  muscle  is  placed 
in  a  transverse  direction  on  the 
globe  of  the  eye,  being  nearly 
parallel  to  the  reflected  portion  of 
the  great  oblique.  It  arises  in  the 
lachrymal  fossa,  passes  outwards, 
and  terminates  in  the  sclerotic,  be- 
tween the  external  and  inferior  recti 
muscles. 

It  is  an  antagonist  of  the  great 
oblique,  pivoting  the  eye  in  a  con- 
trary direction. 

It  is  to  be  noted  that  the  double 
rotatory  movement  executed  by  the 
oblique  muscles  is  altogether  involuntary,  and  that  it  is  constantly  produced  when 
the  animal  inclines  its  head  to  one  side— doubtless  to  maintain  the  visual  axis 
always  in  identical  relations  with  the  same  point  of  the  retina.  This  movement 
is  well  seen  in  Man  when  the  head  is  brought  round  to  either  shoulder  :  the  eye 
then  pivots  in  the  orbit  in  an  inverse  direction  to  that  to  which  the  head  inclines, 
so  that  a  mark  placed  at  the  upper  part  of  the  iris  when  the  head  is  straight 
would  occupy  the  same  position  after  the  lateral  movement.  Simultaneous  in 
both  eyes,  this  pivoting  is  executed  by  certain  muscles  in  each  ;  the  great  oblique 
for  one,  the  small  oblique  for  the  other,  according  to  the  direction  in  which  the 
head  is  turned. 

(A  third,  or  middle  oblique  muscle,  has  been  mentioned  by  Strangeways,  as 
sometimes,  if  not  always,  found  between  the  superior  and  inferior  oblique  muscles. 
It  has  been  described  as  arising  by  a  fine  tendon  from  a  small  depression  in 
the  upper  part  of  the  orbital  process  of  the  frontal  bone,  between  the  origin  of 
the  inferior  oblique  and  the  puDey  of  the  superior  oblique  muscle.     This  tendon 


MUSCLES   OF   THE    EYEBALL   (VIEWED    FROM    ABOVE). 

1,  Section  of  orbital  process  of  frontal  bone  to  which 
the  fibro-cartilaginous  pulley,  4,  of  the  superior 
oblique  muscle,  5,  is  attached;  2,  zygomatic 
process  of  the  temporal  bone;  3,  portion  of  sphe- 
noid bone  into  which  the  recti  and  superior  oblique 
muscles  are  implanted ;  6,  pathetic!  nerve ;  7, 
internal  rectus ;  8,  superior  rectus ;  9,  levator 
palpebrae  muscle;  10,  external  rectus;  11,  eye- 
ball; 12,  upper  eyelid;  13,  lower  eyelid;  14,  inner 
canthus  of  eye. 


THE  ACCESSORY  OBGANS   OF   VISION.  941! 

is  succeeded  by  a  fusiform  fleshy  mass,  about  three  lines  in  diameter  and  an  inch 
long,  embedded  in  adipose  tissue  ;  it  passes  obliquely  upwards  and  outwards  on 
the  external  face  of  the  rectus  muscle,  and  terminates  in  a  thin  flat  tendon  which 
accompanies  the  upper  belly  of  the  superior  oblique  for  a  short  distance,  and 
becomes  confounded  with  the  tendon  of  that  muscle  as  it  runs  beneath  the 
superior  rectus.  It  is  supposed  to  be  an  accessory  of  the  superior  oblique,  and 
to  regulate  and  facilitate  the  gliding  of  that  muscle  through  the  acute  angle 
formed  by  its  pulley.) 

Protective  Organs  of  the  Eye. 
1.  The  Eyelids  (Figs.  502,  510). 

Preparation. — There  is  no  difiBculty  in  studying  the  eyelids.  Removing  the  skin  carefully 
allows  the  orbicularis  to  be  seen ;  in  turning  this  up,  the  fibrous  layer  is  found ;  and  if  the 
orbital  process  be  removed  by  means  of  the  saw,  the  levator  palpebrse  superioris  is  discovered 
in  cutting  away  the  upper  part  of  the  ocular  sheath.  Lastly,  on  an  eye  extracted  along  with 
the  eyelids,  the  mode  of  union  of  these  with  the  globe  will  be  readily  demonstrated. 

The  surface  of  the  eye  is  covered  and  protected  in  front  by  two  movable 
membranous  curtains — the  eyelids  {palpebral) — one  superior,  the  other  inferior. 

Attached  to  the  circumference  of  the  orbit  by  their  external  border,  the  eye- 
lids have  a  convex  external  face  formed  by  the  skin,  and  a  concave  internal  face, 
moulded  on  the  anterior  surface  of  the  eye,  and  lined  by  the  conjunctiva,  which 
is  reflected  above  and  beiow  on  the  eyeball — the  duplicatures  constituting  the- 
superior  and  the  inferior  conjunctival  {ox  palpebral)  sinuses. 

Each  lid  has  also  a  free  border  opposed  to  that  of  its  fellow,  with  which  it- 
unites  at  an  angle  by  its  extremities,  so  as  to  form  two  commissures  (or  canthi). 
This  border  is  shghtly  bevelled  on  the  inner  side,  and  shows  a  series  of  small 
openings — the  excretory  orifices  of  the  Meibomian  glands ;  as  well  as  a  row  of 
erect  hairs^ — the  eyelashes.     These  wiU  be  described  presently. 

When  the  two  lids  are  closed  by  the  approximation  of  their  free  borders,  they 
completely  cover  the  eye,  and  form  a  narrow  fissure  comparable  to  a  closed 
button-hole.  When  they  are  separated,  they  circumscribe  an  oval  space  {fissura 
palpebrarum),  the  greater  axis  of  which  is  directed  obliquely  downwards,  forwards^ 
and  inwards.  The  upper  contour  of  this  space — formed  by  the  free  margin  of 
the  superior  eyelid — is  always  more  curved  than  the  lower.  The  superior  com- 
missure (or  canthus)  has  also  been  named  the  temporal  angle  of  the  eye.  The 
nasal  angle,  constituted  by  the  inferior  commissure,  is  always  rounder  than  the 
other  ;  it  lodges  the  caruncula  lacrymalis  (in  the  lachus  lachrymalis). 

Structure  of  the  Eyelids. — A  fibrous  plate,  terminated  towards  the  free 
border  of  the  lid  by  a  small  tendinous  arch  named  the  tarsus  ,•  a  sphincter  muscle — 
the  orbicularis  palpebroe — in  contact  with  the  fibrous  membrane  ;  the  levator  pal- 
pebrcB — a  muscle  partly  lodged  in  the  ocular  sheath,  and  terminated  anteriorly  by 
a  very  thin  and  wide  expansion  placed  beneath  the  superior  fibrous  plate  ;  a 
cutaneous  envelope  in  two  layers — an  external,  the  skin,  and  an  internal  of 
mucous  membrane,  the  conjuncMva,  joining  at  the  free  border  of  the  lid  ; — these 
are  the  elements  which  enter  into  the  composition  of  the  protective  coverings  of 
the  eye. 

1.  Fibrous  Membrane. — Usually  thicker  in  the  lower  than  the  upper  lid, 
this  membrane  is  attached,  by  its  adherent  border,  to  the  rim  of  the  orbit,  where 


942  THE  SENSORY  APPARATUSES. 

it  is  continuous  with  the  periosteum  and  the  fibrous  wall  of  the  ocular  sheath. 
Its  free  border  is  margined  by  the  tarsus. 

2.  Tarsus. — This  is  a  fibrous  lamella  that  forms  a  solid  frame  for  the  free 
border  of  the  lid.  It  is  elongated,  narrow  at  its  extremities,  thin  at  its  fixed 
border — where  it  is  confounded  with  the  fibrous  membrane — and  channeled  on  its 
inner  face  by  several  transverse  parallel  grooves  which  lodge  the  Meibomian 
glands.  This  small  fibrous  arc  regulates  the  contraction  of  the  orbicularis 
muscle,  and  prevents  the  lid  being  drawn  into  wrinkles  ;  by  the  rigidity  it  bestows 
on  the  eyelids,  it  allows  these  to  meet — border  to  border — without  puckering, 
when  the  muscle  is  in  action. 

3.  Orbicular  Muscle  of  the  Eyelids  (orbicularis  palpebrarum,  musculm 
ciliaris  Riolani). — For  a  description  of  this  muscle,  see  Myology,  p.  279. 

4.  Elevator  Muscle  of  the  Upper  Eyelid,  or  Orbito-palpebralis 
{Levator  palpebrce  superioris). — When  the  ocular  sphincter  ceases  to  contract,  the 
lower  eyelid  droops  from  its  own  weight ;  the  upper  lid,  however,  requires  some 
special  muscular  agency  to  raise  it,  and  this  it  finds  in  the  levator  palpebrae. 
This  is  a  very  thin,  narrow,  fleshy  band,  lodged  in  the  ocular  sheath  with  the 
other  muscles  of  the  eyeball,  and  is  related  to  the  superior  rectus,  the  com-se  of 
which  it  follows.  On  reaching  the  lachrymal  gland,  it  expands  into  a  wide 
aponeurotic  membrane  that  passes  between  the  conjunctiva  and  the  fibrous  plate 
of  the  eyelid,  and  terminates  on  the  tarsus.  (Besides  ending  in  the  fascia  jjalpe- 
bralis,  some  of  the  fibres — enclosing  smooth  muscular  fibres — pass  on  to  the  upper 
margin  of  the  tarsus  to  constitute  Miiller's  muscle — or  palpebralis  superior. 
Similar  smooth  fibres  in  the  lower  lid,  form  a  palpebralis  inferior.) 

It  will  be  seen  that  this  muscle  is  inflected  on  the  eyeball  in  a  pulley-like 
manner,  and  it  is  owing  to  this  disposition  that  it  has  the  power  of  raising  the 
lid.  If  the  eyeball  were  not  present,  the  muscle  would  draw  the  free  margin  of 
the  hd  towards  the  back  of  the  orbit,  instead  of  elevating  it. 

5.  Integuments  of  the  Eyelids. — The  different  layers  enumerated  are 
comprised  between  two  tegumentary  folds— the  skin  and  conjunctiva — which  are 
continuous  at  the  border  of  the  eyelids.  We  will  examine  these,  with  their 
appendages — the  eyelashes  and  Meibomian  glands. 

a.  Skin. — Intimately  adhering,  by  its  inner  face,  to  the  orbicularis  muscle, 
this  membrane  is  thin  (smooth),  and  covered  with  numerous  fine  short  hairs.  In 
the  foetus,  it  shows  at  the  orbital  arch — when  the  skin  everywhere  else  is  nude — 
a  well-marked  semicircle  of  hairs — ^the  eyebrow.     Fat  is  never  found  beneath  it. 

b.  Conjunctiva. — The  conjunctiva,  as  its  name  indicates,  joins  the  eyelids  to 
the  eyeball.  Very  fine  and  highly  vascular,  this  mucous  membrane  is  a  continua- 
tion of  the  skin  at  the  border  of  the  lids,  lines  the  inner  face  of  each  of  them, 
envelopes  the  anterior  portion  of  the  membrana  nictitans  in  a  particular  fold, 
covers  the  caruncula  lachrymalis,  and  enters  the  puncta  ;  it  is  then  reflected,  at 
the  adherent  border  of  the  eyelids,  on  to  the  eyeball,  extending  over  the  sclerotic 
and  terminal  aponem-otic  expansion  of  the  recti  muscles.  On  arriving  at  the 
margin  of  the  cornea,  it  is  impossible  to  trace  it  further  ;  though  it  is  represented 
by  the  thin  layer  of  pavement  epithelium  already  described.  At  the  surface  of 
the  lachrymal  caruncle,  it  shows  some  very  fine  hair-bulbs.  It  possesses  some 
papillae  (on  the  palpebral  portion  only,  the  ocular  reflection  being  thinner,  and 
having  none  of  these  nervous  processes),  and  tubular  and  aggregate  glands,  as 
well  as  closed  follicles.  We  have  found  large  numbers  of  the  latter,  the  volume 
of  which  was  considerable  ;  they  form  a  corona  around  the  cornea. 


THE  ACCESSORY  ORGANS  OF   VISION.  943 

c.  Eyelashes. — These  are  two  rows  of  hairs  {cilia)  implanted  in  the  free 
border  of  the  lids,  and  destined  to  prevent  the  entrance  of  dust  and  small 
particles  of  foreign  matter  into  the  eye.  They  are  much  longer,  and  more 
abundant  and  stronger,  in  the  upper  than  the  lower  lid,  their  presence  there 
being  more  necessary,  as  extraneous  particles  are  most  likely  to  enter  the  eye  when 
falHng.  But  if  the  eyelashes  of  the  lower  lid  are  few  and  rudimentary,  this  is 
compensated  for  by  the  presence  on  its  surface  of  some  long  bristly  hairs, 
scattered  here  and  there,  and  exactly  like  the  tentacula  of  the  lips. 

Like  all  hairs,  without  exception,  the  eyelashes  are  flanked  at  their  base  by 
two  or  three  small  sebaceous  glands,  the  duct  from  which  opens  into  their 
follicle. 

d.  Meibomian  glands. — These  are  little  acinous  bodies,  analogous  to  sebaceous 
glands,  which  open  alternately  into  a  common,  and  very  long  excretory  canal. 
They  are  lodged  in  the  transverse  grooves  observed  on  the  inner  face  of  the  tarsal 
ligaments.  The  unctuous  matter  they  secrete  is  thrown  out  on  the  free  border 
of  the  lids,  and  enables  these  to  retain  the  tears  more  easily  within  the  ocular 
cavity.  In  sick  animals,  this  secretion  accumulates  at  the  canthi  and  base  of  the 
lids.  (Each  gland  consists  of  a  central  tube,  with  a  number  of  openings  round 
its  sides  leading  to  short  caecal  dilatations.  The  secretion  also  facilitates  the 
movements  of  the  lids.) 

6.  Vessels  and  Nerves  of  the  Eyelids. — These  membranous  curtains 
receive  their  blood,  for  the  most  part,  by  the  supra-orbital  and  lachrymal 
arteries,  and  the  orbital  branch  of  the  superior  dental  artery.  The  terminal 
extremities  of  the  three  sensitive  nerves  of  the  eye,  formed  by  the  ophthalmic 
branch  of  the  fifth  pair  and  the  orbital  filaments  of  the  superior  maxillary 
branch,  ramify  in  them.  The  anterior  auricular  nerve  causes  the  orbicularis 
muscle  to  contract.  The  motor  filaments  of  the  levator  palpebrse  are  derived 
from  the  third  pair. 

(The  blood-vessels  of  the  eyelids  proceed  from  those  which  pass  from  the 
outer  and  inner  angle  of  the  eye  ;  they  form  an  arch  on  the  inner  margin  of  the 
eyelid — the  arcus  tar  sens  externus.  After  supplying  the  tissues,  some  of  these 
vessels  anastomose  with  the  arteria  ciliaris  antica.  The  ocular  conjunctiva  has 
generally  few  blood-vessels  visible  in  health  ;  when  inflamed,  however,  it  becomes 
intensely  red  and  vascular. 

The  lymphatics  form  a  dense  network  in  the  tarsal  conjunctiva  ;  those  in 
this  membrane  in  front  of  the  sclerotic  and  around  the  margin  of  the  cornea, 
probably  join  the  small  canals  of  the  latter.  The  tunica  propria  of  the  eyelid 
has  many  lymph-cells,  and  in  some  animals — as  Ruminants — they  form  small 
lymphoid  glands. 

The  nerves  of  the  conjunctiva  form  a  rich  plexus  on  the  margin  of  the  eyelid, 
and  terminate  in  small  oval  enlargements  or  end  knobs — the  corpuscles  of  Krause 
— which  are  more  particularly  observed  beneath  the  corneal  epithelium.) 

2.  Membrana  Nictitans. 

This  organ,  which  is  also  named  the  third  eyelid,  winking  eyelid,  etc.,  is  placed 
at  the  greater  (inner)  angle  of  the  eye,  whence  it  extends  over  the  eyeball  to 
reheve  it  from  foreign  bodies  which  may  fall  upon  it. 

It  has  for  its  framework  a  fibro-cartilage — reticulated  or  elastic — irregular 
in  shape,  thick  and  nearly  prismatic  at  its  base,  and  thin  anteriorly,  where  it  is 
covered  by  the  conjunctiva  ;  it  is  continued,  behind,  by  a  strong  adipose  cushion, 


944  THE  SENSORY  APPARATUSES. 

which  is  insinuated  between  all  the  muscles  of  the  eye,  and  to  which  it  is  loosely^ 
attached.  No  muscle  directly  concurs  in  the  movements  of  this  body  :  they  are 
entirely  mechanical.  When  the  eye  is  in  its  usual  position,  there  is  only  per- 
ceived the  fold  of  conjunctiva  that  terminates  it  in  front ;  the  remainder  is 
concealed  in  the  fibrous  case  of  the  eye.  When,  however,  the  latter  is  with- 
drawn into  the  orbit  by  the  contraction  of  its  recti  muscles,  the  globe  compresses 
the  fatty  cushion  belonging  to  the  cartilage  ;  this  cushion,  pressing  outwards, 
pushes  the  membrana  before  it,  and  the  latter  then  entirely  conceals  the  whole 
front  of  the  globe.  This  movement  is  instantaneous,  but  it  may  be  momentarily 
checked  by  pressing  gently  on  the  eye  when  the  animal  retracts  it  within  the  orbital 
cavity. 

The  use  of  the  membrana  is— as  will  be  seen  from  the  above — to  maintain  the 
healthy  condition  of  the  eye,  by  removing  any  matters  that  have  escaped  the 
eyelids  ;  and  what  clearly  demonstrates  this  function,  is  the  inverse  relation  that 
always  exists  between  the  development  of  this  body,  and  the  facility  with  which 
animals  can  rub  their  eyes  with  their  anterior  limbs.  So  it  is  that,  with  the- 
Horse  and  Ox,  the  thoracic  limb  of  which  cannot  be  applied  to  this  purpose^ 
the  membrana  is  very  developed  ;'  in  the  Dog,  which  may  use  its  paw  to  somfr 
extent  when  it  requires  to  brush  its  eye,  it  is  smaller  ;  in  the  Cat  it  is  still  less ; 
while  in  the  Monkey  and  in  Mankind,  whose  hands  are  perfect,  it  is  rudimentary. 
In  Tetanus,  the  membrana  nictitans  often  remains  permanently  over  the  eye,  in 
consequence  of  the  continued  contraction  of  the  recti  muscles. 

(Towards  the  middle  of  the  outer  face  of  the  membrana  is  a  small  yellowish- 
red,  acinous  gland — the  glandula  Harden,  firmly  bound  by  a  strong  fibrous 
membrane  to  the  cartilage,  and  surrounded  by  adipose  tissue  ;  it  secretes  a  thick 
unctuous  matter,  which  escapes  by  two  or  three  small  apertures  on  the  inner  face 
of  the  membrana.) 

LACHRYMAL   APPARATUS. 

Preparation. — The  lachrymal  gland  is  prepared  at  the  same  time  as  the  levator  palpebrarum 
(see  above).  To  dissect  its  excretory  apparatus,  melted  tallow  should  be  injected  into  the 
lachrymal  canals  by  the  nasal  opening  of  the  duct.  The  lachrymal  bone  should  be  chiselled 
away,  iu  order  to  see  the  canal ;  the  nasal  portion  can  be  shown  in  a  longitudinal  and  vertical 
section  of  the  head,  made  outside  the  median  plane. 

This  apparatus  comprises  :  1.  A  gland  which  secretes  the  tears.  2.  A  series 
of  canals  that  carry  the  superfluous  fluid  to  the  external  orifice  of  the  nasal 
cavities. 

Lachrymal  gland. — This  gland,  situated  between  the  orbital  process  and  the 
upper  part  of  the  eyeball — from  which  it  is  separated  by  the  superior  rectus  and 
levator  palpebrae  muscles — is  convex  on  its  upper  face,  and  concave  inferiorly,  in 
accordance  with  the  parts  it  adjoins.  Only  little  developed,  it  is  formed  of  very 
small  granules,  united  by  fine  connective  tissue  ;  from  these  arise  minute  radicles, 
the  junction  of  which  forms  a  certain  number  of  very  narrow  ducts,  that  open 
on  the  inner  face  of  the  temporal  (outer)  angle  of  the  eyelids.  These  are  the 
hygrophthalmic  canals. 

The  lachrymal  gland  secretes  the  tears  that  lubrify  the  anterior  surface  of 
the  eye.  This  fluid  escapes  upon  the  organ  at  the  temporal  angle  of  the  lids, 
and  is  carried  between  them  and  the  eyeball  towards  the  nasal  angle.  Its> 
secretion  is  incessant,  but  it  js  increased  by  anything  that  irritates  the  con- 
junctiva, and  its  character  may  even  change  under  the  same  influences. 


THE  ACCESSORY  ORGANS  OF   VISION.  945 

The  lachrymal  gland  belongs  to  the  category  of  conglomerate  glands  ;  con- 
sequently, it  IS  analogous  to  the  salivary  glands.  (The  gland  is  maintained  in 
situ  by  a  capsule  formed  by  the  fascia  of  the  orbit.) 

The  hygrophthalmic  canals  have  a  thin  fibrous  membrane  for  their  walls ; 
.this  is  covered  by  cyUndrical  epithelium. 

Caruncula  lachrymalis. — This  name  is  given  to  a  small  round  (or  fusiform) 
body,  frequently  entirely,  or  partially  black  (or  brown),  slightly  uneven,  and 
situated  in  the  nasal  angle  of  the  eye ;  it  is  nothing  more  than  a  small  fold  of 
conjunctiva  covering  some  agglomerated  follicles,  and  the  bulbs  of  several  fine 
hairs,  which  are  readily  seen  on  its  surface.  It  may  be  regarded  as  designed  to 
•direct  the  tears  towards  the  puncta,  or  to  separate  any  extraneous  particles  that 
this  fluid  may  carry  towards  it. 

It  has  for  its  base  a  small  mass  of  connective  tissue,  in  the  midst  of  which 
are  some  hair-roots,  and  some  rather  large  glandules,  lined  by  an  epithelium 
■charged  with  fat-granules.     Nerve-tubes  ramify  around  the  hair-bulbs. 

Puncta  lachrymalia. — These  are  two  little  openings,  situated  one  in  each 
eyelid,  a  short  distance  from  the  nasal  commissure,  by  which  the  tears  pass  from 
the  oculo-palpebral  surface  into  the  lachrymal  'ducts. 

Lachrymal  ducts. — These  are  continuations  of  the  last,  and,  like  them,  are 
very  narrow  ;  they  carry  the  tears  into  the  lachrymal  sac.  The  superior  is 
longer  than  the  inferior  duct,  and  arrives  at  the  sac  behind  it.  The  mucous 
membrane  lining  these  ducts  is  thin,  and  covered  by  a  stratified  pavement 
epithelium,  similar  to  that  of  the  conjunctiva. 

Lachrymal  sac. — This  little  reservoir— lodged  in  the  indifundibulum  that 
precedes  the  lachrymal  foramen  in  the  bone  of  that  name — receives  the  tears 
from  the  two  ducts,  and  passes  them  into  the  lachrymal  canal.  Its  mucous 
membrane  only  differs  from  that  of  the  ducts  in  being  covered  with  ciliated 
epithelium. 

Lachrymal  canal  (nasal  duct). — The  tears  accumulated  in  the  sac  flow  into 
this  long  duct,  which  extends  to  the  lower  aperture  of  the  nostril.  About  one- 
half  of  its  course  is  in  the  canal  of  the  lachrymal  bone,  which  protects  it,  and 
which  terminates  between  the  two  turbinated  bones.  The  remainder  of  the  canal 
is  beneath  the  nasal  mucous  membrane,  whence  it  passes  to  the  inner  surface  of 
the  outer  wing  of  the  nostril ;  there  it  terminates  by  an  orifice — sometimes  two 
— that  looks  as  if  punched  out  of  the  membrane,  towards  the  lower  commissure, 
near  the  point  where  there  is  a  line  of  demarcation  between  the  dark  colour  of 
the  skin  and  the  rosy  tint  of  the  mucous  lining. 

This  aperture  constitutes  the  "  nasal  outlet." 

The  epithelium  of  the  membrane  lining  the  canal  is  ciKated  in  its  bony, 
■stratified  in  its  nasal,  portion.  On  the  surface  of  the  membrane  are  to  be  seen 
the  openings  of  the  secretory  ducts  of  some  racemose  glands,  which  are  lodged 
in  the  walls  of  the  canal.  Throughout  its  extent,  the  canal  is  lined  by  a  con- 
tinuation of  the  mucous  membrane  of  the  lachrymal  sac.  In  Solipeds,  this  canal 
•opens  on  the  cutaneous  surface  at  the  entrance  to  the  nostrils  ;  it  therefore 
happens  that  in  these  animals  the  conjunctiva,  with  it  prolongations,  forms  a 
particular  mucous  membrane,  independent  of  the  great  gastro-pulmonary 
membrane. 

In  the  Ass  and  Mule,  the  orifice  of  the  lachrymal  canal  is  situated  at  the 
inner  face  of  the  outer  wing  of  the  nostril,  and  not  near  the  inferior  conmiissure, 
as  in  the  Horse. 


946  THE  SENSORY  APPARATUSES. 

(Sometimes  this  outlet  is  double.  The  lachrymal  secretion  is  not  only  useful 
in  facilitating  the  movements  of  the  eyelids  over  the  eyeball,  but  it  washes  away 
dust  and  hurtful  matter  from  off  the  surface  of  the  cornea,  keeping  the  epithelium 
clean,  moist,  and  healthy.) 

Differential*  Characters  in  the  Visual  Apparatus  of  the  other  Animals. 

t 

Essential  Organ  of  "Vision.— In  the  Ox,  the  eyeball  resembles  in  shape  that  of  tlie 
Horse ;  but  in  small  animals,  particularly  the  Dog,  it  is  much  more  spherical.  In  Birds  it 
is  very  convex  in  front ;  its  largest  diameter  is  the  antero-posterior. 

Sclerotic— This  is  the  same  in  all  the  domesticated  quadrupeds.  In  Birds,  however,  it 
has  some  curious  features.  Posteriorly,  it  has  for  base  a  cartilaginous  layer,  covered  on  both 
sides  by  fibrous  tissue ;  this  layer  frequently  ossifies  around  the  optic  nerve,  where  it  forms 
the  posterior  sclerotic  ring.  Around  the  cornea,  there  is  the  anterior  sclerotic  ring,  composed 
of  small  bony  imbricated  scales,  capable  of  moving  on  each  other,  and  modifying  the  shape  of 
the  globe  of  the  eye. 

Cornea. — In  the  Dog  and  Cat,  the  structure  of  the  cornea  is  similar  to  that  of  the  Horse. 
In  the  Ox,  Sheep,  and  Pig,  there  are  two  limitary  membranes ;  one,  consequently,  beneath 
the  epithelium  of  the  anterior  face.     In  Birds,  this  limitary  membrane  is  thickest  in  front. 

Choroid. — In  Mammifers,  there  are  some  sliglit  differences  in  the  coloration  of  the  tapetum. 
Thus,  in  the  Ox,  it  is  golden  green,  wliich  becomes  blue  at  the  circumference;  iu  the  Sheep, 
it  is  a  pale  golden  green  ;  a  golden  yellow  in  the  Cat ;  and  white,  bordered  with  blue,  in  the 
Dog.  (It  is  absent  in  the  Pig.)  In  Birds,  it  is  uniformly  black ;  this  membrane  has  also  a 
network  of  non-striped  muscular  fibres,  and,  in  addition,  "  Crampton's  muscle,  which  arises  from 
the  inner  face  of  the  osseous  ring,  and  is  inserted  into  the  cornea  "  (Leydig).  (According  to 
Hassenstein,  in  rapacious  animals  there  is,  behind  the  tapetum,  a  layer  of  corpuscles  composed 
of  lime  salts ;  to  this  is  owing  the  brilliancy  of  their  eyes  in  the  dark.) 

Jris. — In  all  animals  the  iris  is  muscular.  In  Mammifers,  the  contractile  fibres  are  non- 
striped;  in  Birds,  they  are  striped.  (In  the  Ox,  its  anterior  face  has  a  brighter  colour  than 
in  the  Horse.  In  the  Sheep,  it  is  a  brownish  yellow ;  in  the  Goat,  blue.)  In  the  Dog,  its 
colour  is  a  more  or  less  bright  golden  yellow;  in  the  adult  Cat,  green  ;  and  in  young  animals, 
a  bright  blue.  The  pupil  is  elliptical  iu  the  Ox,  as  iu  Solipeds  (in  the  Sheep  and  Goat,  it 
is  more  elongated) ;  in  the  Dog,  it  is  circular,  and,  when  very  much  diluted,  it  is  the  same  in 
the  Cat;  but,  when  contracted,  it  becomes  elliptical  vertically,  and  may  be  so  narrow  as  to 
represent  nothing  more  than  a  thin  perpendicular  slit.     (In  the  Pig,  it  is  round.) 

There  are  no  differences  worthy  of  note  in  the  other  parts  of  the  eye. 

Accessory  Organs  of  the  Visual  Apparatus. — The  motor  and  protective  organs 
are  nearly  the  same  in  all  the  other  animals. 

Muscles. — Birds  have  only  six  muscles — four  recti,  and  two  oblique.  The  latter  arise  from 
the  anterior  wall  of  the  orbit ;  consequently,  the  great  oblique  does  not  pass  through  a  pulley. 

(The  posterior  rectus,  or  retractor  muscle,  is  most  developed  in  Ruminants,  which,  during 
their  whole  time  of  feeding,  have  the  head  in  a  dependent  position.  In  most  of  the  Carnivora, 
instead  of  this  muscle  forming  a  complete  hollow  cone,  as  in  Ruminants,  there  are  four  distinct 
strips,  almost  resembling  a  second  set  of  recti  muscles,  but  deep-seated,  and  inserted  into  the 
posterior,  instead  of  the  anterior,  portion  of  the  globe.) 

Eyelids. — The  disposition  of  these  is  the  same  in  all  Mammifers.  In  Birds,  the  lower  lid 
is  the  largest,  and  is  furnished  with  a  particular  depressor  muscle ;  there  are  no  Meibomian 
glands.  There  is  a  third  eyelid,  corresponding  to  the  membrana  nictitans  of  Quadrupeds;  it 
is  suflBciently  extensive  to  cover  the  entire  front  of  the  eye,  and  is  moved  by  a  curious  little 
apparatus. 

Glands.— In  Ruminants,  the  Pig,  and  in  Birds,  there  is  found  annexed  to  the  membrana 
nictitans,  Earder's  gland— &  conglomerate  gland,  with  adipose  epitlielium  in  Mammifers,  and 
cylindrical  and  granular  in  Birds.  It  secretes  a  thick  white  matter,  which  is  thrown  out  on 
the  membrana  by  one  or  two  orifices.  Its  use  is,  doubtless,  to  favour  the  movements  of  that 
organ  over  the  surface  of  the  eye,  as  well  as  those  of  the  eyelids.  (In  the  Ox,  this  gland  is 
voluminous;  it  has  two  large  and  several  small  ducts.  The  lachrymal  gland  is  also  voluminous, 
and  its  nasal  opening  is  situated  liigher  in  the  nostril  than  in  the  Horse.  In  the  Sheep,  there 
are  found,  near  the  lachrymal  fossa,  several  adipose  follicles,  which  do  not  properly  belong  to 
this  apparatus,  and  which  secrete  a  consistent,  unctuous,  yellow  matter  In  the  Pig,  the 
lachrymal  ducts  are  separated,  by  a  bony  partition,  into  two  sets,  as  far  as  the  lachrymal  sac.) 


TEE  AUDITORY  APPARATUS.  947 

Comparison  of  the  Visual  Apparatus  of  Man  with  that  of  Animals. 

Essential  Organ  of  Vision.— The  eyeball  of  Man  is  almost  spherical,  as  in  the 
carnivora. 

The  sclerotic  does  not  differ  much.  The  cornea  has  two  limitary  membranes,  and  is  much 
less  elliptical  than  in  Solipeds.  The  choroid  has  the  same  zone  as  in  animals ;  it  is  uniformly 
brown.  The  ciliary  processes,  seventy  to  eighty  in  number,  are  a  little  longer  than  in  the 
Horse,  and  do  not  exceed,  in  front,  the  ciliary  ligament,  to  the  inner  face  of  which  they  adhere 
throughout  their  external  border.  The  pupillary  opening  of  the  iris  is  always  round.  The 
retina  is  the  same  in  structure  as  already  described.  A  little  above  the  optic  papilla,  there  is 
a  circular  or  oval  patch,  about  5',  of  an  inch  in  diameter,  in  the  centre  of  which  is  a  transparent 
spot ;  this  is  the  yellow  spot  (macula  lutea),  with  the  fossa  centralis  of  the  retina  (fovea  centralis, 
foramen  of  Soemmering). 

At  this  patch,  the  tissue  of  the  retina  is  slightly  modified,  especially  at  the  fossa  ;  there  are 
only  cones  in  the  columnar  layer,  and  all  the  other  layers  appear  to  be  confounded  into  one 
granular  mass.  (This  spot  only  exists  in  animals  which  have  the  axes  of  the  eyeballs  parallel 
with  each  other,  as  in  Man,  the  Quadrumana,  and  some  saurian  Reptiles.) 

There  is  nothing  particular  in  tlie  aqueous  humour,  lens,  or  vitreous  humour. 

Accessory  Organs  of  the  Visual  Apparatus. — The  orbital  cavity  in  Man  is  entirely 
enclosed  by  bony  walls,  and  there  is  no  fibrous  sheath.  (A  fold  of  the  orbital  fascia  has  been 
described  as  separating  the  eye  from  its  surrounding  adipose  tissue,  and  which,  like  a  "tunica 
vaginalis,"  enables  the  globe  to  roll  with  rapidity  and  precision.)  The  muscles  are  six  in 
number — four  recti,  and  two  oblique;  the  great  oblique  is  the  same  as  in  animals.  Only  the 
rudiment  of  a  caruncula  lachrymalis  is  present.  The  nasal  duct  opens  at  some  distance  up  on 
the  surface  of  the  inferior  meatus. 


CHAPTER  V. 
AUDITORY  APPARATUS. 


The  sense  of  hearing — destined  for  the  perception  of  sounds  produced  by  the 
vibration  of  bodies — has  for  essential  agents  the  auditory  or  eighth  pair  of 
cranial  nerves,  the  terminal  fibrillae  of  which  ramify  in  the  membranous  walls 
of  a  system  of  cavities  forming  the  internal  ear.  These  cavities  are  excavated  in 
the  substance  of  the  petrous  bone,  and  communicate,  externally,  by  means  of 
two  other  systems  of  diverticuli,  which  constitute  the  middle  and  external  ear. 

Article  L — Internal  Ear,  or  Labyrinth. 

The  cavities  which,  together,  compose  this  part  of  the  auditory  apparatus, 
being  entirely  channeled  within  the  petrous  portion  of  the  temporal  bone,  have 
their  walls — forming  the  osseous  labyrinth — constituted  by  that  bone.  They 
contain  the  soft  parts,  named  the  membranous  labyrinth,  and  fluids  {endolymph). 

The  Osseous  Labyrinth. 

This  is  composed  of  three  portions  :  the  vestibule,  semicircular  canals,  and 
cochlea. 

Preparation.— These  cavities  can  be  seen  by  making  sections  through  the  petrous  bone,  in 
different  directions.  But  it  is  better  to  expose  them  by  cutting  away  this  bone,  after  it  has 
beeu  softened  by  prolonged  steeping  in  dilute  nitric  acid. 


948 


THE  SENSORY  APPARATUSES. 


1.  The  Vestibule  (Fig.  515,  /). 

This  is  a  small,  somewhat  oval  cavity,  in  the  centre  of  the  bone,  and  outside 
the  perforated  bony  plate  that  forms  the  bottom  of  the  internal  auditory  hiatus. 
It  is  a  real  vestibule,  with  regard  to  the  other  parts  of  the  labyrinth,  which  all 
open  into  it. 

On  its  external  ivall  is  the  fenestrn  ovalis  (fenestra  vestibuli),  an  opening 
closed  by  the  stapes.  The  inner  wall  shows  the  foramina  through  which  the 
filaments  of  the  vestibular  branch  of  the  auditory  nerve  pass.  Below.,  and  in 
front,  is  a  large  orifice,  the  commencement  of  the  scala  cochleae  ;  above,  are  five 
little  apertures,  the  openings  of  the  semicircular  canals. 

2.  The  Semicircctlar  Canals  (Fig.  513). 

Three  in  number,  and  very  narrow,  these  canals  owe  their  name  to  their 
•form.     They  are  placed  above  the  vestibule,  like  three  semicircular  arches 


Fig.  511. 


;^--e^ 


DIAGRAM   OF   THE   LABYRINTH    IN   FISHES,    BIRDS,    AND   MAMMALS 

I.  FISH;  n.  bird;  III.  mammal. 
JT,  Utricle;  S,  saccule;   US,  utricle  and  saccule;  Cr,  canalis  reuniens;  R,  recessus  of  the  labyrinth; 
VC,  commencement  of  the  cochlea ;  C,  cochlear  canal ;  L,  logenulus ;   R',  cupola,  forming  the 
summit  of  the  cochlear  canal ;    V,  caecum  of  the  vestibule  of  the  cochlear  canal. 

united  in  a  triangular  manner  at  their  base,  and  are  distinguished  as  superior 
or  anterior,  posterior,  and  external.  The  first  two  open  together,  by  their  adjacent 
extremities,  into  the  vestibule  ;  consequently,  there  are  only  five  orifices  of  the 
semicircular  canals  in  this  cavity.  In  addition,  the  adjoining  openings  of  the 
posterior  and  external  canals  are  so  close  to  each  other,  that  they  appear  to  be 
sometimes  united  at  the  bottom  of  a  short  common  canal. 


3.  The  Cochlea  (Fig.  514). 

Situated  behind,  and  below  the  vestibule,  at  the  inner  wall  of  the  cavity  of 
the  tympanum,  the  cochlea  (snail-shell)  is  well  named,  as  it  presents  exactly  the 
form  of  certain  molluscs'  shell.  It  is  a  spiral  conical  canal,  twisting  downwards, 
forwards,  and  upwards,  around  a  central  conical  axis  (the  modiolus,  or  columella) ; 


TEE  AUDITORY  APPARATUS. 


SO  that  its  centre  nearly  corresponds  to  the  inner  wall  of  the  tympanum.  A 
partition — the  lamina  spiralis,  spiral  like  the  cavity — divides  it  into  two  distinct 
sections,  or  scales — a  superior  and  inferior.  This  partition  is  attached  by  its  inner 
border  to  the  central  axis  of  the  cochlea,  but  is  free  at  its  external  margin,  whick 
does  not  quite  reach  the  periphery  of  the  cavity.     The  two  scalse,  therefore^ 


Fig.  512. 


SECTION    THROUGH   ONE   OF   THE   COILS   OF   THE 
COCHLEA. 

ST,  Scala  tympani ;  SV,  scala  vestibuli ;  CC,  canalis 
cochleae ;  membrana  of  Reissner ;  lis  to  Isp,  lamina 
spiralis  membi-anacea;  Us,  limbus  laminae  spiralis; 
ss,  sulcus  spiralis ;  gs,  ganglion  spirale  situated 
on  nc,  the  nervous  cochlearis  indicated  by  the 
black  line  ;  Iso,  lamina  spiralis  ossea  ;  t,  mem- 
brana  tectoria;  6,  membrana  basilaris  ;  Co,  organ 
of  Corti;  Isp,  ligamentum  spirale;  Cc,  cells  of 
Claudius.  1,  Rod  of  Coiti  of  the  first  order  ;  2, 
rod  of  Corti  of  the  second  order. 

communicate,  in  the  skeleton,  by  means  of  an 
opening  (the  helico-trema)  that  follows  the  free 
border  of  the  lamina  spiralis  throughout  its 
extent. 

The  inferior  scala  (or  scala  vestibuli)  enters 
the  vestibule ;  the  commencement  of  the 
superior  scale,  or  scala  tympani,  is  formed  by 
the  fenestra  rotunda  {fenestra  cochleae),  which 
brings  it  into  communication  with  the  middle 
ear,  without  the  presence  of  a  membrane  ex- 
actly closing  that  aperture. 


Fig.  513. 


SECTION  OF  THE  COCHLEA  PARALLEL  T0» 
ITS  AXIS,  THROUGH  THE  CENTRE  OP- 
THE   MODIOLUS. 

1,  Modiolus  ;  2,  infundibulum  in  which 
the  modiolus  terminates  ;  3,  3,  coch- 
lear nerve,  sending  its  filaments 
through  the  centre  of  the  modiolus ; 
4,  4,  scala  tympani  of  the  first  turoi 
of  the  cochlea  ;  5,  5,  scala  vestibuli 
of  the  first  turn;  the  septum  between 
4  and  5  is  the  lamina  spiralis;  a. 
filament  of  the  cochlear  nerve  is 
seen  passing  between  the  layers  of 
the  lamina  to  be  distributed  in  thfr 
membrane  investing  the  lamina ;  8, 
loops  formed  by  the  filaments  of  the 
cochlear  nerve  on  the  lamina  spiralis;. 
9,  9,  scala  tympani  of  the  second 
turn  of  the  cochlea  ;  10,  10,  scala 
vestibuli  of  the  second  turn ;  the- 
septum  is  the  lamina  spiralis;  11, 
the  remaining  half  turn  of  the  scala. 
vestibuli ;  tlie  dome  above  is  the- 
cupola,  the  line  passing  thi-ough  it 
leads  to  the  remaining  half  turn  of 
the  scala  tympani.  The  osseous 
lamina  forming  the  floor  of  the  scala 
vestibuli  curves  spirally  round  to- 
constitute  the  infundibulum,  2;  14, 
the  helicotrema  through  which  a 
bristle  is  passed ;  its  lower  extremity 
issues  from  the  scala  tympani  of  the- 
middle  turn  of  the  cochlea. 


The  Membranous  Labyrinth. 

The  membranous  labyrinth  comprises  three  parts,  corresponding  to  the  threfr 
cavities  of  the  osseous  labyrinth.  1.  The  vestibule.  2.  The  semicircular  canals. 
3.  The  cochlea. 


1.  The  Membranous  Vestibule  (Fig.  513). 

This  is  composed  of  two  sacs  with  thin,  soft  walls,  lodged  in  the  osseous; 
labyrinth.  The  supei'ior  is  the  largest,  is  oval-shaped,  and  is  named  the  utriculus ; 
it  communicates  with  the  semicircular  canals,  of  which  it  is  a  confluent.     The 


950 


THE  SENSORY  APPARATUSES. 


infmor  is  smaller,  spherical  in  shape,  and  forms  the  sacculus ;  it  appears  to  be 
perfectly  closed,  though  in  contact  with  the  utriculus. 

The  membranous  vestibule  is  composed  of  two  distinct  layers—  an  external, 
of  connective  tissue  ;  and  an  internal,  epithelial,  resting  on  an  amorphous  mem- 
brane. At  the  expansion  of  the  nerve-filaments,  the  latter  is  absent,  and  is 
replaced  by  a  white  calcareous  substance  (minute  crystalline  particles  of  carbonate 
and  phosphate  of  lime)  which,  in  the  domesticated  animals,  appears  as  a  powder, 
and  is  named  the  calcareous  powder  of  the  vestibule,  ear-dust,  or  otoconites 
(otoliths), 

(Some  authorities  give  four  layers  :  an  external  or  serous,  derived  from  the 

lining   membrane   of   the  laby- 
^ig-  51*-  rinth  ;   a  vascular,  with  multi- 

tudes   of    vessels ;     a    nervous, 
_     _^  formed  by  the  expansion  of  the 

^1^^  ^'^    .|^P2^'^--^^^^gt^l||  ,  filaments  of  the  vestibular  nerve  ; 

//f  '^""^     /   jtV\'^^^^p^^*^^K^pff|ffif^  and  an  internal  serous  membrane, 

r/U    P'S,'%^^mmmj^^»!m\\n\mM,/       ^^.^^^Yi  secretes  the  limpid  fluid 

contained  in  its  interior.  Spots 
of  pigment  are  constantly  found 
in  the  tissue  of  the  membranous 
labyrinth.) 

2.  The  Membranous  Semicir- 
cular Canals  (Fig.  513). 

These  are  three  thin  tubes, 
which  correspond  exactly  with, 
though  they  are  of  smaller 
diameter  than,  the  osseous  semi- 
circular canals ;  they  open  into 
the  utriculus  in  the  same  manner 
as  the  latter  do  into  the  bony 
vestibule.  Each  has  one  of  its 
two  extremities  dilated  into  a  sac 
or  ampulla  (sinus-ampullaceus) ; 
for  the  two  superior  and  external 
canals  it  is  the  anterior  extremity, 
and  for  the  posterior  canal  the 
outer  extremity. 

In  structure  they  resemble 
the  vestibular  sacs. 


THE  COCHLEA  OPENED,  TO  SHOW  THE  ARRANGEMENT 
OF  THE  TWO  RAMPS  AND  DISTRIBUTION  OF  THE 
AUDITORY   NERVE. 

a,  Cochlea ;  b,  auditory  nerve ;  c,  blood-vessel ;  d,  d', 
vascular  ramifications ;  e,  posterior  part  of  facial 
nerve  turned  upwards;  /,  intermediate  nerve  of 
Wrisberg ;  g,  summit  of  tiie  cochlea ;  h,  common 
trunks  of  the  petrosal  nerves. 


3.  The  Membraj!I0us  Cochlea  (Fig.  514). 

The  membranous  cochlea  is  represented  by  two  membranes,  which  complete 
the  lamina  spiralis ;  they  continue  the  osseous  laminse  of  the  latter,  and  are 
inserted  into  the  external  wall  of  the  cochlea. 

They  give  rise  to  three  cavities,  or  scalse,  in  the  interior  of  this  portion  of 
the  ear — an  inferior,  or  tj/mpanic  scala ;  a  superior,  or  vestibular  scala ;  and  a 
middle,  or  auditive  scala,  in  which  the  organ  of  Corti  is  lodged.  The  vestibular 
scala  is  itself  divided  by  the  membrane  of  Reissner  into  two  canals — the  jrroper 


THE  AUDITORY  APPARATUS.  95I 

vestibular  scala,  and  Lowenherg's,  or  the  collateral  scala ,-  so  that,  m  reality,  there 
are  four  cochlean  scalae  (Fig.  512). 

We  do  not,  therefore,  find  in  the  cochlea — as  in  the  other  regions  of  the 
labyrinth — a  system  of  membranous  cavities  included  in  osseous  cavities. 

The  structure  of  the  membranes  that  limit  the  auditive  scala  is  not  perfectly 
known,  and  is  still  disputed  by  anatomists  ;  but  connective,  epithelial,  and  nerve 
elements  appear  to  form  their  base. 

With  regard  to  the  organ  of  Corti,  it  is  a  very  curious  and  interesting  portion 
of  the  auditory  scala,  being  formed  of  a  series  of  solid  and  elastic  arches  resting 
by  their  extremities  on  the  membrane — the  basilar — that  separates  the  auditory 
from  the  tympanic  scala,  their  convexity  being  towards  the  superior,  or  membrane 
of  Corti.  These  arches  number  about  three  thousand  in  Man,  and  are  composed 
of  two  portions  or  articles — an  external  and  an  internal,  united  by  a  thickening 
in  the  vicinity  of  the  membrane  of  Corti.  To  these  elastic  arches  are  added 
conical  or  fusiform  ciliated  cells,  the  function  of  which  is  to  increase  and  transmit 
to  the  terminations  of  the  auditory  nerve,  the  slightest  vibrations  of  the  organ 
of  Corti.     (For  fmther  details,  see  works  on  Histology.) 

Fluids  of  the  Labyrinth. 

These  liquids  are  of  two  kinds — one  is  contained  in  the  membranous  labyrinth, 
the  other  in  the  osseous  labyrinth. 

The  fluid  of  the  membranous  labyrinth — or  endo-lymph  of  Breschet — is  con- 
tained in  the  sacs  and  tubes  constituting  the  membranous  vestibule  and  semi- 
circular canals.  It  is  limpid  and  fluid  like  water.  The  fluid  of  the  osseous 
labyrinth,  or  peri-lymph  of  Breschet,  fills  the  two  scalfe  of  the  cochlea,  and 
bathes  the  external  surface  of  the  vestibule  and  membranous  semicircular  canals, 
which  it  separates  from  the  corresponding  walls  of  the  osseous  labyrinth. 

Distribution  and  Termination  of  the  Auditory  Nerve  in  the 
Membranous  Labyrinth. 

This  nerve  (the  i^ortio  mollis  of  the  seventh  pair)  divides,  as  we  have  said, 
into  two  branches — a  cochlear  and  a  vestibular. 

The  cochlear  branch,  the  largest,  reaches  the  base  of  the  cochlea,  where  it 
breaks  up  into  a  large  number  of  fasciculi,  one  portion  of  which  expands  over 
the  first  turn  of  the  lamina  spiralis,  the  other  on  the  second,  and  a  third  on  the 
third  ;  the  latter  ramifications  penetrate  to  the  auditory  scala,  and  terminate  on 
the  organ  of  Corti.  This  anatomist  has  seen,  on  the  primary  fibres  of  these 
ramifications,  a  gangUonic  cell  {ganglion  spiral),  at  the  point  where  they  leave 
the  lamina  spiralis  ossea.  The  primary  fibres  finally  lose  their  myelin  sheath, 
and,  reduced  to  their  axile  filament,  they  terminate  in  the  cells  accompanying  the 
arches  of  Corti. 

The  vestibular  branch  divides  into  three  portions,  their  terminal  filaments 
passing  through  the  openings  of  the  perforated  spots  (foramina  7iervina)^  and 
ramify  in  the  wall  of  the  sacculus,  utriculus,  and  the  ampulla;  at  the  extremities 
of  the  three  semicircular  canals. 

Article  II. — Middle  Ear,  or  Case  of  the  Tympanum. 

Excavated  in  the  substance  of  the  petrous  portion  of  the  temporal  bone,  on 
the  limit  of  the  petrous  and  mastoid  sections — but  chiefly  in  the  latter — the  middle 


952  THE  SENSORY  APPARATUSES. 

ear  constitutes  an  irregular  cavity,  which  we  may  consider  as  composed  of  two 
walls  and  a  circumference. 

The  external  ivall  is  principally  constituted  by  the  membrane  of  the  tympanum. 
The  internal  wall,  formed  by  the  petrous  bone,  offers  two  openings — the  fenestra 
ovalis  a,nd  fenestra  rotunda — the  one  situated  behind  the  other,  and  separated  by 
a  small  eminence  named  the  promontory.  The  circumference  is  occupied  for 
nearly  the  whole  of  its  extent  by  the  mastoid  cells — large  open  cavities  in  the 
tympanum. 

Internally,  the  tympanum  contains  a  chain  of  small  bones  named  the  malleus, 
incus,  OS  orbiculare,  and  stapes  ;  these  bones  form  the  medium  of  communication 
between  the  tympanum  and  the  fenestra  ovalis  —from  one  wall  to  the  other  of 
the  cavity  of  the  tympanum. 

This  cavity  is  lined  by  a  fine  mucous  membrane,  which  is  continuous  with. 
that  lining  the  pharynx,  by  means  of  a  cartilagmous  canal — the  Eustachian  tube^ 
that  conveys  the  external  air  to  the  middle  ear. 

"We  will  glance  briefly  at  the  anatomical  characters  of  the  parts  enumerated, 
and  which  enter  into  the  formation  of  the  middle  ear. 

1.  The  Membrana  Tympani  (Fig.  515,  5). 

Situated  on  the  external  wall  of  the  middle  ear,  which  it  separates  from  the 
bottom  of  the  auditory  canal,  this  membrane  is  oval  in  shape  ;  its  greater  axis 
measures  11  mm.  It  is  thin  and  capable  of  vibrating.  Its  inner  face,  inclining 
inwards  and  slightly  convex,  is  adherent  to  the  handle  of  the  malleus.  Its. 
external  face — forming  the  bottom  of  the  auditory  canal — is  slightly  concave 
(towards  the  meatus).  The  circumference  is  fixed  in  a  bony  frame  named  the 
tympanal  circle,  which  is  sharply  defined,  but  incomplete  at  its  upper  part,  and 
enveloped  by  the  mastoid  cells,  the  cavities  of  which  radiate  around  this  circle. 

Although  very  thin,  this  membrane  is  composed  of  three  layers — a  middle^ 
of  a  fibrous  (and  muscular)  character  (fibres  radiating  towards  the  centre,  and 
also  circular)  ;  an  external — epidermic  ;  and  an  internal — the  mucous  membrane 
of  the  middle  ear.  It  has  vessels  and  nerves,  but  not  in  the  external  and  middle 
layers.  The  nerves  are  numerous,"  and  extend  to  the  epithehum.  (This- 
membrane  receives  those  vibrations  of  the  air  which  set  in  movement  the  chain 
of  bones  in  the  ear,  and  thus  propagates  them  to  the  fenestra  ovalis  and  labyrinth.) 

2.  The  Promontory,  Fenestra  Ovalis,  and  Fenestra  Rotunda  (Fig.  515). 

Placed  in  the  upper  part  of  the  tympanic  wall,  the  promontory  is  only  a  very 
small  eminence  separating  the  fenestra  rotunda  from  the  fenestra  ovalis.  (It  is 
marked  by  grooves  in  which  lie  the  branches  of  the  tympanic  nerves.) 

Th.Q  fenestra  ovalis  {fenestra  vestibuli),  situated  in  front  of  the  promontory,, 
is  an  opening  the  form  of  which  is  sufficiently  indicated  by  its  name.  It  is  the 
opening  between  the  tympanum  and  osseous  vestibule,  and  is  closed  by  the  base 
of  the  stapes.     In  the  Horse,  its  average  diameters  are  '004  by  -002  mm. 

The  fenestra  rotunda  {fenestra  cochlece)  is  separated  from  the  preceding  by 
the  promontory,  and,  behind  this  small  projection,  it  is  closed  in  the  fresh  state 
by  a  thin  membrane  (m.  tympani  secundaria),  that  forms  a  kind  of  diaphragm 
between  the  middle  ear  and  the  tympanic  scala  of  the  cochlea.  Its  dimensions 
are  about  the  same  as  those  of  the  fenestra  ovalis.  (The  aqueduct  of  Fallopius 
is  a  canal  commencing  at  the  internal  ear,  passing  above  the  fenestrfea  and 


THE  AUDITORY  APPARATUS. 


953 


promontory,  and  terminating  at  the  mastoid  foramen.     It  contains  the  facial 
nerve  which  passes  through  the  tympanic  cavity.) 

3.  The  Mastoid  Cells  (Fig.  515,  G). 

These  cells  occupy  all  the  circumference  of  the  tympanic  cavity,  except  above. 
They  are  small,  more  or  less  irregular,  deep  spaces,  separated  by  thin  partitions 

Fig.  515. 


RIGHT  TYMPANIC   CAVITY   OF   THE    HORSE'S   EAR   (ANTERIOR   PLANE,    VERTICAL    AND 
TRANSVERSE   SECTION). 

At  Auditory  canal;  B,  membrana  tympani;  C,  malleus;  D,  incus;  E,  os  orbiculare;  F,  stapes;  G, 
mastoid  cells ;  H,  fenestra  ovalis  ;  I,  vestibule  ;  /,  K,  L,  outline  of  the  semicircular  canals  ;  i/, 
cochlea ;  N,  commencement  of  the  tympanic  scala. 


radiating  around  the  tympanic  circle,  their  free  margin  being  turned  towards  the 
centre  of  the  cavity. 

In  several  animals,  and  particularly  the  Carnivora,  the  mastoid  cells  form  a 
special  compartment  in  the  tympanic  case,  communicating  with  the  latter  by 
a  single  opening.  The  largest  are  situated  at  the  inferior  part  of  the  tympanic 
oavity,  below  the  vaginal  process  of  the  temporal  bone.  (In  the  Sheq)  and 
-Goat,  the  mastoid  cells  and  their  bony  septa  are  entirely  absent.) 

4.  The  Bones  of  the  Middle  Ear  (Fig.  516). 
Four  articulating  bones  (the  ossicula  auditus),  named  the  malleus,  incus,  os 


954 


TEE  SENSORY  APPARATUSES. 


orliculare,  and  stapes,  compose  the  bony  chain  of  the  middle  ear ;  this  chain 
extends  in  a  broken  course  from  the  external  to  the  internal  wall  of  the 
tympanum.  The  pieces  are  movable  on  each  other,  and  are  joined  by  ligaments 
and  moved  by  muscles. 

1.  Malleus  {hammer). — This  is  the  longest  of  the  bones — average  length, 
•Oil  mm. — and  offers  a  handle  and  a  head,  which  almost  equally  divide  it.  The 
ha?idle  (manubrium)  is  placed  almost  vertically,  and  is  firmly  fixed  to  the  inner 
face  of  the  membrana  tympani.  The  head,  directed  upwards,  has  a  diarthrodial 
facet  for  articulation  with  the  incus.     The  neck,  or  upper  part  of  the  handle, 

Fig.   516. 


BONES   OF   THE   MIDDLE    EAR  OP   THE   HORSE. 

M,  Malleus:  1,  handle;  2,  head.  E,  Incus:  1,  inferior  branch;  2,  superior  branch;  3,  body.  L| 
Os  orbiculare.  Et,  Stapes:  1,  summit;  2,  2,  branches;  3,  base.  Me,  Muscle  of  the  stapes;  o, 
bony  nucleus  in  the  terminal  tendon. 


shows  two  small  processes  for  insertion  (processes  gracilis  and  hrevis),  the  inner- 
most of  which  is  very  developed. 

2.  Incus  (anvil). — This  bone  presents  a  body  or  middle  portion,  and  two 
branches.  The  body  is  channeled  externally  by  a  diarthrodial  facet,  corresponding 
with  that  on  the  malleus.  Of  the  two  branches,  the  superior  terminates  in  a 
blunt  point ;  while  the  other,  inferior,  is  united  at  its  extremity  to  the  os  orbiculare. 

3.  Os  Orbiculare. — This  is  a  little,  circular,  discoid  bone,  included  between 
the  inferior  branch  of  the  incus  and  stapes. 

4.  Stapes  (stirrup). — Remarkable  for  its  shape,  which  is  exactly  that  of  a 
stirrup,  this  bone  is  placed  almost  horizontally.  Its  summit  (or  head)  articulates 
with  the  OS  orbiculare  ;  its  middle  part  is  divided  into  two  branches,  having 
between  them  an  aperture  that  is  closed  by  the  tympanic  mucous  membrane. 
Its  base  is  received  into  the  fenestra  ovalis,  and  resembles  that  cavity  in  shape  ; 
and  it  is  maintained  in  its  position  by  the  mucous  lining  of  the  tympanum,  which 


TEE  AUDITORY  APPARATUS.  955 

passes  over  the  stapes,  after  being  reflected  around  the  margin  of  the  fenestra 
ovalis. 

(These  bones  transmit  the  vibrations  of  the  membrana  tympani  to  the  fluid 
in  the  labyrinth.) 

5.  Ligaments  of  the  Auditory  Bones. — We  need  only  mention  the 
existence  of  these  here,  as  they  are  too  small  and  unimportant  to  merit  a 
particular  description. 

6.  Muscles  of  the  Auditory  Bones. — Four  muscles  have  been  described  : 
three  for  the  malleus,  and  one  for  the  stapes.  But  two  of  these  being  extremely 
small,  and  their  muscular  character  doubtful  to  many  anatomists,  we  will  only 
notice  the  internal  muscle  of  the  malleus  and  that  of  the  stapes. 

a.  The  internal  muscle  of  the  malleus  {tensor  tympani,  musculus  internum 
mallei). — This  is  a  little  elongated  fasciculus,  lodged  in  a  particular  groove  in 
the  mastoid  portion  of  the  temporal  bone.  It  arises  near  the  superior  extremity 
of  the  Eustachian  tube,  and  passes  downwards  and  backwards,  to  terminate  by 
a  tendon  which  is  reflected  outwards,  in  front  of  the  fenestra  ovalis,  and  is 
inserted  into  the  neck  of  the  malleus. 

h.  Muscle  of  the  stapes  {stapedius). — Lodged  in  an  excavation  in  the  inner 
wall  of  the  tympanum,  near  the  fenestra  vestibuli,  on  the  course  of  the  aquaeductus 
Fallopii,  this  muscle  is  remarkable  for  its  brevity,  its  relatively  considerable 
thickness,  and  its  conical  shape.  It  terminates  by  a  small  tendon  in  front  of  the 
head  of  the  stapes.  In  the  Horse,  Ox,  and  Sheep,  a  small  bony  nucleus  is  found 
in  the  tendon  (Fig.  516,  o). 

(The  tensor  tympani  retracts  the  bones  of  the  ear  inwards.  In  contracting 
it  draws  the  handle  of  the  malleus  towards  the  cavity  of  the  tympanum,  and 
this  brings  the  membrane  with  it ;  consequently,  the  convexity  of  the  latter  is 
increased  and  its  tension  is  augmented.  In  addition,  while  the  handle  of  the 
malleus  is  carried  inwards,  its  head  is  turned  outwards  by  a  pivoting  motion,  and 
this  pulls  the  body  of  the  incus  also,  the  long  process  of  which  is  raised  and 
inclined  inwards,  pushing  the  os  orbiculare  and  stapes  towards  the  fenestra 
ovaHs.  The  base  of  the  latter  bone  being  in  contact  with  the  fluid  in  the 
vestibule,  this  is  stirred  ;  so  that  this  muscle  likewise  acts  indirectly  in  producing 
the  undulations  in  this  fluid.  The  muscles  of  the  tympanum  are  classed  as 
tensors  and  laxators.  It  is  well  to  know  that  all  are  tensors,  and  none  of  them 
act  as  relaxors  ;  relaxation  of  the  membrane  occurring  when  the  muscles  are  not 
in  action.)  ' 

5.  The  Mucous  Membrane  of  the  Tympanum. 

Very  fine  and  vascular,  this  membrane  covers  all  the  angularities  of  the 
middle  ear,  is  reflected  on  the  chain  of  bones,  and  is  continued  into  the  mastoid 
cells.  It  is  continuous  with  that  lining  the  Eustachian  tube,  and  therefore 
should  be  considered  as  a  prolongation  of  the  tegumentary  membrane  spread 
over  the  walls  of  the  pharyngeal  vestibule.  It  is  covered  by  a  simple  pavement 
epithelium. 

6.  The  Eustachian  Tube. 

The  Eustachian  tuhe  is  a  fibro-cartilaginous  canal  between  the  cavity  of  the 
middle  ear  and  the  pharynx. 

«  Extending  in  a  straight  line  beneath  the  base  of  the  cranium,  from  the 
tympanic  case  to  the  upper  and  lateral  part  of  the  pharyngeal  cavity,  this  canal 


956  THE  SENSORY  APPARATUSES. 

i«  also  named  the  guttural  duct  of  the  tympanum.  It  is  nearly  four  inches  long 
in  Solipeds,  is  flattened  on  both  sides,  and  bordered  by  the  stylo-pharyngeus 
muscle.  Its  upper  or  tympanic  orifice  is  narrow ;  the  inferior,  guttural,  or 
pharyngeal  orifice,  situated  near  and  behind  the  guttural  openings  of  the  nasal 
cavities,  is  wide,  and  represents  a  great  slit  extending  obliquely  downwards 
and  outwards ;  the  contiguous  borders  of  this  aperture  are  sustained  by  a 
cartilaginous  plate — a  kind  of  pavilion  formed  by  the  expansion  of  the  tissue 
•constituting  the  base  of  the  tube. 

Throughout  its  length,  the  guttural  duct  is  cleft  inferiorly,  and  by  this 
long  aperture  the  mucous  membrane  escapes  and  descends  to  form  the  large  sac 
peculiar  to  Monodactyles,  known  as  the  guttural  pouch. 

7.  The  Guttueal  Pouches. 

The  mucous  membrane  lining  the  Eustachian  tube  is  continuous,  forward, 
with  that  of  the  pharynx  ;  above  and  behind,  it  is  prolonged  into  the  tympanic 
cavity,  which  it  lines.     Below,  it  is  dilated,  and  forms  the  guttural  pouch. 

Two  in  number — one  being  on  each  side — the  guttural  pouches  lie  against  each 
other  in  the  median  plane,  and  descend  to  the  larynx,  where  they  terminate  in  a 
cul-de-sac  constituting  their  fu7idus.  Before  and  behind,  they  extend  from  the 
anterior  part  of  the  pharynx  to  the  inferior  face  of  the  atlas.  The  capacity  of 
«ach  is  about  f  of  a  pint ;  but  in  consequence  of  the  extensibility  of  the  mucous 
membrane,  the  extent  and  capacity  of  the  guttural  pouches  are  particularly  variable. 

Irregular  in  shape,  like  the  space  which  it  occupies,  the  guttural  pouch 
corresponds,  behind  and  above,  with  the  base  of  the  occipital  and  sphenoid  bones. 
When  this  reservoir  is  distended,  its  lower  part,  or  fundus,  descends  on  the 
lateral  portions  of  the  pharynx  and  larynx,  to  the  lower  extremity  of  the  parotid 
gland,  in  the  loose  connective  tissue  of  that  region. 

Externally,  the  guttural  pouch  contracts  numerous  different  relations  in  the 
intermaxillary  and  parotideal  regions,  and  in  its  j^osterior  portion. 

a.  In  the  intermaxillary  region,  it  is  in  relation  with  the  tensor  palati, 
pterygoideus  and  hyo-pharyngeus  muscles,  as  well  as  with  the  internal  maxillary 
artery  and  lingual  nerve  ;  it  envelops  the  large  cornu  of  the  hyoid  bone,  and 
covers  the  inner  face  of  the  internal  pterygoideus  muscle. 

b.  In  the  parotideal  region,  the  guttural  pouch  responds,  above,  to  the  inner 
face  of  the  parotid  gland,  from  which  it  is  separated  by  the  auricular  vessels  and 
nerves ;  a  httle  lower,  at  the  posterior  angle  of  the  hyoid  bone,  to  the  stylo- 
hyoideus  muscle  and  the  styloid  process  of  the  occipital  bone  ;  here  the  auricular 
artery  passes  obliquely  upwards  and  backwards,  and  the  membrane  of  the  pouch 
is  more  closely  united  to  the  parts  covering  it. 

Below  this,  the  guttural  pouch  is  in  relation  with  the  stylo-maxillaris  muscle, 
external  carotid,  and  the  nerves  forming  the  guttural  plexus  such  as  the  ninth 
and  twelfth  pairs,  the  sympathetic,  etc.  Lower,  it  is  related  to  the  parotid  gland, 
to  the  inferior  extremity  of  which  it  may  be  prolonged. 

c.  Posteriorly. — The  guttural  pouch  is  in  relation  with  the  atlas,  flexor 
muscles  of  the  head,  occipital  artery,  etc. ;  it  forms  a  fold  that  envelops 
principally  the  pneumogastric  and  sympathetic  nerves,  and,  anteriorly,  another 
fold  that  encloses  the  internal  carotid. 

The  mucous  membrane  of  the  guttural  pouches  is  thicker  and  stronger  than 
that  hning  the  Eustachian  tube  and  the  cavity  of  the  tympanum.  Only  slightly 
adherent  to  the  adjacent  parts,  except  at  the  branch  of  the  hyoid,  the  inner  face 


THE  AUDITORY  APPARATUS.  ■         957 

of  the  stylo-hyoideus,  etc.,  it  is  smooth  internally,  and  lubriiied  by  the  mucus  it 
secretes.  It  may  become  the  seat  of  purulent  collections,  which  compress  the 
larynx  and  obstruct  the  respiration,  and  it  is  in  such  cases  that  the  pouch  is 
punctured.^ 

This  membrane  receives  numerous  fine  vascular  and  nervous  ramifications 
from  the  neighbouring  branches. 

The  guttural  pouches  communicate  with  the  pharynx  and  cavity  of  the 
tympanum,  and  usually  contain  air ;  the  quantity  of  this  may  vary  in  health, 
according  to  the  degree  of  dilatation  of  these  membranous  sacs.  Their  dilatation 
is  chiefly  produced  by  the  palato-pharyngeus  muscle,  several  fibres  from  which 
extend  to  their  mucous  membrane  ;  and,  besides,  when  the  ear  is  erected  this 
membrane  is  thrown  into  a  state  of  tension,  through  the  adhesion  of  the  lower 
prolongation  of  the  concha  to  its  surface. 

The  functions  of  the  guttural  pouches  are  far  from  being  well  known.  It 
cannot  be  affirmed  that  they  increase  phonation  ;  indeed,  their  use  appears  to  be 
rather  related  to  audition,  if  it  be  considered  that  these  annexes  of  the  guttural 
duct  of  the  tympanum  coincide,  in  Sohpeds,  with  a  less  development  of  the 
mastoid  cells  than  in  the  other  animals. 

With  regard  to  the  Eustachian  tube,  it  serves  to  renew  the  air  in  the  tympanic 
cavity,  this  renewal  being  indispensable  to  the  perfect  accomplishment  of  hearing. 

The  epithelium  lining  the  guttural  pouches  is  cylindrical  and  vibratile. 

(It  is  essential  that  the  equilibrium  between  the  external  air  and  that  in  the 
cavity  of  the  tympanum  should  be  maintained,  in  order  to  avert  irregular  tension, 
or  even  rupture,  of  the  membrana  tympani.  Perosino  states  that  the  guttural 
pouches  are  filled  with  warm  air  during  expiration,  and  that  this  is  partly  changed 
for  cold  air  in  inspiration.) 

Aeticle  III. — The  Exteenal  Eae. 

The  external  ear  comprises  the  external  auditory  canal,  and  a  widened  appen- 
dage opening  outwardly,  designated  the  concha,  or  imvilion. 

The  External  Auditory  Canal. 

This  canal  {meatus  auditorius  externus),  described  in  the  Osteology,  is,  in  the 
Horse,  of  a  cylindro-conical  shape,  and  has  an  average  width  of  '020  to  '022  m. 
It  has  at  the  bottom  the  membrana  tympani,  which  separates  it  from  the  middle 
ear.  Its  axis  forms  with  the  surface  of  that  membrane  an  angle  of  about  30°. 
Its  entrance — the  external  auditory  hiatus — gives  attachment  to  the  infundi- 
bulum  of  the  conchal  apparatus.  It  is  lined  by  a  thin  integumentary  membrane, 
intermediate  in  character  between  the  skin  and  mucous  membrane,  and  has 
in  its  substance  a  large  number  of  glands  and  convoluted  tubes,  analogous  to 
the  sudoriparous  glands — but  here  named  ceruminous  glands,  as  they  secrete  an 
unctuous  matter — the  cerumen. 

The  Concha,  or  Pavilion. 

The  external  trumpet-shaped  appendage  named  the  concha  (concha  auris) 
varies  much  in  shape  in  the  different  animals,  though  in  all  it  offers  the  same 
details   in  organization — a   cartilaginous  framework  composed  of   three  pieces, 

'  Bartheleray,  sen.,  and  Goubaux,  have  found,  in  the  guttural  pouches,  solid  masses  formed 
of  mucus  and  epithelial  cells. 
63 


958  TEE  SENSORY  APPARATUSES. 

muscles  to  move  these,  an  adipose  cushion  to  ensure  liberty  of  movement,  and 
integuments  covering  the  whole. 

1.  Caetilages  of  the  Concha  (see  p.  281). 

2.  Muscles  of  the  Exteenal  Eae  (see  p.  281). 

3.  Adipose  Cushion  of  the  Exteenal  Eae. 

This  cushion,  which  is  never  absent — even  in  the  most  emaciated  animals- 
envelops  the  base  of  the  concha  in  front,  inwardly,  and  posteriorly.  It  facilitates 
the  movements  of  that  organ. 

4.  Integuments  of  the  Exteenal  Eae. 
The  skin  covering  the  concha  is  covered  with  fine  close  hairs.     That  lining 
its  interior  is  very  thin  and  vascular,  adheres  closely  to  the  cartilage,  and  is 
furnished  with  long  silky  hairs,  to  prevent  the  entrance  of  dust  into  the  ear. 

Differential  Chakactebs  in  the  Auditory  Apparatus  of  other  than  Soliped  Animals, 

In  the  various  kinds  of  animals  we  study,  there  are  no  notable  differences  in  the  internal  ear. 

In  the  middle  ear,  there  are  some  modifications,  either  in  the  bones  or  accessory  parts.  Id 
Ruminants,  the  auditory  bones  are  like  those  of  the  Horse,  except  that  the  handle  of  the 
malleus  is  more  curved,  and  the  body  of  the  incug  is  longer.  In  the  Dog,  the  handle  of  the 
malleus  is  covered  with  small,  pointed  processes,  and  the  branches  of  the  stapes  are  long  and 
thick.  In  the  Pig,  the  branches  of  the  latter  are  slight  and  inflected,  and  the  base  is  wide 
and  thin;  in  a  word,  the  stapes  of  this  animal  bears  no  resemblance  to  a  stirrup;  the  malleua 
is  very  much  inflected  forward.  In  the  last  two  animals,  no  osseous  nucleus  is  found  in  the 
tendon  of  the  stapedian  muscle. 

It  is  needless  to  say  that  the  fenestra  ovalis  varies  with  the  base  of  the  stapes.  (The 
absence  of  the  mastoid  cells  in  the  Sheep  and  Goat  has  been  already  noted.) 

The  Eustachian  tube  exists  in  all  the  animals,  but  tiie  guttural  pouches  are  only  found  in 
Solipeds. 

In  the  external  ear,  the  conchal  cartilage  varies  much  in  shape.  It  is  thin,  inclined  out- 
wards, and  widely  open  in  Ruminants.  In  the  Pig,  it  differs  a  little,  according  to  breed, 
though  it  is  always  much  developed,  sometimes  erect,  but  most  frequently  drooping.  In  the 
Dog,  it  is  sometimes  short  and  erect,  sometimes  broad  and  pendulous.  It  is  always  short, 
pointed,  erect,  and  open  in  front,  in  the  Cat.  (In  this  animal  a  small  duplicature  of  the 
external  margin  of  the  concha  is  often  seen.)  In  Birds,  the  external  ear  is  limited  to  the 
auditory  canal. 

Comparison  between  the  Auditory  Apparatus  in  Man  and  that  op  Animals. 

There  is  nothing  to  be  said  regarding  the  internal  ear.  The  middle  ear  comprises  the 
same  parts  as  that  of  Mammifers  other  than  Solipeds.  Tlie  handle  of  the  malleus  is  straighter, 
the  incus  more  voluminous,  and  the  stapes  thinner,  proportionately,  than  in  animals.  There 
is  no  bony  nucleus  in  the  stapedian  muscle.  The  muscle  of  the  malleus  is  lodged  in  a  distinct 
canal  belonging  to  the  Eustachian  tube. 

The  external  ear  is  composed  of  only  two  cartilages :  one,  forming  the  base  of  the  concha, 
represents  that  cartilage  in  animals ;  the  other,  belonging  to  the  auditory  canal,  resembles  the 
annular  cartilage  in  the  Horse.  The  concha  is  very  irregular  in  shape,  and  stands  at  an  angle 
of  from  15°  to  45°  from  the  temporal  bone ;  it  is  convex  superiorly,  and  terminates  inferiorly 
by  a  small  lobe.  On  its  anterior  face  it  presents  prominences  and  depressions;  the  former  are 
four  in  number:  the  helix,  a  fold  encircling  the  ear  behind  and  above;  the  antihelix,  a  con- 
centric prominence,  almost  parallel  with  the  preceding;  the  tragus,  a  triangular,  pointed 
process,  covered  with  hair,  situated  in  front  of  the  auditory  canal  (meatus);  the  antitragus, 
opposite  the  tragus,  behind  the  canal,  and  above  the  lobule.  The  depressions  are  :  the  concha, 
a  wide  cavity,  limited  by  tlie  antihelix ;  the  scaphoid  fossa  (fossa  innnminata)  situated  above 
the  latter;  and  the/o88a  triangularis  comprised  between  the  helix  and  antihelix. 

The  pavilion  of  the  ear  is  traversed  by  several  muscular  fasciculi,  which  can  have  no 
influence  on  its  movements.  The  concha  has  also  extrinsic  muscles — the  anterior  auricu- 
htris  (attrahens  aurem),  auricularis  superioris  (attolens  aurem),  and  the  auricularis  posteriores 
(retrahens  aurem).     The  action  of  these  on  the  concha  is  very  slight. 


BOOK  YIII. 

GENERATIVE   APPARATUS. 

Individuals  in  the  organic  kingdom  possess  the  faculty  of  reproduction,  and 
thus  they  perpetuate  the  species  to  which  they  belong.  In  Mammifers,  the 
generation  of  a  new  being  demands  the  concurrence  of  two  individuals — a  male 
and  female— y^ho  have  intercourse  under  certain  determinate  circumstances. 
The  female  furnishes  a  germ — the  ovum,  and  the  male  a  fertilizing  fluid — the 
semen,  which  vivifies  the  ovum,  and  renders  it  capable  of  development. 

We  have,  therefore,  to  study  separately  the  generative,  or  genital  organs  of  the 
male,  and  those  of  the  female. 


CHAPTER  1. 

GENITAL  ORGANS  OP  THE  MALE. 

The  semen  is  elaborated  in  the  structure  of  the  two  testicles.  These  are  lobular 
glands,  each  of  which  is  provided  with  an  excretory  duct,  doubled  a  great  number 
of  times  on  itself  at  its  commencement,  to  form  the  epididymis,  and  destitute  of 
convolutions  for  the  remainder  of  its  extent,  which  is  named  the  vas  deferens. 
This  canal  carries  the  fecundating  fluid  into  vesiculm  seminales — reservoirs  with 
contractile  walls — where  it  accumulates,  and  wnence  it  is  expelled  during  copu- 
lation, by  passing  through  the  ejaculatory  ducts  and  the  urethral  canal.  The 
latter  is  a  single  canal  common  to  the  two  apparatuses  of  generation  and  urinary 
depuration  ;  it  is  provided  in  its  course  with  three  accessory  glands — the  prostate 
and  Coivper's  glands,  and  is  supported  by  an  erectile  body  (the  corpus  cavernosum), 
with  which  it  forms  an  elongated  organ — the  penis,  which,  in  the  act  of  copu- 
lation, is  introduced  into  the  vagina,  to  the  bottom  of  which  it  carries  the 
spermatic  fluid. 

We  will  successively  consider  the  secretory  organs  or  testicles,  and  the  excretory 
apparatus,  comprising  all  the  other  organs. 

Preparation. — To  see  the  arrangement  of  the  male  generative  organs  properly,  it  is  necessary 
to  dissect  them  in  situ,  and  then  remove  them  from  the  pelvis  in  order  to  examine  them 
thoroughly. 

The  subject  in  which  the  organs  are  to  be  examined  in  situ  should  have  the  skin  removed 
from  it,  except  at  the  parinseum,  scrotum,  a  portion  of  the  inner  face  of  the  thighs,  and  the 
inferior  surface  of  the  abdomen,  from  a  transverse  line  passing  from  one  haunch  to  the  other. 
The  intestines  are  taken  from  the  abdominal  cavity,  by  dividing  its  walls  in  front  of  that  line; 
the  left  posterior  limb  is  removed,  leaving  the  sacro-sciatic  ligament  which  is  behind  it. 
Finally,  after  distending  the  rectum  and  bladder,  which  have  previously  been  emptied — the 
first  with  tow,  the  second  with  air  introduced  by  the  ureter,  wiiich  is  then  tied  on  itself— the 
dissection  of  the  internal  genital  organs  can  be  proceeded  with.     This  dissection  is  carried 


960  GENERATIVE  APPARATUS. 

out  as  for  as  the  bladder  and  anus,  the  cellulo-adipose  tissue  being  removed  from  the  bottom 
of  the  pelvis,  taking  care  to  leave  the  peritoneum,  where  it  passes  on  to  the  pelvic  organs.  The 
portion  of  the  ischium  to  which  no  organ  required  tor  this  study  is  attached,  may  be  sawn  off. 

In  detaching  the  skin  from  the  inner  surface  of  the  thigh,  and  as  far  as  the  middle  line, 
the  fixed  portion  of  the  penis  and  one  of  the  dartos  sacs  are  exposed.  The  separation  of  the 
scrotum  from  the  dartos  is  a  laborious  operation,  because  of  the  fineness  and  the  adherence  of 
the  skin;  it  ought  to  be  effected  by  means  of  a  good  scalpel,  and  with  every  precaution.  Tlie 
preparation  is  completed  by  dissecting  the  suspensory  ligaments  of  the  corpus  cavernosum,  the 
penis,  and  the  prepuce  (sheath),  about  which  tiiere  is  no  difficulty. 

(The  dartiis  and  other  layers  within  tlie  scrotum  are  more  easilly  dissected,  if  the  skin  be 
drawn  tight  over  the  testicle  and  tied  between  tlie  latter  and  the  abdomen,  so  as  to  keep  it 
tense  on  the  surface  of  the  organ.) 

The  Testicles,  or  Secretory  Organs  of  the  Semen. 

The  testicles  (testes)  are  two  glands  suspended  on  each  side  of  the  penis, 
between  the  thighs,  where  each  occupies  a  particular  serous  pouch — the  tunica 
vaginalis.  We  will  commence  by  describing  this  cavity,  and  afterwards  the 
organ  it  contains. 

1.  Tunica  Vaginalis. 

The  tunica  vaginalis,  in  the  domesticated  animals,  is  only  a  diverticulum  of 
the  abdominal  cavity,  the  serous  membrane  of  which — the  peritoneum — becomes 
hernied  in  the  inguinal  canal — passing,  as  it  does,  through  the  upper  (internal) 
inguinal  ring,  and  prolonged  belov\^  the  inferiui  (external)  ring,  so  as  to  form  a 
serous  sac,  which  is  enveloped  by  membranous  walls. 

We  have  to  study,  in  the  tunica  vaginalis  :  1.  Its  interior.  2.  The  enveloping 
memhranes  which  form  the  external  wall,  and  to  which  we  give  the  common 
name  of  scrotum. 

Interior. — The  serous  sac  constituting  the  tunica  vaginalis  is  vertically 
elongated,  and  slightly  inclined  downwards,  inwards,  and  backwards.  Its 
inferior  extremity,  forming  the  bottom,  or  cul-de-sac,  is  pear-shaped,  and  lodges 
the  testicle  and  its  epididymis.  Its  middle  portion,  contracted  into  a  narrow 
canal,  contains  the  spermatic  cord.  The  superior  extremity,  or  entrance,  is  open, 
to  maintain  communication  with  the  abdominal  cavity ;  through  it  pass  the 
spermatic  vessels  and  vas  deferens.^ 

As  has  been  said,  the  peritoneum  forms  this  vaginal  sac.  As  in  the  abdomen, 
it  is  divisible  into  two  hjers— parietal  and  visceral.  The  latter  {tunica  vaginalis 
propria)  covers  the  testicle  and  the  cord  ;  while  the  former  {tunica  vaginalis 
communis,  or  reflexa)  lines  the  innermost  of  the  membranous  coverings  which 
serve  as  a  wall  to  the  tunica  vaginalis.  These  two  layers  are  made  continuous 
by  a  serous  frsenum,  analogous  to  the  mesentery  which  sustains  the  floating 
colon ;  like  it,  it  is  formed  by  the  junction  of  the  two  layers.  Flat,  elongated 
from  above  to  below,  and  extending  vertically  from  one  end  of  the  sac  to  the 
other,  this  fraenum  is  attached,  by  its  upper  border,  behind  the  spermatic  cord  ; 
its  lower  extremity  passes  over  the  epididymis,  and  from  it  on  to  the  testicle ; 
above,  it  is  continued  into  the  abdominal  cavity,  in  accompanying  the  different 
vessels  composing  the  cord. 

(A  small  quantity  of  serous  fluid  is  usually  present  in  the  tunica  vaginalis. 
When  in  excess  it  gives  rise  to  hydrocele.) 

Enveloping  Membranes. — The  stratified  layers  that  form  the  external  walls 

'  If  this  opening  be  abnormally  dilated,  a  loop  of  intestine  may  enter  it,  and  lie  alongside 
the  testicle  in  the  sac,  constituting  inguinal  hernia. 


TEE  GENITAL   ORGANS  OF  TEE  MALE.  961 

of  this  vaginal  membrane — and  which  are  generally  described  in  anatomical 
treatises,  with  the  two  serous  layers,  as  the  envelopes  of  the  testicle — are  four  in 
number.  Reckoning  them  from  within  to  without,  they  are  the  fibrous  tuny,, 
cremaster  muscle,  dctrtos,  and  scrotwn. 

Fibrous  Tunic  {infuadibulform  fascia). — This  forms  the  most  complete 
covering  to  the  tunica  vaginalis,  extending,  as  it  does,  over  the  whole  surface 
of  the  parietal  serous  layer,  to  which  it  is  closely  adherent.  Very  thin,  especially 
at  the  points  corresponding  to  the  cremaster,  this  membrane  is  continuous, 
around  the  upper  inguinal  ring,  with  the  transversalis  fascia,  of  which  it  is  only 
a  dependency  ;  its  external  face  is  in  relation  with  the  cremaster  and  dartos. 

Cremaster  (or  cremasteric  fascia). — This  .muscle  is  usually  described  as  an 
envelope  of  the  testicle,  by  the  name  of  tunica  erythroides.  In  the  domesticated 
animals  it  is  a  bright-red  band,  attached,  above,  to  the  inner  or  peritoneal  sur- 
face of  the  ilio-lumbar  aponeurosis  ;  it  descends  into  the  inguinal  canal,  envelops 
outwardly  only  the  middle  portion  of  the  tunica  vaginalis,  and  expands  below  on 
the  ctd-de-sac,  where  its  fibres  terminate  by  small  tendons,  which  are  inserted 
into  the  external  surface  of  the  infundibuliform  fascia.  Therefore  it  is  that 
the  envelope  the  cremaster  forms  is  very  incomplete — the  greater  portion  of  the 
testicle,  and  the  inner  side  of  the  cord,  being  left  unprotected  by  this  muscular 
tunic.  It  is  in  relation,  inwardly,  with  the  fibrous  membrane,  to  which  it  is 
united  by  a  plentiful  connective  tissue  ;  externally,  it  is  related  to  the  posterior 
wall  of  the  inguinal  canal  and  the  dartos.  (It  is  a  connective  dependency  of 
the  internal  oblique  muscle.) 

It  is  the  contraction  of  the  cremaster  that  causes  the  sudden  ascent  of  the 
testicle. 

Dartos. — The  tissue  composing  this  tunic  is  contractile  ;  it  is  constituted  by 
a  mixture  of  elastic  tissue  and  unstriped  muscular  fibres.  The  dartoi'c  tunic 
does  not  reach  the  inguinal  canal ;  consequently,  it  does  not  cover  that  part  of 
the  tunica  vaginalis.  It  forms  a  pouch  below  the  inguinal  ring,  and  is  spread 
from  around  the  margin  of  this  on  to  the  neighbouring  parts,  to  which  it  adheres 
somewhat  closely  ;  it  is  prolonged,  gradually  thinning,  into  the  sheath  of  the 
penis,  and  even  on  to  the  penis  itself,  and  to  the  tunica  abdominalis,  as  well  as 
between  the  thighs.  The  two  pouches  it  forms  are  quite  independent  of  each 
other,  never  becoming  confounded,  though  placed  in  contact  on  the  mesial  line 
to  form  a  double  partition  (septum  scroti),  the  leaves  of  which  are  separated 
above  for  the  passage  of  the  penis.  The  dartos  is  in  relation,  inwardly,  with 
the  fibrous  and  erythroid  tunics,  from  which  it  is  isolated  by  an  abundance  of 
lamellar  connective  tissue,^  which  is  very  condensed  towards  the  globus  major 
epididymis,  and  forms  at  this  point  a  kind  of  cord  that  passes  from  the  fibrous 
tunic  to  the  dartos,  adhering  strongly  to  each.  Externally,  the  dartos  is  covered 
by  the  scrotum. 

This  tunic  determines  the  vermicular  movements  of  which  the  scrotum  is 
the  seat.  It  wrinkles  the  skin  of  the  scrotum,  and  makes  it  firm  and  dense,  thus 
aiding  the  cremaster  in  raising  the  testicle.  When  it  is  not  in  a  state  of  con- 
traction, the  skin  of  the  scrotum  is  smooth  and  even,  and  the  testicle  pendulous. 

Scrotum. — The  different  membranes  enumerated  above  are  double,  one 
being  for  each  tunica  vaginalis  ;  but  the  scrotum  constitutes  a  single  pouch, 
enveloping  the  two  testicles  at  the  same  time.     It  is  merely  the  portion  of  skin 

'  The  testicle  is  disengaged  by  tearing  tlirough  this  tissue,  in  castration  by  the  "  covered 
operation." 


962  GENERATIVE  APPARATUS. 

covering  this  region,  and  is  thin,  and  so  closely  adherent  to  the  dartos  that  it 
can  only  with  difficulty  be  separated  from  it.  It  is  covered  by  very  short  fine 
hair,  and  the  extremely  nmnerous  sebaceous  follicles  in  its  texture  secrete  an 
unctuous  matter  that  renders  its  surface  soft  to  the  touch. 

(There  are  also  numerous  sudoriparous  glands,  and  these,  with  the  sebaceous 
glands,  keep  the  skin  soft  and  pUable,  and  modify  the  effects  of  friction  during 
progression.  On  its  surface  it  shows  a  7-aphe  or  seam  in  the  middle,  which  is  a 
trace  of  its  primary  division,  and  corresponds  to  the  median  septum  separating 
the  testicles.) 

2.  The  Testicles  (Figs.  517,  518,  519,  521). 

External  Conformation. — Each  testicle  is  oval  in  shape,  flattened  on  both 
sides,  lodged  in  the  cul-de-sac  of  the  tunica  vaginalis,^  and  suspended  at  the 
extremity  of  the  spermatic  cord.  The  description  of  this  organ  is  extremely 
simple  ;  it  offers  for  study  two  faces,  two  borders,  and  two  extremities. 

The  faces,  external  and  internal,  are  smooth  and  round.  The  inferior  border 
is  convex  and  free,  like  the  faces  ;  the  supeiHor,  ahnost  straight,  is  related  to  the 
epididymis,  which  adheres  to  it  by  its  head  and  tail. 

Means  of  Attachment. — The  testicle  is  freely  pendent  in  the  lower  part  of  the 
tunica  vaginalis,  where  it  cannot  readily  be  displaced,  because  of  the  narrowness 
of  the  space  containing  it.  It  is  suspended,  by  its  upper  border,  to  the  testicular 
or  spermatic  cord -."^  a  thick  funiculus  contained  in  the  middle  portion  of  the 
vaginal  sheath,  and  formed  by  the  aggregation  of  the  spermatic  vessels  with 
the  vas  deferens. 

This  cord  is  itself  sustained  in  the  tunica  vaginalis  by  the  frsenum  that  unites 
the  two  serous  tunics  of  that  cavity. 

Steucture. — Independently  of  the  serous  tunic  that  covers  the  exterior  of 
the  testicle,  there  enter  into  its  structure  a  fibrous  membrane,  tissue  proper,  and 
vessels  and  nerves.     The  excretory  duct  will  be  studied  separately. 

Fibrous  Membrane. — This  membrane,  designated  the  tunica  albuginea,  forms 
a  strong,  resisting,  thick  shell  around  the  testicle,  and  its  texture  is  channeled 
by  sinuous  spaces  which  lodge  the  large  spermatic  vessels.  It  is  covered  by  the 
visceral  layer  of  the  tunica  vaginalis,  to  which  it  closely  adheres  ;  its  inner  face 
sends  thin  septa  into  the  proper  substance  of  the  gland,  which  divide  the  latter 
into  the  spermatic  lobules.  Towards  the  upper  border  of  the  testicle,  and  in 
front,  the  tunica  albuginea  is  slightly  thickened  ;  this  part  is  named  the  corpus 
Higmorianum  (or  mediastinum  testis),  and  at  this  point  the  seminal  ducts  pass 
through  it  to  reach  the  epididymis. 

(This  membrane  is  dense  and  inelastic,  being  composed  of  white  fibrous 
tissue  interlacing  in  every  direction.) 

Tissue  proper. — The  proper  substance  of  the  testicle  resembles  a  greyish- 
yellow  pulp,  contained  in  the  tunic  albuginea  ;  it  is  divided  by  the  prolongations 
which  that  tunic  sends  into  its  interior,  into  small,  conical,  distinct  lobules  {lobuli 

'  One  or  both  testicles  may  be  retained  in  the  constricted  portion  of  the  tunica  va^nalis, 
or  remain  in  the  abdomen  ;  animals  in  ■which  this  occurs  are  named  monorchids  or  cryptorchids. 
The  absence  of  one  or  two  testicles  (anorchidism)  is  extremely  rare.  Ectopix  of  the  testicles 
is  the  designation  applied  to  these  organs  when  they  are  found  elsewhere  than  in  the  ordinary 
situation. 

*  III  surgical  anatomy,  there  is  sometimes  included  in  the  spermatic  cord  the  middle 
portion  of  the  tunica  vaginalis  and  ail  its  envelopes — the  serous,  fibrous,  and  erythroid  tunics. 


THE  GENITAL   ORGANS  OF  THE  MALE. 


testis),  independent  of  each  other.  These  lobules  vary  in  number,  from  two  to 
three  hundred,  and  all  have  the  same  organization,  each  being  constituted  by 
two  or  three  extremely  convoluted  filiform  tubuli,  about  from  one  to  two  yards 
in  length.  These  tubes — the  tubuU  seminiferi — anastomose  frequently  with  each 
other,  are  intertwined,  and  can  be  unwound  like  a  ball  of  thread.  One  of  their 
extremities  terminates  in  a  cul-de-sac ;  the  other  is  detached  from  the  lobule, 
and  enters  a  central  system  of  excretory  ducts  which  will  be  referred  to  im- 
mediately. 

When  we  cut  through  a  testicle  vertically  and  lengthways,  so  as  to  divide 
the  corpus  Highmorianum  into  two  lateral  portions,  there  is  seen  in  its  substance 
a  whitish  framework,  sometimes  not  very  apparent,  which,  curving  upwards  at 
both  extremities,  extends  from  that  body  to  the  posterior  extremity  of  the  testicle 


Fig.  518. 


Fig.  517. 


DIAGRAM   OF   THE   TESTICLE. 

t,  Mediastinum  testis,  containing 
the  rate  testis ;  2,  2,  trabeculi ; 
3,  one  of  the  lobules  ;  4,  4,  vasa 
recta;  5,  globus  major;  6,  globus 
minor  ;  7,  vas  deferens. 


A   TESTICLE    INJECTED    WITH    MERCURY. 

,  a,  Lobules  formed  of  seminiferous  tubes ;  6,  rete 
testis;  c,  vasa  etferentia;  d,  ilexures  of  the  efferent 
vessels  passing  into  the  head,  e,  e,  of  the  epididy- 
mis ;  /,  body  of  the  epididymis ;  g,  appendix  ;  h, 
Cauda ;  i,  vas  deferens. 


{Fig.  518),  where  it  disappears  ;  from  this  are  given  off  a  large  number  of 
fibrillae  (trabeculce  testis),  which  diverge  in  all  directions.  A  mercurial  injection 
by  the  vas  deferens,  shows  that  this  part  of  the  testicle  is  chiefly  formed  by  a 
ramifying  system  of  rectilinear  canals  with  very  thin  walls,  which  open  into  each 
other,  and  unite,  on  reaching  the  corpus  Highmori,  into  about  twenty  principal 
trunks,  from 'S  mm.  to  '6  mm.  in  diameter.  These  are  named  the  straight  canaliculi 
{vasa  or  tuhuli  recti),  to  distinguish  them  from  the  convoluted  tubuli  (tubuU 
contorti)  ;  they  receive  the  latter  at  their  exit  from  the  lobules,  are  surrounded 
by  numerous  blood-vessels,  and  are  sustained  by  the  fibrous  septa  of  the  tunica 
albuginea,  which  appear  to  converge  towards  the  point  they  occupy.  At  the 
corpus  Highmorianum,  the  tubuli  recti  pass  through  that  body,  forming  in  its 
texture  an  anastomosing  network — the  rete  testis — and  are  contmued  into  the 
epididymis  as  the  efferent  canals  (vasa  efferentia). 


964 


GENERATIVE  APPARATUS. 


Fig.  519. 


The  seminiferous  tubes  in  the  lobules  are  from  -20  mm.  to  -25  mm.  in  diameter. 
Their  walls  are  composed  of  two  membranes — an  internal,  which  is  thin,  amor- 
phous, and  formed  of  cells  joined  border  to  border  as  in  an  endothelium  ;  and 
an  external,  thicker,  lamellar,  and  containing  nuclei.  The  walls  are  lined  by  a 
stratified  epithelium,  which  is  constantly  undergoing  evolution  in  the  adult. 
The  external  layer  is  named  the  basal  epithelium.  It  contains  two  kinds  of  cells  : 
ordinary,  indifferent  cells,  named  the  "  cells  of  Sertoli ; "   and  thin,  round, 

granular  cells  (^spermatogonia)  mixed  with, 
these.  The  latter  are  the  male  ova  of 
Robin,  and  it  is  they  alone  which  exhibit 
the  phenomena  of  spermatogenesis.  Before 
the  manifestation  of  this  process,  the  male 
ova  proliferate,  join  the  cells  of  Sertoli,  and 
form  on  the  face  of  each  of  these  elegant 
radial  series. 

Spermatogenesis  is  the  name  given  to 
the  epithelial  evolution  which  leads  to  the 
formation  of  spermatozoids.  In  spermato- 
genesis, there  are  two  periods  :  1.  The 
period  of  the  proliferation  of  the  tubular 
epithelium  resulting  in  the  production  of 
the  spermatoblasts.  2.  The  period  of  dif- 
ferentiation, in  which  the  spermatoblasts 
are  transformed  into  spermatozoids.  This- 
change  involves  the  nucleus  of  the  sperma- 
toblast, which  becomes  the  head  of  the 
spermatozoid ;  then  the  protoplasm,  from 
which  is  produced  the  tail  of  the  sperma- 
tozoid. 

Between  the  seminiferous  tubules  is  a 
stroma  composed  of  somewhat  peculiar 
connective  tissue,  in  which  are  numerous 
cells  filled  with  yellowish  granules.  Blood- 
vessels and  lymphatics  course  through  this 
stroma. 

Vessels  and  nerves. — The  blood  is  carried 
to  the  testicle  by  the  spermatic  arteryy 
which  is  almost  exclusively  appropriated  ta 
it ;  this  vessel,  after  describing  a  great 
number  of  very  remarkable  flexions,  enters  the  upper  border  of  the  gland,  a 
little  behind  the  epididymis.  It  does  not  immediately  plunge  into  its  sub- 
stance, however,  but  passes  within  the  texture  of  the  tunica  albuginea,  along  the 
borders  of  the  testicle,  and  forms  a  complete  circle  around  it.  From  this  circle 
it  sends  oif  divisions,  which  spread  over  the  sides  of  the  organ,  detaching  fine 
arterial  ramifications  that  penetrate  its  proper  tissue  in  accompanying  the  inter- 
lobular septa.  (There  is  generally  described  a  tunica  vasctdosa.,  which  forms  one 
of  the  coverings  of  the  testicle.  This,  in  reality,  is  not  a  distinct  coat,  but 
merely  the  fine  ramifications  of  the  spermatic  artery  spreading  beneath  the 
tunica  albuginea,  and  held  together  by  delicate  connective  tissue.) 

The  veins  are  very  voluminous  and  frequently  varicose  ;  they  comport  them- 


VERTICAL  SECTION  OF  THE  TESTICLE 
(horse's),  passing  THROUGH  THE  CORPUS 
HIGHMORIANUM. 

1  Spermatic  cord,  with  its  serous  covering; 
2,  sections  of  the  flexuous  vessels  of  the 
cord;  3,  head  of  the  epididymis,  or  globus 
major ;  4,  tail  of  the  epididymis,  or  globus 
minor;  5,  vas  deferens;  6,  corpus  High- 
morianum ;  7,  rete  testis ;  8,  tunica 
albuginea  sending  prolongations  from  its 
inner  face,  and  which  divide  the  testicle 
into  lobules ,  9,  surface  of  the  tunica 
albuginea. 


TEE  GENITAL  ORGANS  OF  THE  MALE. 


965 


selves  like  the  arteries,  and  unite  in  a  single  trunk  that  enters  the  posterior  vena 
cava,  near  the  renal  veins.  (On  the  cord,  in  addition  to  their  sometimes  varicose 
condition,  the  spermatic  veins  have  been  observed  to  form  a  network,  named 
the  pampiniform  plexus.) 

The  lymphatics  are  most  numerous  beneath  the  serous  layer  and  the  tunica 

Fig.  520. 


THE    INTERNAL    GENITO-URINARY    ORGANS,    WITH    THE    STOMACH,   LIVER,   AND   SPLEEN,  IN 
THE   F<ETUS  OF    A   MARE 

R,  Left  kidney  ;  V,  bladder ;  T,  testicle ;  at,  spermatic  artery ;  G,  gubernaculum  testis ;  e, 
epidiiiymis  (the  letter  is  placed  in  the  centre  of  the  serous  layer  which  suspends  the  testicle  and 
spermatic  vessels  from  the  subiumbar  resion,  and  after  the  descent  of  the  gland,  forms  the 
frtenum  between  the  two  layer.s  in  the  vaginal  sheath);  E,  stomach;  F,  liver;  /.  lobus  Spigelii ; 
P,  vena  portse ;  C,  umbilical  cord ;  0,  umbilical  vein ;  0',  intra-hepatic  course  of  that  vein, 
indicated  by  a  double  dotted  line. 

albuginea.  They  commence  by  lacunae  in  the  interstitial  connective  tissue,  and 
form  a  very  rich  network,  in  the  meshes  of  which  are  seminiferous  tubules.  They 
pass  into  the  network  of  the  tunica  albuginea,  and  thence  they  follow  the  sper- 
matic cord  to  terminate  in  the  sublumbar  glands. 

The  nerves  of  the  testicle  are  derived  from  the  sf     athetic  (and  pass  from 


966  GENERATIVE  APPARATUS. 

the  abdomen  with  the  blood-vessels)  ;  they  form  a  small  particular  plexus  around 
the  artery.  (The  nerves  pierce  the  membrana  propria  of  the  tubuli  semiuiferi, 
and  end  in  a  more  or  less  pyramidal  mass  of  protoplasm,  in  which  lie  clear 
elliptical  nuclei.  The  ends  of  the  fibres,  therefore,  lie  in  close  proximity  to  the 
outer  layer  of  the  secreting  cells.) 

Development. — In  the  foetus,  at  an  early  age,  the  testicle  floats  in  the 
abdominal  cavity,  being  suspended  from  the  sublumbar  region,  near  the  flank, 
by  a  wide  peritoneal  fold,  at  the  anterior  border  of  which  are  the  spermatic 
vessels  (Fig.  520,  e) ;  the  tunica  vaginalis  is  not  yet  present.  The  mechanism 
of  the  formation  of  this  is  very  simple,  and  easy  to  understand.  The  visceral 
layer  of  the  tunica  vaginalis,  Avhich  envelops  the  testicle  and  the  cord,  being 
already  formed,  as  well  as  the  serous  frienum  that  establishes  continuity  between 
this  and  the  parietal  layer  in  the  adult  animal,  it  only  remains  to  explain  how  nature 
proceeds  to  construct  the  vaginal  sac  in  which  the  gland  is  afterwards  contained. 

We  have  remarked  that  to  the  posterior  extremity  of  the  testicle  is  attached 
a  thick  round  funicle,  the  other  end  of  which  passes  into  the  internal  inguinal 
ring  ;  this  is  enveloped  by  the  peritoneum,  and  fixed  to  the  posterior  border  of 
the  serous  layer  that  suspends  the  testicle.  This  funicle  is  the  guhernaadum 
testis,  and  is  continuous  by  its  inguinal  extremity  with  the  dartos,  the  structure 
of  which  it  apparently  shares,  and  which  alone  acts  as  the  scrotal  sac  to  it. 
The  serous  layer  covering  it  has  on  its  outer  adherent  face  the  cremasteric  muscle, 
which  is  attached  to  the  ilio-lumbar  aponeurosis  in  the  vicinity  of  the  inguinal 
ring,  enters  the  serous  tube  formed  by  the  peritoneal  envelope  of  the  guberna- 
culum,  and  advances  by  its  terminal  extremity  to  near  the  testicle.  To  this 
organ  is  due  the  principal  share  in  the  formation  of  the  vaginal  pouch. 

When  the  progress  of  development  in  the  foetus  pushes  the  testicle  towards 
the  inguinal  region,  the  gubernaculum  acts  as  a  guide,  as  its  picturesque  name 
sufficiently  indicates.  It  is  the  first  to  descend  into  the  inguinal  opening,  draw- 
ing the  testicle  after  it.  But  in  performing  this  movement  it  also  carries  along 
its  peritoneal  covering,  which  gradually  leaves  it  to  become  related,  by  its 
adherent  face,  to  the  walls  of  the  inguinal  canal ;  and  thus  this  membrane 
becomes  reflected,  just  as  would  a  sock  everted  or  turned  down  from  the  leg  ta 
the  foot,  the  latter  being  supposed  to  represent  the  testicle. 

The  parietal  layer  of  the  vaginal  sac  is,  then,  nothing  more  than  the  serous 
tube  that,  in  the  foetus,  enveloped  the  gubernaculum  testis  while  it  was  in  the 
abdomen,  and  which  is  reversed  on  the  testicle  and  cord  after  their  descent  into 
the  scrotum,  the  cremasteric  muscle  on  its  adherent  face  having  become  external. 

In  all  species,  the  descent  of  the  testicle  commences  before  birth  :  in  the 
Bovidfe  it  is  even  completed  in  the  early  months  of  intra-uterine  existence.  In 
Solipeds,  however,  the  testicle  most  frequently  remains  in  the  inguinal  canal 
until  the  animal  is  from  six  to  ten  months  old. 

Function. — The  testicles  secrete  the  spermatic  (or  seminal)  fluid.  Pure  semen, 
such  as  is  derived  from  these  glands,  is  a  white,  viscid,  odourless,  and  slightly 
alkaline  fluid.  It  contains  a  small  quantity  of  liquid  matter  (Uqiior  seminis), 
in  which  is  an  innumerable  mass  of  spermatozoids.  After  the  semen  has  passed 
through  the  genital  canals,  it  is  made  much  more  watery  by  the  addition  of 
the  fluids  secreted  by  the  walls  of  these  excretory  ducts,  or  by  the  glands  annexed 
to  them. 

The  spermcdozon,  zoosperma,  spermatozo'ides,  or  spernwtic  filaments,  are  little 
elongated  bodies  from  gio  to  sU  of  a  line  in  length.     They  have  a  pyriform, 


THE  GENITAL   ORGANS  OF  THE  MALE. 


flattened,  or  lancet-shaped  head,  and  a  filiform  tail  terminating  in  a  point  ;  this 
tail  is  often  furnished  at  its  origin  with  an  enlargement,  or  unilateral  or  bilateral 
alae.  Their  form  is  slightly  modified  during  their  course  through  the  excretory 
ducts.  (In  the  different  species,  though  possessing  certain  fixed  characters,  the 
spermatozoa  yet  offer  some  curious  diversities.  Some  of  these  are  well  exhibited 
in  the  annexed  representations  of 

these  particles,  found  in  the  semen  Fig.  521. 

of  very  dissimilar  animals.) 

The  spermatozoa  move  by  undu- 
lations of  the  tail  (Grohe  attributes 
the  motion  to  the  contractile  pro- 
toplasm contained  in  the  head)  ; 
ihey  can  traverse  '004  m.  in  a 
minute.  Their  movements  persist 
for  several  days  in  the  genital 
organs  of  the  female  ;  they  are 
suddenly  arrested  by  water,  acids, 
and  the  electric  spark  ;  on  the 
contrary,  they  are  animated  by 
alkaline  fluids.  (The  movements 
cease  when  the  spermatozoa  are  ex- 
posed to  a  temperature  of  120° 
Fahrenheit.)  These  bodies  are  de- 
veloped in  the  cells  of  the  tubuli 
seminiferi  by  a  modification  of 
their  contents.     Their  development  has  been  already  described  above. 


1,  Spermatozoon  of  the  fro^ ;  2,  of  the  triton  ;  3,  of 
the  finch ;  4,  of  the  field-mouse ;  5,  of  the  hedge- 
hog ;  6,  sheep,  a,  Head  with  nucleus  ;  b,  body  ;  e, 
tail. 


Excretory  Apparatus  of  the  Semen. 

1.  The  Epididymis  and  Deferent  Canal  (Figs.  368,  517,  518,  519). 

Epididymis. — The  organ  thus  named  commences  the  excretory  canal  of  the 
testicle.  It  is  a  body  elongated  from  before  to  behind,  placed  against  the  upper 
border,  and  a  little  to  the  outside,  of  the  testicle.  It  has  a  middle  portion  and 
two  extremities. 

The  middle  is  contracted,  flat  on  both  sides,  and  free  outwardly  ;  it  is  related, 
inwardly,  to  the  spermatic  vessels  and  the  testicle,  to  which  it  is  attached  by  a 
very  short  serous  layer.  The  extremities  are  expanded,  and  adhere  closely  to  the 
testicle.  The  anterior — the  largest — is  named  the  head  of  the  epididymis,  or  globus 
major.  The  posterior,  the  tail  of  the  epididymis,  or  globus  minor,  is  more  detached 
from  the  testicle,  and  is  curved  upwards  to  be  continued  by  the  deferent  canal 
{vas  deferens). 

Structure. — The  epididymis  results  from  the  union  of  from  twelve  to  twenty 
small  tubes — the  efferent  ducts — which,  arising  from  the  rete  testis,  open  together, 
at  a  variable  distance,  into  the  globus  major.  Towards  the  globus  minor  there 
is  only  one  duct,  which  is  more  voluminous  and  less  flexuous,  and  ends  by  becom- 
ing detached  from  the  posterior  lobe  of  the  epididymis  to  constitute  the  vas 
deferens. 

The  organization  of  the  walls  of  these  ducts  is  not  the  same  throughout. 
Thus,  in  the  efferent  ducts  it  comprises  a  simple  ciliated  epithelium,  resting  on  a 
proper  amorphous  membrane,  which  again  is  placed  on  unstriped  circular  fibre, 


968  GENERATIVE  APPARATUS. 

lying  on  a  thin  fibrous  tunic  ;  while  beyond,  there  is  observed  a  stratified  ciliated 
epithelium,  a  proper  membrane,  two  layers  of  unstriped  fibres — circular  and 
longitudinal — and  also  a  fibrous  tunic.  The  thickness  of  the  muscular  layers 
increases  from  before  to  behind. 

The  epididymis  is  enveloped  by  a  fibrous  membrane  and  the  tunica  vaginalis 
propria.  It  receives  its  arteries  and  nerves  from  the  same  sources  as  the 
testicle. 

Vas  Deferens. — This  duct  is  about  the  thickness  of  a  goose-quill,  and  is  at 
first  flexuous,  then  straight.  It  lies  parallel  with,  but  behind  and  to  the  inner 
side  of,  the  spermatic  vessels,  as  far  as  the  opening  of  the  internal  ring  ;  passing 
through  this  opening,  it  enters  the  pelvic  cavity,  and  crosses  obliquely  the  ureter 
and  obliterated  cord  of  the  umbilical  artery.  It  is  then  inflected  backwards  above 
the  bladder,  suddenly  dilates  {bulbous  portion),  and  is  prolonged  as  far  as  the 
neck  of  that  reservoir,  where  it  terminates,  after  having  penetrated  beneath  the 
prostate  gland  by  a  sudden  constriction,  at  the  origin  of  which,  and  outwardly, 
the  vesicula  seminalis  opens,  and  is  continued  by  the  ejaculatory  ducts. 

It  may,  therefore,  be  divided  into  four  portions— a  testicular,  funicular, 
inginual,  and  pelvic. 

The  vas  deferens  is  sustained  in  the  vaginal  canal  by  a  very  short  serous  fold 
— a  dependency  of  the  fraenum — the  two  layers  of  which  envelop  the  spermatic 
vessels,  within  and  behind  which  this  duct  is  situated.  In  the  abdominal  cavity, 
it  is  fixed  by  the  prolongation  of  this  serous  duplicature.  Its  dilated  or  pelvic 
portion  is  in  contact,  superiorly,  with  the  vesiculte  seminales,  and  is  finally  united 
to  its  dilated  homologue  of  the  opposite  side — which  it  has  been  gradually 
approaching — by  means  of  a  triangular  peritoneal  fold,  that  comprises  between 
its  two  layers  a  small  club-shaped  cavity — the  prostatic  utricle,  which  will  be 
alluded  to  again. 

The  calibre  of  the  vas  deferens  is  very  small  in  its  vaginal  and  abdominal 
portions,  but  is  greater  towards  the  pelvic  dilatation,  where  the  wall  of  the  duct 
offer  a  well-marked  areolated  disposition  (ampullce). 

Structure. — The  vas  deferens  is  formed,  internally,  by  a  very  fine  mucous 
membrane  covered  with  cylindrical  epithelium,  and  to  this  is  added,  externally,  a 
contractile  and  a,  fibrous  tunic.  The  contractile  layer  is  formed  of  three  planes  of 
smooth  muscular  fibres  ;  the  deep  and  superficial  planes  have  longitudinal,  and 
the  middle  circular  fibres.  It  is,  proportionately,  very  thick  at  the  dilated  por- 
tion of  the  duct,  and  it  is  to  its  great  density  that  the  vas  deferens  owes  its  con- 
sistence as  a  hard,  rigid  cord.  The  mucous  membrane  of  the  pelvic  dilatation 
offers  a  large  surface,  being  inflected  into  all  the  depressions,  but  it  has  no 
follicles  ;  the  cells  of  its  epithelium  have  special  granules  which  give  a  dark 
colour  to  the  membrane. 

2.  The  Vesicula  Seminales  and  Ejaculatory  Ducts  (Fig.  522). 

The  vesiculce  seminales  are  two  oval  pouches,  the  volume  of  which  varies  with 
their  contents  ;  they  are  placed  in  the  pelvic  cavity,  above  the  bladder  and  the 
vas  deferens. 

Each  vesicula  has  a  middle  portion  and  tivo  extremities.  The  middle  portion 
is  enveloped  by  a  loose  abundant  connective  tissue,  and  is  in  relation  with  the 
rectum  above,  and  below  with  the  bladder  and  vas  deferens. 

The  anterior  extremity  is  the  largest,  and  forms  a  rounded  cul-de-sac,  covered 


THE  GENITAL   ORGANS  OF   THE  MALE. 


Fig.  522. 


in  almost  the  same  manner  as  the  bladder  by  the  peritonemn,  which  at  this 
point  furnishes  a  very  small  triangular  frifinum  (the  recto-vesical  fold)  that 
unites  the  two  vesiculae.  The  posterior  extremity  tapers  to  a  narrow  neck  or 
gullet,  which  passes  beneath  the  prostate  gland,  and  joins  at  a  very  acute 
angle  the  terminal  extremity  of  the  vas  deferens,  to  constitute  the  ejaculatory 
duct. 

The  walls  of  this  pouch  are  composed  of  three  membranes  :  an  internal 
mucous,  a  middle  muscular,  and  an  external 
fibrous.  The  mucous  layer  is  contmuous  with 
that  of  the  ejaculatory  ducts,  and  is  very  thin, 
dehcate,  and  follicular.  It  shows  numerous 
folds,  which  disappear  with  distension  of  the 
duct.  The  middle  layer  evidently  belongs  to  the 
class  of  muscular  membranes.  At  the  bottom  of 
its  cul-de-sac  it  gives  off  several  fasciculi,  which 
radiate  on  the  external  surface  of  the  peritoneum. 
(In  addition  to  these,  the  vesiculae  and  vasa 
deferentia  have  a  muscular  covering  with  fibres 
arranged  in  longitudinal  and  transverse  direc- 
tion, the  latter  being  the  most  superficial.  This 
muscular  layer,  being  continuous  over  the  vesi- 
culae seminales  and  vas  deferens,  when  it  contracts 
will  compress  and  shorten  these  ;  consequently, 
it  has  been  named  the  compressor  vesiculcB  et  ductus 
semincdis.  The  fibroiis  coat  of  the  vesiculse  is 
merely  condensed  connective  tissue.)  The  mucus 
and  muscular  coats  are  supplied  with  blood  by 
the  vesico-prostatic  artery  {inferior  vesical)  ;  their 
nerves  are  derived  from  the  pelvic  plexus. 

The  richness  in  glands  of  the  mucous  mem- 
brane of  the  vesiculas  seminales,  has  led  several 
anatomists  to  consider  them  as  organs  of  secre- 
tion, and  not  as  reservoirs  for  the  semen.  But 
the  large  cavity  that  each  forms,  appears  to 
demonstrate  that  they  serve  as  reservoirs  and 
secretory  organs  at  the  same  time.  Their  fluid 
is  added  to  the  semen,  as  is  the  secretion  of  the 
prostate  and  Cowper's  glands. 

The  ejaculatory  duct  is  very  short,  and  succeeds 
the  narrow  canal  of  the  vesicula  after  the  latter 
opens  into  the  vas  deferens.  The  two  ducts  pass 
between  the  prostate  gland  and  urethra,  and, 
after  'a  brief  course,  terminate  in  the  latter,  on 
the  side  of  the  verumontanum — a  tubercle  which 
will  be  noticed  presently. 

Near  to,  and  in  front  of  this  tubercle,  is  a  third  very  small  orifice — the  open- 
ing of  the  third  pouch  included  between  the  serous  duplicatures  joining  the  vasa 
deferentia.  (This  is  the  siims  pocidarls  or  utriculus  prostatio,  the  protometra,  or 
vesicula  seminalis  tertia  or  media  of  Gurlt.)  Improperly  designated  the  third 
vesicular,  or  masculine  uterus  (Weber),  this  pouch  (sometimes  double)  secretes  a 


SUPERIOR  VIEW  OF  THE  PELVIC  POR- 
TION OF  THE  VASA  DEFERENTIA, 
VESICULA  SEMINALES,  PROSTATE 
GLAND,  cowper's  GLANDS,  AND  THE 
INTRA-PELVIO  PORTION  OF  THE 
URETHRA. 

1,  Left  vas  deferens;  1',  its  pelvic 
dilatation;  2,  2,  the  same  on  the 
right  side ;  3,  4,  vesiculae  seminales; 
5,  the  third  vesicula;  6,  serous 
layer  uniting  the  vasa  deferentia ; 
7,  that  comprised  between  the  two 
vesiculae ;  8,  prostate  gland ;  9, 
bladder  seen  through  the  serous 
fold  of  the  vasa  deferentia;  10, 
membranous  or  intra-pelvic  portion 
of  the  uremral  canal,  covered  by 
Wilson's  muscle;  11,  11,  Cowper's 
glands  enveloped  by  that  muscle; 

12,  12,  ischio-cavernosus  muscle; 

13,  accelerator  urinae  muscle. 


970  GENERATIVE  APPARATUS. 

fluid  which  is  thrown  into  the  urethra.^  (This  third  vesicula  is  present  in  all  the 
domesticated  animals.) 

The  ejaculatory  ducts  may  become  obliterated  ;  then  the  secretion  of  the 
vesiculae  seminales  accumulates  in  their  interior,  and  gradually  distends  them 
until  they  attain  enormous  dimensions.  We  found,  in  a  Gelding,  a  vesicula 
which  was  nearly  as  large  as  the  bladder  ;  it  contained  a  brownish,  adhesive  fluid, 
holding  in  suspension  epithelial  cells  and  free  nuclei. 

(The  vesiculae  seminales,  in  addition  to  tiieir  own  secretion,  receive  the  semen 
conveyed  by  the  spermatic  ducts,  and  keep  it  in  reserve  until  copulation  ;  when 
the  contraction  of  its  muscular  apparatus  expels  it  into  the  ejaculatory  ducts, 
and  from  these  into  the  urethral  canal.) 

3.  The  Urethra. 

The  urethra  is  a  canal  with  membranous  and  erectile  walls,  commencing  at 
the  neck  of  the  bladder,  and  terminating  at  the  free  extremity  of  the  penis. 

Course. — When  followed  from  its  origin  to  its  termination,  it  is  seen  to 
proceed  at  first  horizontally  backwards,  then  bend  downwards  at  the  ischial  arch 
to  leave  the  cavity  of  the  pelvis,  placing  itself  between  the  two  roots  of  the 
corpus  cavernosum,  and  passing  forward  in  the  channel  formed  at  the  lower 
border  of  these,  until  it  arrives  at  the  head  (glans)  of  the  penis,  where  it  termi- 
nates by  forming  a  small  (cylindrical)  prolongation,  named  the  urethral  tube. 
In  its  track,  the  urethra  is  divided  into  two  very  distinct  portions  :  the  intra-pelvic 
— the  shortest,  and  the  extra-pelvic — the  most  extensive,  and  which  is  supported 
by  the  corpora  cavernosa.  The  latter  division,  being  alone  enveloped  by  the 
erectile  tissue  that  enters  into  the  formation  of  the  urethral  walls,  has  been  also 
named  the  spongy  portion,  the  first  being  designated  the  membranous  (and  pro- 
static) portion. 

Interior. — Internally,  this  canal  has  not  the  same  width  throughout.  Very 
constricted  at  its  origin,  towards  the  neck  of  the  bladder,  it  expands  somewhat 
suddenly  at  the  prostate  gland  ;  its  dilatation,  improperly  named  in  Man  the 
cul-de-sac  of  the  bulb  (bulbous  portion),  or,  better,  the  ventriculus,  extends  to  its 
curve  over  the  ischial  arch,  where  it  gradually  contracts.  After  this  it  preserves 
the  same  reduced  dimensions  throughout  its  course,  though  these  dimensions  may 
be  increased  during  the  passage  of  the  urine  or  semen.  There  is,  however, 
behind  the  urethral  tube  a  small  oval  dilatation,  named  the  fossa  navirularis 
(Fig.  524).  Smooth  throughout  its  extra-pelvic  portion,  the  inner  surface  of  the 
urethra  offers,  near  the  neck  of  the  bladder,  and  on  its  upper  wall,  the  excretory 
orifices  of  the  prostate  gland,  which  form  two  lateral  lines  of  minute  perforated 
tubercles.  Between  these  two  lines  is  found  the  urethral  ridge  or  verumontanum 
{caput  galUnaginus),  a  httle  eminence  elongated  from  before  to  behind,  on  the 
sides  of  which  the  ejaculatory  ducts  open.  Behind  this  are  the  excretory  orifices 
of  Cowper's  glands. 

Relations. — The  intra-pelvic  portion  of  the  urethra  is  in  relation,  above,  with 
the  prostate,  which  adheres  closely  to  it,  and  with  the  rectum,  to  which  it  is 

'  In  some  Asses,  we  have  found  this  pouch  bifurcated  at  its  anterior  extremity,  and  there- 
fore bearing  a  distant  resemblance  to  the  female  uterus. 

(Though  Chauveau  states  that  the  protometra  is  improperly  named  the  male  uterus,  it  would 
appear,  nevertheless,  that  the  designation  is  correct ;  as  this  pouch  is  not  a  gland  in  the 
ordinary  sense  of  the  term,  and  is  certainly  the  rudiment  of  the  duct  which  develops  into  the 
uterus  in  the  female.) 


TEE  GENITAL   ORGANS  OF  THE  MALE.  971 

united  by  the  abundant  loose  connective  tissue  in  this  part  of  the  pelvis  ;  below, 
it  lies  on  the  internal  obturator  muscle  ;  laterally,  it  is  related  to  the  muscles 
and  ligamentous  or  aponeurotic  expansions  that  close  in  the  sides  of  the  pelvis. 
Outside  the  pelvic  cavity,  the  urethra  is  united  in  the  most  intimate  manner 
to  the  corpora  cavernosa,  which  embrace  its  anterior  border.  By  its  posterior 
border,  it  is  related  to  the  suspensory  ligament  of  the  penis. 

Structuee. — The  urethra  is  composed  of  :  1.  Mucous  membrane.  2.  An 
srectile  envelope.  3.  Muscles.  4.  Vessels  and  nerves.  5.  The  perineal  aponeuroses, 
which  are  in  immediate  relations  with  this  canal. 

1.  Mucous  Membrane. — This  is  rather  delicate,  and  forms  the  lining  of 
the  canal.  It  is  continuous,  posteriorly,  with  that  of  the  bladder,  and  in  front 
with  the  integument  enveloping  the  head  (glans)  of  the  penis ;  it  is  also 
prolonged  into  the  excretory  ducts  of  the  glands  annexed  to  the  urethra,  and  the 
€Jaculatory  ducts.  It  has  longitudinal  folds,  and  is  always  in  contact  with 
itself,  except  during  the  passage  of  urine  or  semen  ;  it  has  scarcely  any  papillae, 
only  a  few  being  found  near  the  anterior  extremity  of  the  canal ;  and  its  tissue 
is  very  rich  in  elastic  fibres. 

The  epithelium  of  this  membrane  is  stratified  and  cylindrical,  but  at  the 
portion  furnished  with  papilla  it  becomes  pavemental. 

2.  Erectile  Envelope. — This  envelope,  lying  outside  the  mucous  membrane, 
does  not  cover  the  intra-pelvic  portion  of  the  canal.  It  commences  a  little  above 
the  ischial  contour,  behind  Cowper's  glands,  by  a  very  thick  bulging  portion, 
named  the  bulb  of  the  urethra.  In  front,  it  terminates  by  another  bulbous 
enlargement,  into  which  the  anterior  extremities  of  the  corpora  cavernosa  enter, 
named  the  head  of  the  penis  (glans  penis). 

The  tissue  composing  this  envelope  has  the  same  organization  as  other 
erectile  apparatuses,  being  a  network  of  communicating  cavities  separated  by 
elastic  septa,  the  latter  showing  in  their  structure  some  contractile  elements  (see 
Corpora  Cavernosa). 

3.  Muscles. — Behind  the  prostate  gland,  the  mucous  membrane  of  the 
urethra  is  covered  by  a  fleshy  layer  of  circular  fibres,  forming  a  sphincter. 
Another  muscular  envelope,  constituting  the  bidbo-cavernous  or  accelerator  urinoe 
muscle,  also  covers  the  erectile  tissue  of  the  urethra,  accompanying  it  to  near 
the  glans,  where  it  gradually  disappears.  To  these  two  principal  muscles  of  the 
urethra  are  added  two  pairs  of  secondary  fasciculi — the  compressor  of  Cowper's 
glands  and  the  transversus  perincei.  The  following  is  a  resume  description  of 
the  muscular  apparatus  : — 

a.  Urethral  sphincter.^ — This  may  be  described  as  a  single  muscle  composed 
of  two  portions — an  inferior  and  a  superior.  Both  are  formed  by  transverse 
fibres  thrown  over  the  membranous  portion  of  the  urethra,  and  both— the 
superior  and  inferior — are  united  at  their  extremities,  which  are  not  attached  to 
the  walls  of  the  pelvis.  Behind,  the  superior  fibres  are  mixed  with  those  of  the 
compressor  of  Coivper's  glands. 

b.  Accelerator  urince. — Composed  of  transverse  fibres  encircHng  the  urethra 

'  Up  to  the  present,  this  organ  has  been  described  in  books  on  Veterinary  Anatomy  as 
Wilson's  muscle.  In  a  work  entitled  Recherches  sur  VAnatomie  compare'e  du  Perine'e,  published 
in  Professor  Robin's  journal,  Paulet  riglitly  objects  to  this  designation,  which  perpetuates  an 
error  of  interpretation.  We  adopt  this  opinion,  not  only  with  regard  to  this  muscle,  but  also 
the  ischio-urethral,  which,  with  him,  we  more  exactly  designate  aa  the  compressor  of  Cowp&i'$ 
glands. 


972  GENERATIVE  APPARATUS. 

from  the  ischial  arch  to  the  free  extremity  of  the  penis,  this  will  also  be  studied 
as  a  single  organ,  separated  into  two  lateral  portions  by  a  median  raphe  passing 
along  the  whole  posterior  face  of  the  urethra.  The  fibres  pass  from  this  raphe 
to  the  right  and  left,  enter  the  furrow  of  the  corpora  cavernosa,  and  reach  the 
upper  surface  of  the  urethra,  where  they  advance  towards  each  other,  but  do  not 
join  in  the  middle  line  ;  so  that  the  circle  formed  by  this  muscle  is  necessarily 
incomplete. 

c.  Compressor  muscle  of  Comperes  glands. — This  muscle  is  composed  of  two 
layers  of  fibres — a  superior  and  an  inferior — confounded  on  the  periphery  of 
Cowper's  glands.  The  superior  layer  is  continuous,  it  may  be  said,  with  the 
upper  part  of  the  urethral  sphincter.  The  inferior  layer  is  attached,  posteriorly, 
by  some  aponeurotic  fibres  to  the  ischial  arch. 

d.  Transversus  perincei. — This  is  a  very  thin  ribbon-like  fasciculus,  often 
scarcely  distinguishable  from  the  ischio-anal  muscle  {retractor  am).  It  extends 
transversely  from  the  ischial  tuberosity — to  which  it  is  attached  through  the 
medium  of  the  sacro-sciatic  ligament — to  the  mesial  line  of  the  perineum,  where 
its  fibres — confounded  with  those  of  its  homologue  on  the  opposite  side — appear 
to  be  inserted  in  the  accelerator  urin^e  muscle  at  its  origin. 

e.  Action  of  the  urethral  muscles. — 1.  The  urethral  sphincter,  when  it  contracts, 
compresses  between  its  two  layers  the  membranous  portion  of  the  urethra.  It  is 
a  veritable  sphincter,  and  opposes  the  escape  of  the  urine ;  when  the  semen  is 
thrown  from  the  vesiculae  seminales  into  the  urethra,  it  also  prevents  that  fluid 
entering  the  bladder,  by  permitting  the  accelerator  to  empty,  from  before  to 
behind,  the  initial  dilatation  of  that  canal.  2.  The  accelerator  urince  is  correctly 
named,  from  the  part  it  plays  in  ejecting  the  semen  from  the  urethra — it  being 
the  chief  agent  in  this  act.  3.  The  compressor  of  Coivper'^s  glands  pulls  back  the 
membranous  portion  of  the  urethra,  along  with  Cowper's  glands,  and  acts  as  a 
compressor  to  these.  4.  The  transversus  perincei  dilates  the  bulbous  portion  of 
the  urethra,  by  drawing  it  out  laterally. 

4.  Vessels  and  Nerves. — The  urethra  is  supplied  with  blood  by  the  bulbo- 
urethral arteries  and  the  two  pairs  of  arteries — the  dorsals  of  the  penis.  Voluminous 
veins — frequently  varicose,  and  satellites  of  the  arteries — carry  it  away.  The 
Igmphatics  form  a  very  rich  plexus  beneath  the  mucous  membrane  ;  their  trunks 
pass  to  the  inguinal,  and  some  to  the  sublumbar,  glands.  The  nerve-Ma.ments, 
are  from  the  internal  pudic  and  great  sympathetic. 

5.  Aponeuroses  of  the  Perineum. — In  the  perinaeal  region,  the  urethra 
is  covered  by  two  superposed  fibrous  layers. 

The  superficicd  aponeurosis  is  fibro-elastic,  and  appears  to  arise  from  the  inner 
surface  of  the  thighs,  where  it  is  mixed  with  the  dartos  ;  it  covers  the  piirinteum, 
and  its  fibres,  becoming  disassociated,  disappear  on  the  sides  of  the  sphincter  ani. 
This  membrane  is  in  relation,  externally,  with  the  skin,  and,  internally,  with  the 
deep  aponeurosis.  On  the  middle  of  its  external  face,  it  receives  the  insertion  of 
a  muscular  fasciculus,  which  is  detached  from  the  sphincter. 

The  deep  or  perinatal  aponeurosis,  formed  of  white  inelastic  fibrous  tissue, 
adheres  to  the  preceding  by  its  outer  face,  and  to  the  accelerator  urinte  and 
ischio-cavernous  muscles  by  its  inner  face.  Above,  it  is  lost  around  the  termina- 
tion of  the  rectum  ;  below,  it  expands  between  the  thighs.  To  the  right  and 
left,  it  insinuates  itself  between  the  erector  penis  and  semimembranosus  muscles, 
to  be  attached  to  the  ischiatic  tuberosity  ;  it  is  prolonged  in  the  pelvic  cavity 
between  the  bladder  and  rectum,  where  it  hmits  two  independent  spaces  :  1.  A 


THE  GENITAL   ORGANS  OF  THE  MALE.  978 

superior — defecatory — space.     2.   An   inferior— genito-urinary— space.     Below 
it  is  confounded  with  the  fibrous  envelope  of  the  penis. 

4.  The  Glands  annexed  to  the  Urethra. 

A.  Prostate  (Fig.  522,  8). — This  single  and  symmetrical  gland  is  situated 
at  the  commencement  of  the  urethra,  and  lies  across  the  neck  of  the  bladder.  A 
constriction  in  the  middle  divides  it  into  two  voluminous  lateral  lobes,  inclining 
slightly  forward.  Its  upper  face  corresponds  to  the  rectum,  through  the  medium 
of  the  connective  tissue  at  the  bottom  of  the  pelvic  cavity.  Its  inferior  face, 
moulded  on  the  neck  of  the  bladder,  embraces  it  above  and  laterally,  and  is 
closely  attached  to  it ;  it  covers  the  terminal  extremity  of  the  vas  deferens  and 
ejaculatory  ducts,  and  the  neck  of  the  vesiculae  seminales. 

Structure. — The  tissue  composing  this  gland  forms  a  number  of  com- 
municating cells,  which  are  larger  in  the  Ass  than  the  Horse  ;  in  these  is 
collected  a  quantity  of  viscid  fluid  {succus  prostaticas)  secreted  by  their  walls, 
and  which  is  ejected  into  the  urethra  by  the  two  rows  of  orifices  arranged  on  the 
sides  of  the  verumontanum.  These  communicating  cells  are  nothing  more  than 
conglomerate  glands,  which  are  distributed  in  a  stroma  of  connective  tissue  and 
uustriped  muscular  fibres.  The  epithelium  of  the  glandular  culs-de-sac  is  formed 
of  two  layers  of  cells  ;  those  of  the  excretory  ducts  are  ciliated. 

B.  Cowper's  Glands. — In  Veterinary  anatomy,  these  are  frequently  named 
the  small  prostates.  They  are  two  globular  bodies,  denser  in  texture  than  the 
prostate  gland,  but  otherwise  the  same  in  organization,  except  in  their 
epithelium,  which  is  cylindrical.  They  are  situated  on  each  side  of  the  urethra, 
in  the  perinseal  region,  above  the  ischial  arch,  and  are  completely  enveloped  by 
a  somewhat  thick  fleshy  covering,  formed  by  the  fibres  of  the  compressor  muscle 
(Fig.  522,  11). 

The  fluid  they  secrete  is  thrown  into  the  urethral  canal  by  numerous  orifices 
in  several  rows,  near  the  middle  line  of  the  superior  plane.  It  has  the  same 
physical  properties  as  that  of  the  prostate,  and  both  are  poured  into  the  urethra 
in  abundance  immediately  before  ejaculation  ;  the  expulsion  of  the  semen  is  by 
this  means  facilitated. 

5.  The  Corpus  Cavernosum. 

The  corpus  cavernosum  is  an  erectile  body,  which  forms  the  base  of  the  penis 
and  supports  the  urethra  ;  it  is  situated  between  the  thighs,  prolonged  beneath 
the  abdomen,  attached  behind  to  the  ischial  arch,  and  terminates  in  front  by  a 
free  extremity,  which  is  received  into  the  erectile  enlargement  named  the  glans 
penis. 

External  conformation. — Flattened  on  both  sides,  this  body  offers  for  study 
two  lateral  faces,  two  borders,  and  two  extremities. 

The  faces  are  plane,  and  present  no  features  of  interest.  The  superior,  or 
dorsal  border,  is  the  thickest,  and  is  rounded  on  both  sides.  The  inferior  is 
channeled  throughout  its  extent  by  a  deep  furrow  which  lodges  the  urethra. 
The  posterior  extremity  is  bifurcated,  the  two  branches  constituting  the  roots 
(corpora  or  crura)  of  the  penis  ,•  they  are  fixed  to  the  ischial  arch,  one  to  the 
right,  the  other  to  the  left,  and  are  covered  by  the  two  ischio-cavernosus 
{erector  penis)  muscles — short,  thick,  and  strong  masses  intersected  by  numerous 
64 


974  GENERATIVE  APPARATUS. 

tendinous  fibres,  and  partly  concealed  by  the  semimembranosus  muscles.  These 
erector  penis  muscles  arise  from  the  inferior  ischiaic  spine,  and  terminate  on  the 
membrane  enveloping  the  crura  of  the  penis,  which  they  cover  posteriorly  and 
externally. 

The  anterior  extremity  of  the  corpus  cavernosum  forms  a  blunt  point,  and  is 
surrounded  by  the  spongy  tissue  of  the  glans. 

Mode   of  attachment  of  the  corpus   cavernosum. — The   chief   attachment   is 

constituted  by  the  insertion  of  the  two  crura  into  the  ischiatic  arch.    There  is 

also  a  double  suspensory  ligament  proceeding  from  the  ischio-pubic  symphysis, 

where  it  is  confounded  with  the  superior  attachments  of  the  short  adductor  of 

the  thigh,  and  passes  to  the  dorsal  border  of  the  corpus 

Fi|^3.  cavernosum,  a  little  in  front  of  the  point  of  union  of  its 

crura. 

Structuee. — This  erectile  organ  is  composed,  ex- 
ternally, of  a  white,  elastic,  fibrous  envelope,  remarkable 
for  its  thickness,  especially  on  the  dorsum  ;  it  gives  off, 
from  its  inner  face,  a  certain  number  of  lamellar  trabe- 
culge  which  partition  the  interior  of  the  cavity  it  forms. 
One  of  these  septa  {septum  pectiniforme)  is  directed 
vertically  from  the  upper  to  the  lower  border,  and  di- 
TRANsvERSE~%ECTioN  OF  vldcs  thc  corpus  cavcmosum  into  two  lateral  portions 
THE  PENIS,  SHOWING  THE     {corfora  cavemoso)^  which  would  indicate  that  the  crura 

URETHRr     WITH        THE       ^^®    "^^    ^^^    °^^^^    ^^    ^^^^^    P^^^^^    ^^    ^^0°'    ^^^    ^^^^^^^ 

CORPUS  CAVERNOSUM.         joiuod  to  each  other.      In  the  Horse,  this  septum  is 
1,  Erectile  tissue  of  the    generally  Very  incomplete,  and  rarely  extends  the  whole 

corpus     caveruosum ;     2,      length  of  the  Organ. 

urethral  canal ;  4,  e^rectile  The  lamellar  prolongations  sustain  other  elastic  and 

tissue  of  the  urethra ;  5,  contractile  bands,  which  circumscribe  the  cavities  in 
secttnlf'theTspensory  ^^^^ch  is  lodged  the  essential  portion  of  the  erectile 
ligament  of  the  penis.  tissue.  According  to  Legros,  the  latter  is  composed  of 
a  network  of  capillaries  interposed  between  the  arterial 
and  venous  twigs  ;  this  network  shows  abrupt  or  regular  dilatations  of  a  diameter 
varying  from  •0001  m.  to  '0015  m.  These  successively  dilated  capillaries  have 
very  thin  walls,  which  are  adherent  to  the  contractile  prolongations  of  the 
envelope,  and  are  lined  by  a  very  delicate  pavement  endothelium.  In  the  areolae 
of  the  cavernous  tissue,  particularly  towards  the  base  of  the  organ,  the  arteries 
offer  a  special  arrangement ;  their  walls  are  very  thick,  and  they  soon  divide 
into  a  bouquet  of  branches  which  enter  the  areolae,  where  they  terminate  either 
by  a  cul-de-sac,  or — which  is  most  frequent — give  off  small  free  branches  convo- 
luted in  a  spiral  manner.  These  are  the  arterim  helkince  described  by  Midler  and 
Rouget.  (The  walls  of  the  cells  are  composed  of  white  and  yellow  fibrous  tissue, 
and  unstriped  muscular  fibres.  The  cells  themselves  are  in  reality  venous  sinuses. 
KoUiker  found  a  minute  artery  to  proceed  from  each  of  the  caecal  terminations 
of  the  helicine  arteries,  and  terminate,  like  the  other  capillaries,  in  the  veins. 
The  dilated  vessels  have  been  regarded  by  some  anatomists  as  only  vascular  loops. 
The  cells,  during  the  erection  of  the  penis,  are  distended  with  blood.) 

The  arteries  of  the  corpus  cavernosum  and  dorsales  penis  pass  into  the 
erectile  structure,  and  supply  this  organ  with  blood.  The  collateral  veins  of 
these  arteries  arise  near  the  surface.  The  nerves  are  from  the  internal  pudic 
and  great  sympathetic. 


THE  GENITAL   ORGANS  OF  THE  MALE. 


975 


6.  The  Penis. 

The  penis  is  the  male  organ  of  copulation,  and  results  from  the  union  of  the 
corpus  cavernosum  and  the  spongy  portion  of  the  urethra.  These  parts  have 
already  been  described  ;  so  it  now  remains  to  consider  the  organ  in  its  entirety. 

The  penis  commences  at  the  ischial  arch,  passes  between  the  thighs  and  the 
two  dartoid  sacs  containing  the  testicles,  and  is  prolonged  beneath  the  belly, 
where  it  terminates  in  a  free  extremity. 

All  the  portion  comprised  between  the  ischial  arch  and  the  scrotum  is 
maintained  and  deeply  covered  by  the  sm'rounding  textures,  and  is  named  the 
fixed  portion  of  the  penis.  The  remainder  of  the  organ — its  anterior  moiety — 
is,  on  the  contrary,  its  free  p)ortion,  as  it  forms  a  detached  appendage  sustained 
by  a  cutaneous  fold — the  sheath  (or  prepuce). 

The  Fixed  Portion  occupies  the  perinasal  region  and  that  between  the 
thighs,  where  it  is  enveloped  by 

the    arteries,   veins,   and    nerves  ^'g-  ^24. 

already  known,  as  well  as  by  a 
large  quantity  of  connective  tissue 
(and  the  skin). 

The  Free  Portion  is  lodged 
in  the  prepuce  during  the  inactive 
condition  of  the  organ,  but  pro- 
trudes from  it  when  in  a  state  of 
erection.  It  is  then  seen  to  be 
covered  by  a  smooth,  unctuous, 
tegumentary  membrane  with 
numerous  papillae,  and  of  variable 
colour,  though  most  frequently  it 
is  black  or  variegated.  Its  base 
presents  a  slight  circular  enlarge- 
ment, due  to  the  accumulation, 
beneath  the  mucous  membrane,  of 
a  small  annular  mass  of  elastic 
and  contractile  tissue.  Its  ex- 
tremify  or  glans  is  also  a  circular  enlargement,  lunited  behind  by  a  salient  ridge 
— the  corona  glandis — which  is  notched  inferiorly,  and  at  the  moment  of  ejacu- 
lation assumes  a  considerable  development,  its  shape  being  then  not  unlike 
the  rose  of  a  watering-can.  This  enlargement  has  for  its  basis  the  terminal 
expansion  of  the  urethral  erectile  tissue,  and  presents  on  its  anterior  face  :  1.  In 
the  centre,  a  rounded  prominence  due  to  the  anterior  point  of  the  corpus  cavern- 
osum. 2.  Beneath  this,  the  urethral  tube  encircled  by  a  fossa.  3.  At  the 
bottom  of  the  fossa,  and  below  the  urethra,  the  orifice  of  a  double  cavity  —the 
urethral  sinus,  which  widens  at  the  bottom,  and  in  which  accumulates  sebaceous 
matter  that  sometimes  becomes  so  hard  as  to  prevent  the  flow  of  the  urine,  by 
compressing  the  tube.     4.  Inferiorly,  the  suburethral  notch. 

The  dermis  covering  the  extremity  of  the  penis  is  rich  in  nerves  which, 
according  to  Kraiise,  have  round  dilatations  which  he  designates  as  "  terminal 
genital  corpuscles." 

To  complete  the  description  of  the  penis,  there  only  remain  to  be  described  : 
1.  Two  suspensory  and  retractile  ligaments  which  concur,  with  the  natural  elasti- 


LONGITUDINAL   SECTION   OF    THE   FREE   EXTREMITY   OF 
THE   horse's   penis   IN   A    RELAXED  STATE. 

1,  Erectile  tissue  of  the  corpus  cavernosum  ;  2,  urethra; 
3,  fossa  navicularis  ;  4,  urethral  tube ;  5,  erectile 
tissue  of  the  urethra;  6,  ditto  of  the  glans;  7, 
corona  glandis ;  8,  urethral  sinus. 


976  GENERATIVE  APPARATUS. 

city  of  the  fibrous  envelope  of  the  corpus  cavernosum,  to  return  the  organ  to  ita 
ordinary  position  when  the  phenomenon  of  erection  has  ceased.  2.  The  tegu- 
mentary  fold,  or  sheath,  which  envelops  the  free  portion  of  the  penis  when  in 
its  ordinary  state  of  repose. 

A.  Suspensory  and  Retractile  Ligaments  of  the  Penis. — Two  in 
number,  these  ligaments  arise  from  the  lower  face  of  the  sacrum,  descend  as 
flat  bands  in  front  of  the  sphincter  ani,  between  the  retractor  muscle  of  the  anus 
and  the  rectum,  to  which  they  give  numerous  short  fasciculi  from  their  posterior 
border  ;  they  then  unite  at  the  mesial  line,  below  the  anal  opening,  thus  forming 
around  the  terminal  extremity  of  the  rectum  a  real  suspensory  ring.  Lying 
together,  and  intimately  united,  they  are  continued  on  the  accelerator  urinae, 
which  they  follow  at  the  raphe,  and  are  eventually  lost  in  its  texture,  near  the 
free  extremity  of  the  penis. 

These  cords  are  composed  of  unstriped  muscular  fibres. 

B.  Prepuce. — The  prepuce,  or  sheath,  is  a  cavity  formed  by  a  fold  of  the 
abdominal  skin,  and  lodges  the  free  portion  of  the  penis ;  it  is  entirely  effaced 
at  the  moment  of  erection,  when  the  copulatory  organ  is  lengthened  and  enlarged. 
The  skin  at  the  opening  of  the  prepuce  enters  its  cavity,  and,  on  arriving  at  the 
free  portion  of  the  penis,  forms  a  circular  cul-de-sac  in  becoming  reflected  over 
the  organ,  which  it  envelops. 

This  lining  integument  of  the  prepuce  is  fine,  and  is  very  irregularly  plicated  ; 
it  is  destitute  of  hair,  and  holds  a  middle  place,  with  regard  to  organization, 
between  the  skin  and  mucous  membranes.  It  contains  in,  or  beneath,  its  sub- 
stance a  considerable  number  of  sebaceous  or  prceputial  glands  that  secrete  an 
unctuous  fatty  matter  (exhaling  a  peculiar  odour,  and  dark  grey  in  colour — the 
smegma  praputii),  which  is  spread  over  the  free  surface  of  the  membrane. 

Above,  the  inner  integument  of  the  sheath  is  applied  to  the  tunica  abdomin- 
alis.  Below,  and  on  each  side,  tlie  cutaneous  fold  constituting  this  cavity  con- 
tains between  its  layers  an  expansion  of  yellow  elastic  fibrous  tissue,  the  lateral 
portions  of  which,  attached  to  the  abdominal  tunic,  are  named  the  suspensory 
ligaments  of  the  prepuce. 

In  the  Ass,  there  exists,  near  the  entrance  to  the  prepuce,  and  on  each  side, 
a  small  tubercle  which  may  be  looked  upon  as  a  rudimentary  teat  of  the  female. 

(The  prepuce  protects  the  penis,  and  sustains  it  when  in  a  flaccid  state.  In 
certain  Horses,  a  gurgling  sound  is  produced  in  trotting,  from  the  air  brusquely 
entering  and  leaving  this  sheath.) 

Differential  Characters  in  the  Male  Genital  Organs  of  the  other  Animals. 

Ruminants.— Farina?  sheath.— Go\\h&\x\  has  remarked  that,  in  the  Bull,  the  internal 
inguinal  ring  is  very  small  when  compared  with  that  usually  seen  in  the  Horse.  It  is  situated 
nearly  at  the  point  of  union  between  the  two  originating  branches  of  the  sartorius  muscle. 

Testicles— In  these  animals  tiie  testicles  are  very  voluminous,  oval,  and  vertically  elongated. 
Thev,  with  their  envelopes,  form  a  pendant  mass  that  occupies  the  inguinal  region.  The 
scrotum  is  always  of  a  pale  colour.  In  the  interior  of  the  testicle,  the  corpus  Higlimorianum 
and  the  rete  testis  nre  very  marked.  (The  proper  tissue  is  yellow,  and  the  septa  formed  by 
the  prolongations  of  the  tunica  albuginea  are  not  very  distinctly  seen.) 

Epididymis.— Vas  deferens.— T!\\e  head  of  the  epididymis  is  wide  and  flat,  and  partly  covers 
the  ant.rior  border  of  the  testicle.  The  miildle  portion,  smaller  than  in  Solipeds,  represents  a 
narrow  cord  lying  outside  the  posterior  border  of  the  seminal  gland.  The  tail  is  a  little  free 
appendage,  inflected  inwards  and  upwards  to  become  continuous  with  the  vas  deferens.  The 
latter  is  dilated,  as  in  the  Horse,  when  it  arrives  above  the  bladder,  and  lies  beside  the  duet 
of  the  opposite  side.     The  two,  thus  joined,  increase  from  before  to  behind,  leave  the  neck  of 


THE  GENITAL   ORGANS  OF  THE  MALE. 


OT7 


the  bladder  in  passing  above  the  vesiculse  seminales,  then  go  beneath  the  prostate,  and 
terminate  in  tlie  uretlira— on  the  summit  of  a  ridge— by  two  elliptical  orifices. 

Vesiculee  seminaUs.—In  the  BuU,  the  vesiculae  seminales  have  not  the  same  appearance  aa 

Fig.  525. 


INTERNAL  GENITAL  ORGANS   OF   A    YOUNG   BULL   (UPPER   FACE). 

Bladder ;  U,  ureter ;  C,  penis  enveloped  by  the  corpus  cavernosum.  1,  Testicle  in  its  fibrous 
envelope;  2,  cremaster;  3,  testicle  exposed;  4,  head  of  the  epididymis;  5,  tail  of  the  epididymis, 
6,  vas  deferens;  7,  dilatation  of  the  vasa  deferens;  8,  vesiculae  seminalis;  9.  prostate;  10,  intra- 
pelvic  portion  of  the  urethra  surrounded  by  its  sphincter;  11,  ischio-urethral  muscle;  12,  accele- 
rator urinse  ;  13,  transversus  perinaei. 


in  the  Horse,  and  they  have  not  so  large  a  cavity  in  their  interior.  They  are  two  elongated 
masses,  lobulated  on  their  surface,  yellow  in  colour,  and  possessing  quite  a  glandular  aspect. 
They  have  sometimes  been  designated  the  lateral  prostates.     They  are  composed  of  aciniform 


978 


GENERATIVE  AFPABATUS. 


glands,  enclosed  in  a  mass  of  connective  tissue  and  unstriped  fibres ;  they  open  into  a  commoa 
central  canal,  which  terminates  in  tlie  vas  deferens. 

Urethra. — This  canal  is  inflected  like  the  letter  S.  Its  diameter  regularly  diminishes  from 
its  commencement  to  its  termination,  wliich  is  not  provided  with  a  urethral  tube,  as  iu 
Solipeds.  Internally  it  presents  :  1.  Immediately  beyond  the  neck  of  the  bladder,  a  short,  but 
very  salient  verumontanum,  which  divides  into  two  mucous  columns  that  gradually  subside 

posteriorly.  2.  Towards  the  ischial  arch,  a 
valve  the  free  border  of  which — directed  down- 
wards— covers  a  cul-de-sac  from  about  three- 
fourths  to  one  inch  deep. 

The  structure  of  the  urethra  is  also  dif- 
erent.  The  walls  of  the  membranous  portion 
are  tliicker  than  in  the  Horse  ;  they  have  a 
layer  of  erectile  tissue,  and  a  sphincter  muscle, 
very  thick  below  and  laterally,  the  fibres  of 
which  are  inserted  in  the  middle  of  the  upper 
surface,  into  an  aponeurotic  rapiie'. 

At  the  ischial  arch,  when  the  canal  bends 
downwards,  the  spongy  tissue  becomes  more 
abundant  to  form  the  hulh  of  the  urethra ;  but 
the  prominence  at  this  point  is  chiefly  due  to 
the  accelerator  urinas,  as  is  shown  in  Fig. 
526,  C  4,  This  muscle  is  extremely  powerful, 
but  it  soon  ceases  beneath  the  ischial  arch. 
The  trausversus  perinasi  is  as  strong  as  in 
Solipeds. 

Glands  annexed  to  the  urethra. — Cowper's 
glands  are  absent.  Tlie  prostate  gland  is  not 
voluminous,  and  forms,  at  the  commencement 
of  the  urethra,  a  little  transverse  yellow,  bilo- 
bate  mass,  beneath  which  pass  the  vasa 
deferentia ;  it  also  lies  beneath  the  sphincter 
muscle,  and  is  prolonged  for  some  distance  on 
the  membranous  portion  of  the  urethra. 

PfMis. — In  the  Bull,  the  penis  is  long  and 
thin,  and  carried  well  forward  beneath  the 
belly.  It  is  enclosed  at  the  perinseum  in  an 
aponeurotic  sheath,  which  is  covered  by  the 
iscbio-tibial  muscles.  This  sheath  is  double, 
its  superficial  layer  being  continuous  with  the 
dartos,  and  it  has  the  same  physical  cha- 
racters; the  deep  layer  is  thin,  white,  and 
inelastic. 

In  front  of  the  pubis,  the  penis  describes 
two  successive  curves — the  S  of  the  penis — the 
first  with  its  convexity  forward;*,  the  second 
backwards.  It  is  at  the  second  curve  that 
the  suspensory  ligmnents  join  tlie  penis,  and 
continue  along  its  sides  to  its  extremity. 

The  free  portion  of  the  organ — very  taper- 
ing— is  covered  by  a  fine,  papillated,  very 
sensitive,  rose-coloured  mucous  membrane. 

It  is  lodged  in  a  narrow  prepuce  that  ad- 
vances much  more  forward  beneath  the  ab- 
domen than  in  Solipeds,  and  has  at  its  opening  a  bunch  of  long  stiff  hairs.  This  cutaneous 
sheath  is  moved  by  four  subcutaneous  muscles:  two  posterior  or  retractors  (Fig.  527,  2)  which 
draw  the  sheath  backwards,  and  concur  in  exposing  the  penis  at  the  moments  of  its  erection  ; 
and  two  anterior  or  protractor  muscles  (Fig.  527,  1)  which  carry  the  prepuce  forward  to  its 
former  position.     The  latter  are  found  in  the  Cow,  and  do  not  appear  to  be  of  any  use. 

The  two  constituent  portions  of  the  copulatory  organ  are  not  joined  in  the  same  manner  as 
in  Solipeds,  the  channel  for  the  lodgment  of  the  urethra  being  transformed  into  a  complete 
canal,  by  a  narrow  layer  of  the  fibrous  envelope  of  the  corpus  cavernosum.    The  latter  is  little 


J  1 

SECTIONS   OF   THE    URETHRA    OF   THE   OX    AT 
DIFFERENT    POINTS. 

Af  Intra-pelvic  portion:  1,  Urethral  sphincter;  2, 
erectile  tissue ;  3,  urethral  canal ;  4,  prostate 
gland.  B,  The  middle  of  the  penis  :  1,  Fibrous 
cord  of  the  corpus  cavernosum ;  2,  urethral 
canal ;  3,  its  erectile  tissue ;  4,  envelope  of 
the  corpus  cavernosum.  C,  At  the  crura  of  the 
penis  :  1,  1,  Crura  of  the  corpus  cavernosum  ; 
2,  urethral  canal ;  3,  its  erectile  tissue  ;  4, 
accelerator  urinae  ;  5,  erector  penis  muscle. 


TEE  GENITAL   ORGANS  OF  THE  MALE. 


979 


developed,  and  presents,  internally,  a  longitudinal  fibrous  cord;  it  is  not  much  dilated  during 
erection.  In  this  act,  the  penis  is  elongated  by  the  straightening  out  of  its  curvatures,  rather 
than  by  any  real  lengthenings;  when  erection  ceases,  the  organ  is  retracted  into  the  preputial 
cavity  by  the  contraction  of  the  suspensory  ligaments,  which  reform  its  double  inflection  behind 
the  scrotum. 

In  the  Ram,  the  disposition  of  the  testicles  and  vasa  deferentia  is  somewhat  similar.  The 
membranous  portion  of  the  urethra  has  no  prostate,  but  quite  posteriorly  it  has  two  small 
Cowper's  glands,  the  upper  face  of  which  is  covered  by  a  red  muscular  layer  that  leaves  the 
origin  of  the  bulbous  portion  and  is  lost  on  this  surface.  Tl)e  muscles  are  disposed  as  in  the 
Bull.  But  the  spongy  portion  of  the  urethra  is  not  enveloped  by  the  corpus  cavernosum, 
which  is  channeled,  as  in  Solipeds,  by  a  furrow  that  lodges  the  urethra.  The  head  of  the 
penis  is  remarkable  for  two  lateral  folds,  disposed  like  wings  at  the  base  of  the  glans.  One 
of  these  is  only  slightly  developed,  so  that  the  head  of  the  penis  looks  asymmetrical.     The 

Fig.  527. 


PENIS   AND   MUSCLES   OF   THE    PREPUCE   OF   THE   BULL. 

1,  Protractor  muscle  of  the  prepuce;  2,  retractor  of  ditto;  3,  testicles  in  the  scrotum  ;  4,  the  S o( 
the  penis;  5,  suspensory  ligaments  of  the  penis  attached  to  the  second  curve;  6,  subcutaneous 
abdominal  vein. 


urethra  is  also  prolonged  by  a  vermiform  appendix  from  1  to  Ij  inches  long.  (In  the  Ram,  the 
extremity  of  the  urethra  has  tlie  form  of  a  narrow  cylinder  curved  backwards,  its  opening  being 
a  longitudinal  slit.  In  Ruminants,  towards  the  extremity  of  the  prepuce  are  small  teats; 
these,  in  the  He-goat,  are  sometimes  glandular,  and  secrete  a  fluid  analogous  to  milk.) 

Pig. — The  testicles  of  this  animal  are  round,  and  placed  in  the  perinseal  region.  The 
scrotum  is  narrow,  and  but  little  detached :  the  pouches  of  which  it  is  composed  appearing 
simply  as  two  hemispherical  prominences  on  the  surface  of  the  perinseum.  There  is  nothing 
particular  to  be  remarked  in  the  epididymis  and  vas  deferens;  (the  tail  of  the  first  is  very- 
voluminous;  the  latter  has  no  pelvic  dilatation.) 

Tlie  vesiculsB  seminales,  with  regard  to  disposition,  are  intermediate  between  those  of  the 
Horse  and  Ox.  Their  walls  are  thick  and  very  glandular,  and  their  interior  is  diverticulated. 
(They  are,  proportionately,  very  large,  and,  in  structure,  closely  resemble  those  of  Ruminants; 


980  GENERATIVE  APPARATUS, 

indeed,  iu  these  animals  they  rather  appear  to  be  organs  for  the  secretion  of  a  milky  liquid 
that  is  mixed  with  the  semen,  than  reservoirs  for  the  fecundating  material,  as  that  fluid  never 
coataius  any  spermatozoa.)  There  are  two  prostates:  one  disposed  as  in  the  Ox;  the  other 
placed  across  the  neck  of  the  bladder,  as  in  Solipeds.  The  penis  resembles  that  of  Ruminants, 
except  in  tlie  absence  of  the  muscles  of  the  prepuce  ;  it  has  also  a  particular  preputial  sheath, 
which  lias  been  studied  by  Lacauchie.  (When  flaccid,  the  penis  of  the  Pig  is  twisted  in  a 
spiral  manner  at  the  extremity.  The  prepuce  is  narrow,  and  longer  than  in  Ruminants.  At 
the  upper  part  of  its  opening  is  the  special  poucli  mentioned  by  Chauveau,  and  which  is  formed 
by  a  fold  of  the  skin.  It  opens  into  the  prepuce,  and  secretes,  in  the  Boar,  an  unctuous  fluid, 
possessing  a  particularly  disagreeable  smell,  and  which  is  mixed  with  the  urine.  The  odour 
of  the  secretion  even  taints  tlie  flesh  of  this  creature.) 

Carnivora. — The  testicles  of  the  Cat  are  formed  like,  and  placed  in  the  same  situation  as, 
those  of  the  Pig ;  those  of  the  Dog  are  more  oval,  and  are  pendent. 

The  Carnivora  have  no  vesicals  seininales.  Tlie  prostate  gland  surrounds  the  neck  of  the 
bladder;  it  is  of  a  yellow  colour,  concave  on  its  upper  surface,  and  divided  into  two  lateral 
lobes  on  its  lower  face.  Cowper's  glands  are  absent  in  tlie  Dog ;  they  exist  in  the  Cat  (in 
which  they  are  very  small,  and  excrete  their  secretion  by  separate  efferent  canals).  The  urethra 
(in  its  pelvic  portion)  is  very  long;  towards  the  ischial  arch  it  shows  an  enlargement  or  bulb, 
though  this  is  less,  proportionately,  than  in  the  Ox;  the  accelerator  urinae  muscle  is  continued 
for  a  longer  di-stance  around  it.     (The  spongy  portion  is  thinner  in  the  Cat  than  iu  the  Dog.) 

"  In  the  Dog,  the  jjents  is  long  and  pointed.  The  posterior  half  is  constituted  by  the 
corpus  cavernosum,  which  is  little  developed,  and  has  not  a  complete  middle  septum.  The 
anterior  moiety  has  for  its  base  a  bone,  found  in  several  other  manimifers,  which  is  intended  to 
favour  the  introduction  of  the  penis  into  the  genital  organs  of  tiie  female. 

"  The  penien  or  penial  bone  is  elongated,  conical,  and  incurvated,  so  as  to  constitute  a  furrow 
inferiorly,  in  which  is  lodged  the  urethra  when  it  leaves  the  fibrous  chaimel  of  the  corpus 
cavernosum;  its  apex,  anteriorly,  partly  forms  the  point  of  the  penis;  its  base  is  intimately 
united  to  the  anterior  portion  of  the  corpus  cavernosum;  the  median  septum,  which  is  very 
dense,  is  fixed  in  this  bone,  as  is  the  fibrous  envelope  which  mixes  with  its  periosteum. 

"  The  penial  bone  almost  entirely  constitutes  the  base  of  all  that  portion  of  the  penis 
Included  within  the  sheath ;  in  addition,  this  part  possesses  two  distinct  erectile  enlargements — 
an  anterior  and  posterior.  The  first  is  analogous  to  that  of  the  glans  penis  of  the  Horse,  and 
is  formed  by  an  expansion  of  the  erectile  tissue  of  the  urethra ;  club-shaped  at  its  anterior 
base,  it  has  there  a  point  suddenly  bent  downwards,  beneath  which  is  the  urethral  orifice ; 
posteriorly  it  is  thin,  and  partially  covers  the  other  erectile  mass.  Tlie  latter  is  supplementary ; 
it  begins  at  the  base  of  the  free  portion  of  the  penis,  where  the  integument  of  the  sheath  is 
folded  in  a  circular  manner  around  it.  From  1  to  1^  inches  long,  it  embraces  the  upper  border 
and  sides  of  the  bone ;  pyramidal  in  shape,  its  base,  which  is  posterior,  is  from  \  to  l\  inches 
thick;  in  front,  it  thins  away  beneath  the  erectile  tissue  of  the  head. 

"Such  are  the  two  erectile  masses,  the  summits  of  which  overlap,  so  that  the  free  portion  of 
the  penis,  bulging  in  front,  and  still  more  so  behind,  is  narrowest  in  the  middle.  Although 
contiguous,  these  two  vascular  dilatations  are  independent  of  each  other ;  the  posterior  has, 
likewise,  no  communication  with  the  corpus  cavernosum,  and  possesses  two  particular  veins 
which  pass  backward  in  the  lateral  groove.  Each  is  erected  separately  during  copulation, 
when  they  assume  a  large  size ;  the  great  volume  of  tlie  posterior  enlargement  prolongs  the 
duration  of  this  act,  until  flaccidity  ensues.  This  peculiarity  is  a  consequence  of  the  absence 
of  the  seminal  reservoirs  (the  vesiculae  seminales). 

"  In  the  Dog,  two  small  muscles  are  found  which  appear  to  be  destined  to  elevate  the  penis 
and  direct  it  during  its  introduction  into  the  sexual  parts  of  the  female,  as  its  erection  is  always 
feeble.  These  are  two  fasciculi  which  proceed  from  the  crura  of  the  penis,  and  pass  forward 
to  unite  in  a  common  tendon  implanted  on  the  dorsal  border  of  the  organ  ;  they  thus  resemble 
the  cord  of  a  bow. 

"  The  Bubpenial  muscular  cords  exist  as  in  the  other  animals.  The  prepuce  is  narrow  and 
long,  and,  as  in  the  didactyles,  has  protractor  muscles  ;  the  integument  is  thin  and  rose-coloured, 
like  that  covering  the  free  portion  of  the  penis. 

"  In  the  Cat,  the  penis  is  short,  and  directed  backwards ;  but  in  a  state  of  erection  it  is  in- 
elined  forwards  for  copulation.  Its  free  portion  presents  some  peculiarities.  It  is  conical,  and 
its  summit,  near  which  is  pierced  the  urethral  opening,  has  for  its  basis  a  small  incomplete 
penial  bone,  that  encloses  a  layer  of  erectile  tissue — an  expansion  of  that  of  the  urethra.  This 
free  portion  is  covered  by  an  integument  studded  with  somewhat  rigid  papillae  directed  back- 
wards, and  capable  of  being  made  erect  during  copulation.  These  points,  which  are  met  with 
in  nearly  all  the  feline  species,  are  analogous  to  the  hairs,  scales,  strong  spines,  and  even  the 


TEE  GENITAL  ORGANS  OF  THE  MALE.  981 

cartilaginous  saws,  of  certain  other  animals,  and  which  appear  to  be  related  to  the  degree 
of  sensitiveness  of  the  female  sexual  organs  "  (A.  Lavocat). 

Glaiids  annexed  to  the  genital  orgam.—Chatm  has  studied  the  anal  glands  in  the  Dog. 
These  are  two  oval  masses  about  half  an  inch  long,  situated  on  the  sides  of  the  rectum,  at  its 
teriuination.  They  are  covered  by  a  tunic  of  striped  muscular  fibres,  and  are  formed  by  acini 
measuring  from  -05  mm.  to  -07  mm.  and  -10  mm.,  whicli  are  lined  by  polyhedral  cells  of  -009 
mm.  In  the  centre  of  the  gland  is  a  small  reservoir  that  communicates  by  a  short  and  dilatable 
canal  with  the  definitive  excretory  duct;  this  opens  on  the  margin  of  the  anus  by  an  opening 
partially  concealed  by  a  told  of  skin.     The  secretion  is  brownish  and  foetid. 

In  the  young  Dog,  the  general  disposition  is  the  same,  the  constituent  anatomical  elements 
only  being  a  little  smaller. 

In  the  Cat,  the  disposition  of  the  glands  differs  but  little  from  wliat  is  observed  in  the  Dog. 
Roj)Ems.— Vaginal  sheath.— In  the  Rabbit,  the  internal  inguinal  ring  is  very  elongated, 
and  placed  horizontally  below  the  inferior  fiice  of  the  pelvis ;  the  bottom  of  the  scrotal  cavity 
— pyriform — hangs  beneath  the  ischium. 

The  cremaster  muscle  completely  envelops  the  fibrous  tunic ;  the  dartos  is  only  represented 
by  a  few  scattered  fibres  ;  the  scrotum  is  covered  by  long  and  fine  hairs. 

Tes^'c/es.— Tliese  are  ellipsoid  in  shape  and  relatively  voluminous.  They  are  lodged  som'e- 
times  in  the  scrotum,  at  other  times  in  the  abdomen  ;  in  tiie  latter  case,  they  are  attached  to 
the  bottom  of  the  scrotal  sac  by  a  gubernaculum  testis.  The  seminiferous  ducts  are  very 
developed,  and  easily  separated. 

Epididymis—  Vas  de/trens.—The  head  of  the  epididymis  is  flattened,  and  the  tail  forms  a 
conical  and  very  much  detached  appendix.  The  vas  deferens  is  isolated  from  the  vessels  of 
the  testicle  in  the  scrotal  cavity,  so  as  to  form  two  spermatic  cords.  When  the  deferent  canals 
arrive  above  the  bladder,  they  remain  free  and  without  dilatation,  and  open  at  difl'erent  places 
in  the  urethral  canal,  beneath  a  small  valve. 

Vesicula  seminalis.— There  is  only  one— the  male  uterus— Vfith  thin  walls,  lying  on  the 
cervix  and  part  of  the  upper  face  of  the  bladder.  This  vesiculus  terminates,  posteriorly,  by 
a  very  short  canal  placed  in  the  prostate,  and  opening  on  the  surface  of  the  urethra,  above  a 
Talve  situated  between  those  which  cover  the  termination  of  the  deferent  canals. 

Urethra. — This  canal  is  very  dilatable,  and  has  thin  walls  exclusively  membranous  in  its 
terminal  moiety.     It  has  no  erectile  enlargement  at  its  extremity. 

Glands. — The  prostate  of  the  Rabbit  is  oblong  and  voluminous ;  it  lies  across  the  com- 
mencement of  the  urethra,  but  is  prolonged  forward  in  such  a  manner  as  to  cover  the  deferent 
ducts  and  a  great  part  of  the  vesicula  semiualis.  There  are  two  Cowper's  glands,  which  are 
oval  and  enveloped  in  the  sphincter  of  the  urethra. 

Penis. — When  this  organ  is  relaxed,  it  has  a  horizontiil  direction,  parallel  to  the  coccygeal 
region.  Its  total  lengtli  is  about  8  inches— 4  for  the  fixed,  and  4  for  the  free  portion.  The 
dorsal  border  is  thin,  and  the  other  border  has  a  groove  in  which  is  lodged  the  urethra. 

The  penis  is  contained  in  a  prepuce  or  sheath,  the  outer  surface  of  which  is  garnished  with 
longer  hairs  than  those  on  the  neighbouring  parts ;  it  is  also  provided  with  a  retractor  muscle, 
which  is  fixed  around  the  penis. 

The  other  muscles  tliat  act  on  the  penis  are  :  1.  Two  enormous  erectores  penis.  2.  A 
rudimentary  accelerator  urinse  that  seems  to  disappear  towards  the  extremity  of  the  organ.  3. 
A  long,  flat  muscle,  the  fibres  of  which  are  directed  obliquely  downwards  and  backwards, 
commencing,  as  they  do,  on  the  borders  of  the  coccyx,  and  terminating  on  the  sides  of  the  deeper 
portion  of  the  corpus  caveruosum  ;  in  contracting,  this  muscle  draws  the  penis  from  the  inferior 
face  of  the  coccygeal  vertebrse.  4.  A  muscle  formed  of  two  bellies,  attached  to  the  ischiatic 
arch,  and  prolonged  behind  by  a  tendon  which  is  fixed  on  the  dorsum  of  tlje  penis.  This 
muscle — which  we  propose  to  name  the  subischio-cavernous  (suberectores  penis) — plays  an 
important  part  in  copulation.  We  have  observed,  while  injecting  the  penis,  that  the  organ  in 
a  state  of  erection  is  vertical ;  but  this  position  is  unfavourable  for  sexual  intercourse,  and  then 
it  is  that  the  muscle  intervenes,  for  when  it  contracts  it  raises  the  penis  towards  the  abdomen, 
and  renders  coition  possible. 

Glands  annexed  to  the  genital  organs. — Below  the  root  of  the  tail,  on  each  side  of  the  anus 
and  prepuce,  are  two  large  shallow  cavities  lined  by  white  skin,  moist  and  destitute  of  hair. 
In  the  centre  of  these  cavities  is  a  papilla  with  an  opening  in  its  summit ;  this  papilla  corre- 
sponds to  the  anal  gland. 

The  anal  glands  are  conical,  and  formed  of  two  little  superposed  masses — one  brown  in 
colour,  the  other  yellow-tinted.  They  are  constituted  by  a  number  of  glandular  acini,  that 
secrete  a  fatty  unctuous  matter.  At  the  bottom  of  these  cavities  also  open  the  excretory  duct 
of  two  other  undescribed  glands.     These  are  situated  deeply  on  each  side  of  the  rectum  ;  they 


982  GENERATIVE  APPARATUS. 

are  yellow  in  colour,  and  are  formed — like  the  preceding — of  acini,  the  cells  of  which  contun 
much  fat.     Because  of  their  situation,  we  have  named  these  the  rectal  glands. 

We  have  also  studied  tlie  generative  organs  of  the  Leporide — a  new  or  hybrid  species 
which  has  been  the  subject  of  much  discussion ;  and  have  remarked  that  there  is  a  perfect 
resemblance  between  these  organs  in  a  male  Leporide  and  those  of  the  Rabbit.  The  testicles 
found  in  the  abdomen  have  furnished  a  fluid  rich  in  very  vivacious  spermatozoids.  These 
Leporides  have,  therefore,  all  that  is  necessary  for  reproduction  inter  se.' 

Comparison  of  the  Genital  Organs  of  Man  with  those  op  Animals. 

Coverings  of  the  testicles. — The  scrotum,  dartos,  tunica  erythryoidea,&nd  tunica  vaginalis  have 
the  sume  organization  as  in  Solipeds.  The  scrotum  is  rich  in  sebaceous  glands,  and  the  tunica 
vaginalis  is  separated  by  a  serous  layer  from  the  peritoneal  cavity. 

Testicles. — These  are  ovoid,  and  situated  in  an  oblique  direction  downwards  and  inwards ; 
their  largest  curvature  is  forwards. 

The  epididymis  ofl'ers  the  same  arrangement  as  already  noticed,  except   that   the   vm 


Fig.  528. 


16 

SECTION   OF   PELVIS   TO   THE    LEFT   OF   THE    MEDIAN    LINE    AT   THE    PUBES,    AND   THROUGH 
THE    MIDDLE   OF   THE   SACRUM. 

1,  Section  of  left  pubic  bone;  2,  peritoneum  on  bladder;  3,  left  crus  penis;  4,  pelvic  fascia 
forming  anterior  ligaments  of  bladder ;  5,  part  of  accelerator  urina; ;  6,  posterior  layer  of 
triangular  ligament  forming  the  capsule  of  the  prostate ;  7,  anterior  layer  of  triangular 
ligament;  between  6  and  7  are  seen  the  membranous  urethra,  deep  muscles  of  urethra  (insertion), 
and  Cowper's  gland  of  the  left  side;  8,  vas  deferens;  9,  bulb  of  urethra;  10,  rectum;  11,  cut 
edges  of  accelerator  urinse  and  transversus  perinaei ;  12,  left  ureter;  13,  reflection  of  deep  layer 
of  superficial  fascia  round  transversus  perinaei ;  14,  left  vesicula  seminalis  ;  15,  cut  edge  of 
levator  ani ;   16,  rectum  ;  17,  prostate  gland. 

deferens,  in  being  detached  from  the  globus  minor,  is  bent  somewhat  suddenly  to  reach  the 
abdominal  cavity.  There  are  several  diverticuli  annexed  to  the  epididymis,  named  the  pedicu- 
lated  hydatid  of  Morgagni,  non-pediculated  hydatid  aberrant  vessels,  and  corpus  innominatum  of 
Giraldes. 

The  hydatid  of  Morgagni  is  a  little  projection  at  the  head  of  the  epididymis,  filled  with  a 
serous  fluid  which  is  never  mixed  with  the  semen.  The  non-pedicidated  hydatid  is  a  small 
white  mass  which  rises  from  the  testicle  at  some  distance  from  the  globus  major ;  it  has  a 
cavity  that  communicates  witli  the  duct  of  the  epididymis.  The  aberrant  vessels  are  fine 
flexuous  ducts  given  off"  from  the  globus  minor,  and  soon  terminate  in  a  cul-de-sac.  The  corpus 
innominatum  of  Giraldes  is  a  small  mass  of  ramifying  tubes  included  in  the  connective  tissue 
uniting  the  globus  majnr  to  the  testicle.  All  these  anpendages  of  the  testicle  or  epididymis, 
are  the  remains  of  the  Wolffian  body. 


For  further  details,  see  Arloing,  "  Etude  Comparative  sur  les  organes  genitaux  du  Lifevre^ 
du  Lapin  et  du  Leporide,"  in  Robin's  Journal  de  I'Anatomieet  de  la  Physiologie  for  1868. 


THE  GENITAL   ORGANS  OF  THE  FEMALE.  983 

Vas  deferens. — This  is  not  united  to  its  fellow  by  a  peritoneal  fold ;  it  is  slightly  dilated  on 
arriving  at  the  neck  of  tlie  bladder,  as  in  the  Horse.  The  vesiculse  seminales  are  elongated, 
and  lobulated  on  their  surface,  as  in  Ruminants. 

Urethra. — Tliis  canal  has  a  fixed  and  a  free  portion  :  the  first  is  sliglitly  inclined  downwards 
and  forwards ;  the  second  is  suddenly  inflected,  and,  with  the  preceding,  forms  the  prepubio 
angle,  which  disappears  with  erection.  Its  diameter  increases  a  little  at  the  bulb,  and  again 
at  the  meatus,  to  form  the  fossa  navicularis.  Its  erectile  envelope  forms  a  considerable  enlarge- 
ment at  its  commencement — the  6mZ6,  and  this  is  covered,  as  in  the  Ox,  by  the  accelerator 
urinaB;  it  also  composes  another,  the  glans,  that  constitutes  the  head  of  the  penis.  Oii  its  inner 
surface  are  some  valvular  folds,  and  some  depressions — the  lacunm  of  Morgagni,  the  verumon- 
tanum — and  towards  the  summit  of  this  a  email  poucli — the  male  uterus  {sinus  pocularis) 
which,  on  a  very  reduced  scale,  represents  the  third  vesicula  df  Solipeds.  The  muscles  of  the 
urethra  are  the  ischio-cavernosum^  accelerator  rsinir;,  Wilson's  muscle,  and  the  transversus 
perinaei— superficial  and  deep.  On  emerging  from  the  pelvic  cavity,  the  urethra  traverses  an 
aponeurotic  membrane  named  the  ligament  of  Carcassonne. 

Corpus  cavernosum. — This  oflfers  nothing  particular  in  its  disposition. 

Penis. — This  organ  is  free,  and  is  suspended  in  front  of  the  pubis.  It  is  enveloped  by  a 
fibrous  covering — the  superficial  fascia,  and  a  cutaneous  cylinder — the  prepuce.  It  is  attached 
by  two  suspensory  ligaments:  the  superficial  is  elastic,  and  arises  from  the  linea  alba;  the 
deep  is  inelastic,  and  is  detached  from  the  symphysis  pubis  and  the  anterior  pillar  of  the 
inguinal  ring.  (It  is  usual  to  describe  only  one  ligament — the  Ugamentum  suspensorium  penis, 
separating  to  form  two  layers  which  give  passage  to  the  dorsal  vessels,  and  nerves  of  the  penis.) 
The  glans  is  separated  from  the  rest  of  the  organ  by  a  constriction  designated  the  cervix,  and 
around  this  the  skin  forms  a  (circular)  fold — the  prepuce,  which  covers  the  glans  more  or  less 
completely.  It  is  attached  to  the  middle  of  its  lower  face  by  a  thin  fold — ihefrsenum  prssputii. 
The  inner  surface  of  the  prepuce  has  a  large  number  of  sebaceous  glands. 


CHAPTER   IL 
GENITAL   ORGANS   OF   THE   FEMALE. 

Preparation. — In  dissecting  the  female  generative  organs,  their  normal  relations  should  be 
preserved  as  much  as  possible  by  preparing  the  subject  as  in  Fig.  536. 

1.  Place  the  subject  in  the  first  position,  carefully  removing  the  skin  covering  the  perinaeum 
and  mammae,  the  [lart  of  the  abdominal  walls  on  v/hich  the  latter  rest  being  left,  but  the  intes- 
tines removed  according  to  the  usual  procedure — a  portion  of  the  floating  colon  being  only 
allowed  to  remain,  i'inally,  the  posterior  part  of  the  trunk  is  cut  away  by  sawing  through 
the  spine  at  the  sixteenth  dorsal  vertebra. 

2.  Before  proceeding  to  dissect,  it  is  well  to  inject  the  bulb  of  the  vagina  by  the  internal 
pudic  artery  near  its  origin,  and  the  uterus  and  bladder  c^ould  be  inflated. 

To  inflate  the  uterus,  the  following  is  the  procedure :  tlio  cervix  is  made  to  project  through 
an  incision  in  the  middle  line  of  the  wall  of  the  vagina;  then  a  straw  or  inflating  tube  is 
introduced  into  the  uttrus,  and  air  injected  thereby ;  when  sufliciently  distended,  the  cervix  is 
firmly  tied  with  a  waxed  thread.  The  bladder  fr:  distended  by  injecting  air  through  a  ureter, 
after  closing  the  urethra;  this  is  done  by  finding  the  meatus  urinarius  with  the  index  finger 
of  the  left  hand ;  a  hook  is  then  placed  on  the  orifice,  which  is  drawn  to  the  vulva,  where  two 
pins  are  pushed  crossways  through  its  mucous  menibrane  and  a  ligature  of  waxed  thread  tied 
behind  these;  the  points  of  the  pins  are  cut  ofi",  and  the  parts  allowed  to  resume  their  natural 
position. 

Finally,  the  vagina  and  rectum  are  slightly  distended  by  means  of  bundles  of  tow. 

3.  When  these  preparations  are  completed,  one  of  the  posterior  limbs  is  disarticulated; 
the  upper  part  of  the  gluteal  and  posterior  crural  muscles,  as  well  as  a  portion  of  the  sacro- 
Bciatic  ligament,  are  cut  away.  In  removing  the  cellulo-adipose  tissue  from  the  pelvic  cavity, 
the  neok  of  the  bladder,  the  rectum,  and  the  vulva  are  freed ;  care  should  be  taken  not  to 
injure  the  peritoneal  fold  that  surrounds  the  nn'ddle  region  of  the  vagina.  The  constrictor 
muscle  of  the  vulva  is  exposed  in  removing  the  skin  by  shreds  with  scissors,  as  was  done  with 
the  orbicularis  muscle  of  the  lips.  Afterwards,  the  portion  of  the  ischium  which  conceals  some 
portions  of  the  details  of  the  preparation  is  removed  by  the  saw. 


984  GENERATIVE  APPARATUS. 

4.  When  the  organs  have  been  studied  in  situ,  tliey  are  removed — the  broad  ligaments 
being  preserved— and  sprciid  on  a  table,  in  order  to  study  their  interior. 

5.  An  injection  into  the  galactopliorous  sinus  allows  a  good  idea  to  be  formed  of  the 
general  disposition  of  the  mammary  gland. 

These  organs  resemble  those  of  the  male  in  their  general  disposition.  Thus 
we  find  in  the  female  :  1.  Two  secretory  organs — the  ovaries — analogous  to  the 
testicles,  in  which  the  germ  is  elaborated.  2.  The  uterine  (Fallopian)  tube, 
disposed — like  the  epididymis  and  vas  deferens— as  a  flexuous  canal,  through 
which  the  ovum  passes  on  leaving  the  ovary.  3.  The  uterus,  a  single  reservoir 
formed  of  two  lateral  moieties  which  may  be  compared  to  the  vesiculte  seminales, 
as  it  is  there  that  the  germ  remains  until  it  is  fully  developed.  4.  The  vagina, 
a  membranous  canal  analogous  to  the  urethra,  and  giving  passage  to  the  foetus 
after  it  has  been  formed  in  the  uterus  :  this  canal,  which  receives  the  penis 
during  copulation,  also  shows,  at  its  exterior  opening,  the  vulva — an  erectile 
apparatus — and  the  clitoris,  which  is  nothing  more  than  a  rudimentary  corpus 
cavernosum  of  the  male.  The  female  has  also  certain  glands,  which,  in  many 
species,  exist  in  a  rudimentary  form  in  the  male  :  for  instance,  the  mammae, 
organs  for  the  secretion  of  milk,  the  first  nourishment  of  the  young  animal. 

(The  glands  of  Duverney,  in  the  female  vagina,  seem  to  be  analogous  to 
Cowper's  glands  in  the  male,  as  they  are  present  in  the  females  of  all  animals 
where  the  latter  exist  in  the  male,  and  their  secretion  appears  to  be  of  the  same 
character.) 

It  may  be  remarked,  after  this  observation,  that  the  male  and  female  genital 
apparatuses  are  constructed  on  the  same  type — a  circumstance  which  is  most 
clearly  demonstrated  at  an  early  period  of  intra-uterine  life,  when  it  is  impossible 
to  distinguish  the  sexes. 

1.  The  Ovaries  (Figs.  529,  535). 

Situation — Form — Relations. — The  ovaries  (testes  muliehres) — the  essential 
organs  of  generation  in  the  female — are  two  ovoid  bodies,  smaller  than  the 
testicles,  though  of  the  same  shape,  situated  in  the  abdominal  cavity,^  and 
suspended  from  the  sublumbar  region — where  they  correspond  with  the  intestinal 
convolutions — a  little  behind  the  kidneys.  Smooth  on  the  surface,  these  organs 
present,  in  the  middle  of  their  upper  face,  a  deep  and  more  or  less  oblique 
fissure,  resembling  the  hilus  of  the  kidney  ;  this  gives  attachment  to  the  paviUon 
of  the  tube. 

Means  of  attachment.  —The  ovary  floats  at  the  anterior  border  of  the  broad 
ligament ;  it  is  also  sustained  by  the  vessels  that  enter  it,  and  by  a  small  cord  of 
unstriped  muscular  fibres — the  ligament  of  the  ovary — which  attaches  it  to  the 
uterus. 

Structure. — The  organization  of  the  ovaries  comprises  a  serous  membraney 
a  tunica  albuginea,  proper  tissue,  and  the  Graafian  vesicles  embedded  therein. 

Serous  membrane. — This  is  a  continuation  of  the  broad  ligaments  ;  it  covers 
the  whole  organ  (except  at  the  hilus),  adhering  closely  to  the  tunica  albuginea. 

Tunica  alhwjinea. — This  is  similar  to  that  enveloping  the  testicle,  being  a 
very  resisting  fibrous  covering  which  sends  prolongations  into  the  substance  of 
the  ovary. 

»  Tlie  ovaries  sometimes  leave  this  situation.  Thus  Dupont,  of  Plazac,  has  observed  them, 
in  four  swine,  occupying  little  cavities,  analogous  to  those  of  the  male  scrotum,  in  the  perinseaj 
region  {Journal  des  Vet^rinaires  du  Midi,  December,  1869). 


THE  GENITAL   ORGANS  OF  THE  FEMALE. 


985 


On  the  surface  of  this  fibrous  membrane  is  found  a  complete  layer  of 
cylindrical  cells,  which  was  at  one  time  regarded  as  a  dependency  of  the  peritoneal 
serous  membrane  ;  but  it  differs  widely  from  it  in  an  anatomical  point  of  view. 
It  is  named  the  germ-epithelium,  in  order  to  indicate  the  share  it  takes  in  the 
production  of  ova  during  the  early  period  of  their  development. 

Proper  tissue. — The  proper  tissue,  or  stroma,  of  the  ovary  is  more  consistent 
than  that  of  the  testicle  ;  it  is  hard,  grates  on  being  cut  into,  and  is  greyish-red 
in  colour.  It  is  divisible  into  two  layers,  distinguishable  by  their  aspect  and 
structure  (Fig.  529). 

1.  The  medullar^/  layer — that  nearest  the  hilus— is  slightly  red  and  spongy ; 


SECTION   OF    THE   OVARY. 

1,  Cortical  vesicles;  2,  larger  vesicles;  3,  vesicles  surrounded  by  the  granular  membrane;  4,  5.  6, 
7,  8,  follicles  in  various  stages  of  development;  9,  membrana  granulosa;  10,  ovum;  11,  cumulus 
proligerus;  12,  non-ruptured  follicle  surrounded  by  a  capillary  network;  13,  follicle  with  its 
contents  partly  escaped  ;  14,  stroma  of  the  cortical  zone ;  15,  vessel  entering  by  the  hilus  of  the 
ovary;  16,  stroma  of  the  hilus;  17,  external  membrane  of  a  corpus  lutea ;  18,  arteries  of  a 
corpus  lutea  ;  19,  its  central  vein. 


it  is  formed  by  an  interlacing  of  the  connective  fibres,  unstriped  muscular  fibres, 
and  a  large  number  of  vessels  that  radiate  from  the  centre  towards  the  peripheiy. 

2.  The  cortical  layer  has  the  elements  of  connective  tissue  for  its  base  ;  it  is 
but  little  vascular,  and  contains  in  its  substance  the  Graafian  vesicles  or  follicles 
{ovisacs),  and  is  consequently  often  named  the  ovigenous  layer.  These  ovisacs 
are  in  various  stages  of  development ;  the  smallest  are  situated  beneath  the 
tunica  albuginea,  and  gradually  increase  as  they  lie  deeper.  When  fully 
developed,  they  are  filled  with  a  transparent,  citron-coloured  fluid ;  the 
ovigenous  layer  can  then  no  longer  contain  them,  and  they  protrude  more  or  less 
from  the  surface  of  the  ovary. 

A  Graafian  vesicle,  in  its  perfect  state,  is  composed  of  an  envelope  and  its 
contents.  The  envelope  comprises  :  a  fibrous  membrane  {tunica  fibrosa),  which 
is  confounded  with  the  stroma  of  the  ovary,  and  in  it  we  may  recognize  two 
layers,  the  internal  of  which  is  rich  in  vessels ;   an  epithelium,  or  membrana 


GENERATIVE  APPARATUS. 


granulosa,  consisting  of  round  or  polygonal  granular  cells.  At  the  bottom  of 
the  ovisac,  this  epithelium  forms  a  small  mass — the  cumulus  proUgerus  (oi 
germinal  eminence),  in  the  centre  of  which  is  the  ovulum  or  eo^or  of  the  mammal. 
The  rontejits  {liquor  folliculi)  is  a  clear  yellow  fluid,  which  becomes  red  on 
admixture  with  blood  when  the  vesicle  ruptures. 

The  ovulum,  or  ovum,  is  a  cell  about  -j^^  of  an  inch  in  diameter,  enclosed  in 
the  discus  proUgerus,  or  cumulus  proUgerus.  The  ovum  is  invested  by  a  thick 
membrane — the  zona  pellwida  {membrana  vitellina),  formed  of  cells  traversed  by 
radiating  canals — the  porous  canalicuU  (ova-tubes) ;  its  granular  contents  are 
named  the  viteUus,  or  ijolk ;  and  its  (vesicular  nucleated)  nucleus,  designated  the 
germinal  vesicle,  or  vesicle  of  Purkinje,  and  lying  at  a  certain  point  on  the  zona 
pellucida,  has  in  its  centre  a  white  patch — the  germinal  spot,  or  spot  of  Wagner. 

Balbiani  has  discovered,  alongside  the  germinal  vesicle,  another,  which  he  has 
named  the  embryogenic  vesicle. 

Vessels  and  nerves. — The  thick,  flexuous,  arterial  divisions  are  given  off  by 
•  the  utero-ovarian  artery;    they 

^'--  ^^^-  ramify  in  the  spaces  formed  by 

the  tunica  albuginea,  before 
reaching  the  proper  tissue  by 
entering  the  hilus.  The  veins., 
are  of  large  calibre,  and  form  a 
very  rich  network  around  the 
gland — the  bulb  of  the  ovary ; 
they  terminate  in  the  vena  cava, 
near  the  renal  veins.  The  lym- 
phatics  are  very  abundant  in  the 
medullary  substance,  and  anas- 
tomose in  a  network  around  the 
follicles  before  they  pass  to  the 
sublumbar  glands.  The  nerves 
emanate  from  the  small  mesen- 
teric plexus. 

Development. — The  ovary 
of  Solipeds  is  of  great  size  in  the 
foetus,  being  often  nearly  as  large 
as  in  the  adult  animal.  Fig. 
530  exhibits  the  proportion  between  its  volume  and  that  of  the  uterus  in  a  six 
months'  foetus.     It  becomes  atrophied  in  aged  animals. 

Functions. — The  productive  organs  of  the  germ,  or  ovum,  the  ovaries  are 
the  testicles  of  the  female.  They  form  the  ova,  and  then  at  certain  periods  set 
them  at  liberty.  As  the  ova  are  contained  in  the  Graafian  vesicles,  it  is  necessary 
to  study  :  1.  The  development  of  these  vesicles.  2.  Their  rupture,  or  dehisence. 
3.  The  phenomena  occurring  in  them  after  rupture. 

Development  of  the  Graafian  vesicles. — The  use  of  the  Graafian  vesicles  is  to 
remove  the  ova  from  the  ovary — to  prepare  their  dehiscence  ;  consequently,  the 
development  of  these  vesicles  is  subordinate  to  the  presence  of  ova.  The  latter 
begin  to  form  among  the  cells  of  the  germ-epithelium  covering  the  surface  of 
the  ovary  ;  then  they  become  deeply  embedded  in  the  organ  by  means  of  Pfliiger's 
cords,  thrown  out  by  the  germ-epithelium. 

When  the  ovum  is  thus  buried  in  the  stroma  of  the  ovary,  the  epitheUum 


OVARIES,    OVIDUCTS,    AND   UTERUS   OF   A    FO^.TCS 
(EQUINE). 


TEE  GENITAL   ORGANS  OF  THE  FEMALE. 


Fig.  531. 


accompanying  it  proliferates  and  forms  two  layers — membrana  granulosa — around 
them.  The  surrounding  connective  tissue,  pressed  out,  accommodates  itself  to 
the  surface  of  the  mass,  and  gradually  constitutes  a  spherical  shell-^the  fibrous 
envelope  ;  then  the  Graafian  vesicle  is  formed.  Soon  the  two  layers  of  the 
membrana  granulosa  separate  at  one  part  to  form  a  cavity — the  cavity  of  the 
vesicle  (Fig.  529,  5,  6,  7) ;  but  as  the  separation  is  not  complete,  the  ovum, 
encircled  by  the  internal  membrane,  lies  beside  the  external  membrane.  As  the 
cavity  of  the  vesicle  enlarges,  the  tissue  of  the  ovary  becomes  more  condensed, 
and  constitutes  the  fibrous  wall,  which  soon  receives  a  network  of  vessels. 

(This  description  does  not  altogether  agree  with  what  is  taught  by  physiologists. 
It  would  appear  that,  in  the  course  of  development,  groups  of  cylindrical  cells 
grow  up  from  the  stroma  of  the  ovary  so  as  to  enclose  the  primordial  ova. 
These  may  even  form  tubular-like  structures,  called  by  some  German  writers  the 
ova-tubes.  By-and-by,  each  ovum  is  surrounded  by  cells,  forming  a  httle  round 
body  called  the  primary  follicle,  which  consists  of  the 
ovum  and  of  epithelial  cells  surrounding  it.  The  forma- 
tion of  this  follicle  around  each  ovum  is  for  the  purpose, 
in  due  time,  of  ejecting  the  ovum  from  the  ovary.  The 
size  of  the  follicle  increases  by  the  multiplication  of 
epithehum-cells,  and  soon  a  space  exists  round  the  ovum 
which  is  filled  with  a  fluid — the  liquor  follkuU.  This 
liquid  may  be  formed  by  transudation  from  the  surround- 
ing blood-vessels,  and,  as  some  have  suggested,  by  the  dis- 
integration and  melting  away  of  some  of  the  epithelial 
cells.  We  have  now  a  vesicle  filled  with  fluid — the 
Graafian  vesicle — having  a  diameter  of  from  '5  to  5  mm. 
The  connective  tissue  forms  the  wall  of  the  vesicle.  It 
consists  of  :  1.  A  connective  tissue  covering  the  them  folli- 
cuU,  which  is  formed  of  two  strata — an  outer  of  fibrous 
tissue,  tunica  fibrosa ;  and  an  inner,  tunica  propria,  rich 
in  cells  and  vessels.  2.  A  lining  of  stratified  folHcular 
epithelium,  sometimes  called  the  membrana  granulosa. 
This  lining  of  epithelium-cells  forms  a  prominence  at  one 
side,  called  the  cumulus  ovigerus,  or  discus  proligerus,  and 
the  layer  surrounding  the  ovum  has  been  termed  the 
tunica  granulosa.  The  space  is  occupied,  as  already  men- 
tioned, by  the  liquor  folliculi.  When  the  ovum  reaches 
maturity,  the  Graafian  vesicle  is  full  of  fluid,  and  bluges  out  from  the  surface  of 
the  ovary.  It  may  be  mentioned  that  the  primordial  ovum  is  a  large  round  cell, 
provided  with  a  nucleus  and  nucleolus  ;  it  originates  from  a  single  cell  of  the 
germ-epithelium. 

In  the  Cow,  at  puberty  the  stroma  of  the  ovary  is  crowded  with  follicles  so 
minute,  that  it  has  been  computed  that  a  cubic  inch  would  contain  two  hundred 
millions  of  them. 

Puberty  occurs  earlier  in  small  than  in  large  animals.  In  the  Rabbit, 
Guinea-pig,  Rat,  and  Birds,  it  is  reached  during  the  first  year  ;  in  the  Dog  and 
Cat,  in  the  second  year  ;  in  the  Ox,  Horse,  and  Lion,  in  the  third  year ;  in  the 
Camel,  in  the  fifth  year  ;  and  in  the  Elephant,  between  the  twentieth  and  thirtieth 
year.  Menstruation — or  a  series  of  phenomena  resembling  this  function  in 
Woman — occurs  in  many  animals,  and  is  known  as  the  rut,  or  heat.    Cows  and 


OVARItTM  OF  THE  RABBIT 
AT  THE  PERIOD  OF 
CESTRUM,  SHOWING 
VARIOUS  STAGES  OP 
THE  EXTRUSION  OP 
OVA. 


988  GENERATIVE   APPARATUS. 

Sheep  rut  twice ;  the  Cat,  Bitch,  and  Sow,  two  or  three  times  ;  and  the  Rabbit 
and  Guinea-pig,  eight  or  twelve  times,  in  the  course  of  the  year.  The  condition 
lasts  in  the  ^lare  and  Cow  from  two  to  four  days,  and  in  the  Sow  and  Bitch 
from  six  to  ten  days.  During  this  period  the  females  have  a  peculiar  smell,  by 
which  the  males  are  attracted,  even  from  long  distances.) 

Rupture  of  the  Graafian  vesicles. — After  puberty  the  ovary  becomes  vascularized, 
and  a  certain  number  of  Graafian  vesicles  increase  in  volume.  At  the  period  of 
oestrum,  one  or  more  of  these,  according  to  the  species,  participate  in  the  change 
in  the  ovary,  become  vascular  and  distended,  and  finish  by  rupturing  and 
evacuating  the  discus  proligerus  and  ovum.  The  latter  is  received  into  the 
Fallopian  tube  and  conveyed  towards  the  uterus. 

Corpus  luteum. — After  the  rupture  of  a  Graafian  vesicle,  its  cavity  is  filled 
by  a  clot  of  blood,  which  gradually  contracts  and  loses  its  colom* ;  at  the  same 
time  the  tunica  fibrosa  becomes  hyDertrophied,  and  the  membrana  granulosa  is 
wrinkled  and  transformed  into  cylindrical  epithelium.  To  this  period  of 
progression  succeeds  one  of  regression,  during  which  the  cylindrical  cells  become 
infiltrated  with  fat  and  are  graduall  absorbed.  The  term  corpus  luteum  is 
given  to  the  cicatrix  resulting  from  the  rupture  of  a  Graafian  vesicle. 


Fig.  532. 


Fig.  533. 


CONSTITUENT    PARTS  OF    A   KAMMALIAI 


Fig.  532,  Entire  ovum.     Fig.  533,  Ovum  ruptured,  with  the  contents  escaping:  mv,  vitelline 
membrane ;  _/,  yolk ;  vg,  germinal  vesicle  ;  tg,  germinal  spot. 


The  progress  of  the  phenomena  of  hypertrophy  and  regression  is  much  slower 
when  the  escape  of  the  ovum  has  been  followed  by  impregnation  ;  so  that  we 
have  false  corpora  lutea  (those  which  are  independent  of  pregnancy),  and  true 
corpora  lutea,  those  of  gestation,  and  which  do  not  disappear  until  several  weeks 
after  parturition.  (The  true  corpora  lutea  are  recognizable,  after  parturition, 
as  small  white  or  dark-coloured  masses — the  corpora  albicans  vel  nigrum.  The 
yellow  colour,  to  which  they  owe  their  name,  is  due  to  the  infiltration  of  the 
cylindrical  cells  with  fat.) 

During  early  life  the  Graafian  follicles  are  not  inert,  as  has  been  believed,  but 
are  active  ;  only  instead  of  rupturing  and  throwing  their  contents  into  the 
Fallopian  tubes,  after  attaining  their  full  development  they  shrivel,  become 
atrophied,  and  eventually  nothing  is  left  of  them  except  a  very  small  yellow 
body. 

Such  are,  very  briefly,  the  functions  of  the  ovary. 

(Beneath  the  hilus  of  the  ovary,  and  between  the  layers  of  the  broad  liga- 
ment and  the  round  ligament,  is  found  a  small  body,  usually  described  as  the 
'parovarium  or  epoophoron,  consisting  of  a  number  of  fine  tubes  or  tortuous  canals 


THE  GENITAL   ORGANS   OF  THE  FEMALE.  989 

with  blind  extremities  lined  with  ciliated  cylindrical  epithelium.  It  is  considered 
as  the  remains  of  the  Wolffian  body  -  a  foetal  structure  that  forms  the  epididymis 
in  the  male,  and  has  been  named  the  orga?i  of  Rosenmiiller  in  the  female. 
Chauveau  does  not  mention  its  existence  in  the  domesticated  animals,  though 
Leyh  does.  There  is  also  the  paroophoron,  likewise  found  in  the  broad  ligament, 
and  formed  of  small  canals  lined  with  cylindrical  cells.  This  is  supposed  to  be 
a  relic  of  the  urinary  portion  of  the  Wolffian  body.) 

2.  The  Fallopian  or  Uterine  Tubes,  or  Oviducts  (Fig.  535,  2). 

The  Fallopian  tube  is  a  little  flexuous  canal,  lodged  in  the  broad  ligament, 
near  its  anterior  border.  It  commences  at  the  ovary  by  a  free,  expanded 
extremity — the  pavilion  of  the  tube  (or  ostium  abdominah),  and  terminates  in  the 
cul-de-sac  of  the  uterine  cornu  by  opening  into  it  (the  ostium  uterinum).     Its 

Fig.  534. 


9 

SUCCESSIVE   STAGES   IN   THE   FORMATION   OF   THE   CORPUS   LUTECM   IN   THE   GRAAFIAN 
FOLLICLE   OF   A    SOW   (VERTICAL   SECTION). 

a,  The  follicle  immediately  after  the  expulsion  of  the  ovum,  its  cavity  being  filled  with  blood,  and 
no  ostensible  increase  of  its  epithelial  lining  having  yet  taken  place;  at  b,  a  thickening  of  this 
lining  has  become  apparent ;  at  c,  it  begins  to  present  folds,  which  are  deepened  at  d,  and  the  clot 
of  blood  is  being  absorbed  and  decolorized  ;  a  continuance  of  the  same  process,  as  shown  at  e,f,  g,  h, 
forms  the  corpus  luteum,  with  its  stellate  cicatrix. 

canal  at  the  middle  is  so  narrow  as  scarcely  to  admit  more  than  a  very  thin 
straw,  and  its  calibre  is  still  less  towards  the  uterine  extremity  ;  near  the  ovary, 
however,  it  is  wide  enough  for  the  passage  of  a  thick  goose-quill. 

The  orifice  of  the  uterine  extremity  opens  in  a  small  and  very  hard  tubercle. 
The  ovarian  extremity,  in  all  Mammalia,  offers  a  very  remarkable  arrangement. 
It  opens  into  the  peritoneal  cavity,  near  the  fissure  of  the  ovary,  and  in  the 
centre  of  the  expansion  named  the  pavilion  of  the  tube,  which  is  also  designated 
the  fimbriated  extremity  (or  morsus  diaboli).  This  pavilion  is  attached  to  the 
external  side  of  the  ovary,  and  has  a  very  irregular  outline — notched,  as  it  is, 
into  several  lancet-shaped,  unequal  prolongations  {fimbria),  which  float  freely  in 
the  abdomen.  Here  are,  then,  two  important  anatomical  facts — the  discontinuity 
between  a  gland  and  its  excretory  duct,  and  the  communication  of  a  serous  cavity 
fvith  the  exterior. 

Structure. — The  Fallopian  tube  is  formed  of  a  serous,  a  muscular,  and  a 

mucous  tunic.     The  serous  {external)  is  furnished  by  the  broad  ligament,  and  is 

derived  from  the  peritoneum.    The  middle  is  formed  of  unstriped  muscular  fibres, 

which  extend  into  the  pavilion.     (They  are  arranged  as  circular — internal,  and 

65 


990  GENERATIVE  APPARATUS. 

longitudinal — external  fibres,  and  are  continuous  with  those  of  the  uterus  ;  they 
are  mixed  with  embryonic  nucleated  connective  tissue.)  The  mucous  membrane 
is  arranged  in  longitudinal  folds  in  the  tube,  but  in  the  pavilion  these  folds  are 
radiating  ;  it  is  covered  by  a  ciUated  cylindrical  epithelium  (the  vibrations  of  the 
cilia  being  towards  the  uterus).  (It  has  very  few  glands  and  no  villi.)  At  the 
margin,  or  fimbriae,  of  the  pavilion  it  suddenly  ceases,  and  is  continued  by 
the  peritoneum  (a  serous  cyst  is  frequently  found  in  this  situation  ;  at  the  other 
extremity  the  mucous  membrane  is  continuous  with  that  of  the  uterus). 

Functions. — The  excretory  duct  of  the  ovary,  the  Fallopian  tube  seizes  the 
ovum  expelled  from  the  Graafian  vesicle,  and  carries  it  to  the  uterus.  It  is  there- 
fore necessary  that,  at  the  moment  of  rupture  of  the  vesicle,  the  fimbriae  should 
be  applied  to  the  ovary,  in  order  to  receive  the  germ  and  bring  it  to  the  abdominal 
orifice  of  the  tube.  The  application  of  the  pavilion  to  the  ovary  is  brought  about, 
either  by  the  contraction  of  the  muscular  fibres  it  contains,  or  through  the  dis- 
tension of  the  bulb  of  the  ovary.  Sometimes  this  mechanism  is  insufficient,  and 
the  ovum  falls  into  the  abdominal  cavity,  becomes  fixed  there,  and  is  developed 
if  it  has  been  previously  fecundated ;  this  occurrence  constitutes  the  most 
remarkable  variety  of  extra-uterine  gestation. 

The  oviduct  also  conveys  the  seminal  fluid  of  the  male  to  the  ovum. 

3.  The  Uterus  (Figs.  535,  536). 

The  uterus  is  a  membranous  sac  to  which  the  ovum  is  carried,  and  in  which 
it  is  developed. 

Situation. — It  is  situated  in  the  abdominal  cavity,  in  the  sublumbar  region, 
at  the  entrance  to  the  pelvic  cavity,  where  its  posterior  extremity  is  placed. 

Form  and  relations. — In  its  posterior  moiety,  the  uterus  is  a  single  cylindrical 
reservoir,  slightly  flattened  above  and  below  ;  this  is  the  body  of  the  uterus.  Its 
anterior  moiety  is  bifid,  and  gives  rise  to  two  cornua,  which  curve  upwards. 

The  bod//  is  related,  by  its  upper  face,  to  the  rectum,  which  lies  on  it  after 
passing  between  the  two  cornua  ;  it  receives,  on  the  sides  of  this  face,  the  attach- 
ment of  the  broad  ligaments  ;  its  lateral  and  inferior  faces  are  related  to  the 
intestinal  convolutions.  (Inferiorhj,  it  is  in  relation  with  the  bladder.)  Its 
anterior  extremity  (or  fundus)  is  continuous,  without  inten'uption,  with  each  of 
the  cornua  ;  thQ  posterior  extremity  is  separated  from  the  vagina  by  a  constriction, 
named  the  neck  {cervix)  of  the  uterus. 

The  cornua,  lying  among  the  different  portions  of  intestine  which  occupy  the 
same  region,  offer  :  a  free  and  convex  inferior  curvature ;  a  superior  curvature,  to 
which  the  suspensory  ligaments  are  attached  ;  a  posterior  extremity,  or  base,  fixed 
to  the  body  of  the  organ  ;  and  an  anterior  extremity  or  summit — a  rounded  blind 
pouch  looking  upwards,  and  showing  the  entrance  of  the  Fallopian  tube, 

3Ieans  of  attachment. — Floating  in  the  abdominal  cavity,  like  the  intestines, 
the  uterus  is  also,  like  them,  attached  by  bands  which  suspend  it  to  the  sub- 
lumbar  region,  and  which  for  this  reason  have  been  named  the  suspensory  or 
broad  ligaments  of  the  uterus. 

These  bands  are  two  in  number,  are  irregularly  triangular  in  shape,  and  are 
more  developed  before  than  behind.  Close  to  each  other  posteriorly,  and 
separating  in  front  like  the  branches  of  the  letter  V,  they  leave  the  sublumbar 
surface  and  descend  towards  the  uterus,  to  be  attached  by  their  inferior  border 
to  the  sides  of  the  upper  face  of  the  body  and  the  small  curvature  of  the  cornua. 
Their  anterior  body  is  free  ;  they  sustain  the  Fallopian  tubes  and  ovaries,  th» 


THE  GENITAL   ORGANS  OF  TEE  FEMALE.  991 

former  being  placed  between  the  two  serous  layers  of  the  ligament,  and  the  latter — 
also  within  this  ligament — receives  a  band  detached  from  the  principal  layer, 
forming  with  it,  beneath  the  ovary,  a  kind  of  small  cupola. 


Fig.  535. 


15  19 

GENERATIVE   ORGANS   OF   THE   MARE,    ISOLATED   AND   PARTLY  OPENED. 

1,  1,  Ovaries;  2,  2,  Fallopian  tubes;  3,  pavilion  of  the  tube  (external  face);  4,  ditto  (inner  face, 
showing  the  opening  in  the  middle);  5,  ligament  of  the  ovary;  6,  intact  cornu  of  the  uterus-  7 
a  cornu  thrown  open;  8,  body  of  the  uterus  (upper  face);  9,  broad  ligament;  10,  cervix,  with  its 
mucous  folds;  11,  cul-de-sac  of  the  vagina;  12,  mterior  of  the  vagina,  with  its  folds  of  mucous 
membrane;  13,  urinary  meatus,  and  its  valve,  14;  15,  mucous  fold,  a  vestige  of  the  hymen;  16, 
interior  of  the  vulva;  17,  clitoris;  18,  18,  labia  of  the  vulva;  19,  inferior  commissure  of  the 
vulva. 


There  is  also  another  little  naiTow  long  band  outside  the  broad  ligament,  and 
which  can  be  traced  as  far  as  the  upper  inguinal  ring.    Anteriorly,  it  has  a  small 


992  GENERATIVE  APPARATUS. 

enlarged  appendix  ;  between  the  two  layers  forming  this  fold  is  found  a  thin 
muscle,  altogether  like  the  male  cremaster  before  the  descent  of  the  testicle  into 
the  scrotum.  This  may  be  looked  upon  as  the  analogue  of  the  round  ligament  of 
Woman. 

The  uterus  is  also  fixed  in  its  situation  by  its  continuity  with  the  vagina. 

Interior. — The  inner  surface  of  this  organ  shows  mucous  folds,  which  exist 
even  in  the  foetus  ;  they  are  arranged  in  a  longitudinal  series,  and  are  not 
effacable  by  distension  ;  though  they  disappear  during  gestation,  consequent  on 
the  enlargement  that  takes  place  in  the  uterine  cavity. 

This  cavity  has  three  compartments  :  the  cariti/  of  the  body,  and  those  of  the 
cornua.  The  latter  are  pierced,  at  their  extremity,  by  the  uterine  orifice  of  the 
Fallopian  tube ;  while  the  former  communicates  with  the  vagina  by  a  narrow 
canal  that  passes  through  the  posterior  constriction  of  the  uterus  (cervix), 
and  which  is,  in  Human  anatomy,  named  the  cavity  of  the  cervix  (os  uteri,  os 
externum,  os  triccB).  In  all  the  domesticated  animals,  except  the  Rabbit,  this 
canal  is  prolonged  to  the  bottom  of  the  vagina,  in  something  the  same  fashion 
as  a  tap  is  into  the  interior  of  a  barrel ;  and  in  this  way  it  always  forms  a  very 
marked  projection  in  the  vaginal  cavity.  Around  this  projection,  the  utero- 
vaginal mucous  membrane  is  raised  in  transverse  folds  disposed  in  a  circular 
manner,  which  give  it  the  appearance  of  a  radiated  flower ;  in  Veterinary 
anatomy,  this  projection  of  the  cervix  is  consequently  named  the  "expanded 
flower  "—fleur  epanouie ;  it  is  the  tench's  nose  of  the  Human  being. 

Structure. — The  walls  of  the  uterus  are  composed  of  three  membranes— 
an  external,  serous ;  a  middle,  muscular ;  and  an  internal,  mucous ;  with  vessels 
and  nerves. 

The  serous  tunic  envelops  all  the  organ ;  it  is  an  expansion  of  the  broad 
ligaments,  which  are  prolonged  backwards  on  the  posterior  extremity  of  the 
vagina,  and  are  afterwards  doubled  in  a  circular  fashion  around  that  canal,  to 
pass  over  either  the  rectum,  the  bladder,  or  the  lateral  walls  of  the  pelvis. 
Between  the  two  cornua  this  membrane  forms  a  particular  fraenum,  which  is  only 
slightly  developed  in  Solipeds. 

The  muscular  layer  comprises  longitudinal  (superficial),  and  circular  (deep) 
fibres,  analogous  to  those  of  the  small  intestine.  Near  the  insertion  of  the  broad 
ligaments,  they  give  off  a  series  of  fasciculi  which  are  prolonged  between  the 
two  layers  of  these  ligaments.  These  are  not  the  only  smooth  muscular  fibres 
met  with  in  the  ligaments,  however ;  for  Rouget  has  found  others  throughout 
their  whole  extent,  but  particularly  in  the  vicinity  of  the  ovaries.^  (Around  the 
cervix  uteri,  the  circular  fibres  are  most  dense  and  numerous.) 

In  the  pregnant  animal,  the  number  of  fibres  composing  this  layer  is  much 
more  considerable  than  in  ordinary  circumstances  ;  this  increase  has  for  its  object 
to  permit  the  dilatation  of  the  uterus,  without  allowing  its  parietes  to  become 
too  attenuated  ;  they  do  become  more  or  less  thin,  notwithstanding,  according 
to  the  species.  It  has  also  been  remarked  that,  during  pregnancy,  the  muscular 
fibres  present  a  manifest  striation.  (The  elements  of  these  fibres  are  short  fusi- 
form cells  with  long  oval  nuclei,  mixed  with  a  large  quantity  of  embryonic, 
nucleated  connective  tissue.) 

The  mucous  membrane  is  very  rich  in  cellular  elements,  and  is  thin,  delicate, 
and  raised  into  folds.     It  is  covered  by  ciliated  epithelium,  which  becomes 

>  Unstriped  contractile  fibres  are  also  found,  iu  the  male,  along  tlie  spermatic  cord,  beneath 
the  visceral  layer  of  the  tunica  vasinalis. 


THE  GENITAL   ORGANS  OF  TEE  FEMALE.  993 

cylindrical  in  the  os  uteri,  and  pavemental  around  the  cervix  ;  here  also  are 
found  calyciform  cells — a  kind  of  unicellular  glands  which  secrete  the  thick  mucus 
found  in  this  part.  (The  cilia  vibrate  towards  the  fundus  of  the  organ.  The 
membrane  is  closely  connected  with  the  muscular  tunic,  and  is  composed  of 
embryonic,  nucleated,  connective  tissue,  without  elastic  fibres.)  The  uterine 
mucous  membrane  is  destitute  of  papillae  except  at  the  cervix  (where  there  are 
many  highly  vascular  papillas)  ;  but  it  lodges  numerous  simple  or  ramified 
glands,  which  are  straight  or  slightly  flexuous  at  their  extremities.  At  the 
cervix,  these  glands  enlarge  at  the  bottom,  and  assume  something  of  the 
appearance  of  acinous  glands. 

(These  mucous  glands  are  designated  simple  and  cylindrical.  The  first  are 
most  numerous  towards  the  cervix  ;  some,  here  and  there,  with  their  orifices 
closed,  are  enlarged,  and  form  small  vesicular  tumours— the  ovida,  cysts,  or  glands 
of  Nahothi ;  they  secrete  the  peculiar  transparent  mucus  found  here.  The 
cylindrical,  uterine,  or  utricular  glands  are  closely  clustered  together,  sometimes 
bifurcated,  often  twisted  in  a  spiral  fashion,  and  terminating  in  a  cul-de-sac  in 
the  substance  of  the  membrane.  In  structure  they  resemble  other  mucous 
glands,  consisting  of  a  membrana  propria,  an  epithelium  of  spheroidal  cells  at 
the  bottom  of  the  tube,  and  of  columnar  cells  in  its  duct.  During  gestation 
they  are  much  enlarged,  and  receive  the  cotyledonal  processes  of  the  placenta. 
At  the  period  of  oestrum,  the  glandular  secretion  of  the  uterus  is  more  active 
than  at  other  times.) 

Vessels — Nerves. — The  blood  is  brought  to  the  uterus  by  the  uterine  and  utero- 
ovarian  arteries,  and  is  conveyed  from  it  by  veins  corresponding  to  the  latter. 
In  animals  which  have  been  pregnant  several  times,  the  vessels  are  remarkable 
for  their  enormous  volume,  their  tortuousness,  and  the  adhesion  of  the  veins 
to  the  neighbouring  tissues.  (The  arteries  freely  anastomose  ;  they  ramify 
through  the  muscular  and  mucous  tunics,  constituting  coarse  and  fine  networks, 
which  ultimately  end  in  the  veins.  These  are  very  large,  and  have  no  valves ; 
the  plexuses  they  form  are  considerable.) 

The  lymphatics  that  proceed  from  the  uterus  are  as  remarkable  for  their 
number  as  their  size  ;  they  pass  to  the  sublumbar  region. 

The  nerves  supplying  the  organ  come  from  the  small  mesenteric  and  pelvic 
plexuses.  (In  the  uterus  there  are  several  important  nerve-gangha  ;  and  during 
gestation  it  has  been  ascertained  that  the  nerves,  like  the  vessels,  enlarge,  and 
after  parturition  return  to  their  former  size.) 

Development. — Narrow  in  the  foetus,  and  in  the  adult  which  has  not  been 
impregnated,  the  uterus  increases  in  size  in  animals  which  have  had  young 
several  times. 

Functions. — The  uterus  is  the  sac  in  which  the  embryo  is  developed.  The 
ovum  grafts  itself  upon  the  mucous  membrane  of  the  organ  by  its  placental 
apparatus,  in  order  to  draw  indirectly,  from  the  maternal  blood,  the  materials 
for  its  development.  This  function  of  the  uterus  gives  rise  to  most  interesting 
anatomical  and  physiological  considerations,  which  will  be  referred  to  when 
giving  the  history  of  the  ovum. 

4.  The  Vagina  (Figs.  535,  536). 

The  vagina  is  a  membranous  canal  with  thin  walls.;  it  succeeds  the  uterus, 
and  terminates  posteriorly  by  an  external  opening — the  vulva. 

Situation  and  Relations. — Situated  in  the  pelvic  cavity,  which  it  passes 


994  GENERATIVE  APPARATUS. 

across  horizontally,  the  vagina  is  in  relation  with  the  rectum  above,  below  with 
the  bladder,  and  laterally  with  the  sides  of  the  pelvis  and  the  ureters.  Con- 
nective and  adipose  tissues  suiTOund  it  posteriorly. 

Internal  conformation.— The  inner  surface  of  the  vagina  is  always  lubricated 
by  an  abundance  of  mucus,  and  is  ridged  by  longitudinal  folds  {columnce  rugosce). 


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In  front,  at  the  bottom  of  the  canal,  is  observed  the  projection  formed  by  the 
cervix  uteri ;  posteriorly,  this  surface  is  continuous  with  that  of  the  vulva. 

Structure. — The  vagina  is  formed  of  two  tunics — an  inner,  mucous,  and 
nn  external,  muscular.  The  mucous  membrane  (pale  red  in  colour)  is  continuous 
with  that  Uning  the  vulva  and  the  uterus  (and  bladder)  ;  it  is  provided  with 


TEE  GENITAL   ORGANS   OF  •THE  FEMALE.  995 

papillae,  and  is  lined  by  stratified  squamous  epithelium.  It  contains  some  closed 
follicles.  (It  consists  of  connective  and  elastic  tissues,  to  which  its  extensibility 
and  firmness  are  due.) 

The  muscular  coat  is  rose-coloured,  and  traversed  by  a  large  number  of 
vessels  ;  it  is  surrounded,  for  the  greater  part  of  its  extent,  by  an  abundance 
of  connective  tissue,  which  unites  it  to  the  organs  contained  in  the  pelvic  cavity  ; 
in  front,  however,  it  is  enveloped  by  the  peritoneum,  which  surrounds  the  vagina 
before  passing  to  the  uterus.  (This  connective  tissue  is  sometimes  designated 
the  third  or  fibrous  tunic  of  the  vagina.  The  muscular  fibres  are  unstriped,  and 
arranged  in  circular  and  longitudinal  series  ;  towards  the  posterior  portion  of 
the  canal  they  are  redder  than  in  front.) 

Vessels  and  nerves. — The  vagina  is  supplied  with  blood  by  the  internal  ptcdic 
artery  ;  this  fluid  is  carried  from  it  by  numerous  veins,  which  are  disposed  in  a 
plexus  around  the  canal,  and  enter  the  satellite  of  the  artery.  The  nerves  come 
from  the  pelvic  plexus.  (The  lynrphatics  accompany  the  veins,  and  pass  to  the 
pelvic  glands.) 

Function. — The  vagina  receives  the  male  organ  during  copulation,  and 
through  it  the  foetus  passes  during  parturition. 

5.  The  Vulva  (Fig.  535). 

The  external  orifice  of  the  vagina,  the  mdva  is  situated  in  the  perinseal  region, 
immediately  below  the  anus.  We  will  consider  in  succession  its  external  opening^ 
its  cavity.,  and  its  structure. 

External  Opening. — This  is  a  vertical  elongated  slit,  presenting  two  lips 
and  tuw  commissures.  The  lips  (labia  vulvae)  are  covered  externally  by  a  fine, 
smooth,  unctuous,  and  (almost)  hairless  skin,  rich  in  colouring  pigment,  and 
lined  internally  by  mucous  membrane  ;  on  their  free  margin,  the  limits  of  these 
two  membranes  are  well  marked.  The  superior  commissure  is  very  acute,  and 
almost  meets  the  anus,  from  which  it  is  nevertheless  separated  by  a  narrow  space 
— the  perinceum.  The  inferior  commissure  is  obtuse  and  rounded  ;  it  lodges  the 
clitoris. 

Cavity  op  the  Vulva. — By  all  Veterinary  authorities,  this  cavity  is  de- 
scribed as  belonging  to  the  vagina,  to  which  it  forms  the  entrance  ;  but  consider- 
ing the  analogies  that  exist  between  the  genital  parts  of  Woman  and  those  of 
animals,  this  cavity  must  be  distinguished  from  that  of  the  vagina.  It  offers 
for  study  the  hymen,  which  separates  the  two  cavities,  the  meatus  urinarius  and 
its  valve,  and  the  clitoris. 

The  Clitoris — Exactly  like  the  corpus  cavernosum  of  the  male — which  it 
represents  in  miniature — and  from  2  to  3  inches  in  length,  the  clitoris  commences 
by  two  crura  fixed  to  the  ischiatic  arch,  and  covered  by  a  rudimentary  erector  penis 
muscle.  After  being  attached  to  the  symphysis  by  means  of  a  suspensory  liga- 
ment analogous  to  that  of  the  male,  it  passes  backwards  and  protrudes  into  the 
vulvular  cavity,  towards  the  inferior  commissure.  Its  free  extremity,  lodged  in 
that  cavity,  is  enveloped  by  a  mucous  cap — the  prepuce  of  the  clitoris  {prceputium 
clitoridis),  which  is  folded  in  various  directions,  and  excavated  about  the  centre 
of  the  tubercle  by  a  small  follicular  cavity  that  represents  the  extremity  of  the 
male  penis.  The  organization  of  the  clitoris  resembles  in  every  particular  that 
of  the  corpus  cavernosum  of  the  penis — a  fibrous  framework,  erectile  tissue,  and 
•cavernous  vessels.  It  is  the  contact  of  the  penis  with  this  organ  during  copula- 
tion, that  chiefly  occasions  the  venereal  excitation. 


996  Gh.,t.tiATIVE  APPARATUS. 

The  Meatus  Urinarius  and  its  Valve.— The  urethral  canal  in  the 
female  is  very  short.  It  passes  immediately  beneath  the  anterior  sphincter 
muscle  of  the  vulva,  and  after  a  brief  course  in  the  texture  of  the  floor  of  the 
vagina,  it  opens  into  the  vulvar  cavity  by  an  orifice  covered  by  a  large  mucous 
valve  :  this  is  the  meatus  urinarius  and  its  valve.  The  urinary  opening,  placed 
at  the  bottom  of  the  cavity,  at  frc- :  S^  to  5  inches  from  the  external  opening, 
is  wider  than  the  male  urethn",,  and  will  admit  sounds  of  somewhat  large  size, 
for  the  catheterism  of  the  bladaer.  The  valve  has  its  free  border  inclining 
backwards,  to  direct  the  flow  of  r.riEe  towards  the  exterior,  and  prevent  its  reflux 
into  the  vagina. 

(The  female  urethra  is  composed  of  two  tunics  :  a  mucoi/s,  continuous  with 
that  of  the  bladder  and  vagina  ;  and  a  muscular  coat,  also  a  continuation  of 
that  belonging  to  these  organs,  and  chiefly  made  up  of  circular  fibres ;  some 
flat  fasciculi  attach  it  to  the  periosteum  of  the  ischial  bones.  The  urethra  is 
not  suiTounded  by  a  corpus  spongiosum,  as  in  the  male.) 

The  Hymen. — This  membrane,  when  it  exists,  distinctly  separates  the 
vulvar  from  the  vaginal  cavity.  It  is  rarely  present,  however ;  though  we 
have  observed  it  several  times  in  the  adult  Mare.^  It  forms  a  circular  partition, 
fixed  by  its  margin  to  the  vulvo-vaginal  walls,  as  w^ll  as  to  the  valve  of  the 
meatus  urinarius,  and  is  perforated  by  one  or  more  openings  which  establish  a 
communication  between  the  vulva  and  vagina.  On  many  occasions  we  have 
found,  in  old  brood-mares,  pediculated  appendages— the  remains  of  this  septum. 
It  is  usually  represented  by  a  transverse  fold  of  mucous  membrane,  notched  on 
its  free  border,  which  lies  above  the  meatus  urinarius. 

Structure  of  the  Vulva. — The  vulva  offers  for  study  in  its  structure  : 
1.  The  mucous  membrane  lining  its  interior.  2.  An  erectile  body  lying  on  that 
membrane,  and  named  the  vaginal  bulb.  3.  Tivo  constrictor  muscles — anterior 
and  posterior.    4.  Two  muscular  ligaments.     5.  The  external  skin. 

1.  Mucous  membrane. — Continuous  with  that  of  the  vagina  and  bladder,  this 
membrane  has  a  rosy  colour,  which  may  become  a  bright  red  at  the  period  of 
oestrum.  It  often  shows,  near  the  free  border  of  the  labia — and  especially  on  the 
mucous  cap  of  the  clitoris — black  pigment  patches,  which  give  it  a  speckled 
appearance.  It  has  in  its  substance  a  great  quantity  of  mucous  follicles  and 
sebaceous  glands.  The  latter  exist  near  the  free  border,  particularly  about  the 
clitoris,  and  especially  in  the  space  between  that  erectile  body  and  the  inferior 
commissure  of  the  vulva,  where  they  meet  in  several  small  sinuses.  (These 
glands  secrete  an  unctuous  matter  possessing  a  special  odour ;  they  are  most 
active  during  oestrum.) 

Where  the  mucous  membrane  is  furnished  with  papillae,  it  is  covered  by  a 
stratified  pavement  epithelium. 

2.  Vaginal  (or  vestibular)  bulb. — This  is  an  organ  entirely  formed  of  erectile 
tissue  with  wide  areolae  ;  it  is  divided  into  two  branches  {bulbi  vestibuli),  which 
arise  from  the  vicinity  of  the  crura  of  the  clitoris  and  pass  on  the  sides  of  the 
vulva,  where  they  terminate  in  a  round  lobe.  Covered  by  the  posterior  con- 
strictor of  the  vulva,  the  vestibular  bulb  conununicates,  inferiorly,  with  the 
veins  of  the  corpus  cavernosum.  The  influx  of  blood  into  the  cells  of  its  tissue 
contracts  the  vulvar  cavity,  and  concurs  to  render  the  coaptation  of  the  copu- 
latory  organs  more  perfect  during  coition. 

•  Goubaux  gives  several  instances,  in  an  article  on  "  Purturitiou  in  the  Domestic  Animals,* 
published  in  the  Bectieil  de  M^d.  V^te'rinaire  for  1873. 


THE  GENITAL   ORGANS  OF  THE  FEMALE.  991 

3.  Muscles  of  the  vulva. — Imperfectly  described  and  determined  in  books  on 
Veterinary  Anatomy,  these  belong  to  the  category  of  voluntary  muscles.  We 
recognize  two,  which  will  be  described  as  the  posterior  and  anterior  constrictors. 

Posterior  Constrictor  of  the  Vulva. — AnalogouL  to  the  constrictor 
vagince  of  Woman,  this  muscle — included  in  the  labia  of  the  vulva — forms  a  veri- 
table sphincter.  Above,  its  fibres  are  mixed  with  those  of  the  sphincter  ani,  and 
are  attached  to  the  sacrum  through  the  medium  of  the  suspensory  ligaments. 
Inferiorly,  the  most  anterior  are  fixed  to  the  base  of  the  clitoris  ;  the  middle 
are  prolonged  between  the  thighs,  and  are  inserted  into  the  inner  surface  of 
the  skin. 

Inwardly,  it  is  in  relation  with  the  vestibular  bulb  and  the  mucous  membrane 
of  the  vulva.  Its  external  face  is  separated  from  the  skin  of  the  labia  by  a  very 
vascular  cellulo-fibrous  tissue  capable  of  tonic  contraction,  and  in  the  midst 
of  which  are  always  found  isolated  red  fasciculi — dependencies  of  the  principal 
muscle. 

This  muscle,  in  contracting  during  copulation,  constricts  the  aperture  of  the 
vagina  and  compresses  the  penis  ;  and  as,  in  consequence  of  its  attachment  to 
the  clitoris,  it  cannot  act  without  raising  that  erectile  body,  it  appHes  this  to 
the  male  organ  and  causes  a  greater  degree  of  excitement.  With  animals  in 
<Estrum,  the  movements  of  the  clitoris  are  frequently  observed  to  propel  that 
organ  outwards,  especially  after  micturition  ;  in  this  case,  the  fibres  of  the 
constrictor  attached  to  the  clitoris  erect  it  by  its  base,  while  those  which  are 
fixed  into  the  skin  between  the  thighs  depress  the  inferior  commissure  of  the 
vulva.  This  double  action  necessarily  exposes  the  erectile  tubercle  lodged  in 
that  commissure. 

Anterior  Constrictor  of  the  Vulva. — This  muscle  is  formed  of  arciform 
fibres  which  envelop — below  and  laterally — the  vaginal  walls  at  the  entrance  of 
the  canal ;  its  extremities  are  continued,  by  means  of  aponeurotic  fascia,  to  the 
sides  of  the  rectum,  where  they  are  lost ;  some  even  pass  tc  the  inferior  surface 
of  the  sacrum.     By  its  posterior  border,  this  muscle  is  mixed  with  the  preceding. 

4.  Muscular  ligaments  of  the  vulva. — Traces  of  the  suspensory  ligaments  of 
the  male  penis,  these  are  disposed  in  the  same  manner  at  their  origin.  After 
becoming  united  beneath  the  rectum,  they  descend  in  several  fasciculi  into  the 
labia  of  the  vulva,  and  disappear  among  the  fibres  of  the  posterior  constrictor. 

5.  External  skin. — This  is  fine  and  black  (or  hght-coloured),  destitute  of 
hair,  smooth  and  unctuous,  and  adheres  closely  to  the  subjacent  tissues. 

6.  The  Mamm^. 

The  mammce  are  glandular  organs  ;  they  secrete  the  fluid  that  should  nourish 
the  young  animal  during  the  early  months  of  its  life.  They  are  rudimentary  in 
youth,  and  become  developed  with  the  advent  of  puberty,  assuming  their  greatest 
development  towards  the  end  of  gestation  ;  they  are  most  active  after  parturi- 
tion, and  cease  their  function,  as  well  as  diminish  in  volume,  when  the  period  of 
lactation  has  terminated. 

Situation. — These  glands  are  two  in  number,  placed  beside  each  other  in  the 
inguinal  region,  where  they  occupy  the  situation  of  the  scrotum  in  the  male. 

Form. — They  are  two  hemispherical  masses,  separated  from  each  other  by  a 
shallow  furrow,  and  showing  in  their  centre  a  prolongation  called  the  teat,  nipple, 
or  mammilla,  which  is  pierced  at  its  free  extremity  by  several  orifices  for  the 


998  GENERATIVE   APPARATUS. 

escape  of  the  milk  ;  it  is  by  this  prolongation  that  the  young  animal  effects 
suction. 

The  two  glands  are  fixed  in  their  position  by  the  skin  which  covers  them, 
and  which  is  thin,  black,  covered  with  a  line  down,  and  altogether  destitute  of 
hair  in  the  vicinity  of,  or  on,  the  teat,  where  the  cutaneous  surface  is  smooth, 
greasy,  and  supple.  They  are  also  attached  to  the  tunica  abdominalis  by  several 
wide,  but  short,  elastic  bands,  which  resemble  the  ligaments  of  the  prepuce  in 
the  male. 

Structure. — Structurally,  the  mammary  glands  offer  for  study  :  1.  A  yellow 
(elastic)  fibrous  envelope.  2.  Glandular  tissue.  3.  The  (jalactophorous  (or  lactiferous) 
reservoirs  or  sinuses.     4.  The  excretory  canals,  or  mammary  (or  milk)  ducts. 

The  elastic  envelope,  placed  in  the  middle  line,  beside  its  fellow  of  the  opposite 
side,  is  mixed  with  the  suspensory  bands  that  descend  from  the  abdominal  tunic, 
and  sends  into  the  substance  of  the  gland  a  number  of  septa,  which  are  inter- 
posed between  the  principal  lobules. 

The  glandular  tissue  is  a  compound  of  gland-vesicles  or  acini,  clustered  in 
groups  around  the  lactiferous  ducts.  (The  gland-vesicles  are  made  up  of  an 
amorphous  membrane — membrana  propria — lined  with  spheroidal  nucleated  cells. 

Fig.  537.  Fig.  538. 


GLAND-VESICLES,     WITH     THEIR    EXCRETORY  ULTIMATE    FOLLICLES,    OR    GLAND-VESICLES, 

DUCTS    TERMINATING     IN    A    DUCTUS    LAC-  WITH    THEIR    EPITHELIUM    OR    SECRETING 

TIFEROUS:  FROM  A  MERCURIAL  INJECTION  CELLS,  a,  a,  AND   NUCLEI,  6,  6. 
(magnified   FOUR   TIMES). 

They  are  -^  of  an  inch  in  diameter.)  The  lactiferous  ducts  commence  by 
blind  extremities,  and  run  into  each  other  to  constitute  a  certain  number  of 
principal  canals  ;  these  open  into  the  galactophorous  sinuses  (each  a  saccidus  vel 
sinus  lactiferus).  The  glandular  culs-de-sac  are  lined  with  a  polyhedral  epithe- 
lium when  the  gland  is  inactive  ;  but  during  lactation  the  alveoli  enlarge,  their 
walls  become  thickened  by  a  regular  epithelial  layer,  and  their  cavities  filled  with 
spherical  cells  which  are  infiltrated  by  a  great  quantity  of  fat. 

Placed  at  the  base  of  the  teat,  the  galactophorous  sinuses  or  reservoirs  are 
generally  two  in  number,  but  sometimes  there  are  three,  and  even  four.  They 
nearly  always  communicate  with  each  other,  and  are  continued  into  the  mam- 
milla by  an  equal  number  of  independent  excretory  canals — the  definitive  dmtSy 
the  orifices  of  which  are  very  small,  and  are  seen  beside  each  other  at  the  free 
extremity  of  the  teat.  A  fine  mucous  membrane  lines  the  inner  face  of  this 
excretory  apparatus  ;  it  is  doubled  in  the  teat  by  a  thick  layer  of  tissue,  which, 
again,  is  covered  by  the  skin  that  adheres  closely  to  it.  (Between  the  external 
and  internal  tunic  of  the  teats  are  found  numerous  fasciculi  of  unstriped 
muscular  fibres,  arranged  in  a  circular  and  longitudinal  manner  around  these 
ducts.) 

Connective  and  adipose  tissue,  vessels,  and  nerves  complete  this  organization. 
The  arteries  are  from  the  external  pudic  trunk  ;  the  veins  are  very  numerous. 


TEE  GENITAL   ORGANS  OF  THE  FEMALE.  999 

and  pass  to  the  abdominal  subcutaneous  vein  ;  capillaries  form  a  rich  network 
around  the  alveoli.  The  lymphatics  are  very  developed.  (The  nerves  are 
derived  from  the  first  lumbar  pair.) 

Functions. — The  mammte  secrete  the  milk ;  they  undergo  remarkable 
modifications  at  puberty  and  at  the  end  of  each  gestation — modifications  which 
are  related  not  only  to  their  volume  and  secretion,  but  also  to  their  minute 
structure.  After  gestation,  the  gland-vesicles  shrink — become,  as  it  were, 
atrophied,  and  have  only  a  polygonal  epithelium.  At  the  termination  of  gesta- 
tion, they  are  enlarged,  new  vesicles  are  developed,  and  the  epithelium  changes 
its  character — filling  the  gland  cavities, 

assuming  a  spherical  shape,  and  becoming  Fig.  539. 

charged  with  fat-granules.   The  period  of  ..  fvo°o^°''°9<' 

lactation  being   completed,  the  mamms  - '-  -  ^    -  ^      ^ 

assume  their  former  character.  (In  Mares 
which  have  not  been  bred  from,  the 
mammte  are  hard  and  small,  the  teats  only 

slightly  prominent,   and    the    glandular  _oo„^-„  6„    ^ 

tissue  scanty.    In  old  brood-mares,  on  the     0°°  o,  ®g^  Opo°o  0°^°  o  o  p»  o°Oo*o  °?°°.  © 


contrary,  they  are  flaccid  and  pendent,  and  ^  ^5  ^o  o  ^j^  ^  0-0  ^ 
the  teats  somewhat  lengthened.  The  milk  "^%  0°  °|o  ^  o  ®0°^. 
secreted  by  the  mammary  glands  is  a  white       ''g'>°°so°  °So  00°^" 


fluid,  possessing  a  sweet  taste,  and  com-    .     ''W0'$^°o'^ ^  ■ 

posed  of  an  albuminous  water  containing  ^^^''P°!6Bp° 

caseine  in  solution,  milk  sugar,  salts,  and 

fatty    matter    in    globules — the    butter. 

TTsnallv  a  small  nnantitv  i<5  '^pfrptprl   snmp      microscopical  appearance  of  milk,  with 

usual  y  a  small  quantity  is  secreted  some        ^^^  intermixture  of  colostric  corpus- 

days  before  parturition  ;    that  which  is        cles  at  a,  a,  and  elsewhere. 

yielded  for  a  short  time  after  that  period 

— the  colostrum — is  rich  in  white  corpuscles,  and  has  purgative  properties.     The 

colostrum  is  of  a  rich  yellow  colour,  less  fluid  than  the  milk  of  a  later  period, 

of  a  higher  specific  gravity,  sUghtly  acid,  and  containing  large  oil-globules,  a  few 

irregular  flakes — probably  epithelium-scales — a  little  granular  curd-like  matter, 

and  a  small  number  of  granular  corpuscles.) 

Differential  Characters  in  the  Female  Genital  Organs  of  the  other  Animals. 

Certain  organs  offer  some  differences  worthy  of  notice,  while  others  are  formed  as  in 
Solipeds. 

Ruminants. — Ovaries. — In  the  Cow,  the  ovaries  are  relatively  much  smaller  than  in  the 
Mare,  but  tlieir  form  and  structure  are  identical.  (The  Graafian  vesicles  are  visible  through 
the  tunica  albuginea.) 

Uterus. — The  uterus  of  the  Co"w,  compared  with  that  of  the  Mare,  offers  but  few  differ- 
ences with  regard  to  its  general  disposition  in  the  pelvic  and  abdominal  cavities,  except  that 
it  is  not  so  advanced  in  the  latter.  Supposing  the  uterus  to  be  perfectly  horizontal,  a  trans- 
verse line  drawn  through  the  plane  of  the  abdomen,  before  the  external  angle  of  the  ilium,  is 
exceeded  by  the  extremity  of  the  cornua  from  about  1 J  to  2  inches ;  so  that  if  the  animal  were 
on  its  back,  the  uterus  would  only  be  prolonged  to  the  fourth  or  fifth  lumbar  vertebra. 

With  regard  to  form,  the  uterus  of  the  Cow  presents  a  very  remarkable  disposition,  which 
it  is  necessary  to  note.  The  concave  curvature  of  the  cornua  looks  downwards,  while  in  the 
Mare  it  looks  upwards ;  though  in  both  the  sublumbar  ligaments  are  attached  to  this  con- 
cavity. Therefore  it  is  that  in  the  Cow — if  we  consider  the  uterus  as  freely  suspended  in  the 
abdomen — the  extremity  of  tht)  cornua  is  twisted  outwards  and  upwards,  while  the  base, 
although  drawn  in  the  same  direction  by  these  ligaments,  maintains  its  direction,  because  it 
is  in  a  manner  fixed  by  the  body  of  the  uterus.     The  latter  receives,  like  the  cornua,  the 


1000  GENERATIVE  APPARATUS. 

insertion  of  the  broad  ligaments  on  its  lower  plane,  so  that  it  overlaps  them,  while  the  utema 
of  the  Mare  projects  below  them.  Otherwise,  these  lijjaments  are  very  ample,  especially  at 
their  anterior  border;  they  are  wide  apart  in  front,  towards  their  lumt«,r  attachment,  wliich 
is  prolonged  even  on  the  parietes  of  the  flank.  The  ligaments  may  be  altogether  compared  to 
a  triangular  cravat,  one  angle  of  which  is  attached  to  the  bottom  of  the  pelvic  cavity,  and  the 
other  two  to  the  tuberosities  of  the  ilium.  On  this  cravat  lies  the  body  and  part  of  the  cornua 
of  the  uterus. 

The  uterine  cornua  are  thin  and  tapering  at  their  anterior  extremity.  The  body  is  short 
and  narrow. 

The  interior  of  the  utenis  of  the  Cow  is  less  ample  tlian  that  of  the  Mare.  Its  surface  is 
studded  with  rounded  tubercles,  known  as  cotyledons,  which  will  be  studied  iiereafter.  It  is 
only  necessary  to  say  here  that  they  are  numerous  ia  the  cornua,  but  small  and  few  in  the 
body  of  the  organ. 

The  cervix  uteri,  about  from  2f  to  3 J  inches  long,  is  narrow  and  irregular.  The  "ex- 
panded flower,"  more  finely  plicateil  than  in  the  Mare,  is  almost  cartilaginous.  Three  other 
plicated  rings,  eafh  smaller  than  the  other,  are  e'chelonned  in  the  cavity  of  the  cervix,  from 
the  external  orifice  to  the  body  (corresponding  to  the  pHcae  palmatx,  or  arbor  vitm  uterina,  of 
Woman.) 

In  structure,  the  muscular  layer  is  generally  thicker  than  in  Solipeds. 

In  the  Sheep  and  Goat,  the  arrangement  is  the  same  as  in  the  Cow,  except  that  the 
cotyledons  are  hollowed  like  a  cup  in  their  centre,  and  deserve  their  name.  (The  cornua  are 
longer  and  more  pendent  than  in  the  Cow.) 

In  the  Camel,  the  cervix  uteri  is  very  long,  and  is  encircled  by  six  corona  of  superposed 
mucous  folds,  hard  and  rigid  on  their  surface.  The  cavity  in  the  body  is  divided  in  two  for 
the  greater  part  of  its  extent,  by  a  septum  formed  by  the  junction  of  the  two  cornua. 

Vagina. — In  the  Cow,  the  sides  of  the  vagina  are  traversed,  for  a  certain  distance,  by  a 
mucous  canal  tliat  opens  into  the  vulvar  cavity,  beside  the  meatus  urinarius.  These  ducts, 
the  use  of  which  is  unknown,  are  designated  the  canals  of  Gxrtner.  They  are  not  present  in 
the  Sheep  or  Goat.  (In  Ruminants,  the  vagina  is  longer,  and  its  external  tunic  thicker, 
than  in  the  Mare.  Leyh  describes  the  canals  of  Gaertner  as  present  in  the  Mare,  though 
rarely.) 

Vulva. — This  has  thick  labia  in  the  Cow.  The  inferior  commissure  is  acute,  and  furnished 
with  a  tuft  of  hair.  (The  corpus  cavernosum  of  the  clitoris  is  longer,  thinner,  and  more 
flexuous,  and  the  glans  much  smaller,  than  in  the  Mare.)  The  meatus  urinarius  is  disposed 
as  in  the  Mare;  but  there  exists,  on  the  floor  of  the  urethra,  a  valve  the  free  border  of  which 
is  directed  backwards.  This  valve  surmounts  a  small  cul-de-sac,  which  it  is  necessary  to  avoid 
in  catheterism  of  the  bladder.  At  about  an  inch  from  the  entrance  to  the  vulva,  there  are 
found  in  the  texture  of  the  labia  the  vulvo-vaginal  glands  (glands  of  Bartholine).  Discovered 
by  Duverney,  described  by  Bartholine,  and  recently  by  Colin,  these  glands  (two  in  number) 
are  about  the  size  of  a  large  almond ;  their  wide  extremity  is  directed  upwards,  and  the 
narrow  end,  situated  in  the  vicinity  of  the  iscMo-clitoridis  muscle,  gives  origin  to  the  excretory 
canaliculi.  They  are  yellow  racemose  glands,  and  their  ducts  unite  to  form  a  kind  of  sinus, 
which  at  length  opens  in  the  vaginal  cavity,  about  4  inches  from  the  labia  of  the  vulva. 
(These  glandulse  vaginie  are  supposed  to  be  analogous  to  the  prostate  glands,  and  are  covered 
by  muscular  fasciculi.  They  are  composed  of  pyriform  glandular  vesicles,  lined  by  squamous 
epithelium,  and  surrounded  by  a  dense  nucleated  connective  tissue ;  the  excretory  ducts  are 
invested  by  columnar  epithelium,  and  surrounded  by  a  thin  layer  of  smooth  muscle-cells,  dis- 
posed longitudinally.     Their  secretion  is  a  clear,  yellowish,  viscid  mucus.) 

(In  the  Sheep  and  Goat,  the  labia  of  the  vulva  have  several  folds  externally,  and  the 
inferior  commissure  terminates  in  a  point.) 

Mammx. — In  the  Cow,  eacli  lateral  mammary  mass — although  enclosed  in  a  single  fibrous 
capsule — is  composed  of  two  distinct  glands,  each  having  its  teat;  so  that  this  animal  really 
has  four  mammx  and  four  teats.  There  are  also  frequently  found  behind  these,  two  rudi- 
mentary imperforate  (sometimes,  though  very  rarely,  perforate)  teats. 

In  the  centre  of  each  gland,  at  the  base  of  the  teat,  is  a  single  galactophorous  sinus,  the 
general  confluent  of  all  the  lactiftrous  ducts — a  wide  cavity  opening  at  the  extremity  of  the 
teat  by  a  definitive  excretory  canal.'  (The  mammse  of  the  Cow  occupy  the  same  region  as 
those  of  the  Mare,  and  the  teats  are  longer  and  thicker.) 

'  Sanson  has  seen,  at  Grignon,  a  Cow  with  seven  teats,  all  giving  milk.  He  has  also  seen 
*wo  teats  communicating  with  the  same  galactophorous  sinus,  and  he  believed  that  there  are 
•nly  two  mammae,  no  matter  how  many  teats  there  may  be.    Goubaux  is  of  opinion  that 


'  ^ 


THE  GENITAL   OliGANS  OF  THE  FEMALE.  1001 

In  the  Sheep  and  Goat,  there  are  only  two  mammae,  as  in  the  Mare  and  Ass,  though  they 
are  formed  as  in  the  Cow.     The  Goat  has  frequently  two  posterior  rudimentary  mammse. 

Pig. — The  ovary  of  the  Bow  has  a  lobulated  aspect,  like  the  ovary  of  Birds.  This  appear- 
ance is  due  to  the  ovisacs  which,  when  they  are  well  developed,  project  beyond  the  surface  of 
the  ovarium,  instead  of  remaining  encysted  in  its  stroma.  The  oviduct  is  less  flexuous,  but 
its  length  is  proportionately  greater  than  in  the  other  species.  The  body  of  the  uterus  is  sliort, 
but  the  cornua  are  very  long  and  folded,  and  float  amongst  the  intestinal  convolutions.  (Its  cervix 
does  not  project  into  the  vagina,  and  the  two  cavities — vagina  and  uterus — are  continued  into 
each  otlier  without  any  marked  limit  between  them.  The  mucous  membrane  is  very  loose, 
soft,  and  fine  to  the  touch,  and  its  surface  is  gathered  up  into  numerous  folds  of  various  forms. 
The  broad  ligaments  resemble  the  mesentery,  and  the  cornua  join  the  Fallopian  tubes  without 
any  very  perceptible  limit.) 

The  vagina  shows  Gsertner's  canals,  as  in  the  Cow.  (Its  mucous  membrane  has  numerous 
longitudinal  folds  anteriorly ;  and  in  front  a  multitude  of  fine  points,  wliich  are  the  excretory 
ducts  of  small  glands  analogous  to  the  prostates.  On  the  sides  of  the  meatus  urinarius  are  two 
small  fossettes  surrounded  by  a  ring.  There  is  no  vaginal  valve.)  Tlie  inferior  commissure 
of  the  vulva  is  more  acute  than  in  Ruminants.  The  mammae  are  ten  in  number,  disposed  in 
two  rows,  extending  from  the  inguinal  region  to  below  the  chest.  They  have  no  galacto- 
phorous  reservoirs,  as  in  the  larger  Ruminants — the  lactiferous  ducts  uniting  directly  into  a 
variable  number  of  definitive  canals  that  pass  through  the  teat,  to  pierce  its  extremity  by 
from  five  to  ten  orifices.  (There  are,  of  course,  five  or  six  glands  in  each  row,  each  with  its 
teat.) 

Carnivora.— In  the  Dog  and  Cat,  the  ovaries  and  uterus  are  disposed  as  in  the  Pig;  the 
ovaries  (are  situated  behind  the  kidneys,  and)  are  lodged  in  a  particular  fold  of  the  broad  liga- 
ments, which  forms  a  kind  of  cup.  There  are  no  Gaertner's  canals  in  the  vagina.  The  vulva 
of  the  Dog  is  triangular,  and  acute  at  its  inferior  commissure.  The  Cat  has  a  small  bone  in 
the  clitoris.  The  mammx  are  ten  in  number  in  the  Dog,  and  eight  in  the  Cat ;  they  are 
distinguished,  as  in  the  Pig,  into  inguinal,  abdominal,  and  pectoral.  (Each  teat  has  from  eight 
to  ten  orifices.  The  vagina  is  long,  and  wider  at  the  vulva  than  towards  the  uterus.  Beside 
the  smooth  muscular  fibres  of  its  external  coat,  it  has  wliite  fibres  which  give  it  greater  thick- 
ness and  resistance.  The  mucous  membrane  forms  longitudinal,  intersected  by  transverse, 
folds ;  the  valve  of  the  meatus  urinarius  scarcely  exists.  Tiie  cervix  of  the  uterus  projects 
into  the  vagina,  and  is  even  more  voluminous  than  the  body,  which  is  short ;  it  is  hard  to  the 
loucli.) 

Rodents.— Otz-aries. — In  the  Rabbit,  these  organs  are  about  from  J  to  i  inch  in  length, 
and  from  1|  to  2  inches  in  breadth ;  they  are  faintly  rose-tinted,  and  the  Graafian  vesicles 
and  corpora  lutea — extremely  numerous— are  scattered  over  the  entire  surface  of  the  glands. 

Fallopian  tube. — The  pavillion  of  the  tube  is  very  developed,  and  exceeds  the  ovary  in 
front ;  it  is  bent  downwards  and  backwards,  in  order  to  be  fixed  on  the  ovary. 

Uterus.— In  the  Rabbit,  the  uterus  is  double,  there  being  really  two  distinct  organs  lying 
beside  each  other  at  their  origin,  but  diverging  for  the  remainder  of  their  extent.  Their 
average  length  is  from  4  to  5  inches ;  each  is  cylindrical  and  slightly  flexuous,  and  opens  at 
the  bottom  of  the  vagina  by  a  small  "  expanded  flower."  The  broad  ligaments  are  fixed  in 
the  uterus  as  in  the  Cow,  and  the  uterus  is  drawn  outwards. 

Vagina. — This  is  flattened  above  and  below,  and  sustained  by  the  borders  of  its  inferior 
face ;  it  is  from  about  2  to  3  inches  long,  but  its  origin  is  not  well  defined,  as  the  meatus 
urinarius  is  more  or  less  crossed  by  Gaertner's  canal,  which  naturally  belongs  to  the  vagina. 
That  canal  lies  to  the  left  of  the  meatus,  but  it  soon  disappears  there,  to  reappear  in  the 
vicinity  of  the  left  uterine  canal. 

Vulva. — Rather  more  than  two  inches  long,  the  vulvar  cavity  is  almost  entirely  situated 
beyond  the  ischiatic  arch,  and  is  attached,  witir  the  rectum,  to  the  inferior  surface  of  the 
coccygeal  region.  Its  orifice  shows  labia  majora  and  minora.  The  first  is  garnished,  near 
the  inferior  commissure,  with  a  tuft  of  long  fine  hairs ;  the  second  commence  towards  the 
superior  commissure,  and  are  attached  inferiorly  to  the  clitoris.  The  latter  organ  hRS  for  its 
base  a  corpus  cavernosum  1|  inch  long;  its  free  portion  is  flattened  and  tapering,  and  it  may 
become  so  very  salient,  when  the  labia  of  the  vulva  are  drawn  forward,  as  to  resemble  a  small 
penis. 

The  muscles  of  the  vulva  are :  1 .  A  posterior  constrictor.     2.  An  anterior  constrictor — very 

Sanson  has  met  with  anomalies.     For  ourselves,  we  have  found  that  each  teat  has  a  special 
galactophorous  sinus.     In  this  Cow,  therefore,  there  were  five  mammary  glands,  one  of  which 


1002  GENERATIVE  APPARATUS. 

large,  commencing  at  the  coccygeal  vertebrae,  and  inserted  into  tlie  borders  of  the  clitoris.  3, 
Two  erectores  penis  muscles.  4.  A  subischio-cavernous  muscle,  less  voluminous  than  in  the 
male,  but  of  the  same  shape. 

Mammse. — They  are  disposed  as  in  the  Sow  and  Bitch. 

Glands. — The  female  Rabbit  possesses,  like  the  male,  a  pair  of  rectal  and  a  pair  of  anal 
glands. 

In  the  female  Leporide,  it  is  remarked  tliat  the  external  genital  organs  resemble  thosd 
of  the  Rabbit,  and  that  the  internal  ones  hold  a  middle  place  between  those  of  the  Rabbit  and 
doe-Hare;  otherwise  these  organs  show  everything  necessary  for  reproduction. 

Comparison  of  the  Generative  Organs  of  Woman  with  those  of  Animals. 

Ovaries. — These  organs  are  oval,  about  1^  inches  long  and  i  of  an  inch  broad,  and  are 
lodged  in  the  posterior  layer  of  the  broad  ligaments.  They  are  attached  to  the  uterus  by  the 
ligament  of  the  ovary,  and  united  to  the  Fallopian  tubes  by  the  Fallopio-ovarian  ligament. 
Their  structure  is  the  same  as  in  animals.  A  Graafian  vesicle  usually  ripens  every  month  ;  its 
rupture  corresponds  with  the  menstrual  period.  Annexed  to  tiie  human  ovary  is  found  the 
organ  of  Rosenmiiller,  composed  oi"  from  fifteen  to  twenty  tortuous  tubes  opening  into  a  transverse 

Fig.  540. 


II 

uterus  of  the  human  female,  with  its  appendages  (viewed  from  the  front). 
1,  Body  of  the  uterus;  2,  fundus;  3,  cervix;  4,  os  uteri;  5,  vagina,  with  its  colurana  and 
transverse  rugae;  6  fi,  broad  ligament  of  the  uterus;  7,  convexity  of  the  broad  ligament  formed 
by  the  ovary;  8,  8,  round  ligaments  of  the  uterus;  9,  9,  Fallopian  tubes;  10,  10,  their 
fimbriated  extremities;  11,  ovary ;  12,  utero-ovarian  ligament;  13,  Fallopio-ovarian  ligament; 
14,  peritoneum  of  anterior  surface  of  uterus  fit  is  removed  at  the  left  side,  but  on  the  right  is 
continuous  with  the  anterior  layer  of  the  broad  ligament). 

branch ;  these  tubes  are  lined  by  ciliated  epithelium,  and  filled  with  a  yellow  fluid  ;  they  form 
a  closed  system  included  in  the  broad  ligament,  between  the  ovary  and  oviduct. 

Oviduct. — Placed  at  the  upper  border  of  the  broad  ligament,  it  is  nearly  straight,  and 
terminates  by  a  pavilion  notclied  into  about  fifteen  unequal  fringes. 

Uterus.— The  human  uterus  is  situated  between  the  bladder  and  rectum,  being  inclined 
slightly  downwards,  from  before  to  behind.  Its  form  is  very  difl'erent  from  the  uterus  of  the 
animals  we  have  described,  being  that  of  a  flattened  gourd  ;  its  volume  varies  with  age  and  the 
number  of  gestations  ;  it  weighs  about  two  ounces.  It  is  described  as  having  a  body  and 
cervix.  The  body  is  triangular,  and  at  the  extremities  of  its  upper  border  the  Fallopian  tubes 
open  into  it.  The  cervix  is  fusiform  ;  the  projection  it  makes  at  the  bottom  of  the  vagina  is  the 
tench's  nose — a  transversal  slit  bordered  by  two  unequal  lips.  The  inner  face  of  the  cervix 
shows  the  plicas  paZmate— arborizations  formed  by  the  mucous  membrane. 

There  is  not! ling  special  to  be  noticed  in  its  structure. 

The  broad  ligaments  comprise  a  quantity  of  muscular  fibres  between  their  layers,  and  which 
accumulate  at  certain  points  to  form  accessory  folds  ;  among  tliese  the  most  important  are  the 
round  ligaments.  These  leave  the  anterior  face  of  the  uterus,  pass  forward  and  outward,  enter 
the  inguinal  canal,  and  terminate  in  the  connective  tissue  of  the  mons  Veneris. 

Vagina. — This  canal  is  about  2|  inches  wide  :  it  is  in  contact  with  the  rectum,  and  responds 
in  front,  by  connective  tissue,  to  the  bladder  and  urethra.  Its  internal  face  has  longitudinal 
folds— the  columnas  of  the  vagina — which  are  intersected  by  transverse  folds.  Below  the  orifice 
of  the  urethra  is  the  entrance  to  the  vagina,  a  circular  opening  partially  closed  by  the  hymen  in 
virgins.     Rarely  complete,  this  membrane  may  afl'ect  different  shapes,  and  consequently  receive 


^ 


GENERATIVE  APPARATUS  OF  BIRDS.  1003 

various  names— as  horse-shoe,  bilabial,  semilunar,  annular,  and  fringed  hymen.  When  ruptured, 
it  retracts  very  much,  but  there  always  remain  some  vestiges  of  it,  which  are  designated 
carunculse  myrtiformes. 

Vulva.— Thin  presents  a  cavity  and  an  orifice,  as  in  the  domesticated  animals ;  but  the 
cavity  is  not  so  deep,  and  is  named  the  vestibule;  it  extends  to  the  hymen  or  its  debris.  The 
entrance  to  the  vulva  occur  in  the  middle  of  a  cuneiform  prominence  that  is  confounded,  above,  with 
a  kind  of  eminence— the  mons  Fe?iem— wliich  appears  to  protect  the  pubic  symphysis.  It  is 
margined  by  two  folds  on  each  side :  one  cutaneous— the  labia  majora ;  the  other  mucous— the 
labia  minora  (or  nymphse).  The  labia  majora  are  convex  externally,  continuous  above  with 
the  mons  Veneris,  and  unite  below  to  form  an  acute  angle,  named  the  fourchette ;  they  are 
covered  externally  with  hair.  The  labia  minora,  more  or  less  developed,  leave  the  fourchette, 
and  extend  around  the  entrance  to  the  vagina,  uniting  above  the  clitoris,  and  forming  the  prepuce 
of  that  organ. 

The  clitoris  is  lodged  in  the  superior  commissure  of  the  vulva  ;  its  point  is  directed  down- 
wards, especially  during  erection ;  its  base  is  attaclied,  on  each  side,  to  the  two  erectile  lobes 
which  constitute  the  bulb  of  the  vagina  (bulbi  vestibuli). 

Two  racemose  glands— the  vulvo-vaginal,  or  glands  of  Bartholine—pout  their  secretion  over 
the  walls  of  the  vestibule. 

Marnrn^.— These  are  pectoral,  and  two  in  number.  In  their  centre,  they  present  an 
enormous  papilla— the  7iipple— into  which  the  excretory  canals  open ;  it  is  surrounded  by  a 
brown  circle,  the  areola  of  the  nipple. 


CHAPTER  III. 

Generative  Apparatus  of  Birds. 

1.  Male  Generative  Organs. 


The  generative  organs  of  the  male  are  the  testicles,  and  an  excretory  apparatus 
much  simpler  than  that  of  Mammals. 

Testicles. — These  organs  are  placed  in  the  sublumbar  region  of  the  abdominal 
cavity,  behind  the  lungs,  and  below  the  anterior  extremity  of  the  kidneys,  in  front 
of  the  three  last  ribs.  Their  form  is  usually  oval,  and  their  volume  varies  with 
the  different  species,  as  well  as  at  different  seasons  ;  at  the  breeding-season  they 
are  greatly  developed. 

E.ccretory  afparatus. — In  Birds  there  is  not,  properly  speaking,  an  epididymis. 
The  vas  deferens  passes  from  within  the  posterior  extremity  of  the  testicle, 
is  directed  in  a  flexuous  manner  backwards,  draws  near  to  the  ureter  on  its  own 
side,  going  along  the  kidney  with  it,  and  arriving  at  the  cloaca,  where  it  termi- 
nates by  an  orifice  to  be  alluded  to  hereafter.  In  the  Duck,  it  has  near  its 
termination  a  small  oval  vesicle,  always  filled  with  spermatic  fluid. 

Organ  of  copvlation. — This  varies  with  the  species.  In  the  Gallinacge,  it  is 
only  a  small  papilla,  placed  below,  near  the  margin  of  the  cloacal  opening,  and 
between  the  two  orifices  of  the  deferent  canals.  This  papilla  is  traversed  by  a 
furrow,  through  which  the  semen  flows. 

In  the  Palmipedes,  this  organ  is  much  more  developed,  and  is  peculiar. 
Contained  within  a  tubular  cavity  in  the  cloaca,  it  is  protruded  externally  at  the 
moment  of  copulation  by  the  eversion  of  this  cavity,  like  the  finger  of  a  glove  ; 
it  then  appears  as  a  long  pendent  appendage,  twisted  like  a  corkscrew. 


1004 


GENERATIVE  APPARATUS  OF  BIRDS. 


2.  Generative  Organs  of  the  Female. 

The  development  of  the  young  animal  taking  place  external  to  the  female, 
the  generative  organs  are  hmited  to  that  producing  the  ovum,  and  the  duct 
through  which  it  passes  on  leaving  the  ovary. 

Ovari/. — In  birds  there  is  only  one  ovary,  which  is  situated  on  the  left  side, 
the  right  one  becoming  atrophied  very  early  in  nearly  all  species.  This  ovary  is 
situated,  hke  the  testicles,  in  the  sublumbar  region  of  the  abdominal  cavity,  and 
constitutes  a  more  or  less  voluminous  body,  composed  of  a  variable  number  of 

ova  in  process  of  development— some 


Fig.  541. 


OVAKY    OF    THE    BIRD. 


a,  c,  c.  Ova  (eggs)  in  the  various  stages  of  develop- 
ment ;  6,  stieak  without  vessels,  indicating  the 
point  where  the  vesicle  is  about  to  rupture  to 
allow  the  ova  to  escape;  d,  ruptureil  vesicle; 
e,  very  small  ovum  showing  tl^#  cicatriculus. 


very  young,  little,  and  white  ;  others 
more  advanced  in  age,  being  larger  and 
yellow  in  colour.  The  ova  are  en- 
veloped in  a  very  vascular  cellular 
membrane,  which,  when  they  are  ripe, 
splits  in  a  circular  manner,  following 
an  equatorial  line,  and  permits  the 
escape  of  the  essential  part  of  the  egg 
— the  i/elloiv  (yolk),  or  vitellus. 

Oviduct. — This  duct  is  long,  very 
wide  and  dilatable,  and  very  flexuous. 
It  begins,  near  the  ovary,  by  an  un- 
fringed  pavilion,  and  terminates  in  the 
cloaca  by  a  somewhat  narrow  orifice, 
which  is  considerably  widened  when 
the  Qgg  passes  through  it.^  The  egg 
— composed,  on  entering  the  oviduct, 
of  the  fundamental  part  named  the 
yolk,  or  vitellus— h  enveloped  in  an 
albuminous  covering  during  its  pro- 
gress towards  the  cloaca,  and  after- 


wards with  a  protecting  shell.  The  oviduct  of  birds  is,  therefore,  something 
more  than  an  excretory  canal,  as  it  participates  in  the  formation  of  the  ovum. 
It  is  composed  of  three  membranes — an  external  serous,  maintains  the  tortuous 
tube  ;  a  middle,  muscular  ;  and  an  internal,  mucous. 

In  the  two  sexes,  above  the  cloaca  there  is  a  diverticulum  named  the  pouch 
of  Fabricius,  which  is  extirpated  in  Brittany,  in  order  to  render  the  hen  birds 
sterile. 

•  Instances  of  abdominal  "  egg-laying "  have  been  observed.  Reul  gives  examples  in 
which  it  was  due  to  atresia  of  the  oviduct  {Annales  de  Med.  Veterinaire  de  Bruxelles,  1887> 


BOOK  IX. 

EMBRYOLOGY. 

Embryologij  has  for  its  object  the  study  of  the  modifications  which  the  ovum 
undergoes,  from  the  moment  it  is  fecundated  until  it  is  transformed  into  a  new 
being  capable  of  living  in  the  external  world. 

The  points  of  this  subject,  belonging  to  the  domain  of  anatomy,  will  be 
divided  into  three  chapters.  In  the  first,  the  transformations  of  the  ovum  which 
produce  the  embryo  will  be  examined.  In  the  second,  the  various  portions  of 
the  ovum — the  annexes  of  the  foetus — will  be  studied  ;  and  the  third  will  deal 
with  the  development  of  the  foetus. 


CHAPTER  I. 
The  Ovum  and  its  Early  Embryonic  Developments. 

Aeticle  I. — The  Ovum. 

The  ovum  of  the  domestic  mammifers  is  a  vesicle  about  y^Vtr  of  an  inch  in 
diameter  (the  germinal  spot  being  from  ^-^  to  tt^Vtt  of  an  inch),  contained  in 
the  Graafian  follicle,  in  the  midst  of  the  cumulus  proUgera. 

It  possesses  :  1.  An  amorphous,  transparent  enveloping  membrane,  '01  mm. 
thick,  named  the  vitelline  membrane,  or  zona  pellucida.  2.  A  hazy  viscid  fluid, 
holding  in  suspension  a  large  number  of  dark-coloured  granules  and  fat-globules  : 
this  is  the  vitellm,  or  yolk.  3.  The  germinal  vesicle,  a  spherical  transparent 
nucleus  lying  to  one  side  of  the  vesicle,  and  readily  altered.  The  germinal  spot, 
a  kind  of  very  brilliant  nucleolus  seen  in  the  centre  of  the  nucleus. 

According  to  Balbiani,  there  also  exists  in  the  ovum  of  all  animals — from 
insects  up  to  Mammals — beside  the  germinative  vesicle,  a  second  nucleus— named 
Balbiani'' s  or  the  embrgogenous  vesicle — which  plays  a  very  important  part  in  the 
nutrition  of  the  ovum  and  the  phenomena  succeeding  fecundation. 

Article  II. — First  Embryonic  Developments. 

These  include  three  important  events — the  segmentation  of  the  viteUus,  the 
formation  of  the  blastoderm,  and  the  appearance  of  the  embryo. 

These  phenomena  have  been  particularly  studied  in  the  ovum  of  the  Rabbit, 
and  it  is  to  the  researches  of  Van  Beneden  on  this  subject  that  science  owes  the 
most  important  information  on  the  first  phenomena  that  occur  after  fecundation 
in  the  Mammalia. 

1.  Segmentation  of  the  Vitellus. — This  takes  place  immediately  after 


1006 


EMBRYOLOGY. 


fecundation  ;  and  although  we  have  not  to  treat  of  fecundation  itself,  yet  it  ia 
well  to  bring  forward  the  essential  fact  resulting  from  modern  investigations 
on  this  point,  showing  that  this  great  act  consists  in  the  fusion  of  two  germs 
— the  female  pronucleus,  arising  from  the  division  of 
the  germinal  vesicle  ;  and  the  male  pro)iucleus,  due  to 
the  transformation  and  migration  of  the  spermatozoid. 
These  two  elements,  by  their  fusion,  originate  the  i/olk- 
nucleus  which,  by  its  double  origin,  contains  the  material 
elements  of  hereditary  continuity. 

The  division  of  the  yolk-nucleus  begins  and  deter- 
mines the  segmentation  of  the  yolk — equivalent  to  cell- 
proliferation. 

Before  becoming  segmented,  the  yolk  separates  from 
its  enveloping  membrane,  retracts,  and  leaves  around  it 
a  space  occupied  by  a  transparent  fluid. 

The  segmentation  of  the  yolk  is  total,  the  entire 
mass  undergoing  proliferation,  and  the  first  effect  of 
this  is  the  production  of  two  cells  resulting  from  the 
division  of  the  yolk.  These  two  primary  cells,  or 
segmentation  globes,  in  their  turn  divide  and  give  rise 
to  two  generations  which  have  different  destinies  to 
fulfil.  This  specialization  is  already  naturally  contained 
in  the  two  primary  globes  of  segmentation,  and  is 
marked  by  particular  characters.  The  two  globes  are, 
in  fact,  unequal  in  size.  The  largest — the  edodermic 
globe — is  transparent  ;  the  second — the  endodermic  globe 
— is  charged  with  granules  which  are  readily  stained  by  osmic  acid. 

The  proliferation  of  the  ectodermic  and  endodermic  globes  continues,  and  in 
Buch  a  manner  that  the  segmentation  globes  issuing  from  the  first  proceed  towards 


A  GRAAFIAN  VESICLE,  FROM 
A  WOMAN  THIRTY-TWO 
YEARS  OF  AGE. 

In  this  is  seen  the  epithelial 
covering  formed  of  poly- 
gonal cells,  and  an  ovum 
in  which  there  is  at  a  the 
germinal  vesicle  with  its 
spot,  and  at  h  the  embryo- 
genous  vesicle,  much 
smaller,  and  surrounded 
by  numerous  granules 
which  are  disseminated  in 
the  vitellus;  c  is  the 
zonula  pellucida. 


OPTICAL  SECTIONS   OF   THE   OVUM   OF   A    RABBIT   IN    TWO   STAGES 


AFTER  SEGMENTATION. 


ep,  Epiblast,  or  ectoderm ;  hy,  hypoblast,  or  entoderm  ;  hp,  blastopore.    The  ectoderm  and  endoderm 
are  differently  shaded. 


the  periphery,  and  tend  to  envelop  the  mass  of  those  which  arise  from  the  division 
of  the  endodermic  globes.  Finally,  in  about  seventy  hours  after  fecundation,  in 
the  Rabbit,  the  envelopment  is  complete. 


EARLY  EMBRYONIC  DEVELOPMENTS. 


1007 


The  yolk  is  formed  of  a  peripheral  layer  of  clear  transparent  cells— the 
ectoderm,  or  epiblast— lining  the  vitelline  membrane,  and  embracing  a  central 
mulberry  mass  (morula)  of  polyhedral  and  granular  cells— the  endoderm,  or  hypo- 
llast.  The  ectoderm  shows  at  one  of  its  points  an  aperture— the  hlastopore,  or 
anus  of  Rusconi— into  which  penetrates  and  closes  it,  but  without  overlapping  it, 
a  prolongation  of  the  endoderm— the  cork  of  Ecker.  At  this  phase  in  its  evolu- 
tion, the  yolk  constitutes  what  is  termed  in  comparative  embryology,  the  meta- 
gastnda. 

2.  Passage  of  the  Metagastrula  to  the  Uterus,  and  Formation  op 
THE  Vesicle  and  Blastodermic  Layers. — As  soon  as  the  metagastrula  has 
reached  the  uterus,  it  commences  to  be  transformed  into  a  clear  and  transparent 
vesicle,  which  grows  rapidly,  attaining  in  four  or  five  days  a  diameter  of  from 
8  to  9  mm.,  and  constituting  the  blastodermic  vesicle,  or  blastoderm. 

The  appearance  of  the  blastoderm  is  marked  by  the  appearance  of  a  fissure 
that  separates  the  ectoderm  from  the  endoderm,  leaving  them  only  adherent  at 
a  point  corresponding  to  the  blasto- 
pore, which  was  already  formed 
towards  the  end  of  the  third 
day. 

Owing  to  the  pressure  of  the 
fluid  that  fills  it  and  tends  to  ac- 
cumulate, the  ectoderm  becomes 
distended  and  fissures ;  its  cells 
multiply,  and  it  fiattens  so  as  to 
embrace  a  layer  that,  towards  the 
ninetieth  hour,  attains  from  '15  to 
•17  mm.  The  endoderm,  pressed 
upon  by  the  fiuid,  is  deformed  and 
spread  over  a  point  beneath  the 
ectoderm,  where  it  becomes  the 
gastrodisc.  The  vesicle,  formed  at 
this  part  of  two  superposed  layers, 
is  still  monodermic  everywhere  else 
(Fig.  544)  ;  nevertheless,  the  cells 
of  the  gastrodisc  change  in  charac- 
ter, becoming  flattened,  and  in  an 
ovum  of  from  105  to  115  hours, 
having  a  diameter  of  from  -9  to  2 
mm.,   they    form    an    endothelial 

lining  to  the  ectoderm  to  an  extent  which  increases  with  the  marginal  growth  of 
the  internal  layer. 

But  all  the  cells  of  the  endoderm  are  not  so  transformed.  In  ova  of  five 
days  old,  having  from  2  to  4  mm.  to  the  centre  of  the  gastrodisc,  some  are 
found  which  have  preserved  their  primary  characters  of  segmentation  spheres, 
and  remain  interposed  between  the  ectoderm  and  endoderm— between  the 
external  and  internal  layers.  This  residual  cellular  mass,  which  has  escaped 
the  endodermic  transformation,  is  the  point  of  depr.rture  of  a  third  layer— the 
mesoderm  {mesoblast),  or  middle  lager,  which  is  already  marked  at  this  period  by 
a  circular  spot  at  the  pole  of  the  gastrodisc.  It  is  this  spot  that  has  been  known 
since  the  time  of  Bischoff  and  Coste  as  the  germinal  area  or  streak.  The  germijial 
—also  named  the  embryonal— area  is  only  at  first  the  optical  signification  of  the 


OVUM   OF   THE   RABBIT,   NINETY   HOURS  AFTER 

FECUNDATION. 

br,  Cavity  of  the  blastodermic  vesicle;  ep,  epiblast,  or 
ectoderm,  forming  a  complete  sac  ;  hy,  hypoblast, 
or  endoderm,  forming  the  gastrodisc;  zp,  zonula 
pellucida. 


1008  EMBRYOLOGY. 

appearance  of  the  middle  layer,  and  although  the  embryo  at  a  later  period  reveals 
its  first  outlines  in  this  part  of  the  blastoderm,  it  must  not  be  forgotten  that  it 
is  not  yet  traced  ;  so  that  the  qualification  of  embryonal  area  cannot  be  accepted 
in  a  literal  sense. 

In  the  following  days,  the  internal  and  middle  layers  continue  to  grow.  By 
multiplication  of  the  elements  of  the  mesoderm,  the  germinal  area  increases  in 
thickness  and  in  surface,  pushing  up  the  ectoderm,  which  becomes  salient  like  a 
shield,  and  has  a  well-defined  circular  outline.  The  germinal  area  at  this  moment 
reveals  the  thickening  of  the  central  region  of  the  mesoderm  (mesoblast),  which 
extends  by  its  borders  at  the  same  time  as  the  endoderm,  so  that  the  walls  of  the 
vesicle  are  soon  composed  of  three  layers  throughout. 

From  the  seventh  to  the  eighth  day,  the  blastoderm  figures  as  an  elliptical 
vesicle,  somewhat  flattened,  from  7  to  8  mm.  in  diameter,  filled  with  a  trans- 
parent albuminous  fluid,  and  formed  of  three  superposed  layers.  It  does  not  yefc 
exhibit  any  traces  of  morpliological  differentiation  except  the  germinal  area,  or 

Fig.  545. 


VIEWS   OF    THE    BLASTODERMIC    VESICLE   OF    A    RABBIT    ON    THE    SEVENTH    DAY. 
A.  FROM    ABOVE;     B,  FROM    THE    SIDE. 

ag,  Embryonal  area ;  ge,  limit  of  the  gastrodisc  or  endoderm  (hypoblast). 

central  thickening  of  the  mesoderm.  It  is  true,  however,  that  the  outline  of  the 
embryo  soon  becomes  apparent,  and  the  three  layers  of  the  blastoderm  play  a 
distinct  part  in  its  formation,  which  it  is  necessary  to  indicate  beforehand. 

a.  The  external  layer — ectoderm,  epiblasf — is  also  named  the  sensorj/  or 
smsitive  layer,  because  it  gives  rise  to  the  epidermis  or  epidermic  formation,  and 
to  all  the  nerve-elements  of  the  sensory  terminations — retina,  organ  of  Corti, 
etc. ;  it  also  furnishes  the  outline  of  the  central  nervous  system. 

h.  The  internal  layer — endoderm,  ht/jwblast — also  merits  the  name  of  mucous 
layer,  as  it  originates — not  the  mucous  membranes,  as  is  often  said — but  the 
epithelium  of  the  post-diaphragmatic  portion  of  the  digestive  apparatus  and  the 
glands  annexed  thereto —liver  and  pancreas. 

c.  The  middle  layer — mesoderm,  mesohlast — serves  as  a  centre  for  all  the  other 
tissues — connective,  muscular,  blood-vessels  and  lymphatics,  serous  membranes, 
sexual  glands,  etc.  The  multiplicity  of  its  future  specializations  does  not,  there- 
fore, authorize  a  particular  denomination,  though  it  is  at  times  designated  as  the 


EARLY  EMBRYONIC  DEVELOPMENTS.  1009 

serous  or  germinal  layer.  The  qualification  of  vascular  layer  should  not  be  given 
to  it,  as  it  belongs  to  a  special  formation  which  will  be  alluded  to  hereafter. 

3.  Appearance  and  Formation  of  the  Embryo.— The  place  in  which  the 
embryo  is  developed  is  prepared  by  a  differentiation  in  the  germinal  area.  At 
first  opaque  throughout  its  extent,  it  becomes  clear  in  Ids  central  region,  and  is 
thus  divided  into  two  concentric  and  circular  zones— the  transjmrent  and  the 
ofaque  zone.  The  phenomena  which  follow  are  easily  studied  in  the  Chick,  and 
it  is  in  it  that  we  will  observe  them.  But  it  is  necessary  at  first  to  examine  the 
composition  of  a  Bird's  q^;^  ;  though  its  complexity  is  due  to  the  circumstance 
that  the  development  of  the  embryo  takes  place  externally,  and  that  the  germ 
must  therefore  carry  with  it  its  nutriment  and  its  protective  envelopes. 

Essential  parts. — The  Qgg  of  Birds — like  that  of  Reptiles  and  all  the  Oviparous 
Vertebrates — is,  then,  only  a  germ  provided  with  an  enormous  quantity  of  aliment, 
and  it  is  this  mass  that  constitutes  the  yolk.  The  germ  itself — that  which  is  the 
physiological  equivalent  of  the  ovum  of  Mammals— is  represented  by  a  small, 
circular,  white  spot — the  cicatricula — situated  on  the  surface  of  the  yolk,  beneath 
the  vitelline  membrane  ;  in  this,  exclusively,  resides  the  evolutionary  force,  and 
it  is  this  spot  which  undergoes  segmentation.  It  corresponds,  then,  to  the  whole 
of  the  vitellus  of  the  ovum  in  Mammalia,  and  merits  the  name  of  plastic  vitellus,  to 
distinguish  it  from  the  nutritive  vitellus  represented  by  the  yolk.  Although  there 
is  no  marked  line  of  demarcation  between  the  two  masses,  and  although  from  the 
plastic  vitellus  there  emanates  a  kind  of  protoplasmic  atmosphere  that  penetrates 
the  nutritive  vitellus,  it  might  be  maintained  that  the  latter  does  not  participate 
to  any  extent  in  the  segmentation,  which  remains  exclusively  localized  in  the  plastic 
vitellus.  In  this  sense  it  may  be  said  that  the  segmentation  is  partial  in  the  ova 
of  the  type  named  meroUastic.  The  ova  of  Mammalia  and  those  of  the  same  type 
are,  on  the  contrary,  holoblastic — ova  in  which  segmentation  involves  the  whole 
of  the  yolk. 

In  the  Fowl,  whether  or  not  fecundation  has  taken  place,  segmentation  occurs 
during  the  passage  of  the  Q^g  in  the  tube,  and  is  nearly  completed  at  the  moment 
of  laying.  The  cicatricula  visible  in  the  vitelline  membrane  therefore  represents, 
in  the  new-laid  Qgg,  not  the  primary  and  simple  germ,  but  the  germ  segmented 
and  ready  to  form  the  blastoderm.  To  see  this  properly,  a  fresh  egg,  sliould  be 
opened  in  water  ;  the  centre  of  gravity  of  the  yolk  being  eccentric,  the  vitellus 
passes  in  a  certain  direction,  bringing  the  cicatriculus  to  the  highest  pole  of  the 
yolk,  in  the  centre  of  the  visible  hemisphere. 

Accessory  parts. — In  passing  through  the  oviduct,  the  ovum — reduced,  as  we 
have  seen,  to  the  mass  of  the  vitellus — is  surrounded  successively  by  :  1.  A  layer 
of  albumen.     2.  A  testaceous  membrane.     3.  A  shell. 

The  albumen — or  "  white  " — forms  three  layers  of  different  densities.  As,  in 
its  progression,  the  egg  is  submitted  to  a  rotatory  mo\'ement  on  its  greater  axis, 
so  the  albumen  undergoes  a  twist  and  a  particular  condensation  along  this  axis  ; 
in  this  way  are  formed  two  kinds  of  coverings,  that  can  be  seen  floating  and 
adhering  to  the  yolk  of  eggs  opened  in  water,  and  which  are  named  the  chulazm. 

The  shell  membrane  (jnemhrana  putaminis),  fibroid  in  appearance,  at  the 
thick  pole  is  doubled  into  two  layers  to  form  a  cavity — the  air-chamber.  This 
cavity  increases  as  development  goes  on,  in  order  to  meet  the  respiratory  demands 
of  the  embryo,  or  fcetus  ;  while  the  yolk  and  albumen  become  progressively 
expended  as  the  foetus  grows. 

The  shell  is  an  organic  framework  impregnated  with  lime  salts  ;  but  it  is 


1010 


EMBRYOLOGY. 


unnecessary  here  to  enter  into  a  consideration  of  the  very  complex  details  of  its 
structure  and  mode  of  formation. 

The  above  description  shows  the  fundamental  identity  between  the  holoblastic 


DIAGRAMMATIC   SECTION   OF   A   FOWL'S   UNHATOHED   EGG. 

I.,  Blastoderm;  w.y.,  white  vitellus,  consisting  of  a  pyrit'orm  central  mass  and  a  certain  number  of 
concentric  layers ;  y.,  yellow  vitellus,  in  alternate  layers  with  the  preceding ;  v.t.,  vitelline 
membrane;  x.,  layer  of  albuminous  fluid  surrounding  the  vitellus;  w.,  consistent  albumen  ;  ch.L, 
chalazae;  a.ch.,  air-chamber;  i.s.m.,  inner  layer  of  the  testaceous  or  shell  membrane;  s.m., 
external  layer  of  ditto ;  s.,  shell. 


Fig.  547. 


and  meroblastic  ova  ;  they  only  differ  in  the  enormous  predominance  of  the 
nutritive  vitellus  in  the  latter.     This  predominance  has  the  mechanical  effect  of 

localizing  the  phenomena  of  segmentation  to 
one  pole  of  the  egg — that  in  which  is  the  plastic 
vitellus ;  and  we  have  seen  that  this  is  com- 
pleted at  the  moment  of  laying.  The  blastoderm 
that  issues  from  this  centre  of  proliferation 
necessarily  assumes  the  shape  of  a  disc — the 
germinal  disc ;  then  of  a  spherical  cap  lying  on 
the  yolk  by  its  concavity,  and  tending  to  em- 
brace it  by  the  progressive  extension  of  its 
circular  border.  This  investment  is  only  com- 
pleted towards  the  sixth  day  of  incubation,  and 
the  blastoderm  is  therefore  late  in  assuming 
the  vesicular  form.  Notwithstanding  differences 
of  the  same  kind,  arising  from  another  manner 
of  proceeding  than  that  observed  in  Mammals, 
the  successive  formation  of  the  germinal  area, 
and  its  doubling  into  an  opaque  and  a  trans- 
parent zone,  take  place. 

The  appearance  of  the  embryo  is  manifested 
by  a  temporary  formation  known  as  the  primitive  trace — embryonal  rudiment,  or 
axile  layer.     The  primitive  trace  is  marked  on  the  blastoderm  by  two  dark  streaks 


pr.s 

AREA  PELLUCIDA  IN  THE  VERY  EARLY 
BLASTODERM  OF  THE  CHICK,  SHOWING 
THE  PRIMITIVE  LINE  AT  ITS  FIRST 
APPEARANCE. 

pr.s,  primitive  trace  ;  ap,  transparent 
or  pellucid  area.;  a.op,  opaque  area. 


EAKLY  EMBRYONIC  DEVELOPMENTS  1011 

close  together,  separated  by  a  bright  line  (primitive  streak),  but  continuous  with 
each  other  in  front.  All  the  transparent  zone  in  front  of  the  primitive  line  has 
been  designated  by  Duval  as  the  tergal  zone,  and  we  adopt  this  correct  and 
convenient  term.  The  growth  of  the  primitive  line  takes  place  at  its  posterior 
extremity,  and  to  this  circumstance  is  due  the  change  in  shape  of  the  transparent 
area,  which  becomes  pyriform. 

It  is  indispensable  to  see,  on  transverse  sections,  the  arrangement  of  the 
blastoderm  and  its  layers  at  the  primitive  trace.  The  ectoderm,  formed  of  a 
layer  of  cubical  cells,  is  curved  in  the  middle,  and  its  deep  face  becomes  con- 
founded with  the  mesoderm.  The  latter,  formed  of  small  angular  cells,  is  placed 
between  the  two  layers,  and  enters  the  substance  of  the  opaque  zone.  The 
endoderm,  formed  of  a  single  layer  of  fiat  cells  throughout  the  extent  of  the  trans- 
parent zone,  suddenly  becomes  thicker  at  the  opaque  zone,  by  the  stratification 
of  its  cells  still  filled  with  vitelline  granules.  These  marginal  thickenings  have 
been  named  by  Kolliker  the  endodermic  ridges ;  it  is  to  them  that  the  opaque 
zone  owes  its  optical  characters. 

This  transverse  section  enables  us  to  see,  for  the  first  time,  the  three  super- 


Fig.  548. 


TRANSVERSE   SECTION   OF   A   BLASTODERM   OF   THE   SAME   AGE   AS   FIG.  547. 

pos.,  Primitive  trace ;  ep.,  epiblast,  or  ectoderm ;  hy.,  endoderm  ;  yk.,  above,  the  endodermic  ridge. 
The  section  passes  nearly  through  the  middle  of  the  primitive  trace. 

posed  layers  of  the  germinal  disc  ;  and  it  exhibits,  between  the  ectoderm  and  the 
mesoderm,  a  curious  and  characteristic  continuity  of  the  primitive  trace,  which  has 
for  a  long  time  exercised  the  wisdom  of  embryologists,  and  given  rise  to  debates 
now  terminated.  We  will  say  nothing  of  the  solution  arrived  at,  as  it  would  lead 
us  too  far  from  the  scope  of  this  work  ;  and  only  refer  to  the  primitive  trace, 
because  for  a  long  time  it  passed  for  what  it  was  not,  and  also  because  there  was 
seen  in  it  a  trace  of  the  central  nervous  system,  which  only  appeared  morpho- 
logically towards  the  twentieth  hour.  Destined  to  retrograde  and  disappear, 
the  primitive  trace  is  only  on  the  threshold  of  the  embryonal  development — an 
atavic  episode,  the  significance  of  which  cannot  be  given  here,  but  of  which  it 
is  necessary  to  speak,  and  to  point  out,  in  order  not  to  confound  it  with  the 
origin  of  the  nervous  system. 

Article  III.— General  Direction  of  Development.— Vertebral  Type. 

The  ulterior  modifications  in  the  three  layers  of  the  blastoderm— inflections, 
invaginations,  doublings— tending  to  the  realization  of  this  type,  and  from  the 
end  of  the  first  day,  furnish  very  interesting  indications. 

We  will  study  these  in  a  blastoderm  from  the  twentieth  to  the  twenty-fourth 
hour  (Fig.  547). 


1012 


EMBRYOLOGY. 


The  outline  of  the  embryo  distinctly  appears  as  a  very  elongated  ellipse. 
At  its  inferior  extremity  is  seen  (Fig.  549)  a  very  slender  crescent,  the  per- 
spective of  which  does  not  give  so  good  an  idea  of  its  disposition  as  longitudinal 
sections  do.  This  appearance  of  the  blastoderm  seen  on  the  surface,  is  due  to  the 
inflection  of  its  margins  downwards  and  inwards.  The  elliptical  disc  represented 
by  the  embryo,  and  which  is  lying  flat  on  the  yolk,  gradually  has  its  borders 
curved  downwards,  and  converging  towards  the  middle  on  its  ventral  face.  This 
inflection  of  the  embryo  brings  about  the  formation  of  the  walls  of  the  body 
and  its  cavities.  In  their  progressive  incurvation,  the  borders  circumscribe  an 
aperture,  which  contracts  and  becomes  the  umbilicus.  The  inflection  proceeds 
from  before  to  behind,  and  is  constituted  by  successive  folds,  which  have  been 


Fig.  550.    . 


AREA  PELLUCIDA  OF  THE  BLASTO- 
DERM OF  A  CHICK  SOON  AFTER 
THE  FORMATION  OF  THE  PRIMI- 
TIVE GROOVE. 

pr,  Primitive  trace  with  the  primitive 
groove ;  af,  amniotic  fold.  The 
shaded  part  around  the  primitive 
trace  shows  the  extension  of  the 
mesoblast. 


AREA  PELLUCIDA  IN  A  BLASTODERM  OP 
EIGHTEEN  HOURS,  SHOWING  THE 
MEDULLARY   GROOVE. 

pr,  Primitive  trace;  m.c,  medullary  groove, 
or  dorsal  furrow;  A,  medullary  fold. 


designated,  from  their  situation,  as  the  cephalic  fold,  lateral  fold,  and  caudal 
fold. 

Fig.  .549  shows  precisely  the  commencement  of  the  cephalic  fold — that  is, 
the  first  trace  of  that  grand  phenomenon  which  leads  to  the  formation  of  the 
great  splanchnic  cavities.  It  may  be  remarked  that,  throughout,  the  three  layers 
of  the  blastoderm  engaged  in  forming  the  embryo  are  continued  by  their  borders 
with  the  other  parts  of  the  blastoderm.  It  may  also  be  stated  that  the  embryo 
is  only  a  morphological  specialization  of  the  blastodermic  vesicle,  and  that  there 
is  reason  to  distinguish  the  embryonal  blastodermic  layers  from  the  extra- 
embryonal  layers.  "We  shall  soon  see  the  why  and  wherefore,  by  reason  of  the 
continuity  of  the  two  regions  of  the  blastoderm,  of  the  modifications  in  the 
embryonal  layers  bringing  about  correlative  modifications  in  the  extra-embryonal 
layers. 


GENERAL  DIRECTION  OF  DEVELOPMENT.  lOlS 

The  tergale  zone  is  occupied  by  a  new  formation,  which  appears  to  be  the 
continuation  of  the  primitive  trace,  but  is  in  reality  altogether  distinct.  This  is 
a  furrow  formed  by  a  longitudinal  excavation  in  the  ectoderm,  and  which  com- 
mences the  trace  of  the  central  nervous  system  ;  it  is  named  the  medullary 
groove,  or  dorsal  furrow.  At  the  bottom  of  this  groove  a  dark  line  betrays 
the  presence  of  the  chorda  dorsalis,  or  notochord — a  provisional  skeletal  stalk 
that  sustains  the  medullary  groove. 

The  presence  of  the  medullary  groove  leads  to  the  division  of  the  embryo 
into  two  perfectly  distinct  zones — the  spinal  zone,  corresponding  with  the 
medullary  groove,  and  the  marginal  zone  comprising  all  the  other  part  to  the 
borders  of  the  embryo.  These  facts  become  very  intelhgible  in  a  transverse 
section  through  the  middle  of  the  medullary  groove  (Fig.  551).  It  is  seen  how 
the  latter  is  formed  by  the  thickening  and  median  inflection  of  the  ectoderm, 

Fig.  551. 


TRANSVERSE    SECTION   OP    A   BLASTODERM   AFTER   THE   FORMATION   OF    THE    MEDULLART    GROOVE 
AND   THE   NOTOCHORD. 

A,  Ectoderm  ;   B,  mesoderm ;   c,  endoderm :   mc,  medullary  groove  ;   mf,  medullary  fold  ;   ch,  noto- 
chord.    The  figure  represents  the  left  half  of  the  section. 

which  resembles  a  V  widely  open,  the  two  branches  of  the  V  constituting  the 
medullary  folds  (Fig.  550).  By  their  inflection  and  union  they  ultimately  form 
a  closed  tube — the  neural  canal,  perhaps  better  designated  as  the  neuraxis 
(Fig.  552). 

The  endoderm  does  not  offer  any  other  modification,  but  the  mesoderm 
undergoes  transformations  of  the  highest  interest.  The  interposition  of  the 
chorda  dorsalis  divides  it  into  two  symmetrical  moieties.  The  thickened  parts, 
which,  in  the  two  moieties,  are  subjacent  to  the  corresponding  medullary  fold, 
form  the  lateral  layers  (or  plates).  Beyond,  the  mesoderm  shows,  in  certain 
embryos  at  this  time,  a  very  marked  indication  of  a  decisive  event  in  the  evolu- 
tion of  the  embryo  and  the  realization  of  the  vertebral  type ;  but  it  is  more 
convenient  to  study  this  in  a  more  advanced  embryo. 

In  transverse  sections,  the  mesoderm  can  be  seen  undergoing  cleavage  into 
two  layers  (Fig.  552).  The  space  between  these — and  which  is  really  a  fissure 
of  no  importance — grows  to  a  great  extent ;  this  is  the  pleuro-peritoneal  fissurSy 
which  at  a  later  period  becomes  the  pleuro-peritoneal  cavity. 

The  two  layers  resulting  from  the  splitting  of  the  mesoderm,  perform  very 
difl'erent  functions.  The  superficial  layer,  which  furnishes  materials  for  the 
parieties  of  the  body — including  the  dermis  of  the  skin — has  been  named  the 
musculo-cutaneous  layer ;  the  deeper  one  is  designated  the  fibro-intestinal  layeTy 
which  sufficiently  indicates  the  direction  of  its  approaching  evolution. 

In  their  ulterior  modifications,  the  two  layers  remain  closely  allied  to  the 
ectoderm  and  endoderm  ;  and  by  this  association  they  constitute  formations 
akeady  complex,  which  it  is  necessary  to  note  and  to  qualify.    The  musculo- 


1014 


EMBRYOLOGY. 


cutaneous  layer  lining  the  ectoderm  constitutes  the  somatopUure ;  and  the  fibro- 
intestinal  layer  lining  the  endoderm  constitutes  the  splanchnopleure. 

But  it  is  essential  to  remark  that  phenomena  of  the  same  order  occur  pro- 
gressively in  the  extra-embryonal  mesoderm,  which,  throughout  its  extent, 
undergoes  delamination,  and  becomes  two  layers  equally  alhed  with  the 
ectoderm  and  endoderm.  It  is  sufficient  to  add  that  the  somatopleure  and 
splanchnopleure  are  continued  beyond  the  embryo  by  two  identical  formations, 
which  it  is  convenient  to  designate  as  the  extra-embryonal  somatopleure  and 
splanchnopleure. 

We  have  given  all  the  facts  and  adopted  the  language  which,  up  to  the 
present,  can  be  embraced  in  a  preliminary  view  of  the  general  direction  of  the 
development  and  the  manner  in  which  the  vertebral  type  is  realized,  as  well  as 


TRANSVERSE   SECTION   OF  THE   DORSAL   REGION   OF   AN   EMBRYO   CHICK  OF   FORTY-FIVE   HOURS. 

A,  Ectoderm  ;  B,  mesoderm  ;  M.c,  neuraxis  ;  P.v.,  lateral  layer,  or  mesoblastic  limit ;  p.p.,  pleuro* 
peritoneal  cavity  ;  c.h.,  notochord  ;  S.o.,  somatopleura  ;  S.p.,  splanchnopleura  ;  W.d.,  Wolffian 
canal;  a.o.,  aorta;  v,  blood-vessels;  w,  mesodermic  ridge,  or  germinal  wall;  op,  limit  of  the 
opaque  area  and  area  pellucida.     The  figure  represents  the  right  half  of  the  section. 


the  correlations  between  the  embryonal  and  extra-embryonal  blastoderms.  The 
study  of  these  correlations  allows  us  to  trace  the  origin  of  the  envelopes  which 
protect  the  foetus,  and  are  known  as  the  annexes  of  the  foetus. 

In  Fig.  553  is  given  a  series  of  sections  of  an  embryo  more  or  less  advanced. 
In  sections  F  and  I  the  embryonal  somatopleure  and  splanchnopleure  are  already 
iucurvated  downwards  and  inwards.  In  passing  from  F  to  I,  we  see  how  the 
splanchnopleure  of  each  side  advance  towards  each  other,  and  tend  to  form  a 
tube  opened  inferiorly  at  each  section — this  is  the  intestine.  Its  walls,  not 
joined  at  this  point,  are  continuous  with  the  extra-embryonal  splanchnopleure, 
which  is  really  the  umbilical  vesicle ;  in  Birds,  the  latter  contains  the  mass  of 
the  yolk.  Above  the  intestine  are  seen  the  superposed  sections  of  the  notochord 
and  neural  canal ;  and  it  is  the  order  of  this  superposition  that  is  characteristic 


GENERAL  DIRECTION  OF  DEVELOPMENT. 


1015 


—-w 


FROM    A   TO   N   IS   A  SERIES  OF   DIAGRAMMATIC   FIGURES  SHOWING   THE    MANNER   IN   WHICH   THE 
EMBRYO    AND    ITS    ENVELOPES    ARE    FORMED. 

ttt,  Vitelline  membrane;  e,  embryo;  pp,  pleuro-peritoneal  cavity;  af,  folds  of  the  amnion;  a, 
amnion  proper ;  ae  or  ac,  cavity  containing  the  liquor  amnii ;  al,  allantois ;  a'  digestive  tabe  ;  9 
or  ys,  vitellus,  or  vitellin  sac. 


1016  EMBRYOLOGY. 

of  the  vertebral  type.  The  alliance  of  the  embryonal  and  extra-embryonal 
blastoderms  has,  at  the  commencement,  a  form  that  allows  us  to  understand  the 
origin  and  mode  of  formation  of  the  foetal  annexes — umbilical  vesicle,  amnion, 
chorion,  aUantois.  Before  proceeding  to  the  description  of  these  organs,  we  will 
examine  precisely  their  origin. 

It  has  been  already  shown  that  the  umbilical  vesicle  is  nothing  more  than 
the  whole  of  the  extra-embryonal  splanchnopleure.  The  amnion  is  derived  from 
the  extra-embryonal  somatopleure  ;  from  F  to  I  this  derivation  may  be  followed. 
Around  the  embryo  the  somatopleure  undergoes  a  double  inflection — one  that 
establishes  the  limits  between  its  two  embryonal  and  extra-embryonal  parts, 
and  passes  up  towards  the  back  of  the  embryo  ;  and  another — C— which  is 
continued  over  the  inner  face  of  the  vitelline  membrane,  and  is  named  the  fold ; 
the  amniotic  layer  comprised  between  the  two  inflections  constitutes  the  amnion. 
This  membrane  is  made  complete  by  the  union  of  the  amniotic  folds  (I)  ;  the 
embryo  is  entirely  enclosed  in  the  amnion.  The  union  of  the  amniotic  folds 
entails,  at  the  same  time  as  the  occlusion  of  the  amnion,  the  occlusion  of  the 
remainder  of  the  extra-embryonal  somatopleure,  which  lines  the  whole  of  the 
internal  face  of  the  vitelline  membrane,  and  forms  a  continuous  and  independent 
membrane — the  serous  layer,  or,  better,  the  chorion. 

The  umbilical  vesicle,  the  amnion,  and  the  chorion,  circumscribe  a  space 
named  the  external  calome,  and  communicating  freely  with  the  pleuro-peritoneal 
cavity. 

In  Figs.  E  and  H,  showing  longitudinal  sections,  are  seen  the  general 
relations  of  all  these  parts.  At  al,  Fig.  Gr,  is  observed  the  origin  of  the  aUantois, 
which  appears  to  be  only  a  diverticulum  of  the  last  portions  of  the  intestines. 
The  allantoid  sac  soon  passes  into  the  ccelome,  and  there  develops  in  size  and 
shape  according  to  the  species  of  the  animal. 

In  the  preceding  chapter,  we  have  seen  by  what  evolutive  modes  the  foetal 
envelopes  or  membranes  are  derived  from  the  intra-embryonal  part  of  the  somato- 
pleure and  splanchnopleure.  These  envelopes  or  membranes  are  represented  in 
the  diagrammatic  figure,  553.  To  them  are  joined  the  cord  of  vessels  and  the 
capillaries  that  establish  the  relations  between  the  mother  and  progeny.  The 
whole  receive  the  name  of  annexes  of  the  foetus. 


CHAPTER   II. 
THE    PCETAL   ENVELOPES   OP    SOLIPEDS. 

Preparation. — The  dissection  of  the  annexes  of  the  foetus  is  a  delicate  operation ;  but  a 
good  idea  of  their  arrangement  may  be  obtained  in  several  ways. 

1.  The  embryo  should  be  first  removed  from  the  uterus.  This  is  very  easily  effected  in 
Solipeds,  as  the  adhesions  between  the  placenta  and  the  uterus  are  nearly  always  destroyed  when 
dissection  is  undertaken.  With  the  foetus  of  Ruminants,  it  is  necessary  to  open  the  uterus 
from  the  cervix  to  the  summits  of  the  cornua,  the  incision  passing  between  the  cotyledons.  la 
order  to  accomplish  this,  the  point  of  the  branch  of  a  pair  of  scissors  is  passed  between  the 
chorion  and  uterus,  in  raising  the  wall  of  the  latter.  The  cotyledons  are  then  sought  for. 
With  the  foetus  of  the  Cow,  the  chorion  is  carefully  pulled  from  the  uterine  cotyledon  in  order 
to  separate  the  placentas ;  with  that  of  the  Sheep  and  Goat,  the  cotyledons  are  pressed  between 
two  fingers,  in  order  to  expel  the  chorial  villi  from  their  interior. 


THE  FOSTUS.  1017 

2.  The  foetus  being  isolated,  the  chorion  is  studied  with  regard  to  shape  and  external 
aspect.  To  scl-  the  relations  of  its  internal  face  with  the  other  annexes,  we  may  resort  to  a 
plan  which  gives  good  results  with  the  foetus  of  Ruminants.  This  consists  in  tilling  tlie 
allantois  and  amnion  by  small  openings  with  diflferent-coloured  fluids.  The  limits  of  the  two 
sacs  can  then  be  very  well  made  out  through  the  cliorion,  while  their  reciprocal  relations  can 
also  be  observed.  With  Solipeds,  the  allantoid  cavity  must  necessarily  be  opened ;  the  mem- 
brane of  that  name  is  partially  separated  from  the  inner  surface  of  the  chorion  by  blowing  in 
air  along  the  principal  divisions  of  the  vessels  of  the  cord,  by  means  of  a  straw  or  blow-tube. 

3.  To  complete  the  study  of  the  amnion  and  the  allantois  of  Ruminants,  it  is  best  to  blow 
in  air  beneath  the  chorion,  after  removing  the  contents.  The  chorion  is  then  carefully  taken 
away,  in  breaking  through — by  means  of  the  fingers  and  forceps — the  laminal  tissue  uniting 
these  two  membranes;  in  the  same  way  are  destroyed  the  fasciculi  which  bind  the  allantois 
to  the  amnion.  In  Solipeds,  notliing  is  more  easy  than  to  inflate  the  amnion,  and  to  study 
its  shape  and  relations.  The  chorial  layer  of  the  allantois  is  demonstrated  as  already  de- 
scribed ;  a  similar  procedure  is  employed  to  show  the  existence  of  the  amniotic  layer,  which  is 
more  easily  done  than  with  the  other. 

4.  The  vessels  of  the  umbilical  cord  and  placenta  should  be  injected,  and  to  make  an 
injection  penetrate  satisfactorily,  tlie  placental  vessels,  with  the  foetus  and  chorion,  should  be 
placed  in  tepid  water  for  some  time. 

The  annexes  of  the  fcetus   comprise  :    1.  A  membranous  envelope  exactly 

Fig.  554. 


DIAGRAM   OF   THE    FCETAL   MEMBRANES    OF    A    MAMMAL. 

pc.  Zona  pellucida  with  villi,  and  sz,  the  remainder  of  the  extra-embryonal  somatopleure  con- 
stituting the  chorion;  am,  amnion;  AC,  cavity  of  amnion;  UV,  umbilical  vesicle;  al,  allantois; 
ALC,  cavity  of  the  allantois ;  e,  ectoderm,  or  outer  layer  of  the  embryo  (epiblast) ;  m,  mesoblast 
(or  middle  layer) ;  H,  endoderm  of  the  embryo  (alimentary  canal). 

moulded  on  the  uterus,  and  known  as  the  chorion.  2.  A  second  ovoid  sac  in- 
cluded in  the  first,  and  containing  the  foetus — the  amnion.  3.  The  allantois— o. 
membrane  formed  of  two  layers  spread  over  the  inner  surface  of  the  chorion 
and  the  external  face  of  the  amnion,  as  well  as  covering  the  parts  between  these 
two  envelopes.  4.  A  small  pyriform  bladder  constituting  the  umbilical  vesicle. 
5.  The  placenta — a  collection  of  vascular  tufts  which  graft  the  young  creature 
to  the  mother.     6.  The  umbilical  cordy  composed  of  vessels  that  attach  the  foetus 


J018  ~^  EMBRYOLOGY. 

to  the  envelopes  sniToundiiig  it,  and  which  ramify  in  the  placental  tufts  (Fig. 
556). 

1.  The  Chorion  (Figs.  554,  555). 

The  outermost  envelope  of  the  ovum,  the  chorion  is  a  vast  membranous  and 
perfectly  closed  sac,  the  shape  of  which  exactly  corresponds  with  that  of  the  uterus. 
It  has  a  hodij  and  two  cornua.  The  latter,  when  inflated,  are  plicated  and 
sacculated  like  the  caecum,  and  are  always  unequal  in  volume — that  in  which 
the  foetus  is  developed  having  by  far  the  largest  dimensions.^ 

The  external  face  is  studded  with  small  red  tubercles,  formed  by  the  placental 
tufts.  It  adheres  to  the  internal  surface  of  the  uterus.  Between  the  two 
membranes  there  is  found  a  small  quantity  of  sanguinolent  fluid ;  but  on  one 
occasion,  in  the  Ass,  it  had  the  appearance  of  milk. 

The  internal  face,  lined  by  the  external  layer  of  the  allantois,  is  united  in 
the  closest  manner  to  that  membrane,  except  at  the  umbilical  cord,  where  there 


Fie.  555 


EXTERIOR  OF  THE  CHORIAL  SAC  (MARE). 

A,  Body ;  B,  C,  cornua. 

exists  a  kind  of  conical  infundibulum  occupied  by  the  umbilical  vesicle.  Ad- 
hesion is  established  by  means  of  the  vessels  of  the  umbilical  cord  passing  into 
the  texture  of  the  chorion,  and  by  very  delicate,  laminal,  interannexial  connective 
tissue. 

Structure  and  Development. — The  external  covering  of  the  ovum  is  at 
first  formed  by  the  vitelline  tunic,  itself  constituted  by  the  transparent  membrane, 
covered  externally  by  a  layer  of  cells  derived  from  the  Fallopian  tube  or  uterus. 
This  primitive  chorion  is  replaced  by  a  portion  of  the  extra-foetal  somatopleure, 
which  becomes  the  secondary  or  definitive  chorion.  It  is  destitute  of  vessels  until 
the  allantois  is  developed. 

When  the  chorion  is  complete,  it  is  composed  of  three  layers  :  1.  An  external 
epithelial  covering,  formed  of  a  single  layer  of  uniform  cylindrical  cells,  contain- 

'  When  there  is  only  one  foetus,  it  is  always  more  particularly  developed  in  one  comu, 
which  consequently  has  an  enormous  volume  when  compared  with  the  other.  When  there 
are  two  foetuses— as  often  happens  in  the  Ewe — there  is  one  in  each  cornu;  and  then  the 
cornua  develop  in  the  same  manner. 


THE  FCETUS.  1019 

ing  at  some  points  fat-granules.  2.  A  chorial  stroma  of  embiyonic  connective 
tissue — fibres,  stellate  cells,  and  round  and  migratory  cells  in  the  midst  of  a 
large  quantity  of  albuminous  fluid.  Dastre  has  observed  in  this  layer  opaque 
plates — chorial  plates — composed  of  irregular  particles  of  tribasic  phosphate  of 
lime,  which  ultimately  serves  for  the  ossification  of  the  foetal  cartilages.  The 
chorial  deposit  in  Solipeds  has  the  appearance  of  a  network,  the  meshes  and 
spaces  in  which  are  badly  defined.  3.  A  layer  of  mucous  connective  tissue  that 
unites  it  to  the  allantois. 

From  this  description,  it  will  be  seen  that  the  chorion  does  not  play  a  merely 
mechanical  part  in  protecting  the  foetus  and  supporting  the  placental  blood- 
vessels, but  that  it  holds  in  reserve  the  materials  that  will  serve  for  rapid 
nutritive  changes  at  a  given  moment. 

2.  The  Amxion  (Figs.  556,  A  ;  557,  C). 

The  second  sac  enveloping  the  foetus — the  amnion — floates  freely  in  the  interior 
of  the  chorion,  to  which  it  is  only  united  at  one  point  through  the  medium  of 
the  umbilical  cord.  It  contains  the  young  creature,  which  is  also  attached  to 
its  inner  face  by  the  vessels  of  the  cord.  It  has  the  shape  of  an  ovoid  pouch 
depressed  around  the  umbilical  vessels,  around  which  it  forms  a  sheath  as  it  goes 
to  be  confounded  with  the  skin  of  the  foetus.     It  has  thin  transparent  walls. 

Its  external  face  is  covered  by  the  inner  layer  of  the  allantois,  to  which  it 
adheres  slightly.  A  large  number  of  flexuous  vessels,  enveloped  by  a  thick  layer 
of  mucous  tissue,  course  over  this  surface.  The  internal  face  is  perfectly  smooth, 
and  is  applied  more  or  less  directly  to  the  skin  of  the  foetus.  It  exhales  a  fluid 
in  which  the  latter  floats — the  liquor  amnii. 

Structure. — As  the  amnion  is  derived,  hke  the  chorion,  from  the  somato- 
pleure,  it  is  not  surprising  to  find  in  it  three  superposed  layers  :  1.  A  very  thin 
connective-tissue  membrane  that  adheres  to  the  allantois.  2.  A  proper  membrane 
— also  of  connective  tissue — but  containing  some  muscular  fibres,  which  explains 
the  contration  of  the  amnion  observed  in  the  chick.  3.  An  epithelial  lamina 
lining  the  latter.  There  are  sometimes  met  with,  at  certain  points  on  the  inner 
surface  of  the  amnion,  small,  white,  opaque  masses,  composed  of  glycogenic  ceUs, 
which  become  brown  when  treated  with  iodine. 

Liquor  amnii. — Enclosed  with  the  foetus  in  the  cavity  of  the  amnion,  this 
fluid  is  more  or  less  abundant,  according  to  the  period  of  gestation  ;  its  relative 
quantity  being  always  less  as  the  foetus  is  advanced  in  development.  At  an 
early  period  it  is  somewhat  milky  in  appearance,  but  later  it  assumes  a  citrine  or 
slightly  reddish  tint.  It  has  a  salt  taste,  and  contains  99  per  cent,  of  water, 
with  albumen  and  salts,  the  principal  of  which  are  chloride  of  sodium  and  the 
sulphate  and  phosphate  of  lime. 

3.  The  Allantois  (Fig.  556). 

The  allantois  is  a  membrane  that  covers  the  inner  face  of  the  chorion,  and 
is  folded  around  the  insertion  of  the  umbilical  cord,  to  spread  itself  over  the 
whole  external  surface  of  the  amnion.  It  thus  transforms  the  chorial  sac  into 
a  kind  of  serous  cavity,  in  which  the  amnios  is  enclosed  as  a  viscus. 

The  inner,  or  amniotic  lamina,  is  attached  to  the  amnion  "  so  shghtly,  that 
dissection,  and  especially  insufflation,  easily  destroys  its  adhesion.  When  the 
second  of  these  measures  is  resorted  to,  in  order  to  separate  the  two  membranes. 


1020 


EMBRYOLOGY. 


the  allantoid  surface  assumes  a  sacculated  or  blistered  appearance,  due  to  the 
numerous  cellular  bands  that  attach  it  to  the  amnion.  These  bands  rupture 
when  the  inflation  is  forced,  and  a  noise  is  heard  analogous  to  that  produced  by 
the  rumpling  of  parchment.  With  a  little  care,  the  whole  of  this  portion  of 
the  allaiitois — the  extent  of  which  equals  that  of  the  amnion — may  be  entirely 
detached. 

"  The  degree  of  adhesion  of  the  chorial  allantois  is  more  marked.  Ordinary 
dissection — which  is  easy  along  the  first  divisions  of  the  cord — is  much  more 
difficult  towards  the  chorion,  and  soon  becomes,  if  not  impossible,  at  least  very 
arduous,  if  we  desire  to  separate  it.  But  here,  again,  inflation  demonstrates  the 
existence  of  the  membrane,  and  its  continuity  with  the  portion  so  easily  dissected 
from  the  amnion.     If,  after  opening  the  allantoid  sac  by  cutting  through  the 


DIAGRAM    OF   THE  DIFFERENT  PARTS  OF  THE   FCETAL  HORSE,  TOWARDS  THE  MIDDLE  OP    GESTATIOIT. 

P  P,  Placenta ;  Ch  Ch,  chorion  ;  Al',  external  lamina  of  the  allantois ;  Al,  internal  lamina  of 
ditto  ;  o,  urachus;  e,  cavity  of  the  allantoid  ;  A,  amnion  ;  B,  cavity  of  the  amnion;  Vo,  remains 
of  the  umbilical  vesicle  ;  V,  vessels  of  the  umbilical  cord  ;  F,  foetus. 


chorion  and  the  lamina  lining  it,  a  tube  is  introduced  between  the  two  membranes 
— which  is  readily  done  near  a  large  vessel — by  a  slight  inflation  the  air  enters 
between  the  allantois  and  chorion,  though  it  only  follows  the  track  of  vessels  of 
a  certain  size,  to  the  sides  of  which  there  is  but  little  adherence.  If  the  inflation 
is  pushed,  the  air — following  the  smallest  vascular  ramifications— renders  the 
membrane  more  apparent,  though  without  detaching  it  from  the  points  where 
the  vessels  have  almost  become  capillaries. 

"  If,  instead  of  injecting  the  air  towards  the  ramifications,  it  is  propelled  in 
the  opposite  direction,  it  will  soon  be  perceived  to  extend  towards  the  allantoid 
portion  of  the  umbilical  cord,  and  insinuate  itself  between  the  amnion  and  the 
allantois  covering  it — an  evident  proof  of  the  continuity  of  the  two  layers  which 


THE  F(ETUS.  1021 

have  been  separated  for  the  purpose  ot  studying  them,  but  which  are,  in  reaUty, 
only  two  portions  of  the  same  membrane  that  forms  a  complete  sac."  ^ 

The  cavity  of  this  sac  communicates  with  the  bladder  by  means  of  a  canal 
divisible  into  two  portions  :  1.  The  infutuUbulum — a  wide  canal  continued  in 
the  amniotic  portion  of  the  umbiUcal  cord,  the  walls  of  which  are  continuous,  on 
the  one  part,  with  the  amniotic  lamina  of  the  membrane,  and  on  the  other  part 
with  the  chorial  lamina,  after  being  prolonged  as  a  sheath  around  the  cord. 
2.  The  urachus,  a  musculo-membranous  canal  that  extends  from  the  umbilicus 
to  the  summit  of  the  bladder,  with  the  umbihcal  arteries  on  each  side  (Figs.  556  ; 
557,  A  B). 

Structure  and  Development. — The  allantois  has  the  structure  of  a  serous 
membrane.  It  possesses  :  1.  An  endothelial  lining,  the  cells  of  which  are  thin 
and  polygonal,  leaving  between  them,  here  and  there,  stomata  that  permit  the 
blood-serum  to  transude  through  its  texture  ;  these  cells  contain  the  glycogen. 
2.  A  middle  layer  or  stroma,  of  the  nature  of  connective  tissue,  little  vascular, 
and  the  fibres  of  which  are  parallel.  3.  An  external  layer  of  loose  connective 
tissue,  rich  in  vessels,  and  resembling  subserous  tissue  ;  this  layer  is  continuous 
with  the  parietal  fibrous  tissue  of  the  foetal  peritoneum,  through  the  medium  of 
Wharton's  jelly. 

The  allantois,  as  we  have  described  it,  passes  beneath  the  mucous  membrane 
of  the  bladder  instead  of  being  confounded  with  it. 

The  blastodermic  laminae — internal  and  middle — concur  in  the  formation  of 
the  allantois  ;  but  the  middle  one  has  the  largest  share  in  this.  There  is  a 
tendency  to  beHeve  that  the  extra-foetal  portion  of  this  vesicle  is  a  cavity  formed 
in  the  intra-annexial  connective  tissue,  and  that  this  cavity  is  at  a  later  period 
transformed  into  a  serous  one.  In  any  case,  it  serves  as  a  support  to  the  vessels 
passing  between  the  foetus  and  placenta. 

Allantoid  Fluid. — This  cavity  contains  a  fluid,  the  quantity  of  which 
increases  with  age.  Colourless  and  transparent  at  first,  it  afterwards  becomes 
amber-tinted,  and  this  gradually  deepens  ;  at  the  same  time  it  grows  turbid,  and 
flocculent  masses  form  in  it.  Its  reaction  is  alkaline,  and  it  has  the  property  of 
emulsifying  fats.  It  contains  albumen,  urea,  various  salts,  and  sugar — 2*5  per 
1000  average.  The  proportion  of  the  latter  does  not  vary  much  during 
gestation. 

The  presence  of  urea  in  this  fluid,  as  well  as  the  communication  of  the  urachus 
with  the  bladder,  has  led  to  the  supposition  that  the  urinary  secretion  of  the 
foetus  contributes  to  its  formation.  But  this  is  not  demonstrated,  and  the  mere 
presence  of  urea  is  not  sufficient  to  attribute  this  origin  to  the  allantoid  fluid  ; 
for  the  blood,  lymph,  cerebro-spinal  fluid,  as  well  as  all  other  serous  fluids,  contain 
a  proportion  at  least  as  considerable. 

Hippomanes. — This  name  is  given  to  small  brown  masses,  more  or  less 
numerous — though  often  there  is  only  one — which  float  in  the  allantoid  fluid. 
"These  bodies,  of  the  consistency  of  gluten,  and  elastic  like  it,  are  flattened, 
thinner  at  the  borders  than  towards  the  centre,  oval  or  irregularly  circular,  and 
about  the  diameter  of  a  five-franc  piece.  It  is  difficult  to  explain  the  presence  of 
the  hippomanes  in  the  allantoid  sac.  Nothing  in  its  appearance  indicates  that  it 
may  be  formed  at  the  expense  of  the  liquid  contained  in  this  membrane.  Some- 
times pediculated  hippomanes  are  found,  and  these  may  assist  in  explaining  the 
formation  of  the  free  hippomanes.     Bourgelat  speaks,  in  his  Anatomic,  of  pedicu- 

•  F.  Lecoq,  Bes  Annexes  du  Foetus. 
67 


1022 


EMBRYOLOGY. 


lated  hippomanes,  and  I  have  been  able  to  make  the  following  observationB, 
through  having  met  with  a  large  number  on  a  foetus  : — 

"  Besides  the  free  hippomanes  found  floating  in  the  allantoid  fluid,  there  were 
remarked,  on  the  outer  wall  of  the  sac,  a  great  number  of  small  tear-shaped  bodies 
of  variable  size,  adhering  by  a  pedicle  which  was  more  or  less  narrow  as  the  mass 
was  more  developed.  Their  colour  was  the  same  as  that  of  the  principal  hippo- 
manes, and  if  pressed  between  the  fingers,  the  brown  matter  contained  in  a  thin- 
Fig.  557. 


FCETUS   OF    THE    MARE,    WITH    ITS    ENVELOPES. 

,  Chorion;  (7,  amnion  removed  from  the  allantoid  cavity,  and  opened  to  expose  the  foetus;  2), 
infundibulum  of  the  urachus;  B,  allantoid  portion  of  the  umbilical  cord  ;  b,  point  of  the  external 
surfare  of  the  chorion,  destitute  of  placental  villi,  and  corresponding  to  the  part  where  the  three 
pediculated  hippomanes  are  attached. 


walled  sac  escaped  by  the  pedicle,  and  spread  itself  over  the  external  surface  of 
the  chorion.  There  the  villosities  of  the  placenta  were  absent  at  the  margin  of 
the  opening,  which  was  surrounded  by  a  whitish  areola  (Fig.  557,  b). 

"Might  it  not  be  admitted,  from  this  disposition,  that  the  hippomanes  is 
developed  between  the  placenta  and  the  uterus,  and  is  carried  inward,  by  pushing 
before  it  the  chorion  and  layer  of  the  allantois  covering  it,  until,  on  reaching  the 


TEE  FCETUS. 


1023 


allantoid  cavity,  it  becomes  detached,  like  certain  fibrous  or  cartilaginous  bodies 
in  the  synovial  or  serous  cavities  ?  "  (F.  Lecoq). 

According  to  Dastre,  the  hippomanes  arise  between  the  chorion  and  the 
allantois,  and  they  are  formed  by  the  phosphatic  matter  of  the  chorion,  which 
collects  in  masses  at  certain  points,  where  it  is  enveloped  by  a  mass  of  the  sub- 
jacent mucous  connective  substance  of  this  membrane. 


4.  The  Umbilical  Vesicle. 

The  umbilical  vesicle  is  a  small  fusiform  or  pyriform  pouch,  lodged  in  the 
infundibulum  at  the  extremity  of  the  umbilical  cord.  Its  fmidus  adheres  to 
the  chorion  ;  the  opposite  extremity  is  prolonged  to  a  variable  depth  in  the 
substance  of  the  cord,  and  is  even  continued — in  the  very  young  foetus — to  the 
abdominal  cavity,  by  a  narrow  canal  that  communicates  with  the  terminal 
portion  of  the  small  intestine. 

This  pouch  has  a  red  colour,  due  to  its  great  vascularity.  Its  walls  receive  a 
special  artery  derived  from  the  anterior  mesenteric,  its  corresponding  vein  passing 
to  the  portal  vein.     These  are  the  two  omphalo-mesenteric  vessels. 

In  the  last  months  of  foetal  life,  the  umbiUcal  vesicle  is  always  more  or  less 
atrophied  ;  its  cavity  has  disappeared,  and  it  is  nothing  more  than  a  thin  reddish- 
brown  cord.      Its  vessels   also  become 

atrophied  in  the  same  manner,  and  nearly  Fig-  558. 

always  nothing  else  is  found  than  the 
artery,  reduced  to  the  dimensions  of  a 
thread. 


PORTION  OF  THE  ULTIMATE  RAMIFICATIONS 
OF  THE  UMBILICAL  VESSELS,  FORMING  THE 
FCETAL   VILLI   OF   THE   PLACENTA. 


5.  The  Placenta  (Figs.  556,  558,  559). 

The  placenta  is  the  organ  which 
establishes  relations  between  the  foetus 
and  the  uterus  of  the  parent.  It  ad- 
heres to  the  chorion,  of  which  it  is  only 
a  kind  of  dependency. 

In  Solipeds,  the  placenta  is  composed  of  a  multitude  of  small  tubercles 
{placentce),  spread  uniformly  over  the  external  surface  of  the  chorion,  which  they 
almost  completely  cover.  Their  number  and  development  are  greatest  in  the 
middle  portion  of  the  chorion — in  the  zone  where  the  principal  divisions  of  the 
umbilical  cord  lie  beside  this  membrane.  Thence  they  diminish  towards  the  ex- 
tremity of  the  uterine  cornua  and  body.  In  front  of  the  openings  of  the  uterus — 
Fallopian  tubes  and  os  uteri — they  are  rare.  These  small  tubercles  are  formed  by 
an  aggregation  of  extremely  vascular  vilU,  which  implant  themselves  in  the  follicles 
of  the  uterine  mucous  membrane.  The  terminal  ramifications  of  the  vessels  of 
the  cord  constitute  the  vascular  apparatus  of  these  villi  (Figs.  558,  559,  560). 

The  parts  of  the  uterine  mucous  membrane  which  are  related  to  the  foetal 
placentae,  are  named  the  uterine  or  maternal  placentce.  They  are  constituted  by 
follicular  cavities,  which  are  formed  beside  permanent  glandular  follicles  in  the 
mucous  membrane  during  gestation,  but  they  disappear  after  parturition 
(Ercolani). 

This  Italian  anatomist  compared  the  cavities  of  the  maternal  placentae  to 
glands  which  secrete  a  kind  of  uterine  milk.  Laulanie,  from  a  study  of  the 
maternal  placenta  of  the  Guinea-pig — and  which  he  regards  as  a  colossal  multi- 


1024  EMBRYOLOGY. 

nucleated  cell,  the  protoplasm  in  which  is  intersected  by  vessels — is  of  opinion 
that  the  placental  cavities  in  the  Mare  are  of  the  same  character,  except  that 
there  are  several  giant  cells.  There  is  nothing  glandular  in  the  epithelium 
lining  these  cavities  ;  on  the  contrary,  they  are  often  confounded  with  the  cells 
of  the  deeper  part. 

These  cavities  are,  then,  sinuses  lined  with  blood-vessels,  and  are  not  glands. 
Besides,  as  may  be  seen  in  examining  Fig.  559,  they  are  quite  distinct  from  the 
proper  tubular  glands  of  the  uterine  mucous  membrane. 

Structure  and  Development. — The  villi  of  the  placenta  have  for  their 
base  a  tissue  similar  to  that  of  the  chorion,  their  stroma  being  formed  by  bundles 
of  connective  tissue  mixed  with  cells.  They  are  covered  by  a  simple  cylindrical 
epithelium   placed  immediately  on  the  connective  stroma  (Fig.  56oi    Their 


Fig.  559. 


VERTICAL   SECTION    OF   THE    INJECTED    PLACENTA    OF   A   MARE. 

ck,  Chorion,  with  its  villi  partly  m  situ,  partly  torn  out  of  the  uterine  sinuses,  cr ;  g,  uterine 
glands  ;  V,  blood-vessels  ;  E,  epithelium. 

interior  is  occupied  by  a  capillary  network,  the  finest  divisions  of  which  are 
subjacent  to  the  epithelium  ;  the  network  itself  is  supplied  by  a  branch  from  the 
umbilical  arteries,  and  the  blood  is  returned  by  a  vein  nearly  in  the  centre  of 
the  villus. 

The  vessels  pre-exist  in  the  villi ;  consequently,  the  latter  do  not  develop 
from  the  chorial  tissue,  but  rather,  it  might  be  said,  the  chorion  is  pushed  back 
by  the  pressure  of  the  vessels-.  The  placenta  succeeds,  then,  the  development  of 
the  allantois,  the  use  of  which  is  to  convey  the  umbilical  vessels  from  the 
umbilicus  to  the  chorion. 

The  villi  penetrate  the  uterine  mucous  membrane,  in  such  a  way  that  the 
capillary  systems  of  the  mother  and  foetus  are  only  separated  by  the  thin  walls 
of  the  vessels,  and  the  epithelium  of  the  villi  and  follicles. 

The  fusion  of  these  two  systems  has  never  been  observed,  and  all  the  inter- 
changes between  the  female  and  its  young  take  place  through  the  capillaries  by 
osmotic  force  only. 


TEE  FCETUS. 


1025 


6.  The  Umbilical  Coed  (Figs.  556,  557). 

The  cord  is  formed  by  the  vessels  which,  in  the  foetus,  caiTj  the  blood  to  the 
envelopes,  and  chiefly  to  the  placenta.  It  is  divided  into  two  portions — an 
amniotic,  the  longest,  which  is  always  twisted  on  itself  like  a  cord,  and  covered 
externally  by  the  amnion  that  is  prolonged  on  its  surface,  to  be  continued  with 
the  skin  around  the  umbilicus  ;  the  other — the  allantoid  portion  (Fig.  557,  B) — 
much  shorter  and  less  twisted,  is  enveloped  by 
the  sheath  that  continues  the  two  layers  of  the 
allantois,  and  is  inserted  into  the  superior  wall 
of  the  chorion,  between  the  two  cornua.^ 

Three  vessels  compose  the  cord — two  arteries 
and  a  vein;  these  are  covered  by  a  layer  of 
embryonic  tissue — the  gelatine  of  Wharton — 
which  makes  them  appear  much  larger  than 
they  really  are. 

The  Umbilical  Arteeies  ^  arise  from  the 
internal  iliac,  and  pass  along  the  sides  of  the 
bladder  ;  escaping  by  the  umbilicus,  they  arrive 
at  the  terminal  extremity  of  the  amniotic  portion 
of  the  cord,  and  giving  off  some  branches  to 
the  amnion,  they  are  continued  to  the  extremity 

of  the  allantoid  portion,  where  they  end  in  an 
expansion   of    placental   ramifications.      These 

arteries  run  parallel  to  the  median   plane  of 

the  body  of  the  foetus,  to  the  umbilicus  ;  they 

are  perpendicular  at  the  infundibulum,  which 

proves  that  the  allantois  undergoes  a  twist  in 

the  early  period  of  development.     The  amniotic 

divisions  of  these  arteries  are  few,  and  extremely 

flexuous ;  they  are  included  between  the  allantoid 

layer  and  the  amniotic  membrane,  within  which 

they  may  be  seen  projecting. 

The  placental  or  cliorial  divisions — infinitely 

larger  and  more  numerous — leave  the  end  of 

the  cord,  and  pass  in  every  direction  between  the  chorion  and  external  lamina 

of  the  allantois,  beneath  which  they  are  very  prominent.     By  their  anastomoses 

they  form  a  very  rich  network,  from  which  proceed  the  capillary  twigs  that 

enter  the  villosities  of  the  placenta.     Observation  demonstrates  that  these  twigs 

do  not  communicate  with  the  maternal  vessels,  and  that  they  are  continued  by 

venous  radicles,  the  origin  of  the  vessel  now  to  be  described. 

The  Umbilical  Vein  commences  by  these  capillary  radicles  of  the  placental 

villi,  which  unite  between  the  chorion  and  amnion  to  form  a  network  of  more 

voluminous  divisions  and  complexity  than  that  of  the  arteries.     Two  principal 


PORTION  OF  ONE  OF  THE  FOETAlj 
VILLI,  ABOUT  TO  FORM  PART  OP 
THE  PLACENTA  (HIGHLY  MAGNI- 
FIED). 

a,  a,  Its  cell  covering;  6,  6,  6,  its 
looped  vessels;  c,  c,  its  basis  of  con- 
nective tissue. 


'  Goubaux  has  remarked  that  the  relations  between  these  two  portions  are  not  constant. 
In  a  six  months'  foetus,  the  amniotic  part  measured  -40  m.,  and  the  allantoid  part  -24  m.  In  a 
foetus  of  ten  months,  the  first  was  -30  m.  long,  and  the  second  -20  m. 

2  The  -walls  of  the  umbilical  artery  are  very  rich  in  muscular  fibres,  which  are  longitudinal 
and  transversal,  but  are  irregularly  distributed.  There  is  no  internal  elastic  tunic  in  any  of  tha 
branches  external  to  the  umbilicus. 


EMBRYOLOGY. 
Fig,  561. 


FtETUS  OPENED  ON  THE  LEFT  SIDE  TO   SHOW   THE   COURSE  OF  THE    UMBIUCAL    VESSEI;S 
IN   THE    BODY. 


A,  Umbilical  cord ;  B,  umbilical  vein ; 
6,  spleen  ;  H,  liver  ;  /,  intestine  ; 
arteriosus  ;  N,  thymus  gland. 


C,  umbilical  artery;   £>,  bladder;   ^.testicle;   J",  kidney; 
/,  lung;    K,   heart;    L,   pulmonary    artery;    if,  ductus 

Fig.  562. 


BIX)OD-VESSELS   IN   THE    LIVER    OF   AN    EQUINE    F<ETUS   AT   MID-TERM. 

A   Umbilical  vein;  B,  its  anastomoses  with  the  portal  vein,  C]  D,  ductus  venosus;  E,  posterior 

rena  cava. 


THE  FCETUS. 


1027 


Fig.  563. 


branches  are,  finally,  the  result  of  the  coalescing ;  and  these  soon  unite  into  a 
single  trunk,  which  accompanies  the  two  arteries  in  the  cord.  On  reaching  the 
umbilicus,  this,  the  umbilical  vein  (Fig,  561),  bends  forward  on  the  inner  face  of 
the  abdominal  parietes,  where  it 
is  covered  by  the  peritoneum, 
and  arrives  at  the  liver,  into 
which  it  enters  and  opens  di- 
rectly into  the  vena  portae  ;  the 
junction  of  the  two  vessels 
giving  rise  to  a  single  canal, 
from  which  proceed  the  sub- 
lobular  veins  (Fig.  562).  In 
other  animals  than  Solipeds,  this 
single  vessel  gives  off  a  par- 
ticular trunk  of  somewhat  con- 
siderable volume,  which  passes 
directly  to  the  posterior  vena 
cava,  and  forms  what  is  named 
the  ductus  venosus  of  Arantius 
(Figs.  562,  563). 

Such    are     the    umbilical 
vessels,  and  it  will  be  seen  that  they  form  a  part  of  the  circulatory  system  of 
the  young  creature,  which  will  be  more  completely  studied  hereafter. 


LIVER   OF    A    LAMB    AT    BIRTH. 

,  Posterior  vena  cava ;  B,  vena  porta ;  C,  umbilical 
vein;  Z),  anastomosis  of  the  umbilical  vein  with  the 
vena  portae. 


Differential  Characters  in  the  Annexes  of  the  Fcetus  of  the  other  Animals. 

1.  Rdminants. — Placenta. — The  placental  apparatus  of  the  Cow  is  not  uniformly  spread 
over  the  outer  surface  of  the  chorion,  but  is  constituted  by  a  variable  number  of  vascular 
bodies— about  sixty  on  an  average — disseminated  here  and  there,  and  dovetailed  by  reciprocal 
penetration  of  prominences  and  cavities,  into  analogous  bodies  on  the  inner  surface  of  the 
uterus,  designated  cotyledons.  These  are  only  thickened  points  of  the  mucous  membrane,  the 
follicles  of  which  are  enormously  enlarged.  They  exist,  we  have  seen,  before  gestation  ;  but 
observation  demonstrates  that  they  may  be  afterwards  formed  or  entirely  renewed,  especially 
in  those  cases  in  which  accidental  circumstances  have  rendered  those  present  insufficient  for 
their  oflSce.  The  largest  are  found  in  the  body  of  the  uterus  ;  in  the  cornua  they  are  smaller 
as  they  are  nearer  the  extremity.  Their  form  i&  generally  elliptical,  and  they  are  attached  to 
the  uterine  surface  by  a  wide  mucous  peilicle;  their  surface  is  convex,  and  perforated  by 
numerous  openings,  into  which  the  placental  tufts  pass.  They  have  always  a  yellowish 
colour,  which,  added  to  their  external  characteristics,  gives  them  the  appearance  of  a  moril 
mushroom. 

With  regard  to  the  placentie,  they  repeat,  on  the  surface  of  the  chorion,  the  disposition  of 
the  cotyledons  on  the  uterus.  They  are  vascular,  concave  patches,  closely  embracing  the 
cotyledous,  and  showing  on  their  surface  a  multitude  of  long  ramifying  papillae,  which  bury 
themselves  in  the  cotyledonal  cavities.  They  are  attached  to  the  chorion  by  a  very  thick, 
short,  vascular  pedicle. 

In  the  Sheep  and  Goat,  the  arrangement  is  the  same,  except  that  the  cotyledons  are 
hollowed  out  in  their  centre,  like  a  cup,  and  into  this  cavity  the  placentae  are  inserted  (Fig.  565) 

Chorion. — The  primary  chorion  disappears  at  the  same  time  that  the  amnion  is  formed,  and 
it  is  completely  replaced  by  the  definitive  chorion  towards  the  twentieth  day,  in  tlie  foetus  of 
the  Sheep.  The  general  form  of  this  sac  is  an  exact  repetition  of  that  of  the  uterine  cavity. 
This  membrane  responds  to  the  inner  face  of  the  uterus,  in  the  iuterplacental  points.  These 
points  constitute  the  chorion  (or  decidua)  serotina,  and  the  part  carrying  the  placentae  is  named 
the  chorion  frondosum.  The  inner  face  of  the  chorion  is  united  to  the  amnion  and  the  allaatoia 
by  means  of  inter-annexial  laminated  tissue. 

Allantois. — Very  diflerent  from  that  of  the  Mare,  and  otherwise  much  less  complicated, 
the  allantois  of  Ruminants  is  a  very  elongated  cavity,  the  middle  portion  of  which  receives 
the  insertion  of  the  urachus,  and  its  extremities  are  prolonged  into  the  two  cornua  of  the 


1028  EMBRYOLOGY. 

chorion.  This  sac,  which  is  an  expansion  of  the  urachus,  is  always  reversed  on  one  of  the 
sides  of  tlie  amnion  ;  its  two  braiicbes  are  sacculated  on  their  surface  like  the  large  intestine 
ami  the  greatest  forms  a  cul-de.  sac.  or  conical  diverticulum.  * 

The  extremities  of  the  allantoid  coraua  appear  to  have  pierced  the  cliorion  ;  they  form  a 
point  covered  with  a  yellow,  mucus  substance,  and  separated  from  the  rest  of  the  membrane 
by  a  circular  constricticu.  This  part  is  beneath  the  chorion,  like  the  remainder  of  the 
membrane,  only  the  vessels  do  not  extend  beyond  the  constriction ;  so  that  the  elements  of 
the  chorion  and  allantois  here  undergo  a  kind  of  murtiticati(jn.  The  allantoid  infundibulum 
is  encircled  by  a  vascular  network  that  accompanies  it  throughout  tue  umbilical  cord. 

The  epithelium  of  the  allantois  is  every  wliere  colourable  by  iodine  reagents,  in  Kuniiuants. 
At  times  the  hippomanes  is  Ibund  floating  in  the  liquid  it  contains. 

Jmntow.— Altogether  like  that  of  Solipeds,  tiiis  membrane  is  readily  resolved  into  two 


Fig.  564. 


FCETUS   OP   THE   SHEEP,    FREED   FROM    ITS   CONNECTION    WITH   THE    UTERUS. 

AL  AL,  Allantois  slightly  inflated,  seen  beneath  the  chorion ;  Am  Am  Am,  amnion  slightly  dis- 
tended with  fluid  underneath  the  chorioa  ;  P,  P,  P,  placentae  on  the  surface  of  the  chorion  ;  C, 
umbilical  chord  ;  al,  al,  extremities  of  the  allantoidean  cornua,  looking  as  if  protruding  through 
the  chorion. 


laminae,  and  presents  on  its  inner  surface  a  great  number  of  little,  yellowisii-white,  epidermic 
patches,  more  especially  visible  on  the  amniotic  covering  of  the  cord.  The  epithelium  is  only 
stained  by  iodine  at  these  patches,  or  villi.  These  productions  are  surrounded  at  their  base 
by  a  girdle  of  glycogenic  cells.  In  the  foetus  of  the  Cow,  at  a  late  stage  of  gestation,  the 
amniotic  fluid  is  not  abundant,  and  becomes  white  and  viscid ;  in  one  instance  we  found  it 
stringy,  like  a  solution  of  gelatine. 

Umbilical  cord. — This  comprises  two  arteries  and  two  veins ;  the  latter  forming  one  trunk 
on  their  entering  the  abdomen.  To  reach  the  chorion,  tiiese  vessels  only  traverse  the  amniotic 
cavity.  Tliey  are  accompanied  by  tlie  urachus,  which  at  their  extremity  presents  the  dilatation 
that  results  in  the  allantoid  sac. 

Unihilical  vesicle. — This  pouch  disappears  at  an  early  period,  and  not  a  vestige  of  it  is  to  be 
found  after  the  formation  of  the  abdominal  parietes. 


TEE  FCETUS.  1029 

2.  Pig.— The  placenta  is  formed  by  an  expansion  of  the  villous  tubercles,  as  in  Solipeds. 
The  chorion  is  not  entirely  covered  by  these  tubercles,  but  here  and  there  it  shows  bright  little 
patches,  where  its  tissue  is  merely  covered  by  an  epithelial  layer ;  it  is  also  glabrous  at  those 
points  wliere  it  is  in  cont:ict  with  the  chorion  of  neighbouring  foetuses. 

The  chorion  has  not  a  body  and  two  coruua,  but  is  merely  an  elongated  sac,  the  two 
extremities  of  which  are  in  relation  with  the  adjacent  foetuses.  The  inner  face  corresponds, 
as  in  Ruminants,  with  the  amnion  and  allantois.  The  latter  is  the  same  as  in  the  Cow,  tliough 
it  is  very  much  shorter ;  the  inner  covering  of  this  membrane  contains  the  glycogenic  matter, 
but  that  of  the  amnion  has  none. 

The  umbilical  vesicle,  amnion,  and  cord,  are  also  the  same  as  in  Ruminants. 

3.  Carnivora.— Tlie  placenta  is  a  thick  gir<lle,  surrounding  the  middle  portion  of  the 
chorion.  It  has  a  Uvid  colour  in  its  middle,  green  on  its  borders.  When  the  green-coloured 
matter  is  isolated,  and  treated  with  alcohol  and  chloroform,  then  submitted  to  certain  reagents, 
it  appears  to  be  identical  with  the  colouring  matter  of  the  bile,  and  derived,  as  that  is,  from 
the  haemoglobin  of  tlie  blood. 

The  allantois  is  disposed,  in  principle,  as  in  Solipeds. 

The  chorion  is  quite  like  that  of  the  Pig  with  regard  to  form,  but  it  is  diflferent  with  regard 


Fig.  565. 


SEMI-DIAGRAMMATIC   VERTICAL  SECTION   OF   A   MATERNAL   COTVLEDOX   OF   THE   SHEEP. 

(^cr,  Uterine  sinus;  e,  epithelial  lining  of  the  sinus;  V,  veins,  and  c,  flexuous  arteries  of  the  sub- 
epithelial connective  tissue. 


to  structure,  as  it  hac  no  chora  plates  v/ith  mineral  granules.  Nothing  is  known  as  to  the 
organ  which  fulfils  the  function  of  these  deposits. 

The  umbilical  vesicle— yfhidi  remains  VQvy  developed  at  all  periods  of  foetal  life — resembles 
in  shape  the  allantois  of  the  Pig,  being  a  transversely  elongated  sac  included  between  the 
amnion  and  the  inner  allantoid  lamina,  and  provided  at  its  middle  portion  with  a  narrow 
pedicle,  which  is  prolonged  into  the  umbilical  cord ;  its  walls  are  extremely  vascular. 

•The  amnion  is  lined,  internally,  by  the  inner  lamina  of  the  allantois. 

The  umbilical  cord  has,  as  in  Solipeds,  an  allantoid  portion;  but  it  is  extremely  short,  and 
enveloped  in  a  wide  fold  of  the  allantois. 

Results.— The  comparative  examination  of  the  disposition  of  the  placenta  may  furnish 
valuable  indications  as  to  the  procedure  to  be  adopted  in  practising  artificial  delivery;  as  the 
surgical  manoeuvres  should  necessarily  vary  with  the  extent  and  disposition  of  the  points  of 
union  existing  between  the  uterus  and  the  foetal  envelopes. 

With  this  practical  object  in  view,  we  believe  that  it  is  useful  to  divide  the  ilomesticated 
animals  into  two  groups  :  those  which  have  a  simple,  and  those  which  have  a  multiple  placenta. 
The  first  group  may  be  subdivided,  according  as  the  simple  placenta  is  general  or  local. 


1030  EMBRYOLOGY. 

This  division  is  summed  up  in  the  following  table  : — 

I_,._  (  Mare. 

Diffuse <  g 
Local  and  circular    .  |  ^' ^  ' 
I  Oat. 

,,,,.,      ,        ^     (  Convex  cotyledons    .      oi.    ' 
Multiple  placenta  |  Concave  cotyledons  .      f'^ 

[   (jrOitt. 

Comparison  of  the  Annexes  of  the  Human  Fcetds  with  those  of  Animals. 

The  human  foetus,  like  that  of  the  domesticated  Mammals,  is  enveloped  by  an  amnion  and 
chorion,  which  are  generally  identical  in  disposition  with  those  already  described.  The  umbilical 
vesicle  submits  to  the  same  change  as  in  the  Mare,  becoming  so  quickly  atrophied  that  scarcely 
any  traces  of  it  can  be  found  at  birth.  It  is  impossible  to  isolate  the  aUantois  from  the  inner 
face  of  the  amnion  and  chorion  ;  so  that  some  anatomists  only  admit  its  presence  by  analogy 
witli  what  is  observed  in  animals. 

The  umbilical  cord  offers  nothing  particular.  The  placenta  is  circular ;  its  diameter  at  the 
termination  of  pregnancy  being  from  6  to  8  inches,  and  its  thickness  from  1  to  H  inch.  There 
is  distinguished  the  foetal  placenta,  to  the  midst  of  which  the  umbilical  cord  reaches;  and  the 
maternal  placenta,  the  villi  of  which  dovetail  with  those  of  the  former. 

The  insertion  of  the  placenta  takes  place  towards  the  fundus  of  the  uterus,  near  one  of  the 
Fallopian  tubes.  When  there  are  more  than  one  foetus,  there  is  a  corresponding  number  of 
placentas. 

Independently  of  those  annexes — which  are  the  same  in  all — there  is  described  for  the 
human  foetus  a  special  envelope,  external  to  the  chorion — this  is  the  membrana  decidua.  This 
is  formed  by  the  hypertrophied  mucous  membrane,  which  is  doubled  around  tlie  ovum,  when 
the  latter  is  lodged  in  the  uterine  cavity.  Consequently,  there  results  the  division  of  the 
decidua  into  two  parts— the  true  decidua  (decidua  vera)  which  covers  the  uterus,  and  the 
reflected  decidua  (decidua  reflexa)  which  envelops  the  chorion.  These  present  the  characters 
of  the  hypertropliied  uterine  mucous  membrane. 


CHAPTER  III. 

DEVELOPMENT   OF  THE   FCETUS. 

In  the  two  preceding  chapters,  we  have  seen  how  the  fecundated  ovum  is  modified 
to  furnish  the  earliest  lineaments  of  the  foetus  and  the  organs  annexed  to  it ; 
this  chapter  will  be  deveted  to  an  examination  of  the  manner  in  which  the  foetus 
is  developed,  though  this  subject  more  properly  belongs  to  physiology. 

The  young  creature  is  designated  an  embryo  during  the  early  period  of  gesta- 
tion, before  it  has  assumed  any  definite  shape  ;  but  as  soon  as  it  exhibits  the 
form  of  the  species  to  which  it  belongs — and  particularly  when  the  placental 
circulation  is  established — it  is  named /a^ws. 

Grurlt  has  divided  the  duration  of  gestation  into  seven  periods,  the  length 
of  which  varies  according  to  the  species.  He  has  also  measured  the  dimensions 
of  the  ovum,  the  embryo,  and  the  foetus  of  each  of  them.  We  may,  therefore, 
accept  the  figures  he  has  given  in  order  to  learn  the  age  of  the  foetus.  They  are 
shown  in  the  two  following  tables  : — 


THE  FCETUS. 


1081 


^^ 

M 

1 

week, 
h  wei  k 

h  week 

week. 

th  an.l 
ks. 

1 

'H-s     -s 

■S      £  ® 

— 

:5§    § 

.a    s  ^ 

B 

Hfa      fa 

CC       OQ 

;z; 

ja     4= 

M       J3 

ja 

week 
to   t 

to    t 

s    s 

s 

1 

fourth 
fourth 

ek 
sixth 

eek 

eighth 
ek 

levent 
week 

II 

rd  and 
m   the 
xtli  we 
m    the 
ghth  w 

m  the 
nth  we 
m  the  fc 
fteenth 

a  s 

1=  £«  2  « 

2-  P« 

2  S 

Hfa      fa 

fa     fa 

fa 

^      35 

®           03 

3 

th  week 
li    to    t 

eventh 
and   nin 

H 

th   to 
•ek 

enth  to 
eek 

II 

2 

^ 

jtc  5      .a 

g^l^ 

s« 

g 

5 

o 

[lird  and 
rom    the 
seventh 
rom     the 
the   eigl 
weeks 
rom    the 
thirti^ent 
rom  the  t 
eighteen 

^1 

Hfa      fa 

fa     fa 

fa 

^      ^ 

rom    tlie    thirteenth    to 
the  twentieth  week 
rom   the   twenty-eighth 
to     the     thirty -second 

s 

1 

hird  and  fourth  week 
rom    the    ^Ith    to    t 

eighth  week 
rom    the    ninth   to   t 

twelfth  week 

T-2 

ill 

EHfa       fa 

fa     fa 

fa 

2       2 

S^Sj, 

c 

II 

i 
1 

fourth  week 
fifth    to    t 

eek 
ninth    to   t 

hweek 

fourteenth 
ty-second  we 
wenty-tliird 
y-fourth  wee 

hird  and 
rom    the 

eighth  w 
rom    the 

thirteent 

the 
twen 
the  t 
thirt 

II 

i^  i-S 

C    03 
1- 

Hfa      fa 

fa    fa 

fa 

^ 

• 

ill  1 

i  i 

fe!»H        fa 

fa       CB 

:k 

Ills 


i  a  a^ 

i  a  35 

'  lO  05  CO 
I  CO  »  ■*! 


:i  a  a  i  I  i 

o  a  a  s  °  "" 

o  '*«  ^  »  53  sn 
i-i  CO  03  rt  CC  •*! 


a  fi  a  a  a  a 
X  iaa  aa 

g    «0500N 

V  X  ■*  oa  «o  -H 


CC  -^  W  iO  »o  — 
f-  O  rt  ?^  -X  -H 


faajHfafaoQcc 


1032 


EMBRYOLOGY. 


The  following  are  the  weights  of  the  completely  developed  foetuses. 
The  iveight  of  the  foetus  of  the  Mare,  at  birth,  varies  according  to  breed.     It 
has  been  found  to  be  35  pounds  in  a  Corsican  Mare,  and  135  pounds  in  a  Suflfolk- 
Boulonnaise  Mare  ;  and  between  these  extremes  are  many  intermediate  weights. 
In  Cattle,  the  weight  of  the  Calf  is,  on  an  average,  2*31  parts  that  of  the  Cow. 
According  to   Leuckart,  the  weight  of  the   Puppy  at  birth  is  about  one 
pound  ;  that  of  the  Lamb,  ten  or  eleven  pounds ; 
that  of  the  Pig,  five  pounds  ;  that  of  the  Chick, 
about  one  and  a  half  ounce. 

The  transition  between  the  embryonic  and  the 
foetal  condition  being  inappreciable,  we  will  study 
the  first  phases  of  development  under  the  heading 
of  formation  of  the  embryo,  and  the  last  under 
that  of  the  development  of  organs. 

Article  I. — Formation  of  the  Embryo. 

When  the  embryo  has  assumed  the  form  of  an 
elongated  streak,  and  shows  in  its  centre  the 
primitive  groove,  there  appear  in  the  middle 
lamina  of  the  blastoderm  the  chorda  dorsalis,  the 
vertebral  lamince,  and  the  lateral  lamince,. 

Development  of  the  Chorda  Dorsalis  and 
Vertebral  Laminae. 

The  chorda  dorsalis  is  a  cylindrical  cord, 
slightly  attenuated  at  both  extremities,  which  is 
developed  beneath  the  primitive  groove.  On  its 
sides  is  a  series  of  small,  opaque,  quadrangular 
masses — the  vertebral  /«mw««— which  are  nothing 
more  than  the  jjrotovertebrce,  or  first  traces  of  the 
foetal  vertebrae.  They  appear  in  the  embryo,  on 
each  side  of  the  neural  axis,  in  the  form  of  dark 
quadrilateral  spots,  and  are  developed  in  a  series 
in  the  spinal  zone. 

They  are  hollowed  by  a  central  cavity,  to- 
wards which  converge  a  radial  series  of  cells.     On 
their  lateral  surfaces  they  are  continuous  with  the 
musculo-cutaneous  and  fibro-intestinal  lamina,  by 
means  of  an  intermediate  part — the  intermediate  cellular  lamina. 

At  the  third  day  they  give  rise,  by  differentiation,  to  the  muscular  lamincB 
(Fig.  567,  m.s.).  The  protovertebrse  afterwards  become  fused,  and  invest  all  the 
neural  tube  and  the  chorda  dorsalis  ;  and  it  is  in  this  homogeneous  matrix  that 
an  ulterior  segmentation  marks  the  traces  of  the  definitive  vertebrae.  The  articular 
intervals  in  the  latter  correspond  to  the  middle  portion  of  the  proto-vertebrae. 

The  muscidar  lamince,  in  augmenting  in  volume,  are  inflected  upwards,  and 
unite  in  the  middle  line  of  the  back.  They  form,  in  great  part,  the  muscles  of 
the  vertebral  furrows  ;  they  also  give  off,  below,  prolongations  which  concur  in 
the  development  of  the  intercostal  and  abdominal  muscles,  as  well  as  those  of  the 
extremities. 


EMBRYO  OF  THE  CHICK  AGED 
ABOUT  THIRTY-SIX  HOURS  (IN- 
FERIOR face). 

FB,  Anterior  brain,  on  the  sides  of 
which  are  seen  the  optic  vesicles. 
op;  s.o,  posterior  limit  of  the  fold 
of  somatopleure ;  HB,  posterior 
brain ;  MB,  middle  brain ;  p.v. 
and  v.pl,  protovertebrae ;  ch,  an- 
terior extremity  of  the  notochord ; 
pi,  outline  of  the  area  pellucida; 
pv,  primitive  trace. 


TEE  FCETUS. 


Article  II.— Development  of  the  Various  Organs  in  the  Animal 
Economy. 

Development  of  the  Nervous  System. 

We  will  at  first  glance  at  the  development  of  the  nervous  centres — the  Irain 
and  spinal  cord  ,■  then  their  peripheral  parts — the  tierves. 

1.  First  differentiations  of  the  neuraxis. — The  trace  of  the  central  nervous 
system  or  neuraxis,  resides,  or  has  been  seen,  in  the  primitive  groove,  resulting 
from  an  inflection  of  the  thickened  ectoderm  (Fig.  551).  The  complete  invagina- 
tion of  the  ectoderm  brings  about  the  formation  of  a  tube— the  neural  canal 
(Fig.  552).  From  the  thirty-sixth  hour,  the  medullary  laminae  are  close  to 
each  other  in  front  in  the  middle  line,  but  are  not  yet  fused  together.     From 


Fig.  567. 


TRANSVERSE  SECTION  OF  THE  BODY  OF  AN  EMBRYONIC  DUCK,  THREE  DAYS  OLD.      (AFTER  BALFOUR.) 

om.,  Amnion ;  so.,  somatopleure ;  sp.,  splanchnopleure  ;  wd,  Wolffian  canal ;  st,  segmentary  tube  ; 
ca.v,,  cardinal  vein  ;  m.s.,  muscular  lamina,  or  plate ;  sp.g.,  spinal  ganglion ;  sp.c,  spinal  cord ; 
ch.,  notochord  ;  ao.,  aorta  ;  hy,  endoderm. 

the  fortieth  hour,  the  neural  canal  is  closed  as  far  as  the  rhomloidal  sinus — the 
lozenge-shaped  space  where  the  primitive  groove  is  widest. 

Towards  its  anterior  part,  the  neural  canal  shows  three  successive  dilatations 
— tracts  of  the  brain,  and  constituting  the  three  primitive  cerebral  vesicles.  The 
remainder  of  the  neural  canal  forms  the  spinal  cord. 

2.  Development  of  the  brain.— The  cerebral  vesicles— at  first  three  in  number,  and 
distinguished  as  anterior,  middle,  and  posterior — soon  undergo  an  increase  to  five. 

The  anterior  cerebral  vesicle  throws  out  two  hollow  prolongations  which 
become  the  cerebral  hemispheres,  and  now  constitute  the  anterior  brain.  On  the 
other  hand,  the  anterior  cerebral  vesicle  itself  becomes  the  vesicle  of  the  optic 
thalami,  or  intermediate  brain  (see  Fig.  568). 


1034 


EMBRYOLOGY. 


The  middle  cerebral  vesicle  gives  origin  to  the  cerebral  crura,  the  corpora 
quadrigemina,  and  the  aqueduct  of  Sylvius  or  middle  ventricle.  It  deserves  to 
be  named  the  vesicle  of  the  corpora  quadrigemina  of  the  middle  brain. 

The  third  vesicle  becomes  doubled,  forming  the  cerebellar  vesicle,  or  posterior 
brain,  from  which  arises  the  cerebellum,  and  the  vesicle  of  the  medulla  oblongata 
which  originates  that  body. 

The  middle  vesicle  is  that  which,  at  first,  increases  most  rapidly  in  volume  ; 

it  soon,  however,  ceases  to  grow,  in 
order  to  allow  the  anterior  cell  to 
become  developed,  when  the  brain 
assumes  its  ovoid  form,  with  a  pre- 
dominance of  the  anterior  part. 

Towards  the  end  of  the  first 
third  of  intra-uterine  life,  nearly  all 
the  parts  of  the  brain  are  distinct : 
the  two  hemispheres  have  become 
isolated  by  the  development  of  the 
septum  lucidum ;  the  convolutions 
appear  on  their  surface  ;  and  the  cor- 
pora quadrigemina  and  cerebral  cura 
are  distinctly  defined.  It  is  not  until 
a  little  later  that  the  cerebellum  is 
distinguishable,  as  well  as  the  pons 
Varolii,  medulla  oblongata,  corpora 
restiformia,  and  corpora  pyramidalia. 
3.  Development  of  the  spinal  cord. 
— The  neural  canal  is  the  first  trace 
of  the  spinal  cord  ;  it  occupies  the 
whole  length  of  the  vertebral  spine, 
and  its  cavity  communicates,  in 
front,  with  the  fourth  ventricle. 
"When  the  spine  is  developed,  the 
cord  does  not  increase  proportion- 
ately in  length,  and  appears  to  ascend 
in  the  vertebral  canal  ;  it  stops  about 
the  middle  of  the  sacrum  in  the 
equine  foetus,  but  ascends  higher 
in  the  other  species.  During  this 
apparently  ascensional  movement  is 
developed  the  Jilum  terminate,  and 
the  nerves  of  the  cavda  equina. 

The  walls  of  the  neural  canal,  at  first  very  thin,  increase  in  thickness  by  the 
appearance  of  the  nerve  of  the  cord.  Soon  they  divide  into  two  layers — an  in- 
ternal, the  epithelium  of  the  central  canal  ;  the  other  external — the  (jrey  substance 
of  the  cord.  Gradually  the  canal  contracts,  and  the  marrow  is  seen,  with  its 
longitudinal  furrows. 

At  the  end  of  the  first  month,  the  inferior  roots  are  in  existence,  as  well  as 

the  spinal  ganglia  ;  the  latter  are  developed  at  the  expense  of  the  protovertebrie, 

afi  will  be  shown  presently.     The  superior  roots  are  formed  some  time  afterwards. 

The  envelopes  of  the  cerebro-spinal  centres  are  furnished  by  the  protovertc 


EMBRYO   OF    THE   CHICK   AT    FROM    THIRTY   TO 
THIRTY-SIX    HOURS. 

/.o,  Anterior  bvaiu;  m.6,  middle  brain ;  A.6,  posterior 
brain ;  op.v,  optic  vesicle ;  du.p,  olfactory  fossa ; 
o.f,  vitelline  vein;  p.v,  protovertebrse,  or  meso- 
blastic  somite ;  m./,  line  of  junction  of  the 
medullary  laminae  above  the  neuraxis ;  s.r, 
rhomboidal  sinus ;  t,  caudal  fold  ;  p.r,  remains  of 
the  primitive  groove ;  a.p,  area  pellucida. 


THE  F(ETUS. 


1035 


bral  laminfe  ;  they  are  developed  after  the  sixth  week,  progressing  with  the 
growth  of  the  parts  they  are  destined  to  cover. 

4.  Dn'elopmmt  of  the  nerves. — 'The  development  of  the  nerves  is  somewhat 
obscure.  The  motor  roots  seem  to  arise  from  the  cord  ;  but  the  spinal  ganglia 
are  formed  separately  in  the  protovertebrte,  and  perhaps  originate  the  sensitive 
roots.  The  nerve-branches  begin  by  elongated  ramifying  cells,  which 
become  fused  to  each  other  by  their  extremities — the  nuclei  of  the  cells  lying  at 
the  periphery  becoming  the  nuclei  of  the  white  substance  of  Schwann,  the  proper 
nerve-tissue  being  afterwards  gradually  deposited  between  the  axis-cylinder  and 
the  envelope. 


Fig.  570. 


Fig.  569. 


TRANSVERSE  SECTION  OF  THE  EMBRVO 
OF  A  FOWL  AT  THE  BEGINNING  OF 
THE   THIRD    DAY    OF    INCUBATION,    X 

90-100. 
ch,  Chorda  dorsalis ;  wwh,  position  of  a 
thinning,  or  cavity  in  the  protoverte- 
bral  mass,  dividing  it  into  an  anterior 
and  posterior  portion ;  hp,  parietal 
lamina;  df,  intestinal  fibrous  lamina; 
dd,  intestinal  glandular  lamina ;  dr, 
primitive  intestinal  groove;  A,  corneal 
lamina  j  mr,  medullary  tube  (spinal 
cord);  m,  muscular  lamina;  /),  pleuro- 
peritoneal  cavity ;  af,  fold  of  the 
amnion  ;  ao,  primitive  aorta ;  t)C,  vena 
cardinalis ;  un,  Wolffian  body  ;  ung, 
duct  of  the  Wolffian  body. 


LONGITUDINAL    SECTION   OF     THE    EYE   OF     EMBRYO 
FOWL. 

1,  From  an  embryo  at  about  the  sixty-fifth  hour  of 
incubation ;  2,  from  an  embryo  a  few  hours 
older;  3,  from  an  embryo  at  the  fourth  day  of 
incubation,  h,  Corneal  lamina;  /,  lens  in  fig.  1, 
still  connected  with  the  corneal  lamina,  and 
possessing  a  small  cavity,  o,  in  its  interior  (in 
figs.  2  and  3  it  is  seen  detached,  but  still 
hollow) ;  r,  introverted  portion  of  the  primitive 
optic  vesicle,  subsequently  becoming  the  retina  ; 
a,  posterior  j>art  of  the  optic  vesicle,  which, 
according  to  Remak,  probably  becomes  the 
choroid  coat,  ciliary  processes,  and  iris,  and  in 
figs.  1  and  2  is  still  connected  with  the  brain 
by  the  hollow  optic  nerve ;  x,  thickening  of  the 
corneal  lamina  around  the  spot  from  which  the 
lens  has  detached  itself;  gl,  vitreous  body,  or 
humour. 


The  great  sympathetic  is  early  seen  as  a  nodulated  cord.     It  is  probably  de- 
veloped in  the  same  manner  as  the  other  nerves. 


Development  of  the  Organs  of  Sense. 

The  principal  portion  of  the  organs  of  sense  belong  to  the  dependencies  of 
the  nervous  system,  and  are  developed  with  it ;  the  other  parts  belong  to  the 
external  epithelial  lamina,  the  skin,  and  the  germinative  lamina. 

1.  Visual  Apparatus. — From  the  anterior  cerebral  vesicle  are  given  off  two 
tubular  prolongations,  which  are  directed  forward,  and  terminate  by  the  primitive 
eye-vesicles,  traces  of  the  ocular  globes.  The  hollow  protrusions  form  the  optic 
nerves  ;  the  vesicles  furnish  the  retina  and  choroid.  The  crystalline  lens, 
vitreous  humour,  cornea,  and  sclerotica  arise  from  the  external  blastodermic 
layer.     These  modifications  take  place  in  the  following  manner  : — 

The  external  integument  of  the  foetus  passes  over  the  front  of  the  primitive 
eye-vesicles.  Here  it  shows  a  slight  depression  on  its  outer  surface,  and  on  its 
inner  face  a  cellular  protrusion  (Fig.  570,  1  o),  which,  becoming  developed, 


1036  EMBRYOLOGY. 

surrounds  the  external  depression,  completely  closes  it,  and  constitutes  the  com- 
mencement of  the  crystalline  lens  (Fig.  570,  2  /).  The  latter,  thus  formed, 
presses  on  the  primitive  eye-vesicle,  pushes  it  backwards  (2),  and  gives  rise  to  a 
secondary  eye-vesicle,  the  anterior  wall  of  which  becomes  the  retina,  and  the 
posterior  wall  the  choroid.  The  lens  is,  therefore,  a  dependency  of  the  epithelial 
lamina  ;  the  cells  composing  it  become  elongated  into  fibres  in  the  centre,  and 
are  disposed  at  its  circumference  as  a  primary  amorphous  envelope — the  crystalline 
capsule — and  afterwards  as  a  secondary  envelope  rich  in  vessels. 

The  portion  of  the  integument  which  is  not  doubled  to  form  the  lens  envelops 
the  globe,  and  gives  rise  to  the  sclerotica  and  cornea  ;  the  epidermis  furnishes  the 
epithelium  of  the  latter,  which  becomes  distinct  from  the  sclerotica  in  the  course 
of  the  fourth  month. 

An  aperture — the  sclei-otic  cleft — is  made  at  the  lower  part  of  the  fibrous 
envelope  of  the  eye  ;  this  is  connected  with  the  development  of  the  vitreous  body — 
a  prolongation  of  the  derm — a  kind  of  conjunctival  bud  passing  through  this 
opening,  and  placing  itself  between  the  crystalline  lens  and  the  anterior  wall  of 
the  secondary  eye-vesicle  (3  gl),  where  it  is  developed  and  transformed  into  the 
vitreous  body.  At  first  it  is  encircled  by  vessels  like  the  lens,  but  these  disappear 
before  the  termination  of  gestation. 

The  optic  nerve  is  developed  in  the  pedicle  uniting  the  eye-vesicle  to  the 
anterior  cerebral  vesicle.  The  retina  is  formed  by  the  inner  lamina  of  the 
secondary  eye-vesicle  ;  it  extends  to  the  lens  in  changing  its  character  anteriorly. 
According  to  Remak,  the  choroid  is  constituted  by  the  posterior  lamina  of  the 
eye-vesicle  ;  it  advances  at  first  to  the  lens,  and  then  becomes  inflected  in  front 
to  form  the  iris.  The  borders  of  the  pupil  are  attached  to  the  vascular  envelope 
of  the  lens,  and  this  gives  rise  to  the  pupillary  diaphragm,  which  disappears  before 
birth. 

The  motor  and  protective  organs  of  the  eye  are  gradually  developed  around 
the  globe.  The  eyelids  are  small  cutaneous  folds  that  appear  towards  the  first 
third  of  uterine  life  ;  they  increase,  and  unite  at  their  margin  until  immediately 
before,  or  soon  after  birth,  when  they  separate. 

The  lachrymal  gland  is  a  dependency  of  the  epithelial  lamina  which  is  pushed 
in  above  the  globe.  At  first  solid,  it  gradually  becomes  channeled  out  by  cavities, 
from  which  arise  the  excretory  ducts. 

2.  Auditory  Apparatus. — The  internal  ear,  auditory  nerve,  and  middle  ear, 
are  developed  separately.  The  labyrinth  appears  in  the  shape  of  a  vesicle,  which 
is  not  in  direct  relation  with  the  posterior  cerebral  cell ;  it  is  constituted  by 
a  depression  of  the  epidermic  lamina — the  auditory  fossa— which  is  gradually 
developed,  and  at  last  becomes  a  closed  cavity.  At  this  time,  the  wall  of  the 
labyrinth  is  only  a  simple  epithelial  membrane  ;  this  is  soon  covered,  outwardly, 
by  a  vascular  connective  membrane  that  separates  into  three  layers — an  internal, 
joined  to  the  epithelium  to  form  the  membranous  labyrinth  ;  an  external,  that 
lines  the  cartilaginous  labyrinth  ;  and  a  middle,  the  soft,  embryonic,  connective 
tissue  of  which  disappears,  and  is  replaced  by  the  perilymph.  At  the  same  time  that 
these  changes  of  structure  are  occurring,  the  vesicular  form  of  the  labyrinth  is 
modified,  and  shows  the  cochlea,  semicircular  canals,  utriculus,  and  saccidus. 

The  middle  and  externcd  ear  arise  from  the  first  pharyngeal  (branchial)  cleft, 
which  is  never  completely  closed,  while  the  others  disappear.  At  first,  then,  we 
find  a  cavity  communicating  externally  with  the  pharynx  ;  this  cavity  contracts, 
and  is  separated  into  two  portions  by  a  partition  that  spreads  across  its  middle, 


THE  FCETUS. 


1037 


and  which  becomes  the  membrana  tympani ;  the  internal  portion  is  the  middle 
ear  and  Eustachian  tube  ;  the  external  portion  is  the  external  auditory  canal. 

The  ossicula  auditus  appear  in  a  cartilaginous  state  towards  the  third  month  ; 
they  gradually  ossify,  and  have  scarcely  acquired  their  definitive  volume  at  birth. 
The  external  ear  {concha)  is  developed  beneath  the  integument  after  the  second 
month. 

3.  Olfactory  apparatus. — This  commences  by  two  depressions  of  the  epider- 
mic lamina,  analogous  to  the  auditory  fossa  and  that  of  the  lens.  These  two 
olfactory  fossas  appear  below  the  ocular  vesicles,  and  become  more  and  more  dis- 
tinct, being  margined  by  small  projections  which  increase  their  depth.  Behind, 
they  communicate  with  the  pharynx.  The  appearance  of  the  palate  separates 
them  in  front  from  the  buccal  cavity,  and  from 
this  period  the  nasal  fossae  are  constituted.  They 
are  completed  by  the  development  of  the  bones 
of  the  face. 

The  olfactory  hidbs  and  nerves  are  primarily 
hollow,  and  joined  to  the  anterior  cerebral  cell. 
The  nostrils  are  formed,  in  the  young  foetus,  by 
a  mass  of  mucus  and  epithelium  ;  towards  the 
middle  of  gestation  they  are  open. 

4.  Gustatory  apparatus. — See,  subsequently,     I 
the  development  of  the  tongue^  in  digestive  ap- 


AN  EMBRYO  (HUMAN)  OF  FOCB 
WEEKS,  ENLARGED  ABOUT  THREE 
TIMES. 

a.  Vesicle  of  corpora  quadrigemina ; 
6,  vesicle  of  cerebral  hemispheres; 
c,  vesicle  of  third  ventricle  ;  d, 
vesicle  for  cerebellum  and  medulla 
oblongata  ;  e,  auditory  vesicle  ;  /, 
olfactory  fossa ;  h,  liver ;  **, 
caudal  extremity. 


5.  Tactile  apparatus. — The  skin  and  its  de- 
pendencies.— The  skin  is  developed  at  the  expense 
of  the  epidermic  lamina  of  the  middle  layer  of 
the  blastoderm.  The  cutaneous  laminfe — by  the 
modification  of  their  elements — form  the  derma, 
in  which  the  blood-vessels  are  very  apparent  at 
the  third  month.  In  the  epidermis,  the  mucous 
and  the  horny  layers  are  soon  distinguished  ;  in 
the  first,  the  pigment  is  visible  at  the  commence- 
ment of  the  fifth  month  in  the  larger  Quad- 
rupeds. When  the  foetus  increases  in  volume,  the  epidermis  exfoliates,  and  its 
debris  floats  in  the  liquor  amnii. 

In  the  third  month,  the  hairs  are  seen  in  the  foetus  of  the  Mare  and  Cow  ; 
they  appear  at  first  on  the  eyebrows,  lips,  and  the  joints  of  the  limbs  ;  at  the  sixth 
or  seventh  month  they  cover  the  body.  They  may  be  shed  and  renewed  before 
birth.  They  are  developed  in  a  prolongation  of  the  epidermic  lamina,  which  is 
embedded  in  the  substance  of  the  derm  ;  it  is  shaped  like  a  httle  bottle,  and  is 
composed  of  a  mass  of  cells  ;  in  its  centre,  these  cells  are  modified  and  collected 
together  to  form  a  small  cone,  the  base  of  which  covers  the  growing  papilla.  This 
cone  becomes  elongated,  touches  the  surface  of  the  epidermis,  doubles  under  the 
effort  to  push  through  it,  and  finally  makes  its  exit,  after  which  it  can  grow  freely. 

The  sebaceous  and  sudoriparous  glands  are  developed  in  the  same  manner, 
towards  the  middle  period  of  uterine  existence. 

"  The  horny  productions — the  claics,  hoofs,  ergots,  chestnuts — begin  to  show 
themselves  early.  Towards  the  end  of  the  second  month,  in  the  fcetus  of  the 
Cow,  there  is  perceived,  at  the  extremity  of  each  limb,  a  small  pale,  translucid, 
conical  tubercle,  which  is  the  rudiment  of  the  hoof.     At  the  commencement  of 


1038 


EMBRYOLOGY. 


the  fourth  montli,  or  thereabouts,  the  hoof,  better  defined,  has  become  firm  and 
opaque,  and  has  assumed  a  fine  yellow  tint.  At  mid-term,  brown  or  black 
patches  are  manifest  if  the  coronet  is  provided  with  pigment ;  it  is  only  about 
the  end  of  gestation  that  the  hoof  towards  the  coronet  begins  to  have  the 
greenish  hue  peculiar  to  horn  destitute  of  pigment,  but  the  remainder  of  this 
production — especially  at  the  inferior  part — preserves  its  yellow  colour  uutil  birth. 
In  Solipeds,  the  '  chestnuts '  are  shown  at  mid-term,  in  the  shape  of  thin  brown 
plates,  which  are  soon  darker-coloured."  * 

The  horn  of  the  hoof  is  not  at  first  tubular ;  after  birth  it  is  shed,  and  is 
succeeded  by  a  more  consistent  tubular  horn,  which  had  been  forming  beneath  it. 


Development  of  the  Locomotory  Apparatus. 

1.  The  Skeleton. — ^We  have  seen  at  p.  19  how  the  development  and  growth 
of  the  bones  take  place  ;  it  is  therefore  needless  to  recur  to  this  subject  here  ;  so 
we  will  limit  ourselves  to  an  examination  of  the  mode  of  development  of  the 
principal  sections  of  the  skeleton. 

A.  Development  of  the  vertebra. — The  vertebral  spine  is  the  first  portion  of 
the  skeleton  manifested  in  the  embryo  ;  it  is  represented  by  the  chorda  dorsalis 


Fig.  572. 


Fig.  573. 


DIAGRAM    SHOWING    THE   POSITION   OF    THE 
CHORDA    DORSAUS   IN    THE   BODY   OF   THE 
VERTEBRA,  AND  THE  FORMATION  OF  THE 
DIAGRAM    SHOWING    THE    ATTENUATION    OF  NEURAL   ARCHES. 

THE  CHORDA  DORSALIS  IN  THE   MIDDLE  OF 

THE  BODIES  OF  THE  VERTEBRA,  WHILST  c^>  Chorda  dorsalis ;  cv,  body  of  the  verte- 

PRESERViNG  ITS  ORIGINAL  DIAMETER  IN  bia  ;  a,  ueural  arch,  or  neurapophysis ;  c, 

THE  INTERVERTEBRAL  SPACES.  "b ;  ^w,  transverse  process. 

ch,  Chorda  dorsalis;  v,  body  of  vertebra  ;  U, 
intervertebral  spaces. 

— a  stalk  constituted  by  a  mass  of  cells  situated  in  the  interior  of  a  transparent 
sheath.  The  protovertebrce.  appear  on  each  side  of  the  chorda  dorsalis  ;  in  becom- 
ing developed,  these  parts  encircle  the  latter  and  the  medullary  canal ;  from  this 
results  the  external  theca  of  the  cord,  and  the  superior  uniting  membrane.  From 
this  time,  the  vertebral  column  exists  in  the  shape  of  a  membranous  axis. 

Soon  this  membranous  spine  is  segmented  to  give  rise  to  the  vertebrae,  and 
its  various  portions  gradually  become  cartilaginous.  Each  persistent  vertebra 
does  not  exactly  correspond  to  a  protovertebra.  In  reality,  the  latter  takes  a 
share  in  the  formation  of  two  vertebrge,  and  divides  into  two  portions — an 
inferior,  which  constitutes  the  posterior  moiety  of  a  permanent  vertebra  ;  and 
a  superior,  which  forms  the  anterior  moiety  of  the  persistent  vertebra  imme- 
diately behind  the  preceding  and  the  intervertebral  disc. 

'  Colin,  Trait€de  Fhysiologie  Compar^e  des  Animaux,  2nd  Edition.     Paris,  1873. 


THE  FCETUS. 


1039 


The  bodies  of  the  vertebras  are  developed  more  rapidly  than  their  spinal 
portion  :  thus,  towards  the  end  of  the  second  month,  all  the  vertebral  bodies 
are  already  cartilaginous,  while  the  vertebral  laminae  are  yet  membranous.  It 
is  only  in  the  third  month  that  ossification  begins  in  the  vertebral  column.  The 
number  of  osseous  nuclei — primary  and  complementary — is  not  the  same  in  all 
species  ;  they  have  been  enumerated  at  p.  20.  In  a  large  number,  the  spinous 
process  is  regarded  as  the  result  of  the  joining  together  of  the  two  moieties  of 
the  vertebral  arch  ;  in  the  Sheep,  on  the  contrary,  the  spinous  process  forms  a 
nucleus  altogether  independent  of  the  vertebral  arches.  Thomas  has  noted  this 
disposition,  and  he  considers  it  as  peculiar  to  animals  the  anterior  dorsal 
vertebrae  of  which  are  furnished  with  a  long  spinous  process. 

During  ossification,  the  chorda  dorsalis  disappears,  except  between  the 
vertebrae,  where  it  is  developed  to  form  the  intervertebral  substance  or  discs. 

B.  Development  of  the  cranium  and  face. — The  brain  is  enveloped  by  a 
membrane  formed  at  the  expense  of  the  protovertebral  laminae.  This  cranial 
membrane  becomes  partly  cartilaginous,  partly  fibrous  ;  the  cartilage  exists  at  the 
base  of  the  cranium,  and  seems  to  prolong  the  bodies  of  the  vertebrse  into  this 
region ;  indeed  it  is  known  that  the  skull  may  be  resolved  into  four  portions, 
each  corresponding  to  a  vertebra.  The  cartilage  is  insensibly  transformed  into 
bone  ;  while  the  fibrous  part — comprising  the  roof  of  the  skull  and  its  lateral 
walls — passes  directly  into  an  osseous  state. 

The  bones  of  the  face  are  developed  at  the  expense  of  the  pharyngeal  arches. 
This  designation  is  given  to  four  laminae  (or  lamellce)  which  spring  from  the 
anterior  extremity  of  the  chorda  dorsalis,  and  double  downward  and  inward  to 
join  those  of  the  opposite  side.     They  are  also  named  the  branchial  and  visceral 


Fig.  574. 


arches,  and  the  spaces  between 
them  are  called  the  pharyngeal 
clefts.  The  upper  jaw,  mouth, 
nasal  cavities  :  i.e.  the  nasal, 
maxillary,  and  palatine  bones, 
are  furnished  by  the  first  arch. 
Meckel's  cartilage,  which  arises 
from  the  handle  of  the  malleus 
to  pass  towards  the  inferior 
maxilla,  is  also  a  dependency  of 
this  branchial  arch ;  it  disap- 
pears towards  the  sixth  or 
seventh  month.  It  is  to  be 
remarked  that,  at  the  com- 
mencement, the  mouth  com- 
municates with  the  nasal  cavi- 
ties ;  the  palate  is  developed  in 
two  moieties  which  advance 
towards  each  other,  though  they 
remain  a  long  time  apart ;  so 
that  at  this  time  the  young 
animal  really  has  a  hare-lip.  The  second  pharyngeal  arch  forms  the  stapes,  the 
pyramidal  process  of  the  temporal  bone,  the  styloid  arch,  and  the  branch  of 
the  hyoid.  The  third  develops  the  hyoid  bone,  with  its  cornua  ;  while  the 
fourth  arch  only  constitutes  the  soft  parts  of  the  neck. 


THE    HEAD   OF    A    FCETAL   LAMB    DISSECTED   TO    SHOW 
MECKEL'S   CARTILAGE. 

M,  Meckel's  cartilage;  wi,  the  malleus;  t,  incus  ;  Zy,  th* 
tympanic;  H,  the  hyoid;  Sg,  the  squamosal;  Vt, 
pterygoid ;  pi,  palatine ;  L,  lachrymal ;  pmx,  pre- 
maxilla ;  N,  nasal  sac,  Em,  Eustachian  tube. 


1040  EMBRYOLOGY. 

The  integument  covering  the  pharyngeal  bones  is  sometimes  imprisoned  at 
some  points,  when  fusion  of  the  bones  of  these  arches  occurs.  There  then  result 
small  dermoid  cysts  that  slowly  enlarge,  and  which  the  surgeon  is  sometimes 
called  upon  to  remove  from  time  to  time,  as  they  disfigure  the  face — if  they  have 
no  other  inconvenience. 

C.  Development  of  the  Thorax. — The  ribs  are  dependencies  of  the  protoverte- 
bral  laminte,  which  curve  towards  the  lower  face  of  the  vertebral  column.  The 
true  ribs  are  most  rapidly  developed,  and  before  attaining  the  middle  line  are 
united  by  their  internal  extremity,  and  form  a  moiety  of  the  sternum.  A  fissure 
separates  the  costal  arches  of  the  right  side  from  those  of  the  left :  this  gradu- 
ally contracts,  and  finally  disappears,  and  the  sternum  is  then  formed.  The  ribs 
are,  after  the  petrous  bone,  the  parts  of  the  skeleton  which  are  most  promptly 
ossified,  ossification  commencing  in  the  middle  ribs. 

The  costal  arches  do  not  belong  exclusively  to  the  dorsal  vertebrae,  but  have 
a  tendency  to  form  along  the  whole  length  of  the  spine  ;  and  it  is  not  rare  to 
see— attached  to  the  lumbar  vertebrae— a  small  cartilaginous  nucleus,  which  is 
soon  lost  in  the  texture  of  the  abdominal  walls.  This  nucleus  assumes  large 
dimensions  on  the  last  cervical  vertebrae  of  Birds. 

The  form  of  the  thorax  varies  with  the  species ;  in  some  it  is  circular,  in 
others  it  is  flattened  laterally  ;  and  in  all  cases  it  is  less  developed  in  the  foetus 
and  young  animal  than  in  the  adult.  It  is  in  the  latter  that  the  thoracic  cavity 
presents,  proportionately,  its  greatest  dimensions. 

D.  Development  of  the  Limbs. — The  limbs  do  not  show  themselves  until  after 
the  formation  of  the  spinal  column,  the  pharyngeal  arches,  and  the  thoracic 
parietes.  They  appear  as  four  little  prolongations  from  the  thorax  and  pelvi^ 
and  are  slightly  enlarged  at  their  origin  and  constricted  in  the  middle.  Their 
free  extremity  is  flattened,  and  either  divides  or  remains  single,  as  the  animal 
has  one  or  more  apparent  digits.  It  is  in  these  prolongations  that  the  carti- 
laginous segments  are  developed,  which,  at  a  later  period,  become  the  bones  of  the 
limbs.  For  the  manner  in  which  ossification  is  carried  on  in  each  bone,  reference 
must  be  made  to  Osteology,  Articles  IV.  and  V.,  pp.  97  and  127. 

2.  Muscles. — The  muscles  are  developed  around  the  bones  when  these  have 
become  perfectly  distinct.  They  may  be  divided  into  four  groups — the  vertebral 
muscles,  which  come  from  the  muscular  laminae  of  the  protovertebrae  ;  the 
visceral  muscles — thoracic  and  abdominal  cavities,  neck  and  jaw — having  the 
same  origin ;  the  cutaneous  muscles,  which  are  developed  at  the  expense  of 
the  cutaneous  laminae  of  the  middle  layer  of  the  blastoderm ;  and  the  muscles 
of  the  hmbs,  the  development  of  which  is  not  yet  perfectly  known. 

It  was  at  one  time  believed  that  the  muscular  fibres  were  formed  by  the 
junction — end  to  end — of  several  elongated  cells ;  but  it  is  now  known  that 
they  are  constituted  by  a  single  cell  which  lengthens,  and  the  nuclei  of  which 
multiply  and  lie  at  the  surface,  while  its  contents  are  transformed  into  a  substance 
that  offers  the  characteristics  of  contractile  tissue.  The  sarcolemma  is  formed 
after  the  fibre,  by  a  modification  of  the  connective  tissue  surrounding  it. 

Development  of  the  Circulatory  Apparatus. 

During  the  first  days  which  follow  the  appearance  of  the  embryo  in  the 
substance  of  the  blastodermic  layer,  there  is  no  trace  of  vessels  in  the  area 
germinativa.     It  is  not  long,  however,  before  the  heart  and  some  blood-vessels 


THE  FCETUS. 


1011 


ifh-:' 


are  seen  in  the  middle  layer,  the  vessels  extending  to  the  surface  of  the  um- 
bilical vesicle,  which  gradually  shows  itself.  While  the  contents  of  the  vitel- 
line vesicle  are  undergoing  absorption  by  the  embryo,  the  heart  is  being  completed, 
the  vessels  are  developing,  the  allantois  is  formed,  and  the  placental  circulation — 
which  continues  until  birth — is  established.  From  this  time  the  circulatory 
apparatus  has  acquired  its  definitive 
disposition.  Fig.  575. 

1.  Appearance  of  the  heart. — Circu- 
lation in  the  umbilical  vesicle. — The 
pleuro-peritoneal  cavity  of  the  embryo 
presents,  anteriorly,  a  diverticulum — 
the  cardiac  cavity — in  the  interior  of 
which  the  heart  is  developed. 

From  what  has  been  already  said, 
it  will  be  understood  that  the  circu- 
latory apparatus  is  adapted  to  take  the 
part,  successively,  of  the  umbilical 
vesicle  and  the  placenta  ;  and  from  this 
two  great  systems  arise — the  umbilical 
or  omphalo-mesenteric  circulation,  and 
the  allantoid  circulation. 

As  Dareste  has  it,  the  heart  is 
primarily  double.  Its  two  portions  are 
formed  on  each  side  by  a  folding  in- 
wards of  the  fibro-intestinal  lamina 
and  its  endothelial  lining.  The  two 
cardiac  cavities  open  into  each  other 
by  the  absorption  of  the  walls  joined 
as  a  septum,  and  the  simple  heart 
assumes  the  form  of  a  looped  tube 
inclined  to  the  right,  as  in  Fig.  577. 

As  soon  as  it  shows  itself,  the 
heart  contracts  and  dilates  alternately, 
the  movements  being  very  slow,  though 
they  gradually  become  quicker.  To- 
wards the  twelfth  day,  the  central 
organ  of  the  circulation  has  the 
form  of  a  contractile  cylindrical  tube. 
From  its  anterior  part  spring  two 
branches — the  aortic  arches  {arcus 
aortce) — which  are  directed  towards 
the  head  of  the  embryo,  and  are 
afterwards  inflected  downwards  and 
backwards. 

The  aortic  arches  join  together  to  constitute  the  single  aorta,  which,  in  its 
turn,  divides  into  two  trunks— the  arterice  vertebralis,  or  primitive  aortcp.  These 
vessels  pass  along  the  lower  surface  of  the  embryo,  parallel  to  each  other,  and 
furnish  during  their  course  four  or  five  divisions— the  omphalo-mesenteric  arteries 
—which  ramify  in  the  area  germinativa,  and  open  into  a  limitary  vein  named 
the  sinus  (or  vena)  terminalis.     From  the  network  of  the  area  and  the  sinus 


DIAGRAM   OF   THE   FORMATION   OP   THE    VENJE 
OMPHALO-MESENTERICiE    AND    UMBILICALES. 

1,  At  the  time  of  the  first  appearance  of  the  um- 
bilicales,  and  the  commencement  of  the  om- 
phalo-mesenteric£e  ;  2,  at  the  time  of  the  first 
appearance  of  the  branches  to  and  from  the 
liver,  and  the  diminution  of  the  omphalo- 
mesenteric vessels ;  3,  4,  at  the  period  of  com- 
plete fcetal  circulation  in  1,  omphalo-mesenteric 
trunk  ;  in  2,  3,  remains  of  it ;  in  4,  vein  of  the 
yolk-sac  alone ;  om',  right,  and  om",  left  vena 
omphalo-mesentericse ;  u,  trunk  of  the  um- 
bilical vein ;  u',  right,  and  u",  left  vena  um- 
bilicalis;  c?c,  ductus  Cuvieri ;  y,  jugularis;  c, 
cardinalis  ;  /,  liver;  ha,  hepatica  advehentes; 
hr,  hepaticffi  revehentes ;  m,  mesentericae  ;  da, 
ductus  venosus  Arantii ;  ci,  cava  inferior;  p, 
vena  portee ;  I,  lienalis ;  m,  mesenterica  su- 
perior. 


1042  EMBRYOLOGY. 

arise  two  vessels — the  vence  omphalo-mesentericce — which  enter  the  posterior 
extremity  of  the  heart. 

In  Birds  there  are  only  two  omphalo-mesenteric  or  vitelline  arteries. 

The  circulation  in  the  umbilical  vesicle  is  somewhat  ephemeral  in  several 
species,  and  it  has  been  already  stated  that  the  vesicle  is  atrophied  at  an  early 
jieriod  of  f cetal  life.  In  Birds  it  is  most  extensive  ;  and  its  presence  may  be  noted 
in  the  Carnivora  during  the  whole  term  of  uterine  existence. 

2.  Development  of  the  heart  and  vessels. — Placental  circulation. — The  hearty 
which,  until  now,  was  a  cylindrical  tube,  is  considerably  modified  before  it  attains 
its  complete  development.  In  its  different  phases,  it  successively  offers  all  the 
forms  known  to  exist  in  vertebrate  animals.  The  first  change  consists  in  an 
inflection  ;  the  tube  curves  in  an  S-shaped  manner,  so  that  its  inferior  part  becomes 
superior  ;  it  then  dilates  at  three  points  :  the  anterior  and  superior  dilatation 
situated  at  the  origin  of  the  aorta  is  named  the  aortic  bulb  {bulbus  aortce)  ;  the 
middle  dilatation,  the  ventricular  cavity;  and  the  posterior  dilatation,  the  auri- 

Fig.  576. 


HEART   OF   THE   EMBRVO  OF   A    RABBIT,  THE   SAME,   SEEN    FROM    BEHIND. 

SEEN  FROM  BEFORE.  g^    Venae    omphalo-mesentericae ;     d.    right 

ta,  Truncus  arteriosus;   I,  left  ventricle;  r,  auricle;  e,  bulbus  aortfe ;  /,  the  six  aortic 

right  ventricle;  a,  auricle;  u,  venous  sinus.  arches;  c,  atrium  ;  6,  auriculae. 

cidar  cavity.  Haller's  passage  is  the  name  given  to  the  constriction  between  the 
auricle  and  ventricle,  which  at  this  time  are  single.  They  do  not  remain  long  so, 
however.  The  ventricular  cavity  is  the  first  to  be  divided  into  two  compartments, 
and  the  division  is  marked  externally  by  a  groove  which  appears  on  the  surface 
of  the  heart  of  the  Ovine  embryo  towards  the  nineteenth  day,  and  on  the  twenty- 
fifth  in  the  Equine  foetus.  This  groove  coiTesponds  to  an  interventricular 
septum,  which  insensibly  rises  from  the  bottom  of  the  ventricles  ;  when  it  reaches 
the  auricles,  it  concurs  in  forming  the  auriculo-ventricular  openings.^  The 
margins  of  these  openings  are  provided  with  a  small  slightly  salient  lip,  which 
afterwards,  in  developing,  originates  the  mitral  and  tricuspid  valves.  The  heart 
has  now  three  cavities — two  ventricles  and  an  auricle  ;  but  in  a  brief  period  the 
latter  is  doubled,  and  the  compartments  are  then  four  in  number.  Externally, 
there  is  observed  a  depression  which  shows  the  division  in  the  auricles  ;  at  a  point 
corresponding  to  it,  a  septum  is  developed  in  their  interior  which  remains  incom- 
plete during  the  whole  of  foetal  life,  being  perforated  by  the  foramen  of  Botal. 
With  regard  to  the  aortic  bulb,  it  contracts  and  divides  into  two  vessels — the  aorta 
and  pulmonary  artery. 

'  This  septum  is  sometimes  arrested  in  its  development,  whence  results  an  abnormal  com- 
munication between  the  ventricles.  Some  instances  have  been  given  when  describing  the 
heart. 


TEE  FCETUS. 


1043 


The   arteries   are  developed  partly   at   the   expense   of   the   vessels 
primary    circulation,    and    partly    in    the    vascular    lamina    of    the 


Fig.  578. 


of  the 
mbryo. 

The  heart,  when  it  was  only  a  simple 

cylindrical   tube,    presented    at    its 

anterior  extremity  two  aortic  arches, 

which  curved  backwards  and  united 

to  form  the  single  aorta,  then  the 

vertebral  or  common  aortte.     The 

aortic  arches  are  situated  at  the  inner 

face   of   the    two    first    pharyngeal 

arches ;    afterwards    more    are    de- 
veloped, which  are  placed  within  the 

other  pairs  of  arches,  until  the  num- 
ber is  increased  to  five,  though  they 

never  all  exist  at   the   same   time. 

Some  atrophy,  while  others  are  being 

developed  :    the    two   first  entirely 

disappear  ;  the  third  form  the  caro- 
tids ;  the  fourth  the  axillary  arteries 

and  the  arch  of  the  aorta  ;  the  fifth 

atrophies  on  the  right,  and  on  the 

left  originates  the  pulmonary  artery, 

the  ductus  arteriosus,  and  the  aorta. 

The  latter  is  continued  along  the 

spine    by  the    fusion    of   the    two 

primitive  aortae.     They  present,  at 

their  posterior  extremity,  the  pelvic 

vessels — which  are  very  small — and 

the  umbilical  arteries,  which  are,  on  the  contrary,  remarkable  for  their  volume 


HEART  OF  AN  EQUINE  FCETUS. .  THE  RIGHT  AURICLE 
AND  PUbXERIOR  VKNA  CAVaWaVE  BEKN  OPENED 
TO   SHOW    THE    FORAMEN   OF   BOTAL. 

1,  Left  ventricle  ;  2,  right  ventricle  ;  3,  interior  of 
the  right  auricle ;  4,  posterior  vena  cava ;  5, 
foramen  of  Botal. 


PLAN   OF   THE   AORTA   AND    ITS   ARCHES   AT   AN   EARLY   PERIOD. 

1  Truncus  arteriosus,  with  one  pair  of  aortic  arches,  and  dotted  lines  indicating  the  position  of  the 
'  second  and  third  pairs ;  2,  the  same,  with  four  pairs  of  aortic  arches,  and  indications  of  the  fifth ; 
3,  the  same,  with  the  three  posterior  pairs  of  aortic  arches,  from  which  the  permanent  vessels  of 
the  embryo  are  developed,  with  dotted  outlines  showing  the  position  of  the  two  (now)  obliterated 
anterior  arches  ;  4,  permanent  arterial  trunks  in  their  primitive  form,  the  obliterated  portions 
still  shown  in  dotted  outline,  1-5,  primitive  aortic  arches,  a.  Aorta  ;  p,  pulmonary  artery  ; 
p',  p",  branches  to  the  lungs  ;  aio',  root  of  thoracic  aorta  (ad)  on  leit  side  ;  aw,  obliterated  root 
springing  from  right  side ;  s".  s',  subclavian  artery  ;  v,  vertebral ;  ax,  axillary ;  c,  common 
carotid ;  c',  external  carotid  ;  c",  internal  carotid. 

The  peripheral  arteries  arise,  independently  of  the  central  vessels,  on  the 
interior  of  the  vascular  lamina.     They  appear  in  the  form  of  solid  cellular 


1044 


EMBRYOLOGY. 


DIAGRAM  OF  THE  CIR- 
CULATION AT  THE 
COMMENCEMENT  OF 
THE  FORMATION  OF 
THE  PLACENTA 

(seen      FROM      THE 

front). 
a,  Venous  sinus  re- 
ceiving all  the  sys- 
temic veins;  b,  right 
auricle ;  6',  left 
auricle;  c,  right 
ventricle ;  c',  left 
ventricle ;  d,  bulbus 
aorticus,sub(iividing 
into,  e,  e',  e",  bran- 
chial branches ;  /, 
/',  arterial  trunks 
formed  by  their  con- 
fluence; g,  g',  vena 
azygos  superior ;  h, 
h',  confluence  of  the 
superior  and  inferior 
azygos ;  j,  vena  cava 
inferior;  k,  k',  vena 
azygos  inferior ;  m, 
descending  aorta ; 
n,  n,  umbilical  arte- 
ries proceeding  from 
it ;  0,  o',  umbilical 
veins;  g,  omphalo- 
mesenteric vein ;  r, 
omphalo-mesenteric 
artery  distributed 
on  the  walls  of  the 
vitelline  vesicle,  t; 
V,  ductus  venosus; 
y,  vitelline  duct;  z, 
chorion. 


branches,  which  are  hollowed  in  the  centre  by  a  cavity  in 
which  the  cells  become  free.  In  proportion  as  these  new 
vessels  are  developed,  the  omphalo-mesenteric  vessels  dis- 
appear, until  at  last  there  only  remain  one  or  two  ducts 
that  pass  to  the  umbilical  vesicle. 

The  umbilical  veins  are  developed  immediately  after  the 
formation  of  the  omphalo-mesenteric  veins  ;  they  enter  the 
common  trunk  of  the  latter,  and  when  its  ramifications 
diminish  in  volume,  the  umbilical  veins  increase  rapidly  ; 
when  the  liver  is  formed  around  them,  they  throw  into  it 
branches,  which  are  the  rudiments  of  the  hepatic  network. 
Between  the  hepatic  and  sublobular  veins,  the  umbilical 
vein  communicates  with  the  vena  cava  by  the  ductus  venosits 
of  Aranzi,  which,  according  to  M.  Colin,  does  not  exist  in 
the  foetus  of  Solipeds  in  the  last  moiety  of  uterine  life. 

The  veins  of  the  embryo  form  four  principal  trunks  at 
first — two  anterior,  the  anterior  cardinal  veins ;  and  two 
posterior — the  posterior  cardinal  veins.  The  veins  of  the 
same  side  unite  in  twos,  from  which  result  the  Cuvierian 
ducts  ;  these  open  transversely  into  the  omphalo-mesenteric 
trunk,  close  to  the  auricular  cavity. 

The  anterior  cardinal  veins  issue  from  the  cranium  ; 
they  form  the  jugular  veins,  and  communicate  by  an  anasto- 
mosis that  extends  transversely  from  left  to  right.  Below 
this  anastomosis,  the  left  vein  gradually  atrophies,  as  does 
the  Cuvierian  duct  of  the  same  side  ;  but  the  canal  on  the 
right  side  increases,  and  becomes  the  anterior  vena  cava. 

The  posterior  vena  ca,va  appears  behind  the  liver  towards 
the  fifth  month  ;  it  receives  the  veins  of  the  kidneys  and 
Wolffian  bodies,  and,  behind,  it  anastomoses  with  the  cardinal 
veins.  The  latter  disappear  in  their  middle  portion,  and  are 
replaced  by  the  vertebrcd,  veins,  the  right  of  which  forms  the 
vena  azygos.  There  only  remain  the  two  extremities  of  the 
cardinal  veins  ;  the  anterior  enters  the  Cuvierian  duct,  and 
the  posterior  constitutes  the  hypogastric  and  crural  veins. 
From  this  disposition,  it  will  be  seen  that  at  first  the  venous 
system  of  the  foetus  is  perfectly  symmetrical,  but  that  in  the 
adult  animal  it  becomes  asymmetrical. 

In  consequence  of  these  successive  developments,  the 
placental  circulation  is  instituted,  and  continues  the  same 
until  the  termination  of  intra-uterine  life.  The  heart  is 
always  the  organ  that  propels  the  blood,  and  this  passes 
into  the  arteries,  reaches  the  umbilical  arteries,  and  is  carried 
to  the  placenta.  There  it  is  renewed — becomes ^r^^rm?  through 
contact  with  the  maternal  blood — and  is  returned  by  the 
umbilical  veins.  In  the  substance  of  the  liver  it  is  mixed 
with  the  venous  blood  of  the  intestines  and  posterior  ex- 
tremities, through  the  medium  of  the  ductus  venosus.  and  at 
last  arrives  at  the  right  auricle,  then  passes  into  the  right 
ventricle,  from  which  it   is    propelled  by  a  contraction. 


THE  FCETUS. 


1045 


Instead  of  going  to  the  lungs — which  do  not  yet  act  as  respiratory  organs — the 
blood,  being  pressed  by  the  contraction  of  the  right  ventricle,  passes  into  the 
aorta  by  the  ductus  arteriosus. 

To  sam  up,  the  foetus  never  receives  pure  arterial  blood  into  its  organs,  this 
being  always  mixed  with  venous  biood — the  mixture  taking  place  at  several 
points  :  1.  By  the  foramen  of  Botal.  2.  In  the  aorta  by  the  ductus  arteriosus. 
3.  In  the  liver  by  tlie  ductus  venosus.  The  head  and  neck  are  the  parts  which 
receive  the  purest  arterial  blood — a  fact  that  explains  the  predominance  of  the 
anterior  over  the  posterior  portion  of  the  body  of  the  foetus. 

At  birth,  the  conditions  of  existence  being  suddenly  changed,  marked  modifi- 
cations take  place  in  the  circu- 
latory apparatus.  The  lungs  ^'S-  ^^l- 
become  the  organs  of  respira- 
tion, and  rapidly  increase  in 
capacity ;  the  pulmonary  artery 
dilates  to  give  passage  to  the 
blood  that  flows  to  them ; 
while  the  ductus  arteriosus  is 
obliterated,  in  order  to  isolate 
the  arterial  from  the  venous 
blood.  This  separation  of  the 
two  fluids  also  takes  place  in 
the  liver  by  the  atrophy  of  the 
ductus  venosus,  and  in  the 
heart  by  the  occlusion  of  the 
foramen  of  Botal ;  though, 
according  to  Goubaux,  that 
orifice  frequently  remains  open 
in  young  animals.  Its  persis- 
tence has  also  been  noted  in 
the  human  adult.  Notwith- 
standing the  presence  of  this 
foramen,  the  circulation  can- 
not be  much  disturbed ;  as 
when  the  heart  contracts,  the 

auricles  become  isolated  by  the  constriction  of  the  opening  and  the  raising  of  a 
valve. 

(Lymphatic  vessels  and  glands  are  found  at  an  early  period  of  foetal  life,  after 
the  blood-circulation  has  been  fully  established.  In  connection  with  these 
should  be  mentioned  the  prevertebral  hmno-lymph  glands,  which  are  best  observed, 
however,  in  the  adult  animal — and  particularly  in  the  Sheep  and  Ox.  They  are 
small  oval  or  lenticular  bodies,  about  the  size  of  a  mustard-seed,  and  are  found 
in  the  abdominal  and  pelvic  cavities  among  the  fat  and  connective  tissue,  between 
the  vertebral  column  and  peritoneum,  as  well  as  in  the  thorax,  in  the  middle  and 
posterior  mediastinum.  They  are  larger  in  Oxen  than  Sheep  ;  there  are  from 
three  to  four  hundred  in  the  latter.  They  are  supposed  to  be  the  source  of 
some,  at  least,  of  the  lymphoid  cells  and  non-nucleated  and  multi-nucleated 
corpuscles  which  occur  in  the  blood.) 


TRANSVERSE  SECTION  OF  THE  ADVANCED  EMBRYO  OF  A 
RABBIT,  SHOWING  THE  RELATIONS  OF  THE  HEART  WITH 
THE   LUNGS   AND   DIGESTIVE   TUBE. 

ht,  heart ;  pc,  pericardial  cavity ;  pl.p,  pleural  cavity ;  Ig, 
lungs  ;  al,  digestive  canal ;  ao,  aorta  ;  ch,  notochord  ;  rp, 
ribs;  st,  sternum;  sp.c,  spinal  cord. 


1046 


EMBRYO  LOQT. 


Fig.  582. 


A9  0 


FIRST    APPEARANCE   OF   THE   LUNGS. 

In  a  Fowl  at  four  days  ;  b,  at  six  days  ;  c, 
termination  of  bronchus  in  a  very  young 

Pig- 


Development  of  the  Respiratory  Apparatus. 

Observers -are  not  unanimous  as  to  the  development  of  the  lungs.  According 
to  Reichert  and  BischoflF,  they  arise  from  two  small  solid  cellular  masses  lying  on 
the  surface  of  the  anterior  portion  of  the  intestinal  canal.  These  become 
channeled  out  into  numerous  ramifying-  cavities  (by  the  deliquescence  or  fusion 

of  the  internal  cells),  which  communicate 
with  the  trachea.  Costa  states  that  they 
commence  by  a  median,  bud-like,  hollow 
process  that  opens  into  the  oesophagus. 
The  walls  of  the  communicating  aperture 
elongate  considerably,  and  at  a  later  period 
form  the  trachea  and  larynx  ;  while  the 
hollow  bud  divides  into  two  pyriform  sacs, 
each  of  which  becomes  broken  up  into  a 
multitude  of  subdivisions  to  constitute 
the  pulmonary  lobes,  with  their  vesicles 
and  infundibula. 

The  trachea  is  completed  by  the  development  of  the  cartilaginous  rings  in  the 
tube  that  binds  the  lungs  to  the  oesophagus.  They  appear  at  the  commencement 
of  the  third  month. 

The  larynx  is  developed  in  the 
^''g-  583.  same  manner  at  the  pharyngeal  open- 

ing.    It  is  always  somewhat  unde- 
fined during  youth,  and  its  definitive 
I*  volume  is    not  acquired   until   the 

period  of  puberty. 

The  thymus  gJand  appears  as  a 
process  of  the  respiratory  mucous 
membrane.  It  seems  to  be  formed 
at  the  larynx,  and  gradually  descends 
along  the  trachea  to  the  entrance  of 
the  thorax. 


Development  of  the  Digestive 
Apparatus. 

In  this  paragraph,  the  develop- 
ment of  the  alimentary  canal  will 
be  first  studied,  then  that  of  the 
organs  annexed  to  it. 

A.  Alimentary  Canal. — We 
have  seen  how  the  embryo,  in  be- 
coming incurvated,  divides  the  blasto- 
dermic vesicle  into  two  parts  which 
communicate  by  a  large  pedicle.  The 
external  portion    is    the    umbilical 


EMBRYO   OF   DOG,    rWENTV-FIVE    DAYS   AFTER   LAST 
COPULATION. 

0,  a,  Nostrils ;  h,  b,  eyes ;  c,  c,  first  visceral  arches, 
forming  the  lower  jaw ;  d,  d,  second  visceral 
arches  ;  e,  right  auricle  ;  /,  left  auricle  ;  g,  right 
ventricle;  h,  left  ventricle;  i,  aortic  bulb;  k  k, 
liver,  between  the  two  lobes  of  which  is  seen  the 
divided  orifice  of  the  omphalo-mesenteric  vein;  I, 
stomach ;  m,  intestine,  communicating  with  the 
umbilical  vesicle,  n  n ;  o  o,  corpora  Wolffiana;  pp, 
allantois ;  q,  q,  anterior  extremities ;  r,  r,  posterior, 
extremities. 


vesicle  ;  the  pedicle  is  the  omphalo- 
mesenteric duct,  and  the  inner  part  the  intestinal  cavity. 

The  latter  may  be  resolved  into  three  portions  :  the  anterior  intestine,  which 


TEE  F(ETU8.  1047 

forms  the  pharynx  and  oesophagus ;  the  posterior  intestine,  that  gives  rise  to 
the  rectum ;  and  the  middle  intestine,  which  becomes  the  stomach  and  in- 
testines. 

The  middle  intestine  appears  at  first  as  a  uniform  cylindrical  tube,  the 
diameter  of  which  is  afterwards  modified  to  constitute  the  organs  comprised 
between  the  oesophagus  and  rectum. 

1.  Mouth. — It  begins  by  a  depression  limited  by  the  maxillary  buds.  This 
blind  pouch  gradually  enlarges  inwardly,  and  proceeds  to  meet  the  pharynx, 
from  which  it  is  only  separated,  at  a  certain  period,  by  a  thin  membrane ;  this 
is  at  last  absorbed,  and  the  two  cavities  then  communicate.  Until  the  third 
month,  the  mouth  is  confounded  with  the  nasal  cavities  ;  at  this  time  the  palate 
appears,  and  this  eventually  isolates  them. 

2.  Tongue. — Appearing  at  first  as  a  small  prominence  on  the  maxillary 
buds,  the  tongue  is  completed  by  the  addition  to  it  of  a  bud  from  the  second 
branchial  arch.  Its  epithelium  and  glands  come  from  the  external  blastodermic 
lamina  ;  they  are  developed  in  the  third  and  fourth  months. 

3.  Pharynx  and  (Bsophagus. — These  two  organs  become  enlarged  and 
elongated  as  the  foetus  grows.  The  oesophagus  communicates  at  first  with  the 
trachea  ;  but  it  slowly  closes,  and  finally  separates  completely  from  that  canal. 

4.  Stomach. — This  is  formed  by  the  dilatation  of  the  anterior  part  of  the 
middle  intestine.  The  dilatation  is  fusiform,  and  its  largest  axis  longitudinal ; 
it  soon  incurvates,  and  its  longest  axis  is  then  transversal.  In  Ruminants,  the 
stomach  is  at  its  first  appearance  simple  ;  but  before  long  it  shows  grooves  on 
its  surface,  and  in  its  interior  septa,  as  in  the  normal  state.  During  foetal  life 
this  organ  is  small ;  but  after  birth,  when  solid  food  begins  to  be  taken,  it 
augments  rapidly  in  volume.  During  lactation  in  Ruminants,  there  is  remarked 
a  predominance  of  the  fourth  over  the  other  gastric  compartments  ;  but  im- 
mediately the  young  animal  commences  to  consume  fibrous  aliment,  the  rumen 
quickly  increases  in  size,  and  it  is  not  long  before  it  becomes  the  most  consider- 
able division. 

5.  Intestines. — The  intestinal  tube  is  primarily  of  a  uniform  calibre,  though 
in  a  short  time  there  can  be  distinguished  the  various  regions  of  which  it  is 
composed.  According  to  A.  Baer,  the  cfecum  is  early  seen  in  hoofed  animals, 
and  is  situated  in  the  vicinity  of  the  omphalo-mesenteric  duct.  This  duct 
detaches  itself  from  the  extremity  of  an  intestinal  loop,  which  is  drawn  towards 
the  umbilical  ring  ;  when  the  latter  is  becoming  atrophied  and  progressing 
towards  complete  obliteration,  this  loop  reascends  into  the  abdominal  cavity. 

The  intestines  are  smooth  on  their  inner  face  during  the  first  two  months  ; 
but  during  the  third  they  show  their  villosities  and  the  glands  of  Lieberkuhn. 
The  Brunnerian  and  solitary  glands  are  a  little  later  in  showing  themselves. 

6.  Rectum. — This  is  derived  from  the  posterior  intestine,  and  is  developed 
like  the  other  portions. 

7.  Anus. — Towards  the  caudal  extremity  of  the  foetus  is  observed  a  depres- 
sion, analogous  to  the  buccal  cid-de-sac.  This  gradually  deepens,  and  is  joined 
to  the  rectum  and  genito-urinary  organs.  Later,  it  is  separated  from  the  latter, 
and  then  belongs  exclusively  to  the  alimentary  canal. 

B.  Annexes  of  the  Alimentary  Canal. — These  are  the  salivary  glands, 
teeth,  liver,  pancreas,  and  spleen. 

1.  Salivary  glands. — These  are  developed  in  a  solid  cellular  bud,  which  is 
related  to  the  epithelium  at  the  commencement  of  the  digestive  apparatus.    This 


1 048  EMBR  YOLOG  Y. 

bud  increases,  and  at  the  same  time  is  hollowed  into  glandular  pouches.  The 
submaxillary  gland  is  the  first  to  appear ;  according  to  Bischoff,  it  is  entirely 
formed  in  the  foetus  of  a  Cow  only  an  inch  in  length.  The  parotid  gland  is  the 
last  to  be  formed. 

2.  Teeth. — These  organs  are  developed  in  the  interior  of  a  cavity,  named  the 
dental  folJich  or  sac,  by  means  of  the  elements  of  three  germs — one  belonging  to 
the  ivory,  another  to  the  enamel,  and  a  third  to  the  cementum. 

Follicle. — The  dental  follicle  is  an  oval  cavity,  with  walls  composed  of  two 
layers  ;  the  external  is  fibrous  and  complete  ;  the  internal — soft  or  gelatinous — is 
allied  at  the  bottom  to  the  ivory  germ.  The  latter  is  a  prominence  which  is 
detached  from  the  bottom  of  the  follicle,  and  has  the  exact  shape  of  the  tooth. 
Its  structure  comprises,  in  the  centre,  delicate  connective  tissue  provided  with 
vessels  and  nerves,  and  on  the  surface  a  layer  of  elongated  cells.  At  the  summit 
of  the  follicle,  facing  the  ivory  germ,  is  the  enamel  germ ;  it  is  exactly  applied 
to  the  dental  pulp,  which  it  invests  like  a  cap,  and  is  composed  of  a  small  mass 
of  mucous  connective  tissue  covered  by  a  layer  of  cylindrical  cells — the  ada- 
mantine  tissue  of  Renaut — joined  to  the  buccal  epithelium  by  the  gubernaculum 
dentis.  The  cementum  organ  manifestly  exists  in  the  Foal,  according  to  M. 
Magitot.  The  base  of  the  ivory  germ  has  been  found,  but  it  disappears  rapidly 
after  having  performed  its  function. 

How  are  the  different  parts  of  the  dental  follicle  developed  ?  When  the 
maxillary  arches  are  formed,  the  alveolar  borders  show  a  ridge  which  enters 
the  embryonal  tissue  of  the  jaws.  On  the  inferior  border  of  this  epithelial  ridge 
are  formed  buds  (enamel  organs),  in  number  equal  to  that  of  the  temporary  teeth 
— these  are  the  primitive  buds. 

While  these  buds — dependencies  of  the  octoderm — are  developing  towards 
the  interior  of  the  jaw,  there  appear  the  dental  bulbs  (ivory  organs),  which  arise 
from  embryonic  tissue  ;  these  grow  outwards  and  bury  themselves  in  the  summit 
of  the  enamel  organs,  so  as  to  form  a  cap  over  them.  Afterwards  the  wall  of 
the  dental  follicle  is  detached  from  the  base  of  the  bulb,  rises,  and  envelops  the 
two  germs  in  an  oval  sac. 

Magitot  and  Legros  have  remarked  in  the  embryo  of  a  Mare  that :  1.  At 
the  hundredth  day,  the  enamel  organs  of  the  incisiors  are  distinct,  and  are  detached 
from  the  epithelial  layer ;  the  follicles  of  the  molars  are  in  a  slightly  more  advanced 
state.  2.  At  one  hundred  and  ninety  days,  the  incisor  follicles  are  closed  ;  the 
molars  are  almost  in  the  same  state.  3.  At  two  hundred  days,  the  follicles  have 
attained  their  complete  development— which  precedes  by  some  days  the  appear- 
ance of  the  dentine  cap  ;  the  permanent  incisor  follicles  are  visible,  but  not  yet 
closed.  4.  At  two  hundred  and  twenty  days  the  temporary  follicles  are  very 
voluminous  ;  the  dentine  cap  is  already  considerable  ;  and  the  two  coronary  and 
radicular  cement  organs  are  in  place  and  quite  developed. 

Formation  of  the  ivory,  enamel,  and  cementum. — The  ivory  and  enamel  are 
developed  by  the  modification  of  the  elements  situated  at  the  surface  of  their  germ. 

It  has  been  shown  that  the  germ  of  the  ivory,  or  dental  pulp,  had  exactly 
the  form  of  the  future  tooth  ;  consequently  the  ivory  which  arises  from  its 
periphery  offers  the  shape  of  this  tooth.  The  ivory  {dentine)  is  constituted  by 
the  cells  of  the  germ,  which  elongate,  send  out  prolongations — the  dental  fibres 
— that  ramify  and  anastomose,  and  by  an  intercellular  substance  which  is  im- 
pregnated with  calcareous  matter,  is  moulded  around  these  fibres,  and  forms  the 
dental  canaliculi. 


THE  FCETUS.  1049 

The  enamel  is  derived  from  the  deep  cells  of  its  germ,  which  are  elongated 
and  prism-shaped,  and  are  calcified  on  becoming  applied  to  the  surface  of  the 
ivory. 

The  cementum  is  developed  at  the  expense  of  the  walls  of  the  follicle,  accord- 
ing to  the  mode  of  ossification  of  the  connective  tissue. 

Eruption. — As  the  ivory  is  formed,  the  tooth  increases  in  length  and  presses 
the  enamel  germ  upwards  ;  the  latter,  constantly  compressed,  becomes  atrophied, 
and  finally  disappears  when  the  tooth  has  reached  the  summit  of  the  follicle. 
In  the  same  way  the  young  organ  pierces  the  dental  follicle  and  gum,  and  makes 
its  eruption  externally. 

Such  is  the  mode  of  development  of  the  deciduous  teeth.  The  permanent 
ones  are  formed  in  the  same  manner. 

The  enamel  organ  proceeds  from  a  point  adjoining  the  summit  of  the  follicle 
of  the  temporary  tooth,  and  buries  itself  beneath  the  latter,  where  it  forms  the 
dental  bulb  and  the  walls  of  the  new  follicle.  The  follicles  of  the  three  last 
molars — which  are  permanent — arise  independently  of  those  of  the  temporary 
teeth.  The  bud  of  the  first  of  these  molars  springs  from  the  epithelial  ridge  on  the 
border  of  the  jaws,  the  buds  of  the  other  two  being  derived  from  the  first, 

3.  The  liver. — This  gland  commences  to  be  developed  very  early  in  all  the 
species.  It  appears  on  the  surface  of  the  duodenum  in  the  form  of  two  or  more 
buds,  according  to  the  number  of  lobules  in  the  adult  liver.  To  these  external 
buds  are  corresponding  internal  ones,  arising  from  the  intestinal  epithelium — 
that  is,  the  inner  lamina  of  the  blastoderm.  The  first  are  contained  in  a  layer  of 
the  mesoblast  that  separates  the  anterior 

aditus  of  the  pericardium  ;  they  grow  and        ^^^^^^^^|^^ 
envelop   the   omphalo-mesenteric   vein ; 
the  second  ramify  in  their  interior,  and 
form  the  system  of  biliary  canals. 

The  liver  grows  rapidly,  and,  towards 
the  third  month,  almost  entirely  fills  the 
abdominal  cavity  ;  at  a  later  period  its 
growth  is  less  marked,  although  at  birth 
it  is  yet  proportionally  larger  than  in  origin  op  the  liver  from  the  intestinal 
adult  life  wall  in  the  embryo  of  the  fowl,  on  the 

„  ■  „i  £    X  fourth  day  of  incubation. 

4.  Pancreas. — The  pancreas  first  ap-       „        ,  .  .   .. 

,.,      ,,  ,.  1       T      •      ii       ,-  a,Heart;  ft,  intestine;  c,  everten  portion,  giving 

pear,  hke  the  salivary  glands,  m  the  form        oHgin  to  liver;  d,  liver;  e,  portion  of  vitel- 
of  a  solid  cellular  bud,  which  afterwards        line  vesicle. 
is  channeled  into  ramescent  cavities. 

5.  Spleen. — According  to  Bischoff,  this  body  is  developed — during  the  second 
month — on  the  large  curvature  of  the  stomach.  Arnold  states  that  it  is  formed 
at  the  same  time  as  the  liver,  in  a  strip  extending  from  the  stomach  to  the 
duodenum.  It  subsequently  separates  from  the  pancreas  and  becomes  fixed  to 
the  stomach,  where  its  elements  assume  the  character  of  spleen-tissue. 

Development  of  the  Genito-Urinary  Apparatus. 

The  development  of  the  genital  organs  is  related  to  that  of  the  urinary  organs, 
as  the  apparatus  they  form  have  some  parts  in  common. 

Immediately  after  the  formation  of  the  intestines,  the  genito-urinary  organs 
are  furnished  by  the  Wolffian  bodies.     These — also  named  i[\Q primordial  kidneys 


1050 


EMBRYOLOGY. 


Fig.  585. 


and  bodies  of  OTcen — are  glandular  in  structure,  and  extend  in  front  of  the  vertebral 
column  from  the  heart  to  the  pelvis.  They  are  composed  of  small  transverse 
canals,  filled  with  a  whitish  fluid,  which  enter  a  common  excretory  duct  that  lies 
parallel  to  the  spine,  and  opens  inferiorly  into  that  portion  of  the  allantois  which 
becomes  the  bladder. 

The  Wolffian  bodies  are  placed  behind  the  peritoneum,  and  are  attached  by 
two  serous  folds  :  an  anterior — the  diaphragmatic  liyament — and  a  posterior — the 
lumbar  ligament  of  the  corpora  Wolffiana.  The  organs  furnish  a  liquid  analogous 
to  the  urine  ;  though  it  is  not  long  before  their  secretion  undergoes  great  modi- 
fications ;  indeed,  these  bodies  soon  atrophy,  and  disappear  more  or  less  rapidly, 
according  to  species.  One  portion  serves  for  the  development  of  the  genital 
organs ;  the  other  gives  rise  to  organs  the  signification  of  which  is  unknown — 
such  as  the  organ  of  Rosenmiiller — which  is  very  developed  in  the  Mare,  and  the 
canals  of  Gaertner,  visible  in  the  Cow  and  Rabbit  (Mare  and  Pig). 

A.  Urinary  Organs. — We  have  seen  above  how  the  allantois  is  derived 
from  the  blastodermic  lamina  ;  it  has  now  to  be  stated  that  the  bladder  is  derived 
from  the  allantois.  This  reservoir  is  the  result  of  the  dilatation  of  the  abdominal 
portion  of  the  allantois.  During  foetal  life,  the  bladder  is  extended,  by  the 
urachus,  to  the  umbilical  ring  ;  but  after  birth  the  urachus  is  obUterated,  and 
the  bladder  is  withdrawn  into  the  pelvic  cavity.  Hereafter  we  shall  study  the 
urethra. 

The  kidneys  appear  a  long  time  after  the  Wolffian  bodies,  in  the  shape  of  two 
blind  pouches  constituted  by  a  pushing  back  of  the  wall 
of  the  excretory  duct  of  that  body.  These  little  cids-de- 
sac  ramify,  and  are  afterwards  replaced  by  solid  buds,  in 
the  interior  of  which  are  developed  the  uriniferous  tubes 
and  Malpighian  bodies.  According  to  certain  observers, 
the  kidneys  subsequently  communicate  with  the  ureters, 
which  are  developed  separately  in  the  middle  layer  of 
the  blastoderm  (for  further  details,  see  Book  IV.,  p.  573). 
(In  the  female,  the  Wolffian  bodies  do  not  entirely 
disappear ;  the  canals  of  Gaertner  and  the  bodies  of 
Eosenmiiller,  situated  in  the  broad  ligaments,  between 
the  ovaries  and  Fallopian  tubes,  are  their  remains  in 
adult  life  ;  traces  of  them  are  also  found  in  the  male,  near 
the  head  of  the  epididymis,  where  they  constitute  the  vasa 
aherrans  of  the  testicles.  The  supra-renal  capsules  are 
very  large  in  the  Equine  foetus,  being  nearly  one-half  the 
size  of  the  kidneys.) 

B.  Genital  Organs. — The  genital  apparatus  of  the 
male  and  female  are  at  first  very  much  alike  ;  indeed, 
during  a  certain  period  it  is  impossible  to  distinguish 
the  sexes  ;  so  that  some  authorities  have  proposed  to  term 
this  period  of  development  the  "  indifferent  state  of  the  genital  organs."  Later, 
the  sexes  are  defined  ;  and  this  period  of  development  may  be  studied  in  the 
internal  and  external  organs. 

1.  Indifferent  state  of  the  internal  genital  organs. — Towards  the  sixth  week, 
there  is  observed  on  the  lower  face,  and  near  the  inner  border  of  the  Wolffian 
bodies,  a  little  white  cord,  which  increases  in  volume  and  maintains  almost  the 
same  position.     This  new  organ  is  the  genital  gland,  which  is  attached  to  the 


STATE  OF  THE  GENITO- 
URINARY APPARATUS  IN 
THE  EARLY  EMBRYO  OF 
THE    BIRD 

a,  Corpora  Wolffiana ;  6,  6, 
their  excretory  ducts; 
c,  kidneys;  d,  ureter; 
e,  e,  testes. 


TEE  FCETU8.  1051 

Wolffian  body  by  serous  folds,  and  is  formed  by  a  mass  of  young  cells  sustained 
by  an  enveloping  membrane. 

The  development  of  this  gland  is  accompanied  by  the  formation  of  the 
genital  or  MuUer''s  duct,  which  is  seen  to  the  inside,  and  in  front  of,  the  "Wolffian 
duct.  Miiller's  duct  is  at  first  a  solid  cellular  column,  which  afterwards  becomes 
a  canal ;  it  terminates  above  in  a  blind  pouch,  and  opens,  below,  into  the  bladder, 
near  the  Wolffian  duct,  which  is  formed  at  the  same  time. 

The  stroma  of  the  genital  glands  in  the  two  sexes,  is  the  seat  of  a  differentia- 
tion that  gives  rise  to  a  system  of  reticulated  solid  cords,  called  the  sexual 
cords.  Its  surface  is  covered  by  an  epithelium,  which  is  continuous  with  that 
of  the  peritoneum,  but  so  specialized  here  as  to  merit  the  name  of  f/erm- 
epithelium. 

The  sexual  specialization  is  produced  in  the  following  manner  : —  ^ 

a.  In  the  male,  by  the  evolution  of  the  sexual  cords,  or  tubuli  seminiferi. 
The  testicle  is  completed  by  the  annexation  of  the  anterior  region  of  the 

Wolffian  body,  which  forms  the  head  {globus  major)  of  the  epididymis,  while 
the  tail  (or  globus  minor),  vas  deferens^  and  ejaculatory  duct,  are  derived  from 
the  Wolffian  duct.  Lastly,  the  vesiculce  seminales  and  the  origin  of  the  urethra 
are  formed  by  the  posterior  extremity  of  Miiller's  ducts,  which  join  and  open 
into  the  uro-genital  sinus,  as  the  very  short  canal  is  named  which  communicates 
between  the  bladder  and  cloaca. 

The  developed  testicle  remains  in  the  abdominal  cavity,  or  descends  through 
the  inguinal  canal  into  the  scrotum.  The  mechanism  of  this  descent  has  been 
already  explained. 

(It  may  be  necessary  here  to  state  that,  in  the  Equine  species,  the  testicles 
do  not  usually  descend  into  the  scrotum  until  some  time  after  birth — about  six 
months  ;  while  in  other  animals  they  reach  that  sac  during  foetal  life.  In  the 
Bovine  species,  the  testes  are  in  the  scrotum  about  the  twentieth  week  of  gesta- 
tion, and  in  the  Sheep  and  Goat  about  the  fifteenth  week  ;  indeed,  it  has  been 
observed  that  in  all  Ruminants  their  descent  is  effected  before  the  skin  is  covered 
with  hair.  In  the  Carnivora,  they  are  usually  in  the  scrotum  a  few  days  before 
birth.) 

b.  In  the  female,  the  sexual  specialization  is  produced  by  a  process  of  the 
germ-epithelium,  which  results  in  the  establishment  of  an  ovigenous  layer.  The 
Fcdlopian  tube  and  its  pavilion  are  formed  by  the  anterior  part  of  Miiller's  duct, 
the  extremity  of  which  shows  a  small  linear  orifice.  The  uterus  and  vagina  arise 
from  the  posterior  part  of  Miiller's  ducts.  These  lie  beside  each  other,  and 
end  by  joining  behind  to  constitute  a  single  canal ;  the  two  divergent  portions  of 
these  canals  comprised  between  the  point  of  fusion  and  the  Fallopian  tubes  form 
the  uterine  cornua. 

The  uterus  and  vagina  are  at  first  placed  end  to  end,  without  any  apparent 

>  At  the  same  time  that  the  sexual  specialization  of  the  genital  gland  is  affirnfed  in  the 
ovary  and  testicles,  the  glands  themselves  afford  exact  evidence  of  the  opposed  sexualities.  In 
the  testicles,  the  germ-epithelium  is  the  seat  of  an  evolution  that  gives  rise  to  the  primordial 
ova  which  Laulanie  has  observed  in  the  fcetus  of  the  Cat,  measuring  from  -7  to  -12  m.  In  the 
same  animal  species,  this  author  has  noted — with  regard  to  the  fcetal  ovary — the  connections 
between  the  primitive  sexual  cords  and  the  tubes  of  the  "Wolffian  body,  establishing  the 
homology  of  the  first  tubuli  seminiferi.  A  demonstration  has  therefore  been  given  for  the  first 
time,  of  a  real  organic  hermaphrodism  of  the  sexual  glands,  and  from  this  arises  tlie  interesting 
notion  that  the  sexuality  of  the  individual  has  been  preceded  by  a  period  of  indifference  and 
a  period  of  bisexuality. 


1052  EMBRYOLOGY. 

separation  ;  but  towards  the  sixth  month  the  neck  of  the  uterus  commences  to 
be  defined. 

2.  Indifferent  state  of  the  external  genital  organs. — The  intestine  is  terminated 
by  the  cloaca — a  cavity  into  which  the  digestive  canal  and  bladder  open  by  the 
uro-genital  sinus.  This  confusion  quickly  ceases  by  the  development  of  a  trans- 
verse septum  that  divides  the  cloaca  into  two  compartments — the  anal  opening 
and  the  uro-genital  aperture.  At  the  inferior  end  of  the  latter  appears  the  genital 
tubercle — the  rudiment  of  the  penis  or  clitoris,  and  wliich  is  surrounded  by 
cutaneous  folds — the  genital  folds.  This  tubercle  increases  in  volume,  and  has 
a  furrow  passing  from  betind  to  before.  Up  to  this  moment  it  is  impossible  to 
distinguish  the  sexes. 

Development  of  the  external  genital  organs  of  the  male. — The  male  sex  is  marked 
by  the  rapid  development  of  the  genital  tubercle,  which  becomes  the  penis — its 
extremity  enlarging  to  constitute  the  glans.  The  genital  furrow  closes  posteriorly, 
and  forms  the  urethra.  The  genital  folds  draw  towards  each  other  below  the 
penis,  unite  in  the  middle  line,  and  thus  produce  the  scrotum.  Owing  to  these 
modifications,  the  digestive  apparatus  is  completely  separated  from  the  genito- 
urinary organs,  and  the  urethral  canal  is  connected  with  the  bladder  and  the 
excretory  ducts  of  the  testicle. 

Development  of  the  external  genital  organs  of  the  female. — The  indifferent  state 
of  the  genital  organs  is  readily  succeeded  by  the  feminine  type.  The  uro-genital 
sinus  forms  the  vulvar  cavity  or  vestibulum  of  the  vagina,  which  is  so  marked 
in  the  lower  animals.  The  genital  tubercle  becomes  the  clitoris ;  the  genital 
furrow  closes  at  a  certain  part  to  constitute  the  perinasum ;  while  the  genital 
folds  form  the  labia  of  the  vulva.  The  mammae — dependencies  of  the  generative 
organs— appear  after  the  first  month  of  uterine  life. 


INDEX. 


PAGE 

PAGE 

Abdomen  

.       450 

Anatomy,  comparative 

I 

Abdominal  aorta          . 

609 

ib. 

cavity 

450 

descriptive 

ib. 

.       455 

ib. 

differential  characters  ii 

I         .          lb. 

general 

ib. 

divisions  of 

450 

ib. 

.        299 

ib. 

form  of 

451 

physiological 

ib. 

lining  membrane  of 

.       452 

regional 

ib. 

.       451 

ib. 

reservoirs    . 

565 

surgical     . 

ib. 

rings  of 

.       303 

typographical 

ib. 

.       450 

ib. 

Abdominal  salivary  gland 

.       555 

ib. 

Abomasum 

470 

Ancyroid  cavity 

803 

interior  of. 

*. 

Andersch's  ganglion 

833 

structure  of 

ib. 

Aneurism 

.       616 

Absorbent  vessels 

713 

Angiology 

'.         '.        C 

J92,  583 

Accessory  portion  of  visual  appara 

tus      .        938 

Animal  amidon  . 

.       497 

Acervulus. 

.        773 

Annular  cartilage 

281 

Adipose  cushion  of  ear           .          , 

.        958 

protuberance 

769 

Adrenals    .... 

.        578 

Annul  us  albidus 

930 

Affluents  of  thoracic  duct 

.        724 

589 

Aggregate  follicles 

475 

Anomalies  in  arteries 

.       605 

Air-cells  of  lungs 

549 

Anorchidism 

.       962 

Air-chamber  ot  egg       .          . 

.      1009 

Ansiform  tube  of  Henl 

572 

Alimentary  canal 

447,  455 

Anterior  antibrachial  i 

egion 

323 

Allantoid  fluid    . 

.      1021 

aorta 

^ 

d44 

Allantois  .          .          .         .101 

6,  1017,  1019 

biachial  region 

\ 

317 

chorial 

.      1020 

771 

.      1021 

femoral  or  crural  region 

.       348 

Alveoli  of  glands 

460 

mediastinum 

.       543 

lymphatic  . 

.        719 

patellar      .... 

348 

Alveolo-dental  periosteum     . 

.       414 

peduncles  of  conarium 

772 

Alveus       .... 

792 

tibial  region 

362 

Amnii,  liquor     . 

.      1019 

white  commissure  of  brain     . 

774 

Amnion      .... 

1017,  1019 

Anus          ..... 

.       484 

Amniotic  lamina 

.      1019 

1047 

Amphiarthroses  . 

.        177 

of  Rusconi 

.     1007 

*. 

Aorta 

608 

Ampulla  of  Vater 

499,  503 

anterior      .... 

.       644 

Amygdalae 

.       401 

common      .... 

608 

Amygdaloid  cavity 

ib. 

— : —  comparison  of     .          .          , 

623 

Anastomoses       .           . 

.        602 

644 

by  arches  . 

ib. 

differential  characters  in 

621 

ib. 

carnivora'    . 

622 

ib. 

pig  .  . 

ib. 

convergent 

ib. 

621 

ib. 

611 

transverse  communicating 

ib. 

posterior     .... 

609 

.       805 

preparation  of     . 

610 

Anatomical  elements 

3 

612 

Anatomy 

1 

Aortae,  primitive 

1041 

anthropotomy     . 

.•6. 

Aortic  heaiT       .... 

590 

69 

1054 


INDEX. 


PAGE 

Aponeurosis 

232 

Arteries,  relations        .... 

322 

structure     .... 

containing            .          .          .          . 

239 

termination 

crural 

301 

302 

abdominal,  anterior 

349 

posterior     .... 

gluteal        

243 

972 

accessory  thyroid 

ih. 

anterior  cerebellar 

superficial 

ib. 

plantar       ....         3 

31,  371 

mesenteric  .... 

tibial          

362 

radial          .          .          .          . 

Apparatus            .... 

6 

tibial           .... 

circulatory,  in  mammalia 

582 

arteria  corporis  callosi.          . 

734 

396 

asternal 

511 

atloido-muscular 

generative 

959 

738 

posterior     .          .          .          . 

924 

axillary 

respiratory,  in  mammalia 

517 

in  birds       . 

557 

899 

949 

basilar 

taste,  of     . 

922 

brachial 

899 

urinary       .          •          .          . 

568 

vision,  of    . 

925 

buccal 

Appendix  auricularis    . 

586 

bulb 

Aqueduct  of  Fallopius 

952 

caecal 

of  Sylvius  .... 

775 

Aqueous  humour 

938 

left 

membrane  of 

ih. 

right           .          .          .          . 

Arachnoid  membrane  . 

751 

carotid,  common 

752 

collateral  branches 

751 

structure    . 

ib. 

790 

external      .          .          .          . 

Arantius,  nodule  of      . 

589 

internal      .          .          .          . 

duct  of       .          .          .          .105 

7,  1044 

Arbor  vitae  cerebelli     . 

781 

cavernous  

Arciform  fibres  of  bulb 

777 

centralis  retinae  .          .          .          . 

Arch  of  aorta      .... 

609 

hamal        .... 

167 

ischial        .... 

.        133 

ischiatic     .... 

ib. 

cerebral,  anterior 

neural        .... 

167 

middle        .          .          .          . 

pharyngeal 

.      1039 

Arcus  aortse        .... 

.      1041 

cerebro-spinal     .          .          .          . 

Arm,  bones  of     . 

.        101 

cervical,  deep      .          .          .          . 

Arms  of  pelvis  of  kidney 

.       571 

Arnold's  ganglion 

824 

Arterial  zones  of  heart 

.        592 

cervico-muscular 

Arteriae  helicinae 

974 

transverse  ... 

vertebralis 

.      1041 

ciliary 

Arteries     ..... 

600 

.       602 

anomalies     . 

.       605 

posterior,  of  shoulder    . 

.       601 

direction 

ib. 

.       607 

division 

.       600 

middle        .          .          .          . 

form,  particular    . 

ih. 

ccEliac         .... 

general  considerations  . 

ih. 

form   .          .          . 

ih. 

left  or  retrograde 

■ injection      . 

.       606 

collateral  of  the  cannon          .         6 

.       603 

branches     .          .          .          . 

.       601 

of  the  digit 

preparation . 

.       6«>6 

colon,  first  of  small  colon 

INDEX. 


1055 


Arteries,  coraco-radialis        .         , 

PAGE 
651 

Arteries,  internal  mammary 

PAGE 

647 

620 

maxillary   . 

672 

coronary    ....         6 

09,  670 

pudic 

624 

638 

625 

627 

of  male 

624 

cremasteric 

620 

interosseous,  of  forearm 

652 

629 

anterior 

654 

cubital       .... 

650 

metacarpal. 

653 

dental,  inferior    . 

672 

ib. 

superior 

675 

intestinal,  small . 

616 

612 

ischiatic     .... 

625 

digital        .... 

636 

labial,  inferior     . 

.       670 

direct  colic 

617 

ib. 

dorsal         .... 

645 

lachrymal  .... 

674 

anterior  of  penis 

632 

640 

625 

652 

615 

lateral  coccygeal 

625 

elbow,  external  collateral 

650 

ib. 

internal  collateral 

ib. 

ib. 

619 

middle 

612 

epicondyloid 

650 

terminal  branches 

625 

epigastric  .... 

632 

left  colic    .... 

617 

67,  671 

lingual       .... 

669 

collaterals  . 

ib. 

612 

external  pudic     . 

632 

632 

facial          .... 

667 

648 

femoral      .... 

631 

internal      . 

647 

femoro-popliteal . 

634 

672 

first  artery  of  floating  colon  . 

618 

mastoid      .... 

663 

613 

maxillary,  external 

667 

gastro-epiploica  dextra 

615 

internal 

672 

14,  615 

maxillo-muscular 

670 

667 

673 

gluteal       .... 

626 

mesenteric,  great 

616 

great  meningeal . 

673 

anastomoses 

618 

616 

616 

posterior  of  thigh 

633 

617 

testicular  .          ... 

620 

616 

672 

of  right  fasciculus 

617 

974 

innominate  branches 

618 

hepatic       .... 

615 

small 

ib. 

44,649 

636 

650 

middle  cerebral   . 

665 

deep  .... 

ib. 

—coccygeal    . 

626 

humeralis  profunda      . 

650 

612 

629 

664 

643 

muscular,  deep    . 

633 

differential  characters  ii 

1       640 

great  anterior      . 

ib. 

623 

ib. 

629 

ib. 

differential  characters  ii 

1       628 

nasal          .... 

675 

617 

626 

627 

occipital     .... 

662 

626 

collateral  branches 

663 

ib. 

occipito-muscular 

ib. 

dental 

672 

612 

cervical 

648 

omental     .... 

615 

640 

omphalo-mesenteric      . 

1041 

ib. 

673 

infra-scapular     . 

649 

ovarian       .... 

621 

labial 

670 

palatine      .... 

675 

969 

palato-labial        ...         6 

72,  675 

innominata 

644 

615 

innominate  branches  of  great  mesen 

pectoral     .... 

647 

teric    .... 

618 

pedal          .... 

636 

613 

perforating 

ib. 

intercostal 

611 

638 

665 

pharyngeal 

669 

iliac. 

623 

phrenic      .... 

612 

1056 


INDEX. 


PAGE 

Arteries,  plantar          ....       635 

Arteries,     thoracic,     internal     teiminal 

cushion 

638 

branches 

635 

640 

popliteal    . 

634 

transverse-cervical 

posterior  abdominal 

632 

transverse  of  face 

671 

communicating    . 

665 

ulnar          .          .          . 

deep  temporal 

672 

umbilical   . 

625 

652 

utero-ovariaa 

tibial 

634 

vaginal 

.•6. 

vasa  brevia 

ib. 

intestini  tenuis    . 

650 

preplantar  ungual 

639 

vertebralis 

prepubic    . 

631 

vesico-prostatic   . 

prescapular 

649 

Arthrodia . 

prevertebral 

663 

Arthrology 

633 

Articular  cartilages     . 

673 

pulmonary 

607 

Articulations 

preparation  of 

.•6. 

in  general    . 

pyloric 

615 

radial,  anterior   . 

651 

nomenclature 

posterior     . 

652 

anterior  limbs,  of 

radio-palmar 

653 

atlo-axoid  . 

.       663 

renal 

.       619 

reticulum,  artery  of 

621 

17,  663 

carpo-metacarpal 

right  colic 

617 

rumen,  superior  of 

621 

ib. 

sacral,  lateral      . 

625 

costo-vertebral    . 

sacra  media 

612 

coxae 

saphena     . 

.       633 

scapulo-humeral 

649 

small  mesenteric 

618 

femoro-tibial 

intestine     . 

.       616 

foot  . 

small  testicular 

.       620 

head 

ih. 

675 

spinous 

.    ID  — 

.       673 

interchrondral     . 

spiral 

.    ■■».  • 

.       651 

interhyoideal 

splenic 

.       613 

675 

.       645 

first  . 

subcutaneous  abdomim 

[l 

.       632 

second 

.       670 

third 

667 

subsaci'al    . 

.       625 

intervertebral     • 

subscapular 

.        649 

ischio-pubic 

subzygomatic      . 

.        671 

laryngeal  cartilages,  ol 

633 

671 

occipito-atloid     . 

superior  dental    . 

.       675 

pedal 

supermaxillo-dental 

ib. 

pelvic 

supra-scapular    . 

.       649 

posterior  limbs    . 

674 

temporal   . 

671 

deep  anterior 

.       673 

sacro-iliac 

posterior 

ib. 

scapulo-humeral 

superficial 

.       671 

tarsal 

.       620 

small 

ib. 

thoracic,  external 

.       648 

inferior 

t6. 

i 

■         internal      . 

.       647 

tibio-fibular 

. 

INDEX 


1057 


PAGE 

Articulations,  tibio-tarsal     . 

221 

Bones,  nerves                .          .          .          . 

Arytsenoid  cartilages   . 

530 

number 

Ascending  frontal  convolution 

786 

nutrition 

Auditive  scala    .... 

950 

Auditory  apparatus     . 

947 

regions 

Auricles    ....           583,  5 

86,  589 

relative  form 

Auricular  or  conchal  region 

280 

Auricular  facet  .... 

128 

situation 

586 

Auriculo-ventricular  openings       .         5 

88,  590 

in  birds 

zones           .          r 

593 

anterior  maxillary 

Axile  bodies        .... 

901 

astragalus 

Axillary  region  .... 

292 

atlas 

Axis,  cceliac         .... 

613 

axis  , 

cylinder     .          .          .          ,          . 

740 

calcaneus    . 

of  arteries  . 

601 

calcis 

capitatum 

Baccated  fibres  of  tooth 

413 

Bacillary  layer  of  retina 

934 

carpus 

Balbiani's  vesicle 

1005 

cervical  vertebrae 

BandofReil       .... 

771 

Barbs 4 

00,  437 

coccyx 

Bars  of  hoof       .... 

915 

costa; 

Bartholine,  glands  of  . 

1000 

Basement  membranes  .          .          .          . 

5,393 

cuboid 

Basilar  membranes      . 

951 

cuneiform  . 

process  of  os  pedis 

116 

Bauhini,  valvula 

473 

dorsal  vertebra 

Bellini's  tubes     .... 

571 

ethmoid 

Bichat,  fissure  of          .          .          . 

784 

Bicipital  tuberosity     . 

317 

fibula 

Bicuspid  valve  .... 

590 

first  metacarpal 

Biflex  canal         .... 

901 

Biliary  ducts      .... 

498 

great  cuneiform 

Bipolar  nerve-cells 

740 

hamatum   . 

Bizzero's  cells     .... 

18 

Bladder     .          .          ... 

575 

humerus    . 

attachments 

ih. 

hyoid 

7,  1050 

■ form           .... 

575 

incisive 

• functions   .... 

578 

incus 

interior      .... 

576 

inferior  maxillar 

575 

-; relations    .... 

ib. 

576 

lachrymal  . 

575 

large  cuneiform 

Blastema 

393 

lumbar  vertebrae 

Blastoderm,  formation  of      . 

1007 

lunare 

ih. 

magnum     . 

Blastodermic  vesicle    . 

1007 

malar 

Blastopore          .... 

ib. 

malleus 

Blind  spot           .... 

936 

maxillary,  inferi 

)r 

Blood 

583 

superior 

Bones,  in  general 

7 

metacarpals 

13 

metacarpus 

blood-vessels 

18 

metatarsus 

cavities 

15 

middle  cuneiform 

cells  of 

16 

conformation,  internal  . 

15 

navicular  . 

development 

19 

occipital     . 

13 

OS  coronae  . 

eminences    . 

14 

innominatum 

*. 

orbiculare 

• general  principles 

11 

imprints 

14 

penis     . 

■ internal  conformation     . 

15 

palatine     . 

lymphatics  . 

18 

parietal 

medulla        .          .          . 

ih. 

patella 

, 

names 

12 

pedal 

. 

1058 


INDEX 


Bones,  pelvic 
penial 

peroneus 

pisiform 

premaxilla. 

prominens 

pterygoid 

pubis 

pyramidal  , 

radius 

ribs  . 

sacrum 

scaphoid  of  carpus 

of  tarsus 

scooping-bone 

second  phalanx 

sesamoids  . 

small  cuneiform 

small  sesamoid 

sphenoid    . 

stapes 

sternum 

styloid 

supercarpal 

• superior  maxillary 

supermaxilla 

tarsus 

temporal    • 

. third  phalanx 

tibia. 

■  trapezium. 
trapezoides 

tricuspid    . 

. turbinated 

■ ulnar 

■ unciform    . 

vertebra  dentata 

prominens 

tricuspid 

vertebse 

cervical 

coccygeal 

dorsal 

lumbar 

^—  vomer 

zygomatic  . 

Botal,  foramen  of 
Bourrelet  . 
Bowman's  capsule 
Brachial  bulb  . 
Brachio-rachidian  bulb 
Brain  (see  Encephalon) 
Bristles     . 

Bronchi     . 

cartilages  . 

disposition.  . 

form 

glands 

relations     , 

structure  . 

volume       .  . 

Bronchial  cartilages     . 

glands 

tubes 

Bruch,  membrane  of   . 
Brunner's  glands 
Buccal  mucous  membrane 
Bulbi  fornicis 
vestibuli    . 


FACE 

127 

980 

142 

108 

65 

30 

69 

128 

110 

103 

94 

39 

110 

147 

526 

115 

ib. 

148 

117 

56 

954 

92 

79 

108 

63 

ib. 

144 

59 

115 

140 

110 

ib. 

30 

73,  520 

105 

110 

28 

30 

i6. 

24 

27 

41 

32 

36 

74 

69 

589,  1042 
911 
572 
756 
ib. 
763 
905 
539 
540 
359 
540 
729 
540 
ib. 
ib. 
ib. 
729 
540 
931 
471 
398 
770 


Bulb  of  ovary     . 

of  plantar  cushion 

of  urethra  . 

Bui  bus  aortae 

olfactorius. 

Burdach,  column  of 
Bursse,  serous     . 

Caducous  teeth  , 
Caecum 

of  Morgagni 

pharyngeal 

Calamus  scriptorius 
Calcareous  powder  of 
Calices 

Calyciform  papillae 
Callosal  convolution 
Calloso-marginal  fissure 
Canal,  biflex 

ciliary 

Cloquet,  of 

Font  ana,  of 

Ga;rtner,  of 

Haversian  . 

hygrophthalmic 

inguinal 

Jacobson,  of 

perivascular 

Schlenim,  of 

spinal 

Steno,  of    . 

Sylvius,  of 

Canalis  hyaloideus 
Canine  teeth 
Canthi  of  eyelids 
Capillaries 
Capillary  system 
Capsular  ligaments 
Capsule  of  brain. 

of  Glisson  . 

of  lens 

Capsules,  supra-renal 
Ca))ut  gallinaginus 
Cardiac  cavity    . 

ligament    . 

oririce 

septum 

Carpal  sheath 
Carpus 

articulations 

bones 

movements 

Cartilage   . 

of  the  tongue 

Cartilages,  complementary 

incrustation 

interarticular 

interosseous 

stratiform 

annular 

cariniform 

conchal 

costal 

ensiform     . 

mterarticular  of 

scutiform   . 

semilunar  . 

Wi-isberg,  of 

xiphoid 


estibule 


jaw 


fibro- 


INDEX. 


1059 


PAGE 

PAGE 

Caruncula  lachrymalis 

.        945 

Chordae  vocales 530 

sublingualis          .          .          . 

.    440  : 

Willisii       . 

eaij 

Cauda  equina      .          .          .          . 

.        853    ! 

Chorial  plates     . 

1019 

Caudate  nucleus. 

792,794    ! 

Chorion      . 

1018 

Cava,  vena,  anterioi-     .          .          . 

.       686 

definitive   . 

t6. 

posterior    .          .          .          . 

703 

development 

ib. 

Cavernous  sinus. 

.       692 

frondosum 

1027 

Cavities 

15 

primitive   . 

1018 

Cell-germs          .          .          .          . 

.       903 

ib. 

Cells 

3 

serotina      . 

1027 

multiplication  of  . 

»6. 

structure    . 

1018 

16 

Choroid  membrane  or 

coat    . 

929 

connective            .          .          , 

4 

anterior 

930 

great  pyramid     . 

.       796 

posterior 

ib. 

lb. 

931 

hepatic       .          .          .          . 

497 

plexus,  cerebral 

779,7 

89,  793 

medullary 

4 

930 

4.740 

Chyle 

582 

olfactory    . 

523,  925 

Cicatricula 

1009 

prickle       .          .          .          . 

.        903 

Cilia 

943 

.       782 

Ciliary  body 

30,  932 

Sertoli,  of . 

964 

canal 

931 

small  pyramid     . 

.        796 

ib. 

supporting 

.       925 

ligament     . 

30,  931 

Cementum           .          .          .        4 

14,  415,  1048 

processes    . 

ib. 

Central  canal  of  spinal  cord  . 

.       757 

930 

Central  sublobular  veins 

.       498 

Ciliated  epithelium 

393 

Centres  of  ossification 

20 

Circulation,  adult 

582 

Centrifugal  conductibility     . 

744 

foetus 

1042 

nerves        .          .          .          . 

ib. 

Circulatory  apparatus 

582 

Centripetal  conductibility    . 

ib. 

in  birds 

734 

ib. 

Circulus  venosus  orbiculi  ci! 

iaris 

931 

Centrum    .... 

.       167 

Circumvallate  papillae 

02,  923 

ovale  of  Vic-d'Azyr      . 

.       795 

Cistern  of  Pecquet 

721 

Cerebellar  crura 

.       771 

Clark,  vesicular  column  of 

761 

peduncles  . 

767 

Claws 

921 

ventricle    . 

771,  776,  781 

Clefts,  pharyngeal 

1039 

.      1034 

Clitoris      . 

995 

Cerebellum 

763,  778 

ib. 

external  conformation  . 

.        779 

Closed  follicles    . 

407 

.        781 

Coat 

< 

)05,  907 

Cerebral  hemispheres  . 

785 

Coccygeal  gland 

886 

767,  770 

272 

trigonum    . 

.        791 

nerves 

859 

790 

vertebras     . 

41 

vesicles 

.     1033 

Cochlea      . 

948 

Cerebro-spiiial  axis 

.       747 

.       950 

.        804 

Cceliac  axis 

.       613 

Cerebrum  .... 

.        783 

Cohesion    . 

.       395 

convolutions 

.       785 

Colic  mesentery 

. 

1:54.  483 

external  conformation  . 

.        783 

Collateral  scala. 

.       951 

783,  784 

vessels 

.        (i03 

structure    . 

.       793 

Colon 

479 

Cerumen    .... 

957 

double 

.       481 

Ceruminous  glands 

ib. 

attachments 

.       482 

Cervical  ganglia 

887 

481 

ib. 

ib. 

vertebrae    . 

27 

ib. 

Cervix  of  bladder 

575 

functions     . 

.       483 

of  uterus   . 

990,  992 

length 

481 

Chambers  of  the  eye    . 

.       926 

ib. 

Cheeks       .... 

.       398 

483 

.        399 

small 

ib. 

.        398 

attachment 

ib. 

Chestnuts  .... 

907,  922 

lb. 

Chiasma  of  optic  nerves 

770 

ib. 

Chorda  dorsalis  . 

.      1013,  1032 

interior 

ib. 

Chordae  longitudinales 

790 

ib. 

tendinae 

.       588 

1 relations 

. 

iO' 

1060 


INDEX. 


PAGE 

PAGB 

Colon,  small,  structure 

483 

Comparison     of,     nerves,     great     sym 

Colostrum            .... 

999 

pathetic 

886 

Columella            .... 

948 

881 

Columnae  carnse .          .          .          .         f 

88,  591 

oesophagus 

450 

588 

pancreas     .... 

510 

rugosae       .... 

994 

446 

Columnar  epithelium   . 

393 

salivary  glands   . 

440 

Columns  of  spinal  cord           .          .         7 

57,  761 

scapulo-humeral  articulation 

195 

Commissures  of  frog    .          .          . 

917 

510 

of  inguinal  canal. 

303 

spinal  cord 

763 

397 

stomach     .... 

471 

of  nostril    .... 

518 

119 

of  optic  nerves     . 

810 

97 

757 

thymus  gland      . 

556 

of  vulva     .... 

995 

thyroid  gland      .          ,          . 

.•6. 

Common  aorta   .... 

608 

trachea      .... 

552 

Comparison  of  abdominal  cavity    . 

458 

urinary  apparatus 

581 

of  abdominal  limb 

151 

veins           .... 

712 

of  annexes  of  foetus       .          . 

1030 

45 

623 

947 

of  apparatus  of  taste    .          .         4 

32,  924 

Complementary  apparatus  of  pedal  bone 

909 

articulations,  coxo-femoral    . 

216 

Composite  nerves 

804 

humero-radial 

197 

Compressor  vesiculae    . 

969 

interphalangeal   . 

212 

Conarium            .... 

772 

metacarpo-phalangeal  . 

207 

Concha  auris       .... 

280 

199 

281 

scapulo-humeral 

195 

16. 

auditory  apparatus 

958 

Conchal  cartilage 

*. 

axillary  arteries. 

659 

Confluent  of  jugulars  .          .          . 

687 

552 

Confluents  of  subarachnoid  fluid    . 

752 

carotid  arteries  .         .          . 

680 

Congestion  of  liver 

501 

782 

Conglomerate  glands  . 

395 

cerebro-spinal  axis 

754 

Conjunctivae       .... 

942 

cerebrum  .... 

801 

Connective  cells            .          . 

4 

197 

»6. 

enveloping  membranes 

754 

5 

external  iliac  arteries  . 

643 

Contractile  cells           .          .          . 

4 

.       983 

fibrillffi       .          .          0          . 

231 

male  .          .          . 

.       989 

Convoluted  tube  of  kidney    o 

572 

great  sympathetic         .          . 

.       894 

Coracoid  process           .          .          . 

98 

head           .... 

90 

Corium  cutis      .          .         .         .         S 

99,  900 

heart          .          .          . 

.       599 

Cork  of  Ecker     .... 

1007 

.       629 

Cornea      ..... 

928 

— —  intestines   .... 

492 

,b. 

isthmus  of  brain 

778 

Cornu  Ammonis 

791 

larynx        .... 

552 

Cornua  of  spinal  cord  . 

757 

liver           .... 

510 

990 

lumbo-sacral  plexus     .          . 

883 

of  ventricles        .         . 

790 

.       553 

Corona  glandis   .... 

975 

mouth        .... 

430 

radiata       .... 

795 

307 

Corona;  tubulorum       .          .          . 

475 

arm  .... 

.       322 

Coronaria  ventriculi    .          .          . 

613 

• back  .... 

266 

Coronary  cushion         .          . 

911 

costal  region        , 

299 

.  ligament    .... 

ib. 

310 

ib. 

foot  .'.'.'. 

377 

structure    . 

912 

338 

Corpora  albicans  vel  nigrum 

988 

gluteal  region      . 

348 

cavernosa  .... 

973 

hand 

342 

791 

head 

291 

772 

leg    . 

374 

Malpighiana 

572 

neck  .... 

268 

nigra          .... 

932 

316 

68,  776 

sublumbar            .          . 

272 

quadrigemina      ...         7 

67,  771 

thigh           .          .          .          . 

360 

restiformia          ...          7 

69,  777 

thoracic       .           .          . 

299 

Corpus  albicans            ...          7 

70,  791 

nasal  cavities       .          .          .          . 

527 

Arantius    .          .          .          .           . 

589 

872 

callosum              .          .          .          . 

789 

cranial        .          .          .          . 

849 

973 

INDEX. 


10(Jl 


Corpus    cavernosum,  external  confoima 

Cuticle 

903 

tion        ...... 

973 

Cutiduris  ...... 

911 

structure    . 

974 

Cutigeral  cavity           .... 

915 

932 

Cutis  anserina    ....         900.  907 

781 

Cuvierian  ducts ..... 

1044 

fimbriatum 

792 

Cysterna  chyli 

721 

geniculatum,  externum 

772 

Cytoblasts 

903 

internum    . 

ih. 

Czermak,  interglobular  spaces  of  . 

413 

962 

luteum 

988 

Dartos 

961 

false  . 

»6. 

Deciduous  teeth            .          .          .         416,  426 

ih. 

Deferent  canal    ....         963,967 

olivare 

769 

structure  of 

ih. 

• rhomboideum      . 

781 

Deglutition          .... 

445 

89,  792 

Demours,  membrane  of 

938 

(Jorpuscula  tactus 

901 

Dental  follicle     ....       414,  1048 

Corpuscles  of  Krause    . 

807,9 

01,  943 

germ           ....         415,921 

ih. 

pulp            ....         414,415 

Pacinian    .         . 

807 

414 

terminal  genital . 

975 

Dentated  membrane     . 

750 

of  Vater     . 

807 

Dentine 

412 

Corti,  membrane  of     . 

951 

Derma 899,900 

organ  of    . 

Costae 

ih. 

900 

94 

Descemet,  membrane  of         .          .         929,  938 

Costal  cartilages 

95 

Development    of    annexes    of  alimentary 

543 

canal        .... 

1047 

region 

296 

of  auditory  apparatus  . 

1036 

Cotyledons 

1027 

of  brain      .... 

.     1033 

Cotyloid  cavity  . 

127 

.     1032 

Cowper's  glands 

973 

of  circulatory  apparatus 

1041 

Cranial  arachnoid 

752 

of  cranium  and  face       .          . 

1039 

cavity 

747 

of  digestive  apparatus 

1046 

dura  mater 

750 

1030 

1039 

of  genital  organs 

.      1050 

807 

of  genito-urinary  apparatus  . 

1049 

•  origin  of    . 

808 

of  gustatory  apparatus 

1037 

pia  mater  . 

.       754 

of  heart  and  vessels      . 

1042 

Cranium,  bones  of        . 

46 

of  lateral  laminae 

.      1032 

Cremaster 

961 

of  limbs      .... 

.      1040 

Cremasteric  fascia 

ih. 

of  locomotory  apparatus 

.      1038 

Crested  convolution     , 

786 

.      1045 

Cricoid  cartilage 

528 

of  muscles  .... 

.      1040 

Crico-thyroid  membrane 

529 

.      1032 

530 

.     1035 

Crown  of  tooth  . 

412 

of  nervous  system 

.     1033 

Crucial  fissure    . 

785 

.      1013 

Crura  cerebelli    . 

711 

of  olfactory  apparatus 

1037 

cerebri        .          . 

r67,  770 

of  respiratory  apparatus 

1045 

of  fornix     . 

791 

of  skeleton 

.     1038 

of  penis 

.        973 

of  spinal  cord 

1034 

Crural  aponeurosis 

501,  302 

1037 

arch 

ih. 

1040 

internal  region   . 

353 

of  urinary  organs 

1050 

posterior  region  . 

351 

1038 

ring  . 

302 

1032 

Crus  ad  meduUam  oblongati 

im 

771 

of  visual  apparatus 

1035 

cerebelli  ad  pontem 

ih. 

Dewlap 

904 

Crusta  petrosa    . 

414 

Diaphragm          .... 

308 

Cryptae  mucosae  . 

474 

Diaphragmatic  pleura 

543 

Cryptorchids 

962 

region         .... 

308 

Crystalline  lens  . 

i 

26,  936 

Diarth roses          .... 

171 

development  of 

936 

Diastole  of  heart 

598 

1036 

Dieters,  prolongation  of 

761 

structure  of 

£ 

36,  937 

Differential     characters     in      abdomina 

Cumulus  ovigerus 

987 

cavity    . 

455 

Cuneiform  cartilages   . 

529 

air-tube 

541 

curved  plait 

788- 

1027 

Cutaneous  gland  of  Pig 

901 

apparatus  of  taste 

923 

lamina 

1032 

1062 

INDEX. 

PAGE 

Differential   characters   in    articulation 

.^ 

Differential  characters  in  forearm  . 

atlo-axoid        .... 

.       186 

—  gluteal  region 

.       203 

head 

.       192 

hyoid  region 

.       215 

leg     . 

.        220 

• masseteric  region 

humero-radial 

.        197 

palpebral     . 

.       203 

panniculus  carnosus 

209 

210 

207 

spinal  region 

.        188 

198 

thigh 

scapulo-humeral 

195 

193 

nasal  bones 

225 

temporo-maxillary 

189 

220 

958 

palatine  bone 

axillary  arteries 

656 

brachial  plexus    . 

866 

parietal  bone 

798 

carotid  arteries    . 

675 

pharynx      .          .          .          . 

111 

-cerebellum 

782 

limb  .          .          .          . 

798 

premaxillary  bone 

cervical  vertebrae 

30 

pterygoid  bone     . 

■  coccygeal  bones    . 

41 

sacral  vertebra;    . 

cranial  nerves 

843 

salivary  glands    . 

118 

scapula        .          .          .          . 

—  dorsal  vetebra? 

35 

envelopes  of  cerebro-spinal  axi 

,       754 

spinal  cord 

56 

•  external   iliac   arteries 

640 

femur 

139 

sternum      .          .          .          . 

106 

52 

superior  maxillary  bone 

genital  organs  of  female 

999 

976 

great  sympathetic  system 

894 

thorax 

heart 

599 

thymus  gland 

103 

hyoid  bone 

79 

76 

urinary  apparatus 

628 

intestines    . 

485 

778 

lachrymal  bone    . 

70 

vomer          .          .          .          . 

144 

Digestive  apparatus      ...         3 

liver 

508 

of  Birds       .         .          .          . 

lumbar  vertebra 

37 

Dilator  of  the  pupil       .          .          .          . 

lumbo-sacral  plexus 

881 

Dissection  of  arteries    .          .          .          . 

lungs 

552 

Discus  proligerus           .          .          .          . 

lymphatic  system 

732 

Dorsal  nerves 

malar  bone 

69 

furrow          .         .          .          .          . 

metacarpal  bones 

113 

groove          .         .         .          .          . 

■  metatarsal  bones 

149 

424 

Double-contoured  nerve-fibres 

muscles. 

Duct  of  Steno 

307 

of  Wharton          .          .           .          . 

342 

of  Wirsung           .          .          .          . 

arm    . 

321 

Ducts,  accessory  pancreatic 

axillary  region      . 

296 

biliary          .         .          .          .          . 

252 

Cuviei-ian     .         .          .          .          . 

258 

genital 

• superior 

244 

guttural      .          .          .          .          . 

299 

mammary  .          .          .          .          , 

310 

Miiller's 

facial  region 

289 

parotid 

INDEX. 


1063 


Ducts,  perspiratory 

salivary 

thymic 

Ductus  ad  nasum 

arteriosus 

choledochus 

couise 

structure 

cysticus 

ejaculatorius 

galactophorus 

hepaticus    . 

lactiCerus    . 

lymphaticus  dexter 

pancreaticus  minor 

pi-ostaticus 

Riviniani    . 

— —  thoracicus  . 

venosus  of  Aranzi 

Duodeual  glands 
Duodenum 
Dura  mater 

structure 

Duverney,  glands  of 


Ear,  external 

internal,  nerves 

middle 

Ear-dust 
Ectoderm    . 
Ectoderraic  globe 

ridges 

Ectopias  of  testicles 
Effluent  canals  of  dura 
Ejaculatory  ducts 
Elastic  fibres 
Embryogenous    vesicle 
Embryology 
Embryonal  area 
Emergent  veins  of  spi 
Eminences 
Eminentia  teres  . 
Enamel 

germ 

Enarthrosis 
Encephalic  arachnoid 

dura  mater 

pia  mater  . 

Encephalon 

as  a  whole 

constitution 

general  form 

isthmus 

volume 

weight 

Endocardium 
Endoderm 
Endodermic  globe 
Endolyraph 
Ensiform  cartilage 
Envelopes  of  cerebro-: 
Ependymis  of  spinal 
Epiblast     . 
Epicardium 
Epidermis 

growth  of  . 

structure    . 

Epididymis 

■ structure  . 


nal 


spinal 


PAGE 

.       902 

435,  437 

556 

945 


b2, 


1043 
499 

ib. 

ib. 
508 
969 
998 
499 
998 
731 
503 
973 
438 
721 
1027,  1044 
471 
472 
749,  751 
749 
984 

957 
948, 951 
957 
950 
1007 
1006 
1011 
962 
694  ' 
568,  969 
4 
1005 

ib.    I 
1007    : 
695 
14 
796    I 
413,  1048 
415,  1048    i 
176    I 
752  : 
750    I 
754 
763    j 
ib. 
ib. 
ib.   I 
766 
765 

ib.  : 
596 
1007 
1006 
948,  951 
93 
474 
757,  775 
1007  i 
597 
903 


Epiglottis 
Epithelial  cells 

tissue 

Epithelium 

ciliated 

columnar 

cylindrical 

pavement 

simple 

spherical 

squamous 

stratified 

Epoophoron 
Erectile  tissues 
Ergot 

of  Morand 

Essential  organ  of  vision 
Ethmoidal  lobe  , 

sinus 

Eustachian  tube 

valve 

External  auditory  hiatus 
Eye  ... 

Eyelashes  . 
Eyelids 

commissui-es 

integuments        , 

structure   . 

Eye-vesicles,  primitive 


I    Falciform  ligament 
j    Fallopian  tubes  . 
i functions 

structure 

False  glands 

nostril 

Falx  cerebelli      . 

j    cerebri 

■    Fang  of  tooth     . 

Fascia  infundibuliform 

lata  . 

trausversalis 

Fasciculus,  primitive 
Fatty  nucleus  of  Baur 
Fauces 

isthmus  of 

Female  pronucleus 
Femoral  region  . 
Fenestra  cochlea 

ovalis 

rotunda     . 

vestibuli 

Fenestrated  membrane 
Ferrein,  pyramids  of 
Fetlocks    . 
Fibres 

of  Remak  . 

Fibro-cartilages,  complementary 

intervertebral 

pedal  bone 

Fibro-intestinal  lamina 
Fibrous  tissue     . 
Fibrous  zones  of  heart 
Filiform  papillae 
Filum  terminale 
Fimbria  of  Fallopian  tube 

j6.       Fimbriated  extremity  of  oviduct 
967       Fissura  Glaseri  . 
ib.   i   longitudinalis,  inferior 


PAGE 

529 
4 
th. 
393 
«5. 
ib. 
ib. 
ib. 
ib. 
ib. 
ib. 
ib. 
988 
518 
905,  910,  922 
803 
926 
785,  786 
525 
952,  955 
590,  600 
957 
925 
943 
925,  941 
941 
942 
941 
1031 

452 
989 
990 
989 
719 
518 
754 
750 

412,  417 
961 
349 

303,  307 
231 
404 
408 
ib. 
1006 
348 
950 

948,  951,  952 

949,  951,  952 
948,  952 

604 

572 

905 

4 

740,  887 

117 

179 

909 

1013 

4 

592 

402,  923 

753,  1034 

.   989 

ib. 

.       673 

.   756 


1064 


INDEX. 


Fissura  longitudinalis,  superior     . 

PAGE 

.       756 

Fossulate  papillae         .... 

.       941 

Fourchette          .... 

Fissure  of  Bichat 

784 

Fourth  ventricle  of  brain      . 

calloso-marginal 

.       786 

Fovea  centralis  .... 

interlobular 

.       783 

Fracinum  linguae 

.       785 

praeputii    .... 

interpeduncular  . 

.       770 

Frog  of  hoof       .          , 

parallel      . 

.       788 

Frog-stay            .          .          , 

.        116 

Frontal  diverticulum  . 

pleuro-peritoneal 

.     1013 

horns 

Rolando,  of 

785 

lobe 

785,  786 

*5 

Flocculus  .... 

.       782 

Functional  vessels  of  lungs  . 

Fluid  of  labyrinth 

.       953 

Fundus  of  bladder        ,          . 

Foetus,  development  of          . 

.     1030 

Fungiform  papillae       .          . 

40 

circulation  in      .          . 

.     1041 

Funicular  ligaments    .         .         , 

17 

Follicles,  aggregated    . 

.       475 

396,  407 

Galactophorous  ducts  . 

hair            .          .          . 

906 

sinuses        .          .          . 

.       474 

Galeati's  glands            .          . 

mucous      . 

393,  461 

Ganglia     .... 

72 

simple        .          .          , 

.       374 

structure     . 

396,  474 

Andersch's           .          . 

8S 

structure  of 

396,  473 

Arnold's    . 

ultimate    . 

.       433 

Follicular  glands          .          . 

.       406 

intermediate 

.       995 

superior      . 

Fontana,  canal  of 

.       931 

spaces  of   . 

.       928 

Cloquet's    . 

Foramen  of  Botal         .          . 

589,  942 

Ehrenritter's 

caecum  of  Morgagni      . 

401 

of  Vicq-d'Azyr    . 

.        778 

geniculate 

commune  anterius 

772,  775 

posterius    .          . 

.       772 

hypoglossal 

condyloid  .          .          . 

47 

inferior  cervical 

infra-orbital 

63 

intumescentia 

26 

57 

47 

Meckel's    . 

posterior  , 

ib. 

middle  cervical 

Monro,  of 

775,  789,  790 

naso-palatine 

.       951 

nutrient     .          ,         . 

18 

otic  . 

obturator  . 

129 

petrosum   . 

occipital     . 

47 

semilunar  . 

\        8 

58,  587 

58 

Soemmering,  of  . 

.       947 

spinal 

spinal         .          .         , 

24 

submaxillary 

spinosum   .          .          , 

58 

61 

Ganglion  cells    . 

subpubic    .          .          . 

.        129 

Ganglionic  nerves 

subsphenoidal      .          . 

58 

Gasserian  ganglion 

superciliary 

51 

Gastro-colic  omentum           . 

4. 

40 

Gastrodisc 

supra-orbital        .          . 

51 

Gastro-hepatic  omentum 

trachelian 

47 

Gastro-splenic  omentum 

vertebral    . 

»6. 

Galatine  of  Wharton    . 

Vidian 

56 

Gelatinous  substance  of  Rolando 

Winslow    . 

.       453 

Gemmation 

Forceps  major     . 

.       803 

Generative  apparatus  . 

Forearm,  bones  of        .         , 

.       103 

of  Birds      . 

Fore  foot,  bones  of 

107 

Genital  duct 

Forelock   .... 

.       904 

gland 

Formation  of  embryo  . 

.     1032 

organs  of  female 

Fornix       .... 

789,  791 

Fossa  centralis  retinae 

947 

.       589 

Genu  of  corpus  callosum 

— —  navicularis           .          . 

.       970 

Germ  epithelium 

. 

INDEX. 


1065 


Germ  of  hair      . 

PAGE 

906 

Glands,  popliteal 

PAGE 

727 

Germinal  area    . 

.     1007 

pra;putial  . 

!        901,  976 

disc  .          .          ,          , 

.      1010 

.       727 

986 

prepectoral 

730 

spot             .          .          . 

lb. 

.       731 

streak 

.      1007 

prostate     . 

.        973 

vesicle 

.     1004 

racemose    . 

395,  407 

Gianuzzi,  "lanula  of      .         , 

.       433 

727 

Ginglymus 

176 

salivary     . 

.       433 

Glandulae  agminatae     . 

.       475 

sebaceous  . 

.        901 

ib. 

simple 

.        395 

Glands       .... 

395 

socia  parotidis 

441 

agminated 

.       475 

solitary 

396,  474 

anterior  limb,  of 

.       729 

.       728 

.     1000 

staphyline 

.       438 

brachial      . 

.       731 

stomach,  of 

.       728 

Brunner,  of         .          . 

.       474 

.       730 

caecum,  of . 

728 

sublingual 

437,  439 

ceruminous 

.       957 

sublumbar 

724 

cheeks,  of.           .          , 

398,  438 

436, 

439,  730 

886 

subzygomatic 

.       440 

colon,  of     . 

.        727 

sudoriparous 

901 

conglomerate 

.       395 

.       729 

.        973 

thymus      . 

.       555 

cutaneous,  of  Pig          . 

.       901 

thyroid      . 

553 

duodenal    .          .          , 

.       474 

tracheal     . 

539 

.       984 

tubular      . 

.       395 

follicular    . 

.       406 

Tyson's      . 

.       901 

Galeati's    . 

.       474 

uterine 

993 

gastric 

.       461 

utricular    . 

ib. 

genital 

105 

vulvo-vnginal 

.       996 

guttural    . 

.        730 

Glandular  cuts-de-sac 

433 

944,  946 

tissue 

5 

head,  of     . 

.        729 

Glans  clitoridis  . 

995 

honeycomb 

.       475 

.       975 

.       727 

Glenoid  cavity  . 

98 

inguinal,  deep     . 

726 

Glisson,  capsule  of 

497 

.6. 

Globus  major  epididyE 

ais 

967 

.       728 

ib. 

interungulate  of  Sheep 

.       901 

Glomes  of  frog  . 

917 

labial 

398,  406,  438 

Glomeruli  of  kidney 

572 

■ lachrymal  . 

.       944 

Glottis      . 

535 

laryngeal   . 

.       534 

Gluteal  aponeurosis 

543 

lenticular  . 

474 

region 

ib. 

Lieberktihn's 

474,479    ; 

Glycogen  . 

497 

400,438 

Goll's  column     . 

758 

liver 

494,  728 

Goose-skin 

900 

lobulated   .          .          .          . 

.       395 

Graafian  vesicles 

985 

.        886 

Granules,  fat      . 

3 

lymphatic .          .          .          . 

.        718 

pigmentary 

ib. 

mammary .          .          .          . 

.       997 

proteic 

ib. 

maxillary  .          .          .          . 

436,  440 

Great  lymphatic  vein 

721 

943 

sympathetic  system      . 

885 

molar         .          .          .          . 

398,  438 

structure    . 

886 

■ mucus  of  stomach 

.       461 

transverse  cerebral  fissi 

ire     . 

784 

.       729 

Grey  nerve-fibres 

740 

Nuhn's       . 

441 

root  of  optic  nerves 

810 

odoriferous          .         . 

.        523 

777 

Pacchionian 

.        751 

Gubernaculum  dentis  . 

41 

5,  1048 

palate,  soft 

411,  439 

testis 

966 

pancreas     .          .          .          . 

.        502 

Gum 

414 

parotid       .          .          >          ■^ 

134,  439,  450 

Gustative  bulbs . 

923 

Pecklin,  of          .         ,         . 

475 

cells . 

924 

peptic         .          .          .          . 

.        461 

Guttural  pouches         . 

596 

perspiratory 

.       901 

Gyri 

785 

Peyer's       .... 

475 

annectant  . 

ib. 

,        730 

Gyrus  fornicatus 

791 

■ pineal         .... 

772 

rectus 

786 

pituitary  .... 

522,  773 

Habenae     . 

772 

1066 


INDEX 


FAOK     1 

PAGE 

Haemal  arch 167    ; 

Hypochondriac  region. 

451 

Hsematies. 

3 

Hypogastric  region      .          .         .          . 

ih. 

Hairs         .... 

904  : 

Hypophysis  cerebri      .          .          .          . 

773 

follicles      . 

906 

formation  of 

907 

Ileo-csecal  valve.          ...         4 

73,  478 

ih. 

Ileum 

472 

germ  of      .          • 

906 

Imprint 

14 

horse,  of    . 

904 

Incisor  teeth                  .          .           412r,  4 

17,  425 

sheath  of  . 

906 

Incus         ...... 

954 

Haller's  passage            .          . 

1042   ■ 

Infundibula  of  lungs    .          .          .          . 

548 

Hand          .          .          .          . 

121 

Infundibuhform  fascia           . 

961 

Harder,  glands  of 

s 

44,  946 

Infundibulum      .          .          .          .          . 

773 

Harraonia  suture          .          < 

177 

Inguinal  canal 

302 

Haversian  canals          ,          , 

16 

hernia 

632 

Head,  bones  of   . 

46 

302 

in  general . 

80 

Injection  of  arteries     .          .          .          . 

606 

Heart        . 

583 

of  veins 

685 

action 

598 

Inosculation        .... 

602 

capacity     . 

584 

Insulae       ...... 

722 

ih. 

Integuments  of  external  ear. 

958 

external  conformation 

ih. 

Intel-articular  meniscii 

216 

ih. 

Intel-auricular  partition 

587 

general  sketch    .          , 

583 

Intercarotid  ganglion  .          .          .          . 

894 

interior      . 

587 

Interglobular  spaces  of  Czermak    . 

413 

■ nerves  and  vessels  of 

596 

Interlobular  fissure 

783 

serous  membrane          . 

ih. 

veins 

498 

situation    . 

584 

Internal  crural  region. 

3.53 

591 

ear    ..... 

947 

volume 

584 

nerves  of    . 

951 

weight 

ih. 

Interosseous  cartilages 

173 

Helicine  arteries          .         , 

.        974 

Interpeduncular  fissure          .          . 

770 

Helico-trema 

949 

Interstitial  substance  . 

232 

Hemispheres,  cerebral 

784 

Interungulate  gland    . 

901 

Henle,  ansiform  tube  of 

.        572 

Interventricular  septum 

587 

sheath  of  . 

.       803 

Intervertebral  fibro-cartilages 

179 

Henson,  streak  of         . 

232 

foramen     .... 

26 

Hepatic  cells 

497 

Intestines  ..... 

471 

ducts 

.       498 

development 

1047 

497 

large           .... 

477 

Hernia,  inguinal 

632 

attachment 

478 

Herophilus,  wme-press  of 

692 

capacity     . 

ih. 

Highmorianum,  corpus 

963 

dimensions. 

lb. 

Hilum  pulmonis. 

546 

ih. 

Hilus  of  kidney  . 

570 

functions    . 

479 

Hippocampus 

89,  791 

mterior 

478 

Hippomanes 

1021 

ih. 

Hollow  organs    , 

392 

i6. 

ih. 

structure    . 

.•6. 

Holoblastic  type 

1009 

small          .... 

471 

Honeycomb  glands 

475 

attachment 

.       472 

Hoof 

.        908 

ib. 

ih. 

.       477 

description  of 

914 

form. 

.       471 

development  of   . 

919 

.       477 

structure  of 

.        917 

472 

wall  of       . 

.       915 

•6. 

Hoof-horn .          .          . 

917 

structure    . 

.       473 

ih. 

Intra-lobular  veins 

498 

Horn  cells. 

.       918 

Ins 

.       932 

Horns,  frontal     . 

.       922 

.       933 

Horny  productions 

907 

Ischiatic  spine     .... 

.        128 

Horsehair 

.       904 

Island  of  Reil      .... 

.       786 

Humours  of  eye  . 

926,  936 

Isthmus  of  brain          .          .           763, 

766,  767 

Hyaloid  membrane 

.       937 

.        766 

Hydatid  of  Morgagni    . 

.       982 

internal  conformation  of 

774 

Hygrophthalmic  canals 

.       944 

structure  of 

776 

Hymen 

.       996 

.       408 

Hyoideal  region  . 

.       286 

Iter  ad  infundibulum  . 

.       775 

Hypoblast. 

.     1007 

quartum  ventriculum   . 

ib. 

INDEX 


1067 


PAGE 

PACK 

Ivory        

412,  1048 

Lateral  ventricles 

789,  790 

Left  auricle  of  heart    . 

.        591 

Jacob's  membrane        .         • 

934 

ventricle  of  heart 

590 

Jacobson,  nerve  of       .          .          . 

.       833 

Leg,  bones  of      .          . 

140 

Jejunum    .          .          .          .          . 
Jugular  channel 

.       521 
.       472 

Lens,  crystalline 

362 
.       936 

.       687 

ib. 

ib. 

structure  of 

ib. 

Lenticular  ganglion     . 

822 

Keraphyllous  tissue     . 

.       915 

.       471 

Keratogenous  membrane 

Kidneys    .          .          .          .          » 

.       911 
.       568 

papilla 

792 
402,  923 

.■6. 

Lenticulo-stnated  bodies 

794 

internal      . 

.       570 

Leucocytes 

4 

development 

573,  1050 

Lieberkiihn's  follicles  . 

474 

ib. 

574 

.     1041 

Ligaments 

173 

proper  tissue 

571 

174 

570 

funicular     . 

ib. 

.        568 

interosseous. 

ib. 

structure  • 

.       570 

ib. 

ib. 

peripheral    . 

%b. 

.       570 

white. 

.        173 

Krause,  corpuscles  of  . 

806,  943 

174 

.       975 

202 

arteriosum 

607 

Labia  vulva       .          .         .         . 

.       995 

224 

Labial  glands      . 

398,  438 

atlo-axoid,  inferior 

186 

Labyrinth. 

.       947 

ib. 

superior      . 

auditory     . 

t6. 
954,  955 

membranous 

949 

bladder,  of 

576 

Lachrymal  apparatus  . 

.       944 

454,  990 

.       945 

calcaneo-astragaloid 

223 

ducts 

ib. 

calcaneo-metatarsal 

224 

gland 

944 

capsular  of  atlo-axoid 

articulation.        188 

.        816 

of  carpal 

.        202 

.        945 

„         .        192 

Lachus  lachrymalis      . 

941 

of  coxo-femoral 

•       215 

Lacteal  vessels    . 

.        473 

r        „         .       218 

Lactiferous  ducts 

.       998 

„         .       196 

sinuses        .          .          • 

ib. 

„         .       190 

Lamella  of  foot  . 

.       913 

langeal  „     .       206 

Lamina  cinerea  . 

.       775 

„     .       188 

cribrosa 

811,  928 

al           „     .        194 

.        928 

of  temporo-maxil 

lary        „     .        188 

spiralis 

Laminae  of  foot  . 

.       949 
913 

cardiac 

„     .        180 
.       452 

Laminal  tissue    . 

ib. 

carpo-metacarpal 

201 

Lancisii,  chorda  longitudinalis  of 

.       790 

carpal,  anterior  . 

201,  202 

Large  intestine  . 

Larynx      .... 

477 

cervical      . 

180 

.       527 

193 

articulations 

.       530 

ciliary 

931 

.      1046 

colli . 

180 

.       535 

201 

external  surface  . 

ib. 

.       180 

.       528 

179 

functions   , 

.       535 

ib. 

i6. 

supra-spinous 

180 

.       531 

coronary  of  liver 

495 

nerves 

534,  837,  838 

192 

.       528 

ib. 

ib. 

lor       .          .        191 

ventricles  . 

535 

ib. 

.       534 

214 

Lateral  columns  of  spinal  cord 

.       757 

.        215 

fibro-cartilages    . 

.       909 

.       830 

.       917 

crico-trachealis    . 

531 

.      1032 

.       187 

triangular  fasciculus  of  isthr 

nus     .       771 

.       223 

1068 


INDEX. 


PAGE 

PAGE 

Ligaments,  cuboido-scaphoid 

223 

Ligaments,  uterine,  suspensory      .         .       990 

denticulated         .          .          .          . 

753 

vesico-uterine 

576 

diaphragmatic     .          .          .          . 

1049 

997 

Fallopii 

302 

Wolffiani,  of  corpora     . 

1049 

femoro-patellar  .          ,          .          . 

218 

Limbs  in  general 

154 

glosso-epiglottic 

401 

155 

hepatic       .          .          .          .          . 

495 

Limitans  iridis   . 

933 

453 

Limitary  membranes   . 

5,  393 

humero-radial,  external  lateral 

195 

Linea  alba 

299,  300 

internal  lateral     . 

196 

Linea;  transversse 

.       790 

212 

Lingual  canal 

400 

ib. 

438 

interannular 

182 

glandula   . 

398 

190 

lacunse 

401 

intercarpal 

200 

mucous  membrane 

923 

interlamellar 

182 

Linguetta  laminosa 

771 

00,  201 

Lips 

397,4 

23,  424 

198 

functions  of 

398 

interphalangeal,  first   . 

208 

397 

second 

ib. 

Liquor  amnii 

1019 

204 

folliculi      . 

986 

interspinous 

182 

labyrinth!  . 

951 

intervertebral     . 

179 

937 

206 

seminis 

966 

546 

Liver 

494 

lobus  Spigelii,  of 

453 

attachments 

495 

lumbar  of  corpora  Wolffiani . 

1049 

development 

5C 

2,  1049 

metacarpo-phalangeal  . 

204 

direction    . 

494 

nuchse        .... 

180 

ib. 

odontoid     .... 

186 

functions   . 

500 

ovarian      .          .          .          .        4 

154,  984 

proper  tissue 

497 

patellar     .... 

217 

relations    . 

495 

929 

494 

peripheral,  inferior 

191 

structure  . 

497 

Poupart's  .... 

302 

494 

pubio-femoral      . 

214 

Lobes  of  liver     . 

495 

radio-carpal 

200 

Lobular  bronchial  tube 

.       547 

198 

Lobulated  glands 

395 

ib. 

Lobule,  anterior  of  lung 

.       547 

external  transverse 

ib. 

of  curved  plait    . 

86,  788 

recto-uterine 

.       567 

Lobuli  testis 

.       962 

recto-vesical 

ib. 

Lobulus  pneumogastricus 

.       547 

round,  of  uterus  .         .          .        4 

154,  992 

Lobus  Spigelii    . 

.       495 

.       212 

Lockhart's  columns      . 

761 

ib. 

Locomotory  apparatus 

7 

ib. 

Locus  coeruleus  . 

.       814 

scaphoido-cunean 

.       224 

perforatus 

786 

sesamoid     .... 

.       204 

posticus      . 

ib. 

inferior 

ib. 

Longitudinal  fissure  of  brain 

.       783 

lateral 

ib. 

Lowenberg's  scala 

.       951 

ib. 

Lumbar  nerves  . 

857 

spleen,  of  . 

.       503 

vertebrae    . 

36 

stellate      .          .          .          .         ] 

91,  192 

Lumbo-rachidian  bulb 

.       756 

ib. 

Lumbo-sacral  plexus   . 

.       874 

subflava     .... 

182 

Lungs 

545 

supra-dorso-lumbar      . 

.       180 

development 

".       5 

J2,  1045 

supra-spinous  cervical  . 

ib. 

.        545 

206 

.        551 

of  penis      .          .           975,  < 

J76,  978 

fundamental  tissue 

.       547 

of  sheath    . 

.       976 

general  disposition 

.       545 

of  uterus    . 

.       990 

t6. 

tarsal         .... 

221 

serous  envelope  . 

.       547 

225 

situation    . 

545 

teres          .... 

.       215 

structure  . 

.       547 

.       217 

Luschka's  gland 

.       886 

• tracheal     .... 

538 

Lymph 

.       582 

umbilical   .... 

576 

Lymphatics,  course  of 

.       716 

154,  990 

.       714 

round         .         .         , 

ib. 

glands 

.       718 

INDEX. 


1069 


Lymphatics,  numbei-    . 

origin 

plexuses 

preparation  of 

rete  mirabile 

structure 

termination 

vessels 

Lymphatics 

Birds,  in    . 

bladder,  in 

bone,  in 

brachial     . 

bronchial   . 

caecum,  in . 

colon,  large,  in 

small,  in 

guttural     . 

heart,  in    . 

hepatic  lobules,  in 

iliac 

inguinal,  deep 

superficial 

intestines,  in 

kidneys,  in 

laryngeal  . 

lips,  in 

liver,  in     . 

lungs,  in    . 

mucous  membranes,  in 

muscle,  in  . 

nerve-tissue,  in 

nostrils,  in 

ovary,  in    . 

penis,  in     . 

peritoneum,  in 

pharyngeal 

pia  mater,  in 

pituitary    . 

popliteal     . 

precrural    , 

prepectoral 

prescapular 

rectum,  in  . 

serous  membranes,  in 

skin,  in 

small  intestines, 

spleen,  in   . 

stomach,  in 

subglossal  . 

sublumbar 

submaxillary 

supra-renal  capsules,  in 

testicle,  in 

thorax, in  . 

thymus  gland,  in 

thyroid  gland,  in 

urethra,  in 

uterus,  in  . 

vagina,  in  . 

vessels,  in  . 

Lymphatic  sheaths 


Macula  lutea 
Male  pronucleus 
Malleus     . 

Malpighian  corpuscles 
glonierules 

70 


PAGE     ] 

PAGE 

715 

Mammae    .          .          . 

997 

.       714    i 

form            .          .          .          . 

ib. 

715,  717 

functions    .          .          .          . 

.       999 

.        714 

situation    .          .          .          . 

.        997 

717 

structure    .          .          .          . 

998 

714,  718 

Mammary  ducts 

ib. 

.       717    ! 

glands        .          .          .          . 

ib. 

713    I 

Mammilla            .          .          .          . 

997 

.       713    1 

Mammillary  tubercle  ■ 

.        780 

736 

Manubrium         .          .          .          . 

.        954 

577 

Manyplies            .          .          .          . 

.       468 

18,  716 

Marginal  zone     .          .          .          . 

.      1013 

731 

Masculine  uterus 

.       969 

551,  729 

Mastoid  cells  of  ear 

952,  953 

.        728 

lobule  of  brain    . 

787,  788 

727 

Matrix  of  hoof    . 

908,  911 

ib. 

Maxillary  gland 

.       436 

.       730 

Meatus  auditorius  externus 

.        957 

.       596 

nasal 

.       520 

500 

.       995 

.        727 

valve  of     . 

ib. 

.       726 

Meckel's  cartilage 

.      1039 

ib. 

ganglion     . 

823 

479,  727 

Meconium 

502 

.        573 

Median  lacuna  of  frog 

.        916 

.        534 

sinus 

.        692 

.        398 

Mediastinal  pleura 

.       543 

500,  728 

Mediastinum,  anterior 

ib. 

.       551 

posterior    . 

ib. 

715 

testis 

962 

235,  716 

Medulla  of  bones 

18 

.       716 

Medulla  oblongata 

766,  767 

.        524 

Medullary  cells 

.     4,18 

.        906 

groove 

.      1013 

972 

layer  of  kidney    . 

.        571 

.       458 

Medullated  nerve-fibres 

740 

.       730 

Medullo-cells       . 

.     4,18 

.       753 

Meibomian  glands 

941,  942,  943 

524,  525 

Meissner,  corpuscula  tactus  of 

.        901 

.       727 

Membrana  chorio-capillaris  . 

930 

ib. 

dentata 

753 

730 

granulosa   . 

985,  987 

.       731 

.       934 

.       727 

nictitans    . 

.       943 

.       716 

pupillaris   . 

.      933,  1036 

715,  902 

.     1009 

.       426 

tympani     . 

.       952 

506,  728 

ib. 

462,  728 

.  ■    986 

.        730 

Membrane  of  aqueous  humour 

.       938 

.        724 

basilar 

951 

.        730 

Bruch,  of  . 

.       931 

.        579 

choroid 

.       930 

.       965 

conjunctival 

942 

729 

Corti,  of     . 

.        951 

.       556 

.       938 

.       554 

dentated     . 

753 

972 

Descemet,  of 

.       938 

.       993 

eye,  of        .          .          . 

927 

.       995 

604 

716 

hyaloid 

.        937 

605,  716 

keratogenous 

.       911 

.        719 

.        393 

Reissner,  of 

950 

947 

.       394 

.      1006 

vitreous 

.        931 

.       954 

Membranous  cochlea    . 

950 

504,  572 

ib. 

.       573 

.       970 

1070 


INDEX. 


PAGE 

PAOE 

Membraneous  vestibule          .          .          .        949 

Mucous  membrane  of  ureters 

575 

Meningeal  granulations 

751 

of  uterus     . 

992 

Meninges  of  cerebro-spinal  axis 

748 

994 

Meniscii,  interarticular 

173 

of  vulva 

996 

Meroblastic  type 

1009 

Muller's  duct      .... 

1050 

Mesenteric  glands 

728 

Multipolar  nerve-cells 

740 

Mesentery. 

452,  472 

Muscle-plasma    .... 

235 

colic  . 

452,  454,  483 

Muscles: — striped  in  general 

227 

.        452 

action 

237 

Meso-caeoum 

452,  478 

attachments 

229 

Mesocephalon     . 

767,  769 

appendages 

238 

Mesoblast  . 

.      1007 

239 

Meso-colon 

452 

containing  aponeuroses,  of 

i6. 

Mesoderm 

1007 

contractility 

236 

Meso-rectum 

484 

development           .          .       23 

6,  1040 

Metacarpo -phalangeal  sheath 

329 

228 

Metacarjius 

111 

form   .... 

•6. 

Metagastrula      . 

1007 

380 

Metatarsus 

148 

in  Birds 

378 

Middle  cerebellar  peduncle 

771 

229 

951 

lymphatics 

.       716 

septum  of  nose     . 

522 

239 

774 

nomenclature 

229 

Milk 

999 

physico-chemical  properties 

235 

Milk-fountains    . 

711 

physiological  properties 

236 

Mitral  valves      . 

590 

preparation  of 

239 

Mixed  nerves 

804 

preservation  of 

.       242 

Modiolus   . 

948 

.       229 

Molar  glands 

398,  438 

serous   bursse   of 

239 

teeth 

420,  426,  430 

situation 

.       228 

Monorchids 

962 

227 

Monro,  foramen  of 

75,  789,  790 

.       231 

Mons  veneris 

.     1003 

Morgagni,  caecum  of    . 

401 

membranes  of     . 

.       239 

hydatid    of 

982 

tendons  and  aponeuroses 

.       232 

937 

tissue 

.       231 

ventricles  of 

535 

.       237 

Morsus  diaboli    . 

989 

vessels  and  nerves 

235 

Morula 

.     1007 

volume 

227 

Motor  end-plate 

235 

unstriped    .          .          .         S 

127,  394 

Motores  oculorum  nerve 

812 

283 

Mouth 

.       396 

accelerator  urinae 

.       971 

development  of   . 

1046 

adductor   of  arm 

315 

in  general 

.       423 

brevis 

.       355 

Mucous  derma    . 

393 

magnus 

335 

corium 

.'6. 

parvus 

.       355 

membrane 

ib. 

.       351 

of  bladder  . 

.       576 

.       355 

541 

magnus 

.       352 

479 

277 

of  cheeks     . 

398 

321 

of  Fallopian  tubes 

990 

246 

of  guttural  pouches 

956 

annulus   albidus 

930 

952 

antea-spinatus     . 

312 

479 

997 

small 

473 

323 

of  larynx    . 

534 

of  phalanges         .         C 

24,  363 

of  lips 

397 

gracilis 

.       350 

lymphatics  in 

715 

.       349 

of  mouth    . 

423 

327 

of  oesophagus 

448 

907 

olfactory     . 

523 

533 

of  pharynx 

442 

arytasno-oesophageal      . 

449 

526 

attollens  anticus 

281 

of  soft  palate 

411 

282 

of  stomach 

460 

posticus 

283 

of  tongue    . 

402 

azygos  uvulae 

410 

539 

basio-glossus 

404 

of  tympanum 

955 

351 

INDEX. 


1071 


PAGE     1 

PAGB 

Muscles,  biceps  rotator  tibialis        .          .        351    | 

Muscles,  flexor  brachii 

317 

317 

metacarpi  externum 

327 

brachialis  anticus 

318 

internus 

328 

bronchial 

541 

327 

277 

metatarsi    .          .          .          . 

365 

bulbo-cavernous 

971 

pedis            ...         3 

30,  370 

319 

accessor i us  . 

371 

320 

30,  370 

parvum 

ib. 

perforatus    .          .         3 

28,  369 

253 

fronto-palpebral 

279 

cervico-auriculaies 

283 

gastric        .... 

459 

ciliaris 

930 

gastrocnemius      . 

367 

409 

gastrocnemius  exlernus 

ib. 

265 

369 

complexus  major 

248 

gemelli  of  pelvis 

358 

249 

of  tibia 

367 

S 

73,  274 

358 

972 

genio-glossus 

405 

ib. 

hyo-glossas 

ib. 

969 

288 

middl 

J       444 

gluteus  externus 

344 

ib. 

346 

second  middle 

ib. 

*. 

ib. 

gracilis       .          .          •          . 

353 

995 

great  adductor,  of  thigh 

355 

vulvae,  anterior    . 

997 

256 

ib. 

complexus     , 

248 

315 

.        260 

ib. 

.       404 

corrugator  supercilii     . 

279 

.       301 

961 

of  head 

.       250 

ciico-arytsenoideus  lateralis 

533 

.        269 

posticus 

532 

.       305 

449 

serratus 

.       296 

pharyngeus 

444 

supermaxillo-nasalis      . 

.       278 

•  thyroideus 

532 

heart,  of    . 

.       593 

349 

humeralis  externus 

.       318 

350 

obliquus      . 

ib. 

curvator  coccygis 

273 

.       532 

961 

404 

deep  flexor  of  phalanges 

330,  370 

longus 

ib. 

gluteus 

.        346 

pharyngeus 

.       444 

pectoral      . 

293 

hyo-thyroideus 

.        532 

deltoid 

311 

hyoideus  magnus 

.       288 

depressor  coccygeiis 

273 

parvus 

ib. 

labii  inferioris      . 

276 

289 

283 

iliac  psoas  .... 

.       269 

diaphragm 

308 

iliacus        .... 

t6. 

digastricus 

286 

ilio-spinalis 

263 

.       278 

.       313 

»6. 

intermediate  posterior. 

.        277 

transversalis 

.       279 

internal  flexor  of  metacarpus 

.        328 

erector  coccygeus 

.       273 

297 

penis 

973 

.        303 

.       323 

obturator   . 

.       357 

obliquus 

.        324 

285 

pedis 

324,  363 

vastus 

.        350 

.       376 

interossei    .... 

342 

digitorum 

ib. 

250 

suffraginis    . 

.       326 

.       272 

external  flexor  of  metacarpu 

327 

ib. 

.        297 

.       250 

.        301 

intestinal   .          .          .           473, 

183,  484 

.       357 

intrinsic  of  tongue 

.       403 

pterygoid    . 

.        285 

.       485 

.        350 

ischio-cavernosus 

973 

extrinsic  of  tongue 

404 

.        274 

.        349 

.       356 

■          fleshy  panniculus 

. 

.        243 

.       973 

1072 


INDEX. 


Muscles,  kerato-hvoideus 

288 

Muscles,  pericardium 

labiahs       . '        . 

274 

peristaphyleus  externus 

280 

in  tern  us 

large  extensor  of  forearm 

319 

peroneus    . 

533 

extensor  of  phalanges  .          C 

26,  364 

4 

lateralis  sterni     . 

296 

Phillips,  of 

260 

levator  anguli  scapulae 

246 

popliteus   .... 

humeri 

254 

labii  superioris  alaequi  nasi 

278 

minor 

propnus      . 

276 

posterior  constrictor  of  vulv£ 

menti 

277 

palati           .          . 

410 

942 

ulnaris 

levatores  costarum 

298 

protractor  of  sheath     . 

lingualis    .... 

406 

403 

parvus 

311 

pterygoideus  externus  . 

adductor  of  leg    . 

353 

internus 

extensor  of  forearm 

319 

317 

pterygo-pharyngeus     . 

258 

quadratus  cruralis 

263 

lumborum  . 

longus  colli 

258 

lumbrici    .... 

.       342 

oculi 

masseter     .... 

284 

of  sheath    . 

«6. 

rectus 

humeralis  . 

.       254 

maxillo-labialis   . 

276 

capitis  anticus  major 

mento-labialis      . 

ib. 

minor 

middle  constrictor  of  pharynx 

444 

extensor  of  forearm 

.       320 

gluteus 

.       246 

lateralis 

mylo-hyoideus     . 

.       286 

femoris 

nasalis  brevis  labii  superioris 

.       276 

oculi  externus      . 

i6. 

oblique  extensor  of  metacarpus 

.       324 

.        327 

posterior     . 

of  phalanges 

.        371 

superior 

250 

parvus 

inferior 

ib. 

retraheutes  aurem 

superior 

.        251 

.       301 

sacro-coccygeal   . 

.       303 

coccygeus  inferior 

oculi  inferior 

940 

superior 

ib. 

obturator  externus 

.       357 

lumbalis     . 

ib. 

sartorious  . 

.       288 

oesophageal 

449 

scapulo-humeralis  gracilis 

orao-brachialis     . 

.       315 

oris   .... 

274 

scuto-auricularis  externus 

.       279 

internus      . 

orbito-palpebralis 

942 

panuiculus  carnosus      . 

.       243 

seraispinalis  of  back  and  loin 

palato-glossus     . 

.       406 

colli  . 

t09,  443 

dorsi. 

staphylinus 

.       410 

palmaris  magnus 

.       328 

parotido-auricularis      . 

.       283 

pectineus    .... 

.       355 

posticus      . 

pectoralis  anticus          .          .         ' 

292,  293 

short  abductor  of  arm . 

magnus 

.       293 

1-6. 

extensor  of  forearm 

transversus          .          .         ' 

292,  293 

pedal          .... 

.       376 

perforans   .          .          .          .         ' 

530,  370 

perforatus            .          .          .         i 

528,  369 

anterior  serrated. 

INDEX. 


1073 


Muscles,  small  complexus 

extensor  of  forearm 

hyo-glossus 

lateral  rectus 

oblique  of  abdomen 

of  head 

posterior  rectus 

serrated 

psoas 

.  scapulo-humerahs 

supermaxillo-nasalis 

soleus 

sphincter  ani 

vaginae 

spinalis  colli 

splenius 

of  loins 

stapedius   . 

sterno-aponeuroticus 

costales 

humeralis  . 

hyoideus 

maxillaris  . 

prescapularis 

thyro-hyoideus 

trochineus  . 

stomach,  of 

stylo-glossus 

hyoideus 

maxillaris  . 

pharyngeus 

subcutaneous  of  neck 

sublimis  of  phalanges 

subscapularis 

subscapulo-hyoideus 

superficial  gluteus 

flexor  of  phalanges 

pectoral 

superior  constrictor  of  pharynx 

superior  longitudinal  oesophageal 

supermaxillo-labialis 

supei-naso-labialis 

supra-spiuatus     . 

suspensory,  of  «ye 

temporalis. 

tempoi-o-auricularis  externus 

internus 

tensor  fascia  latae 

palati 

tympani 

vaginae  femoris 

teres  externus    . 

internus 

major 

minor 

thyro-arytsenoideus 

pharyngeus 

tracheal 

transversalis  abdominis 

costarum 

hyoidei 

nasi  . 

transverse  of  abdomen 

spinous  of  back  and  loins 

transversus  perinaei 

trachelo-mastoideus 

trapezius    . 

triangularis  sterni 


PAGE 

249 

321 

406 

257 

303 

251 

252 

262 

271 

316 

278 

368 

485 

995 

250 

265 

246 

271 

955 

293 

298 

293 

225 

255 

295 

255 

293 

459 

404 


410,  444 
253 
328 
314 
256 
344 
328,  369 
292 
444 
449 
276 
278 
312 
939 
285 
282 
283 
349 
410 
955 
349 
311 
315 
.•6. 
312 
532 
444 
538 
305 
265 
289 
279 
305 
265 
972 
249 
260 


Muscles,  triceps  abductor  femoris 

brachialis    . 

extensor  brachii 

femoris 

trochlearis 

tympani  secundaria 

ureters,  of 

urethral  sphincter 

uterus,  of  . 

vagina,  of  . 

vastus  externus  . 

internus 

vulva,  anterior  constrictor 

posterior     . 

Wilson's  muscle  . 

zygomatico-auricularis 

zygomatico-labialis 

zygomaticus 

Muscular  cell-fibres     . 

fibre 

insertions,  table  of 

lamina 

tissue 

non-striped 

striped 

of  heart 

Musculi  papillares 

pectinati    . 

Musculus  ciiiaris 

Riolani 

Myeloplaxes 

Myolemma 

Myosine     . 

Nasal  cavities 
duct 


meatuses    . 

Navicular  sheath 
Nerve-cells 

corpuscles 

fibres 

tubes 

Nerves  : — animal,  of  . 

cerebro-spinal 

cranial 

distribution 

division 

ganglionic    . 

general  sensibility 

mixed 

motor 

organic  life,  of 

origin 

preterminal  peripheral  loops  of 

special  sense 

structure 

termination 

vegetative  life,  of. 

in  Birds     . 

abducentes 

accessory  of  external  saphenous 

of  internal  saphenoui 

of  pneumogastric 

acromial    . 

anal . 

angularis    . 

anterior  brachial 

femoral 


PAGB 

351 
319,  320 
319 
349 
940 
952 
575 
971 


995 
350 

ib. 
997 

ib. 

576,  971 
281 
275 

ib. 
505 
4,231 
380 
1032 
231 

lb. 

ib. 
592 


589 
930 
942 
4,  18 
231 
236 

519 
945 
519 
520 
331 
740 
740 
4 
740 
804 

ib. 

ib. 
805 
804 
804 
804 

ib. 

ib. 

ib. 
805 
807 
804 


518, 


804 
894 
825 
879 
875 
841 
856 
858 
861 
864 
875 


1074 


INDEX. 


PAGE 

Nerves,  anterior  gluteal        .          ,          .877 

Nerves,  latissimus  dorsi  branch 

palatine      . 

817 

levator  anguli  scapulae 

tibial 

879 

832 

lumbar 

auricular,  anterior 

830 

lumbo-sacral 

middle 

ih. 

ib. 

862 

brachial     . 

860 

superior      . 

ib. 

buccal 

819 

cardiac 

891 

mental. 

cervical 

829,  854 

musculo-cutaneous 

8 

821,  829 

ciliary 

.       823 

862 

nasal 

clavicular  . 

856 

obturator  . 

coccygeal  . 

859 

occipito-styloid   , 

32,  951 

collateral-dorsal . 

869 

crural 

875 

internal      . 

cubito-cutaneous 

865 

866 

Cyon's 

841 

superior      . 

dental 

17,  821 

olfactory    , 

anterior 

818 

ophthalmic  of  Willis 

817 

optic 

posterior     . 

ib. 

orbita» 

841 

palatine,  anterior 

diaphragmatic     . 

56,  859 

digastric    . 

829 

digital        . 

867 

palmar 

856 

palpebro-nasal     . 

collateral    . 

869 

pathetic!    . 

825 

popliteal     . 

879 

saphenic      . 

880 

facial 

25,  830 

petrosal,  great  deep 

875 

superficial 

femoro-popliteal,  great 

878 

small  deep . 

small 

879 

frontal 

815 

pharyngeal 

8 

832 

phrenic 

8 

gluteal,  anterior 

877 

8 

posterior     . 

ib. 

external 

878 

ib. 

internal 

il 

827 

pneumogastric     . 

gustatory  , 

820 

popliteal,  external 

858 

hypoglossal 

842 

875 

mollis 

ilio-muscular 

877 

posterior  palatine 

inferior  maxillary 

818 

iufra-orbital 

ib. 

816 

pudic,  internal    . 

857 

rachidian    . 

357 

tibial 

internal 

ib. 

radial 

861 

recurrent   . 

877 

oesophageal 

internal  pterygoid 

820 

pudic 

858 

respiratory 

859 

rhomboideal 

833 

sacral 

—  lachrymal 

816 

saphenous,  external 

laryngeal,  external 

837 

accessoiy 

8 

838 

internal 

superior      , 

837 

INDEX. 


1075 


Nerves,  sciatic,  great  . 

PAGE 

.        878 

1    Nostrils,  functions  of  . 

PAGE 

.       519 

small 

877 

Notochord 

.     1013 

.       861 

Nucleated  nerve-fibres 

740 

small  sciatic 

.        877 

Nuclei  of  corpus  striatum     . 

792 

superficial  petrosal 

829 

740,  762 

.        817 

spinal         .... 

.       853 

Obturator  foramen 

129,  ISO 

841 

Occipito-atloid  siuus    . 

.       692 

splanchnic,  great 

.       892 

Ocular  membrane 

938 

lesser 

ib. 

sheath 

ib. 

817 

(Esophageal  groove 

.       467 

stylo-'hyoid 

.        829 

(Esophagus 

447 

subclavian 

.        873 

course 

ib. 

862 

form 

ib. 

.       821 

450 

suboccipital 

.        854 

448 

864 

relations    . 

447 

subzygomatic 

.        820 

structure   . 

.       448 

superficial  temporal 

ib. 

Oken's  bodies      . 

.      1049 

.       837 

Olfactory  apparatus     . 

523,  924 

maxillary   . 

315,  816 

cells 

523,  925 

supra-orbital 

.       816 

786 

864 

lobules 

785,  786,  809 

.        820 

nerves 

809 

middle  deep 

.       819 

Omasum    .... 

468 

ib. 

structure   . 

.       469 

.       820 

Omentum,  gastro-colic 

453,  459 

temporo-auricularis      . 

ib. 

452,  459 

teres  major 

864 

453,  503 

.       862 

great 

453,  459 

ib. 

Omphalo-mesenteric  vessels  . 

1023,  1042 

superior 

.       861 

Ophthalmic  nerve 

815 

tibial,  anterior     . 

.       879 

Optic  bulb           .    ■      . 

.        786 

.       881 

770,  810 

tracheal,  recurrent 

.       838 

ib. 

trifacial      .... 

813 

nerves 

ib. 

ib. 

934 

trochlearis 

.       812 

thalami 

772 

829 

Ora  serrata 

930,  934 

tympano-lingual 

B21,  829 

Orbiculare,  os     . 

.       954 

ulnar          .... 

.        865 

Orbital  cavity    . 

926,  938 

vagus          .... 

834 

Organ  of  Corti    . 

.        951 

.        853 

of  Jacobson 

521 

vestibular  .          .          .          .         : 

m,  951 

989,  1050 

Vidian        . 

823 

Organic  life,  nerves  of 

739,  746,  804 

Wrisberg,  of        .          ,          . 

827 

Organs      .... 

5 

Nerve-tubes  of  spinal  cord    . 

761 

392 

Nerve  colline      .... 

235 

ib. 

glands        .... 

579 

solid 

.        394 

740 

394,  395 

sheath         .... 

739 

Os  externum 

992 

Nerve-tissue        .... 

5 

.        954 

Nervous  system  .... 

738 

ib. 

ib. 

uteri           .          .          .          . 

ib. 

of  Birds      . 

894 

Osseous  labyrinth 

947 

Nervi  cardiaci     .          .          .          .          . 

596 

Ossicula  auditus 

.        953 

803 

Ossification,  centres  of 

20 

Neural  arch        .... 

167 

Osteo-dentine      .          .          .          . 

414 

Neuraxis    ...... 

1033 

167 

Neurilemma       ....         7 

41,  803 

Osteogeny            .          .          .          . 

19 

Neurility 

743 

Osteology            .          .          .          . 

7 

Neuroglia            .          .          .          .     5,  7 

41,759 

Ostium  abdominalis     . 

.       923 

Nodule  of  Arantius      .          .          ,          . 

589    i 

ib. 

Nodus  encephali            .          .          .          . 

767 

Otoconites           .          .          .          . 

.       950 

Nomenclature  in  myology     . 

229 

Otoliths 

tb. 

392    j 

Ova  of  Birds       .          .          .          . 

.     1009 

Non-medullated  fibres 

740 

Ovaries 

.       984 

Nostrils 5 

18,  519 

986,  1050 

framework  of      . 

518 

986 

1076 


INDEX. 


Ovaries,  situation 

.       984 

Pelvis,  in  general 

»6. 

Penis 

Oviducts 

.       989 

Peptic  glands      .           .           .           . 

Ovisacs      .... 

.       985 

Perforans  tendon,  sheath  of 

development 

986 

Pericardium       .          .          .          . 

rupture      . 

ib. 

muscle  of  . 

.       985 

Perilymph           .          .          .          . 

Ovula  Nabothi    . 

.        993 

Perimysium        .          .          .          . 

Ovulum     .... 

986,  1004 

Perinseum 

.      1004 

aponeuroses  of    . 

Ovum        ,          .          .          . 

986 

Perineurium        .          .          .          . 
Periople     .          .          .          .          . 

74 

Pacchionian  glands 

.       751 

Perioplic  ring      .          .          .          . 

Pacinian  corpuscles 

.       807 

Periorbita            .          .          .          . 

Palate       .          .          .            396, 

424,  427,  428 

Periosteum          .          .          .          . 

hard           .          .            334. 

424,  427,  428 

Peritoneum 

.       400 

structure  of 

structure    . 

ib 

Perivascular  canals      . 

71 

soft  .          .          .          .  408, 

424,  427,  428 

Perspiration 

411 

Perspiratory  ducts 

.       409 

glands 

structure    . 

.       408 

Pes  anserinus      . 

Palatine  glands  . 

438 

Palatum  molle    . 

.       408 

Petrosal  sinuses 

Palmar  arch 

660 

Peyer's  glands    , 

Palpebrae  .... 

.       942 

Phalanges 

Palpebral  sinuses 

.          .-6. 

Pharyngeal  arches 

Pampiniform  plexus     . 

.       965 

Pancreas    .... 

.       502 

clefts 

development 

.     1049 

Pharynx    .... 

excretory  apparatus      . 

503 

502 

functions    . 

.       503 

.       502 

functions    . 

situation    . 

ib. 

structure    . 

ib. 

relations    . 

Pancreatic  ring  .          . 

ib. 

Panniculus  adiposus     . 

.       899 

Phillip's  muscle 

Papilla  conica     , 

934 

Phrenic  centre    . 

Papilla      .... 

.       393 

Pia  mater .... 

of  foot 

.       912 

cranial 

of  skin 

900,  902 

spinal 

of  tongue     . 

.       402 

Pigment  cells      . 

calyciformes 

402,  923 

Pigmentary  corpuscles  of  horn 

capitata     . 

ib. 

circumvallatse     . 

ib. 

granules     . 

filiformes  . 

ib. 

Pigmentum  nigrum 

fossulate     . 

402 

Pillars  of  diaphragm   . 

fungiformes 

402,,  923 

ib. 

posterior     . 

Parieto-occipital  lobe  . 

.       788 

of  heart     . 

Parielo-temporal  confluents  . 

.       694 

of  inguinal  canal 

lobe  . 

.       788 

of  rumen    . 

Paroophoron 

.       989 

of  soft  palate 

Parotid  duct 

.       435 

434,  439,  440 

Parovarium 

.       988 

of  tongue,  anterior 

Pars  iridica  retinae 

.       933 

Passage  plaits     . 

.        785 

Pineal  gland 

Paihetici  nerves 

.       812 

Pisiform  tubercle 

Pavilion  of  Fallopian  tube     . 

.       989 

Pituitary  fold  of  dura  mater 

Pecklin's  glands 

475 

gland 

Pecquet,  cistern  of 

.       721 

Pectinated  ligament     . 

.        929 

Pectoral  cavity  . 

.        542 

nerves  of    . 

Pedunculi  cerebelli      . 

767,  771 

stem 

cerebri 

767,  770 

Placenta    .... 

."     101 

Pelvis        .... 

.        127 

structure  of 

difference  in  sexee 

.       134 

multiple    . 

INDEX. 


1077 


PAGK 

Placenta,  simple           ....      1030 

Precrural  glands 

Plantar  arcade  or  arch 

• 

640 

Preparation  :— arteries      . 

910 

anterior  tibial      . 

lb. 

structure  of 

911 

axillary 

910 

brachial      . 

866 

reticulum  . 

6 

99,  913 

head,  of      . 

Pleurae 

543 

iliac,  internal 

544 

structure   . 

ib. 

popliteal     . 

Pleuritis,  effusion  of    . 

545 

posterior  tibial     , 

Pleuro-peritoneal  cavity 

1013 

fissure 

ib. 

tibial,  anterior     . 

Plexus,  general  anatomy 

fi 

05,  886 

annularis   . 

929 

articulations 

anterior  auricular 

830 

atlo-axoid  , 

892 

brachial     . 

854,  860 

chondro-costal 

837,  839 

chrondo-sternal    . 

carotid       . 

.       889 

capillary,  of  lungs 

550 

costo-vertebral     . 

887 

coxo-femoral 

cervical,  deep      . 

854 

ib. 

fii-st  interphalangeal 

choroides   . 

792 

humero-radial      . 

cerebellar   . 

779 

coronary  (venous) 

699,  700 

interphalangeal,  first    . 

facial 

826,  830 

.        892 

guttural    . 

887 

hepatic 

892 

pelvis 

893 

lumbo-aortic 

892 

second  interphalangeal 

.       874 

spine,  of     . 

.       715 

mesenteric,  anterior 

892 

.       893 

vertebrae     . 

myenteric  . 

.       477 

.       965 

•  pelvic 

.       893 

bronchi      .... 

•  pharyngeal 

i 

533,  889 

cerebro-spinal  axis,  envelopes  of 

699 

choroid  coat 

renal 

.       892 

solar,  nerve 

ib. 

cranial  nerves      . 

699 

eye 

892 

subzygomatic      . 

'.         i 

$26,  830 

genital  organs,  male     . 

superficial  cervical 

854 

892 

great  sympathetic  nervous  system 

sympathetic 

.        886 

heart          .... 

tracheal     . 

.        890 

498 

hoof 

682 

intestines   .... 

vertebral   . 

.       890 

lachrymal  apparatus    . 

Plicae  palmatae    . 

.      1000 

larynx        .... 

Pneumogastric  lobule  . 

782 

liver           .... 

Podophyllous  tissue     . 

.        913 

lumbo-sacral  plexus      . 

Pons  Tarini 

.        770 

lungs          .... 

Varolii       . 

?67,  769 

lymphatics 

Popliteal  glands 

.        727 

maxillary  gland  . 

Portio  dura 

.        825 

mouth        .... 

832 

muscles      .... 

Porus  opticus     . 

.        928 

abdominal  region,  inferior 

Pouches,  guttural 

.        956 

alveolo-labialis    . 

Poupart's  ligament 

302 

Praeputial  glands 

976 

crural  region 

Praeputium  clitoridis    . 

.        995 

Precervical  nerve 

885 

brachial  region,  anterior 

584, 


1078 

INDEX.. 

PAGE     1 

PAGE 

Preparation,    muscles,    brachial     region, 

Primitive  groove          .          .          •          . 

1013 

posterior 

buccinator  .          .          .          . 

319    I 

1011 

277 

trace           

1010 

cervical  region,  inferior 

253 

Primordial  kidneys       .          .          .          . 

1049 

superior 

244 

Processes  e  cerebello  ad  testes 

771 

costal  region 

296    1 

Promontory  of  ear        .          .          .          . 

952 

crural  region 

848 

Pronucleus,  female       .          .          .          . 

1006 

anterior 

»6. 

male            .          .          .          .          . 

ih. 

353    ! 

Properties  of  nervous  system 

743 

351    1 

Prostate  gland    . 

973 

308   1 

«6. 

external  scapular  region 

310    i 

Protometra 

969 

eye 

939    : 

Protoplasm 

3 

941    ! 

Protuberantia  annularis 

767 

facial           .           .          .          . 

274   i 

Pro  toverte  brae     ....      103 

2,  1038 

femoral  region,  anterior 

348   ! 

Pulmonary  artery 

607 

351    j 

heart           .... 

587 

flexor,  short,  of  forearm 

318 

lobes            .... 

545 

323   1 

547 

gluteal  region      . 

344 

opening  of  heart 

588 

286   1 

pleura         .... 

547 

299 

tissue          .... 

ih. 

cervical 

253 

vesicles       .... 

548 

268 

Puncta  lachrymalia     . 

945 

314 

Punctum  caecum 

934 

274 

Pupil 

932 

leg     .         ...... 

362 

Pupillary  membrane     . 

933 

268 

sphincter 

'     ib. 

284 

Purkinje's  axis-cylinder 

740 

243 

cells            .... 

782 

posterior  brachial  region 

319 

Pylorus A 

t57,  458 

scapular  region,  external 

310 

Pyramidal  eminence  of  os  pedis 

.       116 

314 

Pyramids  of  the  bulb  . 

.       768 

spinal    region    of    back     an 

loins 

260 

Racemose  glands            .          .          .         . 

595,  407 

sublumbar  region 

268 

Rachidian  bulb 

.       767 

.       244 

Radiant  crown  of  Reil 

.       795 

284 

Raphe  of  scrotum 

.       962 

518 

Receptaculum  chyli 

.       721 

447 

Recto-vesicle  fold 

969 

orbital  cavity 

.       938 

Rectum      ..... 

.       484 

osseous  labyrinth 

947 

attachment 

ib. 

palate         .... 

399 

.     1047 

soft   .... 

.       408 

484 

.       494 

ib. 

parotid  gland 

.       434 

Recurrent  sensibility 

744 

pericardium 

597 

Red  nuclei  of  Stilling 

.       782 

pharynx      .... 

.       441 

Reflex  power        .... 

.       746 

.       933 

Reil,  band  of       ...          . 

771 

soft  palate 

.       408 

radiant  crown  of 

.       795 

spinal  cord 

.       754 

Reissner,  membrane  of 

.       950 

spleen         .... 

494 

Remak,  band  of             ... 

740 

455 

Renal  glomerules 

.       572 

.        436 

pelvis          .... 

.       570 

•  sympathetic  nervous  system 

.        885 

Reservoir  of  thymus  gland    . 

.       556 

thoracic  duct 

721 

Respiratory  apparatus 

.       517 

tongue        .... 

trachea       .... 

400 

of  Birds 

557 

.       536 

of  Mammifers 

.       517 

.       568 

nerves 

808 

veins           .... 

685 

Retemirabile      .          .      676,677,679, 

680,  717 

Prepuce 

.       976 

Malpighi    .... 

.       903 

of  clitoris  .... 

.       995 

680 

Preservation  of  muscles 

.       242 

testis           .... 

.       963 

Prickle-cells        .... 

.       903 

Reticular  layer  of  the  derma 

.       900 

Primitive  aortae 

.      1041 

Reticulum            .... 

.       466 

band  of  Remak    . 

.        740 

467 

chorion       .... 

.      1018 

processigerum 

699 

eye-vesicles 

.     1035 

Retina 

933 

fasciculus              o          .          . 

.       231 

Retrossal  process  of  os  pedis 

.       116 

INDEX. 


1079 


PAGE      1 

PAGE 

Rhomboidal  sinus         ....     1033   1 

Sheaths,  lymphatic      . 

.       716 

Ribs           .... 

94 

329 

Right  auricle  of  heart 

. 

589 

.        331 

ventricle    „ 

587 

ocular 

82,  938 

Rima  glottidis     . 

535 

penis,  of     . 

975,  976 

Ring,  inguinal     . 

303 

perforans  tendon,  of      . 

.        331 

pancreatic 

. 

502 

.        739 

589 

tarsal 

371 

Rings  of  trachea 

537 

Shell,  egg,  of      .          .          . 

.      1009 

Rivinian  ducts    , 

438 

ib. 

Rolando,  gelatinous  substance 

of 

759 

Shoulder,  bones  of 

98 

Root  of  lungs 

540,  546 

Sigmoid  gyrus    . 

785 

Rosenmiiller,  organ  of 

989,  1050 

valves 

589,  591 

Rudimentary  sinuses  of  dura 

matei 

.        692 

Simple  follicles  . 

.        474 

Rumen 

464 

glands 

.       395 

structure  of 

466 

Sinus  ampuliaceous 

.     1030 
.       950 

Sacculus  of  ear 

952 

aortici 

608 

Sacral  nerves 

858 

circularis  iridis    . 

.       931 

Sacrum 

39 

901 

Salivary  glands 

.       433 

lactiferus   . 

.       998,  1000 

development  of 

1047 

.        969 

433, 

435,^ 

t37,  438 

renalis 

.        570 

lobules 

433 

rhomboidalis 

776,  1033 

Saphena  veins     . 

710 

,      1042 

Sarcolemma 

231 

Valsalva    . 

.        608 

Sarcous  elements 

f 

231,  236 

Sinuses,  structure  of    . 

.        683 

Scala,  auditive    . 

.       950 

affluents  of 

.        694 

collateral    . 

951 

aortic 

.        608 

ib. 

.       692 

tympanic    . 

i 

)50,  951 

dura  mater,  of    . 

690 

vestibular 

ib. 

.        692 

proper 

.       951 

ib. 

Schindylesis 

.       177 

effluents  of 

694 

Schneiderian  membrane 

.        523 

692 

925 

ib. 

Schwann,  white  substance  oi 

740 

ib. 

Sclerotica 

.       927 

petrosal      . 

ib. 

Sclerotic  cleft     . 

.      1036 

ib. 

Scrotum     . 

.        961 

.       525 

Scutiform  cartilage 

.        281 

693 

Sebaceous  glands 

901 

ib. 

Secondary  dentine 

414 

transverse 

.       692 

Segments  of  Weismann 

.        593 

galactophorous    . 

998 

Segmentation  of  vitellus 

.      1004 

head,  of     . 

524 

.     1006 

.        526 

Semen 

.        966 

functions  of 

ib. 

Semicircular  anastomoses 

.        640 

525 

band 

772 

ib. 

canals 

.       948 

maxillary,  inferior 

ib. 

.        814 

ib. 

589 

mucous  membrane  of 

526 

Semilunar  crest  of  pedal  bon 

.       116 

sphenoidal 

ib. 

fibro-cartilages    . 

.        216 

lymphatic 

.       719 

Seminiferous  tubes 

963 

I)alpebral  . 

.        941 

Sensitive-motor  centre 

745 

renal 

.        570 

Sensorial  functions 

.        746 

.       776,  1033 

Septum  auricularum    . 

587 

535 

. 

789,  791 

subepiglottic 

ib. 

pectiniforme 

.        974 

terminalis 

.      1042 

scroti 

.       961 

Valsalva,  of 

608 

—  ventriculorum 

587 

Skeleton    .... 

8 

Serous  bursse 

.        239 

Skin           .... 

.        898 

membrane 

.       394 

904 

Sertoli,  cells  of 

964 

.        898 

Sesamoid  bones 

.        115 

epidermis  . 

898,  903 

Sharpey's  perforating  fibres 

17 

foetus,  of    . 

.      1037 

Sheaths,  arteries  of 

602,  605 

definitive    .          . 

ib. 

hair  of 

.       907 

functions    . 

.       904 

1080 


INDEX. 


PAGE 

Skin,  structure            .          .          .         900,  903 

Stomach  in  orifices       .          .          , 

PAGB 

.       458 

Small  intestines 

.       471 

situation     . 

456 

Smegma  piaeputii 

.        976 

.       459 

Smell,  apparatus  of 

.        924 

Carnivora 

.       463 

Socia  parotidis    . 

441 

Pig  .          .          .          . 

t6. 

Soemmering,  foramen 

of       '. 

.        947 

Rabbit 

ib. 

Soft  palate 

.408, 

424,  427,  428 

Ruminants 

ib. 

Sole  of  hoof     <r^ 
Solid  organs    ■  4V 

916 

470 

.        394 

Subarachnoid  fluid 

.       752 

f        \ 

394,  395 

Subarytaenoid  sinus 

.       535 

Solitary  glands  . 

474,  479 

Subcorneous  integument 

911 

Somatpleure 

.      1014 

Subcutaneous  region    . 

.       227 

Speculum  Helmontii 

308 

Subepiglottic  sinus      . 

.       535 

Spermatic  cord  . 

9 

62,  965 

Subhepatic  veins 

.       498 

Spermatogonia   . 

964 

Subiculum 

792 

Sphenoidal  lobe  . 

785 

Sublingual  crest 

.       400 

Sphincter  ani      . 

485 

gland 

437,  439 

933 

Sublobular  veins 

498,  500 

vaginse 

995 

Sublumbar  reservoir    . 

721 

Spinal  arachnoid 

751 

Submaxillary  gland     . 

436,  439,  440 

canal 

747 

Subpodophyllous  reticulum  . 

.       913 

754 

Subsphenoidal  confluents 

.       694 

external  conformation  ( 

f 

ib 

Substantia  ferruginea  . 

782 

general  view  of   . 

754 

.       759 

757 

ostoidea      . 

.       414 

756 

Suburethral  notch 

.       975 

structure 

759 

Succus  prostaticus 

.       973 

volume 

756 

Sudoriparous  glands     . 

.       901 

weight 

ib. 

Sulci  horizontalis 

.       779 

749 

bupra-renal  capsules    . 

.       578 

marrow 

739 

development 

.       579 

nerves 

853 

.       578 

constitution 

ib. 

functions    . 

.       579 

854 

.       578 

pia-mater  . 

753 

situation     . 

ib. 

1013 

ib. 

Spine,  the,  in  general 

42 

Supra-sphenoidal  appendage 

.       773 

Splanchnology    . 

392 

Suspensory  ligament  of  fetlock 

206 

Splanchnopleure 

1014 

penis 

974,  976,  983 

Spleen 

503 

.       976 

attachment 

ib. 

uterus 

.       990 

development 

1049 

Sylvius,  fissure  of 

.       785 

direction    . 

503 

Sympathetic  nervous  system 

.       885 

form 

ib. 

.        886 

507 

structure     . 

ib. 

relations    . 

503 

Symphyses 

.       177 

ib. 

Synarthroses 

.        176 

structure  . 

.       504 

.       177 

503 

Synovia    .... 

175,  239 

Splenic  corpuscles 

505 

Synovial  capsules 

»6. 

pulp 

.'6. 

fossae 

172 

Spongy  horn-substance 

761 

.       175 

portion  of  urethra 

971 

membranes 

.       239 

Spontaneous  voluntary  movement. 

745 

sheaths 

ib. 

Stapes       .... 

954 

villi 

lib 

Staphyline  glands 

438 

Systole  of  heart 

.       598 

Stars  of  Verheyen 

573 

Steno's  duct 

435 

Tactile  corpuscles 

.       807 

canal 

521 

Taenia  hippocampi 

.       791 

Stilling,  red  nucleus  of 

782 

semicircularis     . 

772.  792 

Stomach  in  Solipeds     . 

455 

Tail 

.       904 

1047 

Tapetum  lucidum 

930,  931 

456 

fibrosum    . 

t6. 

form 

ib. 

Tarin,  valves  of 

778,  779 

462 

Tarsal  sheath     . 

.       371 

interior 

458 

Tarsi          .... 

942 

ligaments    . 

459 

Tarsus       .... 

144 

mucous  membrane 

460 

Taste,  apparatus  of 

.       922 

muscular  n 

membrane 

459 

Teats         .... 

.       997 

INDEX. 


1081 


PAGE 

PAGE 

Teeth         .... 

411 

Thoracic,  affluents,  termination      .          .       722 

characters  of 

.       412 

: varieties  in 

ib. 

414,  1047 

Thorax      .... 

92,  542 

412 

190,  193 

eruption  of 

.      1048 

.       544 

external  conformation 

.       412 

in  general . 

193 

structure     . 

ib. 

internal  conformation  ^^ 

542 

.       427 

ib. 

Pig  . 

»6. 

Thymic  ducts                          ^^T 

556 

Ruminants 

.       424 

Thymus  gland    . 

555 

Solipeds      . 

416 

1046 

Tegumentary  membranes 

5 

556 

Temporal  fossa   . 

83 

structure    . 

ib. 

lobe            .          .          . 

785,  787 

Thyroid  cartilage 

529 

Tela  choroidea    . 

.        792 

Thyro-hyoid  membrane 

.       530 

Tendinous  centre 

.        308 

Thyroid  gland     . 

553 

592 

554 

.       239 

ib. 

synovial  membranes     . 

ib. 

Tibial  aponeurosis 

362 

Tendo-Achilles    . 

.       368 

Tissues      . 

4 

Tendons    .... 

.       232 

Toe- stay    . 

917 

anterior  extensor  of  metacar 

pus      .       323 

Tongue 

400, 

424,4 

128,  432 

es       .       301 

401 

330 

development  of  . 

.      1046 

extensor  pedis     . 

.       324 

functions  of 

.       407 

s          .       327 

muscles  of. 

.       403 

.       365 

pillars  of  . 

.       401 

hock 

.       367 

ib. 

ib. 

structure  of 

.       402 

.       261 

Tonsils 

401 

large  extensor  of  forearm 

.       319 

.       782 

lateral  extensor  of  phalange 

326 

Torcular  Herophili       . 

692 

320 

Trabeculae  of  spleen     . 

504 

oblique  flexor 

.       327 

testis 

.       963 

perforatus 

328,  369 

Trachea     . 

536 

330,  370 

course 

ib 

prepubic    . 

.       301 

development 

.      1046 

Tentorium  cerebelli     .          . 

.       750 

536 

Tentacula 

904,  906 

relations    . 

ib. 

Tergal  zone 

.      1011 

structure  . 

537 

Terminal  genital  corpuscles  . 

.        975 

Trace,  primitive 

1010 

motor  plate 

235,  806 

Tracheal  glands  , 

539 

vessels 

.       603 

Tractus  longitudinalis. 

790 

Testaceous  membrane  . 

.     1009 

810 

Testes  cerebelli  . 

771 

respirator!  us 

808 

.        984 

Transverse  sinuses 

692 

tubercula  . 

.       771 

Tricuspid  valves 

588 

Testicles    .... 

960,  962 

Trifacial  nerve    . 

813 

attachment  of     . 

960 

Trigeminii 

ib. 

descent  of  . 

.       966 

Trigone 

576 

.       966,  1051 

Trigonum  vesica 

ib 

ectopise  of 

962 

Trisplanchnic  system  . 

885 

.        960 

Trochlea    . 

176 

.        962 

Trochlearis  nerve 

812 

.       966 

Tuber  annulare  . 

769 

structure  of 

962 

cinerium    . 

773 

Testicular  cord   . 

ib. 

Tubercula  nates 

771 

Thalami  optici    . 

'.         767,  772 

ib. 

'i'hebesius,  valve  of 

•        590 

testes 

ib. 

Theca  vertebralis 

.        749 

Tuberculum  Loweri     . 

590 

Thiernesse's  muscle      . 

.        326 

Tubular  glands  . 

395 

Third  ventricle  of  brain 

.        744 

Tubuli  seminiferi 

963 

Thoracic  aorta    . 

.        610 

uriniferi     . 

571 

cavity 

.        542 

Tuft  of  chin 

397 

duct. 

.        721 

Tunic  of  plantar  cushion 

911 

.        724 

Tunica  abdominalis 

99,  300 

.        721 

adventitia  . 

605 

extent 

ib. 

albuginea  of  ovary 

984 

ib. 

of  testicle  . 

962 

1082 


INDEX. 


PAGE 

Tunica,  erythroides      . 

961 

Vaginal  synovial  membrane 

granulosa  .... 

.       987 

Valsalva,  sinus  of         .          .          . 

.       604 

Valves,  Bauhin,  of 

.•6.    1 

Ruyschiana 

.       931 

Eustachian 

.        960 

ilio-caecal   . 

communis  . 

»6. 

(6. 

lymphatic 

t6. 

vasculosa  testis   . 

.        964 

mitral 

Tiirc's  fasciculus 

758 

Renault,  of 

Tympanal  circle 

.        952 

semilunar  . 

Tympanic  scala  .          .          .          . 

949 

sigmoid 

Tympanum         .          .          .          . 

952 

Tyson's  glands    .          .          .          . 

.        901 

Thebesius,  of 

Ultimate  follicles 

.        433 

veins,  of     . 

Umbilical  cord    .          .          .          . 

1017,  1025 

Vieussens,  of 

arteries      .          .          .          . 

.      1025 

vulvo-vaginal      . 

region         .          .          .          . 

451 
.      1025 

Valvulae  conniventes    . 
Varolii,  pons 

vesicle        .          .          .   1014 

,    1016,  1023 

Vasa  afferentia   . 

Unipolar  nerve-cells     . 

.        740 

etferentia   . 

Uniting  tube  of  kidney 

.        572 

Unitive  fibres  of  heart 

594,  595 

recta 

Unstriped  muscular  fibres      . 

394 

Urachus.    .... 

1021,  1050 

of  veins 

Ureters      .          .          .          • 

.        574 

ib. 

Vascular  blood  glands 

ib. 

Vas  deferens 

structure    . 

ib. 

structure  of 

.       575 

Vegetative  life,  nerves  of 

.       574 

Veins  : — definition 

Urethra     .... 

.       578 

disposition   . 

970 

course 

ib. 

form   . 

interior 

ib. 

ib. 

injection  of  . 

structure    . 

.       971 

female,  of  , 

996 

abdominal,  subcutaneo 

us 

Urethral  ridge    . 

970 

alveolar      . 

.       975 

Urinary  apparatus 

.       568 

Uro-genital  sinus 

.     1051 

vena  cava   . 

Uterine  glands    . 

.       993 

auricular,  anterior 

tubes          . 

.       989 

.       990 

structure    . 

.       989 

basilic 

Uterus       .... 

990 

basium  vertebrarium 

attachment 

ib. 

.       993 

form. 

.       990 

buccal 

functions    . 

.       993 

caecal 

interior      . 

.       992 

cardiac 

masculine  . 

.       969 

.        990 

structure   . 

.       992 

Utricular  glands 

993 

central  of  foot      . 

Utriculus  of  ear. 

.       949 

of  retina     . 

Uvula  of  cerebellum    . 

.       969 

.       782 

colic. 

Vagina      .... 

.       993 

collateral,  of  cannon,  e 

xternal 

.       995 

internal  conformation  . 

.       994 

coronary    . 

situation    . 

993 

great 

structure   . 

994 

small 

Vaginal  bulb 
sheath 

.       996 

of  foot 

.       960 

INDEX. 

1083 

PAGE      1 

PAGE 

Veins,  dental,  inferior           .          .          .690 

Veins,  portal      .         .          .          .          . 

705 

688 

posterior  cardinal 

1044 

703 

701 

digital 

dorsal 

90,  698 

vena  cava    ...       70 

3,  1044 

686 

prepubic 

709 

688 

690 

ductus  venosus    . 

1044 

pulmonary           .          .          .          . 

685 

707 

pyloric 

707 

facial          .          .          . 

688 

radial,  anterior   ...         6 

96,  697 

femoral 

709 

posterior     .          .          .          . 

967 

ib. 

697 

Galeni 

694 

707 

gastric,  anterior 

707 

saphena,  external 

710 

ib. 

internal 

ib. 

gastro-epiploic,  left 

706 

solar           .... 

699 

right 

707 

spermatic  .... 

707 

706 

splenic        .          .          .          .          . 

706 

right 

707 

spur.          „          .          „          .          . 

696 

gluteal 

708 

subcutaneous,  abdominal 

711 

709 

internal      .          .          .          . 

697 

haemorrhoidal      . 

706 

696 

humeral     . 

696 

sublingual. 

689 

.        709 

705 

common      . 

.       708 

submaxillary 

688 

709 

696 

ib. 

690 

ilaco-femoral 

ib. 

superficial  temporal      .          .         6 

87,  689 

iliaco-muscular  . 

ib. 

686 

.       706 

690 

.        689 

superficial            .          .         6 

87,  689 

interlobular  of  liver 

705 

708 

686 

Thebesii     .... 

685 

maxillary  . 

.        687 

thoracic,  external 

686 

thoracic      . 

686 

internal      . 

ib. 

709 

thyroid       .... 

689 

.       697 

710 

intra-lobular,  of  liver 

.       495 

posterior    . 

ib. 

intra-osseous,  of  foot 

702 

697 

.        687 

1044 

588,  689 

.       698 

709 

708 

690 

Vena  azygos       .... 

.       686 

lumbar 

.       708 

Galeni         . 

.        694 

mammary,  internal 

.        686 

portae 

705 

maxillary,  internal 

387,  690 

.      1042 

maxillo-muscular 

.        687 

ib. 

.       694 

vertebral   ....        6 

id,  1044 

697 

cava,  anterior 

686 

.       706 

posterior     .          .          .       7( 

)3,  1044 

ib. 

:    Velum  interpositum     .          .          .         ' 

f'84,  792 

meseraic,  anterior 

ib. 

pendulum  palati 

.       408 

metacarpal,  external 

ib. 

vasculosum 

792 

. 

696,  698 

Velvety  tissue  of  foot  . 

912 

internal      . 

ib. 

Vena  azygos,  great 

.        686 

metatarsal 

.       710 

small 

ib. 

.       711 

ib. 

710 

posterior     . 

.        703 

ib. 

!    Galeni        .... 

394,  789 

^^ nasal 

.       688 

portae          .... 

705 

709 

Venae  comites     .... 

.        684 

occipital     . 

palatine 

pancreatic 

peripheral 

phrenic 

plate 

ib. 

.       931 

.      1042 

Ventricles  of  brain       .          .771,774, 

?76,  790 

689 

cerebellar   . 

.        776 

,        707 
.        699 

fourth 

790 

774 

703 

lateral 

789,  790 

689,  697 

middle 

774 

699 

.       776 

. 

.       709 

i third 

.       774 

1084 


INDEX. 


PAGE 

PAGB 

Ventricles  of  thalami  optic             .          .       774 

Vitreous  humour         .          .          . 

.       937 

of  heart     . 

587,  590 

Viscera 

392 

535 

Visceral 'pleura  .          .          .          . 

543 

^'entricular  arachnoid 

790 

Vision,  apparatus  of    . 

.        925 

584 

Vocal  cords         .          .          .          . 

.       530 

Vermiform  appendix    . 

492 

superior      . 

.       531 

processes  of  cerebellum 

779 

Voluntary  movements 

746 

ib. 

Vulva 

995 

posterior 

ih. 

cavity  of    . 

.•6. 

Vermis  of  cerebellum  . 

ib. 

external  opening  of      . 

«6. 

Vertebrae  . 

24 

structure   .          .          .          . 

.       996 

ib. 

Vulva  of  brain  . 

.       803 

proper  to    . 

26 

Vulva,  labia       . 

.       995 

development 

2 

6,  1038 

26 

Wall  of  hoof       . 

.       915 

Vertebral  column 

24 

angle  of      . 

.       917 

development  of 

1038 

structure  of 

•6. 

167 

Weismann,  segments  of 

593 

1032 

Wharton's  duct . 

.       437 

Vertebro-costal  channels 

512 

gelatine  of 

.      1025 

Veru  montanum 

969 

White  line  of  hoof       . 

.        920 

Vesicle,  serous    . 

1016 

substance  of  Schwann  . 

740 

ib. 

.       759 

Vesicles,  Graafian 

i 

m,  986 

longitudinal  fibres  of  brain 

.       776 

548 

ib. 

Vesicula  seminalis  tertia 

969 

Wilson's  muscle 

971,  983 

Vesiculae  seminales 

968 

Winepress  of  Herophilus 

.       692 

Vestibular  scala 

950 

Winslow,  foramen  of  . 

.       453 

Vestibule  of  ear 

949 

Wirsung,  duct  of 

.        503 

Vibratile  cilia    . 

393 

Wolffian  bodies  . 

1049,  1050 

Vibrissa   . 

527 

Wrisberg,  nerve  of 

.       827 

Vicq-d'Azyr,  caecum  of 

778 

centrum  ovale  of 

.       795 

Xiphoid  appendage  of  sternum 

93 

Vidian  canal 

829 

nerve 

Villi,  intestinal . 

»6. 
823 
473 

Yolk  of  egg 
Yolk  nucleus      . 

.     1009 
.     1006 

Villosities 

393 

Villo-papillae  of  foot    . 

912 

Zona  pellucida    ... 

.      1005 

Villous  loops  of  foot    . 

ib. 

Zonula  ciliaris    . 

930,  931 

Vitellus     . 

986,  1003 

of  Zinn 

930,  934 

Vitreous  body    . 

.       937 

Zoiisperma 

.       966 

(4) 


APR  82 


N.  MANCHESTER, 
INDIANA  46962 


